Natural cooling operation of a chiller

Abstract

A heating, ventilation, air conditioning and / or refrigeration (HVAC&R) system (10) is disclosed that includes a vapor compression system (14) having an evaporator (38), a condenser (34) and a compressor (32). The compressor (34) is configured to direct refrigerant therethrough in a normal operating mode of the vapor compression system (14) and in a free cooling mode of the vapor compression system (14). The HVAC&R system (10) also includes a controller (40) configured to implement power supply to a motor (50) of the compressor (34) in the normal operating mode and to suspend power supply to the motor (50) of the compressor (34) in the free cooling mode.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to and the benefit of U.S. Provisional Application Serial No. 63 / 081,565, entitled “FREE COOLING OPERATION OF A CHILLER” and filed September 22, 2020, which is hereby incorporated by reference in its entirety for all purposes. BACKGROUND

[0003] This section is intended to introduce the reader to various aspects of art that can be related to various aspects of the present disclosure that are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

[0004] The present application generally relates to chiller systems, and more particularly to free cooling operation of a chiller system.

[0005] Chiller systems, or vapor-compression systems, utilize a working fluid (e.g., a refrigerant) that changes phase between vapor, liquid, and combinations thereof in response to being exposed to different temperatures and pressures within components of the chiller system. A chiller system can include an evaporator configured to place a working fluid (e.g., a refrigerant) in a heat exchange relationship with a conditioning fluid (e.g., water) such that the working fluid absorbs heat from the conditioning fluid. The conditioning fluid cooled by the working fluid can then be delivered to a conditioning device and / or conditioned environment served by the chiller system. In such applications, the conditioning fluid can pass through a downstream device, such as an air handler, to condition other fluids, such as air within a building.

[0006] In certain chiller systems, a cooling fluid (e.g., water) can additionally or alternatively be used to cool the working fluid. For example, a chiller system can include a cooling tower (or other water or cooling fluid source) configured to provide a cooling fluid to a condenser of the chiller system. The cooling fluid can be cooled in the cooling tower (or other water or cooling fluid source) via ambient air, and the condenser can place the cooling fluid from the cooling tower in a heat exchange relationship with a refrigerant to transfer heat from the refrigerant to the cooling fluid. A compressor can be positioned between the condenser and the evaporator and can be powered to condition the pressure of the refrigerant and circulate the refrigerant between components of the chiller system.

[0007] In certain systems, natural cooling operation can be initiated during certain conditions, such as when ambient air temperatures are relatively low (e.g., in the spring, winter, and / or fall). When ambient air temperatures are relatively low, cooling demand of a chiller can be reduced and / or operating conditions can enable the chiller to operate with sufficient cooling capacity without powering a compressor. For example, because cooling fluid provided by a cooling tower can have a relatively low temperature when ambient temperatures of outside air are relatively low, a chiller system can operate to cool a conditioning fluid with sufficient capacity without powering a compressor. In conventional chiller systems utilizing natural cooling, power to a compressor of the chiller system can be terminated and refrigerant can be directed to bypass the compressor via a compressor bypass valve or the like. In conventional systems employing natural cooling, directing refrigerant to bypass the compressor can avoid pressure losses that would otherwise reduce cooling capacity of the chiller system. However, it is now recognized that conventional or traditional chiller systems utilizing conventional or traditional natural cooling techniques can include additional components (e.g., compressor bypass valves) that increase part count and cost of the system, can be limited in the type of coolant that can be used, and can be improved in available cooling capacity. SUMMARY

[0008] The following sets forth a summary of certain embodiments disclosed herein. It will be appreciated that these presented aspects are only meant as summaries of certain embodiments and are not meant to limit the scope of the disclosure. In fact, the disclosure can encompass various aspects not set forth below.

[0009] In one embodiment, a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system includes a vapor compression system having an evaporator, a condenser, and a compressor. The compressor is configured to direct refrigerant therethrough in a normal operating mode of the vapor compression system and in a natural cooling mode of the vapor compression system. The HVAC&R system also includes a controller configured to implement power supply to a motor of the compressor in the normal operating mode and to suspend power supply to the motor of the compressor in the natural cooling mode.

[0010] In another embodiment, a method of operating a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system includes supplying power to a motor of a compressor of a vapor compression system in response to a normal operating mode of the HVAC&R system such that the compressor is driven by the motor and biases refrigerant between an evaporator of the vapor compression system and a condenser of the vapor compression system. The method also includes inhibiting power to the motor of the compressor of the vapor compression system in response to a natural cooling mode of the HVAC&R system such that a rotor of the compressor is suspended and enables refrigerant to pass through the compressor.

[0011] In another embodiment, a chiller system includes a compressor configured to circulate a refrigerant through a refrigerant circuit, an electric motor of the compressor, and a controller configured to enable a supply of power to the electric motor of the compressor in response to a normal operating mode of the chiller system and disable the supply of power to the electric motor of the compressor in response to a free cooling mode of the chiller system. BRIEF DESCRIPTION OF DRAWINGS

[0012] Various aspects of the disclosure can be better understood after a reading of the following detailed description together with reference to the drawings, in which:

[0013] Figure 1 is a perspective view of an embodiment of a building that can utilize a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system in a commercial environment in accordance with an aspect of the present disclosure;

[0014] Figure 2 is a perspective view of an embodiment of a vapor compression system (sometimes referred to as a chiller system) for use in Figure 1 is a perspective view of an embodiment of a vapor compression system (sometimes referred to as a chiller system) for use in

[0015] Figure 3 is a perspective view of an embodiment of a vapor compression system (sometimes referred to as a chiller system) for use in Figure 2 is a schematic view of an embodiment of a vapor compression system of

[0016] Figure 4 is a schematic view of an embodiment of a vapor compression system of Figure 2

[0017] Figure 5 is a schematic view of an embodiment of a portion of a vapor compression system of Figure 2

[0018] Figure 6 is a schematic view of an embodiment of a vapor compression system of Figure 2

[0019] Figure 7 is a flowchart illustrating a method of operating a vapor compression system of Figure 2 DETAILED DESCRIPTION

[0020] ​​​​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 can 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.

