Cooling system for centrifugal compressor and refrigeration system including same

Abstract

A cooling system for a compressor includes a coolant supply line, a coolant return line, a temperature sensor connected to the coolant return line to detect at least one of a temperature of the coolant return line and a coolant temperature in the coolant return line, and a controller. The coolant supply line includes a coolant control valve and is connectable to a housing of the compressor to supply coolant to at least one of a plurality of coolant flow paths defined therein. The coolant return line is connectable to the compressor housing to receive coolant from the coolant flow paths and return the coolant to a low pressure side of the compressor. The controller is configured to control the coolant control valve based on the temperature detected by the temperature sensor to control the supply of coolant through the coolant supply line.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent Application No. 17 / 248,166, filed January 12, 2021, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The field relates generally to centrifugal compressors, and more specifically to cooling and refrigeration systems used with centrifugal compressors. [Background technology]

[0003] Although centrifugal compressors offer several advantages over positive displacement compressor designs such as reciprocating, rotary, scroll, and screw compressors, the incorporation of centrifugal compressors into low capacity cooling systems has been limited due to the high rotational speed of the centrifugal compressor impeller and the associated challenges of providing a suitable operating environment for the impeller and associated motor. One particular challenge is providing sufficient cooling to the motor and bearings associated with the compressor drive shaft to maintain the motor and bearings within a suitable operating temperature range.

[0004] This Background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to better understand 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. Summary of the Invention

[0005] In one aspect, a compressor system includes a centrifugal compressor and a cooling circuit. The compressor includes a housing, a shaft rotatably supported within the housing by at least one bearing, an impeller connected to the shaft, and a motor operatively connected to the shaft. The housing has a plurality of coolant flow paths defined therein that supply coolant to the bearings and the motor. The cooling circuit includes a coolant supply line connected to the compressor housing to supply coolant to at least one of the plurality of coolant flow paths. The coolant supply line includes a coolant control valve for controlling coolant flow through the coolant supply line. The cooling circuit also includes a coolant return line connected to the compressor housing to receive coolant from the plurality of coolant flow paths and return the coolant to a low pressure side of the compressor, a temperature sensor connected to the coolant return line to detect at least one of a temperature of the coolant return line and a temperature of the coolant in the coolant return line, and a controller connected to the temperature sensor and the coolant control valve. The controller is configured to control the coolant control valve based on the temperature detected by the temperature sensor to control the supply of coolant to the compressor housing.

[0006] In another aspect, a cooling system for a compressor includes a coolant supply line, a coolant return line, a temperature sensor connected to the coolant return line for detecting at least one of a temperature of the coolant return line and a temperature of a coolant in the coolant return line, and a controller. The coolant supply line includes a coolant control valve for controlling a flow of coolant therethrough and is connectable to a housing of the compressor to supply coolant to at least one of a plurality of coolant flow paths defined within the compressor housing. The coolant return line is connectable to the compressor housing to receive coolant from the plurality of coolant flow paths and return the coolant to a low pressure side of the compressor. The controller is connected to the temperature sensor and the coolant control valve and configured to control the coolant control valve based on the temperature detected by the temperature sensor to control the supply of coolant through the coolant supply line.

[0007] In yet another aspect, a refrigeration system includes a compressor, an evaporator, a condenser, an expansion device, and a cooling circuit. The compressor includes a housing, a shaft rotatably supported within the housing by at least one bearing, an impeller connected to the shaft, and a motor operatively connected to the shaft. The housing has a plurality of coolant flow paths defined therein that supply coolant to the at least one bearing and the motor. The cooling circuit includes a coolant supply line connected to the compressor housing to supply coolant to at least one of the plurality of coolant flow paths, a coolant return line connected to the compressor housing to receive coolant from the plurality of coolant flow paths and return the coolant to a low pressure side of the compressor, a temperature sensor connected to the coolant return line to detect at least one of a temperature of the coolant return line and a temperature of the coolant in the coolant return line, and a controller. The coolant supply line includes a coolant control valve for controlling coolant flow through the coolant supply line. The controller is connected to the temperature sensor and the coolant control valve and configured to control the coolant control valve based on the temperature detected by the temperature sensor to control the supply of coolant to the compressor housing.

[0008] Various refinements exist in the features noted in relation to the above aspects. Further features may be incorporated into the above aspects. These refinements and additional features may exist individually or in any combination. For example, various features described below in relation to any of the illustrated embodiments may be incorporated into any of the above aspects alone or in any combination. [Brief description of the drawings]

[0009] The following figures illustrate various aspects of the present disclosure.

[0010] [Figure 1] FIG. 1 is a schematic diagram of an exemplary refrigeration system.

[0011] [Diagram 2] FIG. 2 is a schematic diagram of an exemplary compressor cooling system suitable for use in the refrigeration system of FIG.

[0012] [Diagram 3] FIG. 3 is a cross-sectional view of a portion of the compressor cooling system shown in FIG. 2, showing a temperature sensor connected in the coolant return line.

[0013] [Figure 4] 3 is a graph illustrating operation of the refrigerant control valve of the compressor cooling system shown in FIG. 2 based on two temperature set points.

[0014] [Diagram 5] FIG. 2 is a schematic diagram of another exemplary compressor cooling system suitable for use in the refrigeration system 100 of FIG.

[0015] [Figure 6] 6 is a graph illustrating operation of a refrigerant control valve of the compressor cooling system shown in FIG. 5 according to an exemplary control scheme.

[0016] [Figure 7] FIG. 13 is a perspective view of an assembled compressor suitable for use in the refrigeration system of FIG. 1 and the compressor cooling systems of FIGS. 2 and 5.

[0017] [Figure 8] FIG. 8 is a cross-sectional view of the compressor of FIG. 7 taken along line 8-8.

[0018] Corresponding reference characters indicate corresponding parts throughout the drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] FIG. 1 is a schematic diagram of an example of a refrigeration system 100. The refrigeration system 100 includes a centrifugal compressor 102, a condenser 104, an expansion device 106 (e.g., expansion valve, orifice, capillary tube), and an evaporator 108. The refrigeration system 100 may include additional or other components than those shown and described with reference to FIG. 1 without departing from the scope of this disclosure. In operation, the compressor 102 receives a working fluid, such as a refrigerant, as a low-pressure gas via a suction line 110. The compressor 102 compresses the gas, thereby increasing the temperature and pressure of the gas. The pressurized hot gas then flows to the condenser 104, where the high-pressure gas is condensed into a high-pressure liquid. The liquid then flows through the expansion device 106, which reduces the pressure of the liquid. The reduced pressure fluid, which may be a gas or a mixture of gas and liquid after passing through the expansion device 106, then passes through the evaporator 108. The evaporator 108 may include a heat exchanger in which the fluid circulating therethrough is cooled by the reduced pressure refrigerant fluid as the refrigerant fluid evaporates into a gas within the evaporator 108. The refrigerant gas is then returned via suction line 110 to the compressor 102 where it again compresses the working fluid and the process repeats.

