Heating, ventilation, air conditioning, and / or refrigeration (hvac&r) systems and method of controlling the same

Abstract

A heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system includes a refrigeration circuit with an evaporator, a compressor, and a condenser that circulate refrigerant and facilitate heat exchange between the refrigerant and a conditioning fluid. A pre-rotation vane (PRV) is at an inlet of the compressor, a variable geometry diffuser (VGD) is at an outlet of the compressor, or both. Control circuitry selectively operates the HVAC&R system in a normal cooling mode or a free cooling mode. In the normal cooling mode, the control circuitry controls the compressor in an active state to compress the refrigerant. In the free cooling mode, the control circuitry controls the compressor in an inactive state such that the refrigerant is circulated through compressor via a pressure difference generator. The control circuity adjusts the PRV, the VGD, or both to control a cooling capacity of the HVAC&R system in the free cooling mode.

Description

[0001] HEATING, VENTILATION, AIR CONDITIONING, AND / OR REFRIGERATION (HVAC&R) SYSTEMS AND METHOD OF CONTROLLING THE SAME

[0002] CROSS-REFERENCE TO RELATED APPLICATION

[0003] This application claims priority from and the benefit of U.S. Provisional Patent Application No. 63 / 529,112, filed on July 26, 2023, which is hereby incorporated by reference in its entirety for all purposes.

[0004] BACKGROUND

[0005] The present disclosure relates generally to heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) systems. More particularly, the present disclosure relates to capacity control for an HVAC&R system operating in free cooling / heating mode.

[0006] Many applications exist for HVAC&R systems including residential, commercial, and industrial applications. For example, a commercial HVAC&R system may be used to cool or heat an enclosed space. Very generally, an HVAC&R system may include circulating a fluid through a closed loop between an evaporator where the fluid absorbs heat and a condenser where the fluid releases heat. The fluid flowing within the closed loop is generally formulated to undergo phase changes within the normal operating temperatures and pressures of the system so that considerable quantities of heat can be exchanged by virtue of the latent heat of vaporization of the fluid.

[0007] In applications where an HVAC&R system is used for cooling, the HVAC&R system can be operated in a free cooling mode when ambient temperatures are low. In the free cooling mode, the low ambient temperature is exploited to provide cooling without the need for an additional energy input from, for example, a compressor. Similarly, in applications where an HVAC&R system is used for heating, the HVAC&R system can be operated in a free heating mode when ambient temperatures are high. In the free heating mode, the high ambient temperature is exploited to provide heating without the need for the additional energy input. Though leveraging ambient temperature in free cooling / heating mode increases HVAC&R operating efficiency, ambient temperature may not always remain constant, and thus may impact a cooling / heating capacity of the HVAC&R system. However, in the HVAC&R system, it may be difficult to control an amount of cooling / heating provided during the free cooling / heating mode.

[0008] In light of the foregoing, it is now recognized that there is a need to control the cooling / heating capacity of the HVAC&R system in accordance with the ambient temperature.

[0009] SUMMARY

[0010] In an embodiment, a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system includes a refrigeration circuit with an evaporator, a compressor, and a condenser that circulate refrigerant and facilitate heat exchange between the refrigerant and a conditioning fluid. A pre-rotation vane (PRV) is at an inlet of the compressor, a variable geometry diffuser (VGD) is at an outlet of the compressor, or both. Control circuitry selectively operates the HVAC&R system in a normal cooling mode or a free cooling mode. In the normal cooling mode, the control circuitry controls the compressor in an active state to compress the refrigerant. In the free cooling mode, the control circuitry controls the compressor in an inactive state such that the refrigerant is circulated through compressor via a pressure difference generator. The control circuity adjusts the PRV, the VGD, or both to control a cooling capacity of the HVAC&R system in the free cooling mode.

[0011] In an embodiment, a method of controlling a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system comprising a refrigeration circuit including an evaporator, a compressor, and a condenser configured to circulate refrigerant and facilitate heat exchange between the refrigerant and a conditioning fluid is provided. The method includes selectively operating, via control circuitry, the HVAC&R system in a normal cooling mode or a free cooling mode. In the free cooling mode, a compression operation of the compressor is inactive, and the refrigerant is circulated through the compressor. In the normal cooling mode, the compression operation of the compressor is active, and the refrigerant is motivated through the refrigerant circuit by the compressor. The method includes adjusting, via the control circuitry, a pre-rotation vane (PRV) at an inlet of the compressor and / or the variable geometry diffuser (VGD) to control a cooling capacity of the HVAC&R system in the free cooling mode.

[0012] In an embodiment, a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system includes a compressor comprising a pre-rotation vane (PRV) at an inlet of the compressor, a variable geometry diffuser (VGD) at an outlet of the compressor, or both. Control circuitry selectively operates the HVAC&R system in a normal heating mode or a free heating mode. In the free heating mode, the control circuitry is configured to control the compressor in an inactive state such that refrigerant is circulated through the compressor by a pressure difference generator. In the normal heating mode, the control circuity is configured to control the compressor in an active state such that the refrigerant is circulated by the compressor. The control circuity is configured to adjust the PRV, the VGD, or both to control a heating capacity of the HVAC&R system in the free heating mode.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Various objects, aspects, features, and advantages of the disclosure will become more apparent and better understood by referring to the detailed description taken in conjunction with the accompanying drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements.

[0015] FIG. 1 is a perspective view of an environment for a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system in a building for a typical commercial setting, in accordance with an embodiment of the present disclosure;

[0016] FIG. 2 is a block diagram of a vapor compression system that can be used in the HVAC&R system of FIG. 1, in accordance with an embodiment of the present disclosure; FIG. 3 is a block diagram of a vapor compression system with an intermediate circuit incorporated between a condenser and an expansion device, in accordance with an embodiment of the present disclosure;

[0017] FIG. 4 is a block diagram that illustrates an exemplary embodiment of a vapor compression system that can be used in the HVAC&R system of FIG. 1, in accordance with an embodiment of the present disclosure;

[0018] FIG. 5 is perspective view of a compressor of FIG. 4 driven by a motor, in accordance with an embodiment of the present disclosure;

[0019] FIG. 6A is a block diagram of the vapor compression system of FIG. 4 operating in a normal cooling mode, in accordance with an embodiment of the present disclosure;

[0020] FIG. 6B is a block diagram of the vapor compression system of FIG. 4 operating in a free cooling mode, in accordance with an embodiment of the present disclosure;

[0021] FIGS. 7A and 7B are block diagrams of a vapor compression system that can be used in the HVAC&R system of FIG. 1, in accordance with an embodiment of the present disclosure;

[0022] FIG. 8 is a flow chart of a method to control cooling capacity of an HVAC&R system (e.g., chiller) operating in a free cooling mode, in accordance with an embodiment of the present disclosure;

[0023] FIG. 9 is a flow chart of a method to control heating capacity of an HVAC&R system (e.g., boiler) operating in a free heating mode, in accordance with an embodiment of the present disclosure;

[0024] FIGS. 10A and 10B are collectively a flow chart of a method to control cooling capacity of an HVAC&R system (e.g., heat pump) during free cooling mode and free heating mode, in accordance with an embodiment of the present disclosure; and FIG. 11 is a flow chart of a method to prevent conditioning fluid from freezing in evaporator of an HVAC&R system, in accordance with an embodiment of the present disclosure.

[0025] DETAILED DESCRIPTION

[0026] One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are 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.

[0027] 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.

[0028] An embodiment of the present disclosure relates to a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system configured to cool a conditioning fluid. In certain embodiments, the HVAC&R system may include a refrigeration circuit having an evaporator, a compressor, and a condenser, which may be used to cool or heat a conditioning fluid (e.g., air). For example, the HVAC&R system may receive the conditioning fluid (e.g., air) from an environment and may cool the conditioning fluid via heat exchange with refrigerant within the refrigeration circuit. Further, the HVAC&R system may then return or supply the cooled conditioning fluid to a structure (e.g., a building) for cooling. Specifically, for example, a pressure drop in the refrigerant may be created via the compressor and an expansion valve to lower a temperature of the refrigerant. The evaporator may be configured to place the low temperature refrigerant in a heat exchange relationship with the conditioning fluid to absorb heat or thermal energy from the conditioning fluid, thereby cooling the conditioning fluid. Subsequent to this, the refrigerant may be pressurized by the compressor, which increases the temperature of the refrigerant. The condenser may then be used to exchange heat between the higher temperature refrigerant and ambient.

[0029] In certain scenarios, ambient temperature may be very low. As a result, a temperature of a cooling fluid (e.g., outdoor air) exchanging heat with refrigerant in the condenser may be lower than or equal to a preset threshold temperature. In such scenarios, an embodiment of the HVAC&R system of the present disclosure may operate in a free cooling mode. In the free cooling mode, the compressor is stopped (e.g., a motor of the compressor is stopped) to halt a compression operation of the compressor and the refrigerant continues to circulate through the refrigeration circuit. Continued circulation of the refrigerant may be achieved with a pump (e.g., an additional liquid pump) or without such a pump (e.g., via a thermosiphon operation). While the HVAC&R system is operated in the free cooling mode, a cooling capacity of the HVAC&R system may be controlled (e.g., reduced or increased) in accordance with a cooling demand. In order to control the cooling capacity, a pre-rotation vane (PRV) and / or a variable geometry diffuser (VGD) may be adjusted between a fully opened position and a fully closed position. For example, the cooling capacity may be progressively reduced by progressively driving one or both of the PRV and the VGD from respective fully or partially opened positions toward or to respective fully closed positions. Similarly, the cooling capacity may be progressively increased by progressively driving one or both of the PRV and the VGD from respective fully or partially closed positions toward or to respective fully opened positions. The adjustment of one or both of the PRV and the VGD may be stopped in accordance with present embodiments when a desired cooling capacity is achieved, and the PRV and / or the VGD may then be maintained at that position until it is desirable for the cooling capacity to be changed again.

[0030] In an embodiment of the present disclosure an HVAC&R system is configured to heat a conditioning fluid for warming an environment. For example, the HVAC&R system may operate as a heat pump such that it receives the conditioning fluid, heats the conditioning fluid, and then returns or provides the heated conditioning fluid to a structure (e.g., a building). In certain embodiments, the HVAC&R system may include a refrigeration circuit having an evaporator, a compressor, and a condenser. The compressor may include a pre-rotation vane (PRV) at its inlet and / or a variable geometry diffuser (VGD) at its outlet. In such a heating configuration, the condenser may be arranged to place a refrigerant in a heat exchange relationship with the conditioning fluid to release heat or thermal energy to the conditioning fluid, thereby heating the conditioning fluid. In certain scenarios, ambient temperature may be high. As a result, a temperature of a heating fluid in a heat exchange relationship with refrigerant in the evaporator may be higher than or equal to a preset threshold temperature. In such scenarios, the HVAC&R system may be operated in a free heating mode in accordance with present embodiments. In the free heating mode, the compressor is stopped (e.g., a motor of the compressor is stopped) to halt a compression operation of the compressor and the refrigerant continues to circulate through the refrigeration circuit. This continued circulation of the refrigerant may be achieved with a pump (e.g., an additional liquid pump) or without such a pump (e.g., via a thermosiphon operation). While the HVAC&R system is operated in the free heating mode, a heating capacity of the HVAC&R system may be controlled (e.g., reduced or increased) in accordance with a heating demand. In order to control the heating capacity, one or both of the PRV and the VGD may be adjusted between respective fully or partially opened positions and a respective fully closed positions. For example, the heating capacity may be progressively reduced by progressively driving one or both of the PRV and the VGD from respective fully opened positions to respective fully closed positions. Similarly, the heating capacity may be progressively increased by progressively driving one or both of the PRV and the VGD from respective fully or partially closed positions toward or to respective fully opened positions. In accordance with present embodiments, the adjustment of one or both of the PRV and the VGD may be stopped when the heating demand of the HVAC&R system is met, and the PRV and / or the VGD may be maintained at that position until it is desirable for the heating capacity to be changed again.

[0031] Before turning to the figures, it should be understood that the disclosure is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that terminology provided in the specification and figures is for the purpose of description only and should not be regarded as limiting. In general, the figures depict methods and systems to control capacity of an HVAC&R system operating in free cooling / heating mode.

[0032] Turning now to the drawings, FIG. 1 is a perspective view of an environment for a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system 10 in a building 12 for a typical commercial setting, according to some embodiments of the present disclosure. The HVAC&R system 10 may employ one or more HVAC&R units for building environmental management. As used herein, an HVAC&R 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&R system" as used herein is defined as conventionally understood and as further described herein. Components or parts of an "HVAC&R 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&R system component, a component configured to enable regulation of climate characteristics, or a combination thereof. An "HVAC&R 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.

