Energy efficient heat pump with active charge management

Abstract

An energy efficient heat pump for a heating, ventilation, and air conditioning (HVAC) system, including a working fluid circuit that may circulate a working fluid therethrough, where the working fluid circuit includes a first heat exchanger and a second heat exchanger. The heat pump also includes a first expansion device, a second expansion device, and a liquid conduit portion extending between the first heat exchanger and the second heat exchanger, where the first expansion device and the second expansion device are disposed along the liquid conduit portion. The heat pump further includes a receiver disposed along the liquid conduit portion and a controller communicatively coupled to the first expansion device and the second expansion device, where the controller may adjust the first expansion device, the second expansion device, or both to adjust the amount of the working fluid retained within the receiver.

Description

BACKGROUND

[0001] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

[0002] A heating, ventilation, and / or air conditioning (HVAC) system may be used to thermally regulate an environment, such as a space within a building, home, or other structure. HVAC systems generally include a vapor compression system having heat exchangers, such as a condenser and an evaporator, which transfer thermal energy between the HVAC system and the environment. Typically, a compressor is fluidly coupled to a working fluid circuit of the vapor compression system and is configured to circulate a working fluid (e.g., refrigerant) between the heat exchangers. In this way, the compressor facilitates heat exchange between the working fluid, the heat exchangers, and other fluids directed across and / or through the heat exchangers. In some cases, the HVAC system may be a heat pump configured to enable reversal of working fluid flow through the working fluid circuit. As such, the heat pump enables the working fluid circuit to operate in a cooling mode and in a heating mode Accordingly, the HVAC system may operate in multiple operating modes (e.g., cooling mode, heating mode) to provide both heating and cooling to the building with one working fluid circuit. Unfortunately, a desired amount of working fluid circulated in the working fluid circuit (e.g., charge) is usually different in the cooling mode and heating mode, thereby resulting in inefficiencies in one mode or the other for traditional systems.SUMMARY

[0003] A summary of certain embodiments disclosed herein is set forth below. It should be noted that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.

[0004] In an embodiment, an energy efficient heat pump for a heating, ventilation, and air conditioning (HVAC) system, includes a working fluid circuit that may circulate a working fluid therethrough, where the working fluid circuit includes a first heat exchanger that may transfer heat between the working fluid and a supply air flow, and a second heat exchanger that may transfer heat between the working fluid and an ambient air flow. The heat pump further including a first expansion device, a second expansion device and a liquid conduit portion of the working fluid circuit extending between the first heat exchanger and the second heat exchanger, where the first expansion device and the second expansion device are disposed along the liquid conduit portion. The heat pump also including a receiver disposed along the liquid conduit portion of the working fluid circuit between the first expansion device and the second expansion device, where the receiver includes a vessel to retain an amount of the working fluid therein. The heat pump also including a controller communicatively coupled to the first expansion device and the second expansion device, where the controller may adjust the first expansion device, the second expansion device, or both to adjust the amount of the working fluid retained within the vessel of the receiver.

[0005] In another embodiment, an energy efficient heat pump for a heating, ventilation, and air conditioning (HVAC) system, includes a working fluid circuit including a liquid conduit portion that may direct a working fluid between a first heat exchanger of the working fluid circuit and a second heat exchanger of the working fluid circuit. The heat pump also including a receiver disposed along the liquid conduit portion, where the receiver includes a vessel, a first dip tube fluidly coupled to the liquid conduit portion and extending into the vessel, and a second dip tube fluidly coupled to the liquid conduit portion and extending into the vessel, where the first dip tube and the second dip tube may each direct the working fluid from the liquid conduit portion and into the vessel and to direct the working fluid from the vessel to the liquid conduit portion. The heat pump also including a first expansion device disposed along the liquid conduit portion between the first heat exchanger and the receiver, a second expansion device disposed along the liquid conduit portion between the second heat exchanger and the receiver, and a controller communicatively coupled to the first expansion device and the second expansion device. The controller may adjust the first expansion device and the second expansion device based on an operating mode of the energy efficient heat pump and based on at least one operating parameter of the working fluid, where the controller may regulate an amount of working fluid retained within the vessel of the receiver.

[0006] In a further embodiment, an energy efficient heat pump includes a working fluid circuit that may circulate a working fluid therethrough, a first heat exchanger disposed along the working fluid circuit and operable to transfer heat between the working fluid and a supply air flow in a heating mode and in a cooling mode of the energy efficient heat pump. The heat pump also including a second heat exchanger disposed along the working fluid circuit and operable to transfer heat between the working fluid and an ambient air flow in the heating mode and the cooling mode and a liquid conduit portion of the working fluid circuit extending between the first heat exchanger and the second heat exchanger. The heat pump also including a receiver disposed along the liquid conduit portion, where the receiver includes a vessel, a first dip tube fluidly coupled to the liquid conduit portion and extending into the vessel, and a second dip tube fluidly coupled to the liquid conduit portion and extending into the vessel a first electronic expansion valve disposed along the liquid conduit portion between the first heat exchanger and the first dip tube. The heat pump further including a second electronic expansion valve disposed along the liquid conduit portion between the second heat exchanger and the second dip tube and a controller communicatively coupled to the first electronic expansion valve and the second electronic expansion valve. The controller may adjust the first electronic expansion valve and the second electronic expansion valve based on data indicative of an amount of subcooling of the working fluid and data indicative of an amount of superheat of the working fluid to adjust an amount of the working fluid retained within the vessel in the heating mode and in the cooling mode.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which:

[0008] FIG. 1 is a perspective view of an embodiment of a building incorporating a heating, ventilation, and / or air conditioning (HVAC) system in a commercial setting, in accordance with an aspect of the present disclosure;

[0009] FIG. 2 is a perspective view of an embodiment of a packaged HVAC unit, in accordance with an aspect of the present disclosure;

[0010] FIG. 3 is a perspective view of an embodiment of a split, residential HVAC system, in accordance with an aspect of the present disclosure;

[0011] FIG. 4 is a schematic diagram of an embodiment of a vapor compression system used in an HVAC system, in accordance with an aspect of the present disclosure;

[0012] FIG. 5 is a schematic diagram of an embodiment of a portion of an HVAC system including a heat pump system having a receiver and a controller, in accordance with an aspect of the present disclosure;

[0013] FIG. 6 is a schematic diagram of an embodiment of a portion of an HVAC system including a heat pump system having a receiver and a controller, in accordance with an aspect of the present disclosure;

[0014] FIG. 7 is a schematic diagram of an embodiment of a portion of an HVAC system including a heat pump system having a receiver and a controller, in accordance with an aspect of the present disclosure;

[0015] FIG. 8 is a schematic diagram of an embodiment of a portion of an HVAC system including a heat pump system having a receiver and a controller, in accordance with an aspect of the present disclosure;

[0016] FIG. 9 is a flow chart of an embodiment of a method for controlling operation of a heat pump system of an HVAC system, in accordance with an aspect of the present disclosure;

[0017] FIG. 10 is a flow chart of an embodiment of a heating control sequence of a method for controlling operation of a heat pump system of an HVAC system, in accordance with an aspect of the present disclosure; and

[0018] FIG. 11 is a flow chart of an embodiment of a cooling control sequence of a method for controlling operation of a heat pump system of an HVAC system, in accordance with an aspect of the present disclosure.DETAILED DESCRIPTION

[0019] One or more specific embodiments of the present disclosure will be described below. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers’ specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0020] When introducing elements of various embodiments of the present disclosure, the articles “a,”“an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0021] As used herein, the terms “approximately,”“generally,” and “substantially,” and so forth, are intended to convey that the property value being described may be within a relatively small range of the property value, as those of ordinary skill would understand. For example, when a property value is described as being “approximately” equal to (or, for example, “substantially similar” to) a given value, this is intended to mean that the property value may be within + / - 5%, within + / - 4%, within + / - 3%, within + / - 2%, within + / - 1%, or even closer, of the given value. Similarly, when a given feature is described as being “substantially parallel” to another feature, “generally perpendicular” to another feature, and so forth, this is intended to mean that the given feature is within + / - 5%, within + / - 4%, within + / - 3%, within + / - 2%, within + / - 1%, or even closer, to having the described nature, such as being parallel to another feature, being perpendicular to another feature, and so forth. Further, it should be understood that mathematical terms, such as “planar,”“slope,”“perpendicular,”“parallel,” and so forth are intended to encompass features of surfaces or elements as understood to one of ordinary skill in the relevant art, and should not be rigidly interpreted as might be understood in the mathematical arts. For example, a “planar” surface is intended to encompass a surface that is machined, molded, or otherwise formed to be substantially flat or smooth (within related tolerances) using techniques and tools available to one of ordinary skill in the art. Similarly, a surface having a “slope” is intended to encompass a surface that is machined, molded, or otherwise formed to be oriented at an angle (e.g., incline) with respect to a point of reference using techniques and tools available to one of ordinary skill in the art.

[0022] As briefly discussed above, a heating, ventilation, and / or air conditioning (HVAC) system may be used to thermally regulate a space within a building, home, or other suitable structure. For example, the HVAC system may include a vapor compression system that transfers thermal energy between a working fluid, such as a refrigerant, and a fluid to be conditioned, such as air. The vapor compression system includes heat exchangers, such as a condenser and an evaporator, which are fluidly coupled to one another via one or more conduits of a working fluid loop or circuit. A compressor may be used to circulate the working fluid through the conduits and other components of the working fluid circuit (e.g., an expansion device) and, thus, enable the transfer of thermal energy between components of the working fluid circuit (e.g., between the condenser and the evaporator) and one or more thermal loads (e.g., an environmental air flow, a supply air flow). Additionally or alternatively, the HVAC system may include a heat pump (e.g., a heat pump system) having a first heat exchanger (e.g., a heating and / or cooling coil, an indoor coil, the evaporator) fluidly coupled to the space to be conditioned, a second heat exchanger (e.g., a heating and / or cooling coil, an outdoor coil, the condenser) positioned in or otherwise fluidly coupled to an ambient environment (e.g., the atmosphere), and a pump (e.g., compressor) configured to circulate the working fluid (e.g., refrigerant) between the first and second heat exchangers to enable heat transfer between the space to be conditioned and the ambient environment, for example.

[0023] The heat pump may be operable to provide both cooling and heating to the space to be conditioned (e.g., a room, zone, or other region within a building) by adjusting a flow of the working fluid through the working fluid circuit. Thus, the heat pump may not include a dedicated heating system, such as a furnace or burner configured to combust a fuel, to enable operation of the HVAC system in the heating mode. As a result, the heat pump is configured to operate with reduced greenhouse gas emissions. For example, during operation of the heat pump in a cooling mode, the compressor may direct working fluid through the working fluid circuit and the first and second heat exchangers in a first flow direction. While receiving working fluid in the first flow direction, the first heat exchanger, which may be fluidly coupled to the space to be conditioned, may operate as an evaporator and, thus, enable working fluid flowing through the first heat exchanger to absorb thermal energy from an air flow directed to the space. Further, the second heat exchanger, which may be positioned in the ambient environment surrounding the heat pump, may operate as a condenser to reject the heat absorbed by the working fluid flowing from the first heat exchanger (e.g., to an ambient air flow directed across the second heat exchanger). In this way, the heat pump may facilitate cooling of the space or other thermal load serviced by (e.g., in thermal communication with) the first heat exchanger.

[0024] Conversely, during operation in a heating mode, a reversing valve (e.g., a switch-over valve) enables the compressor to direct working fluid through the working fluid circuit and the first and second heat exchangers in a second flow direction, opposite the first flow direction. While receiving working fluid in the second flow direction, the first heat exchanger may operate as a condenser instead of an evaporator, and the second heat exchanger may operate as an evaporator instead of a condenser. As such, the first heat exchanger may receive (e.g., from the second heat exchanger) a flow of heated working fluid to reject heat to a thermal load serviced by the first heat exchanger (e.g., an air flow directed to the space) and, thus, facilitate heating of the thermal load. In this way, the heat pump may facilitate either heating or cooling of the thermal load based on a selected operating mode of the heat pump (e.g., based on a flow direction of working fluid along the working fluid circuit).

[0025] Unfortunately, HVAC systems may be susceptible to operational inefficiencies in certain conditions or circumstances. As an example, an amount of working fluid circulated through the working fluid circuit may be ill-suited and / or inefficient for certain HVAC system and / or heat pump operations. In other words, a desired amount of working fluid circulated through the heat pump (e.g., charge) may be different in the cooling mode and in the heating mode, thereby resulting in inefficiencies in one mode or the other for heat pumps configured to operate with a fixed amount of working fluid directed through the working fluid circuit. In many heat pump configurations, there are differences in internal volumes between the indoor heat exchanger and outdoor heat exchanger (e.g., first heat exchanger and second heat exchanger). For example, the indoor heat exchanger (e.g., first heat exchanger) may have an internal volume that is less than the internal volume of the outdoor heat exchanger. As such, when a reversible heat pump changes modes (e.g., from a heating mode to a cooling mode or vice versa), and the heat exchangers switch functions (e.g., evaporator to condenser or vice versa) the desirable charge in the heat pump may change. In most heat pumps, the total amount of working fluid remains constant, as it would be undesirable and / or inefficient to add or reduce the working fluid in a system. As such, methods of controlling the amount of working fluid (e.g., charge) in the heat pump are desirable.

[0026] Conventional approaches to address such shortcomings with heat pumps are typically expensive and complicated. Conventional approaches may also be associated with increased energy consumption and generation of greenhouse gas emissions. For example, a compensator may be included in the heat pump and may be configured to enable control of an amount of working fluid circulating in the working fluid circuit. For example, the compensator may be configured to retain a portion of working fluid therein during the heating mode of the heat pump, such that the portion of retained working fluid does not circulate through the working fluid circuit, to improve operation of the heat pump in the heating mode. However, efficiency improvements provided by compensators may be limited.

[0027] Accordingly, embodiments of the present disclosure relate to a heat pump that is configured to enable more efficient operation and enable a reduction in the generation of greenhouse gas emissions. For example, present embodiments include heat pumps configured to regulate a charge or amount of working fluid circulated through the working fluid circuit to enable more efficient operation of the heat pump in both a heating mode and a cooling mode. In this way, the present techniques enable a reduction in energy consumption and a reduction in greenhouse gas emissions. As discussed in detail below, the heat pump (e.g., heat pump system, a reverse-cycle heat pump system, an air-source heat pump system, reverse cycle air conditioner) may include a receiver positioned between the first heat exchanger and the second heat exchanger that is configured to receive and store an amount of working fluid from the working fluid circuit based on an operating mode of the heat pump, a parameter of the heat pump, or both. In other words, the receiver may store the amount of working fluid, such that the amount of working fluid is not circulated through the working fluid circuit. For example, in a heating mode, when a lower charge of working fluid within the working fluid circuit is desired, the receiver may receive and store an increased amount of working fluid, thereby decreasing the total charge of working fluid in the working fluid circuit. Further, in a cooling mode, when a higher charge of working fluid within the working fluid circuit is desired, the receiver may receive and store a decreased amount of working fluid, thereby increasing the total charge working fluid in the working fluid circuit. In this way, the heat pump may operate with increased efficiency in both the heating mode and the cooling mode.

[0028] The amount of working fluid directed into and stored within the receiver may be adjusted via control of other components of the heat pump. Accordingly, embodiments of the present disclosure also include an improved control system configured to regulate operation of the heat pump and the components of the heat pump. In accordance with present techniques, the control system may regulate operation of expansion devices (e.g., expansion valves, electronic expansion valves, electronic expansion devices) of the heat pump to enable more efficient operation (e.g., reduced energy consumption). For example, the control system may control operation of the expansion devices of the heat pump based on an operating mode of the heat pump, based on operating conditions or parameters of the heat pump, and / or additional variables. For example, the control system may be configured to operate one or more expansion devices to obtain a desired amount of superheating or subcooling of the working fluid in the heat pump. Based on the control of the one or more expansion devices, an amount or volume of working fluid retained within the receiver may be adjusted (e.g., working fluid added to receiver, working fluid removed from receiver). In this way, present embodiments enable more efficient operation of the heat pump in both heating and cooling modes by regulating the amount of working fluid charge (e.g., active charge) in the working fluid circuit. Indeed, the present embodiments provide energy efficient heat pumps configured to operate and satisfy heating demands in cold and warm climate conditions with reduced energy consumption, thereby enabling a reduction of greenhouse gas emissions.

[0029] Turning now to the drawings, FIG. 1 illustrates an embodiment of a heating, ventilation, and / or air conditioning (HVAC) system for environmental management that employs one or more HVAC units in accordance with the present disclosure. As used herein, an HVAC system includes any number of components configured to enable regulation of parameters related to climate characteristics, such as temperature, humidity, air flow, pressure, air quality, and so forth. For example, an “HVAC system” as used herein is defined as conventionally understood and as further described herein. Components or parts of an “HVAC system” may include, but are not limited to, all, some of, or individual parts such as a heat exchanger, a heater, an air flow control device, such as a fan, a sensor configured to detect a climate characteristic or operating parameter, a filter, a control device configured to regulate operation of an HVAC system component, a component configured to enable regulation of climate characteristics, or a combination thereof. An “HVAC system” is a system configured to provide such functions as heating, cooling, ventilation, dehumidification, pressurization, refrigeration, filtration, or any combination thereof. The embodiments described herein may be utilized in a variety of applications to control climate characteristics, such as residential, commercial, industrial, transportation, or other applications where climate control is desired.

[0030] In the illustrated embodiment, a building 10 is air conditioned by a system that includes an HVAC unit 12 with a reheat system in accordance with present embodiments. The building 10 may be a commercial structure or a residential structure. As shown, the HVAC unit 12 is disposed on the roof of the building 10; however, the HVAC unit 12 may be located in other equipment rooms or areas adjacent the building 10. The HVAC unit 12 may be a single package unit containing other equipment, such as a blower, integrated air handler, and / or auxiliary heating unit. In other embodiments, the HVAC unit 12 may be part of a split HVAC system, such as the system shown in FIG. 3, which includes an outdoor HVAC unit 58 and an indoor HVAC unit 56.

[0031] The HVAC unit 12 is an air cooled device that implements a refrigeration cycle to provide conditioned air to the building 10. Specifically, the HVAC unit 12 may include one or more heat exchangers across which an air flow is passed to condition the air flow before the air flow is supplied to the building. In the illustrated embodiment, the HVAC unit 12 is a rooftop unit (RTU) that conditions a supply air stream, such as environmental air and / or a return air flow from the building 10. After the HVAC unit 12 conditions the air, the air is supplied to the building 10 via ductwork 14 extending throughout the building 10 from the HVAC unit 12. For example, the ductwork 14 may extend to various individual floors or other sections of the building 10. In certain embodiments, the HVAC unit 12 may be a heat pump that provides both heating and cooling to the building with one working fluid circuit configured to operate in different modes. In other embodiments, the HVAC unit 12 may include one or more working fluid circuits for cooling an air stream and a furnace for heating the air stream.

[0032] A control device 16, one type of which may be a thermostat, may be used to designate the temperature of the conditioned air. The control device 16 also may be used to control the flow of air through the ductwork 14. For example, the control device 16 may be used to regulate operation of one or more components of the HVAC unit 12 or other components, such as dampers and fans, within the building 10 that may control flow of air through and / or from the ductwork 14. In some embodiments, other devices may be included in the system, such as pressure and / or temperature transducers or switches that sense the temperatures and pressures of the supply air, return air, and so forth. Moreover, the control device 16 may include computer systems that are integrated with or separate from other building control or monitoring systems, and even systems that are remote from the building 10.

[0033] FIG. 2 is a perspective view of an embodiment of the HVAC unit 12. In the illustrated embodiment, the HVAC unit 12 is a single package unit that may include one or more independent vapor compression circuits and components that are tested, charged, wired, piped, and ready for installation. The HVAC unit 12 may provide a variety of heating and / or cooling functions, such as cooling only, heating only, cooling with electric heat, cooling with dehumidification, cooling with gas heat, or cooling with a heat pump. As described above, the HVAC unit 12 may directly cool and / or heat an air stream provided to the building 10 to condition a space in the building 10.

[0034] As shown in the illustrated embodiment of FIG. 2, a cabinet 24 encloses the HVAC unit 12 and provides structural support and protection to the internal components from environmental and other contaminants. In some embodiments, the cabinet 24 may be constructed of galvanized steel and insulated with aluminum foil faced insulation. Rails 26 may be joined to the bottom perimeter of the cabinet 24 and provide a foundation for the HVAC unit 12. In certain embodiments, the rails 26 may provide access for a forklift and / or overhead rigging to facilitate installation and / or removal of the HVAC unit 12. In some embodiments, the rails 26 may fit into “curbs” on the roof to enable the HVAC unit 12 to provide air to the ductwork 14 from the bottom of the HVAC unit 12 while blocking elements such as rain from leaking into the building 10.

[0035] The HVAC unit 12 includes heat exchangers 28 and 30 in fluid communication with one or more vapor compression circuits. Tubes within the heat exchangers 28 and 30 may circulate a working fluid (e.g., a refrigerant), such as R-410A, R-407, R-134a, R-1234ze, R1233zd, R-32, hydrofluoro olefin (HFO), “natural” refrigerants like ammonia (NH3), R-717, carbon dioxide (CO2), R-744, or hydrocarbon based refrigerants, water vapor, or any other suitable working fluid through the heat exchangers 28 and 30. The tubes may be of various types, such as multichannel tubes, conventional copper or aluminum tubing, and so forth. Together, the heat exchangers 28 and 30 may implement a thermal cycle in which the working fluid undergoes phase changes and / or temperature changes as it flows through the heat exchangers 28 and 30 to produce heated and / or cooled air. For example, the heat exchanger 28 may function as a condenser where heat is released from the working fluid to ambient air, and the heat exchanger 30 may function as an evaporator where the working fluid absorbs heat to cool an air stream. In other embodiments, the HVAC unit 12 may operate in a heat pump mode where the roles of the heat exchangers 28 and 30 may be reversed. That is, the heat exchanger 28 may function as an evaporator and the heat exchanger 30 may function as a condenser. In further embodiments, the HVAC unit 12 may include a furnace for heating the air stream that is supplied to the building 10. While the illustrated embodiment of FIG. 2 shows the HVAC unit 12 having two of the heat exchangers 28 and 30, in other embodiments, the HVAC unit 12 may include one heat exchanger or more than two heat exchangers.

[0036] The heat exchanger 30 is located within a compartment 31 that separates the heat exchanger 30 from the heat exchanger 28. Fans 32 draw air from the environment through the heat exchanger 28. Air may be heated and / or cooled as the air flows through the heat exchanger 28 before being released back to the environment surrounding the HVAC unit 12. A blower assembly 34, powered by a motor 36, draws air through the heat exchanger 30 to heat or cool the air. The heated or cooled air may be directed to the building 10 by the ductwork 14, which may be connected to the HVAC unit 12. Before flowing through the heat exchanger 30, the conditioned air flows through one or more filters 38 that may remove particulates and contaminants from the air. In certain embodiments, the filters 38 may be disposed on the air intake side of the heat exchanger 30 to prevent contaminants from contacting the heat exchanger 30.

[0037] The HVAC unit 12 also may include other equipment for implementing the thermal cycle. Compressors 42 increase the pressure and temperature of the working fluid before the working fluid enters the heat exchanger 28. The compressors 42 may be any suitable type of compressors, such as scroll compressors, rotary compressors, screw compressors, or reciprocating compressors. In some embodiments, the compressors 42 may include a pair of hermetic direct drive compressors arranged in a dual stage configuration 44. However, in other embodiments, any number of the compressors 42 may be provided to achieve various stages of heating and / or cooling. As may be appreciated, additional equipment and devices may be included in the HVAC unit 12, such as a solid-core filter drier, a drain pan, a disconnect switch, an economizer, pressure switches, phase monitors, and humidity sensors, among other things.

[0038] The HVAC unit 12 may receive power through a terminal block 46. For example, a high voltage power source may be connected to the terminal block 46 to power the equipment. The operation of the HVAC unit 12 may be governed or regulated by a control board 48. The control board 48 may include control circuitry connected to a thermostat, sensors, and alarms. One or more of these components may be referred to herein separately or collectively as the control device 16. The control circuitry may be configured to control operation of the equipment, provide alarms, and monitor safety switches. Wiring 49 may connect the control board 48 and the terminal block 46 to the equipment of the HVAC unit 12.

[0039] FIG. 3 illustrates a residential heating and cooling system 50, also in accordance with present techniques. The residential heating and cooling system 50 may provide heated and cooled air to a residential structure, as well as provide outside air for ventilation and provide improved indoor air quality (IAQ) through devices such as ultraviolet lights and air filters. In the illustrated embodiment, the residential heating and cooling system 50 is a split HVAC system. In general, a residence 52 conditioned by a split HVAC system may include working fluid conduits 54 that operatively couple the indoor unit 56 to the outdoor unit 58. The indoor unit56 may be positioned in a utility room, an attic, a basement, and so forth. The outdoor unit 58 is typically situated adjacent to a side of residence 52 and is covered by a shroud to protect the system components and to prevent leaves and other debris or contaminants from entering the unit. The working fluid conduits 54 transfer working fluid between the indoor unit 56 and the outdoor unit 58, typically transferring primarily liquid working fluid in one direction and primarily vaporized working fluid in an opposite direction.

[0040] When the system shown in FIG. 3 is operating as an air conditioner, a heat exchanger 60 in the outdoor unit 58 serves as a condenser for re-condensing vaporized working fluid flowing from the indoor unit 56 to the outdoor unit 58 via one of the working fluid conduits 54. In these applications, a heat exchanger 62 of the indoor unit functions as an evaporator. Specifically, the heat exchanger 62 receives liquid working fluid, which may be expanded by an expansion device, and evaporates the working fluid before returning it to the outdoor unit 58.

