Expansion system and heat pump incorporating the same

Abstract

A heat pump includes a refrigeration circuit. The heat pump includes a compressor configured to move refrigerant through the refrigeration circuit. The heat pump includes an expansion system fluidly coupled with the refrigeration circuit via a first valve. The heat pump includes control circuitry configured to control the first valve to selectively provide fluid communication of the refrigerant between the refrigeration circuit and the expansion system.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Canadian Patent Application No. 3,228,039, filed on Feb. 2, 2024, entitled “EXPANSION SYSTEM AND HEAT PUMP INCORPORATING THE SAME,” the disclosure of which is hereby incorporated herein by reference in its entirety. This application claims priority to and the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 63 / 622,787, filed on Jan. 19, 2024, entitled “EXPANSION SYSTEM AND HEAT PUMP INCORPORATING THE SAME,” the disclosure of which is hereby incorporated herein by reference in its entirety.FIELD OF THE DISCLOSURE

[0002] The present disclosure generally relates to an expansion system and a heat pump incorporating the same and, more particularly, to a water heater having a heat pump that allows refrigerant in the heat pump to expand in high-pressure conditions.BACKGROUND OF THE DISCLOSURE

[0003] Conventional heat pump systems are typically shipped without refrigerant due to the potential for the refrigerant to expand during shipment. There is a need for a dynamic system that allows for expansion of the refrigerant during shipping and / or during operation of the heat pump.SUMMARY OF THE DISCLOSURE

[0004] According to one aspect, a heat pump includes a refrigeration circuit. The heat pump includes a compressor configured to move refrigerant through the refrigeration circuit. The heat pump includes an expansion system fluidly coupled with the refrigeration circuit via a first valve. The heat pump includes control circuitry configured to control the first valve to selectively provide fluid communication of the refrigerant between the refrigeration circuit and the expansion system.

[0005] According to another aspect, a method for operating a heat pump having an expansion system includes a method for controlling a heat pump having an expansion system. The method includes closing a suction valve upstream of the expansion system, operating a compressor of a refrigeration circuit to draw refrigerant from the expansion system through a control valve, opening the suction valve based on a pressure of the refrigeration circuit, and closing fluid communication between the refrigeration circuit and the expansion system.

[0006] According to yet another aspect, a heat pump water heater includes a refrigeration circuit. The heat pump includes carbon-dioxide refrigerant disposed in the refrigeration circuit. The heat pump includes an expansion tank configured to store the carbon-dioxide refrigerant in response to pressure of the refrigeration circuit exceeding a pressure threshold. The heat pump includes a normally-open expansion circuit fluidly interposing the refrigeration circuit and the expansion tank.

[0007] These and other features, advantages, and objects of the present disclosure will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In the drawings:

[0009] FIG. 1 is a perspective view of a heat pump incorporating an expansion system according to one aspect of the present disclosure;

[0010] FIG. 2 is a fluid processing schematic of a heat pump incorporating an expansion system according to one aspect of the present disclosure;

[0011] FIG. 3 is a functional block diagram of a control system for a heat pump according to one aspect of the present disclosure; and

[0012] FIG. 4 is a flow diagram of a method for operating a heat pump having an expansion system; and

[0013] FIG. 5 is a flow diagram of a method for operating a heat pump having an expansion system.

[0014] The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles described herein.DETAILED DESCRIPTION

[0015] The present illustrated embodiments reside primarily in combinations of method steps and apparatus components related to an expansion system and heat pump incorporating the same. Accordingly, the apparatus components and method steps have been represented, where appropriate, by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Further, like numerals in the description and drawings represent like elements.

[0016] The terms “including,”“comprises,”“comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by “comprises a . . . ” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0017] Referring generally to FIGS. 1-3, reference numeral 10 generally designates a heat pump. In general, the heat pump 10 incorporates a heat exchange system that allows for refrigerant to expand in extreme temperatures. The heat pump 10 further limits installation costs for third parties to commission the heat pump 10 by limiting the need for refrigerant to be added to the heat pump 10 during / after commissioning. The heat exchange system can also provide for enhanced operation of the heat pump 10 by allowing expansion of refrigerant during an off state, an inoperability state, or another state of the heat pump 10. The system further provides for optimized refrigerant usage by providing a purging feature for refrigerant expanded into an expansion area of the heat pump 10.

