Lubricant circulation system for a compressor

Abstract

A heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system (100) includes a compressor (104), a sensor system (177), where the sensor system includes one or more sensors (178) configured to detect one or more operating parameters, and a lubricant circulation system (108) configured to supply lubricant (112) to the compressor (104). The lubricant circulation system (108) includes a lubricant circuit (132) configured to circulate the lubricant (112), a lubricant heat exchanger (124) disposed on the lubricant circuit (132) and configured to heat the lubricant (112), and a controller (136) communicatively coupled to the compressor (104) and the lubricant circulation system (108), where the controller (136) is configured to control the lubrication circulation system (108) to heat the lubricant (112) via the lubricant heat exchanger (124) in response to determining the compressor (104) is in a non-operational state based on the one or more operating parameters.

Description

LUBRICANT CIRCULATION SYSTEM FOR A COMPRESSORCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from and the benefit of U.S. Provisional Patent Application No. 63 / 700,437, entitled “OIL CIRCULATION SYSTEM FOR A STANDSTILL COMPRESSOR,” filed September 27, 2024, which is hereby incorporated by reference in its entirety for all purposes.BACKGROUND

[0002] 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.

[0003] Heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems, such as vapor compression systems, utilize a working fluid (e.g., refrigerant) that changes phases between vapor, liquid, and combinations thereof in response to exposure to different temperatures and pressures within components of the HVAC&R system. The HVAC&R system may include a working fluid circuit configured to place the working fluid in a heat exchange relationship with a conditioning fluid (e.g., water), and may deliver the conditioning fluid to conditioning equipment and / or a conditioned environment serviced by the HVAC&R system. For example, the HVAC&R system may include a heat exchanger configured to receive the working fluid and the conditioning fluid to place the working fluid in the heat exchange relationship with the conditioning fluid. The conditioning fluid may be directed from the heat exchanger to other equipment, such as air handlers, to condition other fluids, such as air in a building. The HVAC&R system may also include other components, such as a compressor configured to pressurize the working fluid and direct the working fluid through the HVAC&R system. Many other applications exist for HVAC&R systems.

[0004] Certain compressors employed in certain HVAC&R systems may be lubricated by a fluid (e.g., lubricating fluid), such as an oil, to reduce friction caused by moving parts of the compressor, reduce wear and degradation on the compressor, and / or dissipate heat generated by the compressor. Additionally or alternatively, the fluid may be used to seal certain aspects of the compressor and / or for purposes of temperature control. However, when the compressor is non-operational, circulation of fluid into the compressor may be suspended, which can have undesirable results. In certain circumstances, low ambient temperature operating conditions (e.g., freezing conditions) may result in condensation and associated undesirable effects in compressors. Accordingly, there is a need for a system and a method to alleviate condensation risk in a non-operational compressor.SUMMARY

[0005] A summary of certain embodiments disclosed herein is set forth below. It should be noted 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.

[0006] In an embodiment, a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system includes a compressor, a sensor system, where the sensor system includes one or more sensors configured to detect one or more operating parameters, and a lubricant circulation system configured to supply lubricant to the compressor. The lubricant circulation system includes a lubricant circuit configured to circulate the lubricant, a lubricant heat exchanger disposed on the lubricant circuit and configured to heat the lubricant, and a controller communicatively coupled to the compressor and the lubricant circulation system, where the controller is configured to control the lubrication circulation system to heat the lubricant via the lubricant heat exchanger in response to determining the compressor is in a non-operational state based on the one or more operating parameters.

[0007] In an embodiment, a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system includes a compressor having a slide valve system. The slide valve system includes a slide valve cavity and a slide valve configured totransition within the slide valve cavity between a first position and a second position. The compressor also includes a drain fluidly coupling the slide valve cavity to a drain conduit via an opening formed by the slide valve in the second position. The system also includes a lubricant circulation system configured to supply lubricant to the compressor, where the lubricant circulation system includes a heat source configured to heat the lubricant, a sensor system including one or more sensors configured to monitor a temperature, and a controller communicatively coupled to the heat source and the sensor system, where the controller is configured to operate the heat source in response to determining the compressor is in a non-operational state and the temperature is less than a threshold temperature.

[0008] In an embodiment, a method for lubricant circulation within a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system includes receiving data indicative of an ambient temperature, determining whether a compressor of an HVAC&R system is in a non-operating state, in response to determining the ambient temperature is less than a threshold temperature and the compressor is in the non-operating state, circulating lubricant into the compressor from a lubricant circuit, where circulating the lubricant includes operating a pump to bias the lubricant through the lubricant circuit, heating the lubricant via a lubricant heat exchanger, draining a mixture of lubricant and working fluid from the compressor, where the mixture is directed into a lubricant separator via a discharge conduit, separating the mixture into lubricant and working fluid in the lubricant separator, and directing the lubricant separated from the mixture in the lubricant separator into the lubricant heat exchanger.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which:

[0010] FIG. 1 is a perspective view of a building utilizing an embodiment of a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system in a commercial setting, in accordance with an aspect of the present disclosure;

[0011] FIG. 2 is a perspective view of an embodiment of a vapor compression system, in accordance with an aspect of the present disclosure;

[0012] FIG. 3 is a schematic of an embodiment of a vapor compression system, in accordance with an aspect of the present disclosure;

[0013] FIG. 4 is a schematic of an embodiment of a vapor compression system, in accordance with an aspect of the present disclosure;

[0014] FIG. 5 is a schematic view of an embodiment of a lubricant circulation system, in accordance with an aspect of the present disclosure; and

[0015] FIG. 6 is a process diagram for an embodiment of a method that may be followed by the lubricant circulation system, in accordance with an aspect of the present disclosure.DETAILED DESCRIPTION

[0016] One or more specific embodiments of the present disclosure will be described below. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be 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 implementationspecific decisions must be made to achieve the developers’ specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture forthose of ordinary skill having the benefit of this disclosure.

[0017] 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.

