System and Method for Lubricant Separation and Return Control

Abstract

An HVACR system includes: a first compressor and a second compressor arranged in parallel and fluidly connected, a condenser, an expansion device, an evaporator, and a lubricant separator. The first compressor includes a first lubricant reservoir and a first suction port. The second compressor includes a second lubricant reservoir and a second suction port. The lubricant separator is disposed between the evaporator and the first and second compressors and includes a fluid inlet and two fluid outlets. A first fluid outlet of the two fluid outlets is fluidly connected to at least one of the first lubricant reservoir and the second lubricant reservoir. A second fluid outlet of the two fluid outlets is fluidly connected to the first suction port and the second suction port. The second fluid outlet includes a nozzle that is disposed within a flow passage of the lubricant separator such that a gap is maintained between an outer surface of the nozzle and an inner surface of the flow passage.

Description

Technical Field

[0001] The present disclosure generally relates to heating, ventilation, air conditioning, and refrigeration (HVACR) systems. More specifically, the present disclosure relates to systems and methods for controlling lubricant separation and return. Background Art

[0002] Heat transfer loops for HVACR systems typically include a fluid-connected compressor, condenser, expansion device, and evaporator. The compressor typically includes a rotating component driven by an electric motor. The HVACR system can include a rooftop unit to provide conditioned air to an air distribution system including ductwork. The heat transfer loop can include multiple compressors. In one application, one or more of the multiple compressors can be turned on or off during operation. Summary of the Invention

[0003] The present disclosure generally relates to HVACR systems. More specifically, the present disclosure relates to systems and methods for controlling lubricant separation and return.

[0004] Embodiments disclosed herein are directed to lubricant management for multiple compressors connected in parallel. The multiple compressors include compressors having lubricant reservoirs. The compressors are driven by electric motors. In some embodiments, the lubricant reservoir is disposed in a relatively vertical lower portion of the compressor such that lubricant can be collected in the lubricant reservoir by gravity. In some embodiments, the lubricant is entrained in the heat transfer fluid of the heat transfer loop of the HVACR system.

[0005] In some embodiments, the multiple compressors can include a first compressor and a second compressor. In some embodiments, the first compressor can be a variable speed compressor and the second compressor can be a constant speed compressor. In some embodiments, both the first compressor and the second compressor can be constant speed compressors.

[0006] In some embodiments, the multiple compressors can include more than two compressors. In some embodiments, the multiple compressors can include three compressors. In some embodiments, the multiple compressors can include four compressors. In some embodiments, the multiple compressors include at least one variable speed compressor.

[0007] The lubricant separator can be disposed between the evaporator and the multiple compressors. The lubricant separator can be designed to control the flow of the heat transfer fluid and the lubricant to each compressor.

[0008] In some embodiments, the lubricant separator may separate the gaseous heat transfer fluid from the evaporator of the heat transfer loop into a lubricant-rich portion and a lubricant-free portion. In some embodiments, the lubricant-rich portion of the gaseous heat transfer fluid may be provided to a common conduit that is fluidly connected to a reservoir of multiple compressors. In some embodiments, the lubricant-free portion of the gaseous heat transfer fluid may be provided to a common suction conduit that is fluidly connected to the suction inlets of multiple compressors.

[0009] An HVACR system is disclosed. The system includes a first compressor, a second compressor, a condenser, an expansion device, an evaporator, and a lubricant separator that are fluidly connected. The first compressor and the second compressor are arranged in parallel. The first compressor includes a first lubricant reservoir and a first suction inlet. The second compressor includes a second lubricant reservoir and a second suction inlet. The lubricant separator is disposed between the evaporator and the first compressor and the second compressor. The lubricant separator includes a fluid inlet and two fluid outlets. The first fluid outlet of the two fluid outlets is fluidly connected to at least one of the first lubricant reservoir and the second lubricant reservoir. The second fluid outlet of the two fluid outlets is fluidly connected to the first suction inlet and the second suction inlet. The second fluid outlet includes a nozzle that is disposed within the flow channel of the lubricant separator such that a gap (e.g., an annular gap) is maintained between the outer surface of the nozzle and the inner surface of the flow channel.

[0010] A method for separating and returning lubricant for an HVACR system is disclosed. The method includes separating a stream of a heat transfer fluid and lubricant mixture into a lubricant-rich portion and a lubricant-free portion. The method further includes directing the lubricant-rich portion to at least one of a first lubricant reservoir of a first compressor and a second lubricant reservoir of a second compressor. The method further includes directing the lubricant-free portion to a first suction inlet of the first compressor and a second suction inlet of the second compressor. The first compressor and the second compressor are arranged in parallel in the heat transfer loop. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Reference is made to the drawings that form a part of this disclosure, which illustrate embodiments of the systems and methods described in this specification that may be practiced.

[0012] Figure 1A is a schematic diagram of a heat transfer loop according to an embodiment.

[0013] Figure 1B is a schematic diagram of a heat transfer loop according to another embodiment.

[0014] Figure 1C is a schematic diagram of a heat transfer loop according to yet another embodiment.

[0015] Figure 2 is a cross-sectional view of a lubricant separator for use in a heat transfer circuit of Figures 1A - 1C .

[0016] Figures 3A - 3C Shows multiple views of a lubricant transfer pipe assembly according to an embodiment.

[0017] Like reference numerals always denote like parts. DETAILED DESCRIPTION

[0018] The present disclosure generally relates to HVACR systems. More specifically, the present disclosure relates to systems and methods for controlling lubricant separation and return.

[0019] In some embodiments, a heat transfer loop may include multiple compressors. The multiple compressors may be connected in parallel in the heat transfer loop. A common suction pipe may be fluidly connected to the suction inlets of the multiple compressors. A heat transfer fluid and lubricant mixture may flow through the common suction pipe and into one or more of the suction inlets of the multiple compressors. Each of the multiple compressors may include a lubricant sump. Each compressor may be driven by an electric motor disposed within the same housing / casing / vessel as the compressor. In some embodiments, the lubricant sump may be disposed in the relatively vertical lower portion of the compressor such that lubricant may be collected in the lubricant sump by gravity. In some embodiments, lubricant may be entrained in the heat transfer fluid of the heat transfer loop of an HVACR system. The lubricant may accordingly be provided to one or more of the multiple compressors via the corresponding suction inlet by the common suction pipe that supplies gaseous heat transfer fluid from the evaporator of the heat transfer loop to the multiple compressors. The lubricant may flow around the electric motor of the compressor to return to the compressor sump. In some embodiments, the compressor electric motor may include a bypass region having a hydraulic diameter. In some embodiments, the bypass region of the electric motor may be defined as the region between the outer surface of the electric motor and the inner surface of the housing / casing / vessel. In some embodiments, due to, for example, the size and / or design limitations of the compressor, the bypass region of the electric motor and its hydraulic diameter may be limited. The bypass region of the electric motor may allow lubricant to flow out of the suction chamber of the compressor to return to the compressor sump. In some embodiments, when one (or more) of the compressors is turned off, the manifold scheme of the heat transfer loop may not reliably return lubricant to the sump of the operating compressor. This is because gaseous heat transfer fluid may flow through the off compressor, and through the lubricant transfer pipe (e.g., lubricant equalizing line), and upward through the limited bypass region of the electric motor of the operating compressor. This may cause lubricant to remain in the suction chamber of the compressor rather than drain around the bypass region of the electric motor (sink to the sump). In this manner, when staging off compressors, a very low lubricant level may exist in the compressor manifold. In such embodiments, the internal geometry of the compressor (e.g., the limited bypass region of the electric motor and its limited hydraulic diameter) may prevent lubricant from draining downward into the sump, especially when using a large (e.g., having a diameter equal to the diameter of the suction line) equalizing line. In some embodiments, the bypass region of the electric motor may be increased to allow lubricant to drain around the bypass region of the electric motor (sink to the sump).

