Patent Application
20220307739
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Chiller systems, or vapor compression systems, utilize a working fluid (e.g., a refrigerant) that changes phases between vapor, liquid, and combinations thereof, in response to exposure to different temperatures and pressures within components of the chiller system. The chiller system may place a working fluid in a heat exchange relationship with a conditioning fluid and may deliver the conditioning fluid to conditioning equipment and/or a conditioned environment of the chiller system. The chiller system may also include a lubricant circuit to direct lubricant (e.g., oil) to certain components, such as a compressor, of the chiller system. However, in some circumstances, a rate at which the lubricant is directed to such components may not be easily controlled, which may impact a performance of the chiller system.
A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.
In one embodiment, a heating, ventilation, air conditioning, and/or refrigeration (HVAC&R) system includes a refrigerant circuit configured to flow a refrigerant therethrough, a sump configured to direct a lubricant to a compressor positioned along the refrigerant circuit, an ejector configured to direct the lubricant from the refrigerant circuit to the sump, and an expansion device positioned along the refrigerant circuit and configured to reduce a pressure of the refrigerant directed through at least a portion of the refrigerant circuit. The HVAC&R system further includes a controller configured to adjust operation of the HVAC&R system between a first mode and a second mode, in which the controller is configured to instruct the expansion device to adjust to a first position to enable the ejector to direct the lubricant from the refrigerant circuit to the sump at a first target flow rate in the first mode, and the controller is configured to instruct the expansion device to adjust to a second position to enable the ejector to direct the lubricant from the refrigerant circuit to the sump at a second target flow rate in the second mode.
In another embodiment, a heating, ventilation, air conditioning, and/or refrigeration (HVAC&R) system includes a refrigerant circuit, a lubricant circuit, and a sump positioned along the lubricant circuit, in which the sump is configured to direct lubricant to the refrigerant circuit. The HVAC&R system further includes an ejector positioned along the lubricant circuit, in which the ejector is configured to direct the lubricant from the refrigerant circuit to the sump, the ejector is configured to receive a first fluid flow from a condenser positioned along the refrigerant circuit via an inlet of the ejector in a first mode of operation of the HVAC&R system, and the ejector is configured to receive a second fluid flow from a compressor positioned along the refrigerant circuit via the inlet of the ejector in a second mode of operation of the HVAC&R system.
In another embodiment, a heating, ventilation, air conditioning, and/or refrigeration (HVAC&R) system includes a refrigerant circuit, an expansion device positioned along the refrigerant circuit, a sump configured to direct lubricant to the refrigerant circuit, and an ejector configured to draw the lubricant from the refrigerant circuit. The expansion device is configured to reduce a pressure of refrigerant directed through at least a portion of the refrigerant circuit and the ejector is configured to receive a first fluid flow from a condenser positioned along the refrigerant circuit in a first mode of operation of the HVAC&R system, and to receive a second fluid flow from a compressor positioned along the refrigerant circuit in a second mode of operation of the HVAC&R system. The HVAC&R system further includes a controller configured to transition the HVAC&R system between the first mode of operation and the second mode of operation, in which the controller is configured to adjust a position of the expansion device to adjust the pressure of the refrigerant to a first pressure level in the first mode of operation, and to adjust the pressure of the refrigerant to a second pressure level in the second mode of operation, in which the second pressure level is less than the first pressure level.
Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which:
One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.
Embodiments of the present disclosure relate to an HVAC&R system having a refrigerant circuit and a lubricant circuit configured to direct lubricant to components (e.g., a compressor) of the refrigerant circuit. For example, the refrigerant circuit may include various components that operate to condition a refrigerant directed through the refrigerant circuit, and the refrigerant circuit may place the refrigerant in a heat exchange relationship with a conditioning fluid to heat and/or cool the conditioning fluid. The lubricant circuit may direct the lubricant to the components of the refrigerant circuit to facilitate and/or improve operation of the components, such as by improving movement of the components and/or by reducing friction between moving features of the components, in order to improve a performance, such as an efficiency and/or a structural longevity, of the refrigerant circuit to condition the refrigerant.