[0018] As used herein, the terms “approximately,” “generally,” and “substantially,” and so forth, are intended to convey that the property value being described may be within a relatively small range of the property value, as those of ordinary skill would understand. For example, when a property value is described as being “approximately” equal to (or, for example, “substantially similar” to) a given value, this is intended to mean that the property value may be within + / - 5%, within + / - 4%, within + / - 3%, within + / - 2%, within + / - 1%, or even closer, of the given value. Similarly, when a given feature is described as being “substantially parallel” to another feature, “generally perpendicular” to another feature, and so forth, this is intended to mean that the given feature is within + / - 5%, within + / - 4%, within + / - 3%, within + / - 2%, within + / - 1%, or even closer, to having the described nature, such as being parallel to another feature, being perpendicular to another feature, and so forth. Further, it should be understood that mathematical terms, such as “planar,” “slope,” “perpendicular,” “parallel,” and so forth are intended to encompass features of surfaces or elements as understood to one of ordinary skill in the relevant art, and should not be rigidly interpreted as might be understood in the mathematical arts. For example, a “planar” surface is intended to encompass a surface that is machined, molded, or otherwise formed to be substantially flat or smooth (within related tolerances) using techniques and tools available to one of ordinary skill in the art. Similarly, a surface having a “slope” is intended to encompass a surface that is machined, molded, or otherwise formed to be oriented at an angle (e.g., incline) with respect to a point of reference using techniques and tools available to one of ordinary skill in the art.

[0019] The present disclosure is directed to heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) systems. More particularly, the present disclosure is directed to a lubricant circulation system configured to supply a lubricant (e.g., oil, fluid) to a compressor of the HVAC&R system, for example, to lubricate and / or seal portions of the compressor. The lubricant circulation system may also be configured to heat the supply of lubricant before entering the compressor, enabling thermal energy transfer to working fluid therein.

[0020] The HVAC&R system may enable control and / or adjustment of ventilation, air quality, and / or temperature in a condition space, for example, in a commercial or residential building. The HVAC&R system may circulate a working fluid, also referredto as a refrigerant, through a closed loop including a compressor, a condenser, an expansion device, and an evaporator. Refrigerant in the evaporator, for example, may be utilized to cool an air flow via thermal (e.g., heat) exchange to provide cooling to the conditioned space.

[0021] In accordance with the present disclosure, the lubricant circulation system may include a lubricant drain, a lubricant separator, a lubricant pump, a lubricant heat exchanger and an associated heat source, a lubricant fdter, and a controller. The lubricant circulation system may be configured to provide a heated flow of lubricant to the compressor during a stalled, suspended, or otherwise non-operational state or mode of the compressor to reduce or block condensation of working fluid within the compressor. As will be appreciated, condensation within the compressor may result in damage to components of the compressor upon startup, leading to mechanical, chemical, and / or electrical issues. As such, the heated flow of lubricant directed into the compressor during the stalled or suspended state of the compressor may not only lubricate and seal the components of the compressor but may also raise a temperature of the working fluid within (e.g., to a temperature that a corresponding working fluid (e.g., ammonia) may not condense at a certain pressure). Moreover, by lubricating the compressor before operating (e.g., during the stalled or suspended state) a start-up time of the compressor may be reduced. Compared to traditional heating systems (e.g., systems aimed to reduce condensate), such as systems employing heat tracing using electric heaters within the HVAC&R system, the above-described features, among others, described in greater detail below with reference to the drawings, enables increased uniformity of heating, reducing “cold spots” and reducing condensation throughout the HVAC&R system (e.g., the compressor). These and other aspects of the present disclosure are described in greater detail below with reference to the drawings.

[0022] Turning now to the drawings, FIG. l is a perspective view of an embodiment of an environment for a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system 10 in a building 12 for a typical commercial setting. The HVAC&R system 10 may include a vapor compression system 14 (e.g., a heat pump system, a chiller system) that supplies a conditioned liquid, which may be used to heat and / or cool the building 12. The HVAC&R system 10 may also include a boiler 16 tosupply 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 heated and / or chilled liquid from the vapor compression system 14, depending on the mode of operation of the HVAC&R system 10. The HVAC&R system 10 is shown with a separate air handler on each floor of building 12, but in other embodiments, the HVAC&R system 10 may include air handlers 22 and / or other components that may be shared between or among floors. Further, the HVAC&R system 10 may be implemented to provide conditioning (e.g., refrigeration, heating) in other applications, such as food and beverage refrigeration, industrial process refrigeration, district heating, and so forth. Indeed, it should be appreciated that the disclosed systems and methods may be utilized with any suitable HVAC&R system 10 that operates with a working fluid (e.g., refrigerant, ammonia, heat transfer fluid) and a process liquid (e.g., oil).

[0023] FIGS. 2 and 3 are embodiments of the vapor compression system 14 that can be used in the HVAC&R system 10. The vapor compression system 14 may circulate a working fluid (e.g., a heat transfer fluid, ammonia, 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 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.

[0024] Some examples of fluids that may be used as working fluids in the vapor compression system 14 are “natural” refrigerants, such as ammonia (NH3) (e.g., R-717), water vapor (e.g., R-718), or carbon dioxide (CO2) (e.g., R-744), hydrofluorocarbon (HFC) based refrigerants, such as R-410A, R-407, R-134a, or hydrofluoro olefin (HFO), hydrocarbon based refrigerants, or any other suitable working fluid.

[0025] 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 condenser34, 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 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.

[0026] The compressor 32 is configured to compress a working fluid vapor and deliver the vapor to the condenser 34 through a discharge passage. In some embodiments, the compressor 32 may be a screw compressor, a scroll compressor, a centrifugal compressor, or a reciprocating compressor. The working fluid vapor delivered by the compressor 32 to the condenser 34 may transfer heat to a cooling or conditioning fluid (e.g., water or air) in the condenser 34. The working fluid vapor may condense to a working fluid liquid in the condenser 34 due to thermal heat transfer with the conditioning fluid. The liquid working fluid from the condenser 34 may flow through the expansion device 36 to the evaporator 38. In the illustrated embodiment of FIG. 3, the condenser 34 is water cooled and includes a tube bundle 54 connected to a cooling tower 56, which supplies a cooling fluid to the condenser 34. However, in other embodiments or applications, the condenser 34 may receive and heat a conditioning fluid that is supplied to a load to provide heating to the load.