[0020] The embodiments disclosed herein can separate lubricant from a gaseous heat transfer fluid. A common suction conduit for the gaseous heat transfer fluid can be fluidly connected to the suction inlets of a plurality of compressors. The embodiments disclosed herein can redirect the lubricant to a common lubricant conduit (e.g., a lubricant transfer conduit), which can be fluidly connected to the sump of the plurality of compressors. The separation can result in a lubricant-enriched portion and a lubricant-free portion.

[0021] As used in this specification, a "lubricant-enriched portion" includes a portion of a heat transfer fluid (e.g., refrigerant) and lubricant (e.g., oil) mixture that has a relatively higher lubricant concentration relative to another portion of the heat transfer fluid stream.

[0022] As used in this specification, a "lubricant-free portion" includes a portion of a heat transfer fluid and lubricant mixture that has a relatively lower lubricant concentration relative to another portion of the heat transfer fluid stream. It is to be understood that in some embodiments, the lubricant-free portion may still include some lubricant. It is also to be understood that in some embodiments, the lubricant-free portion may not include lubricant.

[0023] In some embodiments, a lubricant separator (described later) can receive the suction gaseous heat transfer fluid stream. The lubricant separator can include a nozzle. The lubricant separator can prevent the lubricant-enriched portion (e.g., lubricant) from flowing into the suction inlets of the plurality of compressors, but allow the lubricant-free portion (e.g., gaseous heat transfer fluid) to pass through and reach the suction inlets of the compressors. The lubricant-enriched portion can flow downward along a tee (e.g., a T-connector) below the lubricant separator into a lubricant transfer conduit (e.g., a lubricant equalizing line) that connects to the sump of the compressors. In this way, there will be no deposition of the lubricant-rich portion in the suction chamber of the compressors, but rather the lubricant-rich portion can be directly transferred into the lubricant transfer conduit that feeds into the sump of the compressors.

[0024] The embodiments disclosed herein can keep the lubricant-enriched portion (returned from the heat transfer loop) outside of the suction conduit of the compressor and directly transfer the lubricant-enriched portion (e.g., via a lubricant transfer conduit separate from the suction conduit) to the sump of the compressor to avoid the need to bleed off the lubricant-enriched portion around the bypass region of the compressor motor.

[0025] Figure 1AIt is a schematic diagram of a heat transfer circuit 10A according to an embodiment. The heat transfer circuit 10A generally includes: a plurality of compressors 12A, 12B; a condenser 14; an expansion device 16; and an evaporator 18. The expansion device 16 allows the working fluid to expand. The expansion causes a significant reduction in the temperature of the working fluid. The "expansion device" as described herein may also be referred to as an expander. In an embodiment, the expander may be an expansion valve, an expansion plate, an expansion vessel, an orifice, etc., or other such types of expansion mechanisms. It should be understood that the expander may be any type of expander used on-site to expand the working fluid to reduce the temperature of the working fluid. The heat transfer circuit 10A is exemplary and may be modified to include additional components. For example, in some embodiments, the heat transfer circuit 10A may include other components such as, but not limited to, an energy-saving heat exchanger, one or more lubricant separators, a receiver tank, a dryer, a suction liquid heat exchanger, etc.

[0026] The heat transfer circuit 10A can generally be applied to various systems for controlling environmental conditions (such as, for example, temperature, humidity, air quality, etc.) in a space (commonly referred to as an air-conditioned space). Examples of systems include, but are not limited to, HVACR systems, transport refrigeration systems, etc.

[0027] The components of the heat transfer circuit 10A are fluidly connected. The heat transfer circuit 10A can be specifically configured as a cooling system (such as, for example, an air conditioning system) capable of operating in a cooling mode. Alternatively, the heat transfer circuit 10A can be specifically configured as a heat pump system that can operate in both a cooling mode and a heating / defrosting mode.

[0028] The heat transfer circuit 10A can operate according to well-known principles. The heat transfer circuit 10A can be configured to heat or cool a heat transfer fluid or medium (such as, for example, a liquid such as, but not limited to, water), in which case the heat transfer circuit 10A can generally represent a liquid chiller system. The heat transfer circuit 10A can alternatively be configured to heat or cool a heat transfer fluid or medium (such as, for example, a gas such as, but not limited to, air), in which case the heat transfer circuit 10A can generally represent an air conditioner or a heat pump.

[0029] In operation, compressors 12A, 12B compress a heat transfer fluid (e.g., refrigerant, etc.) from a relatively low-pressure gas to a relatively high-pressure gas. The relatively high-pressure and high-temperature gas is discharged from compressors 12A, 12B and flows through condenser 14. According to well-known principles, the heat transfer fluid flows through condenser 14 and rejects heat to the heat transfer fluid or medium (e.g., water, air, etc.), thereby cooling the heat transfer fluid. The cooled heat transfer fluid, now in a liquid state, flows to expansion device 16. Expansion device 16 reduces the pressure of the heat transfer fluid. As a result, a portion of the heat transfer fluid is converted to a gaseous state. The heat transfer fluid, now in a liquid-vapor mixture state, flows to evaporator 18. The heat transfer fluid flows through evaporator 18 and absorbs heat from the heat transfer fluid or medium (e.g., water, air, etc.), thereby heating the heat transfer fluid and converting it to a gaseous state. The gaseous heat transfer fluid then returns to compressors 12A, 12B. While the heat transfer loop 10A operates, for example, in a cooling mode (e.g., while enabling compressors 12A, 12B), the above process continues.

[0030] Compressors 12A, 12B can be, for example but not limited to, scroll compressors. In some embodiments, compressors 12A, 12B can be other types of compressors. Examples of other types of compressors include but are not limited to reciprocating compressors, positive displacement compressors, or other types of compressors suitable for use in heat transfer loop 10A and having a lubricant sump. Compressor 12A can generally represent a variable-speed compressor, and compressor 12B can generally represent a constant-speed compressor. In some embodiments, both compressor 12A and compressor 12B can be constant-speed compressors. In some embodiments, compressors 12A, 12B can alternatively be step control compressors (e.g., compressors having two or more stages within the compressor). In some embodiments, compressors 12A, 12B can be compressors having different capacities. For example, according to some embodiments, compressor 12A can have a relatively larger capacity than compressor 12B. It is to be understood that alternatively, compressor 12B can have a relatively larger capacity than compressor 12A.

[0031] Compressors 12A, 12B are connected in parallel in heat transfer loop 10A. Thus, the gaseous heat transfer fluid leaving evaporator 18 is provided to each of compressors 12A, 12B via pipe 22 (e.g., the suction line). Lubricant separator 20 receives the gaseous heat transfer fluid at fluid inlet 24 and provides the gaseous heat transfer fluid to common lubricant transfer pipe 23 via first fluid outlet 26 and to common suction pipe 25 via second fluid outlet 28. In the following according to Figure 2Additionally, the lubricant separator 20 according to some embodiments will be specifically discussed. After compression, the relatively high-pressure and high-temperature gas is discharged from the compressor 12A via the discharge pipe 32A and from the compressor 12B via the discharge pipe 32B. In some embodiments, the discharge pipes 32A, 32B of the compressors 12A, 12B are connected at the discharge pipe 34 to supply the combined relatively high-pressure and high-temperature gas to the condenser 14.

[0032] The heat transfer fluid in the heat transfer loop 10A generally includes the lubricant entrained by the heat transfer fluid. The lubricant is supplied to the compressors 12A, 12B to lubricate, for example, the bearings of the compressors 12A, 12B and seal the leakage paths. When discharging the relatively high-pressure and high-temperature heat transfer fluid from the compressors 12A, 12B, the heat transfer fluid generally carries a portion of the lubricant, and a portion of the lubricant is initially transferred to the compressors 12A, 12B along with the heat transfer fluid entering the compressors 12A, 12B via the pipe 22. A portion of the lubricant is retained in the lubricant reservoirs 13A, 13B of the compressors 12A, 12B.