[0020] The exemplary refrigeration system 100 includes a compressor cooling system 112 that draws working fluid from a portion of the refrigerant circuit (in this example, downstream of the condenser 104) and directs it to the compressor 102 for cooling the compressor 102's components, such as the compressor's 102 motor and bearings. The working fluid used in the cooling system 112 is referred to as the "refrigerant" and is returned to the refrigeration circuit by a refrigerant return line 114 that has an outlet connected to the low pressure side of the compressor 102 (e.g., the suction line 110). As described further herein, a pressure differential across the refrigeration circuit of the cooling system 112 drives the refrigerant through the compressor 102 and back into the refrigeration circuit.

[0021] Figure 2 is a schematic diagram of an example compressor cooling system 200 suitable for use in the refrigeration system 100 of Figure 1. The compressor cooling system 200 includes a compressor 202 (e.g., compressor 102) and a cooling circuit 204 configured to supply coolant to components of the compressor 202 to facilitate cooling the compressor 202 and maintaining the components of the compressor 202 within suitable operating temperature ranges.

[0022] The compressor 202 in the illustrated embodiment is a two-stage centrifugal compressor 202 including a first stage 206 and a second stage 208. In other embodiments, the compressor 202 may include a single stage or may include more than two stages. In still other embodiments, the compressor 202 may be a compressor other than a centrifugal compressor. The first stage 206 includes a first stage inlet 210 connected in flow communication with an evaporator (e.g., evaporator 108 shown in FIG. 1) by a suction line 212. The second stage 208 includes a second stage inlet 214 connected in flow communication with a first stage outlet of the first stage 206 by a refrigerant transfer conduit (not shown in FIG. 2) that receives compressed refrigerant from the first stage 206.

[0023] Compressor 202 generally includes a housing 216, a shaft 218 rotatably supported within housing 216 by a number of bearings 220, 222, 224, a first stage impeller 226 connected to a first end 228 of shaft 218, a second stage impeller 230 connected to a second end 232 of shaft 218, and a motor 234 operably connected to shaft 218 to drive rotation thereof. Compressor 202 may include components in addition to those shown in FIG. 2.

[0024] The housing 216 encloses the components of the compressor 202 within one or more sealed (e.g., hermetic or semi-hermetic) cavities. In some embodiments, for example, the housing 216 includes the end caps of each stage of the compressor 202 that define a volute in which the first and second stage impellers 226, 230 are disposed. In some embodiments, the housing 216 is formed from multiple cast pieces assembled using appropriate fasteners (e.g., screws, bolts, etc.).

[0025] The bearings 220, 222, 224 rotatably support the shaft 218 within the housing 216. In the illustrated embodiment, the compressor 202 includes a first radial bearing 220, a second radial bearing 222, and a thrust bearing 224. In other embodiments, the compressor 202 may include additional or fewer bearings. The bearings 220, 222, 224 may include, for example, but are not limited to, roller-type bearings, magnetic bearings, fluid film bearings, airfoil bearings, and combinations thereof. They may include any suitable type of bearing that enables the compressor 202 to function as described herein. In the illustrated embodiment, each of the bearings 220, 222, 224 includes an airfoil-type bearing.

[0026] Motor 234 is operatively connected to shaft 218 to drive rotation thereof during operation of compressor 202. Motor 234 may generally include any suitable motor that enables compressor 202 to function as described herein. In the illustrated embodiment, motor 234 is an electric motor and includes suitable components (e.g., a stator and a rotor) for imparting rotational motion to shaft 218 during operation of compressor 202.

[0027] The housing 216 has a plurality of coolant passages 236, 238, 240, 242 defined therein that supply coolant to the plurality of bearings 220, 222, 224 and the motor 234. The plurality of coolant passages 236, 238, 240, 242 may be arranged and / or defined within the compressor housing 216 in any manner that enables the compressor cooling system 200 to function as described herein. For example, the coolant passages 236, 238, 240, 242 may be formed as passages within a component of the compressor housing 216 (e.g., a cast part, such as by machining), as passages defined between two or more components of the compressor 202 (e.g., between the motor 234 and the compressor housing 216), and combinations thereof.

[0028] The exemplary compressor 202 includes a first coolant passage 236, a second coolant passage 238, a third coolant passage 240, and a fourth coolant passage 242. The first coolant passage 236 supplies coolant to the thrust bearing 224, the second coolant passage 238 supplies coolant to the first radial bearing 220, the third coolant passage 240 supplies coolant to the second radial bearing 222, and the fourth coolant passage 242 supplies coolant to the motor 234. In some embodiments, the coolant passages 236, 238, 240, 242 may share common or overlapping portions. In the illustrated embodiment, for example, the first coolant passage 236 overlaps with and feeds into the second coolant passage 238 at the first radial bearing 220, and the third coolant passage 240 overlaps with and feeds into the fourth coolant passage 242 at the motor 234.

[0029] Each of the coolant flow paths 236, 238, 240, 242 has a corresponding coolant inlet port 244 that connects to the cooling circuit 204 in the illustrated embodiment. That is, the compressor housing 216 includes four external inlet connections for connecting the multiple coolant flow paths 236, 238, 240, 242 to the cooling circuit 204. In other embodiments, the compressor housing 216 may have fewer external inlet connections. For example, two or more of the coolant flow paths 236, 238, 240, 242 may share a common single coolant inlet port (and a common connection point to the cooling circuit 204) that supplies coolant to the multiple coolant flow paths 236, 238, 240, 242. In such embodiments, the coolant flow delivered to the common coolant inlet port may be separated, split, or otherwise routed within the compressor housing 216 to deliver coolant to two or more of the coolant flow paths 236, 238, 240, 242. In some embodiments, for example, the bearing coolant flow paths (i.e., the first, second and third coolant flow paths 236, 238, 240) may have a common coolant inlet port, and the coolant flow may be routed to separate flow paths internally within the compressor housing 216.

[0030] The compressor housing 216 also defines a common coolant outlet port 246 in the illustrated embodiment. The common coolant outlet port 246 receives coolant from each of the plurality of coolant flow paths 236, 238, 240, 242. That is, all of the coolant delivered to the compressor housing 216 and the coolant flow paths 236, 238, 240, 242 is returned to the common coolant outlet port 246. In some embodiments, at least one of the plurality of coolant flow paths 236, 238, 240 is arranged such that the coolant flows through the at least one coolant flow path, in turn, across the at least one bearing 220, 222, 224, through the motor 234, and into the common coolant outlet port 246. In this manner, the coolant flowing through the at least one coolant flow path absorbs heat from both the motor 234 and one of the bearings 220, 222, 224. The coolant may flow through the motor 234, for example, by flowing between a stator and rotor of the motor 234, through the portion of the shaft 218 around which the motor 234 is disposed, and / or through passages or holes defined in the rotor of the motor 234.