[0041] The outdoor unit 58 draws environmental air through the heat exchanger 60 using a fan 64 and expels the air above the outdoor unit 58. When operating as an air conditioner, the air is heated by the heat exchanger 60 within the outdoor unit 58 and exits the unit at a temperature higher than it entered. The indoor unit 56 includes a blower or fan 66 that directs air through or across the indoor heat exchanger 62, where the air is cooled when the system is operating in air conditioning mode. Thereafter, the air is passed through ductwork 68 that directs the air to the residence 52. The overall system operates to maintain a desired temperature as set by a system controller. When the temperature sensed inside the residence 52 is higher than the set point on the thermostat, or the set point plus a small amount, the residential heating and cooling system 50 may become operative to refrigerate additional air for circulation through the residence 52. When the temperature reaches the set point, or the set point minus a small amount, the residential heating and cooling system 50 may stop the refrigeration cycle temporarily. The outdoor unit 58 includes a reheat system in accordance with present embodiments.

[0042] The residential heating and cooling system 50 may also operate as a heat pump. When operating as a heat pump, the roles of heat exchangers 60 and 62 are reversed. That is, the heat exchanger 60 of the outdoor unit 58 will serve as an evaporator to evaporate working fluid and thereby cool air entering the outdoor unit 58 as the air passes over the outdoor heat exchanger 60. The indoor heat exchanger 62 will receive a stream of air blown over it and will heat the air by condensing the working fluid.

[0043] In some embodiments, the indoor unit 56 may include a furnace system 70. For example, the indoor unit 56 may include the furnace system 70 when the residential heating and cooling system 50 is not configured to operate as a heat pump. The furnace system 70 may include a burner assembly and heat exchanger, among other components, inside the indoor unit 56. Fuel is provided to the burner assembly of the furnace system 70 where it is mixed with air and combusted to form a heat transfer fluid. The heat transfer fluid may pass through tubes or piping in a heat exchanger, separate from heat exchanger 62, such that air directed by the blower 66 passes over the tubes or pipes and extracts heat from the heat transfer fluid. The heated air may then be routed from the furnace system 70 to the ductwork 68 for heating the residence 52.

[0044] FIG. 4 is an embodiment of a vapor compression system 72 that can be used in any of the systems described above. The vapor compression system 72 may circulate a working fluid through a circuit starting with a compressor 74. The circuit may also include a condenser 76, an expansion valve(s) or device(s) 78, and an evaporator 80. The vapor compression system 72 may further include a control panel 82 that has an analog to digital (A / D) converter 84, a microprocessor 86, a non-volatile memory 88, and / or an interface board 90. The control panel 82 and its components may function to regulate operation of the vapor compression system 72 based on feedback from an operator, from sensors of the vapor compression system 72 that detect operating conditions, and so forth.

[0045] In some embodiments, the vapor compression system 72 may use one or more of a variable speed drive (VSDs) 92, a motor 94, the compressor 74, the condenser 76, the expansion valve or device 78, and / or the evaporator 80. The motor 94 may drive the compressor 74 and may be powered by the variable speed drive (VSD) 92. The VSD 92 receives alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source, and provides power having a variable voltage and frequency to the motor 94. In other embodiments, the motor 94 may be powered directly from an AC or direct current (DC) power source. The motor 94 may include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source, such as a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor, or another suitable motor.

[0046] The compressor 74 compresses a working fluid vapor and delivers the vapor to the condenser 76 through a discharge passage. In some embodiments, the compressor 74 may be a centrifugal compressor. The working fluid vapor delivered by the compressor 74 to the condenser 76 may transfer heat to a fluid passing across the condenser 76, such as ambient or environmental air 96. The working fluid vapor may condense to a working fluid liquid in the condenser 76 as a result of thermal heat transfer with the environmental air 96. The liquid working fluid from the condenser 76 may flow through the expansion device 78 to the evaporator 80.

[0047] The liquid working fluid delivered to the evaporator 80 may absorb heat from another air stream, such as a supply air stream 98 provided to the building 10 or the residence 52. For example, the supply air stream 98 may include ambient or environmental air, return air from a building, or a combination of the two. The liquid working fluid in the evaporator 80 may undergo a phase change from the liquid working fluid to a working fluid vapor. In this manner, the evaporator 80 may reduce the temperature of the supply air stream 98 via thermal heat transfer with the working fluid. Thereafter, the vapor working fluid exits the evaporator 80 and returns to the compressor 74 by a suction line to complete the cycle.

[0048] In some embodiments, the vapor compression system 72 may further include a reheat coil. In the illustrated embodiment, the reheat coil is represented as part of the evaporator 80. The reheat coil is positioned downstream of the evaporator heat exchanger relative to the supply air stream 98 and may reheat the supply air stream 98 when the supply air stream 98 is overcooled to remove humidity from the supply air stream 98 before the supply air stream 98 is directed to the building 10 or the residence 52.

[0049] It should be appreciated that any of the features described herein may be incorporated with the HVAC unit 12, the residential heating and cooling system 50, or other HVAC systems. Additionally, while the features disclosed herein are described in the context of embodiments that directly heat and cool a supply air stream provided to a building or other load, embodiments of the present disclosure may be applicable to other HVAC systems as well. For example, the features described herein may be applied to mechanical cooling systems, free cooling systems, chiller systems, or other heat pump or refrigeration applications.

[0050] To provide context for the following discussion, FIG. 5 is a schematic of an embodiment of a portion of an HVAC system 100 that includes a heat pump 102 (e.g., a heat pump system, reverse cycle heat pump, air source heat pump, energy efficient heat pump) in accordance with present embodiments. The heat pump 102 may include one or more components of the vapor compression system 72 discussed above and / or may be included in any of the systems described above (e.g., HVAC unit 12, heating and cooling system 50). The heat pump 102 includes a first heat exchanger 104 (e.g., indoor heat exchanger) and a second heat exchanger 106 (e.g., outdoor heat exchanger) that are fluidly coupled to one another via a working fluid circuit 108 or working fluid loop (e.g., one or more conduits, refrigerant circuit). The first heat exchanger 104 may be in thermal communication with (e.g., fluidly coupled to) a thermal load 110 (e.g., a room, space, and / or device) serviced by the heat pump 102, and the second heat exchanger 106 may be in thermal communication with an ambient environment 112 (e.g., the atmosphere) surrounding the HVAC system 100.

[0051] In some embodiments, a first fan 116 (e.g., blower) may direct a first air flow across the first heat exchanger 104 to facilitate heat exchange between working fluid within the first heat exchanger 104 and the thermal load 110, while a second fan 118 may direct a second air flow across the second heat exchanger 106 to facilitate heat exchange between working fluid within the second heat exchanger 106 and the ambient environment 112. One or more expansion devices 120 (e.g., electronic expansion valve [EEV], bi-directional expansion valve) may be disposed along the working fluid circuit 108 between the first heat exchanger 104 and the second heat exchanger 106 and may be configured to regulate (e.g., throttle) a flow of working fluid and / or a working fluid pressure differential between the first heat exchanger 104 and the second heat exchanger 106. In the illustrated embodiment, the working fluid circuit 108 includes a first expansion device 122 (e.g., expansion valve, indoor expansion device, EEV) disposed along the working fluid circuit 108 proximate the first heat exchanger 104 and a second expansion device 124 (e.g., expansion valve, outdoor expansion device, EEV) disposed along the working fluid circuit 108 proximate the second heat exchanger 106. However, in some embodiments the heat pump 102 may include one expansion device 120 (e.g., either the first expansion device 122 or the second expansion device 124).

[0052] The heat pump 102 also includes a compressor 130 (e.g., compressor system) disposed along the working fluid circuit 108. The compressor 130 is configured to direct working fluid flow through the working fluid circuit 108 and therefore through components disposed along the working fluid circuit 108, such as the first heat exchanger 104, the second heat exchanger 106, the expansion device(s) 120, and so forth. Although one compressor 130 is shown in the illustrated embodiment, the heat pump 102 may include any suitable quantity of compressors 130, such as two, three, four, five, six, or more than six compressors 130. The compressor 130 may be a multi-stage (e.g., two stage) compressor and / or a variable speed compressor. Additionally, the compressor 130 may be a high-side shell compressor, a rotary compressor, a scroll compressor, and / or any other suitable type of compressor. The compressor 130 is configured to receive working fluid (e.g., a primary flow of working fluid) via a suction conduit 132 fluidly coupled to a suction port 134 of the compressor 130 and to discharge working fluid (e.g., compressed working fluid) via a discharge conduit 136 fluidly coupled to a discharge port 138 of the compressor 130.

[0053] The compressor 130 may be fluidly coupled to a remainder of the working fluid circuit 108 via a reversing valve 150 (e.g., a switch-over valve). In the illustrated embodiment, the reversing valve 150 includes a first port 152 that is fluidly coupled to the suction conduit 132, a second port 154 that is fluidly coupled to the discharge conduit 136, a third port 156 that is fluidly coupled to a first conduit portion 158 extending to the first heat exchanger 104, and a fourth port 160 that is fluidly coupled to a second conduit portion 162 extending to the second heat exchanger 106.

[0054] The reversing valve 150 is configured to transition between a first configuration 164, in which the reversing valve 150 fluidly couples the first port 152 and the fourth port 160 and fluidly couples the second port 154 and the third port 156, and a second configuration 170, illustrated in FIG. 6, in which the reversing valve 150 fluidly couples the first port 152 and the third port 156 and fluidly couples the second port 154 and the fourth port 160. Accordingly, in the first configuration 164, the reversing valve 150 enables the compressor 130 to receive a flow of working fluid from the second heat exchanger 106 and to discharge a flow of working fluid to the first heat exchanger 104. Conversely, in the second configuration 170, the reversing valve 150 enables the compressor 130 to receive a flow of working fluid from the first heat exchanger 104 and to discharge a flow of working fluid to the second heat exchanger 106. In this way, while in the first configuration 164, the reversing valve 150 enables the heat pump 102 to operate in a heating mode, in which the first heat exchanger 104 rejects thermal energy to the thermal load 110 to heat the thermal load 110, and the second heat exchanger 106 absorbs thermal energy from the ambient environment 112. Further, while in the second configuration 170, the reversing valve 150 enables the heat pump 102 to operate in a cooling mode, in which the first heat exchanger 104 absorbs thermal energy from the thermal load 110 to cool the thermal load 110, and the second heat exchanger 106 rejects the absorbed thermal energy (e.g., absorbed from the thermal load 110) to the ambient environment 112. As such, while the reversing valve 150 is in the first configuration 164, the compressor 130 may direct a working fluid flow along at least a portion of the working fluid circuit 108 in a first flow direction 172. While the reversing valve 150 is in the second configuration 170, the compressor 130 may direct a working fluid flow along at least a portion of the working fluid circuit 108 in a second flow direction 174, opposite the first flow direction 172. For clarity, the heat pump 102 (e.g., energy efficient heat pump) is shown configured for operation in a heating mode in the illustrated embodiment of FIG. 5, and FIG. 6 is a schematic of an embodiment of a portion of the HVAC system 100 illustrating the heat pump 102 (e.g., energy efficient heat pump) configured for operation in a cooling mode.

[0055] The present discussion continues with reference to FIG. 5. The heat pump 102 may also include additional components, such as an accumulator 180 disposed along the working fluid circuit 108. More specifically, the accumulator 180 is disposed along the suction conduit 132 extending between the reversing valve 150 (e.g., the first port 152) and the suction port 134 of the compressor 130. In general, the accumulator 180 is configured to block flow of liquid working fluid to the compressor 130. In some instances and / or operating conditions, a portion of the working fluid directed from the reversing valve 150 and along the suction conduit 132 may be in a liquid phase. Accordingly, the accumulator 180 is configured to receive the flow of working fluid (e.g., two-phase working fluid) and to separate any liquid working fluid from vapor working fluid. The accumulator 180 may retain liquid working fluid therein and may output vapor or gaseous working fluid to flow to the compressor 130. In this way, flow of liquid working fluid to the compressor 130 may be avoided to protect the compressor 130 from wear and degradation.

[0056] In accordance with the present techniques, the heat pump 102 also includes a receiver 190 (e.g., vessel, liquid receiver, working fluid reservoir) disposed along the working fluid circuit 108. In particular, the receiver 190 is disposed along a liquid conduit portion 192 (e.g., conduit, conduit portion, liquid conduit) of the working fluid circuit 108 that extends between the first heat exchanger 104 and the second heat exchanger 106. The first expansion device 122 and the second expansion device 124 may also be disposed along the liquid conduit portion 192 and / or the liquid conduit portion 192 may extend between the first expansion device 122 and the second expansion device 124. The receiver 190 is configured to enable adjustable control of an amount of working fluid (e.g., liquid working fluid) circulating through the working fluid circuit 108. For example, the receiver 190 may define a chamber that is fluidly coupled to the working fluid circuit 108, and the chamber may be configured to receive and store a portion of working fluid received from the working fluid circuit 108. Thus, the portion of working fluid stored in the receiver 190 may not circulate through the working fluid circuit 108.

[0057] The receiver 190 includes a vessel 194 configured to receive and retain (e.g., store) working fluid from the working fluid circuit 108 to adjust an amount of the working fluid circulated (e.g., actively circulated) along the working fluid circuit 108. The vessel 194 may generally be arranged along an axis (e.g., a vertical axis, in a generally vertical orientation) to enable collection of working fluid within the vessel 194 at a base 196 of the vessel 194. The receiver 190 also includes a first dip tube 198 (e.g., pipe, tube, conduit) and a second dip tube 200 (e.g., pipe, tube, conduit) configured to enable flow of working fluid into and out of the vessel 194. To this end, the first dip tube 198 and the second dip tube 200 are fluidly coupled to the working fluid circuit 108 (e.g., liquid conduit portion 192). The first dip tube 198 and the second dip tube 200 may extend into the vessel 194 from an upper portion 202 of the vessel 194 and may extend through the vessel 194 (e.g., through an interior volume of the vessel 194) along a substantial portion (e.g., 50 percent, 60 percent, 70 percent, 80 percent, 90 percent) of a height 204 of the vessel 194 toward the base 196 of the vessel 194. In some embodiments, a first length of the first dip tube 198 extending along the height 204 of the vessel 194 and a second length of the second dip tube 200 extending along the height 204 of the vessel 194 may be approximately the same (e.g., similar) and / or approximately equal to one another (e.g., within 15 percent, within 10 percent, within 5 percent). As a result, the first dip tube 198 and / or the second dip tube 200 may direct working fluid from the working fluid circuit 108 (e.g., liquid conduit portion 192) to the base 196 of the vessel 194, and the first dip tube 198 and the second dip tube 200 may remain at least partially submerged within the working fluid retained and / or stored within the vessel 194. In other words, a liquid level 206 of working fluid within the vessel 194 may remain above (e.g., relative to a vertical axis, relative to a direction of gravity) at least a portion (e.g., ends, inlet, outlet) of the first dip tube 198 and the second dip tube 200 within the vessel 194.

[0058] As mentioned above, a desired amount (e.g. active charge) of working fluid flowing along the working fluid circuit 108 may vary depending on a configuration and / or design of the heat pump 102 (e.g., components of the heat pump 102, different relative volumes of the first heat exchanger 104 and the second heat exchanger 106), operating conditions of the heat pump 102, an active operating mode of the heat pump 102, and / or other parameters. Indeed, circulating a constant amount of working fluid through the working fluid circuit 108 in all operating conditions and / or operating modes may cause inefficient operation of the heat pump 102 in at least some of the operating conditions and / or operating modes. Therefore, embodiments of the heat pump 102 described herein include the receiver 190 configured to receive and retain (e.g., store) a variable amount of working fluid therein. In this way, an amount of working fluid circulated through the working fluid circuit 108 (e.g., not retained or stored within the receiver 190) may be adjusted, and more efficient operation of the heat pump 102 may be achieved across a wider range of operating conditions and / or operating modes. For example, an amount of working fluid retained within the receiver 190 may vary between a heating mode of the heat pump 102 and a cooling mode of the heat pump 102.

[0059] To enable adjustment of an amount of working fluid retained within the receiver 190 (e.g., vessel 194) during operation of the heat pump 102, operation of one or more components of the heat pump 102 (e.g., working fluid circuit 108) may be adjusted and / or otherwise controlled. For example, operation of the first expansion device 122, the second expansion device 124, or both may be adjusted to cause an adjustment to an amount of the working fluid retained within the receiver 190. To this end, the HVAC system 100 includes a controller 220 (e.g., control system, thermostat, control panel, control circuitry, automation controller, programmable controller) that is communicatively coupled to one or more components of the heat pump 102 (e.g., expansion devices 120) and is configured to monitor, adjust, and / or otherwise control operation of one or more components of the heat pump 102. For example, one or more control transfer devices, such as wires, cables, wireless communication devices, and the like, may communicatively couple the compressor 130, the expansion device(s) 120, the first and / or second fans 116, 118, the control device 16 (e.g., thermostat), and / or any other suitable components of the HVAC system 100 (e.g., heat pump 102) to the controller 220. That is, the compressor 130, the expansion device(s) 120, the first and / or second fans 116, 118, and / or the control device 16 may each have one or more communication components that facilitate wired or wireless (e.g., via a network) communication with the controller 220. In some embodiments, the communication components may include a network interface that enables the components of the HVAC system 100 to communicate via various protocols such as EtherNet / IP, ControlNet, DeviceNet, or any other communication network protocol. Alternatively, the communication components may enable the components of the HVAC system 100 to communicate via mobile telecommunications technology, Bluetooth®, near-field communications technology, and the like. As such, the compressor 130, the expansion device(s) 120, the first and / or second fans 116, 118, and / or the control device 16 may wirelessly communicate data between each other. In other embodiments, operational control of certain components of the heat pump 102 may be regulated by one or more relays or switches (e.g., a 24 volt alternating current [VAC] relay).

[0060] In some embodiments, the controller 220 may be a component of or may include the control panel 82. In other embodiments, the controller 220 may be a standalone controller, a dedicated controller, or another suitable controller included in the HVAC system 100. In any case, the controller 220 is configured to control components of the HVAC system 100 (e.g., heat pump 102) in accordance with the techniques discussed herein. The controller 220 includes processing circuitry 222, such as a microprocessor, which may execute software for controlling the components of the HVAC system 100. The processing circuitry 222 may include multiple microprocessors, one or more “general-purpose” microprocessors, one or more special-purpose microprocessors, and / or one or more application specific integrated circuits (ASICS), or some combination thereof. For example, the processing circuitry 222 may include one or more reduced instruction set (RISC) processors.

[0061] The controller 220 may also include a memory device 224 (e.g., a memory) that may store information, such as instructions, executable code, control software, look up tables, configuration data, other data, or any combination thereof. The memory device 224 may include a volatile memory, such as random access memory (RAM), and / or a nonvolatile memory, such as read-only memory (ROM). The memory device 224 may store a variety of information and may be used for various purposes. For example, the memory device 224 may store processor-executable instructions including firmware or software for the processing circuitry 222 to execute, such as instructions for controlling components of the HVAC system 100 (e.g., expansion devices 120). The memory device 224 may also store data relating to operating parameters of the HVAC system 100 (e.g., measured parameters, set points, etc.). In some embodiments, the memory device 224 is a tangible, non-transitory, machine-readable-medium that may store machine-readable instructions for the processing circuitry 222 to execute. The memory device 224 may include ROM, flash memory, a hard drive, or any other suitable optical, magnetic, or solid-state storage medium, or a combination thereof.

[0062] In accordance with present techniques, the controller 220 is configured to control operation of one or more components of the heat pump 102 to enable adjustment of an amount of working fluid retained within the vessel 194 of the receiver 190 (e.g., liquid level 206). In this way, an amount of working fluid circulated through the working fluid circuit 108 may be adjusted to enable more efficient operation of the heat pump 102. In other words, while the total amount of working fluid within then heat pump 102 may remain unchanged, an active amount of working fluid (e.g., charge, active charge) circulated through components of the heat pump 102 (e.g., first heat exchanger 104, second heat exchanger 106) may be adjusted or controlled by adjusting an amount of working fluid retained or stored within the receiver 190. The liquid level 206 (e.g., amount of working fluid) within the receiver 190 may be adjusted based on an operating mode of the heat pump 102 (e.g., heating mode, cooling mode), an operating parameter of the heat pump 102, another suitable parameter, or both. Additionally, the controller 220 may determine which of the one or more components of the heat pump 102 to control and / or adjust to cause an adjustment to the liquid level 206 (e.g., amount of working fluid) within the receiver 190, for example, based on an operating mode of the heat pump 102, based on a desired adjustment (e.g., increase, decrease) to the liquid level 206 within the receiver 190, another suitable parameter, or any combination thereof.

[0063] As mentioned above, a desired amount of working fluid (e.g., active charge) circulated through the working fluid circuit 108 may be different in the cooling mode and in the heating mode of the heat pump 102 (e.g., due to different relative volumes of the first heat exchanger 104 and the second heat exchanger 106). Accordingly, embodiments of the present disclosure are configured to adjust an amount of working fluid (e.g., liquid level 206) retained or stored within the receiver 190 based on operation of the heat pump 102 in a particular operating mode. For example, the controller 220 may be configured to adjust operation of one or more components of the heat pump 102 to cause the liquid level 206 in the receiver 190 to increase in the heating mode of the heat pump 102. In this way, an amount of the working fluid circulated along the working fluid circuit 108 may be reduced, which may enable more efficient operation of the heat pump 102 in the heating mode. Conversely, the controller 220 may be configured to adjust operation of one or more components of the heat pump 102 to cause the liquid level 206 in the receiver 190 to decrease, thereby increasing an amount of the working fluid circulated along the working fluid circuit 108, in the cooling mode of the heat pump 102 to enable more efficient operation of the heat pump 102 in the cooling mode. In some embodiments, the amount of working fluid retained or stored within the receiver 190 may be adjusted via control of an operating parameter (e.g., subcooling, superheating) of the working fluid that is circulated along the working fluid circuit 108. The controller 220 may control and / or adjust an amount of subcooling and / or superheating of the working fluid circulated along the working fluid circuit 108 via adjustment of one or more of the expansion devices 120, as described in further detail below.

[0064] During operation of the heat pump 102 in the heating mode, as illustrated in FIG. 5, the controller 220 may control operation of the heat pump 102 to increase the liquid level 206 of working fluid stored within the receiver 190 and thereby decrease an active charge of the working fluid circulated along the working fluid circuit 108. For example, the controller 220 may control operation of the first expansion device 122 to adjust an amount of subcooling of the working fluid exiting the first heat exchanger 104, which operates as a condenser in the heating mode. As will be appreciated, an amount of subcooling of the working fluid exiting the first heat exchanger 104 (e.g., condenser) may be indicative of an amount of liquid working fluid within (e.g., maintained within, trapped within) the first heat exchanger 104. The controller 220 may adjust the first expansion device 122 to decrease the amount of subcooling of the working fluid circuit exiting the first heat exchanger 104 and thereby decrease an amount of liquid working fluid contained within the first heat exchanger 104. For example, the controller 220 may adjust the first expansion device 122 toward an open position (e.g., fully open position) to enable increased flow of the working fluid therethrough. In this way, instead of an increased amount of liquid working fluid remaining within the first heat exchanger 104 (e.g., condenser), the liquid working fluid may flow along the working fluid circuit 108, through the first expansion device 122, and to the receiver 190 (e.g., along the liquid conduit portion 192). It should be appreciated that, during steady state operation of the heat pump 102 in the heating mode, the liquid working fluid flowing through the first expansion device 122 may not flash (e.g., vaporize), and the working fluid may remain in a liquid phase and flow along the liquid conduit portion 192 to the receiver 190. Specifically, the liquid working fluid may be directed into the vessel 194 via the first dip tube 198, and the liquid level 206 within the receiver 190 may increase. Accordingly, by adjusting (e.g., decreasing) the amount of subcooling of the working fluid exiting the first heat exchanger 104, such as via control and / or adjustment of the first expansion device 122, the controller 220 may reduce an amount of liquid working fluid maintained within the first heat exchanger 104 and may enable an increase in the amount of working fluid (e.g., liquid level 206) stored within the receiver 190.

[0065] The controller 220 may adjust operation of the first expansion device 122 to adjust (e.g., decrease) the amount of subcooling of the working fluid based on one or more parameters, metrics, and / or other factors. For example, the controller 220 may control the first expansion device 122 to cause the amount of subcooling of the working fluid to approach a subcooling set point (e.g., threshold amount of subcooling, subcooling amount set point, heating mode subcooling set point, first subcooling set point, target amount of subcooling). A value of the subcooling set point may be associated with operation of the heat pump 102 in the heating mode. For example, the subcooling set point may be selected, determined, and / or otherwise based on a desired amount of working fluid (e.g., active charge) actively circulated within the working fluid circuit 108 in the heating mode of the heat pump 102. In some embodiments, the subcooling set point associated with the heating mode may be a fixed value. In other embodiments, the controller 220 may be configured to adjust the subcooling set point and / or select a value of the subcooling set point based on one or more operating parameters and / or operating conditions of the heat pump 102. For example, the controller 220 may be configured to adjust the subcooling set point or select a particular value of the subcooling set point based on a detected parameter, such as an ambient temperature (e.g., within the ambient environment 112).