[0033] The HVAC&R system 10 may include one or more HVAC&R units 14 and 16 which may operate to produce temperature-controlled air to be supplied to internal spaces within the building 12. In some embodiments, the HVAC&R unit 14 may be a vapor compression system 14 (e.g., a chiller, chiller system) that supplies a chilled liquid, which may be used to cool the building 12. In some embodiments, the HVAC&R unit 16 may be a boiler 16 to supply warm liquid to heat the building 12 and an air distribution system which circulates air through the building 12. The air distribution system can also include an air return duct 18, an air supply duct 20, and / or an air handler 22. In some embodiments, the air handler 22 may include a heat exchanger that is connected to the HVAC&R units 14 and 16 by conduits 24. In certain other embodiments, an HVAC&R unit in the HVAC&R system 10 may be a heat pump that provides both heating and cooling to the building 12 with one refrigeration circuit configured to operate in different modes.

[0034] The heat exchanger in the air handler 22 may receive either heated liquid from the boiler 16 or chilled liquid from the vapor compression system 14, depending on the mode of operation of the HVAC&R system 10. The HVAC&R system 10 is shown with a separate air handler on each floor of building 12, but in other embodiments, the HVAC&R system 10 may include air handlers 22 and / or other components that may be shared between or among floors.

[0035] FIG. 2 is a block diagram of the vapor compression system 14 (e.g., vapor compression circuit) that can be used in the HVAC&R system 10, according to some embodiments of the present disclosure. The vapor compression system 14 may circulate a refrigerant through a refrigeration circuit 30 starting with a compressor 32. The refrigeration circuit 30 may also include a condenser 34, an expansion valve(s) or device(s) 36, and a liquid chiller or an evaporator 38. The vapor compression system 14 may further include a control panel 40 that has an analog to digital (AD) converter 42, a microprocessor 44, a non-volatile memory 46, and / or an interface board 48.

[0036] Some examples of fluids that may be used as refrigerants (e.g., working fluids) in the vapor compression system 14 may include, but are not limited to, hydrofluorocarbon (HFC) based refrigerants, for example, R-410A, R-407, R-134a, R-1234ze, RI233zd, 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 refrigerant. In some embodiments, the vapor compression system 14 may be configured to efficiently utilize refrigerants having a normal boiling point of about 19 degrees Celsius (66 degrees Fahrenheit) at one atmosphere of pressure, also referred to as low pressure refrigerants, versus a medium pressure refrigerant, such as R-134a. As used herein, "normal boiling point" may refer to a boiling point temperature measured at one atmosphere of pressure.

[0037] In some embodiments, the vapor compression system 14 may use one or more of a motor 50, a variable speed drive (VSD) 52, the compressor 32, the condenser 34, the expansion valve or device 36, and / or the evaporator 38. The motor 50 may drive the compressor 32 and may be powered by the VSD 52. The VSD 52 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 50. In other embodiments, the motor 50 may be powered directly from an AC or direct current (DC) power source. The motor 50 may include any type of 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. Though the motor 50 is shown to be driven by a VSD, the scope of the disclosure is not limited to it. In some other embodiments, the motor 50 may be driven using a fixed speed motor drive without deviating from the scope of the disclosure.

[0038] The compressor 32 compresses a working fluid vapor and delivers the vapor to the condenser 34 through a discharge passage. In some embodiments, the compressor 32 may be a centrifugal compressor. The working fluid vapor delivered by the compressor 32 to the condenser 34 may transfer heat to a cooling fluid (e.g., water or air) in the condenser 34. The working fluid vapor may condense to a working fluid liquid in the condenser 34 as a result of thermal heat transfer with the cooling fluid. The liquid working fluid from the condenser 34 may flow through the expansion device 36 to the evaporator 38. In the illustrated embodiment of FIG. 2, the condenser 34 is water cooled and includes a tube bundle 54 connected to a cooling tower 56, which supplies the cooling fluid to the condenser 34.

[0039] The liquid working fluid delivered to the evaporator 38 may absorb heat from another cooling fluid, which may or may not be the same cooling fluid used in the condenser 34. The liquid working fluid in the evaporator 38 may undergo a phase change from the liquid working fluid to a working fluid vapor. As shown in the illustrated embodiment of FIG. 2, the evaporator 38 may include a tube bundle 58 having a supply line 60S and a return line 60R connected to a cooling load 62. The cooling fluid of the evaporator 38 (e.g., water, ethylene glycol, calcium chloride brine, sodium chloride brine, or any other suitable fluid) enters the evaporator 38 via return line 60R and exits the evaporator 38 via supply line 60S. The evaporator 38 may reduce the temperature of the cooling fluid in the tube bundle 58 via thermal heat transfer with the working fluid. The tube bundle 58 in the evaporator 38 can include a plurality of tubes and / or a plurality of tube bundles. In any case, the vapor working fluid exits the evaporator 38 and returns to the compressor 32 by a suction line to complete the cycle.

[0040] FIG. 3 is a block diagram that illustrates a schematic of the vapor compression system 14 with an intermediate circuit 64 incorporated between the condenser 34 and the expansion device 36, according to some other embodiments of the present disclosure. The intermediate circuit 64 may have an inlet line 68 (e.g., conduit) that is directly fluidly connected to the condenser 34. In other embodiments, the inlet line 68 may be indirectly fluidly coupled to the condenser 34. As shown in the illustrated embodiment of FIG. 3, the inlet line 68 includes a first expansion device 66 positioned upstream of an intermediate vessel 70. In some embodiments, the intermediate vessel 70 may be a flash tank (e.g., a flash intercooler, an economizer). In other embodiments, the intermediate vessel 70 may be configured as a heat exchanger or a "surface economizer." In the illustrated embodiment of FIG. 3, the intermediate vessel 70 is used as a flash tank, and the first expansion device 66 is configured to lower the pressure of (e.g., expand) the liquid working fluid received from the condenser 34. During the expansion process, a portion of the liquid may vaporize, and thus, the intermediate vessel 70 may be used to separate the vapor from the liquid received from the first expansion device 66.

[0041] Additionally, the intermediate vessel 70 may provide for further expansion of the liquid working fluid due to a pressure drop experienced by the liquid working fluid when entering the intermediate vessel 70 (e.g., due to a rapid increase in volume experienced when entering the intermediate vessel 70). The vapor in the intermediate vessel 70 may be drawn by the compressor 32 through a suction line 74 (e.g., conduit) of the compressor 32. In other embodiments, the vapor in the intermediate vessel may be drawn to an intermediate stage of the compressor 32 (e.g., not the suction stage). The liquid that collects in the intermediate vessel 70 may be at a lower enthalpy than the liquid refrigerant exiting the condenser 34 due to the expansion in the expansion device 66 and / or the intermediate vessel 70. The liquid from intermediate vessel 70 may then flow through a line 72 (e.g., conduit) and through a second expansion device 36 to the evaporator 38.

[0042] It should be appreciated that any of the features described herein may be incorporated with the vapor compression system 14 or any other suitable HVAC&R systems. For example, the present techniques may be incorporated with any HVAC&R system having an economizer, such as the intermediate vessel 70, and a compressor, such as the compressor 32. HVAC&R systems incorporating the present techniques may include water-cooled chillers, air-cooled chillers, heat pumps, and / or any other suitable HVAC&R system. The HVAC&R systems may utilize any suitable working fluid, such as one or more of the refrigerants discussed above or another working fluid.

[0043] FIG. 4 is a block diagram of an exemplary embodiment of a vapor compression system 400 that can be used in the HVAC&R system 10, in accordance with an embodiment of the present disclosure. The vapor compression system 14 of FIG. 1 may be implemented using the vapor compression system 400 shown in FIG. 4. The vapor compression system 400 may be operable in a normal cooling mode or a free cooling mode based on ambient temperature conditions. Specifically, the vapor compression system 400 may include control circuitry that is configured to selectively operate the vapor compression system 400 in the normal cooling mode or the free cooling mode.

[0044] In contrast to conventional vapor compression systems which have no control over cooling capacity while operating in the free cooling mode, the control circuitry of the vapor compression system 400 is configured to adjust a cooling capacity of the vapor compression system 400 (e.g., the HVAC&R system) based on ambient temperature conditions while the vapor compression system 400 operates in the free cooling mode.

[0045] The vapor compression system 400 circulates a refrigerant through a refrigeration circuit 402 starting with a compressor 404 and followed by a condenser 406, a bypass 409 and / or expansion valve(s) or device(s) 408, and an evaporator 410. Access to the bypass 409 may be controlled by a bypass valve 409, which may be controlled to open to facilitate complete bypass or parallel flow with the expansion valve(s) or device(s) 408 to limit pressure drop and any corresponding temperature drop. Some examples of fluids that may be used as refrigerants in the vapor compression system 400 are hydrofluorocarbon (HFC) based refrigerants, for example, R-410A, R-407, R-134a, 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 type of refrigerant. Though the refrigeration circuit 402 is shown to include the compressor 404 (e.g., a single stage or multistage compressor), the condenser 406, the expansion valve(s) or device(s) 408, and the evaporator 410, the scope of the disclosure is not limited by the illustrated embodiment. In some embodiments, in addition to the compressor 404 and the evaporator 410 forming a part of the refrigeration circuit 402, the refrigeration circuit 402 may include additional or alternate components, refrigerant flow paths, or the like without deviating from the scope of the disclosure.

[0046] The vapor compression system 400 may also include a motor 412, a control panel 414, a pump 416 (also a pressure difference generator 416), and a three-way valve 418. Though the pump 416 and the three-way valve 418 are shown to be disposed between the condenser 406 and the expansion device 408, the scope of the disclosure is not limited to the illustrated embodiment. In some embodiments, for example, the pump 416 may be disposed between the condenser 406 and the evaporator 410 in parallel with the expansion device 408. In some embodiments, the pump 416 may be disposed between the expansion device 408 and the evaporator 410. In some embodiments, the pump 416 and the three-way valve 418 may be disposed at other suitable positions in the refrigeration circuit 402 to maintain a refrigeration flow between the condenser 406 and the evaporator 410 when the compressor 404 is not operating (e.g., turned off).

[0047] The control panel 414 may include an analog to digital converter (ADC) 420, a controller 422 (e.g., an application specific integrated circuit (ASIC) processor, a reduced instruction set computer (RISC) processor, a complex instruction set computer (CISC) processor, a field programmable gate array (FPGA), an integrated circuit, a microcontroller, a microprocessor, a digital signal processor), a memory 424, and an interface board 426. For the sake of illustration, electrical connections in FIG. 4 are shown as dotted lines and fluid flow is shown using solid line arrows.

[0048] In some embodiments, the motor 412, driving the compressor 404, may be powered by a fixed speed drive or a variable speed drive (VSD) (e.g., VSD 52 in FIG. 2 and FIG. 3). The VSD may receive alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source, and provide power having a variable voltage and frequency to the motor 412. In one embodiment, the motor 412 may be powered directly from an AC or direct current (DC) power source. The motor 412 may include any type of motor that can be powered by a VSD, a fixed speed drive, 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.

[0049] The compressor 404 may include an inlet 428, an outlet 430, a pre-rotation vane (PRV) 432 disposed at the inlet 428, and a variable geometry diffuser (VGD) 434 disposed at the outlet 430. The PRV 432 and the VGD 434 are flow control devices disposed at the inlet 428 and the outlet 430, respectively, of the compressor 404 to enable capacity control. For example, an aperture of the PRV 432 is adjustable in the range of 0% (fully closed position) and 100% (fully open position). Similarly, aperture of the VGD 434 is adjustable in the range of 0% (fully closed position) and 100% (fully open position).

[0050] When the motor 412 is turned on, the compressor 404 is configured to execute a compression operation. During the compression operation, the compressor 404 may receive refrigerant vapor at the inlet 428 from a suction line 436 and deliver compressed refrigerant vapor via a discharge passage and the outlet 430 to the inlet of condenser 406. However, when the motor 412 is turned off, the compression operation of the compressor 404 is halted, and the refrigerant vapor received at the inlet 428 may pass through the compressor 404 without any compression. Operational aspects of the compressor 404 are further described in conjunction with FIG. 5.

[0051] Referring now to FIG. 5, a diagram that illustrates the compressor 404 driven by the motor 412 is shown in accordance with an embodiment of the present disclosure. The compressor 404 may be a centrifugal compressor, for example. As shown in FIG. 5, the compressor 404 may include a housing 502, a rotating shaft 504, and an impeller 506. The housing 502 may house the rotating shaft 504, and the impeller 506, along with various other components of the compressor 404. As illustrated, the housing 502 may further house the motor 412. However, in some embodiments, the motor 412 may be external to the housing 502. The motor 412 is coupled to the rotating shaft 504 to drive the rotating shaft 504. The motor 412 may include a stator and a rotor. The stator is a stationary part of motor's electromagnetic circuit that imparts radial and axial magnetic forces on the rotor. The rotor is the rotating part of the motor's electromagnetic circuit that rotates under the influence of the radial and axial magnetic forces imparted by the stator. The rotor is coupled to the rotating shaft 504 such that the rotating shaft 504 rotates based on the rotation of the rotor.