[0021] 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 can 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.

[0022] Embodiments of the present disclosure relate to heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) systems that utilize a vapor compression system (hereinafter referred to in some instances as a chiller or chiller system). More particularly, embodiments of the present disclosure relate to a natural cooling mode or operation of a chiller.

[0023] The presently disclosed chiller includes a natural cooling mode in which a passive (e.g., unpowered) compressor of the HVAC&R system receives a flow of refrigerant therethrough. That is, during the natural cooling mode, an electric motor configured to drive rotation of the compressor can not be powered or operated. For example, the chiller is configured to circulate a working fluid (e.g., refrigerant) through a compressor, an evaporator, a condenser, and an expansion valve of the chiller, among other possible components. The evaporator can be in a heat exchange relationship with a conditioning fluid (e.g., water) such that the refrigerant absorbs heat from the conditioning fluid. The conditioning fluid can be circulated between the evaporator and a structure, such as a building, where the conditioning fluid is used to cool a flow of air delivered to conditioned spaces of the structure. In some embodiments, an air handling unit (AHU) of the HVAC&R system can receive the conditioning fluid from the chiller and utilize the conditioning fluid to cool a flow of air delivered to the conditioned spaces. The conditioning fluid can then be returned to the evaporator to be cooled again.

[0024] The refrigerant can circulate from the evaporator toward the compressor, which is powered in the normal operating mode of the chiller to increase the temperature and pressure of the refrigerant before delivering it to the condenser. Upon receiving the refrigerant, the condenser places the refrigerant in heat exchange relationship with a cooling fluid (e.g., water) that is circulated between the condenser and a cooling source, such as a cooling tower. The cooling fluid absorbs heat from the refrigerant in the condenser, causing the refrigerant in vapor form to condense into a liquid. The heated cooling fluid can be directed from the condenser to the cooling source (e.g., cooling tower) to be cooled for delivery back to the condenser. For example, the cooling tower can utilize ambient air to cool the cooling fluid. Other cooling sources are also possible, such as an underground cooling reservoir.

[0025] Under certain conditions, for example, during the fall, winter, and / or spring, ambient air or other cooling media can be relatively cool. The relatively cool ambient air can reduce the cooling demand of the chiller. Moreover, the relatively cool ambient air can cause the cooling fluid directed from the cooling source (e.g., cooling tower) to the condenser to be relatively cool. The cooling fluid having a relatively low temperature can cool and condense the refrigerant to such an extent that the chiller can provide sufficient cooling capacity to the building (e.g., through the evaporator, as described above) without powering the compressor. The operating mode in which the compressor is not powered to compress the refrigerant and force the refrigerant through the vapor compression system can be referred to as a natural cooling or natural cooling mode.

[0026] In conventional chillers employing natural cooling techniques, the refrigerant is directed to bypass the compressor during natural cooling conditions such that the compressor does not cause a significant pressure loss that would otherwise reduce the cooling capacity of the chiller. In accordance with the present disclosure, a natural cooling mode is employed in which the compressor is not powered (e.g., the motor of the compressor is not running) but the compressor is configured or designed to receive and direct the refrigerant therethrough. For example, the compressor can be configured such that when the motor of the compressor is not powered, the rotor of the compressor floats and freely rotates in response to receiving the refrigerant, thereby reducing, mitigating, or eliminating a pressure loss that would otherwise be caused by the compressor. In one embodiment, the compressor can include magnetic bearings that float the rotor of the compressor, or in an oil-free system, rolling element bearings. Additionally or alternatively, a variable geometry diffuser (VGD) and / or pre-rotation vanes (PRVs) of the compressor can open in response to the initiation of the natural cooling mode.

[0027] When the compressor motor is not powered during natural cooling mode, the number of parts, complexity, and / or cost of the chiller system is significantly reduced compared to conventional systems that employ a compressor bypass assembly for natural cooling operation by suspending the rotor of the compressor, opening the VGD and PRV, and directing refrigerant through the compressor. Moreover, the number of parts, complexity, and / or cost of the chiller is reduced without creating a significant pressure loss in the compressor. In this way, the present embodiments enable improved operation of the chiller and reduced manufacturing, operating, and / or maintenance costs associated with the chiller. Moreover, the presently described features enable the use of a wide range of refrigerants (e.g., low, medium, and high pressure refrigerants), including R-123, R-514A, R-1224yd, R-1233zd, R-134a, R-1234ze, R-1234yf, R-1311, R-32, R-410A, etc. Other features, such as falling film evaporators, expansion valve throttling, refrigerant pumps, etc., can be incorporated into the systems disclosed herein to improve cooling capacity and other aspects relative to conventional embodiments, and are described in detail below with reference to the accompanying drawings.