[0018] With continued reference to FIGS. 1-3, the heat pump 10 includes a refrigeration circuit 12 and a compressor 14 configured to move refrigerant through the refrigeration circuit 12. The heat pump 10 also includes an expansion system 16 that is fluidly coupled with the refrigeration circuit 12 via a valve 18. Control circuitry 20 is configured to control the valve 18 to selectively provide fluid communication of the refrigerant between the refrigeration circuit 12 and the expansion system 16. The expansion system 16 can also include a tank 22 for storing the refrigerant when the refrigerant is expanded (e.g., due to high ambient temperature). As will be further described herein, the control circuitry 20 can be configured to control the valve 18 based on one or more conditions of the refrigeration circuit 12, such as pressure, temperature, flow rate, or another condition of the refrigeration circuit 12. In some examples, the valve 18 is a portion of a normally-open expansion circuit fluidly interposing the refrigeration circuit 12 and the expansion tank 22. The normally-open expansion circuit can be fluidly coupled with the refrigeration circuit 12 upstream of the compressor 14.

[0019] Referring now to FIG. 1, a water heater 24 incorporating the heat pump 10 is provided in an environment 26 external to a facility 28. In some examples, the water heater 24 is provided in an internal environment 30 (e.g., within an interior of the facility 28). The water heater 24 can receive a water supply from the facility 28 and provide heated water to the facility 28. The water heater 24 can include or be in fluid communication with a hot water tank system for storing hot water. The water heater 24 includes a housing 32 that houses the various components of the heat pump 10 and defines inlet and outlet ports 34 configured to receive inlet and outlet piping for the water. A user interface 36, such as a disconnect switch, a touchscreen, buttons, switches, or any combination thereof can be provided on the housing 32 to allow an external observer to control and / or view various parameters of the water heater 24. For example, ambient conditions and / or operational conditions, such as pressure information, temperature information, flow rates, electrical properties, or any other quality may be displayed at the user interface. The water heater 24 includes a control panel 38 that is accessible by an external user to view and / or operate parameters of the water heater 24.

[0020] The control circuitry 20 configured to control the heat pump 10 is disposed in the housing 32 and may be accessible via the control panel 38. For example, the control circuitry 20 can include one or more controllers 40 (e.g., a programmable logic device (PLD)) configured to control operation of the heat pump 10 and other components of the water heater 24. In addition or as an alternative, the control circuitry 20 can include any digital or analog communication channels (e.g., nodes or wires) that can be monitored and / or controlled by a control device to read from and / or write to devices of the water heater 24.

[0021] Referring now to FIG. 2, the heat pump 10 can include a heat exchange system configured to warm fluid (e.g., water) provided via piping. For example, a supply line 42 may provide water to be warmed by the heat exchanger and a return line 44 may provide warm water to a water storage tank local to or remote from the water heater 24. The heat pump 10 heats the water via thermal exchange with the refrigeration circuit 12. The refrigeration circuit 12 can be a closed system that transfers heat from the environment 26 (e.g., air in a region exterior to the water heater 24) to the water using refrigerant to carry the heat. The heat exchanger includes a compressor 14, a first heat exchanger 46 (e.g., a gas cooler heat exchanger), an expansion device (e.g., an expansion valve 48), and a second heat exchanger 50 (e.g., an evaporator) each disposed along the refrigeration circuit 12. The refrigeration circuit 12 can also include a third heat exchanger 52 (e.g., a recuperator) for optimizing heat transfer between parts of the refrigeration circuit 12, or refrigerant loop.

[0022] In operation, the compressor 14 pressurizes refrigerant, increasing its temperature and energy. The high-pressure, high-temperature refrigerant then flows into the first heat exchanger 46, where it releases heat into the water to provide hot water to the facility 28 (e.g., hot water tanks). The refrigerant then passes through the expansion valve 48, which restricts its flow and reduces its pressure. As the refrigerant expands, the temperature of the refrigerant lowers. It is contemplated that the refrigerant may pass through the third heat exchanger 52 between the first heat exchanger 46 and the expansion valve 48 to transfer more heat from one portion to another portion of the refrigeration circuit 12. Because the refrigerant may be carbon dioxide in some examples, the refrigerant can be supercritical along one or more parts of the refrigeration circuit 12.