[0066] To these ends, the controller 220 may be communicatively coupled to and configured to receive data and / or feedback from one or more sensors 230 (e.g., temperature sensors, pressure sensors, flow rate sensors) indicative of one or more operating parameters of the heat pump 102. For example, a first sensor 232 may be disposed along the working fluid circuit 108 (e.g., liquid conduit portion 192) between the first heat exchanger 104 and the first expansion device 122. The first sensor 232 may be configured to detect a temperature and / or a pressure of the working fluid exiting the first heat exchanger 104. Based on data received from the first sensor 232, the controller 220 may determine and / or calculate an amount of subcooling (e.g., calculated amount of subcooling, measured amount of subcooling, actual amount of subcooling) of the working fluid exiting the first heat exchanger 104 (e.g., based on data stored on the memory device 224, based on a type of the working fluid). The controller 220 may compare the amount of subcooling (e.g., a value of the amount of subcooling) to the subcooling set point (e.g., stored on the memory device 224). Based on and / or in response to the comparison, the controller 220 may adjust (e.g., via one or more control signals) the first expansion device 122 to cause the amount of subcooling to approach the subcooling set point and enable flow (e.g., additional flow) of liquid working fluid from the first heat exchanger 104 to the receiver 190.

[0067] As mentioned above, the controller 220 may be configured to adjust the subcooling set point based on one or more operation parameters of the heat pump 102 detected by one or more of the sensors 230. For example, a second sensor 234 communicatively coupled to the controller 220 may be configured to detect a temperature (e.g., ambient temperature) of the ambient environment 112. Based on data received from the second sensor 234, the controller 220 may determine and implement an adjustment to the subcooling set point (e.g., stored on the memory device 224) associated with operation of the heat pump 102 in the heating mode to provide an adjusted subcooling set point. The controller 220 may then compare an actual or calculated amount of subcooling of the working fluid exiting the first heat exchanger 104 and control operation of the first expansion device 122 to cause the actual amount of subcooling to approach the adjusted subcooling set point in the manner described above. It should be appreciated that the controller 220 may receive data and / or feedback from other sensors 230 configured to detect other operating parameters, such as a temperature of the thermal load 110, an operating capacity of the compressor 130, a temperature and / or pressure of the working fluid exiting the second heat exchanger 106, an amount of working fluid within the receiver 190 (e.g., liquid level 206), another suitable operating, or any combination thereof. Indeed, the controller 220 may be configured to adjust the subcooling set point associated with the heating mode based on one or multiple operating parameters (e.g., detected by one or more sensors 230).

[0068] In some embodiments, the controller 220 may also be configured to control operation of the heat pump 102 to adjust an amount of superheat of the working fluid along the working fluid circuit 108 to cause an increase of the liquid level 206 of working fluid stored within the receiver 190 and thereby decrease an active charge of the working fluid circulated along the working fluid circuit 108 in the heating mode. As shown in the illustrated embodiment, the second expansion device 124 is disposed along the liquid conduit portion 192 between the receiver 190 and the second heat exchanger 106, which operates as an evaporator in the heating mode. Therefore, the second expansion device 124 may be controlled to adjust flow (e.g., a flow rate, an amount of flow) of the working fluid from the receiver 190 (e.g., via the second dip tube 200) to the second heat exchanger 106 to control and / or adjust the liquid level 206 in the receiver 190, as well as an amount of superheat of the working fluid exiting the second heat exchanger 106. For example, the controller 220 may be configured to adjust the second expansion device 124 toward a closed position (e.g., a fully closed position) to decrease flow of the working fluid into the second heat exchanger 106 in order to increase the amount of superheat of the working fluid exiting the second heat exchanger 106. Decreasing flow of the working fluid to the second heat exchanger 106 may also cause the liquid level 206 of the working fluid within the receiver 190 to increase, which may reduce an amount (e.g., active charge) of the working fluid actively circulating along the working fluid circuit 108. Accordingly, by adjusting (e.g., increasing) the amount of superheat of the working fluid exiting the second heat exchanger 106, such as via control and / or adjustment of the second expansion device 124, the controller 220 may enable an increase in the amount of working fluid (e.g., liquid level 206) stored within the receiver 190.

[0069] The controller 220 may be configured to control an amount of superheat of the working fluid exiting the second heat exchanger 106 based on data and / or feedback received from one or more of the sensors 230. For example, a third sensor 236 may be disposed along the working fluid circuit 108 between the second heat exchanger 106 and the reversing valve 150. The third sensor 236 may be configured to detect a temperature and / or a pressure of the working fluid exiting the second heat exchanger 106. Based on data received from the third sensor 236, the controller 220 may determine and / or calculate an amount of superheat (e.g., calculated amount of superheat, measured amount of superheat, actual amount of superheat) of the working fluid exiting the second heat exchanger 106 (e.g., based on data stored on the memory device 224, based on a type of the working fluid). The controller 220 may compare the amount of superheat (e.g., a value of the amount of superheat) to a superheat set point (e.g., stored on the memory device 224). Based on and / or in response to the comparison, the controller 220 may adjust (e.g., via one or more control signals) the second expansion device 124 to cause the amount of superheat to approach the superheat set point and enable retention of liquid working fluid (e.g., additional working fluid) within the receiver 190.

[0070] The controller 220 may be configured to adjust the superheat set point based on one or more operation parameters of the heat pump 102 detected by one or more of the sensors 230. For example, based on data received from the second sensor 234 (e.g., an ambient temperature measurement), the controller 220 may determine and implement an adjustment to the superheat set point (e.g., stored on the memory device 224) associated with operation of the heat pump 102 in the heating mode to provide an adjusted superheat set point. The controller 220 may then compare an actual or calculated amount of superheat of the working fluid exiting the second heat exchanger 106 and control operation of the second expansion device 124 to cause the actual amount of superheat to approach the adjusted superheat set point in the manner described above. It should be appreciated that the controller 220 may receive data and / or feedback from other sensors 230 configured to detect other operating parameters, such as a temperature of the thermal load 110, an operating capacity of the compressor 130, a temperature and / or pressure of the working fluid exiting the second heat exchanger 106, an amount of working fluid within the receiver 190 (e.g., liquid level 206), another suitable operating, or any combination thereof. Indeed, the controller 220 may be configured to adjust the superheat set point associated with the heating mode based on one or multiple operating parameters (e.g., detected by one or more sensors 230).

[0071] As mentioned above, FIG. 6 is a schematic of an embodiment of a portion of the HVAC system 100 that includes the heat pump 102 (e.g., a heat pump system, reverse cycle heat pump, air source heat pump, energy efficient heat pump) in accordance with present embodiments. The illustrated embodiment of the heat pump 102 is configured for operation in the cooling mode. Accordingly, the reversing valve 150 is in the second configuration 170 described above, the first heat exchanger 104 is configured to operate as an evaporator, and the second heat exchanger 106 is configured to operate as a condenser.

[0072] In the cooling mode, operation of the heat pump 102 may also be controlled to adjust an amount of working fluid flowing along the working fluid circuit 108 (e.g., active charge) and / or to adjust an amount of working fluid retained within the receiver 190. As discussed above, a desired amount (e.g. active charge) of working fluid flowing along the working fluid circuit 108 may vary depending on a configuration and / or design of the heat pump 102 (e.g., components of the heat pump 102, different relative volumes of the first heat exchanger 104 and the second heat exchanger 106), operating conditions of the heat pump 102, an active operating mode of the heat pump 102, and / or other parameters. Indeed, a desired active charge of the working fluid flowing along the working fluid circuit 108 may be different in the cooling mode than a desired active charge of the working fluid flowing along the working fluid circuit 108 in the heating mode (e.g., due to different relative volumes of the first heat exchanger 104 and the second heat exchanger 106, due to operation of the first heat exchanger 104 as an evaporator and operation of the second heat exchanger 106 as a condenser in the cooling mode).

[0073] To enable adjustment of an amount of working fluid retained within the receiver 190 (e.g., vessel 194) during operation of the heat pump 102, operation of one or more components of the heat pump 102 (e.g., working fluid circuit 108) may be adjusted and / or otherwise controlled, as similarly described above with reference to FIG. 5. For example, the controller 220 may be configured to adjust operation of one or more components of the heat pump 102 to cause the liquid level 206 in the receiver 190 to decrease, thereby increasing an amount of the working fluid circulated along the working fluid circuit 108, in the cooling mode of the heat pump 102. In particular, with the first heat exchanger 104 configured to operate as an evaporator and the second heat exchanger 106 configured to operate as a condenser in the cooling mode, the controller 220 may be configured to adjust operation of the second expansion device 124 to adjust (e.g., increase) an amount of subcooling of the working fluid exiting the second heat exchanger 106 and / or the controller 220 may be configured to adjust operation of the first expansion device 122 to adjust (e.g., decrease) an amount of superheat of the working fluid exiting the first heat exchanger 104 to cause a decrease of the liquid level 206 of working fluid stored within the receiver 190 and thereby increase an active charge of the working fluid circulated along the working fluid circuit 108 in the cooling mode. The controller 220 may be configured to adjust operation of the second expansion device 124 to adjust subcooling of the working fluid in a manner similar to the control of the first expansion device 122 to adjust subcooling of the working fluid in the heating mode. Similarly, the controller 220 may be configured to adjust operation of the first expansion device 122 to adjust superheat of the working fluid in a manner similar to the control of the second expansion device 124 to adjust superheat of the working fluid in the heating mode.

[0074] The controller 220 may also control operation of the first expansion device 122 to adjust superheat of the working fluid and / or control operation of the second expansion device 124 to adjust subcooling of the working fluid in accordance with one or more of the techniques described above with reference to FIG. 5. For example, the controller 220 may control the first expansion device 122 to adjust an amount of superheat of the working fluid exiting the first heat exchanger 104 based on data and / or feedback received from one or more of the sensors 230, such as a fourth sensor 240 (e.g., pressure sensor, temperature sensor) disposed downstream of the first heat exchanger 104 relative to a flow of the working fluid along the working fluid circuit 108 in the cooling mode. The controller 220 may control the second expansion device 124 to adjust an amount of subcooling of the working fluid exiting the second heat exchanger 106 based on data and / or feedback received from one or more of the sensors 230, such as a fifth sensor 242 (e.g., pressure sensor, temperature sensor) disposed downstream of the second heat exchanger 106 relative to a flow of the working fluid along the working fluid circuit 108 in the cooling mode. It should be appreciated that any of the sensors 230, data, and / or feedback described herein may be utilized by the controller 220 to enable adjustment of the first expansion device 122 and / or the second expansion device 124 to control superheat and / or subcooling of the working fluid, and thereby control and / or adjust an amount of working fluid retained within the receiver 190, in the cooling mode of the heat pump 102.

[0075] Additionally, the controller 220 may be configured to control the first expansion device 122 to adjust an amount of superheat of the working fluid exiting the first heat exchanger 104 to approach a superheat set point in the cooling mode (e.g., threshold amount of superheat, superheat amount set point, cooling mode superheat set point, second superheat set point, target amount of superheat), as similarly described above. The controller 220 may also be configured to control the second expansion device 124 to adjust an amount of subcooling of the working fluid exiting the second heat exchanger 106 to approach a subcooling set point in the cooling mode (e.g., threshold amount of subcooling, subcooling amount set point, cooling mode subcooling set point, second subcooling set point, target amount of subcooling). The superheat set point and / or the subcooling set point (e.g., stored on the memory device 224) utilized in the cooling mode may be different than the superheat set point and / or the subcooling set point utilized in the heating mode (e.g., due to varying volumes, such as internal volumes, of the first heat exchanger 104 and second heat exchanger 106), which may enable the heat pump 102 to store different amounts of working fluid within the receiver 190 and operate with different active charges of working fluid flowing along the working fluid circuit 108 in the different operating modes of the heat pump 102. The superheat set point and / or the subcooling set point (e.g., stored on the memory device 224) utilized in the cooling mode may be different than the superheat set point and / or the subcooling set point utilized in the heating mode (e.g., due to varying volumes, such as internal volumes, of the first heat exchanger 104 and second heat exchanger 106), which may enable the heat pump 102 to store different amounts of working fluid within the receiver 190 and operate with different active charges of working fluid flowing along the working fluid circuit 108 in the different operating modes of the heat pump 102. For example, the subcooling set point utilized in the cooling mode may be higher than the subcooling set point utilized in the heating mode to enable an increase in the active charge for working fluid circulated along the working fluid circuit 108 during operation of the heat pump 102 in the cooling mode. The superheat set point and / or the subcooling set point utilized in the cooling mode may also be adjusted, such as based on data received from one or more of the sensors 230, as discussed above.

[0076] It should be noted that, during operation of the heat pump 102 in each of the cooling mode and the heating mode, the controller 220 may be configured to control operation of the first expansion device 122 and the second expansion device 124 independently of one another to enable independent control of the amount of superheat and the amount of subcooling of the working fluid circulated along the working fluid circuit 108. Even so, control of the heat pump 102 and the components thereof may nevertheless be dependent on a desirable charge (e.g., active charge) of the working fluid flowing through the working fluid circuit 108. As will be appreciated, adjustment of one of the expansion devices 122, 124 to adjust one of the amount of superheat or the amount of subcooling may affect control of the other of the expansion devices 122, 124 to adjust the other of the amount of superheat or the amount of subcooling.

[0077] In some embodiments, the controller 220 may be configured to control and / or adjust operation of the first expansion device 122 and the second expansion device 124 based on a prioritization scheme. For example, in the heating mode, the controller 220 may be configured to first adjust operation the first expansion device 122 to cause the amount of subcooling (e.g., measured amount of subcooling, calculated amount of subcooling, subcooling of working fluid exiting the first heat exchanger 104) to approach a subcooling set point associated with operation of the heat pump 102 in the heating mode. In response to a determination that the amount of subcooling reaches the subcooling set point and / or in response to a determination that the amount of subcooling is within a threshold amount (e.g., a threshold value, a threshold percentage) of the subcooling set point, the controller 220 may then adjust operation of the second expansion device 124 to cause the amount of superheat (e.g., measured amount of superheat, calculated amount of superheat, superheat of working fluid exiting the second heat exchanger 106) to approach a superheat set point associated with operation of the heat pump 102 in the heating mode. In the cooling mode, the controller 220 may be configured to first adjust operation the second expansion device 124 to cause the amount of subcooling (e.g., measured amount of subcooling, calculated amount of subcooling, subcooling of working fluid exiting the second heat exchanger 106) to approach a subcooling set point associated with operation of the heat pump 102 in the cooling mode. In response to a determination that the amount of subcooling reaches the subcooling set point and / or in response to a determination that the amount of subcooling is within a threshold amount (e.g., a threshold value, a threshold percentage) of the subcooling set point, the controller 220 may then adjust operation of the first expansion device 122 to cause the amount of superheat (e.g., measured amount of superheat, calculated amount of superheat, superheat of working fluid exiting the first heat exchanger 104) to approach a superheat set point associated with operation of the heat pump 102 in the heating mode. Indeed, in some embodiments, the controller 220 may be configured to prioritize adjustment of an amount of subcooling of the working fluid in both the heating mode and the cooling mode, but in other embodiments the controller 220 may be configured to control the first expansion device 122 and the second expansion device 124 based on another priority scheme and / or simultaneously (e.g., without prioritization of controlling the amount of subcooling or the amount of superheat).

[0078] In some embodiments, the heat pump 102 may be configured to regulate the active charge of working fluid circulating through the working fluid circuit 108 at least partially based on the liquid level 206 within the receiver 190. To this end, the receiver 190 may include a fluid level sensor 228 (e.g., liquid level sensor) configured to detect the liquid level 206 (e.g., amount of liquid, volume of liquid, height of liquid) in the vessel 194. Based on the liquid level 206 detected via the fluid level sensor 228, the controller 220 may determine or deduce the active charge within the working fluid circuit 108. For example, the controller 220 may include instructions (e.g., one or more lookup tables, charts, and / or algorithms) stored in the memory device 224 correlating amounts of active charge of working fluid circulating through working fluid circuit 108 (e.g., values indicative of different active charge amounts) with liquid level 206 amounts in the receiver 190 (e.g., values indicative of different levels or amounts of liquid within the receiver 190). In some embodiments, the controller 220 may determine a total volume of working fluid within the receiver 190 based on one or more structural features of the receiver 190 (e.g., dimensions of the vessel 194, dimensions of internal components (e.g., dip tubes)) and data received from the fluid level sensor 228 (e.g., liquid level 206). The liquid level 206 may be indicative of a portion of the total internal volume of the vessel 194 occupied by liquid working fluid.

[0079] Based on a determination of the volume of working fluid within the receiver 190, the controller 220 may determine the active charge of working fluid circulating throughout the working fluid circuit 108. For example, the controller 220 may include instructions within the memory device 224 relating active charge to the total charge and the total volume of working fluid in the receiver 190. Specifically, the controller 220 may determine a difference between the volume of working fluid in the receiver 190 and the total charge of working fluid in the heat pump 102 to determine the active charge of working fluid circulating along the working fluid circuit 108. In some embodiments, the total charge of working fluid in the heat pump 102 may be an initial amount of working fluid installed with the heat pump 102 during, for example, installation or maintenance. As such, the total charge of working fluid in the working fluid circuit 108 may be a predetermined and / or known value and may be stored in the memory device 224.

[0080] In some embodiments, the memory device 224 of the controller 220 may include or store instructions (e.g., one or more algebraic equations, tables, and / or look up charts) to determine a desired active charge of working fluid based on an operating mode of the heat pump 102, one or more parameters of the heat pump 102, respective internal volumes of the first heat exchanger 104 and / or the second heat exchanger, ambient temperatures, another suitable parameter, or a combination thereof. In response to a determination of a desired active charge of working fluid to circulate through the working fluid circuit 108, the controller 220 may then compare the active charge of working fluid (e.g., determined by the controller 220, determined active charge) to the desired charge of working fluid to circulate through the working fluid circuit 108.

[0081] In response to a determination that the active charge of working fluid circulating through the working fluid circuit 108 is less than the desired charge, the controller 220 may actuate one or more components of the heat pump 102 (e.g., expansion devices 120) to decrease the liquid level 206 in the receiver 190 in a manner similar to that discussed above in order to increase the active charge of working fluid circulating through the working fluid circuit 108. In response to a determination that the active charge circulating through the working fluid circuit 108 is greater than the desired charge, the controller 220 may actuate one or more components of the heat pump 102 to increase the liquid level 206 in the receiver 190 in a manner similar to that discussed above to cause a decrease in the active charge.

[0082] While the presently disclosed techniques are described in the context of embodiments of the heat pump 102 configured as air-source heat pumps (e.g., air-to-air heat pumps) utilizing the first heat exchanger 104 and the second heat exchanger 106 configured as air-to-fluid (e.g., air-to-working fluid) heat exchangers, it should be appreciated that the present techniques may also be utilized with embodiments of the heat pump 102 having other configurations, such as air-to-liquid heat pumps having at least one heat exchanger configured to place a working fluid in a heat exchange relationship with a flow of liquid, such as water. For example, FIGS. 7 and 8 are schematics of an embodiment of a portion of the HVAC system 100 including the heat pump 102 with the first heat exchanger 104 configured as a working fluid-to-liquid heat exchanger. For example, the first heat exchanger 104 may be configured to place the working fluid circulated along the working fluid circuit 108 in a heat exchanger relationship with a flow of liquid, such as water, received from the thermal load 110 (e.g., air handling equipment, terminal unit, air handler) and to supply a conditioned (e.g., heated, cooled) flow of liquid to the thermal load 110 to enable conditioning of the thermal load 110. FIG. 7 illustrates the heat pump 102 configured for operation in the heating mode, and FIG. 8 illustrates the heat pump 102 configured for operation in the cooling mode. The second heat exchanger 106 of the illustrated embodiments is configured to place the working fluid in a heat exchange relationship with ambient air from the ambient environment 112, as similarly described above. It should be appreciated that the embodiments of the heat pump 102 illustrated in FIGS. 7 and 8 may be configured as a chiller system or other embodiment of the heat pump 102 configured to cool and / or heat a flow of liquid (e.g., water).

[0083] As similarly described above, the respective configurations of the first heat exchanger 104 (e.g., working fluid-to-liquid heat exchanger) and the second heat exchanger 106 (e.g., working fluid-to-air heat exchanger) may be different from one another. For example, the second heat exchanger 106 may have a greater (e.g., significantly greater) internal volume (e.g., internal working fluid volume, second internal volume) than the internal volume of the first heat exchanger 104 (e.g., internal working fluid volume, first internal volume). Indeed, a variety of different heat exchanger configurations (e.g., microchannel tubes, shell and tube, round-tube) may be utilized for the first heat exchanger 104 and the second heat exchanger 106, which may demand different active charges of working fluid flowing along the working fluid circuit 108 in different operating modes of the heat pump 102 to enable more efficient operation of the heat pump 102. Accordingly, the present techniques enabling adjustment of the active charge of working fluid within the working fluid circuit 108 may be implemented with such configurations of the heat pump 102, such as the configurations illustrated in FIGS. 7 and 8, to enable more efficient operation of the heat pump 102 in the heating mode and the cooling mode. The present techniques may also enable improved (e.g., more efficient) operation of heat pumps 102 utilizing certain types of working fluids, such as high glide refrigerants (e.g., R-454C, R-474A).

[0084] As discussed above, embodiments of the present disclosure include the controller 220 configured to control operation of the heat pump 102 (e.g., expansion devices 120) to enable more efficient operation of the heat pump 102 across a wider range of operating conditions. For example, the controller 220 may be configured to execute one or more control sequences to adjust one or more of the expansion devices 120 based on an operating mode of the heat pump 102 and / or based on operating conditions of the heat pump 102. As described in further detail below, the control sequences executed by the controller 220 may enable control of the heat pump 102 to achieve one or more desired operating parameters (e.g., active working fluid charge level), such as based on an active operating mode (e.g., heating mode, cooling mode) and / or operating conditions of the heat pump 102. In this way, the present techniques enable more efficient operation of the heat pump 102 across a wider range of operating conditions.

[0085] With the foregoing in mind, FIGS. 9 is a flow chart of an embodiment of a control sequence or method 300 for operating the heat pump 102, and FIGS. 10 and 11 are flow charts of embodiments of various control sequence (e.g., portions) of the method 300, in accordance with aspects of the present disclosure. As will be appreciated, one or more steps (e.g., control sequences) of the method 300 may be performed by the controller 220. For example, computer executable instructions or code for performing the one or more control sequences and / or other portions of the method 300 may be stored on the memory device 224, and the processing circuitry 222 may execute the instructions to perform the one or more control sequences of the method 300. In some embodiments, one or more steps of the method 300 may be performed by another controller of the HVAC system 100. In additional or alternative embodiments, multiple components or systems may perform one or more steps of the method 300. It should also be noted that additional steps may be performed with respect to the illustrated method 300 and control sequences thereof. Moreover, certain steps of the method 300 may be removed, modified, and / or performed in a different order. In some embodiments, certain steps of the method 300 may not be performed, for example, based on a configuration of the heat pump 102, such as based on a number and / or arrangement of the expansion devices 120 included in the heat pump 102. In some embodiments of the heat pump 102 including the first expansion device 122 and the second expansion device 124, the controller 220 may be configured to execute all or substantially all of the steps and / or control sequences of the method 300. Further still, one or more of the steps of the method 300 described herein may be performed in any suitable relation with one another, such as in response to one another and / or in parallel with one another.

[0086] As indicated by blocks 302 and 304 of FIG. 9, the method 300 may begin with initiating or starting operation of the heat pump 102 and receiving a call for conditioning. For example, the controller 220 may receive the call for conditioning from a thermostat of the HVAC system 100, and the call for conditioning may be indicative of a desired type of conditioning (e.g., heating, cooling) for the space to be conditioned.

[0087] The method 300 may proceed to block 306, and a determination may be made regarding whether a demand for heating of the space to be conditioned by the heat pump 102 exists. For example, the controller 220 may determine whether the call for conditioning is indicative of a call or demand for heating. If a demand for heating exists, the method 300 may continue to a heating control sequence 320, which is described further below with reference to FIG. 10.

[0088] In response to a determination that a demand for heating does not exist at block 306, a determination may be made regarding whether a demand for cooling exits, as indicated by block 308. For example, the controller 220 may determine whether the call for conditioning is indicative of a call or demand for cooling. In response to a determination that a demand for cooling exists, the method 300 may continue to the cooling control sequence 344, which is described further below with reference to FIG. 11. As will be appreciated, the decisions made in block 306 and block 308 may be performed in an alternate order or may be performed simultaneously.

[0089] In response to a determination that a demand for heating does not exit, and a demand for cooling does not exist, the method 300 may continue to block 310, whereby the method 300 may end. For example, at block 310, the heat pump 102 may not initiate operation in the cooling mode or the heating mode. In some embodiments, the heat pump 102 may transition or remain in an idle or non-operating state at block 310.

[0090] Referring now to FIG. 10, a flow chart of an embodiment of a portion of the method 300, illustrating the heating control sequence 320, is shown. As mentioned above, the method 300 may proceed to the heating control sequence 320 in response to a determination that a demand for heating exists at block 306 described above. Execution of the heating control sequence 320 may coincide with operation of the heat pump 102 in the heating mode. To enable operation of the heat pump 102 in the heating mode, the reversing valve 150 may be actuated to and / or be maintained in the first configuration 164. Thus, in some instances, the heating control sequence 320 may include a step of transitioning the reversing valve 150 to the first configuration 164.

[0091] The heating control sequence 320 may begin with block 322. At block 322, the first expansion device 122 (e.g., indoor EEV) may be adjusted to a fully open position. In this way, working fluid discharged by the first heat exchanger 104 in the heating mode of the heat pump 102 may flow through the first expansion device 122 with reduced and / or without inducing a pressure drop and / or flow restriction (e.g., throttling) of the working fluid. Thus, the working fluid discharged from the first heat exchanger 104 may flow towards the receiver 190 in a liquid phase. In some embodiments, the controller 220 may maintain the first expansion device 122 in a fully open configuration for a predetermined period of time before the heating control sequence 320 proceeds to block 324 and / or block 326. In other embodiments, the controller 220 may maintain the first expansion device 122 in a fully open configuration until the receiver 190 is operating at steady state (e.g., working fluid flowing into the receiver 190 is equal to or approximately equal to working fluid flowing out of the receiver 190).