[0031] The cooling circuit 204 supplies coolant to the compressor housing 216 (specifically to a number of coolant flow paths 236, 238, 240, 242) and returns coolant to a refrigeration circuit (e.g., refrigeration system 100 shown in FIG. 1) of which the compressor 202 is a part. The illustrated cooling circuit 204 includes a number of coolant supply lines 248, 250, 252, 254, a coolant return line 256, a temperature sensor 258, and a controller 260.

[0032] The coolant supply lines 248, 250, 252, 254 are connected in flow communication with a coolant source 262 and are connected to the compressor housing 216 to supply coolant to the multiple coolant flow paths 236, 238, 240, 242. The coolant supply lines 248, 250, 252, 254 may include any suitable fluid conduits (rigid and / or flexible) that enable the supply of coolant to the compressor housing 216, including, for example, but not limited to, pipes, hoses, tubes, and combinations thereof. In some embodiments, the coolant supply lines 248, 250, 252, 254 are constructed of metal tubing, such as copper tubing. The illustrated cooling circuit 204 includes four coolant supply lines 248, 250, 252, 254, one for each of the coolant flow paths 236, 238, 240, 242 defined in the compressor housing 216. More specifically, the illustrated embodiment includes a plurality of bearing coolant supply lines 248, 250, 252 and a motor coolant supply line 254. Each of the bearing coolant supply lines 248, 250, 252 is connected to one of the first, second, and third coolant flow paths 236, 238, 240 to flow or supply coolant to at least one of the compressor bearings 220, 222, 224. The motor coolant supply line 254 is connected to the fourth coolant flow path 242 to supply coolant to the motor 234.

[0033] An exemplary coolant source 262 is a coolant drawn from the refrigeration circuit of which the compressor 202 is a part, specifically, the refrigeration circuit downstream of the condenser (e.g., condenser 104 shown in FIG. 1 ), such as between the condenser and the expansion device of the refrigeration system. The coolant is the same working fluid (e.g., refrigerant) used in the example refrigeration system. In other embodiments, the coolant source 262 may be a part of the refrigeration system other than downstream of the condenser, such as a condenser, or may be any other suitable coolant source that enables the compressor cooling system 200 to function as described herein. In yet other embodiments, the coolant source 262 may be an auxiliary liquid cycle.

[0034] As described further herein, coolant is drawn through cooling circuit 204 from coolant source 262 using a pressure differential between the coolant source 262 and the outlet end of return line 256. In other embodiments, coolant may be directed through cooling circuit 204 using additional or alternative means, such as a pump.

[0035] At least one of the coolant supply lines 248, 250, 252, 254 includes a coolant control valve 264 for controlling coolant flow through the corresponding coolant supply line. The control valve 264 includes an electrically actuatable valve controllable by the controller 260 to vary or otherwise control the flow rate of coolant through the corresponding supply line. Suitable valves include, for example, without limitation, solenoid valves, electronic expansion valves, and modulating control valves. In the illustrated embodiment, the motor coolant supply line 254 includes the coolant control valve 264. In other embodiments, one or more of the bearing coolant supply lines 248, 250, 252 may include the coolant control valve 264. In yet other embodiments, the motor coolant supply line 254 and one or more of the bearing coolant supply lines 248, 250, 252 may include the coolant control valve 264.

[0036] The motor coolant supply line 254 is configured as a primary or main coolant supply line in the illustrated embodiment, having an inlet 266 connected to the coolant source 262 and an outlet 268 connected to the compressor housing 216 to supply coolant to the fourth coolant flow passage 242. The bearing coolant supply lines 248, 250, 252 are configured as branch lines in the illustrated embodiment, each having an inlet 270 connected to the motor coolant supply line 254 upstream of the coolant control valve 264 and an outlet 272 connected to the compressor housing 216 to supply coolant to the first, second, and third coolant flow passages 236, 238, 240. In other embodiments, the inlets 270 of one or more of the bearing coolant supply lines 248, 250, 252 may be connected to the coolant source 262. In still other embodiments, the motor coolant supply line 254 may be configured as a branch circuit extending from one of the bearing coolant supply lines 248, 250, 252.

[0037] The illustrated cooling circuit 204 also includes a shutoff valve 274 on the main coolant supply line (i.e., motor coolant supply line 254) to allow the flow of coolant to the entire cooling circuit to be shut off to isolate the compressor from the rest of the system (e.g., for service). The shutoff valve 274 may be omitted in other embodiments.

[0038] In the illustrated embodiment, the bearing coolant supply lines 248, 250, 252 are free of shut-off valves or other devices that shut off the supply of coolant through the bearing coolant supply lines 248, 250, 252. Thus, while the cooling circuit 204 is operating, the bearing coolant supply lines 248, 250, 252 are configured to continuously supply coolant to the compressor housing 216 regardless of the position of the coolant control valve 264. In this manner, the bearings of the compressor 202 are continuously supplied with coolant during operation to facilitate maintaining the bearings within a suitable operating temperature range. The bearing coolant flow paths - including the bearing coolant supply lines 248, 250, 252 and associated coolant flow paths 236, 238, 240 defined within the compressor housing 216 - may include flow restrictors along the flow paths to regulate or limit the flow of coolant therethrough. Flow restrictors may be included in the bearing coolant supply lines 248, 250, 252 and / or integrated into the compressor housing 216 (e.g., as a metering orifice along the coolant flow path). In some embodiments, for example, one or more of the coolant inlet ports 244 associated with the bearing coolant flow paths 236, 238, 240 include a metering orifice to control the flow of coolant therethrough.

[0039] A coolant return line 256 is connected to the compressor housing 216 to receive coolant from the multiple coolant flow paths 236, 238, 240, 242 and return the coolant to the low pressure side of the compressor 202. The low pressure side of the compressor 202 generally refers to the portion of the compressor 202 and refrigeration circuit that precedes the compression stages of the compressor 202 (i.e., the first stage 206 and the second stage 208). The low pressure side of the compressor 202 may include, for example, but is not limited to, a portion of the compressor 202 upstream of the first stage impeller 226, an inlet to the first stage 206, and a suction line 212 connected to the inlet of the first stage 206.