[0033] The lubricant separator 20 can separate the lubricant from the gaseous heat transfer fluid and lubricant mixture in the heat transfer fluid from the pipe 22. The separation can produce a lubricant-enriched portion (the lubricant generally flows along the pipe / wall of the pipeline) and a lubricant-free portion. The lubricant separator 20 is disposed on the pipe 22, and its branch faces downward (to direct the lubricant to the reservoir). The lubricant separator 20 has a nozzle structure with a diameter that decreases in the direction opposite to the flow of the heat transfer fluid. The common suction pipe 25 (which is fluidly connected to the second fluid outlet 28) is fluidly connected to the suction pipe 21. A connector (e.g., a T-shaped connector, not shown) can connect the common suction pipe 25 to the suction pipe 21. The suction pipe 21 is fluidly connected to the suction port 27A of the compressor 12A and the suction port 27B of the compressor 12B.

[0034] The lubricant reservoirs 13A and 13B of the compressors 12A and 12B are fluidly connected via a lubricant transfer pipe 36. The lubricant transfer pipe 36 is provided at the lubricant level of the lubricant reservoirs 13A and 13B, which allows the lubricant to flow between the compressor 12A and the compressor 12B. The fluid flow of the lubricant is controlled by the pressure difference between the lubricant reservoir 13A of the compressor 12A and the lubricant reservoir 13B of the compressor 12B. Therefore, if the operation of the compressor 12A or 12B is modified, the fluid flow of the lubricant between the compressors 12A and 12B can be affected. In some embodiments, a desired pressure difference can be selected such that, under various compressor 12A and 12B operating conditions, the lubricant flow in the lubricant reservoir 13A is directed to the lubricant reservoir 13B. In some embodiments, the desired pressure difference can alternatively be referred to as a target pressure difference. In some embodiments, the desired pressure difference can be the minimum pressure difference that will cause the lubricant flow from the lubricant reservoir 13A to be directed to the lubricant reservoir 13B. In some embodiments, the desired pressure difference can be the minimum pressure difference that can define the flow rate reaching the compressor 12A at the maximum compressor speed and can define the flow rate reaching the compressor 12B at the minimum suction flow rate corresponding to a low suction temperature. Other operating conditions when the compressor 12B is running typically result in a higher pressure difference.

[0035] In some embodiments, depending on the desired application, the diameter of the lubricant transfer pipe 36 can be relatively small compared to other lubricant transfer pipes. In some embodiments, a relatively small diameter can be selected to limit the heat transfer fluid from flowing from the lubricant reservoir 13A to the lubricant reservoir 13B. In some embodiments, the relatively small diameter lubricant transfer pipe 36 can, for example, prevent the pressure in the lubricant reservoir 13A and the pressure in the lubricant reservoir 13B from equalizing. In some embodiments, this can, for example, maintain the pressure difference between the lubricant reservoirs 13A and 13B to maintain the flow of the lubricant between the lubricant reservoirs 13A and 13B. In some embodiments, the compressors 12A and 12B can be designed to include an outlet having a diameter designed to fit a lubricant transfer pipe of a relatively large diameter. In such an embodiment, an adapter (not shown) can be used to connect the relatively small diameter lubricant transfer pipe 36 to the compressors 12A and 12B.

[0036] In some embodiments, the lubricant transfer pipe 36 can be a lubricant equalization line configured to equalize the pressure in the lubricant reservoir 13A and the pressure in the lubricant reservoir 13B.

[0037] The common lubricant transfer conduit 23 (which is fluidly connected to the first fluid outlet 26) is fluidly connected to the lubricant transfer conduit 36. A connector (e.g., a T-shaped connector, not shown) may connect the common lubricant transfer conduit 23 to the lubricant transfer conduit 36. The lubricant transfer conduit 36 is fluidly connected to the lubricant reservoir 13A via the reservoir inlet 29A of the compressor 12A and is fluidly connected to the lubricant reservoir 13B via the reservoir inlet 29B of the compressor 12B. It is to be understood that in some embodiments, 29A and / or 29B may be inlets for receiving lubricant (e.g., from the common lubricant transfer conduit 23 via the first fluid outlet 26 or from a compressor having a higher pressure in the lubricant reservoir). In some embodiments, 29A and / or 29B may be outlets for transferring lubricant (to a compressor having a lower pressure in the lubricant reservoir).

[0038] Figure 1B is a schematic diagram of a heat transfer loop 10B according to another embodiment. The heat transfer loop 10B is similar to Figure 1A the heat transfer loop 10A shown. The differences between the heat transfer loop 10B and the heat transfer loop 10A are described below.

[0039] The lubricant separator 20 receives the gaseous heat transfer fluid at the fluid inlet 24 and supplies the gaseous heat transfer fluid to the lubricant transfer conduit 23 (the first lubricant transfer conduit) via the first fluid outlet 26. The lubricant transfer conduit 23 (which is fluidly connected to the first fluid outlet 26) is fluidly connected to the reservoir inlet 29C of the lubricant reservoir 13B of the compressor 12B. In this embodiment, the lubricant reservoir 13B has a higher operating pressure than the lubricant reservoir 13A. In one embodiment, the lubricant transfer conduit 23 has a smaller diameter than, for example, a suction line (e.g., the suction conduit 21). In one embodiment, the lubricant transfer conduit 36 (the second lubricant transfer conduit) has a smaller diameter than, for example, a suction line (e.g., the suction conduit 21). The lubricant transfer conduit 36 is connected between a lubricant reservoir (13B) having a higher operating pressure (than the operating pressure of 13A) and a lubricant reservoir (13A) having a lower operating pressure (than the operating pressure of 13B). In this way, lubricant can flow from the lubricant reservoir having a higher operating pressure (e.g., 13B) to the lubricant reservoir having a lower operating pressure (e.g., 13A). It is to be understood that this process can be repeated for additional compressors to "cascade" lubricant from a higher pressure reservoir to a lower pressure reservoir to reduce the reservoir pressure, provided that each lubricant transfer conduit (e.g., 36, the second lubricant transfer conduit) only connects two compressors. It is to be understood that the first lubricant transfer conduit and the second lubricant transfer conduit may be separate / independent conduits.

[0040] The lubricant transfer pipe 36 at the storage tank outlet 29B of the compressor 12B is fluidly connected to the lubricant storage tank 13A and is connected to the lubricant storage tank 13A via the storage tank inlet 29A of the compressor 12A. It is to be understood that in some embodiments, 29A and / or 29B may be inlets for receiving lubricant (e.g., receiving lubricant from a compressor having a higher pressure in the lubricant storage tank). In some embodiments, 29A and / or 29B may be outlets for transferring lubricant (to a compressor having a lower pressure in the lubricant storage tank).

[0041] The lubricant storage tanks 13A, 13B of the compressors 12A, 12B are fluidly connected via the lubricant transfer pipe 36. The lubricant transfer pipe 36 is provided at the lubricant level of the lubricant storage tanks 13A, 13B, which allows lubricant to flow between the compressor 12A and the compressor 12B. The fluid flow of the lubricant is controlled by the pressure difference between the lubricant storage tank 13A of the compressor 12A (the downstream compressor, having a lower pressure in the lubricant storage tank 13A than the pressure in the lubricant storage tank 13B) and the lubricant storage tank 13B of the compressor 12B (the upstream compressor, having a higher pressure in the lubricant storage tank 13B than the pressure in the lubricant storage tank 13A). Thus, if the operation of the compressor 12A or 12B is modified, the fluid flow of the lubricant between the compressors 12A, 12B can be affected. In some embodiments, a desired pressure difference can be selected such that under various operating conditions of the compressors 12A, 12B, the lubricant flow in the lubricant storage tank 13B is directed to the lubricant storage tank 13A. In some embodiments, the desired pressure difference may alternatively be referred to as the target pressure difference. In some embodiments, the desired pressure difference may be the minimum pressure difference that will cause the lubricant flow from the lubricant storage tank 13B to be directed to the lubricant storage tank 13A. In some embodiments, the desired pressure difference may be the minimum pressure difference that can define the flow rate to the upstream compressor 12B at the maximum compressor speed and can define the flow rate to the downstream compressor 12A at the minimum suction flow rate corresponding to a low suction temperature. Other operating conditions when the downstream compressor 12A is running typically result in a higher pressure difference.