[0028] Turning now to the drawings, Figure 1 is a perspective view of an embodiment of a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system 10 in a building 12 for a typical commercial environment. The HVAC&R system can include a boiler 16 for supplying warm liquid to heat the building 12 and a vapor compression system 14 for supplying cooled liquid to cool the building 12. The vapor compression system 14 (sometimes referred to as a chiller) can circulate a working fluid (e.g., a refrigerant) that is cooled by a cooling fluid (e.g., a liquid, such as water) in a condenser of the vapor compression system 14 and heated by a conditioned fluid (e.g., a fluid, such as water) in an evaporator of the vapor compression system 14. The cooling fluid can be provided by a cooling tower that cools the cooling fluid via, for example, ambient air. The conditioned fluid, which is cooled by the working fluid as described above, can be used to cool a flow of air provided to a conditioned space of the building 12.

[0029] HVAC&R system 10 can also include an air distribution system that circulates air through building 12. The air distribution system can also include air return ducts 18, air supply ducts 20, and / or air handlers 22. In some embodiments, air handlers 22 can include heat exchangers that are connected to boiler 16 and vapor compression system 14 by conduits 24. Depending on the operating mode of HVAC&R system 10, the heat exchangers in air handlers 22 can receive heated liquid from boiler 16 or conditioned fluid (e.g., chilled liquid such as water) from vapor compression system 14. HVAC&R system 10 is shown as having a separate air handler on each floor of building 12, but in other embodiments, HVAC&R system 10 can include air handlers 22 and / or other components that can be shared between floors.

[0030] Vapor compression system 14 or chiller can include a compressor disposed between the evaporator and the condenser described above. The compressor can operate in a normal operating mode in which the compressor receives working fluid (e.g., refrigerant) and is powered to increase the temperature and pressure of the working fluid before delivering the working fluid to the condenser. In accordance with the present disclosure, the compressor can operate in a natural cooling mode when the cooling fluid (or, in other words, the ambient air used to cool the cooling fluid via a cooling tower) is at a sufficiently low temperature such that vapor compression system 14 can provide sufficient cooling capacity without powering the motor of the compressor to force refrigerant through vapor compression system 14.

[0031] For example, in a natural cooling mode, the compressor receives working fluid (e.g., refrigerant) but is not powered to force the refrigerant through it. Rather, the compressor is configured to enable the refrigerant to pass through it (e.g., via natural convection). To reduce or eliminate pressure losses in the compressor during the natural cooling mode, the compressor can be a centrifugal compressor that includes a rotor suspended via one or more magnetic bearings, or in an oil-free system, one or more rolling element bearings. Further, a variable geometry diffuser (VGD) and / or pre-rotation vanes (PRVs) of the centrifugal compressor can be opened in the natural cooling mode to enable passive refrigerant flow therethrough. Thus, while the motor of the centrifugal compressor is not powered during the natural cooling mode, the rotor of the centrifugal compressor can freely rotate in response to receiving refrigerant in the natural cooling mode. By configuring the centrifugal compressor as described above, the natural cooling mode can be utilized without the need for refrigerant to bypass the compressor, while still enabling the vapor compression system 14 to provide sufficient cooling capacity to the building 12. Thus, the presently contemplated embodiments enable efficient natural cooling while reducing the number of parts, pressure losses, and overall cost of conventional embodiments. Further, unlike conventional embodiments, the presently contemplated embodiments are compatible with a wide range of refrigerants, including R-123, R-514A, R-1224yd, R-1233zd, R-134a, R-1234ze, R-1234yf, R-1311, R-32, R-410A, and the like.

[0032] Figure 2 and Figure 3 is a schematic diagram of an embodiment of a vapor compression system 14 or chiller that can be used in an HVAC&R system 10 of Figure 1 The vapor compression system 14 can circulate refrigerant through a circuit that begins with a compressor 32, such as a centrifugal compressor. The circuit can also include a condenser 34, an expansion valve or device 36, and an evaporator 38. The vapor compression system 14 can further include a control panel 40 having an analog-to-digital (A / D) converter 42, a microprocessor 44, a non-volatile memory 46, and / or an interface board 48.

[0033] Some examples of fluids that can be used as refrigerants in the vapor compression system 14 are: hydrofluorocarbon (HFC)-based refrigerants, such as R-410A, R-407, R-134a, hydrofluoroolefins (HFO); “natural” refrigerants, such as ammonia (NH3), R-717, carbon dioxide (CO2), R-744; or hydrocarbon-based refrigerants, water vapor, or any other suitable refrigerant. Other possible refrigerants include R-123, R-514A, R-1224yd, R-1233zd, R-134a, R-1234ze, R-1234yf, R-1311, R-32, and R-410A. In some embodiments, the vapor compression system 14 can be configured to effectively utilize a refrigerant having a standard boiling point of about 19 degrees Celsius (66 degrees Fahrenheit) at one atmosphere of pressure, also referred to as a low-pressure refrigerant relative to medium-pressure refrigerants, such as R-134a. As used herein, “standard boiling point” can refer to a boiling temperature measured at one atmosphere of pressure.