[0023] With continued reference to FIG. 2, the low-pressure refrigerant enters the second heat exchanger 50, which may include one or more blowers / fans that draw air across evaporator coils. As the air from the environment 26 passes over evaporator coils, heat is transferred from the air to the refrigerant thereby causing the refrigerant to warm and evaporate. A separator 54 is provided between the second heat exchanger 50 and the compressor 14 to limit liquid, or otherwise higher-density parts of the refrigerant from returning to the compressor 14 (e.g., providing gas, or lower density-refrigerant, to an intake of the compressor 14). The refrigerant then flows to the compressor 14 to repeat the refrigeration cycle. In general, the directional arrows of FIG. 2 point in the direction of flow, such that a first component is upstream of a second component if refrigerant flows from the first component toward the second component.

[0024] The refrigerant employed in the present system can be carbon dioxide or another refrigerant. When employing carbon dioxide refrigerant, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are limited. The use of carbon dioxide can provide for higher efficiency of the heat pump 10 but requires high pressure. The expansion system 16 (detailed below) is operable with carbon dioxide refrigerant to limit high-pressure conditions occurring in response to high temperatures.

[0025] With continued reference to FIG. 2, the heat exchanger can include an expansion system 16 fluidly connected with the refrigeration circuit 12 between the second heat exchanger 50 and the compressor 14. The expansion system 16 includes an expansion tank 22 in fluid communication with the refrigeration circuit 12 via a control valve 18 (e.g., expansion tank 22 valve). When the control valve 18 is open, refrigerant traveling toward the compressor 14 (e.g., via an interposing line 56, or interposing conduit 56) can move into the expansion tank 22. For example, in high temperature / pressure conditions, the refrigerant can expand into the expansion tank 22 when the control valve 18 is in an open position, thereby limiting components of the heat pump 10 (e.g., one or more of the heat exchangers 46, 50, 52, the compressor 14, tubing, valves, sensors, or any other component in the heat pump 10) from high-pressure conditions. When closed, the control valve 18 cuts off fluid communication from the refrigeration circuit 12 to the expansion tank 22.

[0026] While demonstrated in connection with the interposing line 56, it is contemplated that the expansion tank 22 can connect to the refrigeration circuit 12 at various locations (e.g., fluid connection locations) of the refrigeration circuit 12. In the present example, the expansion system 16 is connected between the separator 54 and the third heat exchanger 52 to allow the refrigerant stored in the separator 54 to flow into the expansion tank 22 at high temperatures. Stated another way, by providing the expansion system 16 fluidly proximate to the separator 54 and the second heat exchanger 50, the refrigerant that is evaporated under high temperature can pass into the expansion system 16 before expanding into other components (e.g., the compressor 14, the gas cooler 46, the third heat exchanger 52, etc.). It is contemplated that other connections to the expansion tank 22 (e.g., additional control valves 18) could be provided for coupling the refrigerant to the expansion tank 22 along various portions of the refrigeration circuit 12.

[0027] With continued reference to FIG. 2, the control valve 18 can be normally-open. For example, the control valve 18 can control the normally-open expansion circuit that fluidly interposes the expansion tank 22 and the refrigeration circuit 12 upstream of the compressor 14. By way of example, the normally-open circuit can be disposed between the separator 54 and the compressor 14. More particularly, the normally-open circuit can be disposed between the separator 54 and the third heat exchanger 52. In some examples, the control valve 18 is additionally, or alternatively, spring-return, such that when the control valve 18 receives an electrical signal from the control circuitry 20, the control valve 18 closes, and when the electrical signal is not present, the control valve 18 returns to the open position. In this way, the default position of the control valve 18 is open to allow the refrigerant to expand into the expansion tank 22 when there is no electrical power to the heat pump 10 or the control circuitry 20. Thus, when the water heater 24 or the heat pump 10 is shipped to an installation site, the influence of large temperature fluctuations (e.g., very high temperatures) on components of the heat pump 10 that can occur during shipping can be limited.

[0028] Some high-pressure conditions resolved by the expansion system 16 can occur during operation of the heat pump 10. For example, a rooftop-installed water heater 24 in a warm climate (e.g., exposed to sunlight) can present high temperatures that are handled by controlling the control valve 18 to allow the refrigerant to expand. Accordingly, the expansion system 16 can be operated for an initializing phase (e.g., during the commissioning of the water heater 24), after a power cycle of the water heater 24, or periodically during operation of the water heater 24.

