Lubricant Quality Management for Compressors

Abstract

A heating, ventilation, air conditioning and refrigeration (HVACR) system is disclosed. The HVACR system includes: a refrigerant circuit. The refrigerant circuit includes a compressor, a condenser, an expansion device and an evaporator that are fluidly connected. A controller is electrically connected to the compressor. The controller is configured to prevent the compressor from operating at a rate less than a minimum rate limit. A lubricant separator has an inlet fluidly connected between the compressor and the condenser, and a plurality of outlets. A first outlet of the plurality of outlets is fluidly connected to the condenser. A second outlet of the plurality of outlets is fluidly connected to one or more components of the compressor to provide lubricant to the one or more components.

Description

[0001] Divisional application statement

[0002] This application is a divisional application of the Chinese invention patent application filed on June 14, 2019, with the invention name “Lubricant Quality Management of Compressors” and application number 201910516270.0. Technical Field

[0003] The present disclosure relates generally to heating, ventilation, air conditioning, and refrigeration (HVACR) systems. More specifically, the present disclosure relates to lubricant quality management for compressors in HVACR systems. Background Art

[0004] Heating, ventilation, air conditioning and refrigeration (HVACR) systems often include compressors. Compressors such as, but not limited to, screw compressors and scroll compressors utilize bearings to support a rotating shaft. Bearings often include a lubricant system. If the bearings are not properly lubricated, the bearings, and ultimately, the compressor, may fail before the expected service life of the bearings. Summary of the invention

[0005] The present disclosure relates generally to a heating, ventilation, air conditioning and refrigeration (HVACR) system. More specifically, the present disclosure relates to lubricant quality management for compressors in HVACR systems.

[0006] In an embodiment, the HVACR system comprises a variable speed compressor. In an embodiment, the variable speed compressor is a positive displacement compressor.

[0007] In an embodiment, the variable speed compressor is a variable speed screw compressor. In an embodiment, the variable speed screw compressor can be operated between a maximum speed and a minimum speed. In an embodiment, the minimum speed limit can be set to a value greater than the minimum speed at which the variable speed compressor can operate. For example, based on the saturated suction temperature and saturated discharge temperature of the selected refrigerant and lubricant, the minimum speed limit can be determined for a selected compressor efficiency and bearing size.

[0008] In an embodiment, the selected refrigerant includes a refrigerant having a low discharge superheat and being miscible with the selected lubricant, which may result in high lubricant dilution.

[0009] In an embodiment, the selected refrigerant includes a refrigerant having a global warming potential (GWP) relatively lower than that of R134a and usable as a replacement refrigerant for R134a.

[0010] In an embodiment, the selected refrigerant may be R1234ze(E), R-513A, or the like.

[0011] In an embodiment, the minimum speed limit is negatively correlated with the bearing size. That is, in an embodiment, as the bearing size decreases, the minimum speed limit increases.

[0012] In an embodiment, the HVACR system includes a lubricant separator. The lubricant separator may include a lubricant reservoir. In an embodiment, combining the lubricant separator and the lubricant reservoir may reduce the complexity of the overall HVACR system.

[0013] A heating, ventilation, air conditioning and refrigeration (HVACR) system is disclosed. The HVACR system includes a refrigerant circuit. The refrigerant circuit includes a compressor, a condenser, an expansion device and an evaporator that are fluidly connected. A controller is electrically connected to the compressor, and the controller is configured to prevent the compressor from operating at a rate less than a minimum rate limit. A lubricant separator has an inlet fluidly connected between the compressor and the condenser, and a plurality of outlets. A first outlet of the plurality of outlets is fluidly connected to the condenser. A second outlet of the plurality of outlets is fluidly connected to one or more components of the compressor to provide lubricant to the one or more components.

[0014] A method for controlling a variable speed compressor is disclosed. The method includes: determining a saturated suction temperature and a saturated discharge temperature using a controller of the variable speed compressor; calculating a minimum rate limit for the variable speed compressor based on the saturated suction temperature and the saturated discharge temperature using the controller of the variable speed compressor. The controller receives a cooling request and determines a rate setting for the variable speed compressor based on the cooling request. In response to determining that the rate setting is less than the calculated minimum rate limit, the controller overrides the rate setting and utilizes the minimum rate limit and performs cooling to meet the cooling request.

[0015] A lubricant separator for a heating, ventilation, air conditioning and refrigeration (HVACR) system is disclosed. The lubricant separator includes a first chamber and a second chamber. A conduit is disposed in the first chamber and fluidly connects the first chamber to the second chamber. The first chamber includes an inlet and an outlet, the inlet receiving a high-pressure refrigerant / lubricant mixture and the outlet providing the high-pressure refrigerant. The second chamber receives a lubricant portion of the refrigerant / lubricant mixture through the conduit. The second chamber includes an outlet providing a low-pressure lubricant. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Reference is made to the accompanying drawings which form a part of this disclosure and which illustrate embodiments in which the systems and methods described in this specification may be practiced.

[0017] Figure 1 is a schematic diagram of a refrigerant circuit according to an embodiment.

[0018] Figure 2 is a flow chart of a method for determining a minimum speed limit for a variable speed compressor according to an embodiment.