[0034] In some embodiments, the vapor compression system 14 can use one or more of a variable speed drive (VSD) 52, an electric motor 50, the compressor 32, the condenser 34, an expansion valve or device 36, and / or the evaporator 38. The electric motor 50 can drive the compressor 32 during a standard operating mode and can be powered by the variable speed drive (VSD) 52. The VSD 52 receives alternating current (AC) power during the standard operating mode, where the AC power includes a particular fixed line voltage and a fixed line frequency from an AC power source, and provides power to the electric motor 50 having a variable voltage and frequency. In other embodiments, the electric motor 50 can be powered directly from an AC or direct current (DC) power source. The electric motor 50 can include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source, such as a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor, or another suitable motor. It should be noted that the electric motor 50 and / or the VSD 52 can be considered part of the compressor 32. That is, in instances in which the compressor 32 is described in the present disclosure as not receiving power during a natural cooling mode, it should be understood that the electric motor 50 and / or the VSD 52 can not receive power. However, other components of the compressor 32, such as a magnetic bearing configured to levitate a rotor of the compressor 32, can receive power in the natural cooling mode.

[0035] During the standard operating mode, the compressor 32 compresses refrigerant vapor and delivers the vapor through a discharge passage to the condenser 34. The refrigerant vapor delivered by the compressor 32 to the condenser 34 can transfer heat to a cooling fluid (e.g., water or air) in the condenser 34. As a result of the heat transfer with the cooling fluid, the refrigerant vapor can condense into refrigerant liquid in the condenser 34. The liquid refrigerant from the condenser 34 can flow through the expansion device 36 to the evaporator 38. In Figure 3In the illustrative embodiment, the condenser 34 is water-cooled and includes a tube bundle 54 connected to a cooling tower 56 that supplies cooling fluid to the condenser 34.

[0036] The liquid refrigerant delivered to the evaporator 38 can absorb heat from a conditioning fluid that is then directed to the load 62 (e.g., the building 12). That is, the conditioning fluid can be cooled by the refrigerant in the evaporator 38 and then can be used in the building 12 to condition an air stream provided for conditioning a space in the building 12. The liquid refrigerant in the evaporator 38 can undergo a phase change from liquid refrigerant to refrigerant vapor. As Figure 1 In the illustrative embodiment, the condenser 34 is water-cooled and includes a tube bundle 54 connected to a cooling tower 56 that supplies cooling fluid to the condenser 34. Figure 1 The liquid refrigerant delivered to the evaporator 38 can absorb heat from a conditioning fluid that is then directed to the load 62 (e.g., the building 12). That is, the conditioning fluid can be cooled by the refrigerant in the evaporator 38 and then can be used in the building 12 to condition an air stream provided for conditioning a space in the building 12. The liquid refrigerant in the evaporator 38 can undergo a phase change from liquid refrigerant to refrigerant vapor. As Figure 3 As shown in the illustrative embodiment, the evaporator 38 can include a tube bundle 58 having a supply line 60S and a return line 60R connected to the cooling load 62. Cooling fluid (e.g., water, glycol, calcium chloride brine, sodium chloride brine, or any other suitable fluid) of the evaporator 38 enters the evaporator 38 via the return line 60R and exits the evaporator 38 via the supply line 60S. The evaporator 38 can reduce the temperature of the cooling fluid in the tube bundle 58 via heat transfer with the refrigerant. 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 refrigerant exits the evaporator 38 and is returned to the compressor 32 through the suction line to complete the cycle.

[0037] As previously described, under certain conditions (such as low ambient temperature conditions), the vapor compression system 14 can operate in a natural cooling mode. For example, the vapor compression system 14 can be able to provide sufficient cooling capacity without powering the compressor 32 (or, in other words, the motor 50 and / or the VSD 52 of the compressor 32) when the ambient temperature is below a temperature threshold, when the cooling fluid associated with the cooling tower 56 is below a temperature threshold, or when the refrigerant circulating through the vapor compression system 14 is below a temperature threshold. According to the present embodiment, the compressor 32 can include a centrifugal compressor having a floating rotor. The rotor can be floated via one or more magnetic bearings, or in an oil-free system, via one or more rolling element bearings. Further, a variable geometry diffuser (VGD), a pre-rotation vane (PRV), and / or an expansion device 36 of the compressor 32 can be set to a fully open position in response to an initiation of the natural cooling mode. The floating rotor, the open VGD, the open PRV, and / or the open expansion device 36 can allow the impeller of the compressor 32 (despite not being powered) to freely rotate in response to receiving refrigerant during the natural cooling mode. In some embodiments, the expansion valve 36 can be throttled during the natural cooling mode in order to maintain a condenser level, to increase available liquid head, and to reduce submergence losses in the evaporator 38. The condenser level can be monitored by a sensor 121 ( Figure 6 ) detects, and the controller 40 can operate the throttling of the expansion device 36, 66 based on the liquid level in the condenser 34.

[0038] By enabling the refrigerant to pass through the compressor 32 during the natural cooling mode and enabling the rotor of the compressor 32 to freewheel in response to receiving refrigerant during the natural cooling mode, the number of parts, complexity, and / or cost of the vapor compression system 14 (e.g., chiller) can be reduced compared to conventional embodiments having a compressor bypass feature. For example, a compressor bypass valve or circuit included in conventional systems can be omitted. Further, the number of parts, complexity, and / or cost of the vapor compression system 14 can be reduced without causing significant pressure loss in the compressor 32 during the natural cooling mode.