[0042] In some embodiments, depending on the desired application, the diameter of the lubricant transfer conduit 36 may be relatively small compared to other lubricant transfer conduits. In some embodiments, a relatively small diameter may be selected to limit the flow of the heat transfer fluid from the lubricant reservoir 13B to the lubricant reservoir 13A. In some embodiments, the relatively small diameter lubricant transfer conduit 36 may, for example, prevent the pressures in the lubricant reservoirs 13B and 13A from equalizing. In some embodiments, this may, for example, maintain a pressure differential between the lubricant reservoirs 13A and 13B to maintain the flow of lubricant between the lubricant reservoirs 13A and 13B. In some embodiments, the compressors 12A, 12B may be designed to include an outlet having a diameter designed to fit a lubricant transfer conduit of a relatively large diameter. In such embodiments, an adapter (not shown) may be used to connect the relatively small diameter lubricant transfer conduit 36 to the compressors 12A, 12B.

[0043] In some embodiments, the lubricant transfer conduit 36 may be a lubricant equalization line configured to equalize the pressure in the lubricant reservoir 13A and the pressure in the lubricant reservoir 13B.

[0044] Figure 1C is a schematic diagram of a heat transfer loop 10C according to yet another embodiment. The heat transfer loop 10C is similar to Figure 1B the heat transfer loop 10B shown. The differences between the heat transfer loop 10C and the heat transfer loop 10B are described below.

[0045] The heat transfer loop 10C includes a third compressor 12C. The compressors 12A, 12B, and 12C are connected in parallel in the heat transfer loop 10C. Thus, the gaseous heat transfer fluid leaving the evaporator 18 is provided to each of the compressors 12A, 12B, and 12C via the conduit 22. The lubricant separator 20 receives the gaseous heat transfer fluid at the fluid inlet 24 and provides the gaseous heat transfer fluid to the lubricant transfer conduit 23 (first lubricant transfer conduit) via the first fluid outlet 26 and to the common suction conduit 25 via the second fluid outlet 28. In the following according to Figure 2Additionally, the lubricant separator 20 according to some embodiments is specifically discussed. After compression, the gas at relatively high pressure and high temperature is discharged from compressor 12A via discharge pipe 32A, from compressor 12B via discharge pipe 32B, and from compressor 12C via discharge pipe 32C. In some embodiments, the discharge pipes 32A, 32B, 32C of compressors 12A, 12B, 12C are connected at discharge pipe 34 to provide the combined relatively high pressure and high temperature gas to condenser 14. For example, discharge pipes 32A and 32B can be connected (e.g., using a T-shaped connector), and then the connected (32A and 32B) discharge pipe can be connected to discharge pipe 32C (e.g., using a T-shaped connector). Discharge pipes 32A and 32C can be connected, and then the connected pipes can be connected to 32B. Discharge pipes 32C and 32B can be connected, and then the connected pipes can be connected to 32A.

[0046] The common suction pipe 25 (which is fluidly connected to the second fluid outlet 28) is fluidly connected to the suction pipe 21. A connector (e.g., a T-shaped connector, not shown) can connect the common suction pipe 25 to the suction pipe 21. The suction pipe 21 is fluidly connected to the suction inlet 27A of compressor 12A, the suction inlet 27B of compressor 12B, and the suction inlet 27C of compressor 12C using connectors (e.g., T-shaped connectors, not shown).

[0047] The lubricant separator 20 receives the gaseous heat transfer fluid at the fluid inlet 24 and provides the gaseous heat transfer fluid to the lubricant transfer pipe 23 via the first fluid outlet 26. The lubricant transfer pipe 23 (which is fluidly connected to the first fluid outlet 26) is fluidly connected to the reservoir inlet 29C of the lubricant reservoir 13B of compressor 12B.

[0048] In this embodiment, the lubricant reservoir 13B has the highest operating pressure among the lubricant reservoirs 13A, 13B, and 13C. In one example, the lubricant transfer pipe 23 has a smaller diameter than, for example, the suction line (e.g., the suction pipe 21). In one example, the lubricant transfer pipes (36A and 36B, the second lubricant transfer pipe and the third lubricant transfer pipe) have a smaller diameter than, for example, the suction line (e.g., the suction pipe 21). The lubricant transfer pipe 36A (the second lubricant transfer pipe) is connected between the lubricant reservoir (13B) having a higher operating pressure (than the operating pressure of 13C) and the lubricant reservoir (13C) having a lower operating pressure (than the operating pressure of 13B). The lubricant transfer pipe 36B (the third lubricant transfer pipe) is connected between the lubricant reservoir (13C) having a higher operating pressure (than the operating pressure of 13A) and the lubricant reservoir (13A) having a lower operating pressure (than the operating pressure of 13C).

[0049] In this way, the lubricant can flow from the lubricant transfer pipe 23 to the lubricant reservoir having the highest operating pressure (e.g., 13B), then to the lubricant reservoir having the second highest operating pressure (e.g., 13C), and then to the lubricant reservoir having the lowest operating pressure (e.g., 13A). It is to be understood that this process can be repeated for additional (fourth, fifth, etc., also connected in parallel in the heat transfer loop) compressors so that the lubricant "cascades" from higher pressure reservoirs to lower pressure reservoirs to reduce the reservoir pressure, provided that each lubricant transfer pipe (e.g., 36A, 36B, etc.) is connected to only two compressors. It is to be understood that the first lubricant transfer pipe, the second lubricant transfer pipe, and the third lubricant transfer pipe can be separate / independent pipes.

[0050] The lubricant transfer pipe 36A is fluidly connected to the lubricant reservoir 13B via the reservoir outlet 29B of the compressor 12B and is connected to the lubricant reservoir 13C via the reservoir inlet 29F of the compressor 12C. The lubricant transfer pipe 36B is fluidly connected to the lubricant reservoir 13A via the reservoir outlet 29D of the compressor 12A and is fluidly connected to the lubricant reservoir 13C via the reservoir inlet 29E of the compressor 12C. It is to be understood that in some embodiments, 29A and / or 29B and / or 29D and / or 29E can be inlets for receiving lubricant (e.g., receiving lubricant from a compressor having a higher pressure in the lubricant reservoir). In some embodiments, 29A and / or 29B and / or 29D and / or 29E can be outlets for transferring lubricant (to a compressor having a lower pressure in the lubricant reservoir).

[0051] The lubricant reservoirs 13C and 13B of the compressors 12C and 12B are fluidly connected via a lubricant transfer pipe 36A. The lubricant reservoirs 13A and 13C of the compressors 12A and 12C are fluidly connected via a lubricant transfer pipe 36B. The lubricant transfer pipe 36A is provided at the lubricant level of the lubricant reservoirs 13C and 13B, which allows the lubricant to flow between the compressor 12C and the compressor 12B. The lubricant transfer pipe 36B is provided at the lubricant level of the lubricant reservoirs 13A and 13C, which allows the lubricant to flow between the compressor 12A and the compressor 12C.