In some embodiments, the lubricant circuit includes a sump configured to direct the lubricant to a component positioned along the refrigerant circuit of the HVAC&R system. The lubricant circuit may also include an ejector configured to draw a flow of the lubricant from the refrigerant circuit to return the lubricant to the sump, thereby enabling the sump to re-supply the lubricant to another component to further facilitate operation of the refrigerant circuit. Unfortunately, in some circumstances, the lubricant may accumulate within various components of the refrigerant circuit and, under some operating conditions, a sufficient flow rate of the lubricant is not directed back to the sump. Accordingly, the sump may not include a sufficient amount of the lubricant to supply to components of the refrigerant circuit at a desirable rate, thereby impacting a performance of the HVAC&R system.
Accordingly, it is now recognized that increasing the rate at which the lubricant returns to the sump may improve the performance of the HVAC&R system. Thus, embodiments of the present disclosure are directed to adjusting operation of various components of the HVAC&R system to increase the rate at which the lubricant flows from the refrigerant circuit, such as from a section of the refrigerant circuit where accumulation of the lubricant is not desirable, to the sump. The sump may then readily supply the lubricant to another section of the refrigerant circuit where the flow of lubricant is desirable. In certain embodiments, the HVAC&R system may be configured to transition between operating in a first operating mode (e.g., a normal operating mode) and a second operating mode (e.g., a lubricant return mode) based on feedback indicative of an operating parameter of the HVAC&R system so as to direct the lubricant from the refrigerant circuit to the sump at a different rates. As an example, a controller may instruct the HVAC&R system to operate in the lubricant return mode upon receiving feedback indicative that an amount (e.g., a fluid volume, a level) of lubricant in the sump is below a threshold amount. In the lubricant return mode, a speed of a compressor, a position of a diffuser ring, and/or a position of an expansion device of the HVAC&R system may be adjusted to increase the rate at which the lubricant is directed from the refrigerant circuit to the sump. Although the present disclosure is primarily discussed with reference to a chiller system, the techniques described herein may be implemented with any suitable HVAC&R system, such as a direct expansion system, a heat pump, and so forth.
Turning now to the drawings,
Some examples of fluids that may be used as refrigerants in the vapor compression system 14 are hydrofluorocarbon (HFC) based refrigerants, for example, R-410A, R-407, R-134a, hydrofluoro-olefin (HFO), “natural” refrigerants like ammonia (NH3), R-717, carbon dioxide (CO2), R-744, or hydrocarbon based refrigerants, water vapor, refrigerants with low global warming potential (GWP), or any other suitable refrigerant. In some embodiments, the vapor compression system 14 may be configured to efficiently utilize refrigerants having a normal boiling point of about 19 degrees Celsius (66 degrees Fahrenheit or less) at one atmosphere of pressure, also referred to as low pressure refrigerants, versus a medium pressure refrigerant, such as R-134a. As used herein, “normal boiling point” may refer to a boiling point temperature measured at one atmosphere of pressure.
In some embodiments, the vapor compression system 14 may use one or more of a variable speed drive (VSDs) 52, a motor 50, the compressor 32, the condenser 34, the expansion valve or device 36, and/or the evaporator 38. The motor 50 may drive the compressor 32 and may be powered by a variable speed drive (VSD) 52. The VSD 52 receives alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source, and provides power having a variable voltage and frequency to the motor 50. In other embodiments, the motor 50 may be powered directly from an AC or direct current (DC) power source. The motor 50 may include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source, such as a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor, or another suitable motor.