[0092] The heating control sequence 320 may then proceed to block 324 and / or block 326. At block 324, an actual superheat value (e.g., measured superheat value, calculated superheat value) of the working fluid exiting the second heat exchanger 106 may compared to a superheat set point (e.g., superheat set point value) to determine whether the actual superheat value is less than the superheat set point. In some embodiments, the actual superheat value may be calculated by subtracting the saturation temperature of the working fluid within the second heat exchanger 106 from a measured temperature (e.g., actual temperature, measured via third sensor 236) of the working fluid exiting the second heat exchanger 106. The saturation temperature may be determined via detections or measurements (e.g., pressure measurement) of one or more sensors 230 located, for example, at an outlet of the second heat exchanger 106 (e.g., third sensor 236). Similarly, the temperature of the working fluid exiting the second heat exchanger 106 may be measured via detections or measurements of one or more sensors 230 also located, for example, at an outlet of the second heat exchanger 106 (e.g., third sensor 236). To this end, the controller 220 may be configured to receive data and / or feedback from one or more sensors 230 of the heat pump 102, such as working fluid pressure sensors (e.g., suction pressure sensor, discharge pressure sensor), an ambient temperature sensor, a working fluid temperature sensor, and / or other suitable sensor to determine (e.g., calculate) an actual superheat value of the working fluid exiting the second heat exchanger 106.

[0093] Further, in some embodiments, the superheat set point may be a predetermined set point stored in the memory device 224 of the controller 220. The heat pump 102 may have a predetermined superheat set point that may be based on one or more parameters of the heat pump 102 and / or an operational configuration (e.g., operating mode) of the heat pump 102. For instance, the memory device 224 of the controller 220 may store different superheat set point values associated with the heating mode and the cooling mode of the heat pump 102. For example, in the heating mode configuration illustrated in FIG. 5 and for which the heating control sequence 320 of FIG. 10 may be executed, the superheat set point may be greater than the superheat set point associated with the cooling mode of the heat pump 102. Furthermore, the superheat set point may be based on one or more parameters of the heat pump 102, such as respective internal volumes of the first heat exchanger 104 and / or the second heat exchanger 106. In other embodiments, the superheat set point may be calculated, selected, and / or otherwise determined (e.g., via the controller 220), such as based on an ambient temperature or another operating condition or the heat pump 102 (e.g., measured by one or more of the sensors 230).

[0094] In response to a determination that the actual superheat value is less than the superheat set point, the heating control sequence 320 may proceed to block 328. At block 328, the second expansion device 124 (e.g., outdoor EEV) may be controlled to adjust the actual superheat value of the heat pump 102. For example, the controller 220 may control, adjust, or otherwise operate the second expansion device 124 to cause the actual superheat value of the working fluid to approach the superheat set point. To this end, one or more values of the superheat set point may be stored in the memory device 224 of the controller 220, and / or the controller 220 may receive feedback from one or more of the sensors 230 (e.g., temperature and / or pressure sensors disposed along the working fluid circuit 108) to determine whether adjustment of the second expansion device 124 is desired to achieve the superheat set point. As described above, by controlling the second expansion device 124 to increase the actual superheat value (e.g., by adjusting the second expansion device 124 towards a closed position), the liquid level 206 within the receiver 190 may be increased. Accordingly, the active charge of working fluid circulating through the working fluid circuit 108 may decrease, which may enable more efficient operation of the heat pump 102 in the heating mode.

[0095] Based on a determination that actual superheat value is greater than or equal to superheat set point, the heating control sequence 320 may proceed to block 330. At block 330, the second expansion device 124 (e.g., outdoor EEV) may be controlled to adjust towards a fully open position. As will be appreciated, adjusting the second expansion device 124 towards the fully open position may increase the flow of working fluid into the second heat exchanger 106 and thereby decrease the actual superheat value of the working fluid. As a result, the liquid level 206 of working fluid retained and / or stored in the receiver 190 may decrease and thereby increase the active charge of working fluid circulating through the working fluid circuit 108. In the manner described above, the controller 220 may control operation of the second expansion device 124 to adjust the actual superheat value of the working fluid exiting the second heat exchanger 106 (e.g., toward a superheat set point value associated with the heating mode) and thereby adjust an amount of working fluid retained within the receiver 190 to effectuate an adjustment to the active charge of working fluid circulated through the working fluid circuit 108 to increase the efficiency of the heat pump 102.

[0096] Referring back to block 322, after the controller 220 adjusts the first expansion device 122, the heating control sequence 320 may also proceed to block 326. In some embodiments, the heating control sequence 320 may execute both blocks 324 and 326 simultaneously. At block 326, an actual subcooling value (e.g., measured subcooling value, calculated subcooling value) may be compared to a subcooling set point (e.g., subcooling set point value) to determine whether the actual subcooling value is less than the subcooling set point. In some embodiments, the actual subcooling value may be calculated by subtracting the saturation temperature of the working fluid within the first heat exchanger 104 from a measured temperature (e.g., actual temperature, measured via first sensor 232) of the working fluid exiting the first heat exchanger 104. The saturation temperature may be determined via detections or measurements (e.g., pressure measurement) of one or more sensors 230 located, for example, at an outlet of the first heat exchanger 104 (e.g., first sensor 232). Similarly, the temperature of the working fluid exiting the first heat exchanger 104 may be measured via detections or measurements of one or more sensors 230 also located, for example, at an outlet of the first heat exchanger 104 (e.g., first sensor 232). To this end, the controller 220 may be configured to receive data and / or feedback from one or more sensors 230 of the heat pump 102, such as working fluid pressure sensors (e.g., suction pressure sensor, discharge pressure sensor), an ambient temperature sensor, a working fluid temperature sensor, or other suitable sensor to determine (e.g., calculate) an actual subcooling value of the working fluid exiting the first heat exchanger 104.

[0097] Further, in some embodiments, the subcooling set point may be a predetermined set point stored in the memory device 224 of the controller 220. The heat pump 102 may have a predetermined subcooling set point that may be based on one or more parameters of the heat pump 102 and / or a configuration of the heat pump 102. For instance, the memory device 224 of the controller 220 may store different subcooling set point values associated with the heating mode and the cooling mode of the heat pump 102. For example, in the heating mode illustrated in FIG. 5 and for which the heating control sequence 320 of FIG. 10 may be executed, the subcooling set point may be less than the subcooling set point associated with the cooling mode of the heat pump 102. Furthermore, the subcooling set point may be based on one or more parameters of the heat pump 102, such as internal volumes of the first heat exchanger 104 and / or the second heat exchanger 106. In other embodiments, the subcooling set point may be calculated, selected, and / or otherwise determined (e.g., via the controller 220), such as based on an ambient temperature and / or another operating condition or the heat pump 102 (e.g., measured by one or more of the sensors 230).

[0098] In response to a determination that the actual subcooling value is less than the subcooling set point, the heating control sequence 320 may proceed to block 332. At block 332, the first expansion device 122 (e.g., indoor EEV) may be controlled to adjust the actual subcooling value of the heat pump 102. For example, the controller 220 may control, adjust, or otherwise operate the first expansion device 122 to cause the actual subcooling value of the working fluid to approach the subcooling set point. To this end, one or more values of the subcooling set point may be stored in the memory device 224 of the controller 220, and / or the controller 220 may receive feedback from one or more of the sensors 230 (e.g., temperature and / or pressure sensors disposed along the working fluid circuit 108) to determine whether adjustment of the first expansion device 122 is desired to achieve the subcooling set point. In some embodiments, adjusting the first expansion device 122 to adjust the actual subcooling value may at least partially restrict flow of the working fluid leaving the first heat exchanger 104. As such, the residence time of the working fluid in the first heat exchanger 104 may increase, thereby causing an increase in the actual subcooling value due to an increased amount of working fluid in the first heat exchanger 104. In this way, the receiver 190 may experience a decrease in working fluid, thus decreasing the liquid level 206. Accordingly, the charge (e.g., working fluid) circulating through the working fluid circuit 108 may increase. As such, by controlling the subcooling set point, the controller 220 may also directly control the amount of charge circulating through the working fluid circuit 108, thus increasing the efficiency of the heat pump 102 and decreasing emission of greenhouse gases.

[0099] Based on a determination that actual subcooling value is greater than or equal to the subcooling set point, the heating control sequence 320 may proceed to block 334. At block 334, the first expansion device 122 (e.g., indoor EEV) is maintained in the fully open position. As will be appreciated, adjusting the first expansion device 122 to a fully opened position may increase the flow of working fluid out of the first heat exchanger 104, decreasing the amount of working fluid in the first heat exchanger 104 and the residence time of the working fluid in the first heat exchanger 104. As such, the actual subcooling in the heat pump 102 may decrease. Further, the adjusting of the first expansion device 122 may result in the receiver 190 experiencing an increase in working fluid, thus increasing the liquid level 206. Accordingly, the charge of working fluid circulating through the working fluid circuit 108 may decrease.

[0100] After blocks 328, 330, 332, and 334 the heating control sequence 320 may proceed to block 316 to end the heating control sequence 320. In some embodiments, subsequent to execution of the steps in blocks 328, 330, 332, and 334, the sequence may restart at blocks 324 and / or 326, creating an iterative sequence to adjust the expansion devices 120 to achieve the subcooling set point, the superheat set point, and a desired active charge of working fluid circulating in the working fluid circuit 108 in the heating mode.

[0101] Referring now to FIG. 11, a flow chart of an embodiment of the method 300, illustrating the cooling control sequence 344, is shown. As mentioned above, the method 300 may proceed to the cooling control sequence 344 in response to the determination that a demand for cooling exists at block 308 of the method 300. In other words, the cooling control sequence 344 may be executed in a cooling mode of the heat pump 102. As discussed above, the reversing valve 150 may be actuated to and / or maintained in the second configuration 170 in the cooling mode of the heat pump 102. Thus, in some instances, the cooling control sequence 344 may include a step of transitioning the reversing valve 150 to the second configuration 170.

[0102] The cooling control sequence 344 may begin with block 346. At block 346, the second expansion device 124 (e.g., outdoor EEV) may be adjusted to a fully open position. In this way, working fluid discharged by the second heat exchanger 106 in the cooling mode of the heat pump 102 may flow through the second expansion device 124 with reduced and / or without inducing a pressure drop and / or flow restriction (e.g., throttling). In other words, the working fluid discharged from the second heat exchanger 106 may flow towards the receiver 190 in a liquid phase.

[0103] The cooling control sequence 344 may then proceed to block 348. At block 348, an actual superheat value (e.g., measured superheat value, calculated superheat value) of the working fluid exiting the first heat exchanger 104 may be compared to a superheat set point (e.g., superheat set point value) to determine whether the actual superheat value is less than the superheat set point. In some embodiments, the actual superheat value may be calculated by subtracting the saturation temperature of the working fluid within the first heat exchanger 104 from a measured temperature (e.g., actual temperature, measured via fourth sensor 240) of the working fluid exiting the first heat exchanger 104. The saturation temperature may be determined via detections or measurements (e.g., pressure measurement) of one or more sensors 230 located, for example, at an outlet of the first heat exchanger 104 (e.g., fourth sensor 240). Similarly, the temperature of the working fluid exiting the first heat exchanger 104 may be measured via detections or measurements of one or more sensors 230 also located, for example, at an outlet of the first heat exchanger 104 (e.g., fourth sensor 240). To this end, the controller 220 may be configured to receive data and / or feedback from one or more sensors 230 of the heat pump 102, such as working fluid pressure sensors (e.g., suction pressure sensor, discharge pressure sensor), an ambient temperature sensor, a working fluid temperature sensor, and / or other suitable sensor to determine (e.g., calculate) an actual superheat value of the working fluid exiting the first heat exchanger 104 in the cooling mode.

[0104] Further, in some embodiments, the superheat set point may be a predetermined set point stored in the memory device 224 of the controller 220. The heat pump 102 may have a predetermined superheat set point that may be based on one or more parameters of the heat pump and / or a configuration of the heat pump. For instance, the memory device 224 of the controller 220 may store different superheat set point values associated with the heating mode and the cooling mode of the heat pump 102 in a heating mode and a cooling mode. For example, in the cooling mode configuration illustrated in FIG. 6 and for which the cooling control sequence 344 of FIG. 11 may be executed, the superheat set point may be smaller than the superheat set point associated with for in a heating mode. Furthermore, the superheat set point may be based on one or more parameters of the heat pump 102, such as internal volumes of the first heat exchanger 104 and second heat exchangers 106. In other embodiments, the superheat set point may be calculated, selected, and / or otherwise determined (e.g., via the controller 220), such as based on an ambient temperature or another operating condition of the heat pump 102 (e.g., measured by one or more sensors 230.

[0105] In response to a determination that the actual superheat value is less than the superheat set point, the cooling control sequence 344 may proceed to block 352. At block 352, the first expansion device 122 (e.g., indoor EEV) may be controlled to adjust the actual superheat value the heat pump 102. For example, the controller 220 may control, adjust, or otherwise operate the first expansion device 122 to cause the actual superheat value of the working fluid to approach the superheat set point. To this end, one or more values of the superheat set point may be stored in the memory device 224 of the controller 220, and / or the controller 220 may receive feedback from one or more of the sensors 230 (e.g., temperature and / or pressure sensors disposed along the working fluid circuit 108) to determine whether adjustment of the first expansion device 122 is desired to achieve the superheat set point. As described above, by controlling the first expansion device 122 to increase the actual superheat value (e.g., by adjusting the first expansion device 122 towards a closed position), the liquid level 206 within the receiver 190 may be increased. Accordingly, the active charge of working fluid circulating through the working fluid circuit 108 may decrease. As such, by controlling the superheat set point, the controller 220 may also directly control the amount of charge in the working fluid circuit 108, which may enable more efficient operation of the heat pump 102 in the cooling mode.

[0106] Based on a determination that actual superheat value is greater than or equal to the superheat set point, the cooling control sequence 344 may proceed to block 354. At block 354, the first expansion device 122 (e.g., indoor EEV) may be controlled to adjust towards a fully open position. As will be appreciated, adjusting the first expansion device 122 towards the fully open position may increase the flow of working fluid into the first heat exchanger 104 and thereby decrease the actual superheat value of the working fluid. As a result the liquid level 206 of working fluid retained and / or stored in the receiver 190 may decrease and thereby increase the active charge of working fluid circulating through the working fluid circuit 108 may increase. In the manner described above, the controller 220 may control operation of the first expansion device 122 to adjust the actual superheat value of the working fluid exiting first heat exchanger 104 (e.g., toward a superheat set point value associated with the cooling mode) and thereby adjust an amount of working fluid retained within the receiver 190 to effectuate an adjustment to the active charge of working fluid circulated through the working fluid circuit 108 to increase the efficiency of the heat pump 102.

[0107] Referring back to block 346, after the controller 220 adjusts the second expansion device 124, the cooling control sequence 344 may proceed to block 350. In some embodiments, the cooling control sequence 344 may execute both blocks 348 and 350 simultaneously. At block 350, an actual subcooling value (e.g., measured subcooling value, calculated subcooling value) may be compared to a subcooling set point (e.g., subcooling set point value) to determine whether the actual subcooling value is less than the subcooling set point. In some embodiments, the actual subcooling value may be calculated by subtracting the saturation temperature of the working fluid within the second heat exchanger 106 from a measured temperature (e.g., actual temperature, measured via fifth sensor 242) of the working fluid exiting the second heat exchanger 106. The saturation temperature may be determined via detections or measurements (e.g., pressure measurement) of one or more sensors 230 located, for example, at an outlet of the second heat exchanger 106 (e.g., fifth sensor 242). Similarly, the temperature of the working fluid exiting the second heat exchanger 106 may be measured via detections or measurements of one or more sensors 230 also located, for example, at an outlet of the second heat exchanger 106 (e.g., fifth sensor 242). To this end, the controller 220 may be configured to receive data and / or feedback from one or more sensors 230 of the heat pump 102, such as working fluid pressure sensors (e.g., suction pressure sensor, discharge pressure sensor), an ambient temperature sensor, a working fluid temperature sensor, and / or other suitable sensors to determine (e.g., calculate) an actual subcooling value of the working fluid exiting at the second heat exchanger 106 in a cooling mode.

[0108] Further, in some embodiments, the subcooling set point may be a predetermined set point stored in the memory device 224 of the controller 220. The heat pump 102 may have a predetermined subcooling set point that may be based on one or more parameters of the heat pump 102 and / or a configuration of the heat pump 102. For instance, the memory device 224 of the controller 220 may store different subcooling set point values associated with the heating mode and the cooling mode of the heat pump 102. For example, in the cooling mode as illustrated in FIG. 6 and for which the cooling control sequence 344 of FIG. 11 may be executed, the subcooling set point may be greater than the subcooling set point associated with the heating mode. Furthermore, the subcooling set point may be based on one or more parameters of the heat pump 102, such as internal volumes of the first heat exchanger 104 and / or the second heat exchangers 106. In other embodiments, the subcooling set point may be calculated, selected, and / or otherwise determined (e.g., via the controller 220), such as based on an ambient temperature and / or operating another condition or the heat pump 102 (e.g., measured by one or more of the sensors 230).

[0109] In response to a determination that the actual subcooling value is less than a subcooling set point, the cooling control sequence 344 may proceed to block 356. At block 356, the second expansion device 124 (e.g., outdoor EEV) may be controlled to adjust subcooling value of the heat pump 102. For example, the controller 220 may control, adjust, or otherwise operate the second expansion device 124 to cause the actual subcooling value of the working fluid to approach the subcooling set point. To this end, one or more values of the subcooling set point may be stored in the memory device 224 of the controller 220, and / or the controller 220 may receive feedback from one or more of the sensors 230 (e.g., temperature and / or pressure sensors disposed along the working fluid circuit 108) to determine whether adjustment of the second expansion device 124 is desired to achieve the subcooling set point. In some embodiments, adjusting the second expansion device 124 to adjust the actual subcooling value may at least partially restrict flow of the working fluid leaving the second heat exchanger 106. As such, the working fluid in the second heat exchanger 106 may increase, and the residence time of the working fluid in the second heat exchanger 106 may increase, thereby causing an increase in the actual subcooling value due to an increased amount of working fluid in the second heat exchanger 106. In this way, the receiver 190 may experience a decrease in working fluid, thus decreasing the liquid level 206. Accordingly, the active charge of the working fluid circulating through the working fluid circuit 108 may increase, which may enable more efficient operation of the heat pump 102 in the cooling mode.

[0110] Based on a determination that actual subcooling value is greater than or equal to the subcooling set point, the cooling control sequence 344 may proceed to block 358. At block 358, the second expansion device 124 (e.g., outdoor EEV) may be maintained in the fully open position. As will be appreciated, adjusting the second expansion device 124 to a fully opened position may increase the flow of working fluid out of the second heat exchanger 106, decreasing the amount of working fluid in the second heat exchanger 106, and the residence time of the working fluid in the second heat exchanger 106. As such, the actual subcooling in the heat pump 102 may decrease. Further, the adjusting of the second expansion device 124 may result in the receiver 190 experiencing an increase in working fluid, thus increasing the liquid level 206. Accordingly, the active charge of the working fluid circulating through the working fluid circuit 108 may decrease, which may enable more efficient operation of the heat pump 102 in the cooling mode.

[0111] After blocks 352, 354, 356, and 358 the cooling control sequence 344 may proceed to block 316 to end the method 300. In some embodiments, after the control of the expansion devices 120 in blocks 352, 354, 356, and 358, the sequence may restart at blocks 348, and 350, creating an iterative sequence to adjust the expansion devices 120 to obtain the set point subcooling, the set point superheating, and a desired heat pump 102 charge in the working fluid circuit 108.

[0112] Further, it should be appreciated that other steps of the method 300 may be performed iteratively throughout an operating cycle of the heat pump 102. For example, in the heating mode, the steps of the heating control sequence 320 may be performed iteratively (e.g., based on updated data or feedback received from one or more sensors 230), such that the controller 220 may execute some or all blocks of the heating control sequence 320. Similarly, in the cooling mode, the steps of the cooling control sequence 344 may be performed iteratively (e.g., based on updated data or feedback received from one or more sensors 230), such that the controller 220 may execute some or all blocks of the cooling control sequence 344. In such embodiments, transition from different portions of the heating control sequence 320 and the cooling control sequence 344 may be regulated via reference to additional threshold values such as cut-in or cut-out threshold values to avoid repetitive, excessive, or otherwise undesirable transition between different operating modes and / or control sequences of the method 300.

[0113] As set forth above, embodiments of the present disclosure may provide one or more technical effects useful for regulating an active working fluid charge in a heat pump to enable more efficient operation of the heat pump in both a cooling mode and a heating mode of the heat pump. As a result, the present techniques enable utilization of heat pumps to operate with reduced energy consumption and reduced greenhouse gas emissions. It should be understood that the technical effects and technical problems in the specification are examples and are not limiting. Indeed, it should be noted that the embodiments described in the specification may have other technical effects and can solve other technical problems.

[0114] While only certain features and embodiments have been illustrated and described, many modifications and changes may occur to those skilled in the art, such as variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, such as temperatures and pressures, mounting arrangements, use of materials, colors, orientations, and so forth, without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the disclosure.

[0115] Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described, such as those unrelated to the presently contemplated best mode, or those unrelated to enablement. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.

[0116] The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function]…” or “step for [perform]ing [a function]…”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).

Examples

Embodiment Construction

[0019]One or more specific embodiments of the present disclosure will be described below. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers’ specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0020]When introducing elements of various embodiments o...

BACKGROUND

[0001] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

[0002] A heating, ventilation, and / or air conditioning (HVAC) system may be used to thermally regulate an environment, such as a space within a building, home, or other structure. HVAC systems generally include a vapor compression system having heat exchangers, such as a condenser and an evaporator, which transfer thermal energy between the HVAC system and the environment. Typically, a compressor is fluidly coupled to a working fluid circuit of the vapor compression system and is configured to circulate a working fluid (e.g., refrigerant) between the heat exchangers. In this way, the compressor facilitates heat exchange between the working fluid, the heat exchangers, and other fluids directed across and / or through the heat exchangers. In some cases, the HVAC system may be a heat pump configured to enable reversal of working fluid flow through the working fluid circuit. As such, the heat pump enables the working fluid circuit to operate in a cooling mode and in a heating mode Accordingly, the HVAC system may operate in multiple operating modes (e.g., cooling mode, heating mode) to provide both heating and cooling to the building with one working fluid circuit. Unfortunately, a desired amount of working fluid circulated in the working fluid circuit (e.g., charge) is usually different in the cooling mode and heating mode, thereby resulting in inefficiencies in one mode or the other for traditional systems.SUMMARY

[0003] A summary of certain embodiments disclosed herein is set forth below. It should be noted that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.

[0004] In an embodiment, an energy efficient heat pump for a heating, ventilation, and air conditioning (HVAC) system, includes a working fluid circuit that may circulate a working fluid therethrough, where the working fluid circuit includes a first heat exchanger that may transfer heat between the working fluid and a supply air flow, and a second heat exchanger that may transfer heat between the working fluid and an ambient air flow. The heat pump further including a first expansion device, a second expansion device and a liquid conduit portion of the working fluid circuit extending between the first heat exchanger and the second heat exchanger, where the first expansion device and the second expansion device are disposed along the liquid conduit portion. The heat pump also including a receiver disposed along the liquid conduit portion of the working fluid circuit between the first expansion device and the second expansion device, where the receiver includes a vessel to retain an amount of the working fluid therein. The heat pump also including a controller communicatively coupled to the first expansion device and the second expansion device, where the controller may adjust the first expansion device, the second expansion device, or both to adjust the amount of the working fluid retained within the vessel of the receiver.

[0005] In another embodiment, an energy efficient heat pump for a heating, ventilation, and air conditioning (HVAC) system, includes a working fluid circuit including a liquid conduit portion that may direct a working fluid between a first heat exchanger of the working fluid circuit and a second heat exchanger of the working fluid circuit. The heat pump also including a receiver disposed along the liquid conduit portion, where the receiver includes a vessel, a first dip tube fluidly coupled to the liquid conduit portion and extending into the vessel, and a second dip tube fluidly coupled to the liquid conduit portion and extending into the vessel, where the first dip tube and the second dip tube may each direct the working fluid from the liquid conduit portion and into the vessel and to direct the working fluid from the vessel to the liquid conduit portion. The heat pump also including a first expansion device disposed along the liquid conduit portion between the first heat exchanger and the receiver, a second expansion device disposed along the liquid conduit portion between the second heat exchanger and the receiver, and a controller communicatively coupled to the first expansion device and the second expansion device. The controller may adjust the first expansion device and the second expansion device based on an operating mode of the energy efficient heat pump and based on at least one operating parameter of the working fluid, where the controller may regulate an amount of working fluid retained within the vessel of the receiver.