[0052] The fluid flow of the lubricant is controlled by the pressure difference between the lubricant reservoir 13C of the compressor 12C (downstream compressor, having a lower pressure in the lubricant reservoir 13C than in the lubricant reservoir 13B) and the lubricant reservoir 13B of the compressor 12B (upstream compressor, having a higher pressure in the lubricant reservoir 13B than in the lubricant reservoir 13C). The fluid flow of the lubricant is controlled by the pressure difference between the lubricant reservoir 13C of the compressor 12C (upstream compressor, having a higher pressure in the lubricant reservoir 13C than in the lubricant reservoir 13A) and the lubricant reservoir 13A of the compressor 12A (downstream compressor, having a lower pressure in the lubricant reservoir 13A than in the lubricant reservoir 13C).

[0053] Therefore, if the operation of the compressor 12A and / or 12B and / or 12C is modified, it can affect the fluid flow of the lubricant between the compressors 12C and 12B and / or between the compressors 12A and 12C. In some embodiments, a desired pressure difference can be selected such that, under various operating conditions of the compressors 12C and 12B, the lubricant flow in the lubricant reservoir 13B is directed to the lubricant reservoir 13C. In some embodiments, a desired pressure difference can be selected such that, under various operating conditions of the compressors 12A and 12C, the lubricant flow in the lubricant reservoir 13C is directed to the lubricant reservoir 13A.

[0054] In some embodiments, the desired pressure differential may alternatively be referred to as the target pressure differential. In some embodiments, the desired pressure differential may be the minimum pressure differential that will cause the lubricant flow from lubricant reservoir 13B to be directed to lubricant reservoir 13C (and / or that will cause the lubricant flow from lubricant reservoir 13C to be directed to lubricant reservoir 13A). In some embodiments, the desired pressure differential may be the minimum pressure differential that can define the flow rate to the upstream compressor 12B at the maximum compressor speed and can define the flow rate to the downstream compressor 12C at the minimum suction flow rate corresponding to the low suction temperature. In some embodiments, the desired pressure differential may be the minimum pressure differential that can define the flow rate to the upstream compressor 12C at the maximum compressor speed and can define the flow rate to the downstream compressor 12A at the minimum suction flow rate corresponding to the low suction temperature. Other operating conditions when the downstream compressor 12A (or downstream compressor 12C) is operating typically result in a higher pressure differential.

[0055] In some embodiments, depending on the desired application, the diameter of the lubricant transfer pipes (36A and / or 36B) may be relatively small compared to other lubricant transfer pipes. In some embodiments, a relatively small diameter may be selected to limit the flow of the heat transfer fluid from lubricant reservoir 13B to lubricant reservoir 13C (and / or from lubricant reservoir 13C to lubricant reservoir 13A). In some embodiments, the relatively small diameter lubricant transfer pipes (36A, 36B) may, for example, prevent the pressure in lubricant reservoir 13B and the pressure in lubricant reservoir 13C (and / or the pressure in lubricant reservoir 13C and the pressure in lubricant reservoir 13A) from equalizing. In some embodiments, this may, for example, maintain the pressure differential between lubricant reservoirs 13C, 13B (or 13A, 13C) to maintain the flow of lubricant between lubricant reservoirs 13C, 13B (or 13A, 13C). In some embodiments, the compressors 12A, 12B, 12C may be designed to include an outlet having a diameter designed to fit a lubricant transfer pipe of a relatively larger diameter. In such embodiments, an adapter (not shown) may be used to connect the relatively small diameter lubricant transfer pipes (36A, 36B) to the compressors 12A, 12B, 12C.

[0056] In some embodiments, the lubricant transfer pipes (36A, 36B) may be lubricant equalization lines configured to equalize the pressure in lubricant reservoir 13C and the pressure in lubricant reservoir 13B (and / or the pressure in lubricant reservoir 13A and the pressure in lubricant reservoir 13C).

[0057] The embodiments disclosed herein can help direct lubricant into a lubricant sump rather than having the lubricant return through a suction line. The lubricant can first be separated from the suction line (e.g., via lubricant separator 20), transferred through a dedicated lubricant return line, and enter the compressor sump with the highest sump pressure in the heat transfer loop. The lubricant can first be delivered to the sump with the highest pressure and then flow in the direction of gradually decreasing pressure. Then, multiple compressors can be connected in this cascading sequence (in parallel), and the lubricant can be made to flow from a higher-pressure sump to a lower-pressure sump. As long as there is a pressure difference between the compressor sumps (connected via lubricant transfer pipes) and there is a sufficient quantity of lubricant, the lubricant can be transferred.

[0058] It is to be understood that in an embodiment, the heat transfer loop can have one compressor. In such an embodiment, the lubricant can be directed from the lubricant separator to the compressor sump via a lubricant transfer pipe.

[0059] The embodiments disclosed herein use smaller lubricant transfer pipes (e.g., the lubricant transfer pipe has a smaller diameter than, for example, the diameter of the suction line) for directing lubricant to the compressor sump with the highest pressure and / or for connecting between compressor sumps with different pressures (to allow the lubricant to move from a higher-pressure sump to a lower-pressure sump).

[0060] The embodiments disclosed herein can effectively manage the lubricant level at all load levels and conditions. Laboratory tests show that with the embodiments disclosed herein, the reliability of the compressor can be improved at all lubricant levels.

[0061] Figure 2 is a cross-sectional view of a lubricant separator 20 according to some embodiments. In operation, the heat transfer fluid in pipe 22 ( Figures 1A - 1C ) is supplied to the fluid inlet 24 of the lubricant separator 20. In some embodiments, the fluid inlet 24 can be a part of pipe 22.

[0062] Generally, the lubricant in the heat transfer fluid and lubricant mixture is more concentrated at the perimeter of the fluid inlet 24 and less concentrated towards the center of the fluid inlet 24. The lubricant in the heat transfer fluid and lubricant mixture collides with walls 50, 52 and flows towards the fluid outlet 26, which is fluidly connected to a common lubricant transfer pipe 23. The lubricant-free heat transfer fluid flowing towards the center of the fluid inlet 24 (e.g., along the longitudinal axis of the fluid inlet 24) enters nozzle 40 and exits through fluid outlet 28 to the common suction pipe 25.

[0063] The nozzle 40 extends from the fluid outlet 28 towards the fluid inlet 24. In some embodiments, the nozzle 40 at least includes a portion having a diameter smaller than that of the fluid inlet 24. In some embodiments, the nozzle 40 at least includes a portion having a diameter smaller than that of the fluid inlet 24 such that the inlet of the nozzle 40 is disposed at or near the middle region of the fluid flow from the fluid inlet 24. In some embodiments, the size of the nozzle 40 can be determined such that a gap is maintained between the inner wall of the fluid inlet 24 and the outer wall of the nozzle 40. In some embodiments, the nozzle 40 extends beyond a longitudinal line extending along the longitudinal axis of the fluid outlet 26. In some embodiments, the nozzle 40 can be integrally formed with the common suction duct 25. The size includes the radius R2 of the nozzle 40, the length L1 of the extension 40A of the nozzle 40, and the length L2 of the tapered portion 40B of the nozzle 40. As shown, the radius R1 of the fluid inlet 24 can be greater than the radius R3 of the fluid outlet 28. The fluid outlet 26 has a radius R4, and the radius R4 can also be selected to control the flow of the lubricant-rich heat transfer fluid towards the common lubricant delivery duct 23. By controlling the position and cross-sectional area of the nozzle 40, the distributed flow from the fluid inlet 24 to the fluid outlets 26, 28 can be controlled for various compressor conditions (e.g., compressor speed, etc.). For example, the extent to which the nozzle 40 extends towards the fluid inlet 24 relative to the fluid outlet 26 is controlled. In the illustrated embodiment, the nozzle 40 and the fluid outlet 26 overlap. In some embodiments, the nozzle 40 and the fluid outlet 26 do not overlap. In some embodiments, the expansion angle θ of the nozzle 40 can be selected to control the rate of fluid expansion of the heat transfer fluid flowing through the nozzle 40 towards the fluid outlet 28. Generally, the pressure drop increases as the angle θ increases.