[0019] Figure 3 is a flow chart of a method for operating a variable speed compressor to maintain a minimum bearing lubricant film thickness according to an embodiment.

[0020] Figure 4 The minimum operating frequency for a variable speed motor in an HVACR system according to an embodiment is shown.

[0021] Figure 5A A lubricant separator according to an embodiment is shown.

[0022] Figure 5B A lubricant separator according to an embodiment is shown.

[0023] Figure 5C A lubricant separator according to an embodiment is shown.

[0024] Like reference numerals refer to like parts hereinafter. DETAILED DESCRIPTION

[0025] The present disclosure generally relates to a heating, ventilation, air conditioning and refrigeration (HVACR) system. More specifically, the present disclosure relates to lubricant quality management for compressors in HVACR systems.

[0026] There is a growing concern about the environmental impact of HVACR refrigerants. For example, since 2011, the European Union has been phasing out refrigerants with a global warming potential (GWP) greater than, for example, 150 in certain refrigeration systems. Environmentally suitable HVACR refrigerants with suitable properties (such as density, vapor pressure, heat of evaporation, and suitable chemical properties) that meet requirements regarding safety and environmental impact (such as the EU standards discussed above) can be used in HVACR systems. Environmentally suitable HVACR refrigerants are non-flammable or mildly flammable, non-ozone depleting, energy efficient, low in toxicity, compatible with building materials, and chemically stable throughout the life of the equipment.

[0027] Current refrigerants such as R134a may have a relatively high GWP. For example, the GWP of R134a is 1430. As a result, alternative refrigerants such as, but not limited to, R1234ze(E), R513A, etc. are being used in HVACR systems.

[0028] When utilizing newer refrigerant compositions such as, but not limited to, R1234ze(E) and R513A, various issues may arise due to the different properties of the refrigerants compared to existing refrigerants such as R134a. Typically, refrigerants with low GWP, such as R1234ze(E), R513A, etc., may be introduced into the lubricant. In some cases, the alternative refrigerant is relatively more miscible in the lubricant than the current refrigerant, resulting in a higher refrigerant concentration in the lubricant (e.g., lubricant dilution).

[0029] As a result, a portion of the operating map of a compressor for an HVACR system may suffer from higher lubricant dilution and limited bearing viscosity due to low discharge superheat. In some cases, the higher lubricant dilution and limited bearing viscosity issues may be more significant when the variable speed compressor is operated at a relatively low speed. Higher lubricant dilution and limited bearing viscosity may result in, for example, a shortened service life of the bearings and ultimately compressor failure. In some cases, replacing the refrigerant with R134a may require replacement of mechanical components (e.g., bearings, etc.) in the compressor.

[0030] In other cases, controlling a variable speed compressor to maximize efficiency may result in lubricant dilution problems even when utilizing current refrigerants such as R134a.

[0031] Typically, lubricants used with R134a replacement refrigerants suffer from higher lubricant dilution issues.The lubricant may include any suitable lubricant that is miscible with the selected replacement refrigerant.

[0032] Generally, higher lubricant dilution may become a problem when the exhaust superheat becomes relatively low. For example, higher lubricant dilution may occur when the exhaust superheat is below or close to 8°C.

[0033] In an embodiment, a minimum rate limit may be set for a variable speed compressor to limit or avoid reaching operating conditions where higher lubricant dilution and limited bearing viscosity are problematic. As a result, existing mechanical components (e.g., bearings, etc.) may be utilized. For example, providing a minimum rate limit for a variable speed compressor may control the pitch rate (average diameter times rate) of the bearings. As a result, the service life of the bearings may be increased. In an embodiment, the minimum rate limit may be selected based on a combination of saturated suction temperature and saturated discharge temperature with compressor frame size. In an embodiment, the compressor frame size may include bearing size and compressor efficiency.

[0034] In an embodiment, the compressor for the HVACR system is a screw compressor.In an embodiment, the screw compressor is a variable speed screw compressor capable of operating at various speeds between a maximum speed and a minimum speed.

[0035] According to an embodiment, a minimum speed for the variable speed compressor may be selected based on the exhaust gas superheat.

[0036] In an embodiment, a minimum speed for the variable speed compressor may be selected based on the saturated suction temperature and the saturated discharge temperature.

[0037] Figure 1 1 is a schematic diagram of a refrigerant circuit 10 according to an embodiment. The refrigerant circuit 10 generally includes a compressor 12, a condenser 14, an expansion device 16, an evaporator 18, and a lubricant separator 150.

[0038] The refrigerant circuit 10 is an example and may be modified to include additional components. For example, in an embodiment, the refrigerant circuit 10 may include other components such as, but not limited to, an economizer heat exchanger, one or more flow control devices, a receiving tank, a dryer, a suction heat exchanger, and the like.

[0039] The refrigerant circuit 10 is generally applicable to various systems for controlling environmental conditions (e.g., temperature, humidity, air quality, etc.) in a space (commonly referred to as a conditioned space). Examples of such systems include, but are not limited to, HVACR systems, transport refrigeration systems, and the like.

[0040] The compressor 12, condenser 14, expansion device 16, and evaporator 18 are fluidly connected by refrigerant lines 20, 22, 24. In embodiments, the refrigerant lines 20, 22, and 24 may alternatively be referred to as refrigerant conduits 20, 22, and 24, or the like.

