Patent Publication Number: US-2021190395-A1

Title: Hybrid cooling systems for hermetic motors

Description:
BACKGROUND 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     A compressor of a refrigeration cycle is driven by a shaft, which may be rotated by a motor. Heat (e.g., thermal energy) may be generated as electrical current passes through a stator of the motor formed by a series of windings, which drives rotation of a rotor of the motor that is coupled to the shaft. The rotor and stator are contained within a motor housing, which may experience an increase in temperature as heat is generated by operation of the motor. In some compressors, the rotor may be supported by electromagnetic bearings, which may also generate heat and further increase the temperature within the motor housing. Accordingly, cooling fluid may be provided to the motor via a cooling system to remove heat and avoid a decrease in performance or shutdown of the motor caused by overheating. Unfortunately, the cooling fluid provided by some cooling systems may generate large temperature gradients (e.g., cold spots, hot spots) within the motor. For example, the cooling fluid may be a chilled liquid, which may occasionally overcool a housing of the motor and cause condensation to form on an exterior of the housing. In addition to cosmetic issues, water condensation may pose reliability issues to electronic components located on the exterior of the housing. 
     SUMMARY 
     A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below. 
     In one embodiment, a hybrid cooling system for a hermetic motor includes an annular cavity in a motor housing. The annular cavity is configured to receive a vapor flow from a main refrigerant circuit. The hybrid cooling system includes at least one annulus in the motor housing. The at least one annulus is configured to receive a liquid flow from the main refrigerant circuit. The hybrid cooling system also includes a sleeve disposed within the motor housing adjacent to the annular cavity and the at least one annulus. At least one radial opening is defined through the sleeve and in fluid communication with the annular cavity. The hybrid cooling system also includes a stator at least partially surrounded by the sleeve, as well as a gap defined between the stator and a rotor of the hermetic motor. Additionally, the hybrid cooling system includes a vent slot of the stator configured to receive the vapor flow from the annular cavity through the at least one radial opening of the sleeve and direct the vapor flow to the gap. The hybrid cooling system also includes an exit path in the motor housing configured to direct an evaporated vapor flow, generated from the liquid flow contacting the stator, and the vapor flow out of the motor housing 
     In another embodiment, a hermetic motor for a compressor of a heating, ventilating, air conditioning, and refrigeration (HVAC&amp;R) system includes a stator configured to cause rotation of a rotor that drives the compressor. A vent slot is defined through a central portion of the stator to fluidly couple a radially outward surface of the stator to an annular gap defined between the stator and the rotor. The hermetic motor includes a sleeve circumferentially surrounding a portion of the radially outward surface of the stator and a motor housing disposed around the stator and the sleeve. The motor housing defines a first annulus and a second annulus each adjacent to the sleeve. The first annulus and the second annulus are each configured to direct a respective liquid flow through the sleeve to the stator. The motor housing also defines an annular chamber adjacent to the sleeve. The annular chamber is axially positioned between the first annulus and the second annulus. The annular chamber is configured to direct a vapor flow from the annular chamber, through the sleeve and the vent slot, and into the annular gap. 
     In another embodiment, a heating, ventilating, air conditioning, and refrigeration (HVAC&amp;R) system includes a main refrigerant circuit including a compressor, a condenser, an expansion device, and an evaporator coupled in series. A high pressure side of the main refrigerant circuit is defined between an outlet of the compressor and an inlet of the expansion device. The HVAC&amp;R system includes a motor configured to drive the compressor and a hybrid cooling system. The hybrid cooling system includes a cooling refrigerant circuit configured to direct a vapor flow from the high pressure side of the main refrigerant circuit to the hermetic motor, direct a liquid flow from the condenser to the hermetic motor, and direct warmed refrigerant from the motor to the evaporator. The hybrid cooling system also includes a housing of the motor defining a first annulus, a second annulus, and an annular chamber axially positioned between the first annulus and the second annulus. The first annulus and the second annulus are each configured to receive the liquid flow from the cooling refrigerant circuit and direct the liquid flow to a stator of the hermetic motor. The annular chamber is configured to receive the vapor flow from the cooling refrigerant circuit and direct the vapor flow to a gap between the stator and a rotor of the hermetic motor. 