[0052] The rotating shaft 504 and the rotor collectively rotate about a rotation axis in order to transmit torque and rotation to other components and / or assemblies coupled to the motor 412. The rotating shaft 504 is coupled to the impeller 506 at one end thereof. In some embodiments, the rotating shaft 504 may be coupled to the impeller 506 using a direct drive connection. The direct drive connection may include a mechanical fastener (e.g., a bolt, a pin) used to couple the rotating shaft 504 to the impeller 506. The motor 412 rotates the rotating shaft 504, which in turn rotates the impeller 506. The rotation of the impeller 506 performs the compression operation on the refrigerant vapor received at the inlet 428 of the compressor 404.

[0053] In a scenario where the motor 412 is stopped, the rotating shaft 504 stops rotating. As a result, the impeller 506 coupled to the rotating shaft 504 also stops rotating. In such a scenario, the refrigerant vapor that enters the inlet 428 of the compressor 404 flows freely through the impeller 506, without being compressed.

[0054] Referring back to FIG. 4, in some embodiments, the compressor 404 may be further integrated with one or more pressure sensors to measure suction and discharge pressures of the compressor 404, one or more temperature sensors to measure suction and discharge temperatures of the compressor 404, and / or one or more position sensors to measure positions / status of the PRV 432 and the VGD 434. The sensed data from the pressure sensors, the temperature sensors, and / or the position sensors is communicated to the control panel 414 for further processing to maintain the operations of the vapor compression system 400 in accordance with present embodiments.

[0055] The refrigerant vapor delivered by the compressor 404 to the condenser 406 transfers heat to a cooling fluid, for example, water or air. The refrigerant vapor condenses to a refrigerant liquid in the condenser 406 as a result of the heat transfer with the cooling fluid. The liquid refrigerant from the condenser 406 flows through the expansion device 408 (e.g., an expansion valve) to the evaporator 410. In some embodiments, the condenser 406 may include a temperature sensor SI disposed at an inlet of the condenser 406 from where the cooling fluid enters the condenser 406. The temperature sensor SI may be configured to measure (or sense, detect) a temperature of the cooling fluid entering the condenser 406 and generate sensed data. The temperature sensor SI may then communicate the sensed data to the control panel 414 for further processing.

[0056] The liquid refrigerant delivered to the evaporator 410 absorbs heat from another fluid, which may or may not be the same type of fluid used for the condenser 406, and undergoes a phase change to a refrigerant vapor. In the exemplary embodiment shown in FIG. 4, the evaporator 410 includes an exchanger coil 438 having a supply line 440S and a return line 440R connected to a load 442 to be cooled. A conditioning fluid, for example, ethylene glycol, calcium chloride brine, sodium chloride brine, or any other suitable liquid, enters the evaporator 410 via the return line 440R and exits the evaporator 410 via the supply line 442S. The evaporator 410 cools the conditioning fluid in the exchanger coil 438. The vapor refrigerant exits the evaporator 410 and returns to the compressor 404 by the suction line 436 to complete the cycle.

[0057] In some embodiments, the evaporator 410 may include a temperature sensor S2 disposed at an inlet of the evaporator 410 at which the conditioning fluid enters the evaporator 410. The temperature sensor S2 may be configured to measure (or sense, detect) a temperature of the conditioning fluid entering the evaporator 410 and generate sensed data. The temperature sensor S2 may then communicate the sensed data to the control panel 414 for further processing.

[0058] The liquid refrigerant exiting the condenser 406 may be delivered to the evaporator 410 via a first path 444 or a second path 446. The three-way valve 418 controlled by the controller 422 may selectively circulate the liquid refrigerant exiting the condenser 406 via the first path 444 or the second path 446. When the motor 412 is turned on and the compressor 404 is executing the compression operation, the three-way valve 418 may be configured to close the second path 446 and open the first path 444 such that the liquid refrigerant exiting the condenser 406 is circulated via the first path 444. In the first path 444, the liquid refrigerant exiting the condenser 406 is transferred to the evaporator 410 by bypassing the pump 416. However, when the motor 412 is turned off (or stopped) and the compression operation of the compressor 404 is halted, the three-way valve 418 may be configured to close the first path 444 and open the second path 446. The liquid refrigerant exiting the condenser 406 is then circulated via the second path 446. In the second path 446, the liquid refrigerant exiting the condenser 406 is transferred to the evaporator 410 via the pump 416. The pump 416, when activated by the controller 422, is configured to pressurize the refrigerant to maintain a flow of the refrigerant and cause the refrigerant to circulate through the refrigeration circuit 402 even when the compressor 404 is turned off. In other words, the liquid refrigerant exiting the condenser 406 may bypass the pump 416 when the compressor 404 is in an ON state ("on") / and may flow through the pump 416 when the compressor 404 is in an OFF state ("off" or "stopped"). It should be noted that, in some embodiments, the pump 416 may be replaced with a pressure difference generator, which includes any suitable device or configuration that operates to pressurize the refrigerant to maintain refrigerant circulation when the compressor 404 is stopped, without deviating from the scope of the disclosure.

[0059] The control panel 414 may include the ADC 420 to receive analog input signals, from various components of the vapor compression system 400. Such analog input signals may indicate the performance of the vapor compression system 400. For example, the input signals received by the control panel 414 may include the temperatures of the fluids entering the condenser 406 and the evaporator 410, refrigerant pressures in the evaporator 410 and the condenser 406, or the like. The ADC 420 may be configured to convert the received analog signals to digital input signals and provide the converted input signals to the controller 422 for further processing.

[0060] The control panel 414 may include the memory 424 to store various control algorithm(s) executable by the controller 422. The control algorithm(s) can be computer programs stored in the memory 424 and have a series of instructions executable by the controller 422. The one or more control algorithm(s) may be executable to control the operation of the vapor compression system 400. For example, the control panel 414 may use the control algorithm(s) to selectively operate the vapor compression system 400 in the normal cooling mode or the free cooling mode based on a temperature of the cooling fluid entering the condenser 406. In the free cooling mode, the control panel 414 may further use the control algorithm(s) to adjust positions of at least one of the PRV 432 and the VGD 434 to control a cooling capacity of the vapor compression system 400. While the control algorithm(s) may be embodied in a computer program(s) and executed by the controller 422 (for example, control circuitry), it will be understood by those skilled in the art that the control algorithm(s) may be implemented and executed using digital and / or analog hardware. If hardware is used to execute the control algorithm(s), the corresponding configuration of the control panel 414 can be changed to incorporate the necessary components and to remove any components that may no longer be required.

[0061] The control panel 414 may include the controller 422 to execute or use a single or central control algorithm or control system to control the vapor compression system 400 and components of the vapor compression system 400. In one embodiment, the control system can be a computer program or software having a series of instructions executable by the controller 422. In another embodiment, the control system may be implemented and executed using digital and / or analog hardware by those skilled in the art. In still another embodiment, the control panel 414 may incorporate multiple controllers, each performing a discrete function, with a central controller that determines the outputs of the control panel 414. If hardware is used to execute the control algorithm, the corresponding configuration of the control panel 414 can be changed to incorporate the necessary components and to remove any components that may no longer be required.

[0062] The central control algorithm executed by the controller 422 may include a mode control program or algorithm to selectively operate the vapor compression system 400 (HVAC&R system) in the normal cooling mode or the free cooling mode. The mode control program when executed may cause the controller 422 to automatically select one of the normal cooling mode and the free cooling mode for operating the vapor compression system 400. The controller 422 may provide suitable control signals to control the motor 412, the pump 416, and the three- way valve 418, and based on the selection of one of the normal cooling mode and the free cooling mode.

[0063] The central control algorithm executed by the controller 422 may further include a capacity control program or algorithm to control a cooling capacity of the vapor compression system 400 in the free cooling mode. The capacity control program when executed may cause the controller 422 to provide control signals to actuators of the PRV 432 and / or the VGD 434 via the interface board 426 to adjust the position of the PRV 432 and / or the VGD 434. The controller 422 may further be configured to employ feedback (e.g., continuous feedback) from the temperature sensor SI to monitor temperature changes in the cooling fluid.

[0064] The control panel 414 may further include the interface board 426 to transmit actuation and control signals generated by the controller 422 to various components of the vapor compression system 400 for controlling the operation of the vapor compression system 400. For example, the control panel 414 may be configured to transmit actuation signals to stop the motor 412 and activate the pump 416 when the free cooling mode is selected. The control panel 414 may also be configured to transmit actuation and control signals to control the positions of the PRV 432 and / or the VGD 434 for capacity control during the free cooling mode.

[0065] In one embodiment, the control panel 414 may be connected to or configured to incorporate a user interface 448 that permits an operator to interact with the control panel 414. The operator can select and enter commands for the control panel 414 through the user interface 448. In addition, the user interface 448 can display messages and information from the control panel 414 regarding the operational status of the vapor compression system 400 for the operator. The user interface 448 can be located locally to the control panel 414, such as being mounted on the vapor compression system 400 or the control panel 414, or alternatively, the user interface 448 can be located remotely from the control panel 414, such as being located in a separate control room apart from the vapor compression system 400. Operations of the vapor compression system 400 in the normal cooling mode and the free cooling mode are described later in conjunction with FIGS. 6A and 6B.

[0066] Though the vapor compression system 400 is shown as including the pump 416 and the three-way valve 418, the scope of the disclosure is not limited to this illustrated embodiment. In some embodiments, the vapor compression system 400 may not include the pump 416 and the three-way valve 418. In such a vapor compression system, the flow of the liquid refrigerant between the condenser 406 and the evaporator 410 may be maintained even when the compressor 404 is turned off (e.g., in an OFF state) due to a pressure difference between the condenser 406 and the evaporator 410. The pressure difference between the condenser 406 and the evaporator 410 may be caused due to a height difference between the condenser 406 and the evaporator 410. Thus, the refrigerant may flow naturally from the condenser 406 to the evaporator 410 when the compressor 404 is stopped, maintaining a flow of the refrigerant in the refrigeration circuit 402. This configuration may be an example of a pressure difference generator. Similar to the vapor compression system 400, a vapor compression system including a pressure difference generator that is not a pump (e.g., the pump 416) is also operable in the normal cooling mode or the free cooling mode based on ambient temperature conditions.

[0067] FIG. 6A is a block diagram of the vapor compression system 400 (e.g., the HVAC&R system) operating in the normal cooling mode, according to some embodiments of the present disclosure. The ADC 420 may be configured to receive sensed data (e.g., analog input signals) from the temperature sensor SI. The sensed data may indicate (e.g., directly or indirectly) the temperature of the cooling fluid entering an inlet of the condenser 406 via a return line 602R. The ADC 420 may convert the received sensed data in a format compatible with the controller 422 and provide the converted sensed data to the controller 422. Though, in FIG. 6A, the controller 422 is illustrated as receiving the sensed data from the temperature sensor SI via the ADC 420, the present disclosure is not limited to this embodiment. In some embodiments, the controller 422 may receive the sensed data directly from the temperature sensor SI or a different sensor that provides relevant data.

[0068] The controller 422 may execute the mode control program or algorithm to selectively operate the vapor compression system 400 in the normal cooling mode or the free cooling mode when cooling operation is desired. The controller 422 may determine whether cooling operation is desired based on, for example, a temperature setting of a thermostat, a temperature of a return air, a temperature of a supply air, a temperature of the conditioning fluid entering or leaving the evaporator 410, or the like. In an example, when the temperature of the return air is substantially the same as or lower than the temperature of supply air, the controller 422 may determine that cooling operation is not desired. However, when the temperature of the return air is greater than the temperature of supply air, the controller 422 may determine that cooling operation is desired. In some embodiments, the controller 422 may utilize some other control logic known in the art to determine whether cooling operation is desired (e.g., required) or not, without deviating from the scope of the disclosure. Upon determining that the cooling operation is desired, the controller 422 may execute the mode control program or algorithm to selectively operate the vapor compression system 400 in the normal cooling mode or the free cooling mode. The controller 422 may compare the temperature of the cooling fluid, entering the condenser 406, with a first threshold temperature value and generate a first comparison result. When the first comparison result indicates that the temperature of the cooling fluid is greater than the first threshold temperature value, the controller 422 may select the normal cooling mode to operate the vapor compression system 400. In response to selection of the normal cooling mode, the controller 422 may be configured to generate control signals to operate the motor 412, the pump 416, and the three-way valve 418 in accordance with the normal cooling mode. The controller 422 may provide the control signals to the motor 412, the pump 416, and the three-way valve 418, for example, via the interface board 426 or direct communication.

[0069] The control signal when received by the three-way valve 418 may cause the three-way valve 418 to open the first path 444 for refrigerant flow and close the second path 446. Based on the control signal, the three-way valve 418 opens the first path 444 (indicated by solid line) and closes the second path 446 (indicated by dotted line). This configuration allows the liquid refrigerant exiting the condenser 406 to be delivered to the evaporator 410 via the first path 444 and without going through the pump 416. Further, the motor 412 is on (e.g., in an ON state) and the pump 416 remains deactivated (e.g., in an OFF state) based on the control signal provided by the controller 422 in the normal cooling mode.