[0064] In the illustrated embodiment, there can be a (vertical) gap between the end / edge of the extension 40A (both on the fluid inlet 24 side) and the inner surface of the fluid outlet 26 such that the lubricant-enriched portion can flow into the fluid outlet 26, while the lubricant-free portion can flow into the fluid outlet 28. The gap can be configured to prevent an excessive amount of the lubricant-free portion from flowing into the fluid outlet 26. In some embodiments, the gap can range from 0 to 2×R4. In some embodiments, the gap can be greater than R4 / 2 but less than R4.

[0065] Tests have shown that in a heat transfer circuit that does not have the embodiments disclosed herein (for comparison purposes, for example), lubricant loss may occur within five minutes, for example, after starting one compressor and shutting down another compressor.

[0066] Tests have also shown that in a heat transfer loop having an embodiment disclosed herein, the amount of lubricant can be stabilized under various conditions. For example, a lubricant return line is utilized that has sufficient restriction to prevent excessive gaseous heat transfer fluid from passing through the line.

[0067] Figures 3A to 3C Shows multiple views of a lubricant transfer line assembly 300 according to an embodiment. The lubricant transfer line assembly 300 can be used to connect Figures 1A - 1C lubricant reservoirs 13A, 13B, 13C, and / or connect Figures 1A - 1C a lubricant separator 20, and one of the lubricant reservoirs 13A, 13B, 13C.

[0068] Figure 3A Shows a perspective view of a lubricant transfer line assembly 300 according to an embodiment. Figure 3B Shows a side view of a lubricant transfer line assembly 300 according to an embodiment. Figure 3C Shows another side view of a lubricant transfer line assembly 300 according to an embodiment. Figure 3B and Figure 3C are side views of the same lubricant transfer line assembly 300, but rotated 90° relative to each other. For simplicity of the specification, unless otherwise specifically stated, the features will generally be referred to with reference to Figures 3A - 3C the drawings, without specifically referring to a particular drawing.

[0069] The lubricant transfer line assembly 300 includes a connector 305, a first line 380, and a second line 385. The first line 380 includes line portions 315, 320, 325, and 345. The second line 385 includes line portions 310 and 350.

[0070] Each connector 305 has a first end and a second end. The first end of the connector 305 has a reduced diameter compared to the second end of the connector 305. The line portion 315 (and / or 310) is attached, fixed, or otherwise connected to the first end of the connector 305. In one embodiment, the line portion 315 (and / or 310) can be brazed to the first end of the connector 305. The second end of the connector 305 (having a larger diameter than the first end) can be connected to, for example, other lines (not shown) for transferring lubricant. It is to be understood that the second end of the connector 305 can also have a reduced diameter similar to the first end of the connector 305 to connect to other lines for transferring lubricant.

[0071] The lubricant transfer line assembly 300 further includes a barrel 340 having a first end and a second end. The first end of the barrel 340 has a reduced diameter compared to the second end of the barrel 340. Sleeves 330 and 335 are attached / fixed / connected to the first end of the barrel 340, for example, in a side-by-side manner.

[0072] A portion of the second conduit 385 passes through the sleeve 335 and the barrel 340. At the end of the sleeve 335 remote from the barrel 340, the gap between the outer surface of the second conduit 385 and the inner surface of the sleeve 335 is sealed (e.g., brazed) to avoid leakage. A portion of the second conduit 385 inside the barrel 340 is inclined from the axis of the barrel 340 towards the lower part of the barrel 340.

[0073] A portion of the first conduit 380 passes through the sleeve 330 and the barrel 340. At the end of the sleeve 330 remote from the barrel 340, the gap between the outer surface of the first conduit 380 and the inner surface of the sleeve 330 is sealed (e.g., brazed) to avoid leakage. A portion 341 of the first conduit 380 inside the barrel 340 is inclined from the axis of the barrel 340 towards the lower part of the barrel 340. The barrel 340 can hold the first conduit 380 and / or the second conduit 385 in place and enable the lubricant delivery conduit assembly 300 to be sealed, for example, by brazing. The second end of the barrel 340 can be brazed to a connector (not shown) of the compressor sump. Once the second end of the barrel 340 is brazed to the compressor sump, the interior of the barrel 340 is opened to communicate with the sump pressure.

[0074] The conduit portion 350 of the second conduit 385 and the conduit portion 345 of the first conduit 380 are arranged side by side in the lower part of the barrel 340. Arranging the conduit portions 350 and 345 in the lower part of the barrel 340 can keep the level of the lubricant in the compressor sump very low. Since the compressor sump connection (which is connected to the second end of the barrel 340) is higher than the conduit portions 350 and 345, this can allow the lubricant level to build up to enter the motor of the compressor, which in turn can increase the lubricant circulation rate in the HVACR system.

[0075] In one embodiment, the diameter of the pipe 380 and / or 385 can be, for example, equal to or about 0.25 inches (equal to or about 6.35 millimeters). The diameter of the pipe 380 and / or 385 generally matches the width / diameter of the bypass area where the lubricant of the compressor motor can bypass the motor. The diameter of the pipe 380 and / or 385 can be any suitable size for matching the width / diameter of the bypass area of the compressor motor to allow the lubricant to flow downward through the motor. It is to be understood that a large diameter of the pipe 380 and / or 385 (e.g., equal to or about 1.125 inches (equal to or about 28.575 millimeters)) can easily exhaust the compressor sump, thus not allowing the lubricant to drop through the motor of the compressor, for example, when only one compressor is operating. A very small diameter (e.g., equal to or about 0.25 inches (equal to or about 6.35 millimeters)) can reduce the exhaust to allow the lubricant to drop through the motor of the compressor, for example, when only one compressor is operating. In one embodiment, the diameter of the second end of the tube 340 can be equal to or about 1.125 inches (equal to or about 28.575 millimeters). The diameter of the second end of the tube 340 can be any suitable size for matching the size of the connector on the compressor sump.

[0076] In one embodiment, the first pipe 380 (e.g., via the pipe section 345) can be connected to the inlet of, for example, the sump of the compressor, and the second pipe 385 (e.g., via the pipe section 350) can be connected to the outlet of, for example, the sump of the compressor. In another embodiment, the first pipe 380 (e.g., via the pipe section 345) can be connected to the outlet of, for example, the sump of the compressor, and the second pipe 385 (e.g., via the pipe section 350) can be connected to the inlet of, for example, the sump of the compressor. It is to be understood that in one embodiment, the second end of the tube 340 can be brazed to a connector (not shown) on the compressor sump, and the first pipe 380 and the second pipe 385 extend into the compressor sump such that they independently draw lubricant from the compressor sump or discharge lubricant into the compressor sump.

[0077] The axis of the pipe section 315 and the axis of the pipe section 325 form an angle equal to or about 120°. This angle can help separate the two brazed joints (the joint between the connector 305 and the pipe section 315, and the joint between the connector 305 and the pipe section 310). If the two brazed joints are close together, the first brazed joint may become unsoldered during the brazing operation of the joint. The pipe section 320 is the bending section between the pipe section 315 and the pipe section 325. The lubricant can flow from one end of the pipe (380 and / or 385) to the other end of the pipe (380 and / or 385).