[0039] Figure 4 is a schematic illustration of an embodiment of a vapor compression system 14 having an intermediate circuit 64 incorporated between the condenser 34 and the expansion device 36. The intermediate circuit 64 can have an inlet line 68 fluidly connected directly to the condenser 34. In other embodiments, the inlet line 68 can be fluidly coupled indirectly to the condenser 34. As Figure 4 As shown in the illustrative embodiment of FIG. 1, the inlet line 68 includes a first expansion device 66 positioned upstream of an intermediate vessel 70. In some embodiments, the intermediate vessel 70 can be a flash tank (e.g., a flash intercooler). In other embodiments, the intermediate vessel 70 can be configured as a "heat exchanger" or "surface economizer." In Figure 4 In the illustrative embodiment of FIG. 1, the intermediate vessel 70 functions as a flash tank, and the first expansion device 66 is configured to reduce the pressure (e.g., expand) of the liquid refrigerant received from the condenser 34. During the expansion process, a portion of the liquid refrigerant can vaporize, and thus the intermediate vessel 70 can function to separate the vapor refrigerant from the liquid refrigerant received from the first expansion device 66. Additionally, due to the pressure drop experienced by the liquid refrigerant as it enters the intermediate vessel 70 (e.g., due to the rapid increase in volume experienced as it enters the intermediate vessel 70), the intermediate vessel 70 can provide further expansion of the liquid refrigerant. The vapor refrigerant in the intermediate vessel 70 can be drawn by the compressor 32 through a suction line 74 of the compressor 32. In other embodiments, the vapor refrigerant in the intermediate vessel 70 can be drawn to an intermediate stage (e.g., not the suction stage) of the compressor 32. Due to the expansion of the refrigerant at the expansion device 66 and / or in the intermediate vessel 70, the liquid refrigerant collected in the intermediate vessel 70 can have a lower enthalpy than the liquid refrigerant exiting the condenser 34. The liquid refrigerant from the intermediate vessel 70 can then flow through the line 72 and through the second expansion device 36 to the evaporator 38.

[0040] Figure 4The vapor compression system 14 of FIG. 1 can operate in a normal mode of operation whereby the compressor 32 is powered (e.g., by powering the motor 50, the VSD 52, and the control panel 40 that controls the motor 50 and / or the VSD 52) to increase the pressure and temperature of the refrigerant received by the compressor 32 from the evaporator 38 and / or the intermediate vessel 70. As described with respect to the vapor compression system 14 of FIG. 2, Figure 3 the vapor compression system 14 of FIG. 3, Figure 4 the vapor compression system 14 of FIG. 4 can also operate in a natural cooling mode in accordance with the present disclosure whereby the compressor 32 is not powered but still enables the flow of refrigerant therethrough. As described in detail below with respect to the vapor compression system 14 of FIG. 5, Figure 5 the compressor 32 (e.g., the impeller of the compressor 32) can be configured to freely rotate in response to receiving refrigerant during the natural cooling mode.

[0041] Figure 5 is Figure 2 a schematic view of an embodiment of a portion of the vapor compression system 14 of FIG. 1, showing a cross-section of a portion of the control panel 40 (e.g., the controller) and the compressor 32. The exemplified compressor 32 is a centrifugal compressor suitable for operation in the disclosed natural cooling mode, although other types of compressors can be used with the present technology.

[0042] The compressor 32 can operate in a normal operating mode whereby the control panel 40 powers the compressor 32 (e.g., via the motor 50 and / or VSD corresponding to the compressor 32) as the compressor 32 receives refrigerant at the suction side 80 (e.g., inlet) of the compressor 32. In the normal operating mode, the compressor 32 operates to increase the pressure and temperature of the refrigerant before delivering the refrigerant to, for example, the condenser 34 of the vapor compression system 14. For example, the motor 50 can rotate a shaft 82 of the compressor 32. The shaft 82 can be coupled to an impeller 84 having vanes or blades 86. The shaft 82 and impeller 84, as well as other features that are driven to rotate by the motor 50 via the shaft 82, can be collectively referred to as a rotor 85 of the compressor 32. As the compressor 32 receives refrigerant and the rotor 85 is driven to rotate by the motor 50 during the normal operating mode, the rotating blades 86 of the impeller 84 can progressively increase the energy of the refrigerant, which is transferred toward a diffuser 88 of the compressor 32. The diffuser 88 converts the kinetic energy of the refrigerant into pressure by reducing the velocity of the refrigerant. For example, the illustrated diffuser 88 is a variable geometry diffuser (VGD) having a diffuser ring 90 that can be controlled via the control panel 40 to open or restrict the flow path of the refrigerant through the diffuser 88 to varying degrees based on desired operating parameters and / or performance of the compressor 32. The illustrated compressor 32 also includes pre-rotation vanes 92 disposed upstream of the impeller 84 relative to a flow 94 of refrigerant through the compressor 32. After passing through or across the pre-rotation vanes 92, the impeller 84, and the diffuser 88, the pressurized refrigerant can accumulate in a collector 96 for subsequent distribution of the pressurized refrigerant to downstream components of the vapor compression system, such as Figures 2 to 4 the condenser 34 in the vapor compression system 14.