[0070] The control signal when received by the motor 412 may turn on the motor 412 and may cause the motor 412 to drive the rotating shaft 504 (shown in FIG. 5). The rotating shaft 504 transmits the torque to drive the impeller 506, which results in the compression operation being performed on the refrigerant vapor received at the inlet 428 of the compressor 404 from the evaporator 410. The controller 422 may be configured to operate the vapor compression system 400 in the normal cooling mode until the temperature of the cooling fluid entering the condenser 406 becomes equal to or lower than the first threshold temperature value. The first threshold temperature value may be preset by an operator, installer, manufacturer, or the like of the vapor compression system 400 using the user interface 448 or other techniques. In some embodiments, the first threshold temperature value may be set automatically by the controller 422 or manually by the operator based on a cooling temperature requirement. The first threshold temperature value may be stored in the memory 424.

[0071] FIG. 6B is a block diagram of the vapor compression system 400 (e.g., the HVAC&R system) operating in the free cooling mode, in accordance with an embodiment of the present disclosure. In a scenario when the cooling operation is required and the first comparison result (e.g., generated by comparing the temperature of the cooling fluid entering the condenser 406 with the first threshold temperature value) indicates that the temperature of the cooling fluid is at a particular level (e.g., within a range), such as less than or equal to the first threshold temperature value, the controller 422 may initiate or maintain operation in the free cooling mode. For example, the controller 422 may utilized temperature data to determine whether the cooling capacity in the free cooling mode is sufficient to satisfy the cooling demand. If the controller 422 determines that the cooling capacity in the free cooling mode is not sufficient to satisfy the cooling demand, the controller 422 may select the normal cooling mode to operate the vapor compression system 400, as shown in FIG. 6A. However, if the controller 422 determines that the cooling capacity in the free cooling mode is sufficient to satisfy the cooling demand, the controller 422 may select the free cooling mode to operate the vapor compression system 400. The controller 422 may determine the cooling demand based on, for example, a temperature setting of the thermostat, a temperature of the return air, a temperature of a supply air, a temperature of the conditioning fluid entering or leaving the evaporator 410, or the like. In one embodiment, the controller 422 may utilize some other control logic known in the art to determine the cooling demand, in accordance with the present disclosure.

[0072] Upon selecting the free cooling mode, the controller 422 may be configured to execute the capacity control program to control a cooling capacity of the vapor compression system 400 operating in the free cooling mode. The controller 422 may be configured to control the cooling capacity of the vapor compression system 400 operating in the free cooling mode based on the cooling demand. While executing the capacity control program in the free cooling mode, the controller 422 may be configured to compare the current cooling capacity of the vapor compression system 400 with the cooling demand and generate a second comparison result. The second comparison result may indicate a difference between the current cooling capacity of the vapor compression system 400 and the cooling demand. The controller 422 may then determine a new cooling capacity required to meet the cooling demand.

[0073] The controller 422 may be configured to generate control signals to operate the motor 412, the pump 416, and the three-way valve 418 in accordance with the free cooling mode. The controller 422 may be configured to generate actuation signals to adjust the PRV 432 and / or the VGD 434 to control the cooling capacity of the vapor compression system 400 operating in the free cooling mode, for example, to satisfy the cooling demand. The controller 422 may provide the control signals to the motor 412, the pump 416, and the three-way valve 418, and the actuation signals to the PRV 432 and / or the VGD 434 for example, via the interface board 426 or direct communication.

[0074] The control signal when received by the three-way valve 418 may cause the three-way valve 418 to close the first path 444 and open the second path 446 for refrigerant flow. Based on the control signal, the three-way valve 418 opens the second path 446 (indicated by solid line) and closes the first path 444 (indicated by dotted line). Opening of the second path 446 allows the liquid refrigerant exiting the condenser 406 to be delivered to the evaporator 410 via the second path 446. While flowing through the second path 446, the liquid refrigerant flows through the pump 416.

[0075] The control signal when received by the pump 416 causes the pump 416 to activate (e.g., enter an ON state). The activated pump 416 pressurizes the liquid refrigerant to provide (cause flow of) the liquid refrigerant to the evaporator 410. The control signal when received by the motor 412 causes the motor 412 to stop (e.g., enter an OFF state). As a result, the rotating shaft 504 (shown in FIG. 5) and the impeller 506 also stop rotating, which results in the compression operation at the compressor 404 to halt. Thus, the refrigerant pressurized by the activated pump 416 circulates through the refrigeration circuit 402 and flows freely through the impeller 506. In some embodiments, the pump 416 may represent a pressure difference generator that is not a pump.

[0076] In some embodiments, the controller 422 may provide the actuation signal to one or more actuators of the PRV 432 to adjust the PRV 432 in a position that satisfies the cooling demand. In an example, the controller 422 may be configured to receive sensor readings from the position sensors monitoring a position of the PRV 432. When a current position of the PRV 432 results in a cooling capacity that is more than the desired (or determined) cooling capacity, the actuation signal provided by the controller 422 may adjust the current position of the PRV 432 to reduce the cooling capacity. The current position of the PRV 432 may be a fully opened position or a partially closed position. The actuation signal may cause the actuator to progressively drive the PRV 432 from the current position towards the fully closed position. The actuator, based on the actuation signal, may close the PRV 432 in steps or increments until the cooling demand is met or the fully closed position is reached. While the PRV 432 is being progressively closed, the controller 422 may continue to monitor the temperature of the conditioning fluid leaving the evaporator 410 to detect the changes in the cooling capacity of the vapor compression system 400. When the cooling capacity of the vapor compression system 400 matches the cooling demand, the controller 422 may stop the actuation signal and maintain the PRV 432 at that position at which the cooling demand was met. In another example, a current position of the PRV 432 may result in a cooling capacity that is less than the desired (or determined) cooling capacity. In such a scenario, the actuation signal provided by the controller 422 may adjust the current position of the PRV 432 to increase the cooling capacity. The current position of the PRV 432 may be a partially closed position. The actuation signal may cause the actuator to progressively drive the PRV 432 from the current position towards the fully opened position. The actuator, based on the actuation signal, may open the PRV 432 in steps or increments until the cooling demand is met or the fully open position is reached. While the PRV 432 is being progressively opened, the controller 422 may continue to monitor the temperature of the conditioning fluid leaving the evaporator 410 to detect the changes in the cooling capacity of the vapor compression system 400. When the cooling capacity of the vapor compression system 400 matches the cooling demand, the controller 422 may stop the actuation signal and maintain the PRV 432 at that position at which the cooling demand was met.

[0077] In some embodiments, the controller 422 may provide the actuation signal to one or more actuators of the VGD 434 to adjust the VGD 434 in a position that satisfies the cooling demand. In an example, the controller 422 may be configured to receive sensor readings from the position sensors monitoring a position of the VGD 434. When a current position of the VGD 434 results in a cooling capacity that is more than the desired (or determined) cooling capacity, the actuation signal provided by the controller 422 may adjust the current position of the VGD 434 to reduce the cooling capacity. The current position of the VGD 434 may be a fully opened position or a partially closed position. The actuation signal may cause the actuator to progressively drive the VGD 434 from the current position towards the fully closed position. The actuator, based on the actuation signal, may close the VGD 434 in steps or increments until the cooling demand is met or the fully closed position is reached. While the VGD 434 is being progressively closed, the controller 422 may continue to monitor the temperature of the conditioning fluid leaving the evaporator 410 to detect the changes in the cooling capacity of the vapor compression system 400. When the cooling capacity of the vapor compression system 400 matches the cooling demand, the controller 422 may stop the actuation signal and maintain the VGD 434 at that position at which the cooling demand was met. In another example, a current position of the VGD 434 may result in a cooling capacity that is less than the desired (or determined) cooling capacity. In such a scenario, the actuation signal provided by the controller 422 may adjust the current position of the VGD 434 to increase the cooling capacity. The current position of the VGD 434 may be a partially closed position. The actuation signal may cause the actuator to progressively drive the VGD 434 from the current position towards the fully opened position. The actuator, based on the actuation signal, may open the VGD 434 in steps or increments until the cooling demand is satisfied or the fully open position is reached. While the VGD 434 is being progressively opened, the controller 422 may continue to monitor the temperature of the conditioning fluid leaving the evaporator 410 to detect the changes in the cooling capacity of the vapor compression system 400. When the cooling capacity of the vapor compression system 400 matches the cooling demand, the controller 422 may stop the actuation signal and maintain the VGD 434 at that position at which the cooling demand was met.

[0078] In accordance with embodiments of the present disclosure, the controller 422 may provide the actuation signals to the actuators of the PRV 432 and the VGD 434 to adjust the PRV 432 and the VGD 434 in combination for satisfying the cooling demand. The controller 422 may additionally or alternatively adjust an opening of the expansion device 408, for example, from a fully opened position to a partially closed position, to control the cooling capacity of the vapor compression system 400. The bypass valve 409 may likewise or separately be controlled. In some embodiments, the expansion device 408 may be bypassed entirely or a parallel flow may be established via the bypass 409 and the bypass valve 411 to limit pressure drop and corresponding temperature drop. Further, the pump 416 may be controlled using a VSD. In such a scenario, the cooling capacity of the vapor compression system 400 may additionally or alternatively be controlled by controlling pumping power of the pump 416. For example, the pumping power may be reduced by the controller 422 to reduce the cooling capacity and the pumping power may be increased to increase the cooling capacity. Different pressure difference generators may be controlled differently.

[0079] The capacity controlled refrigerant vapor flowing from the compressor 404 to the condenser 406 transfers heat to the cooling fluid entering the condenser 406. The refrigerant vapor condenses to a refrigerant liquid in the condenser 406 as a result of the heat transfer with a cooling fluid. The liquid refrigerant from the condenser 406 flows to the evaporator 410 through the second path 446, for example, through the pump 416, and then through the fully or partially opened expansion device 408 (e.g., an expansion valve). In some embodiments, the second path 446 may bypass or extend parallel to the expansion device 408. The liquid refrigerant delivered to the evaporator 410 absorbs heat from the conditioning fluid entering the evaporator 410, and may undergo a phase change to a refrigerant vapor. As a result, the conditioning fluid in the exchanger coil 438 is cooled to satisfy the cooling demand. The vapor refrigerant exits the evaporator 410 and returns to the compressor 404 to complete the cycle.

[0080] While the vapor compression system 400 operates in the free cooling mode, the controller 422 may monitor the cooling capacity, periodically, continuously, or at somewhat random time intervals. If the current cooling capacity deviates from the cooling demand, the controller 422 may execute the capacity control program described above to adjust at least one of the PRV 432 and the VGD 434. Further, if the cooling capacity in the free cooling mode becomes insufficient to satisfy the cooling demand, the controller 422 may switch from the free cooling mode to the normal cooling mode.

[0081] While the vapor compression system 400 operates in the free cooling mode, the controller 422 may further monitor the temperature of the cooling fluid entering the condenser 406 to determine whether the free cooling mode can be continued. In an exemplary scenario, while the vapor compression system 400 is operating in the free cooling mode, the temperature of the cooling fluid entering the condenser 406 may exceed the first threshold temperature value. In such a scenario, the controller 422 may switch from the free cooling mode to the normal cooling mode.

[0082] The controller 422 may again switch from the normal cooling mode to the free cooling mode when the temperature of the cooling fluid entering the condenser 406 becomes less than or equal to the first threshold temperature value and when the cooling capacity in the free cooling mode becomes sufficient to satisfy the cooling demand. In other words, when cooling operation is required, the controller 422 may operate the vapor compression system 400 in the normal cooling mode or the free cooling mode in accordance with operating conditions (e.g., temperature of the cooling fluid entering the condenser 406, cooling demand) of the vapor compression system 400.

[0083] In another example scenario, while the vapor compression system 400 is operating in the free cooling mode, the controller 422 may determine that the cooling operation is no longer required. In such a scenario, the controller 422 may be configured to stop the circulation of the refrigerant in the refrigeration circuit 402. To stop the circulation of the refrigerant, the controller 422 may be configured to generate a control signal which when received by the pump 416 may cause the pump 416 to stop. As the compressor 404 was already deactivated, deactivating the pump 416 causes the refrigerant in the refrigeration circuit 402 to stop circulating.

[0084] In some embodiments, during the normal cooling mode or the free cooling mode, the controller 422 may be configured to determine a likelihood of the conditioning fluid getting frozen in one or more tubes (e.g., the exchanger coil 438, the supply line 440S, and the return line 440R) of the evaporator 410. In an example, the conditioning fluid circulation through the evaporator 410 may stop due to a fault or error and some conditioning fluid may remain in the tubes of the evaporator 410. In such a scenario, the controller 422 may determine that there is a high likelihood that the refrigerant flow through the evaporator 410 can cause the conditioning fluid to freeze due to heat exchange between the refrigerant and the conditioning fluid. In response to determining the likelihood of the conditioning fluid getting frozen in the evaporator 410, the controller 422 may be configured to adjust at least one of the PRV 432 and the VGD 434 to the fully closed position. Additionally, or alternatively, the controller 422 may be configured to adjust the opening of the expansion device 408 (and / or the bypass valve 411) to a fully closed position to prevent the refrigerant from flowing into the evaporator 410. The controller 422 may further activate the pump 416 temporarily so as to draw the refrigerant out of the evaporator 410. With at least one of the PRV 432 and the VGD 434 (and / or the expansion device 408 and bypass valve 409) fully closed, refrigerant may not flow into the evaporator 410. With no refrigerant available in the evaporator 410, the controller 422 prevents freezing of the conditioning fluid in the evaporator 410. The controller 422 may open the closed PRV 432, the VGD 434, the expansion device 408, and / or the bypass valve 411 when there is no or substantially low likelihood that the refrigerant flow through the evaporator 410 can cause the conditioning fluid to freeze. In some embodiments, the expansion device 408 may be closed an the bypass valve 411 may be fully opened to facilitate desired flow.