The compressor 32 compresses a refrigerant vapor and delivers the vapor to the condenser 34 through a discharge passage. In some embodiments, the compressor 32 may be a centrifugal compressor. The refrigerant vapor delivered by the compressor 32 to the condenser 34 may transfer heat to a cooling fluid (e.g., water or air) in the condenser 34. The refrigerant vapor may condense to a refrigerant liquid in the condenser 34 as a result of thermal heat transfer with the cooling fluid. The refrigerant liquid from the condenser 34 may flow through the expansion device 36 to the evaporator 38. In the illustrated embodiment of
The refrigerant liquid delivered to the evaporator 38 may absorb heat from another cooling fluid, which may or may not be the same cooling fluid used in the condenser 34. The refrigerant liquid in the evaporator 38 may undergo a phase change from the refrigerant liquid to a refrigerant vapor. As shown in the illustrated embodiment of
An HVAC&R system may include a lubricant circuit that is configured to direct a lubricant to certain components of a refrigerant circuit of the HVAC&R system. The lubricant may enhance a performance of the components, such as by reducing friction between moving features of the components. The lubricant circuit may include a sump configured to receive the lubricant from and supply the lubricant to the refrigerant circuit. The lubricant circuit may also include an ejector configured to draw the lubricant from the refrigerant circuit and direct the refrigerant into the sump by establishing a pressure differential between a location along the refrigerant circuit and an interior of the sump. In some cases, the amount of lubricant in the sump may fall below a threshold amount. For instance, a pressure differential established by the ejector may not be sufficient to return the lubricant to the sump at a target flow rate (e.g., relative to a flow rate at which the lubricant is directed out of the sump). As such, the HVAC&R system may be configured to operate in a lubricant return mode, in which the operation of certain components of the HVAC&R system is adjusted to increase the pressure differential generated by the ejector and thus, increase a flow rate of the lubricant back to the sump.
In some cases, the lubricant mixes with the refrigerant within the compressor 106 and is directed through the refrigerant circuit 104, such as to the condenser 108 and/or to the evaporator 112. In order to return the lubricant back to the sump 102, the lubricant circuit 101 includes an ejector 116. For example, the lubricant circuit 101 may include a condenser line 118 fluidly coupling the condenser 108 to a first input or inlet 120 of the ejector 116. The lubricant circuit 101 may also include an evaporator line 122 fluidly coupling the evaporator 112 to a second input or inlet 124 of the ejector 116. The lubricant circuit 101 may further include a return line 126 coupling an outlet 128 of the ejector 116 to the sump 102. In some embodiments, a pressure differential between the condenser 108 and an interior of the ejector 116 may cause high pressure vapor or gas, such as lubricant vapor and/or refrigerant vapor that has not condensed within the condenser 108, to flow from the condenser 108 through the condenser line 118 to the first input 120 of the ejector 116.
The movement of the high pressure vapor into the ejector 116 may also create a suction pressure in the evaporator line 122 that draws liquid, such as refrigerant liquid and/or lubricant liquid, from the evaporator 112 into the second input 124 of the ejector 116. For example, high pressure vapor from the condenser 108 may expand within the ejector 116 and generate a low pressure (e.g., a vacuum), which drives or draws liquid from within the evaporator 112 to flow toward the second input 124 via the evaporator line 122. The high pressure vapor from the condenser 108 and the liquid from the evaporator 112 may combine and/or mix within the ejector 116 and flow through the outlet 128 of the ejector 116 into the sump 102 via the return line 126. In certain embodiments, the lubricant circuit 101 may additionally include a separator (e.g., a flash vessel) configured to separate the lubricant from the refrigerant. For instance, the separator may include a vessel that rapidly reduces a pressure of a mixture of the lubricant and refrigerant. As such, the separator may direct refrigerant vapor to the compressor 106 and/or to another suitable location along the refrigerant circuit 104, and the separator may direct the lubricant into the sump 102. As such, the sump 102 may primarily contain the lubricant, rather than refrigerant.