[0027] The liquid working fluid delivered to the evaporator 38 may absorb heat from another fluid, which may or may not be the same cooling or conditioning fluid used in the condenser 34. The liquid working fluid in the evaporator 38 may undergo a phase change from the liquid working fluid to a working fluid vapor. As shown in the illustrated embodiment of FIG. 3, the evaporator 38 may include a tube bundle 58 having a supply line 60S and a return line 60R connected to a cooling load 62. The conditioning fluid of the evaporator 38 (e.g., water, ethylene glycol, calcium chloride brine, sodium chloride brine, or any other suitable fluid) enters the evaporator 38 via return line 60R and exits the evaporator 38 via supply line 60S. The evaporator 38 may reduce the temperature of the conditioning fluid in the tube bundle 58 via thermal heattransfer with the working fluid. The tube bundle 58 in the evaporator 38 can include a plurality of tubes and / or a plurality of tube bundles. In any case, the vapor working fluid exits the evaporator 38 and returns to the compressor 32 by a suction line to complete the cycle.

[0028] 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, an economizer, etc.). 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 working fluid received from the condenser 34. During the expansion process, a portion of the liquid may vaporize, and thus, the intermediate vessel 70 may be used to separate the vapor from the liquid received from the first expansion device 66.

[0029] Additionally, the intermediate vessel 70 may provide for further expansion of the liquid working fluid due to a pressure drop experienced by the liquid working fluid when entering the intermediate vessel 70 (e.g., due to a rapid increase in volume experienced when entering the intermediate vessel 70). The vapor in the intermediate vessel 70 may be drawn by the compressor 32 through a suction line 74 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 working fluid exiting the condenser 34 due to 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.

[0030] It should be appreciated that any of the features described herein may be incorporated with the vapor compression system 14 or any other suitable HVAC&Rsystems. For example, the present techniques may be incorporated with any HVAC&R system having a process liquid system, including heat pump systems, chiller systems, and so forth. Further, as mentioned above, the present techniques may be incorporated with HVAC&R systems that utilize any suitable working fluid, such as ammonia (NH3), as a working fluid.

[0031] Any of the systems, units, and / or assemblies illustrated in FIGS. 1-4 may include a compressor and, in accordance with the present disclosure, a lubricant (e.g., oil) circulation system to the compressor. As mentioned above, the compressor 32 may be a screw compressor. In accordance with present embodiments, a lubricant may be circulated through the lubricant circulation system to the compressor 32 to facilitate operation of various components of the compressor 32, such a rotor (e.g., male rotor, female rotor, screw rotor), a bearing associated with the compressor 32, and so forth. The presently disclosed embodiments, described in greater detail below with reference to FIGS. 5 and 6, enable improved operation of a compressor in various operational states, such as a stalled or suspended state, by reducing risk of condensation within the compressor by heating working fluid to provide increased temperature uniformity.

[0032] FIG. 5 is a block diagram illustrating an embodiment of a portion of a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system 100, including a compressor 104 (e.g., the compressor 32) and a lubricant circulation system 108 (e.g., oil circulation system) configured to deliver a flow of lubricant 112 to the compressor 104 for lubrication, sealing, and / or temperature regulation. The lubricant circulation system 108 may include a lubricant drain 114 (e.g., compressor drain, outlet), a lubricant separator 116 (e.g., a lubricant separator, an oil separator), a lubricant pump 120, a lubricant heat exchanger 124, and / or a lubricant fdter 128 fluidly coupled via a lubricant circuit 132.

[0033] The lubricant circulation system 108 may also include a controller 136 communicatively coupled to one or more components of the lubricant circulation system 108 (e.g., the drain 114, the separator 116, the pump, the lubricant heat exchanger 124, the lubricant fdter 128, and so forth). In some configurations, the controller 136 may be a component of the control panel 40. Alternatively, the controller 136 may be a component of another system or subsystem of the HVAC&R system 100, the building 12, or other system. The controller 136 may be configured to controloperation of the lubricant circulation system 108, in accordance with the techniques discussed herein. The controller 136 includes processing circuitry 140, such as one or more microprocessors, which may execute software for controlling the components of the lubricant circulation system 108. The processing circuitry 140 may include multiple microprocessors, one or more “general -purpose” microprocessors, one or more specialpurpose microprocessors, and / or one or more application specific integrated circuits (ASICS), or some combination thereof. For example, the processing circuitry 140 may include one or more reduced instruction set (RISC) processors.

[0034] The controller 136 may also include a memory device 144 (e.g., a memory) that may store information, such as instructions, control software, look up tables, configuration data, etc. The memory device 144 may include a volatile memory, such as random access memory (RAM), and / or a nonvolatile memory, such as read-only memory (ROM). The memory device 144 may store a variety of information and may be used for various purposes. For example, the memory device 144 may store processor-executable instructions including firmware or software for the processing circuitry 140 to execute, such as instructions for controlling the lubricant circulation system 108. In some embodiments, the memory device 144 includes one or more tangible, non-transitory, machine-readable-media that may store machine-readable instructions for the processing circuitry 140 to execute. The memory device 144 may include ROM, flash memory, a hard drive, or any other suitable optical, magnetic, or solid-state storage medium, or a combination thereof. The memory device 144 may store data, instructions, and any other suitable data.

[0035] In general, the lubricant circulation system 108 may be configured to deliver the flow of lubricant 112 (e.g., the oil) to the compressor 104, such as to bearings of the compressor 104, a rotor and / or a motor of the compressor 104, an intake of the compressor 104, other locations of the compressor 104, or any combination thereof. Indeed, the compressor 104 may be configured to receive the flow of lubricant 112 in various operational states, such as a fully operational state, a non-operational state (e.g., stalled state, suspended state), and so forth. During the stalled or suspended state of the compressor 104, it may be desirable to continue to circulate the flow of lubricant 112 through the compressor 104, to, among other things, heat working fluid within and prevent condensation. As used herein, the stalled or suspended state of operation of thecompressor may be during an unplanned or unexpected shutdown (e.g., a power outage), during a planned or intended suspension of operation (e.g., due to cost considerations (e.g., based on a ratio of cost of electricity and a desire to heat)), and so forth. The lubricant circulation system 108 of the present disclosure may adequately heat the flow of lubricant 112 for use in the compressor 104 during both operational and non-operational states, reducing and / or preventing condensation within the compressor 104.

[0036] In operation, the lubricant circulation system 108 may circulate a flow of lubricant 112 into a lubricant inlet 148 of the compressor 104, where the lubricant inlet 148 is configured to facilitate flow of the lubricant 112 to internal components of the compressor 104, such as bearings, rotors, a slide valve, and so forth. As will be discussed in greater detail below, the flow of lubricant 112 may be heated to block or reduce condensation of working fluid within the compressor 104 during the stalled or suspended state. Indeed, circulating the flow of lubricant 112 (e.g., heated lubricant) through the compressor 104 may provide increased heating uniformity compared to traditional heating devices, such as electric heaters placed at various locations of the compressor 104. Additionally, by circulating the flow of lubricant 112 through the compressor 104 during the stalled or suspended state of the compressor 104, a start-up time of the compressor may be decreased.