[0085] Though FIGS. 4, 6A, and 6B describe the use of HVAC&R system (e.g., the vapor compression system 400) to cool a space, the scope of the present disclosure is not limited these embodiments. Indeed, the HVAC&R system (e.g., the vapor compression system 400) can also be used to heat an environment. Working of a vapor compression system as a boiler to heat a space is described in conjunction with FIGS. 7A and 7B.

[0086] FIGS. 7A and 7B are block diagrams of a vapor compression system 700 that can be used in the HVAC&R system 10 for heating, in accordance with an embodiment of the present disclosure. The boiler 16 of FIG. 1 may be implemented using the vapor compression system 700 shown in FIGS. 7A and 7B. The vapor compression system 700 is similar to the vapor compression system 400 except that the vapor compression system 700 is used to heat a space. In an embodiment, the vapor compression system 700 represents reconfigured operation of the vapor compression system 400, as with a heat pump, wherein the heat exchangers that operate as the condenser 406 and evaporator 410 switch functions. This switch is depicted by illustrating the load 442 exchanging heat with the evaporator 410 in FIGS. 6A and 6B and the load 706 exchanging head with the condenser 406 in FIGS. 7A and 7B.

[0087] The refrigerant vapor delivered by the compressor 404 to the condenser 406 transfers heat to a conditioning fluid (e.g., ethylene glycol, calcium chloride brine, sodium chloride brine) and condenses to a refrigerant liquid in the condenser 406 as a result of the heat transfer with the conditioning fluid. In the exemplary embodiment shown in FIGS. 7A and 7B, the condenser 406 includes an exchanger coil 702 having a supply line 704S and a return line 704R connected to a load 706 to be heated. The conditioning fluid enters the condenser 406 via the return line 704R and exits the condenser 406 via the supply line 704S. The condenser 406 heats the conditioning fluid in the exchanger coil 702. The refrigerant liquid then exits the condenser 406 and is transferred to the expansion device 408.

[0088] The working of the other components of the vapor compression system 700 of FIGS. 7A and 7B is like the working of corresponding components of the vapor compression system 400 described in the foregoing description of FIGS. 4 and 5. However, the vapor compression system 700 is operable to switch between a normal heating mode and a free heating mode based on ambient temperature conditions. The vapor compression system 700 may include control circuitry that is configured to selectively operate the vapor compression system 700 in the normal heating mode or the free heating mode, including switching there between. Further, the control circuitry of the vapor compression system 700 is configured to adjust a heating capacity of the vapor compression system 700 in accordance with ambient temperature conditions while the vapor compression system 700 operates in the free heating mode. Operation of the vapor compression system 700 in the normal heating mode is described in conjunction with FIG. 7A and operation of the vapor compression system 700 in the free heating mode is described in conjunction with FIG. 7B.

[0089] Though the refrigeration circuit 402 is shown to include the compressor 404, the condenser 406, the expansion valve(s) or device(s) 408, and the evaporator 410, the scope of the disclosure is not limited to the illustrated embodiment. In some embodiments, in addition to the compressor 404 and the condenser 406, the refrigeration circuit 402 may include additional or alternate components, refrigerant flow paths, or the like without deviating from the scope of the present disclosure. For example, in the illustrated embodiment, the bypass 409 is included to facilitate refrigerant flow in certain scenarios.

[0090] With reference to FIG. 7A, the ADC 420 may be configured to receive sensed data from the temperature sensor S2. The sensed data may indicate (e.g., directly or indirectly) the temperature of a heating fluid entering an inlet of the evaporator 410 via the return line 440R. The ADC 420 may convert the received sensed data in a format compatible with the controller 422 and provide the converted sensed data to the controller 422. FIG. 7A illustrates the controller 422 receiving the sensed data from the temperature sensor S2 via the ADC 420. However, in other embodiments, the controller 422 may receive the sensed data directly from the temperature sensor S2, from other sensors, or the like.

[0091] The controller 422 may execute the mode control program or algorithm to selectively operate the vapor compression system 700 in the normal heating mode or the free heating mode when heating operation is desired (e.g., required). The controller 422 may determine whether heating operation is desired based on, for example, a temperature setting of a thermostat, a temperature of a return air, a temperature of a supply air, a temperature of the conditioning fluid entering or leaving the condenser 406, or the like. For example, when the temperature of the return air is substantially the same as or higher than the temperature of supply air, the controller 422 may determine that heating operation is not desired. However, when the temperature of the return air is lower than the temperature of supply air, the controller 422 may determine that heating operation is desired. In some embodiments, the controller 422 may utilize some other control logic known in the art to determine whether heating operation is desired (e.g., required) or not, without deviating from the scope of the disclosure.

[0092] Upon determining that the heating operation is desired, the controller 422 may execute the mode control program or algorithm to selectively operate the vapor compression system 700 in the normal heating mode or the free heating mode. The controller 422 may compare the temperature of the heating fluid entering the evaporator 410 with a second threshold temperature value and generate a third comparison result. When the third comparison result indicates that the temperature of the heating fluid is lower than the second threshold temperature value, the controller 422 may select the normal heating mode to operate the vapor compression system 700. In response to selection of the normal heating mode, the controller 422 may be configured to generate control signals to operate the motor 412, the pump 416, and the three-way valve 418 in accordance with the normal heating mode. The controller 422 may provide the control signals to the motor 412, the pump 416, and the three-way valve 418, for example, via the interface board 426 or direct communication. The control signal when received by the three-way valve 418 may cause the three-way valve 418 to open the first path 444 for refrigerant flow and close the second path 446. Based on the control signal, the three-way valve 418 opens the first path 444 (indicated by solid line) and closes the second path 446 (indicated by dotted line). This configuration allows the liquid refrigerant exiting the condenser 406 to be delivered to the evaporator 410 via the first path 444, bypassing the pump 416. Further, the motor 412 is on (e.g., in an ON state) and the pump 416 remains deactivated (e.g., in an OFF state) based on the control signal provided by the controller 422 in the normal heating mode.

[0093] The control signal when received by the motor 412 may turn on the motor 412 and may cause the motor 412 to drive the rotating shaft 504 (shown in FIG. 5). The rotating shaft 504 transmits the torque to drive the impeller 506, which results in the compression operation being performed on the refrigerant vapor received at the inlet 428 of the compressor 404 from the evaporator 410. The controller 422 may be configured to operate the vapor compression system 700 in the normal heating mode until the temperature of the heating fluid entering the evaporator 410 becomes equal to or greater than the second threshold temperature value. The second threshold temperature value may be preset using the user interface 448 or another technique. In some embodiments, the second threshold temperature value may be set automatically by the controller 422 or manually by the operator based on a heating temperature requirement. The second threshold temperature value may be stored in the memory 424.

[0094] With reference to FIG. 7B, when the heating operation is desired and the third comparison result (e.g., generated by comparing the temperature of the heating fluid entering the evaporator 410 with the second threshold temperature value) indicates that the temperature of the heating fluid is at a particular level (e.g., within a range), such as greater than or equal to the second threshold temperature value, the controller 422 may initiate or maintain operation in the free cooling mode. For example, the controller 422 may utilize temperature data to determine whether the heating capacity in the free heating mode is sufficient to satisfy a heating demand. The controller 422 may determine the heating demand based on, for example, a temperature setting of the thermostat, a temperature of the return air, a temperature of the supply air, a temperature of the conditioning fluid entering the condenser 406 after conditioning the space, or the like. In some other embodiments, the controller 422 may utilize some other control logic known in the art to determine the heating demand, without deviating from the scope of the disclosure. If the controller 422 determines that the heating capacity in the free heating mode is not sufficient to satisfy the heating demand, the controller 422 may select the normal heating mode to operate the vapor compression system 700, as shown in FIG. 7A. However, if the controller 422 determines that the heating capacity in the free heating mode is sufficient to satisfy the heating demand, the controller 422 may select the free heating mode to operate the vapor compression system 700.

[0095] Upon selecting the free heating mode, the controller 422 may be configured to execute the capacity control program to control a heating capacity of the vapor compression system 700 operating in the free heating mode. The controller 422 may be configured to control the heating capacity of the vapor compression system 700 operating in the free heating mode based on the heating demand. While executing the capacity control program in the free heating mode, the controller 422 may be configured to compare the current heating capacity of the vapor compression system 700 with the heating demand and generate a fourth comparison result. The fourth comparison result may indicate a difference between the current heating capacity of the vapor compression system 700 and the heating demand. The controller 422 may then determine new heating capacity required to meet the heating demand.

[0096] The controller 422 may be configured to generate control signals to operate the motor 412, the pump 416, and the three-way valve 418 in accordance with the free heating mode. The controller 422 may be configured to generate actuation signals to adjust the PRV 432 and / or the VGD 434 to control the heating capacity of the vapor compression system 700 operating in the free heating mode, for example, to satisfy the heating demand. The controller 422 may provide the control signals to the motor 412, the pump 416, and the three-way valve 418, and the actuation signals to the PRV 432 and / or the VGD 434 for example, via the interface board 426 or direct communication.

[0097] The control signal when received by the three-way valve 418 may cause the three-way valve 418 to close the first path 444 and open the second path 446 for refrigerant flow. Based on the control signal, the three-way valve 418 opens the second path 446 (indicated by solid line) and closes the first path 444 (indicated by dotted line). Opening of the second path 446 allows the liquid refrigerant exiting the condenser 406 to be delivered to the evaporator 410 via the second path 446. While flowing through the second path 446, the liquid refrigerant flows through the pump 416. The control signal when received by the pump 416 causes the pump 416 to activate. The activated pump 416 pressurizes the liquid refrigerant to provide the liquid refrigerant to the evaporator 410. The pump 416 may represent any type of pressure difference generator.

[0098] The control signal when received by the motor 412 causes the motor 412 to stop. As a result, the rotating shaft 504 (shown in FIG. 5) and the impeller 506 also stop rotating, which results in the compression operation at the compressor 404 to halt (e.g., enter or maintain an OFF state). Thus, the vapor refrigerant exiting the evaporator 410 flows freely through the impeller 506 and the pump 416 (or some other pressure difference generator) handles circulation.

[0099] In some embodiments, the controller 422 may provide the actuation signal to one or more actuators of the PRV 432 to adjust the PRV 432 in a position that satisfies the heating demand. In an example, the controller 422 may be configured to receive sensor readings from the position sensors monitoring a position of the PRV 432. When a current position of the PRV 432 results in a heating capacity that is more than the desired (or determined) heating capacity, the actuation signal provided by the controller 422 may adjust the current position of the PRV 432 to reduce the heating capacity. The current position of the PRV 432 may be a fully opened position or a partially closed position. The actuation signal may cause the actuator to progressively drive the PRV 432 from the current position towards the fully closed position. The actuator, based on the actuation signal, may close the PRV 432 in steps or increments until the heating demand is satisfied or the fully closed position is reached. While the PRV 432 is being progressively closed, the controller 422 may continue to monitor the temperature of the conditioning fluid leaving the condenser 406 to detect the changes in the heating capacity of the vapor compression system 700. When the heating capacity of the vapor compression system 700 matches the heating demand, the controller 422 may stop the actuation signal and maintain the PRV 432 at that position at which the heating demand was met. In another example, a current position of the PRV 432 may result in a heating capacity that is less than the desired (or determined) heating capacity. In such a scenario, the actuation signal provided by the controller 422 may adjust the current position of the PRV 432 to increase the heating capacity. The current position of the PRV 432 may be a partially closed position. The actuation signal may cause the actuator to progressively drive the PRV 432 from the current position towards the fully opened position. The actuator, based on the actuation signal, may open the PRV 432 in steps or increments until the heating demand is met or the fully open position is reached. While the PRV 432 is being progressively opened, the controller 422 may continue to monitor the temperature of the conditioning fluid leaving the condenser 406 to detect the changes in the heating capacity of the vapor compression system 700. When the heating capacity of the vapor compression system 700 matches the heating demand, the controller 422 may stop the actuation signal and maintain the PRV 432 at that position at which the heating demand was met.