Generally, increasing pressurization of the refrigerant via the compressor 106 may increase the pressure of the refrigerant in the condenser 108, thereby increasing a flow rate at which refrigerant and/or lubricant are directed from the condenser 108 toward the ejector 116. The increased flow rate may increase a pressure differential between the evaporator 112 and the ejector 116 to increase the rate at which refrigerant and/or lubricant are drawn into the ejector 116 from the evaporator 112. Accordingly, increasing a pressure of the refrigerant discharged from the compressor 106 may increase the flow rate of the lubricant directed from the refrigeration circuit 104 to the ejector 116 and/or to the sump 102. Therefore, an increased amount of lubricant may accumulate within the sump 102 to enable sufficient lubrication of the components of the HVAC&R system 100 and improve performance of the HVAC&R system 100.
Under some operating conditions, the lubricant may not be returned to sump 102 at a rate that enables sufficient lubrication of the compressor 106. For example, a low pressure differential between the condenser 108 and the evaporator 112 may cause a low flow rate of the lubricant (and/or a mixture of refrigerant and lubricant) from the refrigerant circuit 104 into the ejector 116, such that a liquid level of lubricant within the sump 102 decreases. As such, the sump 102 (e.g., the pump 111) may not be able to supply a sufficient amount (e.g., a mass flow rate) of the lubricant to the compressor 106. To increase the liquid level of the lubricant within the sump 102, the HVAC&R system 100 may transition between a normal operating mode (e.g., an operating mode to effectively satisfy a load demand of the HVAC&R system 100) to a lubricant return operating mode (e.g., an operating mode to effectively increase lubricant flow to the sump 102).
In some embodiments, operation of the HVAC&R system 100 in the lubricant return operating mode may increase the concentration of lubricant liquid in the evaporator 112. In other words, the lubricant return operating mode may adjust operation of the HVAC&R system 100 to enable the heat transfer between the conditioning fluid and the refrigerant to vaporize a greater amount of refrigerant (e.g., of the refrigerant and lubricant mixture) in the evaporator 112 relative to that in the normal operating mode of the HVAC&R system 100. For example, the evaporating temperature of the refrigerant in the evaporator 112 during the lubricant return operating mode may be substantially lower than the evaporating temperature in the evaporator 112 during the normal operating mode to enable a greater amount of refrigerant to evaporate with substantially the same amount of heat transfer and without substantially increasing evaporation of the lubricant liquid. In this manner, less refrigerant liquid accumulates within the evaporator 112 during the lubricant return operating mode, thereby increasing a concentration of lubricant liquid in the evaporator 112. As such, if the flow rate at which the lubricant and/or refrigerant mixture is directed from the evaporator 112 to the ejector 116 during the lubricant return operating mode is substantially the same as that during the normal operating mode, the increased concentration of lubricant in the evaporator 112 may enable an increased amount (e.g., an increased volumetric flow rate) of lubricant to return to the sump 102 during the lubricant return operating mode.
To this end, a position of the expansion device 110 may be adjusted to reduce a pressure within the evaporator 112 and therefore also reduce the evaporating temperature of the refrigerant. As an example, the position of the expansion device 110 may be adjusted such that the evaporating temperature of the refrigerant in the lubricant return operating mode is between 1 degrees Celsius and 5 degrees Celsius below the evaporating temperature of the refrigerant in the normal operating mode. In certain embodiments, the position of the expansion device 110 may be adjusted automatically (e.g., electronically), such as via a controller 130 communicatively coupled to the expansion device 110. The controller 130 may include a memory 132 and a processor 134. The memory 132 may be a mass storage device, a flash memory device, removable memory, or any other non-transitory computer-readable medium that includes instructions for controlling of the HVAC&R system 100. The memory 132 may also include volatile memory, such as randomly accessible memory (RAM) and/or non-volatile memory, such as hard disc memory, flash memory, and/or other suitable memory formats. The processor 134 may execute the instructions stored in the memory 132, such as instructions to adjust the position of the expansion device 110.