     Other features and advantages of the present application will be apparent from the following, more detailed description of the embodiments, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a perspective view of an embodiment of a building that may utilize a heating, ventilation, air conditioning, and refrigeration (HVAC&amp;R) system in a commercial setting, in accordance with an aspect of the present disclosure; 
         FIG. 2  is a perspective view of an embodiment of a vapor compression system, in accordance with an aspect of the present disclosure; 
         FIG. 3  is a schematic of an embodiment of the vapor compression system of  FIG. 2 , in accordance with an aspect of the present disclosure; 
         FIG. 4  is a schematic of an embodiment of the vapor compression system of  FIG. 2 , in accordance with an aspect of the present disclosure; 
         FIG. 5  is a schematic of an embodiment of the vapor compression system having a hermetic motor that utilizes a hybrid cooling system, which receives refrigerant vapor from a condenser, in accordance with an aspect of the present disclosure; 
         FIG. 6  is a schematic of an embodiment of the vapor compression system having a hermetic motor that utilizes a hybrid cooling system, which receives refrigerant vapor from a compressor, in accordance with an aspect of the present disclosure; 
         FIG. 7  is a cross-sectional side view of an embodiment of the hermetic motor of  FIG. 5 or 6  including the hybrid cooling system, in accordance with an aspect of the present disclosure; and 
         FIG. 8  is a partial cross-sectional side view of an embodiment of the hermetic motor of  FIG. 7  illustrating a refrigerant vapor inlet and two refrigerant liquid inlets, in accordance with an aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     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&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     Embodiments of the present disclosure are directed toward a heating, ventilation, air conditioning, and refrigeration (HVAC&amp;R) system having a hybrid cooling system that controls a temperature of a motor (e.g., hermetic motor, electric motor), which is utilized to drive a compressor of the HVAC&amp;R system. To drive the compressor, electrical current is directed through a stator of the motor, which causes a rotor of the motor to rotate, generating rotation of components of the compressor via a shaft coupled between the rotor and the compressor. Motors generate heat during their operation, for example, as results of winding resistance and eddy current losses from the electrical current that is supplied to the motor. The heat produced by the motor may be transferred to a motor housing as thermal energy, thereby increasing a temperature of the motor. Accordingly, a cooling system may be coupled to the motor housing to absorb the thermal energy and reduce the temperature of, or cool, the motor. In some embodiments, the cooling system circulates refrigerant from a main refrigerant circuit of the HVAC&amp;R system into the motor housing to absorb the thermal energy in the motor housing. For example, refrigerant (e.g., the cooling fluid of the cooling system) may be directed from a condenser of the HVAC&amp;R system and into the motor housing to absorb thermal energy generated during operation of the motor. The refrigerant may then be directed back to the main refrigerant circuit of the HVAC&amp;R system from the motor housing. 
     It is now recognized that only providing the refrigerant to the motor housing as a liquid may limit a range of operation of the HVAC&amp;R system to operating modes that enable the motor to be suitably cooled by the refrigerant liquid. Additionally, it is now recognized that the refrigerant liquid may overcool the motor housing (e.g., below a dew point) in certain situations, enabling condensation to accumulate on an exterior surface of the motor housing. As such, the present disclosure introduces a hybrid cooling system that delivers both refrigerant vapor (e.g., cooling vapor) and refrigerant liquid (e.g., cooling liquid), via respective inlet ports, to the motor to efficiently control a temperature of the motor and the motor housing thereof. For example, the hybrid cooling system includes a first inlet port at a first end of the stator of the motor, a second inlet port at a second end of the stator, and a third inlet port positioned between the first and second inlet ports. The hybrid cooling system directs (e.g., injects) refrigerant liquid through the first and second inlet ports and, further, directs refrigerant vapor to a jacket (e.g., annular chamber, heating jacket) that surrounds the stator via the third inlet port. As the refrigerant liquid absorbs heat from the motor, some liquid refrigerant may evaporate into a vapor and travel along a gap between the rotor and the stator. In addition to regulating the temperature of components of the motor, the refrigerant vapor may augment or increase a flow of the vapor along the gap, further improving or equalizing a temperature distribution of the rotor and stator. As such, the hybrid cooling system may increase an efficiency of the motor and increase the operating range of the compressor and/or the HVAC&amp;R system, while reducing overcooling and/or external condensation of the motor. 
     Turning now to the drawings,  FIG. 1  is a perspective view of an embodiment of an environment for a heating, ventilation, air conditioning, and refrigeration (HVAC&amp;R) system  10  in a building  12  for a typical commercial setting. The HVAC&amp;R system  10  may include a vapor compression system  14  that supplies a chilled liquid, which may be used to cool the building  12 . The HVAC&amp;R system  10  may also include a boiler  16  to supply warm liquid to heat the building  12  and an air distribution system which circulates air through the building  12 . The air distribution system can also include an air return duct  18 , an air supply duct  20 , and/or an air handler  22 . In some embodiments, the air handler  22  may include a heat exchanger that is connected to the boiler  16  and the vapor compression system  14  by conduits  24 . The heat exchanger in the air handler  22  may receive either heated liquid from the boiler  16  or chilled liquid from the vapor compression system  14 , depending on the mode of operation of the HVAC&amp;R system  10 . The HVAC&amp;R system  10  is shown with a separate air handler on each floor of building  12 , but in other embodiments, the HVAC&amp;R system  10  may include air handlers  22  and/or other components that may be shared between or among floors. 
       FIGS. 2 and 3  are embodiments of the vapor compression system  14  that can be used in the HVAC&amp;R system  10 . The vapor compression system  14  may circulate a refrigerant through a circuit starting with a compressor  32 . The circuit may also include a condenser  34 , an expansion valve(s) or device(s)  36 , and a liquid chiller or an evaporator  38 . The vapor compression system  14  may further include a control panel  40  that has an analog to digital (A/D) converter  42 , a microprocessor  44 , a non-volatile memory  46 , and/or an interface board  48 . 