[0040] The coolant return line 256 may include any suitable fluid conduit (rigid and / or flexible) that allows for the delivery of coolant from the compressor housing 216 to the low pressure side of the compressor 202. Suitable conduits include, but are not limited to, for example, pipes, hoses, tubes, and combinations thereof. In some embodiments, the coolant return line 256 is constructed of metal tubing, such as copper tubing. In other embodiments, the coolant return line 256 is constructed of other materials. Additionally, in some embodiments, the return line 256 may include a flattened portion or section to facilitate attachment of the temperature sensor 258.

[0041] An inlet 276 of the coolant return line 256 is connected to the common coolant outlet port 246, and an outlet 278 of the coolant return line 256 is connected to the low pressure side of the compressor 202. The coolant in the coolant source 262 (e.g., the condenser 104) is generally at a higher pressure than the low pressure side of the compressor 202. As a result, a pressure differential exists between the coolant in the coolant source 262 and the low pressure side of the compressor 202, which helps drive the coolant through the cooling circuit 204.

[0042] The coolant return line 256 is connected to the common coolant outlet port 246 and receives the coolant from each of the plurality of coolant passages 236, 238, 240, 242 after the coolant has absorbed heat from the motor 234 and / or the bearings 220, 222, 224. As previously described, at least one of the plurality of coolant passages 236, 238, 240, 242 can be arranged such that the coolant flows through at least one coolant passage, in sequence, across at least one bearing 220, 222, 224, through the motor 234, and to the common coolant outlet port 246. In the illustrated embodiment, for example, the third cooling passage 240 is arranged such that the coolant flows through at least one of the at least one bearing 220, 222, 224, through the motor 234, and to the common coolant outlet port 246. As a result, the coolant flowing through the coolant return line 256 absorbs heat from at least one of the bearings 220, 222, 224 and the motor 234 even when the coolant control valve 264 is in the off position.

[0043] The temperature sensor 258 is connected to the coolant return line 256 to detect at least one of the temperature of the coolant in the coolant return line 256. The temperature sensor 258 may include any suitable temperature sensor that enables the cooling circuit 204 to function as described herein, including, for example, but not limited to, a thermistor, a thermocouple, a resistance temperature detector (RTD), a thermal switch, and combinations thereof. In some embodiments, the temperature sensor 258 includes a negative temperature coefficient thermistor.

[0044] The temperature sensor 258 in this embodiment is disposed entirely outside of the compressor housing 216 and the coolant return line 256 and is configured to detect the temperature of the coolant return line 256. For example, as shown in Figure 3, the temperature sensor 258 is coupled to an exterior surface 302 of the coolant return line 256 and configured to detect the temperature of the exterior surface 302. In other embodiments, the temperature sensor 258 may include a probe 304 (shown in dashed lines in Figure 3) that extends into the coolant return line 256 to detect the temperature of the coolant flowing through the coolant return line 256.

[0045] Controller 260 is connected to temperature sensor 258 and coolant control valve 264 and is configured to control operation of coolant control valve 264 (e.g., by opening, closing, or changing the position of coolant control valve 264). In some embodiments, for example, controller 260 is configured to control coolant control valve 264 based on a temperature detected by temperature sensor 258 to control the supply of coolant to compressor housing 216. For example, controller 260 may receive a signal from temperature sensor 258 indicative of a temperature detected by temperature sensor 258, compare the detected temperature to one or more temperature set points, and control coolant control valve 264 based on the detected temperature.

[0046] The controller 260 generally includes any suitable computer and / or other processing unit, including any suitable combination of computers, processing units, and / or the like, communicatively coupled to each other and capable of operating independently or in conjunction with each other (e.g., the controller 260 may form all or part of a controller network). The controller 260 may include one or more modules or devices, one or more of which are enclosed within the compressor 202 or located remotely from the compressor 202. The controller 260 may include one or more processor(s) 280 and associated memory device(s) 282 configured to perform various computer-implemented functions (e.g., performing the calculations, decisions, and functions disclosed herein). As used herein, the term "processor" refers not only to integrated circuits, but also to controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application specific integrated circuits, and other programmable circuits. Additionally, the memory device(s) 282 of the controller 260 may generally be or include, but are not limited to, a memory device(s) including a computer-readable medium (e.g., random access memory (RAM)), a computer-readable non-volatile medium (e.g., flash memory), a floppy disk, a compact disk read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disk (DVD), and / or other suitable memory device. Such memory device(s) 282 may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s), cause the controller 260 to perform various functions described herein, including, but not limited to, controlling the coolant control valve 264 and / or various other suitable computer-implemented functions.

[0047] The controller 260 and / or components of the controller 260 may be integrated or incorporated within other components of the cooling circuit 204 and / or the refrigeration system in which the cooling circuit 204 is incorporated. For example, the controller 260 may be incorporated within a system controller that controls the refrigerant control valve 264 and / or other functions and operations of the compressor 202 and the refrigeration system.

[0048] The controller 260 can be configured to control the coolant control valve 264 based solely on the temperature detected by the temperature sensor 258. As previously described, for example, the temperature sensor 258 is configured to detect the temperature of the coolant in the coolant return line 256 that receives the coolant from each of the coolant flow paths 236, 238, 240, 242 or in the coolant return line 256 itself. Additionally, at least one of the coolant flow paths (e.g., the third coolant flow path 240) is positioned such that the coolant passes through at least one of the bearings 220, 222, 224 and the motor 234 before reaching the common coolant outlet port 246. This allows the coolant flowing through the coolant return line 256 to absorb heat from both the compressor bearings 220, 222, 224 and the motor 234. Thus, the temperature of the coolant in the coolant return line 256 and the temperature of the coolant return line 256 provide an indication of the temperature of the bearings 220, 222, 224 and the motor 234 and can be used to determine when the motor 234 needs additional coolant (and thus the coolant control valve 264 should be opened) or when the motor 234 does not need additional coolant (and thus the coolant control valve 264 should be closed).

[0049] The controller 260 can be configured to receive a signal from the temperature sensor 258 indicative of the temperature detected by the temperature sensor 258 and compare the detected temperature to one or more temperature set points (e.g., stored in the controller's memory 282). Based on the comparison, the controller 260 can be configured to open the coolant control valve 264, thereby permitting additional coolant flow through the motor coolant supply line 254 and the motor 234, or close the coolant control valve 264, thereby reducing coolant flow through the motor coolant supply line 254 and the motor 234. "Opening" and "closing" the coolant control valve 264 can refer to absolute opening and closing (i.e., fully opening and closing the valve) or relative opening and closing of the valve (e.g., opening the valve more than it is already open, closing the valve more than it is already closed).