It should be noted that, in some circumstances, the HVAC&R system 100 may operate more efficiently and/or desirably in the normal operating mode than in the lubricant return operating mode, such as to provide a desirable amount of cooling to the conditioning fluid more efficiently. By way of example, the HVAC&R system 100 may operate more efficiently in the normal operating mode when components of the refrigerant circuit 104 receive an adequate amount or flow rate of the lubricant. However, in other circumstances, the HVAC&R system 100 may operate more efficiently and/or desirably in the lubricant return operating mode than in the normal operating mode. For example, the HVAC&R system 100 may operate more efficiently in the lubricant return operating mode when components of the refrigerant circuit 104 are otherwise not receiving an adequate amount of lubricant. Therefore, the controller 130 may operate the HVAC&R system 100 in a particular operating mode based on an operating parameter to enable the HVAC&R system 100 to operate efficiently.
For example, the operating parameter may include an amount of liquid (e.g., lubricant liquid) in the sump 102, as detected by a liquid level indicator 136 of the sump 102. The controller 130 may be communicatively coupled to the liquid level indicator 136 and may be configured to adjust operation of the HVAC&R system 100 (e.g., between the normal operating mode and the lubricant return operating mode) based on the amount of liquid in the sump 102, as indicated by the liquid level indicator 136. As an example, if the liquid level indicator 136 provides feedback indicative of the amount of liquid in the sump 102 being below a threshold level, the controller 130 may transmit a signal to adjust one or more components the HVAC&R system 100 (e.g., the expansion device 110 and/or the compressor 106) to initiate operation in the lubricant return operating mode. In additional or alternative embodiments, the controller 130 may transmit a signal to adjust operation of the one or more components of the HVAC&R system 100 based on feedback indicative of another operating parameter, such as a temperature and/or pressure of the refrigerant in the refrigerant circuit 104, a concentration of lubricant in the refrigerant circuit 104 (e.g., in the evaporator 112), a pressure of the refrigerant in the condenser 108, an operating parameter associated with operation of the compressor 106, an interval of time, another suitable operating parameter, or any combination thereof. In further embodiments, the controller 130 may receive user feedback (e.g., a user input) that instructs the controller 130 to operate the HVAC&R system 100 in the lubricant return operating mode. That is, an operator of the HVAC&R system 100 may input a target level of lubricant in the sump 102, and the controller 130 may transmit a signal to adjust the one or more components of the HVAC&R system 100 to initiate the lubricant return operating mode based on the target level input by the operator.
At block 162, the controller 130 receives feedback indicative of operation of the HVAC&R system 100 in the lubricant return operating mode. The feedback may be indicative that a level of lubricant in the sump 102 is below a threshold level, and the feedback may be received by the controller 130 from the liquid level indicator 136. The feedback may additionally or alternatively be indicative of another operating parameter and may be transmitted by another suitable sensor of the HVAC&R system 100, for example. The feedback may further include a user input transmitted by an operator of the HVAC&R system 100 and indicative of a target level of lubricant in the sump 102, such that the HVAC&R system 100 transitions to the lubricant return operating mode (e.g., to override a current operation in the normal operating mode).
In response to determining that the HVAC&R system 100 should operate in the lubricant return operating mode, the controller 130 may transmit a signal to adjust the position of the expansion device 110 to reduce an evaporating temperature of the refrigerant in the evaporator 112, as shown at block 164. For example, the controller 130 may transmit a signal to adjust the position of the expansion device 110 to reduce the pressure of the refrigerant directed to the evaporator 112 to a pressure that is lower than that during the normal operating mode. However, the temperature of the conditioning fluid exiting the evaporator 112 in the lubricant return operating mode may remain substantially the same compared to that in the normal operating mode. By way of example, a target evaporator outlet temperature of the conditioning fluid exiting the evaporator 112 after exchanging heat with the refrigerant may remain substantially the same in the lubricant return operating mode as that in the normal operating mode. For instance, the evaporating temperature of the refrigerant in the lubricant return operating mode may be reduced to 4 degrees Celsius, 3 degrees Celsius, 2 degrees Celsius, or another suitable temperature. Further, the evaporator outlet temperature of the conditioning fluid may remain, relative to an evaporator outlet temperature of the condition fluid in the normal operating mode, at 6 degrees Celsius, 7 degrees Celsius, 8 degrees Celsius, or another suitable temperature. In this way, during the lubricant return operating mode, a temperature differential (e.g., a small temperature differential) between the evaporating temperature of the refrigerant and the evaporator outlet temperature of the conditioning fluid may increase. By increasing such temperature differential, an increased amount of refrigerant may be vaporized in the evaporator 112 to accumulate a greater concentration of lubricant liquid in the evaporator 112. As a result, a flow of the liquid drawn into the ejector 116 contains a greater amount of lubricant to thereby increase the level of lubricant within the sump 102. In some embodiments, the lubricant return operating mode includes a first target flow rate of lubricant into the sump 102, and the controller 130 is configured to instruct the expansion device 110 to adjust to a first position based on the first target flow rate.