     Some examples of fluids that may be used as refrigerants in the vapor compression system  14  are hydrofluorocarbon (HFC) based refrigerants, for example, R-410A, R-407, R-134a, hydrofluoro olefin (HFO), “natural” refrigerants like ammonia (NH 3 ), R-717, carbon dioxide (CO 2 ), R-744, or hydrocarbon based refrigerants, water vapor, or any other suitable refrigerant. In some embodiments, the vapor compression system  14  may be configured to efficiently utilize refrigerants having a normal boiling point of about 19 degrees Celsius (66 degrees Fahrenheit) at one atmosphere of pressure, also referred to as low pressure refrigerants, versus a medium pressure refrigerant, such as R-134a. As used herein, “normal boiling point” may refer to a boiling point temperature measured at one atmosphere of pressure. 
     In some embodiments, the vapor compression system  14  may use one or more of a variable speed drive (VSDs)  52 , a motor  50 , the compressor  32 , the condenser  34 , the expansion valve or device  36 , and/or the evaporator  38 . The motor  50  may drive the compressor  32  and may be powered by a variable speed drive (VSD)  52 . The VSD  52  receives alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source, and provides power having a variable voltage and frequency to the motor  50 . In other embodiments, the motor  50  may be powered directly from an AC or direct current (DC) power source. The motor  50  may include any type of 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. 
     The compressor  32  compresses a refrigerant vapor and delivers the vapor to the condenser  34  through a discharge passage. In some embodiments, the compressor  32  may be a centrifugal compressor. The refrigerant vapor delivered by the compressor  32  to the condenser  34  may transfer heat to a cooling fluid (e.g., water or air) in the condenser  34 . The refrigerant vapor may condense to a refrigerant liquid in the condenser  34  as a result of thermal heat transfer with the cooling fluid. The liquid refrigerant from the condenser  34  may flow through the expansion device  36  to the evaporator  38 . In the illustrated embodiment of  FIG. 3 , the condenser  34  is water cooled and includes a tube bundle  54  connected to a cooling tower  56 , which supplies the cooling fluid to the condenser. 
     The liquid refrigerant delivered to the evaporator  38  may absorb heat from another cooling fluid, which may or may not be the same cooling fluid used in the condenser  34 . The liquid refrigerant in the evaporator  38  may undergo a phase change from the liquid refrigerant to a refrigerant vapor. As shown in the illustrated embodiment of  FIG. 3 , the evaporator  38  may include a tube bundle  58  having a supply line  60 S and a return line  60 R connected to a cooling load  62 . The cooling fluid of the evaporator  38  (e.g., water, ethylene glycol, calcium chloride brine, sodium chloride brine, or any other suitable fluid) enters the evaporator  38  via return line  60 R and exits the evaporator  38  via supply line  60 S. The evaporator  38  may reduce the temperature of the cooling fluid in the tube bundle  58  via thermal 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 returns to the compressor  32  by a suction line to complete the cycle. 
       FIG. 4  is a schematic of the vapor compression system  14  with an intermediate circuit  64  incorporated between condenser  34  and the expansion device  36 . The intermediate circuit  64  may have an inlet line  68  that is directly fluidly connected to the condenser  34 . In other embodiments, the inlet line  68  may be indirectly fluidly coupled to the condenser  34 . As shown in the illustrated embodiment of  FIG. 4 , the inlet line  68  includes a first expansion device  66  positioned upstream of an intermediate vessel  70 . In some embodiments, the intermediate vessel  70  may be a flash tank (e.g., a flash intercooler). In other embodiments, the intermediate vessel  70  may be configured as a heat exchanger or a “surface economizer.” In the illustrated embodiment of  FIG. 4 , the intermediate vessel  70  is used as a flash tank, and the first expansion device  66  is configured to lower the pressure of (e.g., expand) the liquid refrigerant received from the condenser  34 . During the expansion process, a portion of the liquid may vaporize, and thus, the intermediate vessel  70  may be used to separate the vapor from the liquid received from the first expansion device  66 . Additionally, the intermediate vessel  70  may provide for further expansion of the liquid refrigerant because of a pressure drop experienced by the liquid refrigerant when entering the intermediate vessel  70  (e.g., due to a rapid increase in volume experienced when entering the intermediate vessel  70 ). The vapor in the intermediate vessel  70  may be drawn by the compressor  32  through a suction line  74  of the compressor  32 . In other embodiments, the vapor in the intermediate vessel may be drawn to an intermediate stage of the compressor  32  (e.g., not the suction stage). The liquid that collects in the intermediate vessel  70  may be at a lower enthalpy than the liquid refrigerant exiting the condenser  34  because of the expansion in the expansion device  66  and/or the intermediate vessel  70 . The liquid from intermediate vessel  70  may then flow in line  72  through a second expansion device  36  to the evaporator  38 . 