[0050] The one or more temperature set points may be empirically determined prior to operation, for example, by comparing the measured temperature of the motor with the temperature detected by the temperature sensor 258. In some embodiments, for example, a single temperature set point may be determined based on the temperature detected by the temperature sensor when the measured temperature of the motor 234 reaches a maximum allowable operating temperature. In this case, the temperature set point may be set as a certain number of degrees (e.g., 10°C, 20°C, 30°C, etc.) below the temperature detected by the temperature sensor 258 when the measured temperature of the motor 234 is at the maximum allowable operating temperature. In embodiments using a single temperature set point, the controller 260 may open the coolant control valve 264 when the temperature detected by the temperature sensor 258 exceeds the temperature set point and close the coolant control valve 264 when the temperature detected by the temperature sensor 258 falls below the temperature set point.

[0051] The controller 260 may alternatively or additionally control the coolant control valve 264 based on multiple temperature set points, such as two temperature set points. In such an embodiment, the two temperature set points may define a suitable temperature window or range. In such an embodiment, the controller 260 may open the coolant control valve 264 when the temperature detected by the temperature sensor 258 is above a first, higher temperature set point and close the coolant control valve 264 when the temperature detected by the temperature sensor 258 is below a second, lower temperature set point.

[0052] 4 is a graph 400 illustrating the operation of the coolant control valve 264 based on two temperature set points, indicated by lines 402 and 404. The first and second temperature set points 402 and 404 generally define a temperature range above which the coolant control valve 264 opens and below which the coolant control valve 264 closes. The temperature range may be any suitable temperature range that enables the compressor 202 to function as described herein, including, for example, but not limited to, 2° F., 5° F., 10° F., 15° F., 20° F., 25° F., 30° F., 35° F., 40° F., 50° F., or higher. The temperature detected by the temperature sensor 258 is illustrated by curve 406 in FIG. 4. As shown in FIG. 4, when the detected temperature 406 exceeds the first temperature set point 402, the controller 260 opens the coolant control valve 264 to provide additional coolant to the motor 234. The additional coolant supplied to the motor 234 causes the temperature of the coolant in the coolant return line 256 to initially increase and then decrease as additional heat is removed from the motor 234 (e.g., from the stator), causing the sensed temperature 406 to decrease. When the sensed temperature 406 falls below the second temperature set point 404, the controller 260 closes the coolant control valve 264, reducing the coolant flow to the motor 234. As a result, the temperature of the coolant in the coolant return line 256 increases, as shown in FIG. 4. When the sensed temperature 406 again reaches a temperature above the first temperature set point 402, the controller 260 again opens the coolant control valve 264 to supply additional coolant to the motor 234, repeating the cycle.

[0053] Figure 5 is a schematic diagram of another example compressor cooling system 500 suitable for use in the refrigeration system 100 of Figure 1. The compressor cooling system 500 includes a cooling circuit 502 including a first temperature sensor 258 connected to the coolant return line 256. Additionally, the cooling circuit 502 includes a second temperature sensor 504 connected to the compressor housing 216 (e.g., the shell of the compressor housing 216) to detect the temperature of the compressor housing 216. The second temperature sensor 504, in this embodiment, is connected to an exterior surface of the compressor housing 216 and configured to detect the temperature of the exterior surface.

[0054] Additionally, in this embodiment, the cooling circuit 502 includes a main bearing coolant supply line 506 that branches off from the motor coolant supply line 254 and supplies each of the multiple bearing coolant supply lines 248, 250, 252. The main bearing coolant supply line 506 includes a bearing coolant control valve 508 that is used to control additional or supplemental coolant flow to the compressor bearings 220, 222, 224, and the motor coolant supply line 254 includes a motor coolant control valve 510 that controls additional or supplemental coolant flow to the motor 234. More specifically, each of the motor coolant supply line 254 and the main bearing coolant supply line 506 includes a respective bypass line 512, 514. The bypass lines 512, 514 allow coolant to bypass the respective motor coolant control valve 510 and bearing coolant control valve 508 to continuously supply coolant to the motor 234 and compressor bearings 220, 222, 224, respectively, regardless of the position of the motor coolant control valve 510 and bearing coolant control valve 508. The bypass lines 512, 514 may include metering orifices or other metering devices to restrict or regulate the flow of coolant therethrough. The motor coolant control valve 510 may open to provide additional or supplemental coolant flow to the motor 234, and the bearing coolant control valve 508 may open to provide additional or supplemental coolant flow to the bearings 220, 222, 224.

[0055] 5, the motor coolant control valve 510 and the bearing coolant control valve 508 are connected to the controller 260. The controller 260 may be configured to control (i.e., open or close) the bearing coolant control valve 508 and the motor coolant control valve 510 based on temperatures detected by the first temperature sensor 258 and the second temperature sensor 504. For example, the controller 260 may be configured to control the bearing coolant control valve 508 based on the temperature detected by the first temperature sensor 258 and to control the motor coolant control valve 510 based on the temperature detected by the second temperature sensor 504. In particular, the controller 260 may compare the temperature detected by the first temperature sensor 258 to a first temperature set point associated with the first temperature sensor 258 and open or close the bearing coolant control valve 508 based on the comparison. For example, the controller 260 can open the bearing coolant control valve 508 to provide supplemental coolant flow to the bearings 220, 222, 224 when the temperature detected by the first temperature sensor 258 is above a first temperature set point and close the bearing coolant control valve 508 to reduce the coolant flow to the bearings 220, 222, 224 when the temperature detected by the first temperature sensor 258 is below the first temperature set point. Similarly, the controller 260 can open the motor coolant control valve 510 to provide supplemental coolant flow to the motor 234 when the temperature detected by the second temperature sensor 504 is above a second temperature set point and close the motor coolant control valve 510 to reduce the coolant flow to the motor 234 when the temperature detected by the second temperature sensor 504 is below the first temperature set point.

[0056] 6 is a graph 600 illustrating the operation of the bearing coolant control valve 508 and the motor coolant control valve 510 in accordance with an exemplary control scheme or algorithm. In this control scheme, the motor coolant control valve 510 is controlled based on a fixed or set motor temperature set point, represented by line 602, and the bearing coolant control valve 508 is controlled based on a variable bearing temperature set point, represented by line 604. The temperature sensed by the first temperature sensor 258 is represented by curve 606 in FIG. 6, and the temperature sensed by the second temperature sensor 504 is represented by curve 608 in FIG. 6.

[0057] In this embodiment, the bearing temperature set point 604 is determined continuously or continuously (e.g., periodically or in real time) based on the detected temperature 608 of the compressor housing 216 detected by the second temperature sensor 504. Specifically, the bearing temperature set point 604 is calculated or determined by subtracting an offset temperature 610 from the measured temperature 608 of the compressor housing 216. As shown in FIG 6, for example, if the measured temperature 608 of the compressor housing 216 increases, the bearing temperature set point 604 also increases by the same amount, but remains offset from the measured temperature 608 by the offset temperature 610. The offset temperature 610 may be any suitable offset temperature that enables the compressor 500 to function as described herein, including, for example, but not limited to, a range of 0°F to 30°F, a range of 0°F to 25°F, a range of 5°F to 30°F, a range of 5°F to 20°F, a range of 5°F to 15°F, a range of 10°F to 25°F, and a range of 10°F to 20°F.