[0041] In an embodiment, the refrigerant circuit 10 may be configured as a cooling system (eg, an air conditioning system) capable of operating in a cooling mode. In an embodiment, the refrigerant circuit 10 may be configured as a heat pump system capable of operating in a cooling mode and a heating / defrosting mode.

[0042] Refrigerant circuit 10 may operate according to generally known principles. Refrigerant circuit 10 may be configured to heat or cool a gaseous process fluid (eg, a heat transfer medium or fluid such as, but not limited to, air), in which case refrigerant circuit 10 may generally represent an air conditioner or heat pump.

[0043] When in operation, the compressor 12 compresses a working fluid (e.g., a heat transfer fluid such as a refrigerant) from a relatively low pressure gas (e.g., suction pressure) to a relatively high pressure gas (e.g., discharge pressure). In an embodiment, the compressor 12 may be a positive displacement compressor. In an embodiment, the positive displacement compressor may be a screw compressor, a scroll compressor, a reciprocating compressor, etc. In an embodiment, the compressor 12 may be a centrifugal compressor.

[0044] A relatively high pressure gas, which may also be at a relatively high temperature, is discharged from the compressor 12 and flows through the refrigerant line 20 to the condenser 14. The working fluid flows through the condenser 14 and rejects heat to the process fluid (e.g., water, air, etc.), thereby cooling the working fluid. The cooled working fluid, now in liquid form, flows to the expansion device 16 through the refrigerant line 22. The expansion device 16 reduces the pressure of the working fluid. As a result, a portion of the working fluid is converted to a gaseous form. The working fluid, now in a mixed liquid and gaseous form, flows to the evaporator 18 through the refrigerant line 22. The working fluid flows through the evaporator 18 and absorbs heat from the process fluid (e.g., water, air, etc.), heating the working fluid, and converting it to a gaseous form. The gaseous working fluid then returns to the compressor 12 through the refrigerant line 24. The above process continues while the refrigerant circuit is running, for example, in a cooling mode (e.g., while starting the compressor 12).

[0045] The refrigerant circuit 10 may include a lubricant separator 150 disposed between the compressor 12 and the condenser 14. FIG. 5A to FIG. 5C The lubricant separator 150 is shown and described in further detail. The lubricant separator 150 is fluidly connected to the discharge of the compressor 12 via the refrigerant line 20. The lubricant separator 150 is fluidly connected to the compressor 12 to provide fluid to various components (e.g., bearings, etc.) of the compressor 12 via the lubricant return line 28a and optionally via the second lubricant return line 28b. It will be appreciated that the number of lubricant return lines 28a and 28b may be selected based on, for example, which components of the compressor are provided with lubricant.

[0046] Figure 2 is a method for determining a variable speed compressor (eg, Figure 1 Flowchart of method 50 for determining a minimum speed limit for compressor 12 in FIG. 1 . Method 50 may be specific to a selected compressor size. The selected compressor size and corresponding execution of method 50 may be based on, for example, the size of bearings in the compressor and the efficiency requirements of the compressor. According to an embodiment, method 50 may be performed by a controller of the compressor (e.g., Figure 1 In an embodiment, a series of compressors may perform method 50, and the determined minimum rate limit may be included in the control of the compressors. Figure 3 An example of a control method for compressor 12 is shown and described.

[0047] At 52, the suction pressure for the HVACR system is measured. The suction pressure in conjunction with the selected refrigerant (e.g., R-134a, R1234ze(E), R-513A, etc.) can be used to determine the saturated suction temperature. In an embodiment, the suction temperature may alternatively be measured, but assumptions would have to be made regarding the amount of superheat, which may make the determination less accurate than using the suction pressure.

[0048] At 54, the discharge pressure for the HVACR system is measured. The discharge pressure in conjunction with the selected refrigerant (e.g., R-134a, R1234ze(E), R-513A, etc.) can be used to determine the saturated discharge temperature. In embodiments, the discharge temperature may alternatively be measured, but assumptions would have to be made regarding the amount of superheat, which may make the determination less accurate than using suction pressure.

[0049] At 56, the selected saturated suction temperature and the selected saturated discharge temperature are used to determine a minimum rate limit for the variable speed compressor. The minimum rate limit generally depends on the refrigerant, the lubricant, the bearing size in the compressor, and the compressor performance. In an embodiment, as the bearing size decreases, the minimum rate limit increases. For example, the minimum rate limit can be determined by testing and modeling the discharge temperature of the variable speed compressor relative to the bearing cavity temperature for the bearing in the variable speed compressor, and performing a surface fit to determine the minimum rate limit equation. Typically, when the bearing reaches a pitch angle rate of less than or close to 300,000 mm / min, a minimum rate limit may be required to prevent higher lubricant dilution. Therefore, a pitch angle rate of less than or close to 300,000 mm / min can be considered a lower rate, while a pitch angle rate of more than 300,000 mm / min can be considered a higher rate.