At block 166, the controller 130 receives feedback indicative of operation of the HVAC&R system 100 in the normal operating mode. For example, the feedback may be received from the liquid level indicator 136 and may indicate that the level of lubricant in the sump 102 is at or above the threshold level. The feedback may additionally or alternatively be indicative of another operating parameter and/or may include a user input (e.g., to override current operation in the lubricant return operating mode) transmitted by the operator of the HVAC&R system 100.
To transition from the lubricant return operating mode to the normal operating mode, the controller 130 may transmit a signal to adjust the position of the expansion device 110 to increase the pressure of the refrigerant directed to the evaporator 112, thereby increasing the evaporating temperature of the refrigerant in the evaporator 112, as shown at block 168. That is, the controller 130 may transmit a signal to adjust the expansion device 110 to increase the pressure within the evaporator 112. In certain implementations, the normal operating mode may include a second target flow rate of lubricant into the sump 102 that is less than the first target flow rate of lubricant into the sump 102. The controller 130 may be configured to instruct the expansion device 110 to adjust to a second position to achieve the second target flow rate of lubricant into the sump 102 by increasing the pressure within the evaporator 112. In some cases, increasing the pressure within the evaporator 112 may reduce an amount of lubricant liquid directed to the sump 102, but the HVAC&R system 100 may cool the conditioning fluid more efficiently than during operation in the lubricant return operating mode.
To operate the HVAC&R system 100 in the lubricant return operating mode, the controller 130 may block fluid flow (e.g., a first fluid flow) through the condenser line 118 to the first input 120 and/or enable fluid flow (e.g., a second fluid flow) through the compressor line 200 to the first input 120. In some embodiments, a first valve 202 may be positioned along the condenser line 118, and a second valve 204 may be positioned along the compressor high pressure line 200. In the normal operating mode, the controller 130 may open the first valve 202 to enable high pressure vapor to flow from the condenser 108 to the ejector 116 and may close the second valve 204 to block high pressure vapor from flowing from the compressor 106 to the ejector 116. In the lubricant return operating mode, the controller 130 may open the second valve 204 to enable high pressure vapor to flow from the compressor 106 to the ejector 116 and may close the first valve 202 to block high pressure vapor from flowing from the condenser 108 to the ejector 116. In additional or alternative lubricant return operating modes, the controller 130 may transmit a signal to alternatively enable an amount of high pressure vapor to flow through both the compressor line 200 and the condenser line 118 simultaneously.
In certain embodiments, the first valve 202 and/or the second valve 204 may each include on-off valves configured to transition between a fully open position to enable fluid flow and a fully closed position to block fluid flow through the respective lines 118, 200. As such, the first valve 202 and/or the second valve 204 may not be configured to transition to an intermediate position between the fully open position and the fully closed position to enable high pressure vapor to flow at a particular rate. In other embodiments, the first valve 202 and/or the second valve 204 may each be configured to transition to a position between the fully open position and the fully closed position in order to control the flow rate of high pressure vapor flowing to the ejector 116 through the respective lines 118, 200. The first valve 202 and/or the second valve 204 may each include solenoid valves configured to actuate to a specific position based on receiving an electrical signal (e.g., a voltage signal) from the controller 130. As such, the controller 130 may be configured to transmit a signal to the first valve 202 and/or the second valve 204 to transition operation of the HVAC&R system 100 between the normal operating mode and the lubricant return operating mode. For instance, the first valve 202 and/or the second valve 204 may each be configured to transition to the closed position upon receiving a respective signal from the controller 130.