[0058] As shown in FIG. 6, when the sensed temperature 608 of the compressor housing 216 exceeds the motor temperature set point 602, the controller 260 opens the motor coolant control valve 510 to provide additional coolant to the motor 234. The additional coolant provided to the motor 234 causes the temperature of the compressor housing 216 to decrease after a period of time, which results in a decrease in the sensed temperature 608. When the sensed temperature 608 of the compressor housing 216 decreases to a temperature below the motor temperature set point 602, the controller 260 closes the motor coolant control valve 510, which reduces the coolant flow to the motor 234. This causes the temperature of the motor 234 and the compressor housing 216 to increase, as shown in FIG. 6.

[0059] Additionally, when the sensed temperature 606 of the coolant return line 256 exceeds the bearing temperature set point 604, the controller 260 opens the bearing coolant control valve 508 to supply additional coolant to the bearings 220, 222, 224. The additional coolant supplied to the bearings 220, 222, 224 causes the temperature of the coolant in the coolant return line 256 and the temperature of the coolant return line 256 to decrease after a period of time, resulting in a decrease in the sensed temperature 606. When the sensed temperature 606 of the coolant return line 256 decreases to a temperature below the bearing temperature set point 604, the controller 260 closes the bearing coolant control valve 508 to decrease the flow of coolant to the bearings 220, 222, 224. As a result, the coolant temperature in the coolant return line 256 increases, as shown in FIG. 6. This cycle is repeated during operation of the compressor 500. The motor temperature set point 602 and the offset temperature 610 can be empirically determined prior to operation.

[0060] Figure 7 is a perspective view of an exemplary compressor 700 suitable for use in the refrigeration system 100 of Figure 1 and the compressor cooling systems 200, 500 of Figures 2 and 5. Figure 8 is a cross-sectional view taken along line 8-8 of the compressor 700 of Figure 7. In the illustrated embodiment, the compressor 700 is a two-stage centrifugal compressor, although in other embodiments, the compressor 700 may include a single stage or more than two stages. In still other embodiments, the compressor 700 may be a compressor other than a centrifugal compressor.

[0061] The compressor 700 generally includes a compressor housing 702 that defines at least one sealed cavity in which each stage of refrigerant compression is accomplished. The compressor 700 receives refrigerant from a suction line 706 and includes a first refrigerant inlet 704 that introduces refrigerant vapor to a first compression stage 708, a first refrigerant outlet 710, a refrigerant transfer conduit 712 that transfers compressed refrigerant from the first compression stage 708 to a second compression stage 714, a second refrigerant inlet 716 that introduces refrigerant vapor to the second compression stage 714, and a second refrigerant outlet 718. The refrigerant transfer conduit 712 is operatively connected at both ends to the first refrigerant outlet 710 and the second refrigerant inlet 716, respectively. The second refrigerant outlet 718 delivers compressed refrigerant from the second compression stage 714 to a cooling or refrigeration system in which the compressor 700 is incorporated (e.g., refrigeration system 100).

[0062] 8, the compressor housing 702 includes a first housing end or cap 802 that encloses a first compression stage 708 and a second housing end or cap 804 that encloses a second compression stage 714. The first compression stage 708 and the second compression stage 714 are located at opposite ends of the compressor 700, but may also be located at the same end of the compressor 700. The first compression stage 708 includes a first impeller 806 configured to add kinetic energy to the refrigerant entering via the first refrigerant inlet 704. The kinetic energy imparted to the refrigerant by the first impeller 806 is converted to increased refrigerant pressure (i.e., compression) as the refrigerant velocity slows upon transfer to a sealed cavity (e.g., diffuser). Similarly, the second compression stage 714 includes a second impeller 810 configured to add kinetic energy to the refrigerant transferred from the first compression stage 708 entering via the second refrigerant inlet 716. The kinetic energy imparted to the refrigerant by the second impeller 810 is converted to increased refrigerant pressure (i.e., compression) as the refrigerant velocity slows during transfer to the sealed cavity (e.g., diffuser). The compressed refrigerant exits the second compression stage 714 via the second refrigerant outlet 718.

[0063] The first impeller 806 and the second impeller 810 are coupled at opposite ends of a drive shaft 814. The drive shaft 814 is operatively coupled to a motor 816 located between the first impeller 806 and the second impeller 810 such that the first impeller 806 and the second impeller 810 rotate at a selected rotational speed to compress the refrigerant to a preselected target (e.g., mass flow rate) that exits through a second refrigerant outlet 718. Any suitable motor may be incorporated into the compressor 700, including, but not limited to, an electric motor. The exemplary compressor 700 includes an electric motor having a stator 818 connected to the compressor housing 702 and a rotor 820 connected to the drive shaft 814. An air gap (not labeled in FIG. 8 ) is defined between the stator 818 and the rotor 820 to allow the refrigerant to flow through the bottom. Drive shaft 814 is supported by first and second radial foil bearings 822, 824, and a thrust foil bearing 826. Additional details of compressor 700, including additional components and operation of compressor 700, are described in U.S. Patent Application Publication No. 2020 / 0256347, the disclosure of which is incorporated herein by reference.

[0064] 8, the compressor housing 702 has a plurality of coolant passages 828, 830, 832, 834 defined therein that supply coolant to the bearings 822, 824, 826 and the motor 816. The exemplary compressor 700 includes a first coolant passage 828, a second coolant passage 830, a third coolant passage 832, and a fourth coolant passage 834. The first coolant passage 828 supplies coolant to the thrust bearing 826, the second coolant passage 830 supplies coolant to the first radial bearing 822, the third coolant passage 832 supplies coolant to the second radial bearing 824, and the fourth coolant passage 834 supplies coolant to the motor 816. The compressor housing 702 also defines a common coolant outlet port 836 in the illustrated embodiment. A common coolant outlet port 836 receives coolant from each of the multiple coolant passages 828 , 830 , 832 , 834 .