     As noted above, the motor  50  used in the vapor compression system  14  of  FIGS. 1-4  may generate heat during operation and, accordingly, is generally cooled using refrigerant directed from a relatively high pressure portion of the vapor compression system  14 , such as the condenser  34 . To help illustrate,  FIG. 5  is a schematic diagram of an embodiment of a hybrid cooling system  100  that circulates refrigerant to the motor  50  to cool the motor  50 . As described above, a main refrigerant circuit  102  cyclically directs refrigerant through the compressor  32 , the condenser  34 , the expansion device  36 , and the evaporator  38 , which may be coupled in series with one another. As used herein, a high pressure side  104  of the main refrigerant circuit  102  extends between an outlet of the compressor  32  and an inlet of the expansion device  36 . The illustrated embodiment of the hybrid cooling system  100  includes a motor cooling circuit  106  (e.g., cooling refrigerant circuit), which directs refrigerant from multiple portions of the high pressure side  104  of the main refrigerant circuit  102  to cool the motor  50 . As described herein, the hybrid cooling system  100  implements a combination of refrigerant vapor and refrigerant liquid, directed through respective inlet ports into the motor  50 , to efficiently cool components (e.g., a stator, a rotor, and/or bearings) within the motor  50 . The hybrid cooling system  100  is initially discussed with reference to the refrigerant vapor being diverted to the motor cooling circuit  106  from the condenser  34 , though as will be understood, the refrigerant vapor may alternatively be diverted from a discharge of the compressor  32 , the intermediate vessel  70  discussed above, or another suitable high pressure source of the vapor compression system  14 . 
     In the illustrated embodiment, the motor cooling circuit  106  directs refrigerant vapor from a top portion  110  of the condenser  34 , along a vapor conduit  112  of the motor cooling circuit  106 , and into a housing of the motor  50 . For example, an outlet port may be formed through a shell of the condenser  34  to enable the high pressure refrigerant vapor therein to exit the shell and enter the vapor conduit  112 . Although indicated as the top portion  110  of the condenser  34 , it should be understood that the refrigerant vapor may be drawn from any suitable location from the shell of the condenser  34 . A first valve  114  (e.g., vapor control valve) may be disposed along the vapor conduit  112  downstream of the condenser  34  with respect to the flow of refrigerant along the vapor conduit  112 . The first valve  114  operates to adjust an amount of the refrigerant vapor that is directed along the motor cooling circuit  106  from the condenser  34  to the motor  50 . 
     Additionally, to supplement the refrigerant vapor, the motor cooling circuit  106  directs a portion of the refrigerant liquid exiting the condenser  34  to the housing of the motor  50 . For example, a first tee  120  (e.g., three-way valve) may divert a portion of the refrigerant liquid from the main refrigerant circuit  102  to a liquid conduit  122  of the motor cooling circuit  106 . Additionally, a second valve  124  (e.g., liquid control valve) may be disposed along the liquid conduit  122  downstream of the condenser  34  with respect to the flow of refrigerant along the liquid conduit  122 . The liquid conduit  122  of the present embodiment includes a single conduit inlet and two conduit outlets. It should be understood that any suitable control device (e.g., valve) may be included along the liquid conduit  122  to enable the hybrid cooling system  100  to control the relative flows of refrigerant liquid out of the two conduit outlets. Indeed, in other embodiments, the second valve  124  may be replaced with two valves, which are each designed to control refrigerant liquid flow from a respective conduit outlet of the liquid conduit  122 . 
     The valves  114 ,  124  may each be any suitable valve that passively or actively controls the refrigerant flow therethrough, such as a fixed-orifice valve, a variable-orifice valve, a ball valve, a butterfly valve, a gate valve, a globe valve, a diaphragm valve, and/or another suitable valve. In some embodiments, one or both of the valves  114 ,  124  are coupled to the control panel  40 , hereinafter referred to as a controller  40 . The controller  40  may adjust a respective position of the valves  114 ,  124  to control flows of the refrigerant through the conduits  112 ,  122  of the motor cooling circuit  106 , such as based on a temperature of the motor  50  monitored by a sensor  126  (e.g., temperature sensor), for example. The controller  40  of the hybrid cooling system  100  may individually adjust flows of the refrigerant vapor relative to the refrigerant liquid, in some embodiments. For example, the controller  40  may increase the flow of the refrigerant vapor relative to the flow of the refrigerant liquid (e.g., via adjusting the valves  114 ,  124 ) in response to determining that the temperature of the motor  50  is below a predefined threshold, thereby increasing the temperature of the motor  50 . Alternatively, the controller  40  may decrease the flow of the refrigerant vapor relative to the flow of the refrigerant liquid in response to determining that the temperature of the motor is above a predefined threshold. In some embodiments, the valves  114 ,  124  may be manually controlled based on expected or scheduled operation of the vapor compression system  14 . Alternatively, one or both of the valves  114 ,  124  may be omitted in situations in which the respective conduits  112 ,  122  have a size (e.g., diameter, fixed orifice size) suitable for regulating the flow of refrigerant along the motor cooling circuit  106  based on operation of the vapor compression system  14 . 