[0006] In a further embodiment, an energy efficient heat pump includes a working fluid circuit that may circulate a working fluid therethrough, a first heat exchanger disposed along the working fluid circuit and operable to transfer heat between the working fluid and a supply air flow in a heating mode and in a cooling mode of the energy efficient heat pump. The heat pump also including a second heat exchanger disposed along the working fluid circuit and operable to transfer heat between the working fluid and an ambient air flow in the heating mode and the cooling mode and a liquid conduit portion of the working fluid circuit extending between the first heat exchanger and the second heat exchanger. The heat pump also including a receiver disposed along the liquid conduit portion, where the receiver includes a vessel, a first dip tube fluidly coupled to the liquid conduit portion and extending into the vessel, and a second dip tube fluidly coupled to the liquid conduit portion and extending into the vessel a first electronic expansion valve disposed along the liquid conduit portion between the first heat exchanger and the first dip tube. The heat pump further including a second electronic expansion valve disposed along the liquid conduit portion between the second heat exchanger and the second dip tube and a controller communicatively coupled to the first electronic expansion valve and the second electronic expansion valve. The controller may adjust the first electronic expansion valve and the second electronic expansion valve based on data indicative of an amount of subcooling of the working fluid and data indicative of an amount of superheat of the working fluid to adjust an amount of the working fluid retained within the vessel in the heating mode and in the cooling mode.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which:

[0008] FIG. 1 is a perspective view of an embodiment of a building incorporating a heating, ventilation, and / or air conditioning (HVAC) system in a commercial setting, in accordance with an aspect of the present disclosure;

[0009] FIG. 2 is a perspective view of an embodiment of a packaged HVAC unit, in accordance with an aspect of the present disclosure;

[0010] FIG. 3 is a perspective view of an embodiment of a split, residential HVAC system, in accordance with an aspect of the present disclosure;

[0011] FIG. 4 is a schematic diagram of an embodiment of a vapor compression system used in an HVAC system, in accordance with an aspect of the present disclosure;

[0012] FIG. 5 is a schematic diagram of an embodiment of a portion of an HVAC system including a heat pump system having a receiver and a controller, in accordance with an aspect of the present disclosure;

[0013] FIG. 6 is a schematic diagram of an embodiment of a portion of an HVAC system including a heat pump system having a receiver and a controller, in accordance with an aspect of the present disclosure;

[0014] FIG. 7 is a schematic diagram of an embodiment of a portion of an HVAC system including a heat pump system having a receiver and a controller, in accordance with an aspect of the present disclosure;

[0015] FIG. 8 is a schematic diagram of an embodiment of a portion of an HVAC system including a heat pump system having a receiver and a controller, in accordance with an aspect of the present disclosure;

[0016] FIG. 9 is a flow chart of an embodiment of a method for controlling operation of a heat pump system of an HVAC system, in accordance with an aspect of the present disclosure;

[0017] FIG. 10 is a flow chart of an embodiment of a heating control sequence of a method for controlling operation of a heat pump system of an HVAC system, in accordance with an aspect of the present disclosure; and

[0018] FIG. 11 is a flow chart of an embodiment of a cooling control sequence of a method for controlling operation of a heat pump system of an HVAC system, in accordance with an aspect of the present disclosure.DETAILED DESCRIPTION

[0019] One or more specific embodiments of the present disclosure will be described below. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers’ specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0020] When introducing elements of various embodiments of the present disclosure, the articles “a,”“an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0021] As used herein, the terms “approximately,”“generally,” and “substantially,” and so forth, are intended to convey that the property value being described may be within a relatively small range of the property value, as those of ordinary skill would understand. For example, when a property value is described as being “approximately” equal to (or, for example, “substantially similar” to) a given value, this is intended to mean that the property value may be within + / - 5%, within + / - 4%, within + / - 3%, within + / - 2%, within + / - 1%, or even closer, of the given value. Similarly, when a given feature is described as being “substantially parallel” to another feature, “generally perpendicular” to another feature, and so forth, this is intended to mean that the given feature is within + / - 5%, within + / - 4%, within + / - 3%, within + / - 2%, within + / - 1%, or even closer, to having the described nature, such as being parallel to another feature, being perpendicular to another feature, and so forth. Further, it should be understood that mathematical terms, such as “planar,”“slope,”“perpendicular,”“parallel,” and so forth are intended to encompass features of surfaces or elements as understood to one of ordinary skill in the relevant art, and should not be rigidly interpreted as might be understood in the mathematical arts. For example, a “planar” surface is intended to encompass a surface that is machined, molded, or otherwise formed to be substantially flat or smooth (within related tolerances) using techniques and tools available to one of ordinary skill in the art. Similarly, a surface having a “slope” is intended to encompass a surface that is machined, molded, or otherwise formed to be oriented at an angle (e.g., incline) with respect to a point of reference using techniques and tools available to one of ordinary skill in the art.

[0022] As briefly discussed above, a heating, ventilation, and / or air conditioning (HVAC) system may be used to thermally regulate a space within a building, home, or other suitable structure. For example, the HVAC system may include a vapor compression system that transfers thermal energy between a working fluid, such as a refrigerant, and a fluid to be conditioned, such as air. The vapor compression system includes heat exchangers, such as a condenser and an evaporator, which are fluidly coupled to one another via one or more conduits of a working fluid loop or circuit. A compressor may be used to circulate the working fluid through the conduits and other components of the working fluid circuit (e.g., an expansion device) and, thus, enable the transfer of thermal energy between components of the working fluid circuit (e.g., between the condenser and the evaporator) and one or more thermal loads (e.g., an environmental air flow, a supply air flow). Additionally or alternatively, the HVAC system may include a heat pump (e.g., a heat pump system) having a first heat exchanger (e.g., a heating and / or cooling coil, an indoor coil, the evaporator) fluidly coupled to the space to be conditioned, a second heat exchanger (e.g., a heating and / or cooling coil, an outdoor coil, the condenser) positioned in or otherwise fluidly coupled to an ambient environment (e.g., the atmosphere), and a pump (e.g., compressor) configured to circulate the working fluid (e.g., refrigerant) between the first and second heat exchangers to enable heat transfer between the space to be conditioned and the ambient environment, for example.

[0023] The heat pump may be operable to provide both cooling and heating to the space to be conditioned (e.g., a room, zone, or other region within a building) by adjusting a flow of the working fluid through the working fluid circuit. Thus, the heat pump may not include a dedicated heating system, such as a furnace or burner configured to combust a fuel, to enable operation of the HVAC system in the heating mode. As a result, the heat pump is configured to operate with reduced greenhouse gas emissions. For example, during operation of the heat pump in a cooling mode, the compressor may direct working fluid through the working fluid circuit and the first and second heat exchangers in a first flow direction. While receiving working fluid in the first flow direction, the first heat exchanger, which may be fluidly coupled to the space to be conditioned, may operate as an evaporator and, thus, enable working fluid flowing through the first heat exchanger to absorb thermal energy from an air flow directed to the space. Further, the second heat exchanger, which may be positioned in the ambient environment surrounding the heat pump, may operate as a condenser to reject the heat absorbed by the working fluid flowing from the first heat exchanger (e.g., to an ambient air flow directed across the second heat exchanger). In this way, the heat pump may facilitate cooling of the space or other thermal load serviced by (e.g., in thermal communication with) the first heat exchanger.

[0024] Conversely, during operation in a heating mode, a reversing valve (e.g., a switch-over valve) enables the compressor to direct working fluid through the working fluid circuit and the first and second heat exchangers in a second flow direction, opposite the first flow direction. While receiving working fluid in the second flow direction, the first heat exchanger may operate as a condenser instead of an evaporator, and the second heat exchanger may operate as an evaporator instead of a condenser. As such, the first heat exchanger may receive (e.g., from the second heat exchanger) a flow of heated working fluid to reject heat to a thermal load serviced by the first heat exchanger (e.g., an air flow directed to the space) and, thus, facilitate heating of the thermal load. In this way, the heat pump may facilitate either heating or cooling of the thermal load based on a selected operating mode of the heat pump (e.g., based on a flow direction of working fluid along the working fluid circuit).

[0025] Unfortunately, HVAC systems may be susceptible to operational inefficiencies in certain conditions or circumstances. As an example, an amount of working fluid circulated through the working fluid circuit may be ill-suited and / or inefficient for certain HVAC system and / or heat pump operations. In other words, a desired amount of working fluid circulated through the heat pump (e.g., charge) may be different in the cooling mode and in the heating mode, thereby resulting in inefficiencies in one mode or the other for heat pumps configured to operate with a fixed amount of working fluid directed through the working fluid circuit. In many heat pump configurations, there are differences in internal volumes between the indoor heat exchanger and outdoor heat exchanger (e.g., first heat exchanger and second heat exchanger). For example, the indoor heat exchanger (e.g., first heat exchanger) may have an internal volume that is less than the internal volume of the outdoor heat exchanger. As such, when a reversible heat pump changes modes (e.g., from a heating mode to a cooling mode or vice versa), and the heat exchangers switch functions (e.g., evaporator to condenser or vice versa) the desirable charge in the heat pump may change. In most heat pumps, the total amount of working fluid remains constant, as it would be undesirable and / or inefficient to add or reduce the working fluid in a system. As such, methods of controlling the amount of working fluid (e.g., charge) in the heat pump are desirable.

[0026] Conventional approaches to address such shortcomings with heat pumps are typically expensive and complicated. Conventional approaches may also be associated with increased energy consumption and generation of greenhouse gas emissions. For example, a compensator may be included in the heat pump and may be configured to enable control of an amount of working fluid circulating in the working fluid circuit. For example, the compensator may be configured to retain a portion of working fluid therein during the heating mode of the heat pump, such that the portion of retained working fluid does not circulate through the working fluid circuit, to improve operation of the heat pump in the heating mode. However, efficiency improvements provided by compensators may be limited.

[0027] Accordingly, embodiments of the present disclosure relate to a heat pump that is configured to enable more efficient operation and enable a reduction in the generation of greenhouse gas emissions. For example, present embodiments include heat pumps configured to regulate a charge or amount of working fluid circulated through the working fluid circuit to enable more efficient operation of the heat pump in both a heating mode and a cooling mode. In this way, the present techniques enable a reduction in energy consumption and a reduction in greenhouse gas emissions. As discussed in detail below, the heat pump (e.g., heat pump system, a reverse-cycle heat pump system, an air-source heat pump system, reverse cycle air conditioner) may include a receiver positioned between the first heat exchanger and the second heat exchanger that is configured to receive and store an amount of working fluid from the working fluid circuit based on an operating mode of the heat pump, a parameter of the heat pump, or both. In other words, the receiver may store the amount of working fluid, such that the amount of working fluid is not circulated through the working fluid circuit. For example, in a heating mode, when a lower charge of working fluid within the working fluid circuit is desired, the receiver may receive and store an increased amount of working fluid, thereby decreasing the total charge of working fluid in the working fluid circuit. Further, in a cooling mode, when a higher charge of working fluid within the working fluid circuit is desired, the receiver may receive and store a decreased amount of working fluid, thereby increasing the total charge working fluid in the working fluid circuit. In this way, the heat pump may operate with increased efficiency in both the heating mode and the cooling mode.

[0028] The amount of working fluid directed into and stored within the receiver may be adjusted via control of other components of the heat pump. Accordingly, embodiments of the present disclosure also include an improved control system configured to regulate operation of the heat pump and the components of the heat pump. In accordance with present techniques, the control system may regulate operation of expansion devices (e.g., expansion valves, electronic expansion valves, electronic expansion devices) of the heat pump to enable more efficient operation (e.g., reduced energy consumption). For example, the control system may control operation of the expansion devices of the heat pump based on an operating mode of the heat pump, based on operating conditions or parameters of the heat pump, and / or additional variables. For example, the control system may be configured to operate one or more expansion devices to obtain a desired amount of superheating or subcooling of the working fluid in the heat pump. Based on the control of the one or more expansion devices, an amount or volume of working fluid retained within the receiver may be adjusted (e.g., working fluid added to receiver, working fluid removed from receiver). In this way, present embodiments enable more efficient operation of the heat pump in both heating and cooling modes by regulating the amount of working fluid charge (e.g., active charge) in the working fluid circuit. Indeed, the present embodiments provide energy efficient heat pumps configured to operate and satisfy heating demands in cold and warm climate conditions with reduced energy consumption, thereby enabling a reduction of greenhouse gas emissions.

[0029] Turning now to the drawings, FIG. 1 illustrates an embodiment of a heating, ventilation, and / or air conditioning (HVAC) system for environmental management that employs one or more HVAC units in accordance with the present disclosure. As used herein, an HVAC system includes any number of components configured to enable regulation of parameters related to climate characteristics, such as temperature, humidity, air flow, pressure, air quality, and so forth. For example, an “HVAC system” as used herein is defined as conventionally understood and as further described herein. Components or parts of an “HVAC system” may include, but are not limited to, all, some of, or individual parts such as a heat exchanger, a heater, an air flow control device, such as a fan, a sensor configured to detect a climate characteristic or operating parameter, a filter, a control device configured to regulate operation of an HVAC system component, a component configured to enable regulation of climate characteristics, or a combination thereof. An “HVAC system” is a system configured to provide such functions as heating, cooling, ventilation, dehumidification, pressurization, refrigeration, filtration, or any combination thereof. The embodiments described herein may be utilized in a variety of applications to control climate characteristics, such as residential, commercial, industrial, transportation, or other applications where climate control is desired.

[0030] In the illustrated embodiment, a building 10 is air conditioned by a system that includes an HVAC unit 12 with a reheat system in accordance with present embodiments. The building 10 may be a commercial structure or a residential structure. As shown, the HVAC unit 12 is disposed on the roof of the building 10; however, the HVAC unit 12 may be located in other equipment rooms or areas adjacent the building 10. The HVAC unit 12 may be a single package unit containing other equipment, such as a blower, integrated air handler, and / or auxiliary heating unit. In other embodiments, the HVAC unit 12 may be part of a split HVAC system, such as the system shown in FIG. 3, which includes an outdoor HVAC unit 58 and an indoor HVAC unit 56.

[0031] The HVAC unit 12 is an air cooled device that implements a refrigeration cycle to provide conditioned air to the building 10. Specifically, the HVAC unit 12 may include one or more heat exchangers across which an air flow is passed to condition the air flow before the air flow is supplied to the building. In the illustrated embodiment, the HVAC unit 12 is a rooftop unit (RTU) that conditions a supply air stream, such as environmental air and / or a return air flow from the building 10. After the HVAC unit 12 conditions the air, the air is supplied to the building 10 via ductwork 14 extending throughout the building 10 from the HVAC unit 12. For example, the ductwork 14 may extend to various individual floors or other sections of the building 10. In certain embodiments, the HVAC unit 12 may be a heat pump that provides both heating and cooling to the building with one working fluid circuit configured to operate in different modes. In other embodiments, the HVAC unit 12 may include one or more working fluid circuits for cooling an air stream and a furnace for heating the air stream.

[0032] A control device 16, one type of which may be a thermostat, may be used to designate the temperature of the conditioned air. The control device 16 also may be used to control the flow of air through the ductwork 14. For example, the control device 16 may be used to regulate operation of one or more components of the HVAC unit 12 or other components, such as dampers and fans, within the building 10 that may control flow of air through and / or from the ductwork 14. In some embodiments, other devices may be included in the system, such as pressure and / or temperature transducers or switches that sense the temperatures and pressures of the supply air, return air, and so forth. Moreover, the control device 16 may include computer systems that are integrated with or separate from other building control or monitoring systems, and even systems that are remote from the building 10.

[0033] FIG. 2 is a perspective view of an embodiment of the HVAC unit 12. In the illustrated embodiment, the HVAC unit 12 is a single package unit that may include one or more independent vapor compression circuits and components that are tested, charged, wired, piped, and ready for installation. The HVAC unit 12 may provide a variety of heating and / or cooling functions, such as cooling only, heating only, cooling with electric heat, cooling with dehumidification, cooling with gas heat, or cooling with a heat pump. As described above, the HVAC unit 12 may directly cool and / or heat an air stream provided to the building 10 to condition a space in the building 10.

[0034] As shown in the illustrated embodiment of FIG. 2, a cabinet 24 encloses the HVAC unit 12 and provides structural support and protection to the internal components from environmental and other contaminants. In some embodiments, the cabinet 24 may be constructed of galvanized steel and insulated with aluminum foil faced insulation. Rails 26 may be joined to the bottom perimeter of the cabinet 24 and provide a foundation for the HVAC unit 12. In certain embodiments, the rails 26 may provide access for a forklift and / or overhead rigging to facilitate installation and / or removal of the HVAC unit 12. In some embodiments, the rails 26 may fit into “curbs” on the roof to enable the HVAC unit 12 to provide air to the ductwork 14 from the bottom of the HVAC unit 12 while blocking elements such as rain from leaking into the building 10.

[0035] The HVAC unit 12 includes heat exchangers 28 and 30 in fluid communication with one or more vapor compression circuits. Tubes within the heat exchangers 28 and 30 may circulate a working fluid (e.g., a refrigerant), such as R-410A, R-407, R-134a, R-1234ze, R1233zd, R-32, hydrofluoro olefin (HFO), “natural” refrigerants like ammonia (NH3), R-717, carbon dioxide (CO2), R-744, or hydrocarbon based refrigerants, water vapor, or any other suitable working fluid through the heat exchangers 28 and 30. The tubes may be of various types, such as multichannel tubes, conventional copper or aluminum tubing, and so forth. Together, the heat exchangers 28 and 30 may implement a thermal cycle in which the working fluid undergoes phase changes and / or temperature changes as it flows through the heat exchangers 28 and 30 to produce heated and / or cooled air. For example, the heat exchanger 28 may function as a condenser where heat is released from the working fluid to ambient air, and the heat exchanger 30 may function as an evaporator where the working fluid absorbs heat to cool an air stream. In other embodiments, the HVAC unit 12 may operate in a heat pump mode where the roles of the heat exchangers 28 and 30 may be reversed. That is, the heat exchanger 28 may function as an evaporator and the heat exchanger 30 may function as a condenser. In further embodiments, the HVAC unit 12 may include a furnace for heating the air stream that is supplied to the building 10. While the illustrated embodiment of FIG. 2 shows the HVAC unit 12 having two of the heat exchangers 28 and 30, in other embodiments, the HVAC unit 12 may include one heat exchanger or more than two heat exchangers.

[0036] The heat exchanger 30 is located within a compartment 31 that separates the heat exchanger 30 from the heat exchanger 28. Fans 32 draw air from the environment through the heat exchanger 28. Air may be heated and / or cooled as the air flows through the heat exchanger 28 before being released back to the environment surrounding the HVAC unit 12. A blower assembly 34, powered by a motor 36, draws air through the heat exchanger 30 to heat or cool the air. The heated or cooled air may be directed to the building 10 by the ductwork 14, which may be connected to the HVAC unit 12. Before flowing through the heat exchanger 30, the conditioned air flows through one or more filters 38 that may remove particulates and contaminants from the air. In certain embodiments, the filters 38 may be disposed on the air intake side of the heat exchanger 30 to prevent contaminants from contacting the heat exchanger 30.

[0037] The HVAC unit 12 also may include other equipment for implementing the thermal cycle. Compressors 42 increase the pressure and temperature of the working fluid before the working fluid enters the heat exchanger 28. The compressors 42 may be any suitable type of compressors, such as scroll compressors, rotary compressors, screw compressors, or reciprocating compressors. In some embodiments, the compressors 42 may include a pair of hermetic direct drive compressors arranged in a dual stage configuration 44. However, in other embodiments, any number of the compressors 42 may be provided to achieve various stages of heating and / or cooling. As may be appreciated, additional equipment and devices may be included in the HVAC unit 12, such as a solid-core filter drier, a drain pan, a disconnect switch, an economizer, pressure switches, phase monitors, and humidity sensors, among other things.

[0038] The HVAC unit 12 may receive power through a terminal block 46. For example, a high voltage power source may be connected to the terminal block 46 to power the equipment. The operation of the HVAC unit 12 may be governed or regulated by a control board 48. The control board 48 may include control circuitry connected to a thermostat, sensors, and alarms. One or more of these components may be referred to herein separately or collectively as the control device 16. The control circuitry may be configured to control operation of the equipment, provide alarms, and monitor safety switches. Wiring 49 may connect the control board 48 and the terminal block 46 to the equipment of the HVAC unit 12.

[0039] FIG. 3 illustrates a residential heating and cooling system 50, also in accordance with present techniques. The residential heating and cooling system 50 may provide heated and cooled air to a residential structure, as well as provide outside air for ventilation and provide improved indoor air quality (IAQ) through devices such as ultraviolet lights and air filters. In the illustrated embodiment, the residential heating and cooling system 50 is a split HVAC system. In general, a residence 52 conditioned by a split HVAC system may include working fluid conduits 54 that operatively couple the indoor unit 56 to the outdoor unit 58. The indoor unit56 may be positioned in a utility room, an attic, a basement, and so forth. The outdoor unit 58 is typically situated adjacent to a side of residence 52 and is covered by a shroud to protect the system components and to prevent leaves and other debris or contaminants from entering the unit. The working fluid conduits 54 transfer working fluid between the indoor unit 56 and the outdoor unit 58, typically transferring primarily liquid working fluid in one direction and primarily vaporized working fluid in an opposite direction.

[0040] When the system shown in FIG. 3 is operating as an air conditioner, a heat exchanger 60 in the outdoor unit 58 serves as a condenser for re-condensing vaporized working fluid flowing from the indoor unit 56 to the outdoor unit 58 via one of the working fluid conduits 54. In these applications, a heat exchanger 62 of the indoor unit functions as an evaporator. Specifically, the heat exchanger 62 receives liquid working fluid, which may be expanded by an expansion device, and evaporates the working fluid before returning it to the outdoor unit 58.

[0041] The outdoor unit 58 draws environmental air through the heat exchanger 60 using a fan 64 and expels the air above the outdoor unit 58. When operating as an air conditioner, the air is heated by the heat exchanger 60 within the outdoor unit 58 and exits the unit at a temperature higher than it entered. The indoor unit 56 includes a blower or fan 66 that directs air through or across the indoor heat exchanger 62, where the air is cooled when the system is operating in air conditioning mode. Thereafter, the air is passed through ductwork 68 that directs the air to the residence 52. The overall system operates to maintain a desired temperature as set by a system controller. When the temperature sensed inside the residence 52 is higher than the set point on the thermostat, or the set point plus a small amount, the residential heating and cooling system 50 may become operative to refrigerate additional air for circulation through the residence 52. When the temperature reaches the set point, or the set point minus a small amount, the residential heating and cooling system 50 may stop the refrigeration cycle temporarily. The outdoor unit 58 includes a reheat system in accordance with present embodiments.

[0042] The residential heating and cooling system 50 may also operate as a heat pump. When operating as a heat pump, the roles of heat exchangers 60 and 62 are reversed. That is, the heat exchanger 60 of the outdoor unit 58 will serve as an evaporator to evaporate working fluid and thereby cool air entering the outdoor unit 58 as the air passes over the outdoor heat exchanger 60. The indoor heat exchanger 62 will receive a stream of air blown over it and will heat the air by condensing the working fluid.

[0043] In some embodiments, the indoor unit 56 may include a furnace system 70. For example, the indoor unit 56 may include the furnace system 70 when the residential heating and cooling system 50 is not configured to operate as a heat pump. The furnace system 70 may include a burner assembly and heat exchanger, among other components, inside the indoor unit 56. Fuel is provided to the burner assembly of the furnace system 70 where it is mixed with air and combusted to form a heat transfer fluid. The heat transfer fluid may pass through tubes or piping in a heat exchanger, separate from heat exchanger 62, such that air directed by the blower 66 passes over the tubes or pipes and extracts heat from the heat transfer fluid. The heated air may then be routed from the furnace system 70 to the ductwork 68 for heating the residence 52.

[0044] FIG. 4 is an embodiment of a vapor compression system 72 that can be used in any of the systems described above. The vapor compression system 72 may circulate a working fluid through a circuit starting with a compressor 74. The circuit may also include a condenser 76, an expansion valve(s) or device(s) 78, and an evaporator 80. The vapor compression system 72 may further include a control panel 82 that has an analog to digital (A / D) converter 84, a microprocessor 86, a non-volatile memory 88, and / or an interface board 90. The control panel 82 and its components may function to regulate operation of the vapor compression system 72 based on feedback from an operator, from sensors of the vapor compression system 72 that detect operating conditions, and so forth.

[0045] In some embodiments, the vapor compression system 72 may use one or more of a variable speed drive (VSDs) 92, a motor 94, the compressor 74, the condenser 76, the expansion valve or device 78, and / or the evaporator 80. The motor 94 may drive the compressor 74 and may be powered by the variable speed drive (VSD) 92. The VSD 92 receives alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source, and provides power having a variable voltage and frequency to the motor 94. In other embodiments, the motor 94 may be powered directly from an AC or direct current (DC) power source. The motor 94 may include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source, such as a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor, or another suitable motor.

[0046] The compressor 74 compresses a working fluid vapor and delivers the vapor to the condenser 76 through a discharge passage. In some embodiments, the compressor 74 may be a centrifugal compressor. The working fluid vapor delivered by the compressor 74 to the condenser 76 may transfer heat to a fluid passing across the condenser 76, such as ambient or environmental air 96. The working fluid vapor may condense to a working fluid liquid in the condenser 76 as a result of thermal heat transfer with the environmental air 96. The liquid working fluid from the condenser 76 may flow through the expansion device 78 to the evaporator 80.

[0047] The liquid working fluid delivered to the evaporator 80 may absorb heat from another air stream, such as a supply air stream 98 provided to the building 10 or the residence 52. For example, the supply air stream 98 may include ambient or environmental air, return air from a building, or a combination of the two. The liquid working fluid in the evaporator 80 may undergo a phase change from the liquid working fluid to a working fluid vapor. In this manner, the evaporator 80 may reduce the temperature of the supply air stream 98 via thermal heat transfer with the working fluid. Thereafter, the vapor working fluid exits the evaporator 80 and returns to the compressor 74 by a suction line to complete the cycle.

[0048] In some embodiments, the vapor compression system 72 may further include a reheat coil. In the illustrated embodiment, the reheat coil is represented as part of the evaporator 80. The reheat coil is positioned downstream of the evaporator heat exchanger relative to the supply air stream 98 and may reheat the supply air stream 98 when the supply air stream 98 is overcooled to remove humidity from the supply air stream 98 before the supply air stream 98 is directed to the building 10 or the residence 52.

[0049] It should be appreciated that any of the features described herein may be incorporated with the HVAC unit 12, the residential heating and cooling system 50, or other HVAC systems. Additionally, while the features disclosed herein are described in the context of embodiments that directly heat and cool a supply air stream provided to a building or other load, embodiments of the present disclosure may be applicable to other HVAC systems as well. For example, the features described herein may be applied to mechanical cooling systems, free cooling systems, chiller systems, or other heat pump or refrigeration applications.