[0100] In some embodiments, the controller 422 may provide the actuation signal to one or more actuators of the VGD 434 to adjust the VGD 434 in a position that satisfies the heating demand. In an example, the controller 422 may be configured to receive sensor readings from the position sensors monitoring a position of the VGD 434. When a current position of the VGD 434 results in a heating capacity that is more than the desired (or determined) heating capacity, the actuation signal provided by the controller 422 may adjust the current position of the VGD 434 to reduce the heating capacity. The current position of the VGD 434 may be a fully opened position or a partially closed position. The actuation signal may cause the actuator to progressively drive the VGD 434 from the current position towards the fully closed position. The actuator, based on the actuation signal, may close the VGD 434 in steps or increments until the heating demand is met or the fully closed position is reached. While the VGD 434 is being progressively closed, the controller 422 may continue to monitor the temperature of the conditioning fluid leaving the condenser 406 to detect the changes in the heating capacity of the vapor compression system 700. When the heating capacity of the vapor compression system 700 matches the heating demand, the controller 422 may stop the actuation signal and maintain the VGD 434 at that position at which the heating demand was met. In another example, a current position of the VGD 434 may result in a heating capacity that is less than the desired (or determined) heating capacity. In such a scenario, the actuation signal provided by the controller 422 may adjust the current position of the VGD 434 to increase the heating capacity. The current position of the VGD 434 may be a partially closed position. The actuation signal may cause the actuator to progressively drive the VGD 434 from the current position towards the fully opened position. The actuator, based on the actuation signal, may open the VGD 434 in steps or increments until the heating demand is met or the fully open position is reached. While the VGD 434 is being progressively opened, the controller 422 may continue to monitor the temperature of the conditioning fluid leaving the condenser 406 to detect the changes in the heating capacity of the vapor compression system 700. When the heating capacity of the vapor compression system 700 matches the heating demand, the controller 422 may stop the actuation signal and maintain the VGD 434 at that position at which resulted the heating demand was met.

[0101] In some embodiments, the controller 422 may provide the actuation signals to the actuators of the PRV 432 and the VGD 434 to adjust the PRV 432 and the VGD 434 in combination for satisfying the heating demand. In some embodiments, the controller 422 may additionally or alternatively adjust an opening of the expansion device 408 (and / or the bypass valve 411) to control the heating capacity of the vapor compression system 700.

[0102] In some embodiments, the pump 416 may be controlled using a VSD. In such a scenario, the heating capacity of the vapor compression system 700 may additionally or alternatively be controlled by controlling pumping power of the pump 416. For example, the pumping power may be reduced by the controller 422 to reduce the heating capacity and the pumping power may be increased to increase the heating capacity.

[0103] The capacity controlled refrigerant vapor flowing from the compressor 404 to the condenser 406 transfers heat to the conditioning fluid entering the condenser 406. The refrigerant vapor condenses to a refrigerant liquid in the condenser 406 as a result of the heat transfer with the conditioning fluid entering the condenser 406. As a result, the conditioning fluid in the exchanger coil 702 is heated to satisfy the heating demand. The liquid refrigerant from the condenser 406 flows to the evaporator 410 via the second path 446, for example, through the pump 416 and then through the expansion device 408 (e.g., an expansion valve) and / or the bypass 409. The liquid refrigerant delivered to the evaporator 410 absorbs heat from the heating fluid entering the evaporator 410, and may undergo a phase change to a refrigerant vapor. The vapor refrigerant exits the evaporator 410 and returns to the compressor 404 to complete the cycle. While the vapor compression system 700 operates in the free heating mode, the controller 422 may monitor the heating capacity, periodically, continuously, or at somewhat random time intervals. If the current heating capacity deviates from the heating demand, the controller 422 may execute the capacity control program described above to adjust at least one of the PRV 432 and the VGD 434.

[0104] While the vapor compression system 700 operates in the free heating mode, the controller 422 may further monitor the temperature of the heating fluid entering the evaporator 410 to determine whether the free heating mode can be continued. In an exemplary scenario, while the vapor compression system 700 is operating in the free heating mode, the temperature of the heating fluid entering the evaporator 410 may fall below the second threshold temperature value. In such a scenario, the controller 422 may switch from the free heating mode to the normal heating mode. In another exemplary scenario, the controller 422 may determine that the heating capacity of the free heating mode may not be sufficient to satisfy the heating demand. In such a scenario, the controller 422 may switch from the free heating mode to the normal heating mode.

[0105] The controller 422 may again switch from the normal heating mode to the free heating mode when the temperature of the heating fluid entering the evaporator 410 becomes greater than or equal to the second threshold temperature value and when the heating capacity in the free heating mode becomes sufficient to satisfy the heating demand. In other words, when heating operation is required, the controller 422 may operate the vapor compression system 700 in the normal heating mode or the free heating mode in accordance with operating conditions (e.g., temperature of the heating fluid entering the evaporator 410, heating demand) of the vapor compression system 700.

[0106] In some other exemplary scenarios, while the vapor compression system 700 is operating in the free heating mode, the controller 422 may determine that the heating operation is no longer required. In such a scenario, the controller 422 may be configured to stop the circulation of the refrigerant in the refrigeration circuit 402. To stop the circulation of the refrigerant in the refrigeration circuit 402, the controller 422 may be configured to generate a control signal which when received by the pump 416 may cause the pump 416 to stop. As the compressor 404 was already deactivated and when the pump 416 is also deactivated, the refrigerant in the refrigeration circuit 402 stops circulating. Though FIGS. 4, 5, 6A, 6B, 7A, and 7B describe the use of separate vapor compression systems (e.g., chillers and boilers) for cooling and heating applications, in certain other embodiments, an HVAC&R system may be a heat pump that provides both heating and cooling functionalities with one refrigeration circuit (e.g., same as the refrigeration circuit 402). In such a scenario, the functionalities of the vapor compression systems 400 and 700 may be implemented using a single vapor compression system, which can maintain the load (e.g., the load 442 or the load 706) at a preset temperature by cooling or heating. Such a vapor compression system can be operable in the normal cooling mode, the free cooling mode, the normal heating mode, or the free heating mode, in accordance with embodiments of the present disclosure. Further, operation of such a vapor compression system is described in conjunction with FIGS. 10A-10D.

[0107] Though the vapor compression system 700 is shown to include the pump 416 and the three-way valve 418, the scope of the disclosure is not limited the illustrated embodiment. In some embodiments, the vapor compression system 700 may not include the pump 416 and the three-way valve 418. In such scenarios, a different pressure difference generator may maintain the flow of the liquid refrigerant between the condenser 406 and the evaporator 410. For example, the flow of the liquid refrigerant between the condenser 406 and the evaporator 410 may be maintained due to a pressure difference between the condenser 406 and the evaporator 410 even when the compressor 404 is not active (e.g., in an OFF state). The pressure difference between the condenser 406 and the evaporator 410 may be caused by a height difference between the condenser 406 and the evaporator 410. Thus, the refrigerant may flow naturally from the condenser 406 to the evaporator 410 when the compressor 404 is stopped, maintaining a flow of the refrigerant in the refrigeration circuit 402. In accordance with present embodiments, the vapor compression system 700 may be operational without using the pump 416 in the normal cooling mode or the free cooling mode based on ambient temperature conditions.

[0108] FIG. 8 represents a flow chart of a method 800 for controlling capacity of an HVAC&R system (e.g., chiller) operating in the free cooling mode, in accordance with an embodiment of the present disclosure. While the method 800 is illustrated as starting at 801 (a starting point for the illustrated procedure) and flowing from there, one of ordinary skill in the art will understand that the method 800 may be continuous and / or repetitive or include continuous and / or repetitive components. For example, temperatures may be continually (e.g., periodically) monitored, as represented by block 802, and changes in temperature may change the operational step of the method 800 or cause portions of the method 800 to repeat.

[0109] In some embodiments, operations 802-814 of the method 800 may be performed by one or more components of the vapor compression system 400 used for a cooling application, as shown in FIGS. 4, 6A, and 6B. The illustrated embodiment of the method 800 is merely an example. Therefore, it should be understood that any of a variety of operations may be omitted, re-sequenced, and / or added while remaining within the scope of the present disclosure. Further, for the sake of brevity, it is assumed that the controller 422 has determined that cooling operation is desired (e.g., required) and performs the method 800 for executing the cooling operation.

[0110] At 802, a temperature of the cooling fluid entering the condenser 406 is monitored. The controller 422 (e.g., control circuitry) may be configured to monitor the temperature of the cooling fluid entering the condenser 406 as described in the foregoing description of FIGS. 4, 6A, and 6B. The controller 422 may monitor the temperature of the cooling fluid entering the condenser 406 periodically, at random time intervals, or continuously based on sensed data generated by the temperature sensor SI.

[0111] At 804, the controller 422 may determine whether the temperature of the cooling fluid entering the condenser 406 is less than the first threshold temperature value. If at 804, the controller 422 determines that the temperature of the cooling fluid entering the condenser 406 is greater than the first threshold temperature value, control proceeds to 806.

[0112] At 806, the vapor compression system 400 (e.g., the HVAC&R system) is selectively operated in the normal cooling mode in which the compressor 404 is in an active state (e.g., the compressor 404 is in an ON state). The controller 422 (e.g., control circuitry) may be configured to selectively operate the vapor compression system 400 in the normal cooling mode. During the normal cooling mode, the motor 412 driving the compressor 404 is ON, and hence the compressor 404 performs the compression operation on the refrigerant entering the compressor 404. In a scenario, where the vapor compressor system 400 includes the pump 416, the pump 416 is deactivated in the normal cooling mode. Working of the vapor compression system 400 in the normal cooling mode is described in the foregoing description of FIG. 6A. The controller 422 continues to monitor the temperature of the cooling fluid entering the condenser 406 at 802 so as to detect any changes in the temperature, which may require switching the vapor compression system 400 to the free cooling mode.

[0113] If at 804, the controller 422 determines that the temperature of the cooling fluid entering the condenser 406 is less than or equal to the first threshold temperature value, control proceeds to 808. At 808, the controller 422 may determine whether the cooling capacity of the free cooling mode is sufficient to satisfy the cooling demand. If at 808, the controller 422 determines that the cooling capacity of the free cooling mode is not sufficient to satisfy the cooling demand, control proceeds to 806. However, if at 808, the controller 422 determines that the cooling capacity of the free cooling mode is sufficient to satisfy the cooling demand, control proceeds to 810. As previously noted, the method 800 may include continuous and repetitive aspects. For example, while the flow chart of the method 800 does not illustrate arrows depicting this, the method 800 may continuously or periodically return (from essentially any point in the method 800) to 808 and change operation (e.g., from free cooling mode to normal cooling mode) based on whether the free cooling mode is sufficient to satisfy cooling demand.

[0114] At 810, the vapor compression system 400 (e.g., the HVAC&R system) is selectively operated in the free cooling mode in which the compressor 404 is not active (e.g., in an OFF state) and the refrigerant is circulated through the refrigeration circuit 402, including through the compressor 404 without being motivated by the compressor 404. The controller 422 (e.g., control circuitry) may be configured to selectively operate the vapor compression system 400 in the free cooling mode. During the free cooling mode, the motor 412 driving the compressor 404 is not active (e.g., in an OFF state), and hence the compression operation of the compressor 404 is halted. Further, when the vapor compression system 400 includes the pump 416, the controller 422 (e.g., control circuitry) may be configured to activate the pump 416 so as to circulate the refrigerant through the refrigeration circuit 402 when the motor 412 driving the compressor 404 is stopped. The activated pump 416 may pressurize the refrigerant to cause the refrigerant to flow through the refrigeration circuit 402. Further, as the motor 412 driving the compressor 404 is stopped, the refrigerant flows freely through the impeller 506 of the compressor 404. Working of the compressor 404 in the free cooling mode is described in the foregoing description of FIG. 6B. It should be noted that the pump 416 may also be representative of a pressure difference generator that is not a pump.

[0115] As the cooling demand may vary with time, the controller 422 may continue to execute 808 to check whether the cooling capacity of the free cooling mode is sufficient to satisfy the cooling demand. If required, the controller 422 may switch the vapor compression system 400 from the free cooling mode to the normal cooling mode.

[0116] At 812, the controller 422 may determine whether the cooling capacity is essentially the same as (e.g., within a threshold, an error, or a variance) the cooling demand. If at 812, the controller 422 determines that the cooling capacity is essentially the same as the cooling demand, control remains at 812. However, if at 812, the controller 422 determines that the cooling capacity is not essentially the same as the cooling demand, control proceeds to 814. At 814, the PRV 432, the VGD 434, or both is adjusted to control the cooling capacity during the free cooling mode. The controller 422 (e.g., control circuitry) may be configured to adjust the PRV 432, the VGD 434, or both to control the cooling capacity of the vapor compression system 400 during the free cooling mode. Control then passes to 812 of the method 800. The PRV 432 and / or the VGD 434 are adjusted to a position at which that the cooling capacity satisfies the cooling demand. Adjustment of the PRV 432 and / or the VGD 434 by the controller 422 to control the cooling capacity of the vapor compression system 400 during the free cooling mode is described in the foregoing description of FIG. 6B.