     As discussed below, the hybrid cooling system  100  therefore directs the refrigerant liquid into the housing of the motor  50  via two liquid inlet ports  130  and, further, directs the refrigerant vapor into the housing of the motor  50  via a vapor inlet port  132 . In some embodiments, the liquid inlet ports  130  are coupled in series with one another, such that an initial flow of refrigerant liquid is directed to an upstream one of the liquid inlet ports  130  before a subsequent flow of refrigerant liquid is directed to a downstream one of the liquid inlet ports  130 . The vapor inlet port  132  is positioned in between the liquid inlet ports  130  relative to a longitudinal axis  140  of the motor  50 , thereby enabling the single flow of refrigerant vapor to interact with both flows of the refrigerant liquid. The hybrid cooling system  100  therefore places the refrigerant flows in a heat exchange relationship with one another and any suitable components (e.g., a stator, a rotor, and/or bearings) of the motor  50 . Accordingly, the refrigerant absorbs thermal energy (e.g., heat) from the motor  50  to reduce a temperature of the motor  50 , while reducing or preventing overcooling of the housing of the motor  50 . The warmed refrigerant is then directed from the motor  50  back toward the main refrigerant circuit  102  via a return conduit  142  of the motor cooling circuit  106 , enabling the warmed refrigerant to flow into the evaporator  38 . In some embodiments, the return conduit  142  is coupled to the main refrigerant circuit  102  via a second tee  144  or three-way valve, though any other suitable connection device may be utilized. As noted herein, the motor cooling circuit  106  therefore includes three connection points to the main refrigerant circuit: a refrigerant vapor inlet  150  (corresponding to the top portion  110  of the condenser  34 ), a refrigerant liquid inlet  152  (corresponding to the first tee  120 ), and a refrigerant outlet  154  (corresponding to the second tee  144 ). 
     In some embodiments, the motor cooling circuit  106  includes a flow generating device, such as a pump, an eductor, a compressor, or another suitable device that facilitates respective flows of the refrigerant through the motor cooling circuit  106 . In other embodiments, the refrigerant travels through the respective conduits  112 ,  122  of the motor cooling circuit  106  via a pressure differential between the refrigerant upstream of the motor  50  and downstream of the motor  50 . For example, a pressure of the refrigerant vapor diverted from the top portion  110  of the condenser and/or a pressure of the refrigerant exiting the condenser  34  may be greater than the pressure of the refrigerant entering the evaporator  38  because of a pressure drop caused by the expansion device  36 . 
       FIG. 6  is a schematic diagram of another embodiment of the hybrid cooling system  100 , which receives refrigerant vapor from a compressor discharge portion  170  of the vapor compression system  14 . In the illustrated example, the motor cooling circuit  106  includes a third tee  172  that diverts a portion of the refrigerant vapor that exits the compressor  32 . Additionally, the vapor conduit  112  extends between the third tee  172  and the vapor inlet port  132  of the housing of the motor  50 . The first valve  114  may be disposed along the vapor conduit  112  to enable the controller  40  to adjust the flow of the refrigerant vapor along the vapor conduit  112 . The refrigerant vapor may therefore cool the motor  50  in conjunction with the refrigerant liquid from the condenser  34 , as discussed above. As such, the connection points from the main refrigerant circuit  102  to the motor cooling circuit  106  include the third tee  172  as the refrigerant vapor inlet  150 , the first tee  120  as the refrigerant liquid inlet  152 , and the second tee  144  as the refrigerant outlet  154 . 
     In other embodiments, the hybrid cooling system  100  may divert refrigerant vapor from a housing of the compressor  32 , such as via a suitably-positioned outlet port formed within the housing of the compressor  32 . Moreover, it should be understood that the refrigerant vapor may be directed to the housing of the motor  50  from any other suitable, high pressure portion of the main refrigerant circuit  102  (e.g., extending between the compressor  32  and the expansion device  36  relative to a refrigerant flow direction). Indeed, returning briefly to  FIG. 4 , the motor cooling circuit  106  may divert refrigerant vapor to the motor  50  from the intermediate vessel  70 , which may correspond to a flash tank economizer. In such embodiments, any suitable tees and/or control valves may be included within the hybrid cooling system  100  to enable control of the refrigerant vapor. Additionally, it should be understood that the refrigerant vapor may be provided from two or more of the condenser  34 , the compressor  32 , and/or the intermediate vessel  70 . For example, refrigerant vapor from each of the condenser  34 , the compressor  32 , and the intermediate vessel  70  may be directed along a common vapor conduit that is provided to the motor  50 . Additionally or alternatively, the controller  40  may operate any suitable control valves to enable the refrigerant vapor to be provided to the motor  50  from a first high pressure vapor source during a first time period and from a second high pressure vapor source during a different, second time period. 