[0037] After circulation through the compressor 104, the flow of lubricant 112 may be discharged from the compressor 104 via the lubricant drain 114 and / or a discharge port 152 of the compressor 104. In an embodiment, the lubricant drain 114 may be positioned at a bottom portion of the compressor 104, relative to a direction of gravity, such that the flow of lubricant 112 may be discharged via a force of gravity (e.g., without additional flow inducing components). For example, the lubricant drain 114 may be formed within or may be defined by a housing of the compressor 104 and may fluidly couple an interior of the compressor 104 to a drain conduit 156. In an embodiment, the lubricant drain 114 may fluidly couple the drain conduit 156 to a slide valve system 160 of the compressor 104. For example, the slide valve system 160 may be configured to vary a volume ratio (e.g., a compression ratio, compressing capacity) of the compressor 104 via regulating an amount of working fluid flowing through a compression portion of the compressor 104, such as by enabling bypass of the workingfluid past the compression. For instance, the slide valve system 160 may include a slide valve 164 configured to transition within a slide valve cavity 168. In some embodiments, in an extreme position (e.g., threshold position) of the slide valve 164 within the slide valve cavity 168 (e.g., the slide valve 164 set to one side of the slide valve cavity 168), the flow of lubricant 112 may be configured to discharge from the slide valve cavity 168 via the lubricant drain 114. Illustratively, in the extreme position, such as during the stalled or suspended state of the compressor 104, the slide valve 164 may expose the lubricant drain 114 (e.g., an opening) to the slide valve cavity 168, allowing lubricant 112 to drain (e.g., via a force of gravity) out of the slide valve cavity 168 through the lubricant drain 114 to the drain conduit 156.

[0038] It will be appreciated that any number of lubricant drains 114 may be included and at any of numerous suitable positions. In an embodiment, the drain conduit 156 from the lubricant drain 114 and may extend between the compressor 104 and lubricant separator 116. In an embodiment, the drain conduit 156 may merge or combine with a discharge conduit 172 extending from the discharge port 152 of the compressor 104.

[0039] In certain configurations, the drain conduit 156 may include a drain valve 176 configured to regulate the flow of lubricant 112, and in some instances, working fluid, from the lubricant drain 114. In one embodiment, the drain valve 176 may be a one-way valve, such as a check valve or a ball valve, configured to enable the flow of lubricant 112 in one direction (e.g., towards the lubricant separator 116) while substantially blocking the flow of lubricant 112 in a second direction (e.g., back towards the compressor 104). With respect to a one-way valve, the drain valve 176 may be configured to enable the flow of lubricant 112 towards the lubricant separator 116 during the stalled or suspended state of the compressor 104 while blocking the flow of lubricant 112 via the drain conduit 156 towards to the lubricant separator 116 during an operating state of the compressor 104. For example, the during the stalled or suspended state of the compressor 104, the flow of lubricant 112 through the drain conduit 156 from the compressor 104 may include a pressure high enough to overcome a threshold resistance of the drain valve 176, such as a spring force. In other words, the flow of lubricant 112 during the stalled or suspended state of the compressor 104 may apply a first force (e.g., via a first pressure or first pressure differential across the drain valve176) from the side of the compressor 104 to the drain valve 176, where the first force is greater than or equal to a threshold force associated with the drain valve 176. Thus, the lubricant is allowed to flow through the drain valve 176 toward the lubricant separator 116 from the compressor 104. Conversely, the flow of lubricant 112 during the operating state of the compressor 104 may apply a second force (e.g., via a second pressure or second pressure differential across the drain valve 176) to the drain valve 176 and the second force is less than the threshold force associated with the drain valve 176. This may be because lubricant is not flowing through the lubricant drain 114, for example, because the slide valve 164 is occluding the lubricant drain 114.

[0040] In an embodiment, the drain valve 176 may be communicatively coupled to the controller 136 and configured to regulate flow of lubricant 112 based on one or more control signals. In other words, the drain valve 176 may be a control valve, such as a solenoid valve or electronic valve. For example, the controller 136 may be configured to control operation of the drain valve 176 based on an operating state of the compressor 104, an ambient temperature, a parameter (e.g., pressure, temperature) of a fluid (e.g., the lubricant 112, the working fluid), and so forth. To this end, the lubricant circulation system 108 may include a sensor system 177 having one or more sensors 178 communicatively coupled to the controller 136 and configured to detect and / or provide feedback or data indicative of the operating state of the compressor 104, a measured temperature (e.g., a measured ambient temperature), a measured operating parameter (e.g., pressure, temperature) of a fluid (e.g., the flow of lubricant 112, the working fluid) and / or a component of the HVAC&R system 100, and so forth.

[0041] As an example, in response to determining the compressor 104 is in the stalled or suspended state and / or an ambient temperature is less than a threshold temperature, the controller 136 may be configured to actuate the drain valve 176 to an open position, draining lubricant from the compressor via the lubricant drain 114 (e.g., into the lubricant separator 116). Conversely, in response to determining the compressor 104 is in the active or operating state and / or the ambient temperature is greater than a threshold temperature, the controller 136 may be configured to actuate the drain valve 176 to a closed position, disabling flow of lubricant 112 through the drain conduit 156. Instead, lubricant may be discharged via the discharge port 152. However, in certain embodiments, the flow of lubricant 112 may drain from thedischarge port 152 into the lubricant circulation system 108 during the stalled or suspended state of the compressor 104. As such, in certain embodiments, the compressor 104 may not include a designated lubricant drain 114.

[0042] From the drain conduit 156 and / or the discharge conduit 172, a mixture of the flow of lubricant 112 and working fluid (e.g., gaseous working fluid), may be biased or directed into the lubricant separator 116 downstream of the compressor 104. The lubricant separator 116 may be configured to separate the flow of lubricant 112 from the working fluid to send the separated components to their respective circuits, a working fluid circuit 175 (e.g., including the compressor 32, the condenser 34, the expansion valve 36, the evaporator 38, the lubricant separator 116) and a lubricant circuit 132 (e.g., including the compressor 32, the lubricant drain 114, the lubricant separator 116, the lubricant pump 120, the lubricant heat exchanger 124, the lubricant filter 128). For instance, the working fluid separated from the lubricant separator 116 may be biased back to the working fluid circuit 175 via a recycle line 180 and the lubricant may be directed towards an additional component (e.g., the lubricant pump 120) of the lubricant circuit 132 The lubricant separator 116 may include any suitable type, such as a gravity separator, coalescing separator, centrifugal separator, and so forth. It should be understood that the lubricant circuit 132 may be considered to include the compressor 32 (e.g., a portion of the compressor) or pass through the compressor 32.