[0050] To provide context for the following discussion, FIG. 5 is a schematic of an embodiment of a portion of an HVAC system 100 that includes a heat pump 102 (e.g., a heat pump system, reverse cycle heat pump, air source heat pump, energy efficient heat pump) in accordance with present embodiments. The heat pump 102 may include one or more components of the vapor compression system 72 discussed above and / or may be included in any of the systems described above (e.g., HVAC unit 12, heating and cooling system 50). The heat pump 102 includes a first heat exchanger 104 (e.g., indoor heat exchanger) and a second heat exchanger 106 (e.g., outdoor heat exchanger) that are fluidly coupled to one another via a working fluid circuit 108 or working fluid loop (e.g., one or more conduits, refrigerant circuit). The first heat exchanger 104 may be in thermal communication with (e.g., fluidly coupled to) a thermal load 110 (e.g., a room, space, and / or device) serviced by the heat pump 102, and the second heat exchanger 106 may be in thermal communication with an ambient environment 112 (e.g., the atmosphere) surrounding the HVAC system 100.

[0051] In some embodiments, a first fan 116 (e.g., blower) may direct a first air flow across the first heat exchanger 104 to facilitate heat exchange between working fluid within the first heat exchanger 104 and the thermal load 110, while a second fan 118 may direct a second air flow across the second heat exchanger 106 to facilitate heat exchange between working fluid within the second heat exchanger 106 and the ambient environment 112. One or more expansion devices 120 (e.g., electronic expansion valve [EEV], bi-directional expansion valve) may be disposed along the working fluid circuit 108 between the first heat exchanger 104 and the second heat exchanger 106 and may be configured to regulate (e.g., throttle) a flow of working fluid and / or a working fluid pressure differential between the first heat exchanger 104 and the second heat exchanger 106. In the illustrated embodiment, the working fluid circuit 108 includes a first expansion device 122 (e.g., expansion valve, indoor expansion device, EEV) disposed along the working fluid circuit 108 proximate the first heat exchanger 104 and a second expansion device 124 (e.g., expansion valve, outdoor expansion device, EEV) disposed along the working fluid circuit 108 proximate the second heat exchanger 106. However, in some embodiments the heat pump 102 may include one expansion device 120 (e.g., either the first expansion device 122 or the second expansion device 124).

[0052] The heat pump 102 also includes a compressor 130 (e.g., compressor system) disposed along the working fluid circuit 108. The compressor 130 is configured to direct working fluid flow through the working fluid circuit 108 and therefore through components disposed along the working fluid circuit 108, such as the first heat exchanger 104, the second heat exchanger 106, the expansion device(s) 120, and so forth. Although one compressor 130 is shown in the illustrated embodiment, the heat pump 102 may include any suitable quantity of compressors 130, such as two, three, four, five, six, or more than six compressors 130. The compressor 130 may be a multi-stage (e.g., two stage) compressor and / or a variable speed compressor. Additionally, the compressor 130 may be a high-side shell compressor, a rotary compressor, a scroll compressor, and / or any other suitable type of compressor. The compressor 130 is configured to receive working fluid (e.g., a primary flow of working fluid) via a suction conduit 132 fluidly coupled to a suction port 134 of the compressor 130 and to discharge working fluid (e.g., compressed working fluid) via a discharge conduit 136 fluidly coupled to a discharge port 138 of the compressor 130.

[0053] The compressor 130 may be fluidly coupled to a remainder of the working fluid circuit 108 via a reversing valve 150 (e.g., a switch-over valve). In the illustrated embodiment, the reversing valve 150 includes a first port 152 that is fluidly coupled to the suction conduit 132, a second port 154 that is fluidly coupled to the discharge conduit 136, a third port 156 that is fluidly coupled to a first conduit portion 158 extending to the first heat exchanger 104, and a fourth port 160 that is fluidly coupled to a second conduit portion 162 extending to the second heat exchanger 106.

[0054] The reversing valve 150 is configured to transition between a first configuration 164, in which the reversing valve 150 fluidly couples the first port 152 and the fourth port 160 and fluidly couples the second port 154 and the third port 156, and a second configuration 170, illustrated in FIG. 6, in which the reversing valve 150 fluidly couples the first port 152 and the third port 156 and fluidly couples the second port 154 and the fourth port 160. Accordingly, in the first configuration 164, the reversing valve 150 enables the compressor 130 to receive a flow of working fluid from the second heat exchanger 106 and to discharge a flow of working fluid to the first heat exchanger 104. Conversely, in the second configuration 170, the reversing valve 150 enables the compressor 130 to receive a flow of working fluid from the first heat exchanger 104 and to discharge a flow of working fluid to the second heat exchanger 106. In this way, while in the first configuration 164, the reversing valve 150 enables the heat pump 102 to operate in a heating mode, in which the first heat exchanger 104 rejects thermal energy to the thermal load 110 to heat the thermal load 110, and the second heat exchanger 106 absorbs thermal energy from the ambient environment 112. Further, while in the second configuration 170, the reversing valve 150 enables the heat pump 102 to operate in a cooling mode, in which the first heat exchanger 104 absorbs thermal energy from the thermal load 110 to cool the thermal load 110, and the second heat exchanger 106 rejects the absorbed thermal energy (e.g., absorbed from the thermal load 110) to the ambient environment 112. As such, while the reversing valve 150 is in the first configuration 164, the compressor 130 may direct a working fluid flow along at least a portion of the working fluid circuit 108 in a first flow direction 172. While the reversing valve 150 is in the second configuration 170, the compressor 130 may direct a working fluid flow along at least a portion of the working fluid circuit 108 in a second flow direction 174, opposite the first flow direction 172. For clarity, the heat pump 102 (e.g., energy efficient heat pump) is shown configured for operation in a heating mode in the illustrated embodiment of FIG. 5, and FIG. 6 is a schematic of an embodiment of a portion of the HVAC system 100 illustrating the heat pump 102 (e.g., energy efficient heat pump) configured for operation in a cooling mode.

[0055] The present discussion continues with reference to FIG. 5. The heat pump 102 may also include additional components, such as an accumulator 180 disposed along the working fluid circuit 108. More specifically, the accumulator 180 is disposed along the suction conduit 132 extending between the reversing valve 150 (e.g., the first port 152) and the suction port 134 of the compressor 130. In general, the accumulator 180 is configured to block flow of liquid working fluid to the compressor 130. In some instances and / or operating conditions, a portion of the working fluid directed from the reversing valve 150 and along the suction conduit 132 may be in a liquid phase. Accordingly, the accumulator 180 is configured to receive the flow of working fluid (e.g., two-phase working fluid) and to separate any liquid working fluid from vapor working fluid. The accumulator 180 may retain liquid working fluid therein and may output vapor or gaseous working fluid to flow to the compressor 130. In this way, flow of liquid working fluid to the compressor 130 may be avoided to protect the compressor 130 from wear and degradation.

[0056] In accordance with the present techniques, the heat pump 102 also includes a receiver 190 (e.g., vessel, liquid receiver, working fluid reservoir) disposed along the working fluid circuit 108. In particular, the receiver 190 is disposed along a liquid conduit portion 192 (e.g., conduit, conduit portion, liquid conduit) of the working fluid circuit 108 that extends between the first heat exchanger 104 and the second heat exchanger 106. The first expansion device 122 and the second expansion device 124 may also be disposed along the liquid conduit portion 192 and / or the liquid conduit portion 192 may extend between the first expansion device 122 and the second expansion device 124. The receiver 190 is configured to enable adjustable control of an amount of working fluid (e.g., liquid working fluid) circulating through the working fluid circuit 108. For example, the receiver 190 may define a chamber that is fluidly coupled to the working fluid circuit 108, and the chamber may be configured to receive and store a portion of working fluid received from the working fluid circuit 108. Thus, the portion of working fluid stored in the receiver 190 may not circulate through the working fluid circuit 108.

[0057] The receiver 190 includes a vessel 194 configured to receive and retain (e.g., store) working fluid from the working fluid circuit 108 to adjust an amount of the working fluid circulated (e.g., actively circulated) along the working fluid circuit 108. The vessel 194 may generally be arranged along an axis (e.g., a vertical axis, in a generally vertical orientation) to enable collection of working fluid within the vessel 194 at a base 196 of the vessel 194. The receiver 190 also includes a first dip tube 198 (e.g., pipe, tube, conduit) and a second dip tube 200 (e.g., pipe, tube, conduit) configured to enable flow of working fluid into and out of the vessel 194. To this end, the first dip tube 198 and the second dip tube 200 are fluidly coupled to the working fluid circuit 108 (e.g., liquid conduit portion 192). The first dip tube 198 and the second dip tube 200 may extend into the vessel 194 from an upper portion 202 of the vessel 194 and may extend through the vessel 194 (e.g., through an interior volume of the vessel 194) along a substantial portion (e.g., 50 percent, 60 percent, 70 percent, 80 percent, 90 percent) of a height 204 of the vessel 194 toward the base 196 of the vessel 194. In some embodiments, a first length of the first dip tube 198 extending along the height 204 of the vessel 194 and a second length of the second dip tube 200 extending along the height 204 of the vessel 194 may be approximately the same (e.g., similar) and / or approximately equal to one another (e.g., within 15 percent, within 10 percent, within 5 percent). As a result, the first dip tube 198 and / or the second dip tube 200 may direct working fluid from the working fluid circuit 108 (e.g., liquid conduit portion 192) to the base 196 of the vessel 194, and the first dip tube 198 and the second dip tube 200 may remain at least partially submerged within the working fluid retained and / or stored within the vessel 194. In other words, a liquid level 206 of working fluid within the vessel 194 may remain above (e.g., relative to a vertical axis, relative to a direction of gravity) at least a portion (e.g., ends, inlet, outlet) of the first dip tube 198 and the second dip tube 200 within the vessel 194.

[0058] As mentioned above, a desired amount (e.g. active charge) of working fluid flowing along the working fluid circuit 108 may vary depending on a configuration and / or design of the heat pump 102 (e.g., components of the heat pump 102, different relative volumes of the first heat exchanger 104 and the second heat exchanger 106), operating conditions of the heat pump 102, an active operating mode of the heat pump 102, and / or other parameters. Indeed, circulating a constant amount of working fluid through the working fluid circuit 108 in all operating conditions and / or operating modes may cause inefficient operation of the heat pump 102 in at least some of the operating conditions and / or operating modes. Therefore, embodiments of the heat pump 102 described herein include the receiver 190 configured to receive and retain (e.g., store) a variable amount of working fluid therein. In this way, an amount of working fluid circulated through the working fluid circuit 108 (e.g., not retained or stored within the receiver 190) may be adjusted, and more efficient operation of the heat pump 102 may be achieved across a wider range of operating conditions and / or operating modes. For example, an amount of working fluid retained within the receiver 190 may vary between a heating mode of the heat pump 102 and a cooling mode of the heat pump 102.

[0059] To enable adjustment of an amount of working fluid retained within the receiver 190 (e.g., vessel 194) during operation of the heat pump 102, operation of one or more components of the heat pump 102 (e.g., working fluid circuit 108) may be adjusted and / or otherwise controlled. For example, operation of the first expansion device 122, the second expansion device 124, or both may be adjusted to cause an adjustment to an amount of the working fluid retained within the receiver 190. To this end, the HVAC system 100 includes a controller 220 (e.g., control system, thermostat, control panel, control circuitry, automation controller, programmable controller) that is communicatively coupled to one or more components of the heat pump 102 (e.g., expansion devices 120) and is configured to monitor, adjust, and / or otherwise control operation of one or more components of the heat pump 102. For example, one or more control transfer devices, such as wires, cables, wireless communication devices, and the like, may communicatively couple the compressor 130, the expansion device(s) 120, the first and / or second fans 116, 118, the control device 16 (e.g., thermostat), and / or any other suitable components of the HVAC system 100 (e.g., heat pump 102) to the controller 220. That is, the compressor 130, the expansion device(s) 120, the first and / or second fans 116, 118, and / or the control device 16 may each have one or more communication components that facilitate wired or wireless (e.g., via a network) communication with the controller 220. In some embodiments, the communication components may include a network interface that enables the components of the HVAC system 100 to communicate via various protocols such as EtherNet / IP, ControlNet, DeviceNet, or any other communication network protocol. Alternatively, the communication components may enable the components of the HVAC system 100 to communicate via mobile telecommunications technology, Bluetooth®, near-field communications technology, and the like. As such, the compressor 130, the expansion device(s) 120, the first and / or second fans 116, 118, and / or the control device 16 may wirelessly communicate data between each other. In other embodiments, operational control of certain components of the heat pump 102 may be regulated by one or more relays or switches (e.g., a 24 volt alternating current [VAC] relay).

[0060] In some embodiments, the controller 220 may be a component of or may include the control panel 82. In other embodiments, the controller 220 may be a standalone controller, a dedicated controller, or another suitable controller included in the HVAC system 100. In any case, the controller 220 is configured to control components of the HVAC system 100 (e.g., heat pump 102) in accordance with the techniques discussed herein. The controller 220 includes processing circuitry 222, such as a microprocessor, which may execute software for controlling the components of the HVAC system 100. The processing circuitry 222 may include multiple microprocessors, one or more “general-purpose” microprocessors, one or more special-purpose microprocessors, and / or one or more application specific integrated circuits (ASICS), or some combination thereof. For example, the processing circuitry 222 may include one or more reduced instruction set (RISC) processors.

[0061] The controller 220 may also include a memory device 224 (e.g., a memory) that may store information, such as instructions, executable code, control software, look up tables, configuration data, other data, or any combination thereof. The memory device 224 may include a volatile memory, such as random access memory (RAM), and / or a nonvolatile memory, such as read-only memory (ROM). The memory device 224 may store a variety of information and may be used for various purposes. For example, the memory device 224 may store processor-executable instructions including firmware or software for the processing circuitry 222 to execute, such as instructions for controlling components of the HVAC system 100 (e.g., expansion devices 120). The memory device 224 may also store data relating to operating parameters of the HVAC system 100 (e.g., measured parameters, set points, etc.). In some embodiments, the memory device 224 is a tangible, non-transitory, machine-readable-medium that may store machine-readable instructions for the processing circuitry 222 to execute. The memory device 224 may include ROM, flash memory, a hard drive, or any other suitable optical, magnetic, or solid-state storage medium, or a combination thereof.

[0062] In accordance with present techniques, the controller 220 is configured to control operation of one or more components of the heat pump 102 to enable adjustment of an amount of working fluid retained within the vessel 194 of the receiver 190 (e.g., liquid level 206). In this way, an amount of working fluid circulated through the working fluid circuit 108 may be adjusted to enable more efficient operation of the heat pump 102. In other words, while the total amount of working fluid within then heat pump 102 may remain unchanged, an active amount of working fluid (e.g., charge, active charge) circulated through components of the heat pump 102 (e.g., first heat exchanger 104, second heat exchanger 106) may be adjusted or controlled by adjusting an amount of working fluid retained or stored within the receiver 190. The liquid level 206 (e.g., amount of working fluid) within the receiver 190 may be adjusted based on an operating mode of the heat pump 102 (e.g., heating mode, cooling mode), an operating parameter of the heat pump 102, another suitable parameter, or both. Additionally, the controller 220 may determine which of the one or more components of the heat pump 102 to control and / or adjust to cause an adjustment to the liquid level 206 (e.g., amount of working fluid) within the receiver 190, for example, based on an operating mode of the heat pump 102, based on a desired adjustment (e.g., increase, decrease) to the liquid level 206 within the receiver 190, another suitable parameter, or any combination thereof.

[0063] As mentioned above, a desired amount of working fluid (e.g., active charge) circulated through the working fluid circuit 108 may be different in the cooling mode and in the heating mode of the heat pump 102 (e.g., due to different relative volumes of the first heat exchanger 104 and the second heat exchanger 106). Accordingly, embodiments of the present disclosure are configured to adjust an amount of working fluid (e.g., liquid level 206) retained or stored within the receiver 190 based on operation of the heat pump 102 in a particular operating mode. For example, the controller 220 may be configured to adjust operation of one or more components of the heat pump 102 to cause the liquid level 206 in the receiver 190 to increase in the heating mode of the heat pump 102. In this way, an amount of the working fluid circulated along the working fluid circuit 108 may be reduced, which may enable more efficient operation of the heat pump 102 in the heating mode. Conversely, the controller 220 may be configured to adjust operation of one or more components of the heat pump 102 to cause the liquid level 206 in the receiver 190 to decrease, thereby increasing an amount of the working fluid circulated along the working fluid circuit 108, in the cooling mode of the heat pump 102 to enable more efficient operation of the heat pump 102 in the cooling mode. In some embodiments, the amount of working fluid retained or stored within the receiver 190 may be adjusted via control of an operating parameter (e.g., subcooling, superheating) of the working fluid that is circulated along the working fluid circuit 108. The controller 220 may control and / or adjust an amount of subcooling and / or superheating of the working fluid circulated along the working fluid circuit 108 via adjustment of one or more of the expansion devices 120, as described in further detail below.

[0064] During operation of the heat pump 102 in the heating mode, as illustrated in FIG. 5, the controller 220 may control operation of the heat pump 102 to increase the liquid level 206 of working fluid stored within the receiver 190 and thereby decrease an active charge of the working fluid circulated along the working fluid circuit 108. For example, the controller 220 may control operation of the first expansion device 122 to adjust an amount of subcooling of the working fluid exiting the first heat exchanger 104, which operates as a condenser in the heating mode. As will be appreciated, an amount of subcooling of the working fluid exiting the first heat exchanger 104 (e.g., condenser) may be indicative of an amount of liquid working fluid within (e.g., maintained within, trapped within) the first heat exchanger 104. The controller 220 may adjust the first expansion device 122 to decrease the amount of subcooling of the working fluid circuit exiting the first heat exchanger 104 and thereby decrease an amount of liquid working fluid contained within the first heat exchanger 104. For example, the controller 220 may adjust the first expansion device 122 toward an open position (e.g., fully open position) to enable increased flow of the working fluid therethrough. In this way, instead of an increased amount of liquid working fluid remaining within the first heat exchanger 104 (e.g., condenser), the liquid working fluid may flow along the working fluid circuit 108, through the first expansion device 122, and to the receiver 190 (e.g., along the liquid conduit portion 192). It should be appreciated that, during steady state operation of the heat pump 102 in the heating mode, the liquid working fluid flowing through the first expansion device 122 may not flash (e.g., vaporize), and the working fluid may remain in a liquid phase and flow along the liquid conduit portion 192 to the receiver 190. Specifically, the liquid working fluid may be directed into the vessel 194 via the first dip tube 198, and the liquid level 206 within the receiver 190 may increase. Accordingly, by adjusting (e.g., decreasing) the amount of subcooling of the working fluid exiting the first heat exchanger 104, such as via control and / or adjustment of the first expansion device 122, the controller 220 may reduce an amount of liquid working fluid maintained within the first heat exchanger 104 and may enable an increase in the amount of working fluid (e.g., liquid level 206) stored within the receiver 190.

[0065] The controller 220 may adjust operation of the first expansion device 122 to adjust (e.g., decrease) the amount of subcooling of the working fluid based on one or more parameters, metrics, and / or other factors. For example, the controller 220 may control the first expansion device 122 to cause the amount of subcooling of the working fluid to approach a subcooling set point (e.g., threshold amount of subcooling, subcooling amount set point, heating mode subcooling set point, first subcooling set point, target amount of subcooling). A value of the subcooling set point may be associated with operation of the heat pump 102 in the heating mode. For example, the subcooling set point may be selected, determined, and / or otherwise based on a desired amount of working fluid (e.g., active charge) actively circulated within the working fluid circuit 108 in the heating mode of the heat pump 102. In some embodiments, the subcooling set point associated with the heating mode may be a fixed value. In other embodiments, the controller 220 may be configured to adjust the subcooling set point and / or select a value of the subcooling set point based on one or more operating parameters and / or operating conditions of the heat pump 102. For example, the controller 220 may be configured to adjust the subcooling set point or select a particular value of the subcooling set point based on a detected parameter, such as an ambient temperature (e.g., within the ambient environment 112).

[0066] To these ends, the controller 220 may be communicatively coupled to and configured to receive data and / or feedback from one or more sensors 230 (e.g., temperature sensors, pressure sensors, flow rate sensors) indicative of one or more operating parameters of the heat pump 102. For example, a first sensor 232 may be disposed along the working fluid circuit 108 (e.g., liquid conduit portion 192) between the first heat exchanger 104 and the first expansion device 122. The first sensor 232 may be configured to detect a temperature and / or a pressure of the working fluid exiting the first heat exchanger 104. Based on data received from the first sensor 232, the controller 220 may determine and / or calculate an amount of subcooling (e.g., calculated amount of subcooling, measured amount of subcooling, actual amount of subcooling) of the working fluid exiting the first heat exchanger 104 (e.g., based on data stored on the memory device 224, based on a type of the working fluid). The controller 220 may compare the amount of subcooling (e.g., a value of the amount of subcooling) to the subcooling set point (e.g., stored on the memory device 224). Based on and / or in response to the comparison, the controller 220 may adjust (e.g., via one or more control signals) the first expansion device 122 to cause the amount of subcooling to approach the subcooling set point and enable flow (e.g., additional flow) of liquid working fluid from the first heat exchanger 104 to the receiver 190.

[0067] As mentioned above, the controller 220 may be configured to adjust the subcooling set point based on one or more operation parameters of the heat pump 102 detected by one or more of the sensors 230. For example, a second sensor 234 communicatively coupled to the controller 220 may be configured to detect a temperature (e.g., ambient temperature) of the ambient environment 112. Based on data received from the second sensor 234, the controller 220 may determine and implement an adjustment to the subcooling set point (e.g., stored on the memory device 224) associated with operation of the heat pump 102 in the heating mode to provide an adjusted subcooling set point. The controller 220 may then compare an actual or calculated amount of subcooling of the working fluid exiting the first heat exchanger 104 and control operation of the first expansion device 122 to cause the actual amount of subcooling to approach the adjusted subcooling set point in the manner described above. It should be appreciated that the controller 220 may receive data and / or feedback from other sensors 230 configured to detect other operating parameters, such as a temperature of the thermal load 110, an operating capacity of the compressor 130, a temperature and / or pressure of the working fluid exiting the second heat exchanger 106, an amount of working fluid within the receiver 190 (e.g., liquid level 206), another suitable operating, or any combination thereof. Indeed, the controller 220 may be configured to adjust the subcooling set point associated with the heating mode based on one or multiple operating parameters (e.g., detected by one or more sensors 230).

[0068] In some embodiments, the controller 220 may also be configured to control operation of the heat pump 102 to adjust an amount of superheat of the working fluid along the working fluid circuit 108 to cause an increase of the liquid level 206 of working fluid stored within the receiver 190 and thereby decrease an active charge of the working fluid circulated along the working fluid circuit 108 in the heating mode. As shown in the illustrated embodiment, the second expansion device 124 is disposed along the liquid conduit portion 192 between the receiver 190 and the second heat exchanger 106, which operates as an evaporator in the heating mode. Therefore, the second expansion device 124 may be controlled to adjust flow (e.g., a flow rate, an amount of flow) of the working fluid from the receiver 190 (e.g., via the second dip tube 200) to the second heat exchanger 106 to control and / or adjust the liquid level 206 in the receiver 190, as well as an amount of superheat of the working fluid exiting the second heat exchanger 106. For example, the controller 220 may be configured to adjust the second expansion device 124 toward a closed position (e.g., a fully closed position) to decrease flow of the working fluid into the second heat exchanger 106 in order to increase the amount of superheat of the working fluid exiting the second heat exchanger 106. Decreasing flow of the working fluid to the second heat exchanger 106 may also cause the liquid level 206 of the working fluid within the receiver 190 to increase, which may reduce an amount (e.g., active charge) of the working fluid actively circulating along the working fluid circuit 108. Accordingly, by adjusting (e.g., increasing) the amount of superheat of the working fluid exiting the second heat exchanger 106, such as via control and / or adjustment of the second expansion device 124, the controller 220 may enable an increase in the amount of working fluid (e.g., liquid level 206) stored within the receiver 190.

[0069] The controller 220 may be configured to control an amount of superheat of the working fluid exiting the second heat exchanger 106 based on data and / or feedback received from one or more of the sensors 230. For example, a third sensor 236 may be disposed along the working fluid circuit 108 between the second heat exchanger 106 and the reversing valve 150. The third sensor 236 may be configured to detect a temperature and / or a pressure of the working fluid exiting the second heat exchanger 106. Based on data received from the third sensor 236, the controller 220 may determine and / or calculate an amount of superheat (e.g., calculated amount of superheat, measured amount of superheat, actual amount of superheat) of the working fluid exiting the second heat exchanger 106 (e.g., based on data stored on the memory device 224, based on a type of the working fluid). The controller 220 may compare the amount of superheat (e.g., a value of the amount of superheat) to a superheat set point (e.g., stored on the memory device 224). Based on and / or in response to the comparison, the controller 220 may adjust (e.g., via one or more control signals) the second expansion device 124 to cause the amount of superheat to approach the superheat set point and enable retention of liquid working fluid (e.g., additional working fluid) within the receiver 190.

[0070] The controller 220 may be configured to adjust the superheat set point based on one or more operation parameters of the heat pump 102 detected by one or more of the sensors 230. For example, based on data received from the second sensor 234 (e.g., an ambient temperature measurement), the controller 220 may determine and implement an adjustment to the superheat set point (e.g., stored on the memory device 224) associated with operation of the heat pump 102 in the heating mode to provide an adjusted superheat set point. The controller 220 may then compare an actual or calculated amount of superheat of the working fluid exiting the second heat exchanger 106 and control operation of the second expansion device 124 to cause the actual amount of superheat to approach the adjusted superheat set point in the manner described above. It should be appreciated that the controller 220 may receive data and / or feedback from other sensors 230 configured to detect other operating parameters, such as a temperature of the thermal load 110, an operating capacity of the compressor 130, a temperature and / or pressure of the working fluid exiting the second heat exchanger 106, an amount of working fluid within the receiver 190 (e.g., liquid level 206), another suitable operating, or any combination thereof. Indeed, the controller 220 may be configured to adjust the superheat set point associated with the heating mode based on one or multiple operating parameters (e.g., detected by one or more sensors 230).