[0043] As previously described, and in accordance with the present disclosure, the vapor compression system 14 can operate in a natural cooling mode whereby the compressor 32 receives refrigerant but is not powered (e.g., driven to rotate). When the vapor compression system 14 operates in the natural cooling mode, the compressor 32 (e.g., the impeller 84) is configured to freely rotate in response to receiving refrigerant. For example, the illustrated compressor 32 includes bearings that can be magnetic bearings or rolling element bearings in an oil-free system. When the compressor 32 (e.g., the motor 50 and / or corresponding VSD 52 of the compressor 32) is not powered by the control panel 40, by including magnetic bearings or rolling element bearings in an oil-free system, the rotor 85 can be levitated and able to freely rotate in response to receiving refrigerant. Further, when the control panel 40 initiates or operates the natural cooling mode, the control panel 40 can adjust the pre-rotation vanes 92 and the variable geometry diffuser 88 to an open position (e.g., a fully open position), thereby reducing or eliminating pressure losses in the refrigerant during operation of the vapor compression system 14 in the natural cooling mode.

[0044] Figure 6 is Figure 2 a schematic view of an embodiment of a vapor compression system 14. In the illustrated embodiment, the vapor compression system 14 includes features similar to those presented in Figure 4 but without the intermediate vessel. However, Figure 6 the vapor compression system 14 in also includes a liquid pump 116 disposed between the condenser 34 and the evaporator 38, and a hot gas bypass valve 114 (HGBV). Further, Figure 6 the evaporator 38 in is a falling film evaporator, and the vapor compression system 14 (i.e., chiller) can include a bypass valve 110 operable to direct refrigerant to various portions of the evaporator 38 (e.g., falling film evaporator) depending on operating conditions.

[0045] As previously described, refrigerant can be directed to the evaporator 38 (e.g., falling film evaporator) and can be used to cool a conditioned fluid directed to and from the load 62. The load 62 can be, for example, one or more air handling units (AHU) that utilize the cooled conditioned fluid to cool an air stream provided to a conditioned space. Generally, the evaporator 38 (e.g., falling film evaporator) can be configured to receive refrigerant toward a top of the evaporator 38 (e.g., at the upper inlet 101) such that the refrigerant is gravity fed from the upper inlet 101 downward and through the evaporator 38. During certain conditions, the pressure of the refrigerant can be such that the refrigerant cannot be moved to the top of the evaporator 38, or such that if the refrigerant is moved to the top of the evaporator 38 to operate the evaporator 38 as a falling film evaporator, the system 14 would otherwise suffer (e.g., pressure loss, cooling capacity, etc.). During these conditions, the falling film bypass valve 110 can be operated (e.g., opened) to enable the refrigerant to travel toward a bottom of the evaporator 38, e.g., into the lower inlet 103. For example, the control panel 40 can instruct (e.g., via a wired connection or via a wireless connection over the network 115) to open and / or close the falling film bypass valve 110, e.g., based on a refrigerant pressure detected by a sensor 123 communicatively coupled to the control panel 40. Thus, when the falling film bypass valve 110 is actuated to divert refrigerant from the upper inlet 101 to the lower inlet 103, the evaporator 38 can be operated as a flooded evaporator. It should be noted that in another embodiment, the falling film bypass valve 110 can be positioned differently than shown, and can be closed to divert refrigerant from the upper inlet 101 to the lower inlet 103 of the evaporator 38.

[0046] As previously described, the vapor compression system 14 can also include the HGBV 114. The HGBV 114 can be operated (e.g., opened) to enable vapor refrigerant to pass from the evaporator 38 toward and to the condenser 34. Opening the HGBV 114 to enable vapor refrigerant to pass to the condenser 34 can increase the cumulative refrigerant flow path area or size of the vapor compression system 14 and increase the cooling capacity of the vapor compression system 14. In some embodiments, the HGBV 114 can be opened in response to initiation of the free cooling operation.

[0047] Further, in certain embodiments, the vapor compression system 14 can include a liquid pump 116 that can be operated (e.g., powered) during the free cooling operation to move liquid refrigerant from the condenser 34 to the evaporator 38. The pump 116 can eliminate the need for the falling film bypass valve 110 and the lower inlet 103 and associated piping. However, in certain embodiments, the vapor compression system 14 can be operated as a thermosyphon whereby natural convection causes heated liquid refrigerant to move upward within the vapor compression system 14 as it is replaced by cooler liquid refrigerant flowing downward via gravity.

[0048] In embodiments without the pump 116, it can be preferable to include the falling film bypass valve 110 and corresponding features. The falling film bypass valve 110 can be needed for the free cooling operation if the condenser 34 is physically lower than the upper inlet 101 such that gravity cannot provide sufficient liquid refrigerant flow.

[0049] Other features can be incorporated with and / or used in conjunction with the vapor compression system 14 (and corresponding natural cooling operation) described herein. For example, the capacity of the vapor compression system 14 can be modulated based on feedback regarding the temperature of the conditioned fluid. More specifically, the control panel 40 can monitor the temperature of the conditioned fluid exiting the evaporator 38. A sensor 120 can detect the temperature of the conditioned fluid exiting the evaporator 38 and can be communicatively coupled to the control panel 40, which periodically receives the temperature data and modulates the capacity of the vapor compression system 14 based on the detected temperature. It should be noted that the sensor 120 or a separate sensor can also be used to determine when to initiate the natural cooling operation. For example, the natural cooling operation can be initiated during cooler seasons (e.g., fall, winter, and / or spring) based on the sensor detecting an ambient temperature and / or based on the sensor detecting a cooling fluid temperature. As previously described, the vapor compression system 14 can be able to operate during relatively cooler seasons at a capacity suitable to meet cooling demands without powering and driving rotation of the compressor 32. The control panel 40 can include temperature thresholds stored in the memory 46. The temperature thresholds can relate to the temperature of the conditioned fluid exiting the evaporator 38 (e.g., as detected by the sensor 120), the ambient air temperature, the temperature of the cooling fluid directed to and from the cooling tower 56, the refrigerant temperature (e.g., detected at selected locations along the vapor compression system 14), or combinations thereof. When the detected temperature corresponding to a temperature threshold is below the temperature threshold, the control panel 40 can initiate the natural cooling operation.