[0029] A suction valve 58 is also provided along the refrigeration circuit 12 between the separator 54 and the expansion system 16. The suction valve 58 can be normally-open and / or spring-return. The suction valve 58 may also be controlled by the control circuitry 20 to open or close based on the condition of the system. For example, to draw refrigerant that is stored in the expansion tank 22 into the refrigeration circuit 12, the control circuitry 20 can activate the compressor 14 and close the suction valve 58 to create suction from the expansion system 16 into the interposing conduit 56. During normal operation (e.g., no or limited refrigeration in the expansion tank 22), the suction valve 58 can be opened to allow evaporated refrigerant to enter the interposing conduit 56 from the separator 54.

[0030] Referring now to FIGS. 2 and 3, one or more sensors 60, 62 can be monitored by the control circuitry 20 to allow the control circuitry 20 to actively or passively control the control valve 18. For example, a temperature sensor 60 and / or a pressure sensor 62 can be monitored by the control circuitry 20. The pressure sensor 62 can be analog or digital. In the present example the pressure sensor 62 is a pressure switch that closes upon the pressure of the refrigeration circuit 12 exceeding a pressure threshold (e.g., 15 bar), though in some examples, the control circuitry 20 can actively read the pressure and perform algorithmic comparison on data read from the sensor 62. The temperature sensor 60 can include any temperature sensing device such as a thermometer, thermocouple, or any the temperature sensing device that can communicate the temperature of the external air to the control circuitry 20. Based on the ambient air temperature and / or the pressure of the refrigeration circuit 12, the control circuitry 20 can control the control valve 18, the suction valve 58, the compressor 14 (via, e.g., variable-frequency control of a motor driving the compressor 14), or any other valve or electrical output component of the heat pump 10.

[0031] Referring now to FIG. 3, the control circuitry 20 includes a controller 40 that is in communication with the pressure sensor 62, the temperature sensor 60, the compressor 14 (via, e.g., a motor control device), the suction valve 58, the expansion valve 48, and the control valve 18. As previously described, the controller 40 can be in communication with other valves or devices for monitoring or controlling conditions of the heat pump 10. In general, the expansion system 16 can be operated in a powered condition and an unpowered condition. In the unpowered condition, the control circuitry 20 is not powered and therefore does not control the expansion system 16 or other components of the heat pump 10. As a result, the control valve 18 and the suction valve 58 are open and, in high temperature or pressure, the refrigerant can expand into the expansion tank 22 from the separator 54. For example, as the liquid refrigerant warms and expands, the refrigerant can pass through the suction valve 58 and into the expansion tank 22 via the control valve 18.

[0032] In the powered condition, the control circuitry 20 can receive pressure or temperature data, or both, via the one or more sensors 60, 62 to classify the condition of the refrigeration circuit 12. Based on the condition, the control circuitry 20 is configured to communicate electrical signals (or omit electrical signals) to the control valve 18 and the suction valve 58 to open the control valve 18 and the suction valve 58. This can isolate the expansion system 16 to allow the compressor 14 to draw the refrigerant from the expansion system 16. The control circuitry 20 can also communicate a signal (or omit a signal) to close the expansion valve 48, thereby increasing a significant draw force on the expansion system 16. The control circuitry 20 is further configured to communicate an electrical signal or instruction to activate the compressor 14.

[0033] In this stage, the compressor 14 is configured to run and draw refrigerant from the expansion system 16 until the condition changes. For example, when the condition of the heat pump 10 (e.g., the pressure of the refrigeration circuit 12 or the ambient temperature of the air) surpasses a condition threshold (e.g., a minimum pressure), the control circuitry 20 is configured to close the control valve 18, then deactivate the compressor 14, then open the suction valve 58. In this way, the control circuitry 20 can introduce the stored refrigerant into the refrigeration circuit 12. It is contemplated that the algorithm executed by the controller 40 to introduce refrigerant into the refrigeration circuit 12 may be executed upon commissioning of the system or during normal operation, such that when pressure exceeds a certain threshold, the controller 40 can control the expansion system 16 and surrounding components to draw the refrigerant from the expansion tank 22.