[0050] Reference Figure 4 , according to an embodiment, an example minimum motor frequency as determined according to method 50 is shown. Figure 4 Indicates the selected bearing size. It will be appreciated that Figure 4 The minimum motor frequency curve in FIG. 1 depends on the selected refrigerant (e.g., R1234ze(E), etc.), the bearing size, and the selected lubricant. In the figure, the x-axis represents the saturated suction temperature (in °F) and the y-axis represents the saturated discharge temperature (in °F). The motor frequency is represented by various shades from relatively low to relatively high. As shown in the figure, at lower saturated suction temperature and saturated discharge temperature, the minimum motor frequency is relatively low compared to at relatively higher saturated suction temperature and saturated discharge temperature.

[0051] Figure 31 is a flow chart of a method 100 for operating a variable speed compressor to maintain a minimum bearing lubricant film thickness according to an embodiment. The method 100 generally includes operating an HVACR system (e.g., Figure 1 The refrigerant circuit 10 in the embodiment of the present invention.

[0052] Method 100 begins at 102. At 102, a controller (e.g., a thermostat, etc.) determines a cooling requirement. The cooling requirement may be based on a setting in the thermostat, one or more sensors in the conditioning space, a building automation system, and / or an HVACR system (e.g., Figure 1 The controller of the refrigerant circuit 10) etc. is used to determine the refrigerant circuit 10.

[0053] At 104, the controller determines a variable speed compressor setting based on the cooling demand. In an embodiment, this may include a target speed setting for compressor 12. In an embodiment, this may include a speed setting for compressor 12 that is less than its target speed. In an embodiment, the target speed may be a maximum speed.

[0054] At 106, the controller 26 determines whether the determined variable speed compressor setting is less than (e.g., Figure 2 ) minimum rate limit determined by method 50 in .

[0055] At 108 , the controller sets one or more cooling settings for the HVACR system based on the cooling demand and the variable speed compressor setting determined in 104 .

[0056] At 110, if the variable speed compressor setting determined at 104 is less than (e.g., Figure 2 If a minimum speed limit (as determined at method 50 in ), the controller 26 overrides the variable speed compressor setting (eg, as determined at 104) to use the minimum speed limit and cools according to the cooling demand.

[0057] FIG. 5A to FIG. 5C 1 shows a lubricant separator 150 according to an embodiment. In an embodiment, the lubricant separator 150 can be used to inject lubricant into a compressor (e.g., Figure 1 The invention provides heat to the lubricant before it is introduced into the bearing cavity of the compressor 12 in the compressor 12, thereby reducing the problem of higher lubricant dilution in the HVACR system. Generally, a higher temperature refrigerant / lubricant mixture can be used to heat the low pressure lubricant as the refrigerant lubricant mixture flashes to maintain the temperature of the low pressure lubricant at or near the discharge temperature. In an embodiment, for example, heating the low pressure lubricant can reduce the amount of refrigerant present in the lubricant. Thus, the amount of lubricant dilution is reduced.

[0058] In an embodiment, the lubricant separator 150 may be included in the above Figure 2 and Figure 3 In an embodiment, the lubricant separator 150 may be included in an HVACR system that does not include the above Figure 2 and Figure 3 The controlled HVACR system described in.

[0059] In an embodiment, the lubricant separator 150 may be included in a HVACR system including a fixed speed compressor. In an embodiment, the lubricant separator 150 may be included in a HVACR system including a variable speed compressor. In an embodiment, the variable speed compressor may include the minimum speed limiting control described above.

[0060] The lubricant separator 150 includes a housing 150a. The housing 150a of the lubricant separator 150 contains a lubricant reservoir 152. In an embodiment, the lubricant reservoir 152 may be referred to as a lubricant reservoir 152. The lubricant separator 150 includes an inlet 154, and outlets 156a, 156b, and 156c.

[0061] Inlet 154 (e.g., via Figure 1 A refrigerant line 20 in is fluidly connected to the discharge port of the compressor 12.

[0062] Outlet 156a is fluidly connected to the first compressor component. In embodiments, the first compressor component may include components such as, but not limited to, one or more rotors in a screw compressor. For example, when lubricant is injected into the compression pocket during the compression cycle, outlet 156a may be included and may be optional. The fluid connection between outlet 156a and the first compressor component may be through an optional lubricant return line (e.g., Figure 1 The lubricant in the return line 28b).

[0063] The outlet 156b is fluidly connected to a second compressor component. In an embodiment, the second compressor component may include components such as, but not limited to, one or more bearings. The fluid connection between the outlet 156b and the second compressor component may be through a lubricant return line (e.g., Figure 1 The lubricant return line 28a).

[0064] The outlet 156c is connected to the refrigerant line (eg, Figure 1 The refrigerant line 20 in the embodiment of the present invention is fluidly connected to the condenser (e.g., Figure 1 Condenser 14 in.

[0065] The housing 150a may be divided into a separate chamber 158a and a chamber 158b by a partition 160. Optionally, the chamber 158a may be referred to as a high-pressure chamber 158a. Optionally, the chamber 158b may be referred to as a low-pressure chamber 158b. The low-pressure chamber 158b has a relatively lower pressure than the pressure of the high-pressure chamber 158a. In an embodiment, the high-pressure chamber 158a may have a pressure at or near the discharge pressure of the compressor. In an embodiment, the low-pressure chamber 158b has a pressure close to the suction pressure of the compressor.