[0050] In addition to these features, under certain conditions, the motor 50 can be operated as a generator during the natural cooling mode. For example, while the control panel 40 can terminate the supply of power to the motor 50 (or the VSD 52, which can be considered part of the motor 50 and / or the compressor 32) during the natural cooling mode, the kinetic energy of the freely rotating compressor 32 (e.g., produced by the passive refrigerant flow directed therethrough) during the natural cooling mode can be harnessed and used to generate energy via the motor 50 or a separate generator coupled to the rotor 85 of the compressor 32. Thus, the motor 50 can be coupled to a load 122 via the VSD 52 (e.g., an electrical system, a battery, a capacitor, a utility grid, etc.), and the load 122 can harness or store the electrical energy generated in or by the motor 50 during the natural cooling mode.

[0051] Furthermore, as previously described, the expansion device 36 (or some other expansion device of system 14) can be throttled during natural cooling operation to maintain the condenser level, thereby increasing the available liquid head and reducing immersion losses in the evaporator 38. The condenser level can be detected via a sensor 121 coupled to the controller 40 via wired or wireless communication, and the controller 40 can operate the throttling of the expansion device 36 based on the level in the condenser 34.

[0052] Figure 7 This shows the operation. Figure 2 A flowchart of an embodiment of method 200 for vapor compression system 14. Method 200 includes: operating vapor compression system 14 in normal operating mode (block 202), whereby compressor 32 (or its motor 50 or VSD 52) is powered, receiving refrigerant, and increasing the temperature and pressure of the refrigerant before delivering it to condenser 34.

[0053] The method 200 also includes detecting the actual temperature of the fluid associated with the vapor compression system 14. As previously described, the fluid may be ambient air (e.g., a fluid used by the cooling tower 56 to cool the refrigerant subsequently extracting heat from the condenser 34), fluid transferred between the cooling tower 56 and the condenser 34, fluid transferred between the evaporator 38 and the load 62 (e.g., an air handling unit), or refrigerant. As will be described below, the detected actual temperature of the fluid can be used to determine whether operation in a natural cooling mode is required. However, in some embodiments, the vapor compression system 14 may be manually operated to initiate a natural cooling mode.

[0054] The illustrated method 200 also includes comparing the actual temperature discussed above with respect to box 204 with a threshold temperature (box 206). For example, as shown, method 200 includes determining (box 208) whether the actual temperature is less than a threshold temperature. If the actual temperature is not lower than the threshold temperature (box 210), normal operation of the vapor compression system 14 can continue. If the actual temperature is lower than the threshold temperature (box 212), a natural cooling mode is activated (box 214).

[0055] As previously described, in natural cooling mode, power to compressor 32 (e.g., to motor 50 or VSD 52 of compressor 32) is terminated. However, compressor 32 is still configured to receive and direct the refrigerant flow therethrough. In other words, the refrigerant flow does not bypass compressor 32 in natural cooling mode. Compressor 32 is configured to rotate freely during natural cooling mode (e.g., in response to receiving refrigerant). To improve efficiency during natural cooling mode, compressor 32 may include features capable of reducing pressure losses that would otherwise be caused by compressor 32 during the currently disclosed natural cooling mode. For example, the VGD (e.g., diffuser 88) of compressor 32 may be set to an open (e.g., fully open) position, the PRV 92 of compressor 32 may be set to an open (e.g., fully open) position, the expansion valve (e.g., valve 36) of vapor compression system 14 may be set to an open (e.g., fully open) position, or any combination thereof. However, in some embodiments, the expansion valve 36 can be throttled during natural cooling mode to maintain the condenser level, thereby increasing the available liquid head and reducing immersion losses in the evaporator 38. Furthermore, in some embodiments, a falling film bypass valve 110 may be included and operated to transfer refrigerant from the upper inlet 101 to the lower inlet 103 in response to specific operating conditions. Figure 6 As described in detail. Furthermore, HGBV 114 may be included and operated to enable vaporized refrigerant to be transferred from evaporator 38 to condenser 34 during natural cooling mode. Finally, motor 50 may be operated as a generator in natural cooling mode to convert the kinetic energy of the freely rotating compressor 32 into electrical energy.

[0056] While only certain features of this embodiment have been shown and described herein, many modifications and alterations will occur to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and alterations falling within the true spirit of this disclosure. Furthermore, it should be understood that certain elements of the disclosed embodiments can be combined or interchanged with each other.

[0057] The technical references presented and asserted herein are applied to tangible objects and specific examples of practical nature that demonstrate improvements to the technical field of the invention and are therefore not abstract, intangible, or purely theoretical. Furthermore, if any claim appended to this specification contains one or more elements expressed as "means for [performing] [function]..." or "steps for [performing] [function]...", such elements are intended to be interpreted in accordance with 35U.SC112(f). However, for any claim containing elements specified in any other manner, it is intended that such elements not be interpreted in accordance with 35U.SC112(f).