[0071] As mentioned above, FIG. 6 is a schematic of an embodiment of a portion of the HVAC system 100 that includes the heat pump 102 (e.g., a heat pump system, reverse cycle heat pump, air source heat pump, energy efficient heat pump) in accordance with present embodiments. The illustrated embodiment of the heat pump 102 is configured for operation in the cooling mode. Accordingly, the reversing valve 150 is in the second configuration 170 described above, the first heat exchanger 104 is configured to operate as an evaporator, and the second heat exchanger 106 is configured to operate as a condenser.

[0072] In the cooling mode, operation of the heat pump 102 may also be controlled to adjust an amount of working fluid flowing along the working fluid circuit 108 (e.g., active charge) and / or to adjust an amount of working fluid retained within the receiver 190. As discussed above, a desired amount (e.g. active charge) of working fluid flowing along the working fluid circuit 108 may vary depending on a configuration and / or design of the heat pump 102 (e.g., components of the heat pump 102, different relative volumes of the first heat exchanger 104 and the second heat exchanger 106), operating conditions of the heat pump 102, an active operating mode of the heat pump 102, and / or other parameters. Indeed, a desired active charge of the working fluid flowing along the working fluid circuit 108 may be different in the cooling mode than a desired active charge of the working fluid flowing along the working fluid circuit 108 in the heating mode (e.g., due to different relative volumes of the first heat exchanger 104 and the second heat exchanger 106, due to operation of the first heat exchanger 104 as an evaporator and operation of the second heat exchanger 106 as a condenser in the cooling mode).

[0073] To enable adjustment of an amount of working fluid retained within the receiver 190 (e.g., vessel 194) during operation of the heat pump 102, operation of one or more components of the heat pump 102 (e.g., working fluid circuit 108) may be adjusted and / or otherwise controlled, as similarly described above with reference to FIG. 5. For example, the controller 220 may be configured to adjust operation of one or more components of the heat pump 102 to cause the liquid level 206 in the receiver 190 to decrease, thereby increasing an amount of the working fluid circulated along the working fluid circuit 108, in the cooling mode of the heat pump 102. In particular, with the first heat exchanger 104 configured to operate as an evaporator and the second heat exchanger 106 configured to operate as a condenser in the cooling mode, the controller 220 may be configured to adjust operation of the second expansion device 124 to adjust (e.g., increase) an amount of subcooling of the working fluid exiting the second heat exchanger 106 and / or the controller 220 may be configured to adjust operation of the first expansion device 122 to adjust (e.g., decrease) an amount of superheat of the working fluid exiting the first heat exchanger 104 to cause a decrease of the liquid level 206 of working fluid stored within the receiver 190 and thereby increase an active charge of the working fluid circulated along the working fluid circuit 108 in the cooling mode. The controller 220 may be configured to adjust operation of the second expansion device 124 to adjust subcooling of the working fluid in a manner similar to the control of the first expansion device 122 to adjust subcooling of the working fluid in the heating mode. Similarly, the controller 220 may be configured to adjust operation of the first expansion device 122 to adjust superheat of the working fluid in a manner similar to the control of the second expansion device 124 to adjust superheat of the working fluid in the heating mode.

[0074] The controller 220 may also control operation of the first expansion device 122 to adjust superheat of the working fluid and / or control operation of the second expansion device 124 to adjust subcooling of the working fluid in accordance with one or more of the techniques described above with reference to FIG. 5. For example, the controller 220 may control the first expansion device 122 to adjust an amount of superheat of the working fluid exiting the first heat exchanger 104 based on data and / or feedback received from one or more of the sensors 230, such as a fourth sensor 240 (e.g., pressure sensor, temperature sensor) disposed downstream of the first heat exchanger 104 relative to a flow of the working fluid along the working fluid circuit 108 in the cooling mode. The controller 220 may control the second expansion device 124 to adjust an amount of subcooling of the working fluid exiting the second heat exchanger 106 based on data and / or feedback received from one or more of the sensors 230, such as a fifth sensor 242 (e.g., pressure sensor, temperature sensor) disposed downstream of the second heat exchanger 106 relative to a flow of the working fluid along the working fluid circuit 108 in the cooling mode. It should be appreciated that any of the sensors 230, data, and / or feedback described herein may be utilized by the controller 220 to enable adjustment of the first expansion device 122 and / or the second expansion device 124 to control superheat and / or subcooling of the working fluid, and thereby control and / or adjust an amount of working fluid retained within the receiver 190, in the cooling mode of the heat pump 102.

[0075] Additionally, the controller 220 may be configured to control the first expansion device 122 to adjust an amount of superheat of the working fluid exiting the first heat exchanger 104 to approach a superheat set point in the cooling mode (e.g., threshold amount of superheat, superheat amount set point, cooling mode superheat set point, second superheat set point, target amount of superheat), as similarly described above. The controller 220 may also be configured to control the second expansion device 124 to adjust an amount of subcooling of the working fluid exiting the second heat exchanger 106 to approach a subcooling set point in the cooling mode (e.g., threshold amount of subcooling, subcooling amount set point, cooling mode subcooling set point, second subcooling set point, target amount of subcooling). The superheat set point and / or the subcooling set point (e.g., stored on the memory device 224) utilized in the cooling mode may be different than the superheat set point and / or the subcooling set point utilized in the heating mode (e.g., due to varying volumes, such as internal volumes, of the first heat exchanger 104 and second heat exchanger 106), which may enable the heat pump 102 to store different amounts of working fluid within the receiver 190 and operate with different active charges of working fluid flowing along the working fluid circuit 108 in the different operating modes of the heat pump 102. The superheat set point and / or the subcooling set point (e.g., stored on the memory device 224) utilized in the cooling mode may be different than the superheat set point and / or the subcooling set point utilized in the heating mode (e.g., due to varying volumes, such as internal volumes, of the first heat exchanger 104 and second heat exchanger 106), which may enable the heat pump 102 to store different amounts of working fluid within the receiver 190 and operate with different active charges of working fluid flowing along the working fluid circuit 108 in the different operating modes of the heat pump 102. For example, the subcooling set point utilized in the cooling mode may be higher than the subcooling set point utilized in the heating mode to enable an increase in the active charge for working fluid circulated along the working fluid circuit 108 during operation of the heat pump 102 in the cooling mode. The superheat set point and / or the subcooling set point utilized in the cooling mode may also be adjusted, such as based on data received from one or more of the sensors 230, as discussed above.

[0076] It should be noted that, during operation of the heat pump 102 in each of the cooling mode and the heating mode, the controller 220 may be configured to control operation of the first expansion device 122 and the second expansion device 124 independently of one another to enable independent control of the amount of superheat and the amount of subcooling of the working fluid circulated along the working fluid circuit 108. Even so, control of the heat pump 102 and the components thereof may nevertheless be dependent on a desirable charge (e.g., active charge) of the working fluid flowing through the working fluid circuit 108. As will be appreciated, adjustment of one of the expansion devices 122, 124 to adjust one of the amount of superheat or the amount of subcooling may affect control of the other of the expansion devices 122, 124 to adjust the other of the amount of superheat or the amount of subcooling.

[0077] In some embodiments, the controller 220 may be configured to control and / or adjust operation of the first expansion device 122 and the second expansion device 124 based on a prioritization scheme. For example, in the heating mode, the controller 220 may be configured to first adjust operation the first expansion device 122 to cause the amount of subcooling (e.g., measured amount of subcooling, calculated amount of subcooling, subcooling of working fluid exiting the first heat exchanger 104) to approach a subcooling set point associated with operation of the heat pump 102 in the heating mode. In response to a determination that the amount of subcooling reaches the subcooling set point and / or in response to a determination that the amount of subcooling is within a threshold amount (e.g., a threshold value, a threshold percentage) of the subcooling set point, the controller 220 may then adjust operation of the second expansion device 124 to cause the amount of superheat (e.g., measured amount of superheat, calculated amount of superheat, superheat of working fluid exiting the second heat exchanger 106) to approach a superheat set point associated with operation of the heat pump 102 in the heating mode. In the cooling mode, the controller 220 may be configured to first adjust operation the second expansion device 124 to cause the amount of subcooling (e.g., measured amount of subcooling, calculated amount of subcooling, subcooling of working fluid exiting the second heat exchanger 106) to approach a subcooling set point associated with operation of the heat pump 102 in the cooling mode. In response to a determination that the amount of subcooling reaches the subcooling set point and / or in response to a determination that the amount of subcooling is within a threshold amount (e.g., a threshold value, a threshold percentage) of the subcooling set point, the controller 220 may then adjust operation of the first expansion device 122 to cause the amount of superheat (e.g., measured amount of superheat, calculated amount of superheat, superheat of working fluid exiting the first heat exchanger 104) to approach a superheat set point associated with operation of the heat pump 102 in the heating mode. Indeed, in some embodiments, the controller 220 may be configured to prioritize adjustment of an amount of subcooling of the working fluid in both the heating mode and the cooling mode, but in other embodiments the controller 220 may be configured to control the first expansion device 122 and the second expansion device 124 based on another priority scheme and / or simultaneously (e.g., without prioritization of controlling the amount of subcooling or the amount of superheat).

[0078] In some embodiments, the heat pump 102 may be configured to regulate the active charge of working fluid circulating through the working fluid circuit 108 at least partially based on the liquid level 206 within the receiver 190. To this end, the receiver 190 may include a fluid level sensor 228 (e.g., liquid level sensor) configured to detect the liquid level 206 (e.g., amount of liquid, volume of liquid, height of liquid) in the vessel 194. Based on the liquid level 206 detected via the fluid level sensor 228, the controller 220 may determine or deduce the active charge within the working fluid circuit 108. For example, the controller 220 may include instructions (e.g., one or more lookup tables, charts, and / or algorithms) stored in the memory device 224 correlating amounts of active charge of working fluid circulating through working fluid circuit 108 (e.g., values indicative of different active charge amounts) with liquid level 206 amounts in the receiver 190 (e.g., values indicative of different levels or amounts of liquid within the receiver 190). In some embodiments, the controller 220 may determine a total volume of working fluid within the receiver 190 based on one or more structural features of the receiver 190 (e.g., dimensions of the vessel 194, dimensions of internal components (e.g., dip tubes)) and data received from the fluid level sensor 228 (e.g., liquid level 206). The liquid level 206 may be indicative of a portion of the total internal volume of the vessel 194 occupied by liquid working fluid.

[0079] Based on a determination of the volume of working fluid within the receiver 190, the controller 220 may determine the active charge of working fluid circulating throughout the working fluid circuit 108. For example, the controller 220 may include instructions within the memory device 224 relating active charge to the total charge and the total volume of working fluid in the receiver 190. Specifically, the controller 220 may determine a difference between the volume of working fluid in the receiver 190 and the total charge of working fluid in the heat pump 102 to determine the active charge of working fluid circulating along the working fluid circuit 108. In some embodiments, the total charge of working fluid in the heat pump 102 may be an initial amount of working fluid installed with the heat pump 102 during, for example, installation or maintenance. As such, the total charge of working fluid in the working fluid circuit 108 may be a predetermined and / or known value and may be stored in the memory device 224.

[0080] In some embodiments, the memory device 224 of the controller 220 may include or store instructions (e.g., one or more algebraic equations, tables, and / or look up charts) to determine a desired active charge of working fluid based on an operating mode of the heat pump 102, one or more parameters of the heat pump 102, respective internal volumes of the first heat exchanger 104 and / or the second heat exchanger, ambient temperatures, another suitable parameter, or a combination thereof. In response to a determination of a desired active charge of working fluid to circulate through the working fluid circuit 108, the controller 220 may then compare the active charge of working fluid (e.g., determined by the controller 220, determined active charge) to the desired charge of working fluid to circulate through the working fluid circuit 108.

[0081] In response to a determination that the active charge of working fluid circulating through the working fluid circuit 108 is less than the desired charge, the controller 220 may actuate one or more components of the heat pump 102 (e.g., expansion devices 120) to decrease the liquid level 206 in the receiver 190 in a manner similar to that discussed above in order to increase the active charge of working fluid circulating through the working fluid circuit 108. In response to a determination that the active charge circulating through the working fluid circuit 108 is greater than the desired charge, the controller 220 may actuate one or more components of the heat pump 102 to increase the liquid level 206 in the receiver 190 in a manner similar to that discussed above to cause a decrease in the active charge.

[0082] While the presently disclosed techniques are described in the context of embodiments of the heat pump 102 configured as air-source heat pumps (e.g., air-to-air heat pumps) utilizing the first heat exchanger 104 and the second heat exchanger 106 configured as air-to-fluid (e.g., air-to-working fluid) heat exchangers, it should be appreciated that the present techniques may also be utilized with embodiments of the heat pump 102 having other configurations, such as air-to-liquid heat pumps having at least one heat exchanger configured to place a working fluid in a heat exchange relationship with a flow of liquid, such as water. For example, FIGS. 7 and 8 are schematics of an embodiment of a portion of the HVAC system 100 including the heat pump 102 with the first heat exchanger 104 configured as a working fluid-to-liquid heat exchanger. For example, the first heat exchanger 104 may be configured to place the working fluid circulated along the working fluid circuit 108 in a heat exchanger relationship with a flow of liquid, such as water, received from the thermal load 110 (e.g., air handling equipment, terminal unit, air handler) and to supply a conditioned (e.g., heated, cooled) flow of liquid to the thermal load 110 to enable conditioning of the thermal load 110. FIG. 7 illustrates the heat pump 102 configured for operation in the heating mode, and FIG. 8 illustrates the heat pump 102 configured for operation in the cooling mode. The second heat exchanger 106 of the illustrated embodiments is configured to place the working fluid in a heat exchange relationship with ambient air from the ambient environment 112, as similarly described above. It should be appreciated that the embodiments of the heat pump 102 illustrated in FIGS. 7 and 8 may be configured as a chiller system or other embodiment of the heat pump 102 configured to cool and / or heat a flow of liquid (e.g., water).

[0083] As similarly described above, the respective configurations of the first heat exchanger 104 (e.g., working fluid-to-liquid heat exchanger) and the second heat exchanger 106 (e.g., working fluid-to-air heat exchanger) may be different from one another. For example, the second heat exchanger 106 may have a greater (e.g., significantly greater) internal volume (e.g., internal working fluid volume, second internal volume) than the internal volume of the first heat exchanger 104 (e.g., internal working fluid volume, first internal volume). Indeed, a variety of different heat exchanger configurations (e.g., microchannel tubes, shell and tube, round-tube) may be utilized for the first heat exchanger 104 and the second heat exchanger 106, which may demand different active charges of working fluid flowing along the working fluid circuit 108 in different operating modes of the heat pump 102 to enable more efficient operation of the heat pump 102. Accordingly, the present techniques enabling adjustment of the active charge of working fluid within the working fluid circuit 108 may be implemented with such configurations of the heat pump 102, such as the configurations illustrated in FIGS. 7 and 8, to enable more efficient operation of the heat pump 102 in the heating mode and the cooling mode. The present techniques may also enable improved (e.g., more efficient) operation of heat pumps 102 utilizing certain types of working fluids, such as high glide refrigerants (e.g., R-454C, R-474A).

[0084] As discussed above, embodiments of the present disclosure include the controller 220 configured to control operation of the heat pump 102 (e.g., expansion devices 120) to enable more efficient operation of the heat pump 102 across a wider range of operating conditions. For example, the controller 220 may be configured to execute one or more control sequences to adjust one or more of the expansion devices 120 based on an operating mode of the heat pump 102 and / or based on operating conditions of the heat pump 102. As described in further detail below, the control sequences executed by the controller 220 may enable control of the heat pump 102 to achieve one or more desired operating parameters (e.g., active working fluid charge level), such as based on an active operating mode (e.g., heating mode, cooling mode) and / or operating conditions of the heat pump 102. In this way, the present techniques enable more efficient operation of the heat pump 102 across a wider range of operating conditions.

[0085] With the foregoing in mind, FIGS. 9 is a flow chart of an embodiment of a control sequence or method 300 for operating the heat pump 102, and FIGS. 10 and 11 are flow charts of embodiments of various control sequence (e.g., portions) of the method 300, in accordance with aspects of the present disclosure. As will be appreciated, one or more steps (e.g., control sequences) of the method 300 may be performed by the controller 220. For example, computer executable instructions or code for performing the one or more control sequences and / or other portions of the method 300 may be stored on the memory device 224, and the processing circuitry 222 may execute the instructions to perform the one or more control sequences of the method 300. In some embodiments, one or more steps of the method 300 may be performed by another controller of the HVAC system 100. In additional or alternative embodiments, multiple components or systems may perform one or more steps of the method 300. It should also be noted that additional steps may be performed with respect to the illustrated method 300 and control sequences thereof. Moreover, certain steps of the method 300 may be removed, modified, and / or performed in a different order. In some embodiments, certain steps of the method 300 may not be performed, for example, based on a configuration of the heat pump 102, such as based on a number and / or arrangement of the expansion devices 120 included in the heat pump 102. In some embodiments of the heat pump 102 including the first expansion device 122 and the second expansion device 124, the controller 220 may be configured to execute all or substantially all of the steps and / or control sequences of the method 300. Further still, one or more of the steps of the method 300 described herein may be performed in any suitable relation with one another, such as in response to one another and / or in parallel with one another.

[0086] As indicated by blocks 302 and 304 of FIG. 9, the method 300 may begin with initiating or starting operation of the heat pump 102 and receiving a call for conditioning. For example, the controller 220 may receive the call for conditioning from a thermostat of the HVAC system 100, and the call for conditioning may be indicative of a desired type of conditioning (e.g., heating, cooling) for the space to be conditioned.

[0087] The method 300 may proceed to block 306, and a determination may be made regarding whether a demand for heating of the space to be conditioned by the heat pump 102 exists. For example, the controller 220 may determine whether the call for conditioning is indicative of a call or demand for heating. If a demand for heating exists, the method 300 may continue to a heating control sequence 320, which is described further below with reference to FIG. 10.

[0088] In response to a determination that a demand for heating does not exist at block 306, a determination may be made regarding whether a demand for cooling exits, as indicated by block 308. For example, the controller 220 may determine whether the call for conditioning is indicative of a call or demand for cooling. In response to a determination that a demand for cooling exists, the method 300 may continue to the cooling control sequence 344, which is described further below with reference to FIG. 11. As will be appreciated, the decisions made in block 306 and block 308 may be performed in an alternate order or may be performed simultaneously.

[0089] In response to a determination that a demand for heating does not exit, and a demand for cooling does not exist, the method 300 may continue to block 310, whereby the method 300 may end. For example, at block 310, the heat pump 102 may not initiate operation in the cooling mode or the heating mode. In some embodiments, the heat pump 102 may transition or remain in an idle or non-operating state at block 310.

[0090] Referring now to FIG. 10, a flow chart of an embodiment of a portion of the method 300, illustrating the heating control sequence 320, is shown. As mentioned above, the method 300 may proceed to the heating control sequence 320 in response to a determination that a demand for heating exists at block 306 described above. Execution of the heating control sequence 320 may coincide with operation of the heat pump 102 in the heating mode. To enable operation of the heat pump 102 in the heating mode, the reversing valve 150 may be actuated to and / or be maintained in the first configuration 164. Thus, in some instances, the heating control sequence 320 may include a step of transitioning the reversing valve 150 to the first configuration 164.

[0091] The heating control sequence 320 may begin with block 322. At block 322, the first expansion device 122 (e.g., indoor EEV) may be adjusted to a fully open position. In this way, working fluid discharged by the first heat exchanger 104 in the heating mode of the heat pump 102 may flow through the first expansion device 122 with reduced and / or without inducing a pressure drop and / or flow restriction (e.g., throttling) of the working fluid. Thus, the working fluid discharged from the first heat exchanger 104 may flow towards the receiver 190 in a liquid phase. In some embodiments, the controller 220 may maintain the first expansion device 122 in a fully open configuration for a predetermined period of time before the heating control sequence 320 proceeds to block 324 and / or block 326. In other embodiments, the controller 220 may maintain the first expansion device 122 in a fully open configuration until the receiver 190 is operating at steady state (e.g., working fluid flowing into the receiver 190 is equal to or approximately equal to working fluid flowing out of the receiver 190).

[0092] The heating control sequence 320 may then proceed to block 324 and / or block 326. At block 324, an actual superheat value (e.g., measured superheat value, calculated superheat value) of the working fluid exiting the second heat exchanger 106 may compared to a superheat set point (e.g., superheat set point value) to determine whether the actual superheat value is less than the superheat set point. In some embodiments, the actual superheat value may be calculated by subtracting the saturation temperature of the working fluid within the second heat exchanger 106 from a measured temperature (e.g., actual temperature, measured via third sensor 236) of the working fluid exiting the second heat exchanger 106. The saturation temperature may be determined via detections or measurements (e.g., pressure measurement) of one or more sensors 230 located, for example, at an outlet of the second heat exchanger 106 (e.g., third sensor 236). Similarly, the temperature of the working fluid exiting the second heat exchanger 106 may be measured via detections or measurements of one or more sensors 230 also located, for example, at an outlet of the second heat exchanger 106 (e.g., third sensor 236). To this end, the controller 220 may be configured to receive data and / or feedback from one or more sensors 230 of the heat pump 102, such as working fluid pressure sensors (e.g., suction pressure sensor, discharge pressure sensor), an ambient temperature sensor, a working fluid temperature sensor, and / or other suitable sensor to determine (e.g., calculate) an actual superheat value of the working fluid exiting the second heat exchanger 106.

[0093] Further, in some embodiments, the superheat set point may be a predetermined set point stored in the memory device 224 of the controller 220. The heat pump 102 may have a predetermined superheat set point that may be based on one or more parameters of the heat pump 102 and / or an operational configuration (e.g., operating mode) of the heat pump 102. For instance, the memory device 224 of the controller 220 may store different superheat set point values associated with the heating mode and the cooling mode of the heat pump 102. For example, in the heating mode configuration illustrated in FIG. 5 and for which the heating control sequence 320 of FIG. 10 may be executed, the superheat set point may be greater than the superheat set point associated with the cooling mode of the heat pump 102. Furthermore, the superheat set point may be based on one or more parameters of the heat pump 102, such as respective internal volumes of the first heat exchanger 104 and / or the second heat exchanger 106. In other embodiments, the superheat set point may be calculated, selected, and / or otherwise determined (e.g., via the controller 220), such as based on an ambient temperature or another operating condition or the heat pump 102 (e.g., measured by one or more of the sensors 230).

[0094] In response to a determination that the actual superheat value is less than the superheat set point, the heating control sequence 320 may proceed to block 328. At block 328, the second expansion device 124 (e.g., outdoor EEV) may be controlled to adjust the actual superheat value of the heat pump 102. For example, the controller 220 may control, adjust, or otherwise operate the second expansion device 124 to cause the actual superheat value of the working fluid to approach the superheat set point. To this end, one or more values of the superheat set point may be stored in the memory device 224 of the controller 220, and / or the controller 220 may receive feedback from one or more of the sensors 230 (e.g., temperature and / or pressure sensors disposed along the working fluid circuit 108) to determine whether adjustment of the second expansion device 124 is desired to achieve the superheat set point. As described above, by controlling the second expansion device 124 to increase the actual superheat value (e.g., by adjusting the second expansion device 124 towards a closed position), the liquid level 206 within the receiver 190 may be increased. Accordingly, the active charge of working fluid circulating through the working fluid circuit 108 may decrease, which may enable more efficient operation of the heat pump 102 in the heating mode.

[0095] Based on a determination that actual superheat value is greater than or equal to superheat set point, the heating control sequence 320 may proceed to block 330. At block 330, the second expansion device 124 (e.g., outdoor EEV) may be controlled to adjust towards a fully open position. As will be appreciated, adjusting the second expansion device 124 towards the fully open position may increase the flow of working fluid into the second heat exchanger 106 and thereby decrease the actual superheat value of the working fluid. As a result, the liquid level 206 of working fluid retained and / or stored in the receiver 190 may decrease and thereby increase the active charge of working fluid circulating through the working fluid circuit 108. In the manner described above, the controller 220 may control operation of the second expansion device 124 to adjust the actual superheat value of the working fluid exiting the second heat exchanger 106 (e.g., toward a superheat set point value associated with the heating mode) and thereby adjust an amount of working fluid retained within the receiver 190 to effectuate an adjustment to the active charge of working fluid circulated through the working fluid circuit 108 to increase the efficiency of the heat pump 102.

[0096] Referring back to block 322, after the controller 220 adjusts the first expansion device 122, the heating control sequence 320 may also proceed to block 326. In some embodiments, the heating control sequence 320 may execute both blocks 324 and 326 simultaneously. At block 326, an actual subcooling value (e.g., measured subcooling value, calculated subcooling value) may be compared to a subcooling set point (e.g., subcooling set point value) to determine whether the actual subcooling value is less than the subcooling set point. In some embodiments, the actual subcooling value may be calculated by subtracting the saturation temperature of the working fluid within the first heat exchanger 104 from a measured temperature (e.g., actual temperature, measured via first sensor 232) of the working fluid exiting the first heat exchanger 104. The saturation temperature may be determined via detections or measurements (e.g., pressure measurement) of one or more sensors 230 located, for example, at an outlet of the first heat exchanger 104 (e.g., first sensor 232). Similarly, the temperature of the working fluid exiting the first heat exchanger 104 may be measured via detections or measurements of one or more sensors 230 also located, for example, at an outlet of the first heat exchanger 104 (e.g., first sensor 232). To this end, the controller 220 may be configured to receive data and / or feedback from one or more sensors 230 of the heat pump 102, such as working fluid pressure sensors (e.g., suction pressure sensor, discharge pressure sensor), an ambient temperature sensor, a working fluid temperature sensor, or other suitable sensor to determine (e.g., calculate) an actual subcooling value of the working fluid exiting the first heat exchanger 104.