     With the above general operation of the hybrid cooling system  100  in mind, further discussion is provided regarding the motor  50  having the hybrid cooling system  100  that directs both refrigerant vapor and refrigerant liquid therethrough.  FIG. 7  is a cross-sectional side view of the motor  50  having the hybrid cooling system  100 , illustrating refrigerant flow paths in the motor cooling circuit  106  through the motor  50 . As shown in the illustrated embodiment of  FIG. 7 , the motor  50  includes a housing  200 , as well as a stator  202 , a rotor  204  coupled to a shaft  206 , a sleeve  210 , and bearings (e.g., ball bearings, sleeve bearings, magnetic bearings, other suitable bearings) disposed in the housing  200 . The stator  202  of the motor  50  may be disposed within the sleeve  210 , such that the sleeve  210  circumferentially surrounds at least a portion of a radially outward surface  212  of the stator  202  (e.g., relative to a circumferential axis  214  around the longitudinal axis  140  of the motor  50 ). In some embodiments, the sleeve  210  is formed from a metallic material, such as an aluminum or non-magnetic metal that reduces interference between the sleeve  210  and the electromagnetic field produced between the rotor  204  and the stator  202  as the rotor  204  rotates within the stator  202 . In other embodiments, the housing  200  and the stator  202  may be formed in a way that enables the sleeve  210  to be omitted from the motor  50 . 
     In the present embodiment, an annular cavity  220  (e.g., heating jacket, cooling jacket, vapor cooling jacket) is formed between the housing  200  and the sleeve  210 . The annular cavity  220  may be a defined volume that extends circumferentially between the sleeve  210  and the housing  200 , such that the annular cavity  220  is adjacent to both the housing  200  and the sleeve  210 . As recognized herein, the vapor inlet port  132  is coupled between the vapor conduit  112  and the annular cavity  220 , enabling the hybrid cooling system  100  to direct a refrigerant vapor flow  222  (e.g., vapor flow) into the housing  200  and into the annular cavity  220  to cool the housing  200 , the sleeve  210 , and the stator  202  of the motor  50 . As discussed above, the refrigerant vapor flow  222  supplied to the housing  200  may be refrigerant vapor diverted from the condenser  34 , the compressor  32 , and/or the intermediate vessel  70  discussed above with respect to  FIG. 4 . 
     In some embodiments, the annular cavity  220  extends around a full circumference of the sleeve  210 , which enables the refrigerant vapor flow  222  to transfer heat between the housing  200  and the full circumference of the sleeve  210 . The annular cavity  220  is fluidly coupled to an upstream end  224  of a vent slot  226  that extends radially (e.g., along radial axis  230 ) through a central portion  232  of the stator  202 , such as a lamination stack of the stator  202 . For example, any suitable number of openings (e.g., drilled holes, radial openings) may be formed within the sleeve  210  to enable the annular cavity  220  to fluidly couple to the vent slot  226 . In some embodiments, each radial opening of the sleeve  210  may be radially centered or aligned with a corresponding vent slot  226  of multiple vent slots  226  to enable the refrigerant vapor flow  222  to enter the multiple vent slots  226 . In any case, a downstream end  234  of the one or multiple vent slots  226  may be fluidly coupled to a gap  240  (e.g., air gap, annular gap) formed between the stator  202  and the rotor  204 . 
     As such, the hybrid cooling system  100  includes a vapor flow path  242  through the housing  200  that enables the refrigerant vapor flow  222  to fill the annular cavity  220 , travel along the vent slot  226 , and travel into the gap  240 . The refrigerant vapor flow  222  may therefore absorbs thermal energy from the housing  200 , the stator  202  and the rotor  204 . The vent slot  226  thus enables the refrigerant vapor flow  222  to maintain a temperature of components within the housing  200 , which may further enhance an efficiency of the motor  50 . The vapor flow path  242  extends from the gap  240  to a first cavity  250  (e.g., downstream cavity relative to a refrigerant flow direction  252 ) in the housing  200 , which directs the refrigerant vapor flow  222  toward a vent  254  out of the housing  200  and toward the evaporator  38 . As the refrigerant flows from the stator  202  along an exit path toward the vent  254 , the refrigerant vapor flow  222  (and/or the evaporated refrigerant vapor flows discussed below) may also contact and absorb heat from the rotor  204  and/or bearings in the housing  200 . 
     Additionally, because the refrigerant vapor flow  222  fills the annular cavity  220  in contact with the housing  200 , the refrigerant vapor flow  222  efficiently maintains a target temperature range of the housing  200 , with a reduced potential (e.g., relative to liquid refrigerant cooling) for lowering the temperature of the housing  200  below a dew point that may lead to external condensation generation. That is, the refrigerant vapor flow  222  within the annular cavity  220  may operate as a warming or heating jacket that raises the temperature of the housing  200  in certain conditions above a dew point that would otherwise enable condensation formation on an exterior surface  256  of the housing  200 . Moreover, compared to cooling systems that may direct a refrigerant liquid along a vent slot, the presently disclosed hybrid cooling system  100  provides a higher flow rate of refrigerant vapor along the gap  240 , thereby providing more efficient cooling with reduced stagnation, reduced air-gap windage loss, and improved temperature distribution. Further, the refrigerant vapor flow  222  traveling along the vapor flow path  242  may augment (e.g., supplement) flows of evaporated or flashed refrigerant liquid provided from the second liquid inlet port  262  and through the gap  240  to enable targeted cooling, without overcooling that may lead to condensation of the housing  200 , as discussed herein. As noted above, the refrigerant vapor flow  222  may be provided from the condenser  34 , the compressor  32 , and/or the intermediate vessel  70 . 