Claims

1. A heating, ventilation, air conditioning and / or cooling (HVAC&R) system, comprising: A vapor compression system, comprising an evaporator, a condenser, and a compressor, wherein the compressor is configured to guide refrigerant through the vapor compression system in a normal operating mode, and wherein the rotor of the compressor is configured to suspend in a natural cooling mode of the vapor compression system to guide the refrigerant through the compressor; and A controller configured to supply power to the motor of the compressor in the normal operating mode and to suspend the power supply to the motor of the compressor in the natural cooling mode.

2. The HVAC&R system of claim 1, wherein the compressor includes a suspended rotor.

3. The HVAC&R system of claim 2, wherein the compressor includes a magnetic bearing, and the suspended rotor is suspended via the magnetic bearing.

4. The HVAC&R system of claim 3, wherein the controller is configured to provide additional power to the magnetic bearing in the natural cooling mode.

5. The HVAC&R system of claim 2, wherein the compressor includes a rolling element bearing, and the suspended rotor is suspended via the rolling element bearing.

6. The HVAC&R system of claim 1, wherein the compressor comprises: A variable geometry diffuser (VGD), and the controller is configured to indicate the VGD to a fully open position in response to the activation of the natural cooling mode; or The controller is configured to indicate the PRV to the fully open position in response to the activation of the natural cooling mode.

7. The HVAC&R system of claim 1, wherein the compressor includes a variable speed drive (VSD) configured to supply power to the motor, and the controller is configured to: control the VSD to provide the power supply to the motor in the normal operating mode, and control the VSD to suspend the power supply to the motor in the natural cooling mode.

8. The HVAC&R system of claim 1, comprising a temperature sensor configured to detect the temperature of: the refrigerant, a conditioning fluid directed through the evaporator, a cooling fluid directed through the condenser, or ambient air, wherein the controller is configured to receive data indicating the temperature from the temperature sensor, and wherein the controller is configured to activate the natural cooling mode in response to determining that the temperature is less than a threshold temperature value.

9. The HVAC&R system of claim 1, comprising a refrigerant pump, wherein the controller is configured to activate the refrigerant pump in response to the activation of the natural cooling mode, such that the refrigerant pump forces at least the liquid phase of the refrigerant through the vapor compression system.

10. The HVAC&R system of claim 1, wherein the motor is configured to convert the kinetic energy of the compressor rotor into electrical energy during the natural cooling mode.

11. The HVAC&R system of claim 1, wherein the compressor is configured to receive a vapor portion of the refrigerant from the evaporator in both the normal operating mode and the natural cooling mode.

12. A method of operating a heating, ventilation, air conditioning and / or cooling (HVAC&R) system, comprising: In response to the normal operating mode of the HVAC&R system, power is supplied to the motor of the compressor of the vapor compression system, such that the compressor is driven by the motor and the refrigerant circulates between the evaporator and the condenser of the vapor compression system; as well as In response to the natural cooling mode of the HVAC&R system, power is cut off to the motor of the compressor in the vapor compression system, causing the compressor rotor to suspend and allowing the refrigerant to pass through the compressor.

13. The method of claim 12, comprising: The rotor of the compressor is suspended by a magnetic bearing.

14. The method of claim 13, comprising: Additional power is supplied to the magnetic bearing in response to the natural cooling mode.

15. The method of claim 12, comprising: The rotor of the compressor is suspended via a rolling element bearing.

16. The method of claim 12, comprising: The kinetic energy of the compressor rotor is converted into electrical energy.

17. The method of claim 12, comprising receiving a portion of the refrigerant vapor from the evaporator via the compressor in both the normal operating mode and the natural cooling mode.

18. A cooler system, comprising: A compressor configured to circulate refrigerant through a refrigerant circuit, wherein the rotor of the compressor is configured to suspend in the natural cooling mode of the cooler system to guide the refrigerant through the compressor; The motor of the compressor; as well as A controller configured to: enable power supply to the motor of the compressor in response to the normal operating mode of the cooler system, and disable power supply to the motor of the compressor in response to the natural cooling mode of the cooler system.

19. The cooler system of claim 18, wherein the compressor comprises a rotor suspended by a magnetic bearing or a rolling element bearing.

20. The cooler system of claim 18, comprising: The evaporator of the refrigerant circuit, the evaporator being configured to receive the refrigerant; as well as The condenser of the refrigerant circuit is configured to receive the refrigerant.

21. The cooler system of claim 20, comprising a temperature sensor configured to detect the temperature of: the refrigerant, a regulating fluid directed through the evaporator, a cooling fluid directed through the condenser, or ambient air, wherein the controller is configured to receive data indicating the temperature from the temperature sensor, and wherein the controller is configured to activate the natural cooling mode in response to determining that the temperature is less than a threshold temperature value.

22. The cooler system of claim 18, wherein the motor is configured to convert the kinetic energy of the compressor rotor into electrical energy during the natural cooling mode.

23. The cooler system of claim 18, wherein the compressor includes an impeller and the compressor is configured to guide the refrigerant through the impeller in the normal operating mode and the natural cooling mode, and wherein the compressor is configured to receive a vapor portion of the refrigerant corresponding to the refrigerant circuit from the evaporator during the normal operating mode and the natural cooling mode.

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