[0078] Refer to Figure 1A, the heat transfer loop 10A can have two lubricant transfer pipe assemblies 300. The first lubricant transfer pipe assembly 300 is connected to the tank inlet / outlet (e.g., 29B) of the lubricant tank 13B via one of the pipes (380, 385) of the first lubricant transfer pipe assembly 300, and the other of the pipes (380, 385) of the first lubricant transfer pipe assembly 300 is not used (e.g., the other is sealed to prevent lubricant leakage). The lubricant transfer pipe 36 can be connected to one of the pipes (380, 385) of the first lubricant transfer pipe assembly 300 via a connector 305 of the first lubricant transfer pipe assembly 300. The first lubricant transfer pipe assembly 300 is disposed between the lubricant transfer pipe 36 and the tank inlet / outlet (29B).

[0079] The second lubricant transfer pipe assembly 300 is connected to the inlet / outlet (29A) of the lubricant tank 13A via one of the pipes (380, 385) of the second lubricant transfer pipe assembly 300, and the other of the pipes (380, 385) of the second lubricant transfer pipe assembly 300 is not used (e.g., sealed to prevent lubricant leakage). The lubricant transfer pipe 36 can be connected to one of the pipes (380, 385) of the second lubricant transfer pipe assembly 300 via a connector 305 of the second lubricant transfer pipe assembly 300. The second lubricant transfer pipe assembly 300 is disposed between the lubricant transfer pipe 36 and the tank inlet 29A. It is to be understood that each of 29A, 29B can be the inlet or outlet of the corresponding tank.

[0080] Referring to Figure 1B , the heat transfer loop 10B can have two lubricant transfer pipe assemblies 300. The first lubricant transfer pipe assembly 300 is connected to the tank inlet (e.g., 29C) of the lubricant tank 13B via one of the pipes (380, 385) of the first lubricant transfer pipe assembly 300, and is connected to the tank outlet (29B) of the lubricant tank 13B via the other of the pipes (380, 385) of the first lubricant transfer pipe assembly 300. The lubricant transfer pipe 23 can be connected to one of the pipes (380, 385) of the first lubricant transfer pipe assembly 300 via a connector 305 of the first lubricant transfer pipe assembly 300. The lubricant transfer pipe 36 can be connected to the other of the pipes (380, 385) of the first lubricant transfer pipe assembly 300 via another connector 305 of the first lubricant transfer pipe assembly 300. The first lubricant transfer pipe assembly 300 is disposed between the lubricant transfer pipes (23 and / or 36) and the tank inlet / outlet (29C and / or 29B).

[0081] The second lubricant transfer pipe assembly 300 is connected to the inlet of the lubricant reservoir 13A via one of the pipes (380, 385) of the second lubricant transfer pipe assembly 300, and the other of the pipes (380, 385) of the second lubricant transfer pipe assembly 300 is not used (for example, the other is sealed to prevent lubricant leakage). The lubricant transfer pipe 36 can be connected to one of the pipes (380, 385) of the second lubricant transfer pipe assembly 300 via a connector 305 of the second lubricant transfer pipe assembly 300. The second lubricant transfer pipe assembly 300 is disposed between the lubricant transfer pipe 36 and the reservoir inlet 29A. It is to be understood that each of 29A, 29B, 29C can be an inlet or an outlet of the corresponding reservoir.

[0082] Referring Figure 1C , the heat transfer loop 10C can have three lubricant transfer pipe assemblies 300. The first lubricant transfer pipe assembly 300 is connected to the reservoir inlet (e.g., 29C) of the lubricant reservoir 13B via one of the pipes (380, 385) of the first lubricant transfer pipe assembly 300, and is connected to the reservoir outlet (29B) of the lubricant reservoir 13B via the other of the pipes (380, 385) of the first lubricant transfer pipe assembly 300. The lubricant transfer pipe 23 can be connected to one of the pipes (380, 385) of the first lubricant transfer pipe assembly 300 via a connector 305 of the first lubricant transfer pipe assembly 300. The lubricant transfer pipe 36A can be connected to the other of the pipes (380, 385) of the first lubricant transfer pipe assembly 300 via another connector 305 of the first lubricant transfer pipe assembly 300. The first lubricant transfer pipe assembly 300 is disposed between the lubricant transfer pipes (23 and / or 36A) and the reservoir inlet / outlet (29C and / or 29B).

[0083] The second lubricant transfer pipe assembly 300 is connected to an inlet (e.g., 29F) of the lubricant reservoir 13C via one of the pipes (380, 385) of the second lubricant transfer pipe assembly 300, and is connected to an outlet (29E) of the lubricant reservoir 13C via the other of the pipes (380, 385) of the second lubricant transfer pipe assembly 300. The lubricant transfer pipe 36A can be connected to one of the pipes (380, 385) of the second lubricant transfer pipe assembly 300 via a connector 305 of the second lubricant transfer pipe assembly 300. The lubricant transfer pipe 36B can be connected to the other of the pipes (380, 385) of the second lubricant transfer pipe assembly 300 via another connector 305 of the second lubricant transfer pipe assembly 300. The second lubricant transfer pipe assembly 300 is disposed between the lubricant transfer pipes (36A and / or 36B) and the reservoir inlet / outlet (29E and / or 29F).

[0084] The third lubricant transfer pipe assembly 300 is connected to an inlet 29D of the lubricant reservoir 13A via one of the pipes (380, 385) of the third lubricant transfer pipe assembly 300, and the other of the pipes (380, 385) of the third lubricant transfer pipe assembly 300 is connected to an outlet 29A of the lubricant reservoir 13A. It is to be understood that the outlet 29A may not be used (e.g., the outlet 29A is sealed to prevent lubricant leakage). The lubricant transfer pipe 36B can be connected to one of the pipes (380, 385) of the third lubricant transfer pipe assembly 300 via a connector 305 of the third lubricant transfer pipe assembly 300. The third lubricant transfer pipe assembly 300 is disposed between the lubricant transfer pipe (36B) and the reservoir inlet / outlet (29D and / or 29A). It is to be understood that each of 29A, 29B, 29C, 29D, 29E can be an inlet or an outlet of the corresponding reservoir.

[0085] Aspect:

[0086] It should be noted that any one of the following aspects 1 to 10 can be combined with any one of aspects 11 to 19.

[0087] Aspect 1. An HVACR system, the system comprising:

[0088] A first compressor, a second compressor, a condenser, an expansion device, an evaporator, and a lubricant separator that are fluidly connected;

[0089] Wherein the first compressor and the second compressor are arranged in parallel,

[0090] The first compressor includes a first lubricant reservoir and a first suction port,

[0091] The second compressor includes a second lubricant reservoir and a second suction port, and

[0092] The lubricant separator is disposed between the evaporator and the first and second compressors. The lubricant separator includes a fluid inlet and two fluid outlets. A first fluid outlet of the two fluid outlets is fluidly connected to at least one of the first lubricant reservoir and the second lubricant reservoir. A second fluid outlet of the two fluid outlets is fluidly connected to the first suction port and the second suction port. The second fluid outlet includes a nozzle that is disposed within a flow channel of the lubricant separator such that a gap is maintained between an outer surface of the nozzle and an inner surface of the flow channel.

[0093] Aspect 2. The system according to aspect 1, wherein the first compressor is a variable speed compressor and the second compressor is a constant speed compressor.

[0094] Aspect 3. The system according to aspect 1, wherein both the first compressor and the second compressor are constant speed compressors.

[0095] Aspect 4. The system according to any one of aspects 1 to 3, wherein the first compressor and the second compressor are scroll compressors.

[0096] Aspect 5. The system according to any one of aspects 1 to 4, wherein the nozzle extends from the second fluid outlet of the two fluid outlets towards the fluid inlet.

[0097] Aspect 6. The system according to any one of aspects 1 to 5, wherein a longitudinal axis of the second fluid outlet of the two fluid outlets is collinear with a longitudinal axis of the fluid inlet.

[0098] Aspect 7. The system according to any one of aspects 1 to 6, wherein a longitudinal axis of the first fluid outlet of the two fluid outlets is perpendicular to the fluid inlet.