     Indeed, as illustrated, the hybrid cooling system  100  may direct refrigerant liquid, such as refrigerant liquid from the condenser  34 , into the housing  200  through a first liquid inlet port  260  and/or the second liquid inlet port  262  of the liquid inlet ports  130 . As mentioned, the liquid inlet ports  130  are formed through the housing  200  on either lateral side of the vapor inlet port  132  (e.g., relative to the longitudinal axis  140 ), such that the refrigerant vapor flow  222  interacts or mixes with vaporized flows of the refrigerant liquid provided through both liquid inlet ports  130 . In some embodiments, the first liquid inlet port  260  directs a first refrigerant liquid flow  264  (e.g., first liquid flow) into a first annulus  266 , which surrounds the stator  202  at a first end  270  of the motor  50  (e.g., an opposite drive end, corresponding to first axial end of stator  202 ). Similarly, the second liquid inlet port  262  directs a second refrigerant liquid flow  274  (e.g., second liquid flow) into a second annulus  276  that surrounds the stator  202  at a second end  278  of the motor  50  (e.g., a drive end, corresponding to second axial end of stator  202 ). In some embodiments, the annuli  266 ,  276  may be formed within the housing  200  adjacent to the sleeve  210 , such that the annuli  266 ,  276  at least partially surround the sleeve  210  and the stator  202 . For example, the annuli  266 ,  276  may be positioned at locations along a length of the motor  50  corresponding to the liquid inlet ports  260 ,  262 , which may be respectively positioned at the first end  270  (e.g., the opposite drive end, first axial end) of the motor  50  and the second end  272  (e.g., the drive end, second axial end) of the motor  50 . 
     In some embodiments, the refrigerant liquid flows  264 ,  274  are provided to the housing  200  in series, such that the second refrigerant liquid flow  274  is directed or provided to the housing  200  and fills the second annulus  276 . Thereafter, because the second annulus  276  is generally filled, the hybrid cooling system  100  may direct or provide the first refrigerant liquid flow  264  to the first annulus  266 . In other embodiments, the refrigerant liquid flows  264 ,  274  may be provided to the housing  200  in parallel. In either case, after respectively filling the annuli  266 ,  276 , the refrigerant liquid flows  264 ,  274  may then be continuously discharged through openings circumferentially spaced about each of the annuli  266 ,  276 , such that the refrigerant liquid flows  264 ,  274  travel radially inward from the openings of the annuli  266 ,  276  and come into contact with windings of the stator  202 . It should be understood that, as the refrigerant liquid flows  264 ,  274  pass through the openings, the hybrid cooling system  100  may continuously fill the annuli  266 ,  276  to enable continuous cooling. In some embodiments, the first refrigerant liquid flow  264  discharged from the first annulus  266  may absorb significant heat from the stator  202  and transform into a first evaporated refrigerant vapor flow  280  (e.g., first evaporated vapor flow, flow initially provided to housing  200  as liquid), which flows through the first cavity  250  of the housing  200 . The first evaporated refrigerant vapor flow  280  may therefore mix with the refrigerant vapor flow  222  within the first cavity  250  before being discharged back toward the main refrigerant circuit  102 . Accordingly, the first evaporated refrigerant vapor flow  280  may join the refrigerant vapor flow  222  and travel from the first cavity  250  and to the evaporator  38 . 
     Additionally, the second refrigerant liquid flow  274  discharged from the second annulus  276  may similarly absorb significant heat from the stator  202  and transform into a second evaporated refrigerant vapor flow  282  (e.g., second evaporated vapor flow, flow initially provided to housing  200  as liquid). The second evaporated refrigerant vapor flow  282  may travel through a second cavity  284  of the housing  200  (e.g., upstream cavity, upstream portion of main cavity defined by first cavity  250  and second cavity  284 ) and toward an upstream end of the gap  240 . All or a portion of the second evaporated refrigerant vapor flow  282  may therefore travel along a full length  290  of the gap  240 , along the longitudinal axis  140 , to mix with the refrigerant vapor flow  222  within the gap  240 . In other words, the second evaporated refrigerant vapor flow  282  may traverse the full length  290  of the gap, while the refrigerant vapor flow  222  traverses a partial length  292  of the gap  240  that is defined between the vent slot  226  and the downstream end of the gap  240 . Because the refrigerant vapor flow  222  enters the gap  240  from the vent slot  226  that is between the upstream end and the downstream end of the gap  240 , the refrigerant vapor flow  222  may augment the second evaporated refrigerant vapor flow  282 , while equalizing a temperature distribution between the rotor  204  and the stator  202 . Then, the second evaporated refrigerant vapor flow  282  may travel with the first evaporated refrigerant vapor flow  280  and the refrigerant vapor flow  222  through the first cavity  250  and out of the vent  254 . 