[0034] Referring now to FIG. 4, a method 400 for operating a heat pump 10 includes closing a suction valve 58 upstream of the expansion system 16 at step 402. The method 400 includes operating a compressor 14 of a refrigeration circuit 12 to draw refrigerant from the expansion system 16 through the control valve 18 at step 404. The method 400 includes opening the suction valve 58 based on a pressure of the refrigeration circuit 12 at step 406. For example, the method 400 can also include a step of opening the suction valve 58 based on the pressure of the refrigeration circuit 12 being below a pressure threshold. The method 400 includes closing fluid communication between the refrigeration circuit 12 and the expansion system 16 at step 408.

[0035] In operation, the control circuitry 20 can be configured to carry out the steps of the method 400 in an initialization sequence or a general pressure relief sequence. For example, the control circuitry 20 can communicate signals, or omit signals, to the components of the heat pump 10 to draw the refrigerant from the expansion tank 22 by pressurizing the interposing conduit 56. In some examples, additional suction force is provided to draw the refrigerant from the expansion system 16 by closing, or maintaining closure of, the expansion valve 48 downstream of the compressor 14 when the suction valve 58 is closed. By closing one or both of the expansion valve 48 and the suction valve 58 while running the compressor 14, additional suction pressure can be applied to the interposing conduit 56 to optimize drawing the refrigerant from the expansion system 16. Once the pressure of the refrigeration circuit 12 is below the pressure threshold, the control circuitry 20 can control the suction valve 58 to open and the control valve 18 to close. The method 400 can follow a power cycle of the heat pump 10, or initial powering on of the heat pump 10, to optimize the amount of refrigerant in the refrigeration circuit 12. In some examples, the method 400 is initiated in response to an interrupt condition, such as a pressure or temperature level of the refrigeration circuit 12 exceeding a pressure threshold or temperature threshold, that can occur during normal operation of the heat pump 10.

[0036] Referring now to FIG. 5, a method 500, which may be standalone or in combination with the method 400, for operating a heat pump 10 includes detecting pressure below a pressure threshold at step 502. For example, the pressure sensor 62 can communicate a signal to the control circuitry 20 indicative of the pressure or the pressure exceeding a set threshold. At step 504, the method 500 provides for closing the control valve 18 in response to the pressure being below a pressure threshold. Also in response to the pressure being below the pressure threshold, the method 500 provides for deactivating the compressor 14 at step 506. At step 508, the method 500 includes opening the suction valve 58. Steps 504, 506, 508 may be performed in order (step 504, then step 506, then step 508) or out of order. In general, these operations can transition the heat pump 10 from initialization to normal operation without overpressure conditions and can be performed following the method 400. Similar to the method 400, method 500 may be performed using the control circuitry 20 to control the components of the heat pump 10. The combination of methods 400, 500 may be completed in any duration, such as in seconds, minutes, or hours. In one example, the methods 400, 500 can occur over seconds or minutes. For example, the volume of refrigerant stored in the expansion tank 22 can be drawn from the expansion tank 22 within seconds or minutes. In this way, the heat pump 10 of the present disclosure can provide enhanced pressure management and commissioning.

[0037] In general, the heat pump 10 and expansion system 16 of the present disclosure can provide for a pre-charged system to be provided upon commission of the water heater 24. For example, the operating volume of refrigerant can be equal to the volume of refrigerant in the refrigeration circuit 12 together with the volume of refrigerant in the expansion tank 22. The expansion system 16 further allows the water heater 24 with the heat pump 10 to be shipped without unwanted relief of pressure via pressure relief valves. For packaged heat pumps, the traditional relief-valve method of venting to relieve pressure has the disadvantage of venting a large percentage of the charge, which can result in performance loss for the user. The heat pump 10 of the present system therefore provides for the expansion of refrigerant, thereby limiting pressures below that of pressure relief valve settings. Further, the control valve 18 selectively provides access to additional volume for the refrigerant, thereby limiting the pressure the refrigerant can achieve to the refrigerant evaporating, which can occur during a standby or completely unpowered condition when the system is exposed to high ambient temperatures.

[0038] The systems and methods of the present disclosure can be constructed according to one or more combinations of the following features:

[0039] According to one aspect, a heat pump includes a refrigeration circuit. The heat pump includes a compressor configured to move refrigerant through the refrigeration circuit. The heat pump includes an expansion system fluidly coupled with the refrigeration circuit via a first valve. The heat pump includes control circuitry configured to control the first valve to selectively provide fluid communication of the refrigerant between the refrigeration circuit and the expansion system.