[0043] After separation, the flow of lubricant 112 (e.g., lubricant portion of the mixture of lubricant and working fluid) may be biased toward the lubricant heat exchanger 124 for further processing (e.g., heating, cooling). To facilitate flow of lubricant 112 within the lubricant circuit 132, such as the flow of lubricant 112 to the lubricant heat exchanger 124, one or more pumps, such as the lubricant pump 120, may be disposed along the lubricant circuit 132. In the illustrated embodiment, the lubricant pump 120 is disposed between the lubricant separator 116 and the lubricant heat exchanger 124 along the conduit 184 extending therebetween. However, the lubricant pump 120 or any number of additional pumps may be disposed at any suitable location within the lubricant circuit 132.

[0044] In some operating modes, at least one operating condition (e.g., at least one pressure condition) of the HVAC&R system 100 enables distribution of the flow oflubricant 112 (e.g., oil) to the compressor 104 without operating the lubricant pump 120. For example, as the flow of lubricant 112 is delivered to and received by the compressor 104 (e.g., the compressor 104 in an operating mode or state, not suspended), the flow of lubricant 112 may mix with a working fluid (e.g., refrigerant) being compressed by the compressor 104. Because the flow of lubricant 112 may be mixed with the working fluid in the lubricant circuit 132, a pressure of the flow of lubricant 112 may be influenced, among other possible factors, by a pressure of the working fluid. In such instances, the lubricant pump 120 may be suspended, and the flow of lubricant 112 may be biased through the lubricant circuit 132 via the pressure of the flow of lubricant 112 caused in part by the work of the compressor 104 imparted to the mixture of flow of lubricant 112 and working fluid.

[0045] To this end, in response to determining an operating state of the compressor 104, the controller 136 may be configured to control operation of the lubricant pump 120. In one example, in response to determining the compressor 104 is operating or is not suspended (e.g., in response to feedback from the compressor 104 indicative of an active operating state or pressure readings in the lubricant circuit 132) the controller 136 may be configured to suspend operation or lower the pumping capacity of the lubricant pump 120. Conversely, in response to determining the compressor 104 is in the stalled or suspended state (e.g., in response to feedback from the compressor 104 indicative of a suspended state) the controller 136 may be configured to operate the lubricant pump 120, biasing the flow of lubricant 112 through the lubricant circuit 132.

[0046] In some embodiments, one or more detected or measured parameters of the flow of lubricant 112 and / or the working fluid may be indicative of an operating mode of the compressor 104. For example, a relatively low measured pressure of the flow of lubricant 112 through the lubricant circuit 132 may be indicative of the stalled or suspended state of the compressor 104 while a relatively high measured pressure of the flow of lubricant 112 through the lubricant circuit 132 may be indicative of the active or operating state of the compressor 104. As such, in response to receiving feedback indicative of a pressure of the flow of a fluid (e.g., the flow of lubricant 112, the working fluid) the controller 136 may be configured to control operation of the lubricant pump 120. For example, in response to receiving feedback indicative of a relatively low pressure (e.g., below a threshold lubricant pressure, which may be indicative of thestalled or suspended state of the compressor 104), the controller 136 may be configured to activate operation of the lubricant pump 120. Conversely, in response to receiving feedback indicative of a relatively high pressure (e.g., above a threshold lubricant pressure, which may be indicative of the active or operating state of the compressor 104), the controller 136 may be configured to suspended operation of the lubricant pump 120. Indeed, other components of the lubricant circulation system 108 may be controlled similarly.

[0047] Further to this end, the lubricant circulation system 108 may include a bypass line 188 configured to enable bypass of the flow of lubricant 112 around the lubricant pump 120. For example, the bypass line 188 may enable the flow of lubricant 112 to bypass in scenarios where the lubricant pump 120 is in a stalled or suspended state, such as during the active operating state of the compressor 104. The bypass line 188 may include a bypass valve 192 (e.g., electric expansion valve, solenoid valve) configured to regulate the flow of lubricant 112 through the bypass line 188. For example, the bypass valve 192 may be selectively actuated between an open position, to enable the flow of lubricant 112 through the bypass line 188, and a closed position, to disable or block the flow of lubricant 112 through the bypass line 188. Indeed, the actuation of the bypass valve 192 may be based on the operating state of the compressor 104, a parameter of fluid (e.g., lubricant flow), the operating state of the lubricant pump 120, and so forth. For example, in response to determining the compressor 104 is in the active or operating state, the controller 136 may be configured to actuate the bypass valve 192 to the open position, enabling bypass of the flow of lubricant 112 around the lubricant pump 120. Conversely, in response to determining the compressor 104 is in the stalled or suspended operating state, the controller 136 may be configured to actuate the bypass valve 192 to the closed position, blocking bypass of the flow of lubricant 112 past the lubricant pump 120.

[0048] In one embodiment, the bypass valve 192 may be a one-way valve, such as a check valve or a ball valve, configured to enable the flow of lubricant 112 in one direction (e.g., towards the lubricant heat exchanger 124) while substantially blocking the flow of lubricant 112 in a second direction (e.g., back towards the lubricant separator 116). With respect to a one-way valve, the bypass valve 192 may be configured to enable the flow of lubricant 112 towards the lubricant heat exchanger 124via the bypass line 188 (e.g., bypassing the lubricant pump 120) during the operating state of the compressor 104 while blocking the flow of lubricant 112 through the bypass line 188 during the stalled or suspended state of the compressor 104.

[0049] As discussed above, the lubricant circulation system 108 may include the lubricant heat exchanger 124 (e.g., lubricant heater, lubricant cooler) configured to thermally regulate the flow of lubricant 112. Indeed, as discussed above, heated lubricant may reduce condensation within the compressor 104.