[0097] Further, in some embodiments, the subcooling set point may be a predetermined set point stored in the memory device 224 of the controller 220. The heat pump 102 may have a predetermined subcooling set point that may be based on one or more parameters of the heat pump 102 and / or a configuration of the heat pump 102. For instance, the memory device 224 of the controller 220 may store different subcooling set point values associated with the heating mode and the cooling mode of the heat pump 102. For example, in the heating mode illustrated in FIG. 5 and for which the heating control sequence 320 of FIG. 10 may be executed, the subcooling set point may be less than the subcooling set point associated with the cooling mode of the heat pump 102. Furthermore, the subcooling set point may be based on one or more parameters of the heat pump 102, such as internal volumes of the first heat exchanger 104 and / or the second heat exchanger 106. In other embodiments, the subcooling set point may be calculated, selected, and / or otherwise determined (e.g., via the controller 220), such as based on an ambient temperature and / or another operating condition or the heat pump 102 (e.g., measured by one or more of the sensors 230).

[0098] In response to a determination that the actual subcooling value is less than the subcooling set point, the heating control sequence 320 may proceed to block 332. At block 332, the first expansion device 122 (e.g., indoor EEV) may be controlled to adjust the actual subcooling value of the heat pump 102. For example, the controller 220 may control, adjust, or otherwise operate the first expansion device 122 to cause the actual subcooling value of the working fluid to approach the subcooling set point. To this end, one or more values of the subcooling set point may be stored in the memory device 224 of the controller 220, and / or the controller 220 may receive feedback from one or more of the sensors 230 (e.g., temperature and / or pressure sensors disposed along the working fluid circuit 108) to determine whether adjustment of the first expansion device 122 is desired to achieve the subcooling set point. In some embodiments, adjusting the first expansion device 122 to adjust the actual subcooling value may at least partially restrict flow of the working fluid leaving the first heat exchanger 104. As such, the residence time of the working fluid in the first heat exchanger 104 may increase, thereby causing an increase in the actual subcooling value due to an increased amount of working fluid in the first heat exchanger 104. In this way, the receiver 190 may experience a decrease in working fluid, thus decreasing the liquid level 206. Accordingly, the charge (e.g., working fluid) circulating through the working fluid circuit 108 may increase. As such, by controlling the subcooling set point, the controller 220 may also directly control the amount of charge circulating through the working fluid circuit 108, thus increasing the efficiency of the heat pump 102 and decreasing emission of greenhouse gases.

[0099] Based on a determination that actual subcooling value is greater than or equal to the subcooling set point, the heating control sequence 320 may proceed to block 334. At block 334, the first expansion device 122 (e.g., indoor EEV) is maintained in the fully open position. As will be appreciated, adjusting the first expansion device 122 to a fully opened position may increase the flow of working fluid out of the first heat exchanger 104, decreasing the amount of working fluid in the first heat exchanger 104 and the residence time of the working fluid in the first heat exchanger 104. As such, the actual subcooling in the heat pump 102 may decrease. Further, the adjusting of the first expansion device 122 may result in the receiver 190 experiencing an increase in working fluid, thus increasing the liquid level 206. Accordingly, the charge of working fluid circulating through the working fluid circuit 108 may decrease.

[0100] After blocks 328, 330, 332, and 334 the heating control sequence 320 may proceed to block 316 to end the heating control sequence 320. In some embodiments, subsequent to execution of the steps in blocks 328, 330, 332, and 334, the sequence may restart at blocks 324 and / or 326, creating an iterative sequence to adjust the expansion devices 120 to achieve the subcooling set point, the superheat set point, and a desired active charge of working fluid circulating in the working fluid circuit 108 in the heating mode.

[0101] Referring now to FIG. 11, a flow chart of an embodiment of the method 300, illustrating the cooling control sequence 344, is shown. As mentioned above, the method 300 may proceed to the cooling control sequence 344 in response to the determination that a demand for cooling exists at block 308 of the method 300. In other words, the cooling control sequence 344 may be executed in a cooling mode of the heat pump 102. As discussed above, the reversing valve 150 may be actuated to and / or maintained in the second configuration 170 in the cooling mode of the heat pump 102. Thus, in some instances, the cooling control sequence 344 may include a step of transitioning the reversing valve 150 to the second configuration 170.

[0102] The cooling control sequence 344 may begin with block 346. At block 346, the second expansion device 124 (e.g., outdoor EEV) may be adjusted to a fully open position. In this way, working fluid discharged by the second heat exchanger 106 in the cooling mode of the heat pump 102 may flow through the second expansion device 124 with reduced and / or without inducing a pressure drop and / or flow restriction (e.g., throttling). In other words, the working fluid discharged from the second heat exchanger 106 may flow towards the receiver 190 in a liquid phase.

[0103] The cooling control sequence 344 may then proceed to block 348. At block 348, an actual superheat value (e.g., measured superheat value, calculated superheat value) of the working fluid exiting the first heat exchanger 104 may be compared to a superheat set point (e.g., superheat set point value) to determine whether the actual superheat value is less than the superheat set point. In some embodiments, the actual superheat value may be calculated by subtracting the saturation temperature of the working fluid within the first heat exchanger 104 from a measured temperature (e.g., actual temperature, measured via fourth sensor 240) of the working fluid exiting the first heat exchanger 104. The saturation temperature may be determined via detections or measurements (e.g., pressure measurement) of one or more sensors 230 located, for example, at an outlet of the first heat exchanger 104 (e.g., fourth sensor 240). Similarly, the temperature of the working fluid exiting the first heat exchanger 104 may be measured via detections or measurements of one or more sensors 230 also located, for example, at an outlet of the first heat exchanger 104 (e.g., fourth sensor 240). To this end, the controller 220 may be configured to receive data and / or feedback from one or more sensors 230 of the heat pump 102, such as working fluid pressure sensors (e.g., suction pressure sensor, discharge pressure sensor), an ambient temperature sensor, a working fluid temperature sensor, and / or other suitable sensor to determine (e.g., calculate) an actual superheat value of the working fluid exiting the first heat exchanger 104 in the cooling mode.

[0104] Further, in some embodiments, the superheat set point may be a predetermined set point stored in the memory device 224 of the controller 220. The heat pump 102 may have a predetermined superheat set point that may be based on one or more parameters of the heat pump and / or a configuration of the heat pump. For instance, the memory device 224 of the controller 220 may store different superheat set point values associated with the heating mode and the cooling mode of the heat pump 102 in a heating mode and a cooling mode. For example, in the cooling mode configuration illustrated in FIG. 6 and for which the cooling control sequence 344 of FIG. 11 may be executed, the superheat set point may be smaller than the superheat set point associated with for in a heating mode. Furthermore, the superheat set point may be based on one or more parameters of the heat pump 102, such as internal volumes of the first heat exchanger 104 and second heat exchangers 106. In other embodiments, the superheat set point may be calculated, selected, and / or otherwise determined (e.g., via the controller 220), such as based on an ambient temperature or another operating condition of the heat pump 102 (e.g., measured by one or more sensors 230.

[0105] In response to a determination that the actual superheat value is less than the superheat set point, the cooling control sequence 344 may proceed to block 352. At block 352, the first expansion device 122 (e.g., indoor EEV) may be controlled to adjust the actual superheat value the heat pump 102. For example, the controller 220 may control, adjust, or otherwise operate the first expansion device 122 to cause the actual superheat value of the working fluid to approach the superheat set point. To this end, one or more values of the superheat set point may be stored in the memory device 224 of the controller 220, and / or the controller 220 may receive feedback from one or more of the sensors 230 (e.g., temperature and / or pressure sensors disposed along the working fluid circuit 108) to determine whether adjustment of the first expansion device 122 is desired to achieve the superheat set point. As described above, by controlling the first expansion device 122 to increase the actual superheat value (e.g., by adjusting the first expansion device 122 towards a closed position), the liquid level 206 within the receiver 190 may be increased. Accordingly, the active charge of working fluid circulating through the working fluid circuit 108 may decrease. As such, by controlling the superheat set point, the controller 220 may also directly control the amount of charge in the working fluid circuit 108, which may enable more efficient operation of the heat pump 102 in the cooling mode.

[0106] Based on a determination that actual superheat value is greater than or equal to the superheat set point, the cooling control sequence 344 may proceed to block 354. At block 354, the first expansion device 122 (e.g., indoor EEV) may be controlled to adjust towards a fully open position. As will be appreciated, adjusting the first expansion device 122 towards the fully open position may increase the flow of working fluid into the first heat exchanger 104 and thereby decrease the actual superheat value of the working fluid. As a result the liquid level 206 of working fluid retained and / or stored in the receiver 190 may decrease and thereby increase the active charge of working fluid circulating through the working fluid circuit 108 may increase. In the manner described above, the controller 220 may control operation of the first expansion device 122 to adjust the actual superheat value of the working fluid exiting first heat exchanger 104 (e.g., toward a superheat set point value associated with the cooling mode) and thereby adjust an amount of working fluid retained within the receiver 190 to effectuate an adjustment to the active charge of working fluid circulated through the working fluid circuit 108 to increase the efficiency of the heat pump 102.

[0107] Referring back to block 346, after the controller 220 adjusts the second expansion device 124, the cooling control sequence 344 may proceed to block 350. In some embodiments, the cooling control sequence 344 may execute both blocks 348 and 350 simultaneously. At block 350, an actual subcooling value (e.g., measured subcooling value, calculated subcooling value) may be compared to a subcooling set point (e.g., subcooling set point value) to determine whether the actual subcooling value is less than the subcooling set point. In some embodiments, the actual subcooling value may be calculated by subtracting the saturation temperature of the working fluid within the second heat exchanger 106 from a measured temperature (e.g., actual temperature, measured via fifth sensor 242) of the working fluid exiting the second heat exchanger 106. The saturation temperature may be determined via detections or measurements (e.g., pressure measurement) of one or more sensors 230 located, for example, at an outlet of the second heat exchanger 106 (e.g., fifth sensor 242). Similarly, the temperature of the working fluid exiting the second heat exchanger 106 may be measured via detections or measurements of one or more sensors 230 also located, for example, at an outlet of the second heat exchanger 106 (e.g., fifth sensor 242). To this end, the controller 220 may be configured to receive data and / or feedback from one or more sensors 230 of the heat pump 102, such as working fluid pressure sensors (e.g., suction pressure sensor, discharge pressure sensor), an ambient temperature sensor, a working fluid temperature sensor, and / or other suitable sensors to determine (e.g., calculate) an actual subcooling value of the working fluid exiting at the second heat exchanger 106 in a cooling mode.

[0108] Further, in some embodiments, the subcooling set point may be a predetermined set point stored in the memory device 224 of the controller 220. The heat pump 102 may have a predetermined subcooling set point that may be based on one or more parameters of the heat pump 102 and / or a configuration of the heat pump 102. For instance, the memory device 224 of the controller 220 may store different subcooling set point values associated with the heating mode and the cooling mode of the heat pump 102. For example, in the cooling mode as illustrated in FIG. 6 and for which the cooling control sequence 344 of FIG. 11 may be executed, the subcooling set point may be greater than the subcooling set point associated with the heating mode. Furthermore, the subcooling set point may be based on one or more parameters of the heat pump 102, such as internal volumes of the first heat exchanger 104 and / or the second heat exchangers 106. In other embodiments, the subcooling set point may be calculated, selected, and / or otherwise determined (e.g., via the controller 220), such as based on an ambient temperature and / or operating another condition or the heat pump 102 (e.g., measured by one or more of the sensors 230).

[0109] In response to a determination that the actual subcooling value is less than a subcooling set point, the cooling control sequence 344 may proceed to block 356. At block 356, the second expansion device 124 (e.g., outdoor EEV) may be controlled to adjust subcooling value of the heat pump 102. For example, the controller 220 may control, adjust, or otherwise operate the second expansion device 124 to cause the actual subcooling value of the working fluid to approach the subcooling set point. To this end, one or more values of the subcooling set point may be stored in the memory device 224 of the controller 220, and / or the controller 220 may receive feedback from one or more of the sensors 230 (e.g., temperature and / or pressure sensors disposed along the working fluid circuit 108) to determine whether adjustment of the second expansion device 124 is desired to achieve the subcooling set point. In some embodiments, adjusting the second expansion device 124 to adjust the actual subcooling value may at least partially restrict flow of the working fluid leaving the second heat exchanger 106. As such, the working fluid in the second heat exchanger 106 may increase, and the residence time of the working fluid in the second heat exchanger 106 may increase, thereby causing an increase in the actual subcooling value due to an increased amount of working fluid in the second heat exchanger 106. In this way, the receiver 190 may experience a decrease in working fluid, thus decreasing the liquid level 206. Accordingly, the active charge of the working fluid circulating through the working fluid circuit 108 may increase, which may enable more efficient operation of the heat pump 102 in the cooling mode.

[0110] Based on a determination that actual subcooling value is greater than or equal to the subcooling set point, the cooling control sequence 344 may proceed to block 358. At block 358, the second expansion device 124 (e.g., outdoor EEV) may be maintained in the fully open position. As will be appreciated, adjusting the second expansion device 124 to a fully opened position may increase the flow of working fluid out of the second heat exchanger 106, decreasing the amount of working fluid in the second heat exchanger 106, and the residence time of the working fluid in the second heat exchanger 106. As such, the actual subcooling in the heat pump 102 may decrease. Further, the adjusting of the second expansion device 124 may result in the receiver 190 experiencing an increase in working fluid, thus increasing the liquid level 206. Accordingly, the active charge of the working fluid circulating through the working fluid circuit 108 may decrease, which may enable more efficient operation of the heat pump 102 in the cooling mode.

[0111] After blocks 352, 354, 356, and 358 the cooling control sequence 344 may proceed to block 316 to end the method 300. In some embodiments, after the control of the expansion devices 120 in blocks 352, 354, 356, and 358, the sequence may restart at blocks 348, and 350, creating an iterative sequence to adjust the expansion devices 120 to obtain the set point subcooling, the set point superheating, and a desired heat pump 102 charge in the working fluid circuit 108.

[0112] Further, it should be appreciated that other steps of the method 300 may be performed iteratively throughout an operating cycle of the heat pump 102. For example, in the heating mode, the steps of the heating control sequence 320 may be performed iteratively (e.g., based on updated data or feedback received from one or more sensors 230), such that the controller 220 may execute some or all blocks of the heating control sequence 320. Similarly, in the cooling mode, the steps of the cooling control sequence 344 may be performed iteratively (e.g., based on updated data or feedback received from one or more sensors 230), such that the controller 220 may execute some or all blocks of the cooling control sequence 344. In such embodiments, transition from different portions of the heating control sequence 320 and the cooling control sequence 344 may be regulated via reference to additional threshold values such as cut-in or cut-out threshold values to avoid repetitive, excessive, or otherwise undesirable transition between different operating modes and / or control sequences of the method 300.

[0113] As set forth above, embodiments of the present disclosure may provide one or more technical effects useful for regulating an active working fluid charge in a heat pump to enable more efficient operation of the heat pump in both a cooling mode and a heating mode of the heat pump. As a result, the present techniques enable utilization of heat pumps to operate with reduced energy consumption and reduced greenhouse gas emissions. It should be understood that the technical effects and technical problems in the specification are examples and are not limiting. Indeed, it should be noted that the embodiments described in the specification may have other technical effects and can solve other technical problems.

[0114] While only certain features and embodiments have been illustrated and described, many modifications and changes may occur to those skilled in the art, such as variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, such as temperatures and pressures, mounting arrangements, use of materials, colors, orientations, and so forth, without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the disclosure.

[0115] Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described, such as those unrelated to the presently contemplated best mode, or those unrelated to enablement. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.

[0116] The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function]…” or “step for [perform]ing [a function]…”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).

Examples

Embodiment Construction

[0019]One or more specific embodiments of the present disclosure will be described below. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers’ specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0020]When introducing elements of various embodiments o...

Claims

1. An energy efficient heat pump for a heating, ventilation, and air conditioning (HVAC) system, comprising:a working fluid circuit configured to circulate a working fluid therethrough, wherein the working fluid circuit comprises a first heat exchanger configured to transfer heat between the working fluid and a supply air flow, a second heat exchanger configured to transfer heat between the working fluid and an ambient air flow, a first expansion device, and a second expansion device;a liquid conduit portion of the working fluid circuit extending between the first heat exchanger and the second heat exchanger, wherein the first expansion device and the second expansion device are disposed along the liquid conduit portion;a receiver disposed along the liquid conduit portion of the working fluid circuit between the first expansion device and the second expansion device, wherein the receiver comprises a vessel configured to retain an amount of the working fluid therein; anda controller communicatively coupled to the first expansion device and the second expansion device, wherein the controller is configured to adjust the first expansion device, the second expansion device, or both to adjust the amount of the working fluid retained within the vessel of the receiver.

2. The energy efficient heat pump of claim 1, wherein the controller is configured to adjust the first expansion device, the second expansion device, or both to adjust the amount of the working fluid retained within the vessel of the receiver based on an operating mode of the energy efficient heat pump, an operating parameter of the energy efficient heat pump, or both.

3. The energy efficient heat pump of claim 2, wherein the controller is configured to control the first expansion device and the second expansion device to adjust the amount of the working fluid retained within the vessel of the receiver based on the operating mode of the energy efficient heat pump, and the operating mode comprises a heating mode or a cooling mode.

4. The energy efficient heat pump of claim 3, wherein the controller is configured to control the first expansion device and the second expansion device to adjust the amount of the working fluid retained within the vessel of the receiver based on the operating parameter of the HVAC system, wherein the operating parameter comprises a subcooling value of the working fluid, a superheat value of the working fluid, or both.

5. The energy efficient heat pump of claim 4, wherein the first expansion device is disposed along the liquid conduit portion between the first heat exchanger and the receiver, and, in the heating mode, the controller is configured to:receive, via one or more sensors, data indicative of an amount of subcooling of the working fluid exiting the first heat exchanger;compare the amount of subcooling of the working fluid exiting the first heat exchanger to a subcooling set point; andin response to a determination the amount of subcooling of the working fluid exiting the first heat exchanger is greater than the subcooling set point, adjust the first expansion device toward an open position to increase the amount of the working fluid retained within the vessel of the receiver.

6. The energy efficient heat pump of claim 5, wherein the subcooling set point is a first subcooling set point, the second expansion device is disposed along the liquid conduit portion between the second heat exchanger and the receiver, and, in the cooling mode, the controller is configured to:receive, via the one or more sensors, data indicative of an amount of subcooling of the working fluid exiting the second heat exchanger;compare the amount of subcooling of the working fluid exiting the second heat exchanger to a second subcooling set point; andin response to a determination the amount of subcooling of the working fluid exiting the second heat exchanger is less than the second subcooling set point, adjust the second expansion device toward a closed position to decrease the amount of the working fluid retained within the vessel of the receiver.

7. The energy efficient heat pump of claim 6, wherein the second subcooling set point is greater than the first subcooling set point.

8. The energy efficient heat pump of claim 6, wherein the closed position is a first closed position, and, in the heating mode, the controller is configured to:receive, via the one or more sensors, data indicative of an amount of superheat of the working fluid exiting the second heat exchanger;compare the amount of superheat of the working fluid exiting the second heat exchanger to a superheat set point; andin response to a determination the amount of superheat of the working fluid exiting the second heat exchanger is less than the superheat set point, adjust the second expansion device toward a second closed position to increase the amount of the working fluid retained within the vessel of the receiver.

9. The energy efficient heat pump of claim 8, wherein the superheat set point is a first superheat set point, the open position is a first open position, and, in the cooling mode, the controller is configured to:receive, via the one or more sensors, data indicative of an amount of superheat of the working fluid exiting the first heat exchanger;compare the amount of superheat of the working fluid exiting the first heat exchanger to a second superheat set point; andin response to a determination the amount of superheat of the working fluid exiting the first heat exchanger is greater than the second superheat set point, adjust the first expansion device toward a second open position to decrease the amount of the working fluid retained within the vessel of the receiver.

10. The energy efficient heat pump of claim 9, wherein the controller is configured to adjust the first subcooling set point, the second subcooling set point, the first superheat set point, the second superheat set point, or a combination thereof, based on one or more additional operating parameters of the energy efficient heat pump detected by the one or more sensors.

11. The energy efficient heat pump of claim 1, wherein comprises a first dip tube fluidly coupled to the liquid conduit portion and second dip tube fluidly coupled to the liquid conduit portion, wherein the first dip tube and the second dip tube extend from an upper portion of the vessel, into the vessel, and toward a base of the vessel.

12. The energy efficient heat pump of claim 11, wherein a first length of the first dip tube and a second length of the second dip tube are approximately equal to one another.

13. The energy efficient heat pump of claim 1, wherein a first internal working fluid volume of the first heat exchanger is greater than a second internal working fluid volume of the second heat exchanger.

14. An energy efficient heat pump for a heating, ventilation, and air conditioning (HVAC) system, comprising:a working fluid circuit comprising a liquid conduit portion configured to direct a working fluid between a first heat exchanger of the working fluid circuit and a second heat exchanger of the working fluid circuit;a receiver disposed along the liquid conduit portion, wherein the receiver comprises a vessel, a first dip tube fluidly coupled to the liquid conduit portion and extending into the vessel, and a second dip tube fluidly coupled to the liquid conduit portion and extending into the vessel, wherein the first dip tube and the second dip tube are each configured to direct the working fluid from the liquid conduit portion and into the vessel and to direct the working fluid from the vessel to the liquid conduit portion;a first expansion device disposed along the liquid conduit portion between the first heat exchanger and the receiver;a second expansion device disposed along the liquid conduit portion between the second heat exchanger and the receiver; anda controller communicatively coupled to the first expansion device and the second expansion device, wherein the controller is configured to adjust the first expansion device and the second expansion device based on an operating mode of the energy efficient heat pump and based on at least one operating parameter of the working fluid, wherein the controller is configured to regulate an amount of working fluid retained within the vessel of the receiver.

15. The energy efficient heat pump of claim 14, wherein the working fluid circuit comprises a reversing valve configured to adjust a flow direction of the working fluid along the working fluid circuit, the first heat exchanger is configured to transfer heat between the working fluid and a supply air flow, the second heat exchanger configured to transfer heat between the working fluid and an ambient air flow, and wherein:in a heating mode of the energy efficient heat pump, the controller is configured to adjust the first expansion device toward an open position to decrease an amount of subcooling of the working fluid exiting the first heat exchanger and increase the amount of working fluid retained within the vessel; andin a cooling mode of the energy efficient heat pump, the controller is configured to adjust the second expansion device toward a closed position to increase an amount of subcooling of the working fluid exiting the second heat exchanger and decrease the amount of working fluid retained within the vessel.

16. The energy efficient heat pump of claim 15, wherein:in the heating mode of the energy efficient heat pump, the controller is configured to adjust the first expansion device based on a comparison of a detected amount of subcooling of the working fluid exiting the first heat exchanger and a first subcooling set point; andin the cooling mode of the energy efficient heat pump, the controller is configured to adjust the second expansion device based on a comparison of a detected amount of subcooling of the working fluid exiting the second heat exchanger and a second subcooling set point,wherein the first subcooling set point is less than the second subcooling set point.

17. The energy efficient heat pump of claim 15, wherein:in the heating mode of the energy efficient heat pump, the controller is configured to adjust the second expansion device toward an additional closed position to increase an amount of superheat of the working fluid exiting the second heat exchanger and increase the amount of working fluid retained within the vessel; andin a cooling mode of the energy efficient heat pump, the controller is configured to adjust the first expansion device toward an additional open position to decrease an amount of superheat of the working fluid exiting the first heat exchanger and decrease the amount of working fluid retained within the vessel.

18. The energy efficient heat pump of claim 14, wherein the first dip tube and the second dip tube each extend within the vessel from an upper portion of the vessel toward a base of the vessel along at least 50 percent of a height of the vessel.

19. The energy efficient heat pump of claim 14, wherein the first expansion device is a first bi-directional electronic expansion valve, and the second expansion device is a second bi-directional electronic expansion valve.

20. An energy efficient heat pump, comprising: a working fluid circuit configured to circulate a working fluid therethrough;a first heat exchanger disposed along the working fluid circuit and configured to transfer heat between the working fluid and a supply air flow in a heating mode and in a cooling mode of the energy efficient heat pump;a second heat exchanger disposed along the working fluid circuit and configured to transfer heat between the working fluid and an ambient air flow in the heating mode and the cooling mode;a liquid conduit portion of the working fluid circuit extending between the first heat exchanger and the second heat exchanger;a receiver disposed along the liquid conduit portion, wherein the receiver comprises a vessel, a first dip tube fluidly coupled to the liquid conduit portion and extending into the vessel, and a second dip tube fluidly coupled to the liquid conduit portion and extending into the vessel;a first electronic expansion valve disposed along the liquid conduit portion between the first heat exchanger and the first dip tube;a second electronic expansion valve disposed along the liquid conduit portion between the second heat exchanger and the second dip tube; anda controller communicatively coupled to the first electronic expansion valve and the second electronic expansion valve, wherein the controller is configured to adjust the first electronic expansion valve and the second electronic expansion valve based on data indicative of an amount of subcooling of the working fluid and data indicative of an amount of superheat of the working fluid to adjust an amount of the working fluid retained within the vessel in the heating mode and in the cooling mode.

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