[0040] According to one aspect, the expansion system includes an expansion tank configured to store the refrigerant.

[0041] According to one aspect, the first valve fluidly interposes the refrigeration circuit and the expansion tank.

[0042] According to one aspect, the heat pump includes a sensor configured to detect a condition of the refrigeration circuit, wherein the control circuitry is configured to control the first valve in response to the condition of the refrigeration circuit.

[0043] According to one aspect, the condition includes a pressure of the refrigeration circuit.

[0044] According to one aspect, the control circuitry is configured to communicate a signal to close the first valve when the pressure is below a pressure threshold.

[0045] According to one aspect, the control circuitry is configured to control the valve to open when the pressure is at or above the pressure threshold.

[0046] According to one aspect, the heat pump includes a second valve in series with the first valve via an interposing conduit in fluid communication with the refrigeration circuit.

[0047] According to one aspect, the second valve is normally open.

[0048] According to one aspect, the control circuitry is configured to control the first valve and the second valve based on the pressure of the refrigeration system.

[0049] According to one aspect, the valve is fluidly coupled with the refrigeration circuit upstream of the compressor.

[0050] According to one aspect, the heat pump includes a gas cooler heat exchanger for transferring heat from the refrigerant to a water supply.

[0051] According to one aspect, the first valve is normally open.

[0052] According to one aspect, the refrigerant is carbon dioxide.

[0053] According to another aspect, a method for operating a heat pump having an expansion system includes a method for controlling a heat pump having an expansion system. The method includes closing a suction valve upstream of the expansion system, operating a compressor of a refrigeration circuit to draw refrigerant from the expansion system through a control valve, opening the suction valve based on a pressure of the refrigeration circuit, and closing fluid communication between the refrigeration circuit and the expansion system.

[0054] According to one aspect, opening the suction valve is based further on the pressure of the refrigeration circuit being below a pressure threshold.

[0055] According to one aspect, the method includes closing an expansion valve downstream of the compressor when the suction valve is closed.

[0056] According to one aspect, the method includes, in response to the pressure being below a pressure threshold, closing the control valve, deactivating the compressor, and opening the suction valve.

[0057] According to yet another aspect, a heat pump for a water heater includes a refrigeration circuit. The heat pump includes carbon-dioxide refrigerant disposed in the refrigeration circuit. The heat pump includes an expansion tank configured to store the carbon-dioxide refrigerant in response to pressure of the refrigeration circuit exceeding a pressure threshold. The heat pump includes a normally-open expansion circuit fluidly interposing the refrigeration circuit and the expansion tank.

[0058] According to one aspect, the heat pump includes a compressor configured to pressurize the carbon-dioxide refrigerant, wherein the normally-open expansion circuit is coupled with the refrigeration circuit upstream of the compressor.

[0059] According to one aspect, a heat pump includes a refrigeration circuit and a compressor configured to move refrigerant through the refrigeration circuit. The heat pump includes an expansion system fluidly coupled with the refrigeration circuit via a valve. The heat pump includes control circuitry configured to control the valve to selectively draw refrigerant from the refrigeration circuit into the expansion system.

[0060] According to one aspect, a heat pump includes a refrigeration circuit and a sensor configured to detect a condition of the refrigeration circuit. The heat pump includes an expansion system including a tank and a valve fluidly coupling the tank with the refrigeration circuit. The valve has an open position and a closed position. The heat pump includes control circuitry configured to control the valve in response to the condition of the refrigeration circuit.

[0061] According to one aspect, the control circuitry is configured to control the valve to open the valve when the condition is low pressure.

[0062] According to one aspect, the control circuitry is configured to communicate a signal to close the valve in response to a pressure of the refrigeration circuit being above a pressure threshold.

[0063] According to one aspect, a water heater incorporates a heat pump and an expansion system constructed according to any aspects of the present disclosure.

[0064] It will be understood by one having ordinary skill in the art that construction of the described disclosure and other components is not limited to any specific material. Other exemplary embodiments of the disclosure disclosed herein may be formed from a wide variety of materials, unless described otherwise herein.