[0066] In an embodiment, for example, the divider 160 may be a plate or the like. The divider 160 may generally be made of a metal such as, but not limited to, steel, copper, or the like. The divider 160 generally facilitates a heat transfer relationship between the high pressure chamber 158a and the low pressure chamber 158b. Therefore, suitable materials include those materials that facilitate a heat transfer relationship.

[0067] The high pressure chamber 158a receives the high pressure refrigerant / lubricant mixture through the inlet 154. The high pressure gaseous refrigerant portion 162a of the refrigerant / lubricant mixture received through the inlet 154 can be separated from the lubricant portion 162b by, for example, gravity, centrifugation, coalescence, collision with the surface of the outlet 156b, etc. It will be appreciated that the specific separation of the refrigerant / lubricant mixture can occur in various ways, and it is not intended to limit the specific type of separator. The lubricant portion 162b can be collected on the partition 160. It will be appreciated that the refrigerant portion 162a may still have lubricant, but the amount of refrigerant is relatively large relative to the amount of lubricant before separation from the refrigerant / lubricant mixture. Similarly, the lubricant portion 162b may still include refrigerant, but the amount of lubricant is relatively large relative to the amount of refrigerant before separation from the refrigerant / lubricant mixture.

[0068] The conduit 164 fluidly connects the lubricant portion 162b in the high pressure chamber 158a to the lubricant reservoir 152 (low pressure chamber 158b). The conduit 164 may include an expansion device 166 to reduce the pressure of the lubricant moving from the high pressure chamber 158a to the lubricant reservoir 152. Various types of expansion devices 166 may be included. In an embodiment, the expansion device 166 may be a fixed device such as, but not limited to, an orifice. In an embodiment, the expansion device 166 may be various devices such as, but not limited to, an electronic expansion valve (EXV).

[0069] The conduit 164 exchanges heat with the high pressure chamber 158a which is at or near the discharge temperature of the compressor. As a result, the lubricant flowing through the conduit 164 to the lubricant reservoir 152 (low pressure chamber 158b) receives heat. Therefore, the conduit 164 may also be referred to as a heat exchange coil or heat exchanger 164. In an embodiment, the length of the conduit 164 and the corresponding total heat transfer surface area may be controlled to provide heat to the lubricant. Therefore, the conduit 164 may be made of a material such as a metal (such as but not limited to steel, copper, etc.) suitable for facilitating heat exchange.

[0070] The conduit 164 is fluidly connected to the high pressure chamber 158a and the lubricant reservoir 152 (low pressure chamber 158b). Lubricant from the lubricant portion 162b enters the conduit 164 through the expansion device 166 and is provided to the lubricant reservoir 152 (low pressure reservoir 158b).

[0071] A relatively high pressure lubricant (eg, lubricant portion 162b) may be provided from outlet 156a to the first compressor component. Lubricant flowing into the lubricant reservoir (low pressure chamber 158b) may be provided to one or more bearings of compressor 12 through outlet 156b.

[0072] The reduction in the pressure of the lubricant from the expansion device 166 may cause the lubricant in the low-pressure chamber 158b to become a two-phase fluid (e.g., a mixture including a gas and a liquid). As the pressure of the lubricant is reduced, the refrigerant flashes, which also results in cooling of the lubricant. However, due to the heat exchange relationship with the refrigerant / lubricant mixture (via the conduit 164 and the partition 160), the lubricant in the lubricant reservoir 152 (low-pressure chamber 158b) receives heat rejected from the refrigerant / lubricant mixture in the high-pressure chamber 158. For example, the additional heat may reduce the amount of refrigerant in the lubricant.

[0073] In an embodiment, the pressure drop induced by the expansion device 166 may be selected to provide a pressure in the low pressure chamber 158b (lubricant reservoir 152) sufficient to drive lubricant through the lubricant filter and into the injection port of the bearing without requiring a lubricant pump to provide the necessary pressure. The pressure drop may also be selected based on, for example, compressor size and efficiency, flow rate to the bearing, and desired temperature for the lubricant in the lubricant reservoir 152.

[0074] In an embodiment, the arrangement of the lubricant reservoir 152 (low-pressure chamber 158b) integral with the lubricant separator 150 can reduce the complexity relative to a system including a separate lubricant separator 150 and lubricant reservoir 152. In an embodiment, heat present in the high-pressure refrigerant / lubricant mixture can be discharged to the low-pressure lubricant in the lubricant reservoir (low-pressure chamber 158b) through the partition 160. In an embodiment, the heat applied by the partition 160, the conduit 164, or a combination thereof can separate the additional refrigerant from the lubricant, thereby improving the quality of the lubricant, reducing lubricant dilution, and increasing the viscosity of the lubricant.

[0075] Figure 5B According to the embodiment Figure 5A Optional configuration for the configuration provided in . Figure 5B In the lubricant separator 150 of FIG. 1 , the lubricant reservoir 152 (low-pressure chamber 158 b ) is disposed at the top of the housing 150 a. Therefore, the conduit 164 extends upward from the lubricant portion 162 b through the refrigerant portion 162 a and into the lubricant reservoir 152 (low-pressure chamber 158 b ).