[0050] In some embodiments, the lubricant heat exchanger 124 may be configured to heat the flow of lubricant 112 prior to the flow of lubricant 112 being directed into the compressor 104. As will be appreciated, during the stalled or suspended state of the compressor 104 and / or during certain ambient temperature conditions (e.g., low ambient temperature conditions), working fluid within the compressor 104 may condense to a liquid form. Liquid working fluid within the compressor 104 may result in damage and degradation to one or more components of the compressor 104, such as upon start-up. As such, by directing a heated flow of lubricant 112 into the compressor 104, via the lubricant circuit 132, the working fluid within may be thermally regulated, reducing or blocking condensation. Additionally, by circulating lubricant through the compressor 104 during the stalled or suspended state, the compressor 104 may experience a faster start-up sequence.

[0051] The lubricant heat exchanger 124 may include any suitable type, such as a fluid heat exchanger (e.g., shell and tube heat exchanger, plate heat exchanger, etc.), an electric heater, a boiler, and so forth. In embodiments including a fluid heat exchanger, a conditioning fluid (e.g., heated fluid, water) may be placed in a heat exchanging relationship with the flow of lubricant 112 within the lubricant heat exchanger 124. For example, a heat source 196 may be configured to heat a flow of conditioning fluid (e.g., heated water) entering into a tube bundle 200 of the lubricant heat exchanger 124 via a supply line or conduit 204. The conditioning fluid (e.g., heated water) may be placed in a heat exchanging relationship with the flow of lubricant 112 through the lubricant heat exchanger 124 to heat the flow of lubricant 112. For example, the flow of lubricant 112 may be directed across the tube bundle 200 including the flow of the conditioning fluid (e.g., heated conditioning fluid), enabling transfer of thermal energy from the heated conditioning fluid to the flow of lubricant 112. After thermal energy transferwithin the lubricant heat exchanger 124, the conditioning fluid (e.g., now cooled conditioning fluid) may be directed back to the heat source 196 via a return line 208 for reheating.

[0052] In an embodiment, the heat source 196 may be a boiler, an electric heater, an additional fluid heat exchanger, or any other suitable source. In some embodiments, the lubricant heat exchanger 124, the heat source 196, or both may be a component of a heat pump including a working fluid circuit (e.g., second working fluid circuit) having a compressor (e.g., second compressor), a first heat exchanger (e.g., second condenser), a second heat exchanger (e.g., second evaporator), and an expansion device (e.g., electronic expansion valve). In an embodiment, the heat source 196 may be internal to the lubricant heat exchanger 124. For example, the lubricant heat exchanger 124 may be a submersion heater configured to submerge one or more heating elements within the flow of lubricant 112.

[0053] In certain configurations, the lubricant heat exchanger 124 may be configured to regulate a temperature of the flow of lubricant 112 during operation of the compressor 104. For example, during operation of the compressor 104, the lubricant heat exchanger 124 may be configured to cool the flow of lubricant 112 prior to direction into the compressor 104. Specifically, the lubricant heat exchanger 124 may be configured to receive conditioning fluid (e.g., cooled conditioning fluid) within the tube bundle 200, where then the conditioning fluid may receive thermal energy from the flow of lubricant 112, cooling the flow of lubricant 112. In other words, the same lubricant heat exchanger 124 may be operable to heat the flow of lubricant 112 during the stalled or suspended operation of the compressor 104 and may also be configured to cool the flow of lubricant 112 during operation of the compressor 104.

[0054] The controller 136 may be configured to activate, suspend, adjust, or otherwise control operation of the lubricant heat exchanger 124 and / or the heat source 196 to regulate a temperature of the flow of lubricant 112. For example, the controller 136 may be configured to control operation of the lubricant heat exchanger 124 and / or the heat source 196 based on an operating state of the compressor 104, an ambient temperature, a parameter (e.g., pressure, temperature) of a fluid (e.g., the flow of lubricant 112, the working fluid), and so forth. This may include bypassing thelubricant heat exchanger 124 in certain embodiments (e.g., via a bypass conduit with a control valve).

[0055] As an example, in response to determining the compressor 104 is in the stalled or suspended state, the controller 136 may be configured to activate the lubricant heat exchanger 124 and / or the heat source 196 to heat and circulate conditioning fluid through the lubricant heat exchanger 124 (e.g., the tube bundle 200), enabling thermal energy transfer to the flow of lubricant 112 directed through the lubricant heat exchanger 124 (e.g., outside of the tube bundle 200). Conversely, in response to determining the compressor 104 is in the active or operating state, the controller 136 may be configured to suspend operation (e.g., a heating operation) of the lubricant heat exchanger 124 and / or heat source 196. In certain configurations, in response to determining the compressor 104 is in the active or operating state, the controller 136 may be configured to enable circulation of conditioning fluid through the lubricant heat exchanger 124 to cool the flow of lubricant 112.

[0056] Additionally or alternatively, in response to determining ambient temperature is below a threshold temperature (e.g., a temperature at which the working fluid may condense within the compressor 104 at a certain pressure), the controller 136 may be configured to activate the lubricant heat exchanger 124 and / or the heat source 196 to heat and circulate conditioning fluid through the lubricant heat exchanger 124 (e.g., the tube bundle 200), enabling thermal energy transfer to the flow of lubricant through the lubricant heat exchanger 124 (e.g., outside of the tube bundle 200). Conversely, in response to determining the ambient temperature is equal to or above the threshold temperature, the controller 136 may be configured to suspend operation (e.g., a heating operation) of the lubricant heat exchanger 124 and / or heat source 196.

[0057] Indeed, operation of the lubricant heat exchanger 124 and / or heat source 196 may be controlled based on both the operating state of the compressor 104 and the ambient temperature. For example, in response to determining ambient temperature is below a threshold temperature and the compressor 104 is in the stalled or suspended state, the controller 136 may be configured to activate the lubricant heat exchanger 124 and / or the heat source 196 to heat and circulate conditioning fluid through the lubricant heat exchanger 124 (e.g., the tube bundle 200), enabling thermal energy transfer to the flow of lubricant 112 directed through the lubricant heat exchanger 124 (e.g., outsideof the tube bundle 200). Conversely, in response to determining the ambient temperature is equal to or above the threshold temperature or the compressor 104 is in an operating state, the controller 136 may be configured to suspend operation (e.g., a heating operation) of the lubricant heat exchanger 124 and / or heat source 196.