[0065] The first coolant passage 828 extends radially inward through the first housing end 802, around the thrust bearing 826, axially along the drive shaft 814 between the first bearing housing 808 and the drive shaft 814, and radially outward to a common coolant outlet port 836. The second coolant passage 830 extends radially inward through the first bearing housing 808 to the first radial bearing 822, axially along the first radial bearing 822 and the drive shaft 814, and radially outward to the common coolant outlet port 836. The third coolant passage 832 extends radially inward through the second bearing housing 812 to the second radial bearing 824, axially along the second radial bearing 824 and the drive shaft 814, radially outward toward an air gap defined between the stator 818 and the rotor 820, axially through the air gap, and radially outward to the common coolant outlet port 836. The fourth coolant passage 834 extends spirally around the stator 818 through a helical groove 838 defined by the compressor housing 702. The fourth coolant passage 834 then extends radially inward to an air gap defined between the stator 818 and the rotor 820, axially through the air gap, and radially outward to a common coolant outlet port 836.

[0066] 8, the coolant passages 828, 830, 832, 834 can share common or overlapping portions of the compressor housing 702. For example, the first coolant passage 828 overlaps and interdigitates with the second coolant passage 238 at the first radial bearing 822, and the third coolant passage 832 overlaps and interdigitates with the fourth coolant passage 834 at the motor 816. Further, as shown in FIG. 8 and described above, the coolant passages 828, 830, 832, 834 in the exemplary compressor housing 702 are arranged such that coolant flows through at least one of the coolant passages 828, 830, 832, 834, in turn, across at least one bearing 822, 824, 826, through the motor 816 and to a common coolant outlet port 836. For example, the third coolant passage 832 supplies coolant to the second radial bearing 824 and to the motor 816 (e.g., by flowing across the stator 818 and rotor 820), causing the coolant to absorb heat from both the bearings 822, 824, 826 and the motor 816.

[0067] A coolant return line 840 (shown diagrammatically in FIGS. 7 and 8 ) has an inlet 842 connected to the common coolant outlet port 836 and an outlet 844 connected to the suction line 706 for returning coolant to the low pressure side of the compressor 700. The suction line 706 is generally at a lower pressure than the coolant supplied to the compressor housing 702, which may be supplied from a higher pressure side of the refrigeration system in which the compressor 700 is incorporated, such as downstream of the condenser. As a result, a pressure differential exists between the coolant of the coolant source and the suction line 706, facilitating driving the coolant through the multiple coolant flow paths 828, 830, 832, 834.

[0068] Embodiments of the described systems and methods achieve superior results as compared to previous systems and methods associated with centrifugal compressor cooling systems. For example, the cooling circuits and associated coolant control valves and schemes disclosed herein provide continuous coolant to the compressor bearings, thereby protecting the bearings, while allowing additional coolant to be supplied to the motor for additional cooling based on temperature feedback. Furthermore, the cooling systems disclosed herein do not require the use of external or additional liquid pumps and require few or no additional components, thereby providing a relatively simple and reliable compressor cooling system.

[0069] Exemplary embodiments of compressor systems and methods, such as refrigerant compressors, are described in detail above. The systems and methods are not limited to the specific embodiments described herein, but rather the components of the systems and methods can be used separately and independently of other components described herein. For example, the refrigeration circuits described herein can be used with compressors other than centrifugal compressors, including, but not limited to, scroll compressors, rotary compressors, and reciprocating compressors.

[0070] When introducing elements of the present disclosure or embodiments thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the element. The terms "comprise," "include," and "have" are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of terms indicating a specific orientation (e.g., "top," "bottom," "side," etc.) is for convenience of description and does not require a particular orientation of the described items.

[0071] Since various changes may be made in the above structures and methods without departing from the scope of the disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings be interpreted in an illustrative and not a limiting sense.

Claims

1. 1. A centrifugal compressor comprising: Compressor housing; a shaft rotatably supported within said compressor housing by at least one bearing; an impeller connected to the shaft; and a motor operatively connected to the shaft, the compressor housing having a plurality of coolant passages defined therein that supply coolant to the at least one bearing and the motor; a compressor having 1. A cooling circuit comprising: a coolant supply line connected to the compressor housing to supply the coolant to at least one of the plurality of coolant flow passages, the coolant supply line having a coolant control valve for controlling coolant flow through the coolant supply line; a coolant return line connected to the compressor housing to receive the coolant from the plurality of coolant flow paths and return the coolant to a low pressure side of the compressor; a temperature sensor connected to the coolant return line to detect at least one of a temperature of the coolant return line and a temperature of the coolant in the coolant return line; and a controller coupled to the temperature sensor and to the coolant control valve, the controller configured to control the coolant control valve based on the temperature detected by the temperature sensor to control a supply of the coolant to the compressor housing; a cooling circuit having Compressor system.

2. the temperature sensor is connected to an outer surface of the coolant return line to detect a temperature of the outer surface; The compressor system of claim 1 .

3. the compressor housing further defines a common coolant outlet port for receiving the coolant from each of the plurality of coolant flow passages, the coolant return line having an inlet connected to the common coolant outlet port and an outlet connected to the low pressure side of the centrifugal compressor. The compressor system of claim 1 .

4. at least one coolant passage of the plurality of coolant passages is arranged such that the coolant flows through the at least one coolant passage, in sequence, across the at least one bearing, through the motor, and to the common coolant outlet port. The compressor system of claim 3 .

5. The coolant supply line includes a motor coolant supply line having an inlet connected to a coolant source and an outlet connected to the compressor housing, the cooling circuit further comprising: at least one bearing coolant supply line having an inlet connected to the motor coolant supply line upstream of the coolant control valve and an outlet connected to the compressor housing to supply the coolant to at least one of the plurality of coolant flow paths, the at least one bearing coolant supply line configured to continuously supply the coolant to the compressor housing regardless of a position of the coolant control valve; The compressor system of claim 1 .

6. at least one coolant flow passage of the plurality of coolant flow passages is arranged such that the coolant flows through the at least one coolant flow passage, in sequence, across the at least one bearing, through the motor, and to a common coolant outlet port defined by the compressor housing, and the at least one bearing coolant supply line is connected to the at least one coolant flow passage. The compressor system of claim 5 .

7. The centrifugal compressor comprises: a first radial bearing rotatably supporting a first end of the shaft; a second radial bearing rotatably supporting a second end of the shaft; and a thrust bearing, wherein the plurality of coolant passages supply the coolant to each of the first radial bearing, the second radial bearing, and the thrust bearing. The compressor system of claim 1 .

8. the compressor housing defines a plurality of refrigerant inlet ports, each refrigerant inlet port being connected to one of the plurality of refrigerant flow paths, at least one of the refrigerant inlet ports having a metering orifice for restricting flow of the refrigerant therethrough. The compressor system of claim 1 .

9. the coolant supply line is a main bearing coolant supply line, the coolant control valve is a bearing coolant control valve, the cooling circuit further comprising a plurality of bearing coolant supply lines connected to the main bearing coolant supply lines to receive the coolant therefrom, the main bearing coolant supply lines having a bypass line to allow the coolant to bypass the bearing coolant control valve to provide a continuous flow of the coolant to the compressor housing regardless of the position of the bearing coolant control valve. The compressor system of claim 1 .