[0076] Figure 5C According to the embodiment Figure 5A and Figure 5B Optional configuration for the configuration provided in . Figure 5C In the lubricant separator 150 of the present invention, the lubricant reservoir (low pressure chamber 158b) is disposed outside the housing 150a. The lubricant reservoir 152 (low pressure chamber 158b) may be a conduit surrounding the outlet 156c and receives heat in a heat exchange relationship with the high pressure, high temperature refrigerant leaving the lubricant separator 150. In an embodiment, the lubricant reservoir 152 (low pressure chamber 158b) may be fixed to the lubricant separator 150. In an embodiment, the lubricant reservoir 152 (low pressure chamber 158b) may be a one-piece integral structure with the lubricant separator 150. In an embodiment, the lubricant reservoir 152 (low pressure chamber 158b) may be separated from the lubricant separator 150.

[0077] exist Figure 5C In the embodiment, the conduit 164 is arranged outside the housing 150a. It will be appreciated that in embodiments, the conduit 164 may be arranged inside the housing 150a.

[0078] FIG. 5A to FIG. 5C The embodiment of FIG. 1 generally shows a combined lubricant separator 150 and lubricant reservoir 152. In an embodiment, the lubricant reservoir 152 can be separate from the lubricant separator 150. The lubricant reservoir 152 is generally located at a location in the refrigerant circuit 10 that can exchange heat with the refrigerant at or near the discharge temperature. In an embodiment, the lubricant reservoir 152 can be incorporated into the condenser 14.

[0079] aspect:

[0080] Any one of aspects 1 to 11 may be combined with any one of aspects 12 to 16, aspects 17 to 22, and aspects 23 to 34. Any one of aspects 12 to 16 may be combined with any one of aspects 17 to 22, and aspects 23 to 34. Any one of aspects 17 to 22 may be combined with any one of aspects 23 to 24.

[0081] Aspect 1. A heating, ventilation, air conditioning and refrigeration (HVACR) system includes: a refrigerant circuit, including a fluidly connected compressor, a condenser, an expansion device and an evaporator; a controller, electrically connected to the compressor, the controller being configured to prevent the compressor from operating at a rate less than a minimum rate limit; and a lubricant separator, having an inlet fluidly connected between the compressor and the condenser, and a plurality of outlets, a first outlet of the plurality of outlets being fluidly connected to the condenser, and a second outlet of the plurality of outlets being fluidly connected to one or more components of the compressor to provide lubricant to the one or more components.

[0082] Aspect 2. The HVACR system of aspect 1, wherein the lubricant separator comprises a lubricant reservoir and a partition, the partition dividing the lubricant separator into a high pressure chamber and a low pressure chamber.

[0083] Aspect 3. An HVACR system as described in Aspect 2, wherein the HVACR system further comprises a conduit fluidly connecting the high-pressure chamber and the low-pressure chamber, the conduit having an expansion device, the expansion device being disposed at a position in the high-pressure chamber, at which position the expansion device is disposed in the liquid portion of the lubricant so that the liquid portion can be provided from the conduit to the low-pressure chamber.

[0084] Aspect 4. The HVACR system of aspect 3, wherein the expansion device is sized to induce a pressure drop to reduce the pressure of the lubricant provided to the low pressure chamber.

[0085] Aspect 5. The HVACR system of any one of aspects 1 to 4, wherein the controller is configured to determine the minimum rate limit based on bearing size, efficiency of the compressor, saturated suction temperature, and saturated discharge temperature.

[0086] Aspect 6. The HVACR system of any one of aspects 1 to 5, wherein the controller is configured to override the cooling setting when the cooling setting corresponds to an operating speed of the compressor that is below a minimum speed limit.

[0087] Aspect 7. The HVACR system of any one of aspects 1 to 6, wherein the compressor is a variable speed screw compressor.

[0088] Aspect 8. The HVACR system of aspect 7, wherein the minimum rate limit is for bearing pitch angle rates less than or approaching 300,000 mm / min.

[0089] Aspect 9. The HVACR system of any one of aspects 1 to 8, wherein the HVACR system uses R134a as a refrigerant.

[0090] Aspect 10. The HVACR system of any one of aspects 1 to 8, wherein the HVACR system uses a refrigerant having a relatively lower GWP than that of R134a.

[0091] Aspect 11. The HVACR system of any one of aspects 1 to 8, wherein the HVACR system uses R1234ze(E) or R513A as a refrigerant.

[0092] Aspect 12. A method for controlling a variable speed compressor includes: determining a saturated suction temperature and a saturated discharge temperature using a controller of the variable speed compressor; calculating a minimum rate limit for the variable speed compressor based on the saturated suction temperature and the saturated discharge temperature using the controller of the variable speed compressor; receiving a cooling request through the controller; determining a rate setting for the variable speed compressor based on the cooling request; and in response to determining that the rate setting is less than the calculated minimum rate limit, overwriting the rate setting, utilizing the minimum rate limit and performing cooling to meet the cooling request.

[0093] Aspect 13. The method of aspect 12, wherein, in response to determining that the rate setting is greater than a minimum rate limit, cooling is performed based on the rate setting to meet the cooling requirement.

[0094] Aspect 14. The method of one of aspects 12 or 13, wherein the calculation is based on saturated suction temperature, saturated discharge temperature, bearing size, and compressor efficiency.