     Indeed, because the refrigerant liquid flows  264 ,  274  may be vaporized by the thermal energy absorbed from portions of the motor  50 , augmenting or supplementing the refrigerant liquid flows  264 ,  274  with the intermediately-supplied refrigerant vapor flow  222  may stabilize the temperature of the rotor  204  and the stator  202 , blocking potential overcooling or formation of cold spots within the motor  50 . The hybrid cooling system  100  may also alleviate demand for an inclusion of a drain in the housing  200  that enables unevaporated portions of the refrigerant liquid flows  264 ,  274  to return to the main refrigerant circuit  102 , thereby reducing a complexity of the motor  50 . Moreover, compared to directly injecting refrigerant vapor to the gap  240 , the hybrid cooling system  100  provides the refrigerant vapor flow  222  to the gap  240  through the vent slot  226 , which is more efficient and reliable, while also integrating more naturally with the refrigerant liquid flows  264 ,  274 . 
       FIG. 8  is an expanded partial cross-sectional side view of the inlet ports  132 ,  260 ,  262  of the hybrid cooling system  100  of the motor  50 . As illustrated, the annuli  266 ,  276  are sealed between the sleeve  210  and a surface  300  of the housing  200  using seals  302  (e.g., O-rings, silicone, sealant). As such, the refrigerant liquid flows  264 ,  274  may be blocked from leaking into the cavities  250 ,  284  or the annular cavity  220  before flowing into the respective annuli  266 ,  276  from the respective liquid inlet ports  260 ,  262 . As discussed above, the annuli  266 ,  276  may each include a number of openings  308 , which are defined though a main body  309  of the sleeve  210 . The openings  308  may be spaced about the annuli  266 ,  276  to direct the refrigerant liquid flows  264 ,  274  toward the stator  202  and absorb heat therefrom. 
     Additionally, the vapor inlet port  132  is coupled to the annular cavity  220 , which extends between the housing  200  and the sleeve  210 . The vapor inlet port  132  may have any suitable size for enabling the refrigerant vapor flow  222  to enter the housing  200 . For example, in some embodiments, the vapor inlet port  132  has a diameter  310  that is larger than a diameter  312  of the liquid inlet ports  130  to enable the refrigerant vapor flow  222  to travel therethrough. A number of openings  314  (e.g., radial openings, radial holes) may be formed through the main body  309  of the sleeve  210  to fluidly couple the annular cavity  220  to the vent slot  226  (or multiple vent slots  226 ) defined through the stator  202 . For example, 2, 3, 4, 5, 10, 20, or more openings  314  and corresponding vent slots  226  may be formed through the sleeve  210  and stator  202 . In other embodiments, the hybrid cooling system  100  may include a single opening  314  that couples the annular cavity  220  to a single vent slot  226 . In any case, the refrigerant vapor flow  222  may be selectively directed through the vent slot  226  and through the gap  240  discussed above to facilitate efficient motor cooling. 
     It should be understood that the vapor inlet port  132  may be positioned in another suitable location within the housing  200 , such as aligned with the vent slot  226 , or alternatively, on an opposite side of one of the liquid inlet ports  260 ,  262  with a fluid conduit connecting the vapor inlet port  132  to the annular cavity  220 . Additionally, the annular cavity  220  may include any suitable shape, such as one with right angles in place of the illustrated smooth edges  320 . Additionally, the annular cavity  220  may include a central height  322  (e.g., radial height) above the vent slot  226  that is different than, instead of equal to, a distal height  324  at edge portions  326  of the annular cavity  220 , in other embodiments. 
     As set forth above, the present disclosure may provide one or more technical effects useful in the cooling of a hermetic motor, such as the motor  50  that drives operation of the compressor  32  of the vapor compression system  14 . Embodiments of the disclosure may include a hybrid cooling system  100  that directs a refrigerant vapor flow  222  to an annular cavity  220  that is defined between a housing  200  of the motor  50  and a sleeve  210  that surrounds a stator  202  of the motor  50 . The refrigerant vapor flow  222  may travel radially through openings  314  in the sleeve  210  to access a vent slot  226  defined through the stator  202 . Then, the refrigerant vapor flow  222  may travel longitudinally along a gap  240  defined between the stator  202  and a rotor  204  of the motor. Moreover, the hybrid cooling system  100  may direct refrigerant liquid flows  264 ,  274  to respective annuli  266 ,  276  defined between the housing  200  and the motor  50 , axially surrounding the annular cavity  220 . The refrigerant liquid flows  264 ,  274  may be evaporated by heat transferred from the stator  202 , generating respective evaporated refrigerant vapor flows  280 ,  282  that traverse cavities  250 ,  284  within the housing  200 , while being augmented by the refrigerant vapor flow  222  therein. Therefore, the hybrid cooling system  100  enables reduced temperatures of the rotor  204  and more uniform temperature distributions throughout the stator  202 , while maintaining the housing  200  of the motor  50  at a temperature above a dew point to block condensation formation. The technical effects and technical problems in the specification are examples and are not limiting. It should be noted that the embodiments described in the specification may have other technical effects and can solve other technical problems. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     While only certain features and embodiments have been illustrated and described, many modifications and changes may occur to those skilled in the art (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters (e.g., temperatures, pressures), mounting arrangements, use of materials, colors, orientations) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the disclosure. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described (i.e., those unrelated to the presently contemplated best mode of carrying out the disclosure, or those unrelated to enabling the claimed disclosure). It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.