[0117] It will be understood by a person of ordinary skill in the art that the controller 422 can execute operations 802, 804, 808, and 812 periodically, at substantially random time intervals, or continuously based on sensed data received by controller 422.

[0118] FIG. 9 represents a flow chart of a method 900 for controlling heating capacity of an HVAC&R system (e.g., boiler) operating in the free heating mode, in accordance with an embodiment of the present disclosure. While the method 900 is illustrated as starting at 901 (a starting point for the illustrated procedure) and flowing from there, one of ordinary skill in the art will understand that the method 900 may be continuous and / or repetitive or include continuous and / or repetitive components. For example, temperatures are continually (e.g., periodically) being monitored, as represented by block 902, and changes in temperature may change the operational step of the method 900 or cause portions of the method 900 to repeat.

[0119] In some embodiments, operations 902-914 of the method 900 may be performed by one or more components of the vapor compression system 700 used for a heating application as shown in FIGS. 7A and 7B. The illustrated embodiment of the method 900 is merely an example. Therefore, it should be understood that any of a variety of operations may be omitted, re-sequenced, and / or added while remaining within the scope of the present disclosure. Further, for the sake of brevity, it is assumed that the controller 422 has determined that heating operation is required and performs the method 900 for executing the heating operation.

[0120] At 902, a temperature of the heating fluid entering the evaporator 410 is monitored. The controller 422 (e.g., control circuitry) may be configured to monitor the temperature of the heating fluid entering the evaporator 410 as described in the foregoing description of FIGS. 7A and 7B. The controller 422 may monitor the temperature of the heating fluid entering the evaporator 410 periodically, at random time intervals, or continuously based on sensed data generated by the temperature sensor S2.

[0121] At 904, the controller 422 may determine whether the temperature of the heating fluid entering the evaporator 410 is greater than the second threshold temperature value. If at 904, the controller 422 determines that the temperature of the heating fluid entering the evaporator 410 is less than the second threshold temperature value, control proceeds to 906.

[0122] At 906, the vapor compression system 700 is selectively operated in the normal heating mode in which the compressor 404 is in an active state (e.g., the compressor 404 is in an ON state). The controller 422 (e.g., control circuitry) may be configured to selectively operate the vapor compression system 700 in the normal heating mode. During the normal heating mode, the motor 412 driving the compressor 404 is ON, and hence the compressor 404 performs the compression operation on the refrigerant entering the compressor 404. Further, when the vapor compression system 700 includes the pump 416, the pump 416 is deactivated in the normal heating mode. Working of the vapor compression system 700 in the normal heating mode is described in the foregoing description of FIG. 7A. The controller 422 continues to monitor the temperature of the heating fluid entering the evaporator 410 so as to detect any changes in the temperature, which may require to switch the vapor compression system 700 to the free heating mode. If at 904, the controller 422 determines that the temperature of the heating fluid entering the evaporator 410 is greater than or equal to the second threshold temperature value, control proceeds to 908.

[0123] At 908, the controller 422 may determine whether the heating capacity of the free heating mode is sufficient to satisfy the heating demand. If at 908, the controller 422 determines that the heating capacity of the free heating mode is not sufficient to satisfy the heating demand, control proceeds to 906. However, if at 908, the controller 422 determines that the heating capacity of the free heating mode is sufficient to satisfy the heating demand, control proceeds to 910. As previously noted, the method 900 may include continuous and repetitive aspects. For example, while the flow chart of the method 900 does not illustrate arrows depicting this, the method 900 may continuously or periodically return (from essentially any point in the method 900) to 908 and change operation (e.g., from free heating mode to normal heating mode) based on whether the free heating mode is sufficient to satisfy heating demand.

[0124] At 910, the vapor compression system 700 is selectively operated in the free heating mode in which the compressor 404 is not active (e.g., in an OFF state) and the refrigerant is circulated through the refrigeration circuit 402, including through the compressor 404 without being motivated by the compressor 404. The controller 422 (e.g., control circuitry) may be configured to selectively operate the vapor compression system 700 in the free heating mode. During the free heating mode, the motor 412 driving the compressor 404 is not active (e.g., in an OFF state), and hence the compression operation of the compressor 404 is halted. Further, when the vapor compression system 700 includes the pump 416, the controller 422 (e.g., control circuitry) may be configured to activate the pump 416 so as to circulate the refrigerant through the refrigeration circuit 402 when the motor 412 driving the compressor 404 is stopped. The activated pump 416 may pressurize the refrigerant to cause the refrigerant to flow through the refrigeration circuit 402. Further, as the motor 412 driving the compressor 404 is stopped, the refrigerant flows freely through the impeller 506 of the compressor 404. Working of the compressor 404 in the free heating mode is described in the foregoing description of FIG. 7B. It should be noted that the pump 416 may also be representative of a pressure difference generator that is not a pump.

[0125] As the heating demand may vary with time, the controller 422 may continue to execute 908 to check whether the heating capacity of the free heating mode is sufficient to satisfy the heating demand. If required, the controller 422 may switch the vapor compression system 700 from the free heating mode to the normal heating mode.

[0126] At 912, the controller 422 may determine whether the heating capacity is essentially the same as (e.g., within a threshold, an error, or a variance) the heating demand. If at 912, the controller 422 determines that the heating capacity is essentially the same as the heating demand, control remains at 912. However, if at 912, the controller 422 determines that the heating capacity is not essentially the same as the heating demand, control proceeds to 914.

[0127] At 914, the PRV 432, the VGD 434, or both is adjusted to control the heating capacity during the free heating mode. The controller 422 (e.g., control circuitry) may be configured to adjust the PRV 432, the VGD 434, or both to control the heating capacity of the vapor compression system 700 during the free heating mode. Control then passes to 912 of the method 900. The PRV 432 and / or the VGD 434 are adjusted to a position at which that the heating capacity satisfies the heating demand. Adjustment of the PRV 432 and / or the VGD 434 by the controller 422 to control the heating capacity of the vapor compression system 700 during the free heating mode is described in the foregoing description of FIG. 7B.

[0128] It will be understood by a person of ordinary skill in the art that the controller 422 can execute operations 902, 904, 908, and 912 periodically, at substantially random time intervals, or continuously based on sensed data received by controller 422. FIGS. 10A and 10B collectively represent a flow chart of a method 1000 to control cooling capacity of an HVAC&R system (e.g., heat pump) during free cooling mode and free heating mode, in accordance with an embodiment of the present disclosure. The method 1000 is depicted as beginning at 1001 but may iterate, repeat, and so forth. In some embodiments, operations 1002-1030 of the method 1000 may be performed by one or more components of a heat pump (also referred to as the HVAC&R system). The heat pump may be similar to the vapor compression system 400 or the vapor compression system 700 except for the fact that heat pump can provide both cooling and heating using the single refrigeration circuit 402. During the cooling operation, the load is cooled based on thermal heat exchange between a conditioning fluid and the refrigerant in the evaporator 410, whereas during heating operation, the load is heated based on thermal heat exchange between a conditioning fluid and the refrigerant in the condenser 406. The illustrated embodiment of the method 1000 is merely an example. Therefore, it should be understood that any of a variety of operations may be omitted, re-sequenced, and / or added while remaining within the scope of the present disclosure.

[0129] With reference to FIG. 10A, at 1002, the controller 422 may determine whether a cooling operation is required. If at 1002, the controller 422 determines that the cooling operation is required, control passes to 1004. During the cooling operation, the conditioning fluid passing through the evaporator 410 is used to cool a load. The cooling operation of the heat pump is described using the vapor compression system 400.

[0130] At 1004, a temperature of the cooling fluid entering the condenser 406 is monitored. The controller 422 (e.g., control circuitry) may be configured to monitor the temperature of the cooling fluid entering the condenser 406 as described in the foregoing description of FIGS. 4, 6A, and 6B. The controller 422 may monitor the temperature of the cooling fluid entering the condenser 406 periodically, at substantially random time intervals, or continuously based on sensed data generated by the temperature sensor SI.

[0131] At 1006, the controller 422 may determine whether the temperature of the cooling fluid entering the condenser 406 is less than the first threshold temperature value. If at 1006, the controller 422 determines that the temperature of the cooling fluid entering the condenser 406 is greater than the first threshold temperature value, control proceeds to 1008.

[0132] At 1008, the HVAC&R system is selectively operated in the normal cooling mode in which the compressor 404 is active (e.g., in an ON state). The controller 422 (e.g., control circuitry) may be configured to selectively operate the HVAC&R system in the normal cooling mode. During the normal cooling mode, the motor 412 driving the compressor 404 is active (e.g., in an ON state), and hence the compressor 404 performs the compression operation on the refrigerant entering the compressor 404. In a scenario, where the vapor compressor system 400 includes the pump 416, the pump 416 is deactivated in the normal cooling mode. Working of the vapor compression system 400 in the normal cooling mode is described in the foregoing description of FIG. 6A. The controller 422 continues to monitor the temperature of the cooling fluid entering the condenser 406 at 1002 so as to detect any changes in the temperature, which may require to switch the vapor compression system 400 to the free cooling mode.

[0133] If at 1006, the controller 422 determines that the temperature of the cooling fluid entering the condenser 406 is less than or equal to the first threshold temperature value, control proceeds to 1010.

[0134] At 1010, the controller 422 may determine whether the cooling capacity of the free cooling mode is sufficient to satisfy the cooling demand. If at 1010, the controller 422 determines that the cooling capacity of the free cooling mode is not sufficient to satisfy the cooling demand, control proceeds to 1008. However, if at 1010, the controller 422 determines that the cooling capacity of the free cooling mode is sufficient to satisfy the cooling demand, control proceeds to 1012.

[0135] At 1012, the HVAC&R system is selectively operated in the free cooling mode in which the compressor 404 is not active (e.g., in an OFF state) and the refrigerant is circulated through the refrigeration circuit 402, for example, via the compressor 404. The controller 422 (e.g., control circuitry) may be configured to selectively operate the vapor compression system 400 in the free cooling mode. During the free cooling mode, the motor 412 driving the compressor 404 is not active (e.g., in an OFF state), and hence the compression operation of the compressor 404 is halted. Further, when the vapor compression system 400 includes the pump 416, the controller 422 (e.g., control circuitry) may be configured to activate the pump 416 so as to circulate the refrigerant through the refrigeration circuit 402 when the motor 412 driving the compressor 404 is stopped. The activated pump 416 may pressurize the refrigerant to cause the refrigerant to flow through the refrigeration circuit 402. Further, as the motor 412 driving the compressor 404 is stopped, the refrigerant flows freely through the impeller 506 of the compressor 404. Working of the compressor 404 in the free cooling mode is described in the foregoing description of FIG. 6B.

[0136] As the cooling demand may vary with time, the controller 422 may continue to execute 1010 to check whether the cooling capacity of the free cooling mode is sufficient to satisfy the cooling demand. If required, the controller 422 may switch the vapor compression system 400 from the free cooling mode to the normal cooling mode.

[0137] At 1014, the controller 422 may determine whether the cooling capacity is essentially the same (e.g., the same, within a threshold range, within a variance, within a tolerance) as the cooling demand. If at 1014, the controller 422 determines that the cooling capacity is essentially the same as the cooling demand, control remains at 1014. However, if at 1014, the controller 422 determines that the cooling capacity is not essentially the same as the cooling demand, control proceeds to 1016.

[0138] At 1016, at least one of the PRV 432 and the VGD 434 is adjusted to control the cooling capacity during the free cooling mode. The controller 422 (e.g., control circuitry) may be configured to adjust at least one of the PRV 432 and the VGD 434 to control the cooling capacity of the HVAC&R system during the free cooling mode. Control then passes to 1014. The PRV 432 and / or the VGD 434 are adjusted to a position at which that the cooling capacity satisfies the cooling demand. Adjustment of the PRV 432 and / or the VGD 434 by the controller 422 to control the cooling capacity of the HVAC&R system during the free cooling mode is described in the foregoing description of FIG. 6B.

[0139] It will be understood by a person of ordinary skill in the art that the controller 422 can execute operations 1004, 1006, 1010, and 1014 periodically, at random time intervals, or continuously based on sensed data received by controller 422. If at 1002, the controller 422 determines that the cooling operation is not required and heating operation is required, control passes to 1018 shown in FIG. 10B. During the heating operation, the conditioning fluid passing through the condenser 406 is used to cool the load. The heating operation of the heat pump is described using the vapor compression system 700.

[0140] At 1018, a temperature of the heating fluid entering the evaporator 410 is monitored. The controller 422 (e.g., control circuitry) may be configured to monitor the temperature of the heating fluid entering the evaporator 410 as described in the foregoing description of FIGS. 7A and 7B. The controller 422 may monitor the temperature of the heating fluid entering the evaporator 410 periodically, at random time intervals, or continuously based on sensed data generated by the temperature sensor S2.

[0141] At 1020, the controller 422 may determine whether the temperature of the heating fluid entering the evaporator 410 is greater than the second threshold temperature value. If at 1020, the controller 422 determines that the temperature of the heating fluid entering the evaporator 410 is less than the second threshold temperature value, control proceeds to 1022.