10. a motor coolant supply line having an inlet connected to a coolant source and an outlet connected to the compressor housing, the motor coolant supply line having a motor coolant control valve and a bypass line that allows the coolant to bypass the motor coolant control valve to provide a continuous flow of the coolant to the compressor housing regardless of the position of the motor coolant control valve; The compressor system of claim 9.

11. the temperature sensor is a first temperature sensor, the cooling circuit further includes a second temperature sensor connected to the compressor housing to detect a temperature of the compressor housing, and the controller is connected to the second temperature sensor and configured to control the motor coolant control valve based on the temperature detected by the second temperature sensor. The compressor system of claim 10.

12. the second temperature sensor is coupled to an exterior surface of the compressor housing. The compressor system of claim 11.

13. 1. A compressor cooling system, the cooling system comprising: a coolant supply line having a coolant control valve for controlling coolant flow therethrough, the coolant supply line being connectable to a compressor housing of the compressor to supply coolant to at least one of a plurality of coolant flow passages defined within the compressor housing; a coolant return line connectable to the compressor housing for receiving coolant from a plurality of coolant flow paths and returning the coolant to a low pressure side of the compressor; a temperature sensor connected to the coolant return line to detect at least one of a temperature of the coolant return line and a temperature of the coolant in the coolant return line; and a controller coupled to the temperature sensor and to the coolant control valve, the controller configured to control the coolant control valve based on the temperature detected by the temperature sensor to control a supply of coolant through the coolant supply line; Cooling system.

14. the temperature sensor is connected to an outer surface of the coolant return line to detect a temperature of the outer surface; The cooling system of claim 13.

15. The coolant supply line includes a motor coolant supply line having an inlet connected to a coolant source, and the cooling system further includes: at least one bearing coolant supply line connectable to the compressor housing to supply the coolant to at least one of the plurality of coolant flow paths, the at least one bearing coolant supply line having an inlet connected to the motor coolant supply line upstream of the coolant control valve and configured to continuously supply the coolant to the compressor housing regardless of a position of the coolant control valve; The cooling system of claim 14.

16. the coolant supply line is a main bearing coolant supply line, the coolant control valve is a bearing coolant control valve, the cooling system further comprising a plurality of bearing coolant supply lines connected to and receiving coolant therefrom, the main bearing coolant supply lines having a bypass line that allows coolant to bypass the bearing coolant control valve to provide a continuous flow of coolant to the compressor housing regardless of the position of the bearing coolant control valve. The cooling system of claim 13.

17. a motor coolant supply line having an inlet connected to a coolant source and an outlet connected to the compressor housing, the motor coolant supply line having a motor coolant control valve and a bypass line that allows coolant to bypass the motor coolant control valve to provide a continuous flow of coolant to the compressor housing regardless of the position of the motor coolant control valve; 17. The cooling system of claim 16.

18. the temperature sensor is a first temperature sensor, the cooling system further includes a second temperature sensor coupled to the compressor housing for detecting a temperature of the compressor housing, and the controller is coupled to the second temperature sensor and configured to control the motor coolant control valve based on the temperature detected by the second temperature sensor.

20. The cooling system of claim 17.

19. the second temperature sensor is coupled to an exterior surface of the compressor housing.

20. The cooling system of claim 18.

20. 1. A compressor comprising: Compressor housing; a shaft rotatably supported within said compressor housing by at least one bearing; an impeller connected to the shaft; and a motor operatively connected to the shaft, the compressor housing having a plurality of coolant passages defined therein that supply coolant to the at least one bearing and the motor; a compressor having Evaporator; Condenser; An expansion device; and 1. A cooling circuit comprising: a coolant supply line connected to the compressor housing to supply coolant to at least one of the plurality of coolant flow passages, the coolant supply line having a coolant control valve for controlling coolant flow through the coolant supply line; a coolant return line connected to the compressor housing to receive coolant from the plurality of coolant flow paths and return coolant to a low pressure side of the compressor; a temperature sensor connected to the coolant return line to detect at least one of a temperature of the coolant return line and a temperature of the coolant in the coolant return line; and a controller coupled to the temperature sensor and to the coolant control valve, the controller configured to control the coolant control valve based on the temperature detected by the temperature sensor to control a supply of the coolant to the compressor housing; a cooling circuit; Refrigeration system.

21. the temperature sensor is connected to an outer surface of the coolant return line to detect a temperature of the outer surface; 21. The refrigeration system of claim 20.

22. the compressor housing further defines a common coolant outlet port for receiving the coolant from each of the plurality of coolant flow paths, the coolant return line having an inlet connected to the common coolant outlet port and an outlet connected to the low pressure side of the compressor.

21. The refrigeration system of claim 20.

23. The coolant supply line includes a motor coolant supply line having an inlet connected to a coolant source and an outlet connected to the compressor housing, the cooling circuit further comprising: at least one bearing coolant supply line having an inlet connected to the motor coolant supply line upstream of the coolant control valve and an outlet connected to the compressor housing to supply the coolant to at least one of the plurality of coolant flow paths, the at least one bearing coolant supply line configured to continuously supply the coolant to the compressor housing regardless of a position of the coolant control valve; 21. The refrigeration system of claim 20.

24. at least one coolant flow passage of the plurality of coolant flow passages is arranged such that the coolant flows through the at least one coolant flow passage, in sequence, across the at least one bearing, through the motor, and to a common coolant outlet port defined by the compressor housing, and the at least one bearing coolant supply line is connected to the at least one coolant flow passage.

24. The refrigeration system of claim 23.

25. the coolant supply line is a main bearing coolant supply line, the coolant control valve is a bearing coolant control valve, the cooling circuit further comprising a plurality of bearing coolant supply lines connected to the main bearing coolant supply lines to receive the coolant therefrom, the main bearing coolant supply lines having a bypass line to allow the coolant to bypass the bearing coolant control valve to provide a continuous flow of the coolant to the compressor housing regardless of the position of the bearing coolant control valve.

21. The refrigeration system of claim 20.

26. The temperature sensor is a first temperature sensor, and the cooling circuit comprises: a second temperature sensor coupled to the compressor housing to detect a temperature of the compressor housing; and a motor coolant supply line having an inlet connected to a coolant source and an outlet connected to the compressor housing, the motor coolant supply line having a motor coolant control valve and a bypass line to allow the coolant to bypass the motor coolant control valve to provide a continuous flow of the coolant to the compressor housing regardless of the position of the motor coolant control valve; the controller is coupled to the second temperature sensor and configured to control the motor coolant control valve based on the temperature detected by the second temperature sensor.

26. The refrigeration system of claim 25.

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