[0065] For purposes of this disclosure, the term “coupled” (in all of its forms, couple, coupling, coupled, etc.) generally means the joining of two components (electrical or mechanical) directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two components (electrical or mechanical) and any additional intermediate members being integrally formed as a single unitary body with one another or with the two components. Such joining may be permanent in nature or may be removable or releasable in nature unless otherwise stated.

[0066] It is also important to note that the construction and arrangement of the elements of the disclosure as shown in the exemplary embodiments is illustrative only. Although only a few embodiments of the present innovations have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes, and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited. For example, elements shown as integrally formed may be constructed of multiple parts or elements shown as multiple parts may be integrally formed, the operation of the interfaces may be reversed or otherwise varied, the length or width of the structures and / or members or connector or other elements of the system may be varied, the nature or number of adjustment positions provided between the elements may be varied. It should be noted that the elements and / or assemblies of the system may be constructed from any of a wide variety of materials that provide sufficient strength or durability, in any of a wide variety of colors, textures, and combinations. Accordingly, all such modifications are intended to be included within the scope of the present innovations. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the desired and other exemplary embodiments without departing from the spirit of the present innovations.

[0067] It will be understood that any described processes or steps within described processes may be combined with other disclosed processes or steps to form structures within the scope of the present disclosure. The exemplary structures and processes disclosed herein are for illustrative purposes and are not to be construed as limiting.

Claims

1. A heat pump, comprising:a refrigeration circuit;a compressor configured to move refrigerant through the refrigeration circuit;an expansion system fluidly coupled with the refrigeration circuit via a first valve; andcontrol circuitry configured to control the first valve to selectively provide fluid communication of the refrigerant between the refrigeration circuit and the expansion system.

2. The heat pump of claim 1, wherein the expansion system includes an expansion tank configured to store the refrigerant.

3. The heat pump of claim 2, wherein the first valve fluidly interposes the refrigeration circuit and the expansion tank.

4. The heat pump of claim 1, further comprising:a sensor configured to detect a condition of the refrigeration circuit, wherein the control circuitry is configured to control the first valve in response to the condition of the refrigeration circuit.

5. The heat pump of claim 4, wherein the condition includes a pressure of the refrigeration circuit.

6. The heat pump of claim 5, wherein the control circuitry is configured to communicate a signal to close the first valve when the pressure is below a pressure threshold.

7. The heat pump of claim 6, wherein the control circuitry is configured to control the first valve to open when the pressure is at or above the pressure threshold.

8. The heat pump of claim 5, further comprising:a second valve in series with the first valve via an interposing conduit in fluid communication with the refrigeration circuit.

9. The heat pump of claim 8, wherein the second valve is normally open.

10. The heat pump of claim 9, wherein the control circuitry is configured to:control the first valve and the second valve based on the pressure of the refrigeration circuit.

11. The heat pump of claim 8, wherein the first valve is fluidly coupled with the refrigeration circuit upstream of the compressor.

12. The heat pump of claim 1, further comprising:a gas cooler heat exchanger for transferring heat from the refrigerant to a water supply.

13. The heat pump of claim 12, wherein the refrigerant is carbon dioxide.

14. The heat pump of claim 1, wherein the first valve is normally open.

15. A method for operating a heat pump having an expansion system, comprising:closing a suction valve upstream of the expansion system;operating a compressor of a refrigeration circuit to draw refrigerant from the expansion system through a control valve;opening the suction valve based on a pressure of the refrigeration circuit; andclosing fluid communication between the refrigeration circuit and the expansion system.

16. The method of claim 15, wherein opening the suction valve is based further on the pressure of the refrigeration circuit being below a pressure threshold.

17. The method of claim 15, further comprising:closing an expansion valve downstream of the compressor when the suction valve is closed.

18. The method of claim 15, further comprising:in response to the pressure being below a pressure threshold, closing the control valve, deactivating the compressor, and opening the suction valve.

19. A heat pump water heater, comprising:a refrigeration circuit;carbon-dioxide refrigerant disposed in the refrigeration circuit;an expansion tank configured to store the carbon-dioxide refrigerant in response to pressure of the refrigeration circuit exceeding a pressure threshold; anda normally-open expansion circuit fluidly interposing the refrigeration circuit and the expansion tank.

20. The heat pump water heater of claim 19, further comprising:a compressor configured to pressurize the refrigerant carbon-dioxide, wherein the normally-open expansion circuit is coupled with the refrigeration circuit upstream of the compressor.

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