[0142] At 1022, the vapor compression system 700 is selectively operated in the normal heating mode in which the compressor 404 is ON. The controller 422 (e.g., control circuitry) may be configured to selectively operate the vapor compression system 700 in the normal heating mode. During the normal heating mode, the motor 412 driving the compressor 404 is ON, and hence the compressor 404 performs the compression operation on the refrigerant entering the compressor 404. Further, when the vapor compression system 700 includes the pump 416, the pump 416 is deactivated in the normal heating mode. Working of the vapor compression system 700 in the normal heating mode is described in the foregoing description of FIG. 7A. The controller 422 continues to monitor the temperature of the heating fluid entering the evaporator 410 so as to detect any changes in the temperature, which may require to switch the vapor compression system 700 to the free heating mode.

[0143] If at 1020, the controller 422 determines that the temperature of the heating fluid entering the evaporator 410 is greater than or equal to the second threshold temperature value, control proceeds to 1024. At 1024, the controller 422 may determine whether the heating capacity of the free heating mode is sufficient to satisfy the heating demand. If at 1024, the controller 422 determines that the heating capacity of the free heating mode is not sufficient to satisfy the heating demand, control proceeds to 1022. However, if at 1024, the controller 422 determines that the heating capacity of the free heating mode is sufficient to satisfy the heating demand, control proceeds to 1026.

[0144] At 1026, the HVAC&R system is selectively operated in the free heating mode in which the compressor 404 is not active (e.g., in an OFF state) and the refrigerant is circulated through the refrigeration circuit 402, for example, via the compressor 404. The controller 422 (e.g., control circuitry) may be configured to selectively operate the vapor compression system 700 in the free heating mode. During the free heating mode, the motor 412 driving the compressor 404 is not active (e.g., in an OFF state), and hence the compression operation of the compressor 404 is halted. Further, when the vapor compression system 700 includes the pump 416, the controller 422 (e.g., control circuitry) may be configured to activate the pump 416 so as to circulate the refrigerant through the refrigeration circuit 402 when the motor 412 driving the compressor 404 is stopped. The activated pump 416 may pressurize the refrigerant to cause the refrigerant to flow through the refrigeration circuit 402. Further, as the motor 412 driving the compressor 404 is stopped, the refrigerant flows freely through the impeller 506 of the compressor 404. Working of the compressor 404 in the free heating mode is described in the foregoing description of FIG. 7B.

[0145] As the heating demand may vary with time, the controller 422 may continue to execute 1024 to check whether the heating capacity of the free heating mode is sufficient to satisfy the heating demand. If required, the controller 422 may switch the vapor compression system 700 from the free heating mode to the normal heating mode.

[0146] At 1028, the controller 422 may determine whether the heating capacity is essentially the same as the heating demand. If at 1028, the controller 422 determines that the heating capacity is same as the heating demand, control remains at 1028. However, if at 1028, the controller 422 determines that the heating capacity is not same as the heating demand, control proceeds to 1030. At 1030, at least one of the PRV 432 and the VGD 434 is adjusted to control the heating capacity during the free heating mode. The controller 422 (e.g., control circuitry) may be configured to adjust at least one of the PRV 432 and the VGD 434 to control the heating capacity of the HVAC&R system during the free heating mode. Control then passes to 1028. The PRV 432 and / or the VGD 434 are adjusted to a position at which that the heating capacity satisfies the heating demand. Adjustment of the PRV 432 and / or the VGD 434 by the controller 422 to control the heating capacity of the vapor compression system 700 during the free heating mode is described in the foregoing description of FIG. 7B.

[0147] It will be understood by a person of ordinary skill in the art that the controller 422 can execute operations 1018, 1020, 1024, and 1028 periodically, at random time intervals, or continuously based on sensed data received by controller 422.

[0148] FIG. 11 is a flow chart of a method 1100 to prevent the conditioning fluid from freezing in the evaporator 410 of an HVAC&R system, according to some embodiments of the present disclosure. The method 1100 is depicted as beginning at 1101 but may iterate, repeat, and so forth. In some embodiments, operations 1102 -1108 of the method 1100 may be performed by one or more components of the vapor compression system 400, 700 (e.g., the HVAC&R system). The illustrated embodiment of the method 1100 is merely an example. Therefore, it should be understood that any of a variety of operations may be omitted, re-sequenced, and / or added while remaining within the scope of the present disclosure

[0149] At 1102, the controller 422 may determine whether the conditioning fluid can freeze in the tubes of the evaporator 410. This determination may be based on temperature measurements, liquid levels (e.g., in the evaporator), and so forth, as detected directly or indirectly by any of various sensors. If at 1102, the controller 422 determines that there is no likelihood for the conditioning fluid to freeze in the tubes of the evaporator 410, control remains at 1102. However, if at 1102, the controller 422 determines that there is a likelihood for the conditioning fluid to freeze in the tubes of the evaporator 410, control passes to 1104.

[0150] At 1104, at least one of the PRV 432, the VGD 434, and the expansion device 408 are adjusted to the fully closed position. The controller 422 may be configured to adjust at least one of the PRV 432, the VGD 434, the expansion device 408, and / or the bypass valve 411 to the fully closed position so as to prevent the refrigerant from flowing into the evaporator 410, which in turn prevents the conditioning fluid from freezing in the tubes of the evaporator 410. Operations of the controller 422 to prevent the conditioning fluid from freezing in the tubes of the evaporator 410 are described in the foregoing description of FIG. 6B.

[0151] At 1106, the controller 422 may again determine whether the conditioning fluid can freeze in the tubes of the evaporator 410. If at 1106, the controller 422 determines that there is still a likelihood for the conditioning fluid to freeze, control remains at 1106. However, if at 1106, the controller 422 determines that there is no likelihood for the conditioning fluid to freeze, control passes to 1108.

[0152] At 1108, at least one of the PRV 432, the VGD 434, and the expansion device 408 are adjusted to the fully or partially opened position. The controller 422 may be configured to adjust at least one of the PRV 432, the VGD 434, and the expansion device 408 to the fully or partially opened position so as start refrigerant circulation again. The control passes to 1102.

[0153] Present disclosure offers many technical advancements and advantages. For example, the capacity control program and / or algorithm implemented by the controller 422 allows the cooling capacity to be controlled during free cooling operation and / or heating capacity to be controlled during free heating operation. In conventional free cooling / heating operation, compressor though inactive (e.g., in an OFF state) is usually bypassed. However, in the present disclosure refrigerant is passed through the compressor 404 which is inactive (e.g., in an OFF state), and flow reductions devices, for example, the PRV 432 and / or the VGD 434, of the compressor 404 are used to control the cooling / heating capacity. In other words, the HVAC&R system of the present disclosure is capable of controlling cooling / heating capacity during free cooling / heating mode in accordance with changing ambient temperatures. The HVAC&R system of the present disclosure may have numerous applications, for example, in submarines where the temperature of evaporator conditioning fluid can be very low, for example, -2°C.

[0154] The construction and arrangement of the systems and methods as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, 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.). For example, the position of elements can be reversed or otherwise varied and the nature or number of discrete elements or positions can be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps can be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure.

[0155] The present disclosure contemplates methods, systems and program products on any machine-readable media for accomplishing various operations. The embodiments of the present disclosure can be implemented using existing computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwired system. Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machineexecutable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD- ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions.

[0156] Although the figures show a specific order of method steps, the order of the steps may differ from what is depicted. Also, two or more steps can be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.

Claims

Claims1. A heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system, comprising: a refrigeration circuit comprising an evaporator, a compressor, and a condenser configured to circulate refrigerant and facilitate heat exchange between the refrigerant and a conditioning fluid; a pre-rotation vane (PRV) at an inlet of the compressor, a variable geometry diffuser (VGD) at an outlet of the compressor, or both; and control circuitry configured to: selectively operate the HVAC&R system in a normal cooling mode or a free cooling mode, wherein: in the normal cooling mode, the control circuitry is configured to control the compressor in an active state to compress the refrigerant; in the free cooling mode, the control circuitry is configured to control the compressor in an inactive state such that the refrigerant is circulated through compressor via a pressure difference generator; and adjust the PRV, the VGD, or both to control a cooling capacity of the HVAC&R system in the free cooling mode.

2. The HVAC&R system of claim 1, wherein the compressor comprises: a rotating shaft configured to rotate about a rotation axis; a motor configured to drive the rotating shaft; and an impeller coupled to the rotating shaft.

3. The HVAC&R system of claim 2, wherein the control circuitry is configured to stop the motor to put the compressor in the inactive state in coordination with entering the free cooling mode.

4. The HVAC&R system of claim 3, wherein the pressure difference generator comprises a thermosiphon operation and, in the free cooling mode, the refrigerant flows through the impeller.

5. The HVAC&R system of one of claims 1 to 4, wherein the control circuitry is configured to operate the HVAC&R system in the free cooling mode based on a temperature of the conditioning fluid entering the condenser being within a range.

6. The HVAC&R system of claim 5, comprising a temperature sensor configured to detect the temperature of the conditioning fluid entering the condenser at a condenser inlet and provide a sensor signal indicating the temperature to the control circuitry.

7. The HVAC&R system of claim 5 or 6, wherein the range comprises temperature values less than or equal to a threshold temperature.

8. The HVAC&R system of one of claims 1 to 7, wherein the control circuitry is configured to adjust the PRV, the VGD, or both to a closed position based on conditions indicative of the conditioning fluid freezing in one or more tubes of the evaporator.

9. The HVAC&R system of claim 5, 6, or 7, comprising an expansion device, wherein the control circuitry is configured to adjust the expansion device to a closed position based on conditions indicative of the conditioning fluid potentially freezing in one or more tubes of the evaporator.

10. The HVAC&R system of one of claims 1 to 9, wherein the control circuitry is configured to adjust the PRV, the VGD, or both to control the cooling capacity of the HVAC&R system in the free cooling mode by adjusting the PRV, the VGD, or both between respective fully opened and fully closed positions.

11. The HVAC&R system of one of claims 1 to 10, wherein the pressure difference generator comprises a pump and the control circuitry is configured to activate the pump in coordination with activating the free cooling mode.

12. A method of controlling a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system comprising a refrigeration circuit including an evaporator, a compressor, and a condenser configured to circulate refrigerant and facilitate heat exchange between the refrigerant and a conditioning fluid, the method comprising: selectively operating, via control circuitry, the HVAC&R system in a normal cooling mode or a free cooling mode, wherein: in the free cooling mode, a compression operation of the compressor is inactive, and the refrigerant is circulated through the compressor, and in the normal cooling mode, the compression operation of the compressor is active, and the refrigerant is motivated through the refrigerant circuit by the compressor; and adjusting, via the control circuitry, a pre-rotation vane (PRV) at an inlet of the compressor and / or the variable geometry diffuser (VGD) to control a cooling capacity of the HVAC&R system in the free cooling mode.

13. The method of claim 12, comprising controlling, via the control circuitry, a pump to circulate the refrigerant in the free cooling mode.

14. The method of claim 12 or 13, comprising closing an expansion valve between the condenser and the evaporator based on detecting conditions indicative of potential freezing of the conditioning fluid.

15. The method of one of claims 12 to 14, comprising selectively operating, via the control circuitry, the HVAC&R system in a normal heating mode or a free heating mode, wherein: in the free heating mode, the compression operation of the compressor is inactive and the refrigerant is circulated through the compressor, and in the normal heating mode, the compression operation of the compressor is active, and the refrigerant is motivated through the refrigerant circuit by the compressor.

16. A heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system, comprising: a compressor comprising a pre-rotation vane (PRV) at an inlet of the compressor, a variable geometry diffuser (VGD) at an outlet of the compressor, or both; and control circuitry configured to: selectively operate the HVAC&R system in a normal heating mode or a free heating mode, wherein: in the free heating mode, the control circuitry is configured to control the compressor in an inactive state such that refrigerant is circulated through the compressor by a pressure difference generator, and in the normal heating mode, the control circuity is configured to control the compressor in an active state such that the refrigerant is circulated by the compressor; and adjust the PRV, the VGD, or both to control a heating capacity of the HVAC&R system in the free heating mode.

17. The HVAC&R system of claim 16, comprising an evaporator and a condenser, wherein the compressor, the evaporator, and the condenser form at least a part of a refrigeration circuit that circulates the refrigerant.

18. The HVAC&R system of claim 17, wherein the control circuitry is configured to operate the HVAC&R system in the free heating mode based on a temperature of a conditioning fluid at an inlet of the evaporator being greater than or equal to a first threshold value.

19. The HVAC&R system of claim 18, further comprising a temperature sensor configured to: detect the temperature of the heating fluid at the inlet of the evaporator; and provide a sensor signal indicating the detected temperature to the control circuitry.

20. The HVAC&R system of one of claims 16 to 19, wherein the pressure difference generator comprises a pump, wherein the control circuitry is configured to activate the pump to circulate the refrigerant in coordination with activation of the free heating mode.

Images