[0095] Aspect 15. The method according to any one of aspects 12 to 14, wherein the variable speed compressor uses R1234ze(E) as the refrigerant.

[0096] Aspect 16. The method of any one of aspects 12 to 15, wherein the minimum rate limit is for a bearing pitch angle rate less than or close to 300,000 mm / min.

[0097] Aspect 17. A lubricant separator for a heating, ventilation, air conditioning and refrigeration (HVACR) system comprises: a first chamber; a second chamber; a conduit disposed in the first chamber and fluidly connected to the second chamber, wherein the first chamber comprises an inlet and an outlet, the inlet of the first chamber receives a refrigerant / lubricant mixture, and the outlet of the first chamber provides a refrigerant portion of the refrigerant / lubricant mixture, wherein the second chamber receives the lubricant portion of the refrigerant / lubricant mixture through the conduit, and the second chamber comprises an outlet, and a lubricant having a pressure relatively lower than a pressure of the refrigerant / lubricant mixture is provided through the outlet of the second chamber.

[0098] Aspect 18. The lubricant separator of aspect 17, wherein the second chamber is arranged to be in thermal communication with the first chamber.

[0099] Aspect 19. The lubricant separator according to one of aspects 17 or 18, wherein the second chamber is located outside the lubricant separator.

[0100] Aspect 20. The lubricant separator according to any one of aspects 17 to 19, further comprising a partition, wherein the partition separates the first chamber from the second chamber.

[0101] Aspect 21. The lubricant separator according to any one of aspects 17 to 20, further comprising a second outlet, the second outlet being disposed in the first chamber, and high-pressure lubricant being provided from the second outlet.

[0102] Aspect 22. A lubricant separator as described in any one of aspects 17 to 21, wherein the expansion device of the conduit is sized to reduce the pressure of the lubricant of the conduit entering the first chamber.

[0103] Aspect 23. A heating, ventilation, air conditioning, and refrigeration (HVACR) system comprises: a fluidly connected refrigerant circuit including a compressor, a condenser, an expansion device, and an evaporator; a controller electrically connected to the compressor, the controller configured to prevent the compressor from operating at a rate less than a minimum rate limit.

[0104] Aspect 24. An HVACR system as described in Aspect 23, the HVACR system also includes a lubricant separator, the lubricant separator having an inlet fluidly connected between the compressor and the condenser, and a plurality of outlets, a first outlet of the plurality of outlets being fluidly connected to the condenser, and a second outlet of the plurality of outlets being fluidly connected to one or more components of the compressor to provide lubricant to the one or more components.

[0105] Aspect 25. The HVACR system of aspect 24, wherein the lubricant separator comprises a lubricant reservoir and a partition, the partition dividing the lubricant separator into a high pressure chamber and a low pressure chamber, the high pressure chamber having a relatively higher pressure than the pressure of the low pressure chamber.

[0106] Aspect 26. An HVACR system as described in Aspect 25, the HVACR system also includes a conduit fluidly connecting the high-pressure chamber and the low-pressure chamber, the conduit having an expansion device, the expansion device being arranged at a position in the high-pressure chamber, at which position the expansion device is arranged in the liquid portion of the lubricant so that the liquid portion can be provided from the conduit to the low-pressure chamber.

[0107] Aspect 27. The HVACR system of aspect 26, wherein the expansion device is sized to induce a pressure drop to reduce the pressure of the lubricant provided to the low pressure chamber.

[0108] Aspect 28. The HVACR system of any of aspects 23 to 27, wherein the controller is configured to determine the minimum rate limit based on bearing size, efficiency of the compressor, saturated suction temperature, and saturated discharge temperature.

[0109] Aspect 29. The HVACR system of any of aspects 23 to 28, wherein the controller is configured to override the cooling setting when the cooling setting corresponds to an operating speed of the compressor that is below a minimum speed limit.

[0110] Aspect 30. The HVACR system of any one of aspects 23 to 29, wherein the compressor is a variable speed screw compressor.

[0111] Aspect 31. The HVACR system of aspect 30, wherein the minimum rate limit is for bearing pitch angle rates less than or approaching 300,000 mm / min.

[0112] Aspect 32. The HVACR system of any one of aspects 23 to 31, wherein the HVACR system uses R134a as a refrigerant.

[0113] Aspect 33. The HVACR system of any one of aspects 23 to 31, wherein the HVACR system uses a refrigerant having a relatively lower GWP than that of R134a.

[0114] Aspect 34. The HVACR system of any one of aspects 23 to 31, wherein the HVACR system uses R1234ze(E) or R513A as the refrigerant.

[0115] The terms used in this specification are intended to describe specific embodiments and are not intended to be limiting. Unless otherwise clearly indicated, singular terms also include plural forms. When the terms "comprise" and / or "comprising" are used in the specification, the existence of the stated features, integers, steps, operations, elements and / or parts is listed, but the existence or addition of one or more other features, integers, steps, operations, elements and / or parts is not excluded.

[0116] With respect to the foregoing description, it will be understood that changes in detail, especially as to the materials of construction employed and the shapes and dimensions of the parts, may be made without departing from the scope of the present disclosure. The specification and described embodiments are exemplary only, with the true scope and spirit of the present disclosure being indicated by the claims.