[0058] After heating, the flow of lubricant 112 may be biased (e.g., by the lubricant pump 120 or suction created by the compressor 104) toward the lubricant filter 128 via a conduit 212 extending between the lubricant heat exchanger 124 and the lubricant filter 128. The lubricant filter 128 may be configured to remove contaminants from the flow of lubricant 112 prior to direction into the compressor 104, protecting components (e.g., bearings, rotors) of the compressor 104 and increasing longevity of the compressor 104. Additionally, filtering the flow of lubricant 112 may increase the lifetime of the flow of lubricant 112, reducing changeover costs. The lubricant filter 128 may include various filtering components, such as membranes (e.g., cellulose, synthetic fibers, etc.), configured to separate containments from the flow of lubricant 112. The lubricant filter 128 may include any suitable type, such as a spin-on filter, a cartridge filter, a full-flow filter, a bypass filter, a mechanical filter, a magnetic filter, a centrifugal filter, a sedimentation filter, a vacuum filter, and so forth.

[0059] After filtering, the flow of lubricant 112 (e.g., filtered lubricant) may be biased toward the compressor 104 via a conduit 216 extending between the lubricant filter 128 and the compressor 104. In certain configurations, the containments, such as sludge, dirt, sediment, and so on, may be directed away from the lubricant circulation system 108.

[0060] FIG. 6 is a process flow diagram illustrating an embodiment of a method 220 of operating a lubricant circulation system 108, such as the lubricant circulation system 108 of FIG. 5. It should be noted that certain embodiments of the method 220 may not include all the steps illustrated in FIG. 6 and described below, and certain embodiments of the method 220 may include additional steps not illustrated in FIG. 6 and not described below. Further, an ordering of the steps in FIG. 6 described in detail below should not be taken as implying a chronology of all embodiments of the method 220. Indeed, while certain embodiments of the method 220 may be implemented in a chronology of the steps illustrated in FIG. 6 and described in detail below, other orderings and / or chronologies are also in accordance with the present disclosure.

[0061] In the illustrated embodiment, the method 220 may include determining an operating state or mode of the compressor 104, indicated by block 224. For example, the controller 136 may receive feedback indicative of the operating state of the compressor 104 via the one or more sensors 178 (e.g., a direct indication of compressor operation, or a parameter of working fluid such as pressure or temperature, which may be indicative of the operating state of the compressor 104).

[0062] Referring to block 228, the method 220 may include comparing a measured temperature (e.g., a measured ambient temperature) to a threshold temperature. For example, the controller 136 may receive feedback or data indicative of the measured temperature from the one or more sensors 178 (e.g., ambient temperature sensors). The threshold temperature may include a temperature (e.g., correlated to the temperature at the working fluid location within the compressor 104) at which working fluid may condense or is likely to condense within the compressor 104, at a given working fluid pressure. As such, in some instances, the threshold temperature may be variable and at least partially based on the pressure of working fluid measured within the compressor 104. It should be noted that the measured temperature and threshold temperature may not be directly applicable values. For example, the measured ambient temperature may correspond to a different temperature within the compressor 104 based on an established correlation. Adjusted values may be used to estimate or predict condensation at the relevant temperatures and pressures.

[0063] Referring to block 232, the method 220 may include determining whether the compressor 104 is in a stalled or suspended state and / or determining whether the measured temperature (e.g., measured ambient temperature) is less than or equal to the threshold temperature. In some instances, the stalled or suspended state of the compressor 104 may be a state where the compressor 104 is not currently compressing working fluid, such as when the compressor 104 operation is actively suspended (e.g., when no conditioning is required), or forcibly suspended (e.g., during a power outage or a stalled state). In response to determining the compressor 104 is not in the stalled or suspended state (e.g., in an active or operating state) and / or in response to determining the measured temperature is greater than the threshold temperature, the method may proceed to block 236. In response to determining the compressor 104 is in the stalled or suspended state and / or in response to determining the measuredtemperature is less than or equal to the threshold temperature, the method may proceed to block 240.

[0064] At block 236, the controller 136 may suspend operation of the lubricant pump 120. Indeed, during operation of the compressor 104, a pressure imparted on the working fluid may also impart a relatively high pressure to flow of lubricant 112, enabling circulation through the lubricant circulation system 108 (e.g., during a cooling mode of the lubrication circulation system) without use of the lubricant pump 120. Additionally or alternatively, the controller 136 may actuate the bypass valve 192 to an open position to enable bypass of the flow of lubricant 112 around the lubricant pump 120 via the bypass line 188.

[0065] Moreover, the controller 136 may suspend operation of the heat source 196 in response to the negative determination indicated by block 232. As will be appreciated, during operation of the compressor 104, a flow of lubricant 112 and working fluid compressed within the compressor 104 may generate a sufficient amount of heat to block or reduce condensation within the compressor 104. As such, additional heating of the flow of lubricant 112 from the lubricant heat exchanger 124 may not be desired. Instead, the lubricant circulation system 108 may operate in a cooling mode, activity cooling the flow of lubricant 112 via the lubricant heat exchanger 124. In configurations of the lubricant circulation system 108 using an electronic drain valve 176, the controller 136 may be configured to actuate the drain valve 176 to the closed position, disabling flow of lubricant 112 from the lubricant drain 114. Instead, a mixture of flow of lubricant 112 and working fluid may be discharged from the discharge port 152 of the compressor 104 and directed to the lubricant separator 116.

[0066] At block 240, the controller 136 may activate operation of the lubricant pump 120 to bias the flow of lubricant 112 through one or more components of the lubricant circulation system 108. Additionally or alternatively, the controller 136 may actuate the bypass valve 192 to a closed position to disable bypass of the flow of lubricant 112 around the lubricant pump 120 via the bypass line 188, forcing the flow of lubricant 112 through the lubricant pump 120.

[0067] Moreover, the controller 136 may activate operation of the heat source 196 and / or the lubricant heat exchanger 124 in response to the positive determinationindicated by block 232. The lubricant heat exchanger 134 and / or the heat source 196 may enable heating of the flow of lubricant 112 during the stalled or suspend state of the compressor 104. The heated flow of lubricant 112 may be directed into the stalled or suspended compressor 104 to transfer thermal energy to working fluid therein, raising the temperature of the working fluid and reducing working fluid condensation. In configurations of the lubricant circulation system 108 using an electronic drain valve 176, the controller 136 may be configured to actuate the drain valve 176 to the open position, enabling flow of lubricant 112 from the lubricant drain 114 for constant circulating through the lubrication circulation system 108.