[0099] Aspect 8. The system according to any one of aspects 1 to 7, wherein a radius of the fluid inlet is greater than a radius of the second fluid outlet of the two fluid outlets.

[0100] Aspect 9. The system according to any one of aspects 1 to 8, further comprising a third compressor,

[0101] wherein the first compressor, the second compressor, and the third compressor are arranged in parallel.

[0102] Aspect 10. The system according to any one of aspects 1 to 9 further includes a first lubricant transfer pipeline and a second lubricant transfer pipeline,

[0103] wherein a first fluid outlet of the two fluid outlets is fluidly connected to the first lubricant storage tank via the first lubricant transfer pipeline, and the first lubricant storage tank is fluidly connected to the second lubricant storage tank via the second lubricant transfer pipeline.

[0104] Aspect 11. A method for separating and returning lubricant for a heating, ventilation, air conditioning, and refrigeration (HVACR) system, the method comprising:

[0105] separating a flow of a heat transfer fluid and lubricant mixture into a lubricant-enriched portion and a lubricant-free portion;

[0106] directing the lubricant-enriched portion to at least one of a first lubricant storage tank of a first compressor and a second lubricant storage tank of a second compressor; and

[0107] directing the lubricant-free portion to a first suction inlet of the first compressor and a second suction inlet of the second compressor,

[0108] wherein the first compressor and the second compressor are arranged in parallel in a heat transfer loop.

[0109] Aspect 12. The method according to aspect 11, wherein the separation of the flow is accomplished using a lubricant separator including a fluid inlet and two fluid outlets, a first fluid outlet of the two fluid outlets being fluidly connected to at least one of the first lubricant storage tank and the second lubricant storage tank, a second fluid outlet of the two fluid outlets being fluidly connected to the first suction inlet and the second suction inlet, the second fluid outlet including a nozzle disposed within a flow channel of the lubricant separator such that a gap is maintained between an outer surface of the nozzle and an inner surface of the flow channel.

[0110] Aspect 13. The method according to aspect 11, wherein the first compressor is a variable-speed compressor and the second compressor is a constant-speed compressor.

[0111] Aspect 14. The method according to aspect 11, wherein both the first compressor and the second compressor are constant-speed compressors.

[0112] Aspect 15. The method according to any one of aspects 11 to 14, wherein the first compressor and the second compressor are scroll compressors.

[0113] Aspect 16. The method according to any one of aspects 12 to 15, wherein the nozzle extends from the second fluid outlet of the two fluid outlets towards the fluid inlet.

[0114] Aspect 17. The method according to any one of aspects 12 to 16, wherein the longitudinal axis of the second fluid outlet of the two fluid outlets is collinear with the longitudinal axis of the fluid inlet.

[0115] Aspect 18. The method according to any one of aspects 12 to 17, wherein the longitudinal axis of the first fluid outlet of the two fluid outlets is perpendicular to the fluid inlet.

[0116] Aspect 19. The method according to any one of aspects 12 to 18, wherein the radius of the fluid inlet is greater than the radius of the second fluid outlet of the two fluid outlets.

[0117] The terms used in this specification are intended to describe specific embodiments and are not intended to be limiting. Unless otherwise expressly indicated, the terms "a", "an" and "the" also include the plural forms. When the terms "comprise" and / or "include" are used in this specification, they specify the presence of the stated features, wholes, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, elements and / or components.

[0118] For the foregoing description, it should be understood that specific changes can be made without departing from the scope of the present disclosure, particularly in terms of the structural materials used and the shape, size and arrangement of the components. This specification and the described embodiments are merely exemplary, and the true scope and spirit of the present disclosure are indicated by the appended claims.

Claims

1. A heating, ventilation, air conditioning, and refrigeration (HVACR) system, the system comprising: A first compressor, a second compressor, a condenser, an expansion device, an evaporator, and a lubricant separator that are fluidly connected; wherein the first compressor and the second compressor are arranged in parallel; the first compressor includes a first lubricant reservoir and a first suction port; the second compressor includes a second lubricant reservoir and a second suction port, and the lubricant separator is disposed between the evaporator and the first compressor and the second compressor, the lubricant separator includes a fluid inlet and two fluid outlets, a first fluid outlet of the two fluid outlets is connected to a reservoir inlet of at least one of the first lubricant reservoir and the second lubricant reservoir via a first lubricant transfer pipe, a second fluid outlet of the two fluid outlets is connected to the first suction port and the second suction port via a suction line, the second fluid outlet includes a nozzle, and the nozzle is disposed in a flow channel of the lubricant separator such that a gap is maintained between an outer surface of the nozzle and an inner surface of the flow channel.

2. The system according to claim 1, wherein, The first compressor is a variable-speed compressor, and the second compressor is a constant-speed compressor.

3. The system according to claim 1, wherein, Both the first compressor and the second compressor are constant-speed compressors.

4. The system according to claim 1, wherein, The first compressor and the second compressor are scroll compressors.

5. The system according to claim 1, wherein, The nozzle extends from the second fluid outlet of the two fluid outlets toward the fluid inlet.

6. The system according to claim 1, wherein, A longitudinal axis of the second fluid outlet of the two fluid outlets is collinear with a longitudinal axis of the fluid inlet.

7. The system according to claim 1, wherein, A longitudinal axis of the first fluid outlet of the two fluid outlets is perpendicular to the fluid inlet.

8. The system according to claim 1, wherein, A radius of the fluid inlet is greater than a radius of the second fluid outlet of the two fluid outlets.

9. The system according to claim 1, further comprising a third compressor, wherein, The first compressor, the second compressor, and the third compressor are arranged in parallel.

10. The system according to claim 1, further comprising a second lubricant transfer pipeline, wherein, The first fluid outlet of the two fluid outlets is connected to the first lubricant reservoir via the first lubricant transfer pipe, and the first lubricant reservoir is connected to the second lubricant reservoir via the second lubricant transfer pipe.

11. A method for separating and returning lubricant for a heating, ventilation, air conditioning, and refrigeration (HVACR) system, the method comprising: Separate a flow of a heat transfer fluid and lubricant mixture into a lubricant-enriched portion and a lubricant-free portion; Direct the lubricant-enriched portion to a reservoir inlet of at least one of the first lubricant reservoir of the first compressor and the second lubricant reservoir of the second compressor via a first lubricant transfer pipe; and Direct the lubricant-free portion to the first suction port of the first compressor and the second suction port of the second compressor via a suction line, wherein the first compressor and the second compressor are arranged in parallel in a heat transfer circuit.

12. The method according to claim 11, wherein, The separation of the flow is accomplished using a lubricant separator including a fluid inlet and two fluid outlets, a first fluid outlet of the two fluid outlets being connected to a tank inlet of at least one of the first lubricant tank and the second lubricant tank, a second fluid outlet of the two fluid outlets being connected to the first suction port and the second suction port, the second fluid outlet including a nozzle disposed within a flow channel of the lubricant separator such that a gap is maintained between an outer surface of the nozzle and an inner surface of the flow channel.

13. The method according to claim 11, wherein, The first compressor is a variable speed compressor and the second compressor is a constant speed compressor.

14. The method according to claim 11, wherein, Both the first compressor and the second compressor are constant speed compressors.

15. The method according to claim 11, wherein, The first compressor and the second compressor are scroll compressors.

16. The method according to claim 12, wherein,The nozzle extends from the second fluid outlet of the two fluid outlets toward the fluid inlet.

17. The method according to claim 12, wherein, A longitudinal axis of the second fluid outlet of the two fluid outlets is collinear with a longitudinal axis of the fluid inlet.

18. The method according to claim 12, wherein, A longitudinal axis of the first fluid outlet of the two fluid outlets is perpendicular to the fluid inlet.

19. The method according to claim 12, wherein, A radius of the fluid inlet is larger than a radius of the second fluid outlet of the two fluid outlets.

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