Claims

1. A heating, ventilation, air conditioning and refrigeration (HVACR) system, include: a refrigerant circuit comprising a compressor, a condenser, an expansion device, and an evaporator fluidly connected, and a lubricant separator having an inlet fluidly connected between the compressor and the condenser, and a plurality of outlets, a first outlet of the plurality of outlets being fluidly connected to the condenser, a second outlet of the plurality of outlets being fluidly connected to one or more components of the compressor to provide lubricant to the one or more components, wherein the lubricant separator comprises a lubricant reservoir and a partition, the partition dividing the lubricant separator into a high pressure chamber and a low pressure chamber; and a conduit fluidly connecting the high pressure chamber and the low pressure chamber, the conduit having a second expansion device disposed at a position in the high pressure chamber where the second expansion device is disposed in a liquid portion of the lubricant so that the liquid portion can be provided from the conduit to the low pressure chamber.

2. The heating, ventilation, air conditioning and refrigeration system according to claim 1, It is characterized in that The heating, ventilation, air conditioning and refrigeration system also includes: A controller is electrically connected to the compressor, the controller being configured to prevent the compressor from operating at a speed less than a minimum speed limit.

3. A heating, ventilation, air conditioning and refrigeration system according to claim 1 or 2, It is characterized in that The second expansion device is configured to induce a pressure drop to reduce a pressure of the lubricant provided to the low pressure chamber.

4. A heating, ventilation, air conditioning and refrigeration system according to claim 1 or 2, It is characterized in that The high pressure chamber is configured to perform heat exchange with the low pressure chamber.

5. A heating, ventilation, air conditioning and refrigeration system according to claim 1 or 2, It is characterized in that The heating, ventilation, air conditioning and refrigeration system uses R134a as the refrigerant.

6. A heating, ventilation, air conditioning and refrigeration system according to claim 1 or 2, It is characterized in that The heating, ventilation, air conditioning and refrigeration system uses a refrigerant having a relatively lower GWP than that of R134a.

7. A heating, ventilation, air conditioning and refrigeration system according to claim 1 or 2, It is characterized in that The heating, ventilation, air conditioning and refrigeration system uses R1234ze(E) or R513A as refrigerant.

8. A heating, ventilation, air conditioning and refrigeration system according to claim 1 or 2, Features: The high pressure chamber includes an inlet configured to receive a refrigerant / lubricant mixture and the first outlet configured to provide a refrigerant portion of the refrigerant / lubricant mixture; The low-pressure chamber is configured to receive a lubricant portion of the refrigerant / lubricant mixture through the conduit, and the low-pressure chamber includes the second outlet configured to provide a lubricant having a relatively lower pressure than a pressure of the refrigerant / lubricant mixture.

9. The heating, ventilation, air conditioning and refrigeration system according to claim 1 or 2, wherein, the high-pressure chamber includes a third outlet among the plurality of outlets, and the third outlet is configured to provide high-pressure lubricant.

10. The heating, ventilation, air conditioning and refrigeration system according to claim 1 or 2, wherein, the second expansion device is configured to include inducing a pressure drop to reduce the pressure of the lubricant provided to the low-pressure chamber.

11. A lubricant separator for a heating, ventilation, air conditioning and refrigeration (HVACR) system, the heating, ventilation, air conditioning and refrigeration system including a refrigerant circuit, the lubricant separator comprises: a lubricant reservoir; a separator that divides the lubricant separator into a high-pressure chamber and a low-pressure chamber; a plurality of outlets and inlets, the inlet being fluidly connected between a compressor and a condenser in the refrigerant circuit, a first outlet among the plurality of outlets being configured to be fluidly connected to the condenser, and a second outlet among the plurality of outlets being configured to be fluidly connected to one or more components of the compressor to provide lubricant to the one or more components; and a conduit that fluidly connects the high-pressure chamber and the low-pressure chamber, the conduit having a second expansion device, the second expansion device being disposed at a position in the high-pressure chamber where the second expansion device is disposed in the liquid portion of the lubricant such that the liquid portion can be provided from the conduit to the low-pressure chamber.

12. The lubricant separator according to claim 11, wherein: the high-pressure chamber includes the inlet and the first outlet, the inlet being configured to receive a refrigerant / lubricant mixture, and the first outlet being configured to provide the refrigerant portion of the refrigerant / lubricant mixture; the low-pressure chamber is configured to receive the lubricant portion of the refrigerant / lubricant mixture through the conduit, the low-pressure chamber includes the second outlet, and the second outlet is configured to provide lubricant having a pressure relatively lower than the pressure of the refrigerant / lubricant mixture.

13. The lubricant separator according to claim 11 or 12, wherein, the high-pressure chamber includes a third outlet among the plurality of outlets, and the third outlet is configured to provide high-pressure lubricant.

14. The lubricant separator according to claim 11 or 12, wherein, the second expansion device is configured to include inducing a pressure drop to reduce the pressure of the lubricant provided to the low-pressure chamber.

15. The lubricant separator according to claim 11 or 12, wherein, the high-pressure chamber is arranged to exchange heat with the low-pressure chamber.

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