[0068] Embodiments of the present disclosure may provide one or more technical effects or benefits useful in the operation of an HVAC system. In particular, presently disclosed embodiments enable improved heated lubricant distribution to a compressor, increasing heating uniformity within the compressor and other component of the HVAC system and reducing condensation within the compressor.

[0069] While only certain features and embodiments have been illustrated and described, many modifications and changes may occur to those skilled in the art, such as variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, such as temperatures and pressures, mounting arrangements, use of materials, colors, orientations, and so forth, 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 resequenced 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.

[0070] Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described, such as those unrelated to the presently contemplated best mode, or those unrelated to enablement. 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, andmanufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.

[0071] The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [performing [a function] ... ” or “step for [performing [a function] ... ”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).

Claims

CLAIMS:

1. A heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system comprising: a compressor; a sensor system, wherein the sensor system includes one or more sensors configured to detect one or more operating parameters; a lubricant circulation system configured to supply lubricant to the compressor, wherein the lubricant circulation system comprises: a lubricant circuit configured to circulate the lubricant; a lubricant heat exchanger disposed on the lubricant circuit and configured to heat the lubricant; and a controller communicatively coupled to the compressor and the lubricant circulation system, wherein the controller is configured to control the lubrication circulation system to heat the lubricant via the lubricant heat exchanger in response to determining the compressor is in a non-operational state based on the one or more operating parameters.

2. The HVAC&R system of claim 1, wherein the compressor comprises a drain configured to discharge the lubricant from the compressor to a drain conduit, wherein the drain conduit comprises a valve.

3. The HVAC&R system of claim 2, wherein the valve is communicatively coupled to the controller, and in response to determining the compressor is in the non- operational state, the controller is configured to transition the valve to an open position.

4. The HVAC&R system of claim 2, wherein the valve comprises a ball valve or a check valve.

5. The HVAC&R system of claim 1, wherein the lubricant heat exchanger is configured to receive a conditioning fluid and facilitate thermal energy transfer between the conditioning fluid and the lubricant.

6. The HVAC&R system of claim 5, wherein the lubricant heat exchanger is configured to heat the conditioning fluid via an electric heater communicatively coupled to the controller, and in response to determining the compressor is in the non- operational state, the controller is configured operate the electric heater.

7. The HVAC&R system of claim 1, wherein the lubricant circulation system comprises a lubricant separator disposed along the lubricant circuit and configured to separate the lubricant from a working fluid, wherein the lubricant separator is disposed downstream of the compressor and upstream of the lubricant heat exchanger.

8. The HVAC&R system of claim 1, wherein the lubricant circulation system comprises a pump communicatively coupled to the controller and configured to facilitate circulation of the lubricant through the lubricant circuit, wherein the controller is configured: receive data indicative of a lubricant pressure within the lubricant circuit; compare the lubricant pressure to a threshold lubricant pressure; in response to determining the lubricant pressure is greater than or equal to the threshold lubricant pressure, instruct the pump to suspend operation; and in response to determining the lubricant pressure is less than the threshold lubricant pressure, instruct the pump to operate.

9. The HVAC&R system of claim 1, wherein the compressor is a screw compressor comprising a slide valve system including a slide valve and a slide valve cavity, and the slide valve is configured to transition to a first position within the slide valve cavity to facilitate draining of the lubricant during the non-operational state of the compressor, and the slide valve is configured to transition to a second position within the slide valve cavity to at least partially block draining of the lubricant in an operational state of the compressor.

10. A heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system comprising: a compressor comprising: a slide valve system comprising:a slide valve cavity; and a slide valve configured to transition within the slide valve cavity between a first position and a second position; and a drain fluidly coupling the slide valve cavity to a drain conduit via an opening formed by the slide valve in the second position; and a lubricant circulation system configured to supply lubricant to the compressor, wherein the lubricant circulation system comprises a heat source configured to heat the lubricant; a sensor system including one or more sensors configured to monitor a temperature; and a controller communicatively coupled to the heat source and the sensor system, wherein the controller is configured to operate the heat source in response to determining the compressor is in a non-operational state and the temperature is less than a threshold temperature.

11. The HVAC&R system of claim 10, comprising the drain conduit, wherein the drain conduit comprises a valve configured to regulate fluid flow of the lubricant from the compressor, and the valve comprises a ball valve, a check valve, or a solenoid valve.

12. The HVAC&R system of claim 10, comprising a lubricant heat exchanger, wherein lubricant heat exchanger is configured to receive a flow of conditioning fluid and the lubricant.

13. The HVAC&R system of claim 12, wherein the lubricant heat exchanger is in fluid communication with the heat source, and the heat source is configured to heat the flow of conditioning fluid.

14. The HVAC&R system of claim 10, wherein the sensor system is configured to monitor ambient temperature as the temperature.

15. The HVAC&R system of claim 10, wherein the lubricant circulation system comprises a lubricant separator configured to separate the lubricant from a working fluid and lubricant mixture discharged from the compressor.

16. The HVAC&R system of claim 10, wherein the lubrication circulation system comprises a lubricant filter disposed upstream of the compressor and configured to filter the lubricant.

17. A method for lubricant circulation within a heating, ventilation, air conditioning, and / or refrigeration (HVAC&R) system, the method comprising: receiving data indicative of an ambient temperature; determining whether a compressor of an HVAC&R system is in a non-operating state; in response to determining the ambient temperature is less than a threshold temperature and the compressor is in the non-operating state: circulating lubricant into the compressor from a lubricant circuit, wherein circulating the lubricant comprises operating a pump to bias the lubricant through the lubricant circuit; heating the lubricant via a lubricant heat exchanger; draining a mixture of lubricant and working fluid from the compressor, wherein the mixture is directed into a lubricant separator via a discharge conduit; separating the mixture into lubricant and working fluid in the lubricant separator; and directing the lubricant separated from the mixture in the lubricant separator into the lubricant heat exchanger.

18. The method of claim 17, wherein draining the mixture comprises actuating a drain of the compressor, wherein the drain comprises a ball valve, a check valve, or a solenoid valve.

19. The method of claim 17, wherein heating the lubricant comprises operating an electric heater configured to heat a flow of conditioning fluid, wherein the flow of conditioning fluid is placed in a heat exchanging relationship with the lubricant.

20. The method of claim 19, comprising: receiving additional data indicative of a lubricant temperature; and adjusting operation of the electric heater based on the additional data.

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