Thus, the controller 130 may transmit an electrical signal to the first valve 202 to close the first valve 202 and block high pressure vapor from flowing to the first input 120 of the ejector 116 via the condenser line 118 to operate the HVAC&R system 100 in the lubricant return operating mode. The controller 130 may also interrupt or discontinue an electrical signal from being transmitted to the second valve 204 in the lubricant return operating mode to position the second valve 204 in the open position and enable high pressure vapor to flow to the first input 120 of the ejector 116 via the compressor line 200. Moreover, the controller 130 may transmit another electrical signal to the second valve 204 to close the second valve 204 and block high pressure vapor from flowing to the first input 120 via the compressor line 200 to operate the HVAC&R system 100 in the normal operating mode. The controller 130 may also interrupt or discontinue the electrical signal from being transmitted to the first valve 202 in the normal operating mode to position the first valve 202 in the open position and enable high pressure vapor to flow to the first input 120 via the condenser line 118.
Additionally or alternatively, the controller 130 may be communicatively coupled to the compressor 106 and may be configured to adjust various components of the compressor 106 to control the pressure of the high pressure vapor directed to the ejector 116 via the compressor line 200. For instance,
The compressor 106 may further include a diffuser ring 242 configured to adjust a geometry (e.g., a cross-sectional area) of the diffusion passage 238. As an example, the diffuser ring 242 may be configured to move in a first direction 244 to reduce the cross-sectional area of the diffusion passage 238 and configured to move in a second direction 246 to increase the cross-sectional area of the diffusion passage 238. Reducing the cross-sectional area of the diffusion passage 238 increases a pressure in an area 248 of the compressor 106 upstream of the diffuser ring 242 with respect to the flow direction 240 of the fluid, thereby increasing a pressure of fluid flowing through the diffusion passage 238.
The compressor line 200 may be fluidly coupled to the diffusion passage 238 proximate to the area 248 to enable at least a portion of the fluid (e.g., high pressure refrigerant and/or lubricant) flowing through the diffusion passage 238 to flow through the compressor line 200 (e.g., when the second valve 204 is in the open position). That is, as fluid flows through the diffusion passage 238, a first portion of the fluid may flow past the diffuser ring 242 through the diffusion passage 238, and a second portion of the fluid may flow through the compressor line 200 toward the ejector 116. As the diffuser ring 242 moves in the first direction 244 to reduce the geometry of the diffusion passage 238, the pressure of the fluid may increase in the area 248. As a result, the fluid directed through the compressor line 200 and into the first input 120 may have an increased pressure that drives or draws the lubricant to flow from the evaporator 112 to the second input 124 at an increased flow rate. Therefore, moving the diffuser ring 242 in the first direction 244 may increase the flow rate of the lubricant directed into the sump 102. Thus, the controller 130 may be configured to transmit a signal to adjust a position of the diffuser ring 242 in the first direction 244 to decrease the cross-sectional area of the diffusion passage 238 and increase the pressure of fluid directed to the ejector 116 in order to operate the HVAC&R system 100 in the lubricant return operating mode.
In additional or alternative embodiments, the controller 130 may transmit a signal to adjust a rotational speed of the impeller 230 in the lubricant return operating mode. For example, the controller 130 may transmit a signal to increase the rotational speed of the impeller 230, such that fluid may flow into the diffusion passage 238 at a greater rate to increase a flow rate of the fluid and/or a pressure of the fluid in the area 248. The increased pressure at the area 248 may also increase the pressure of the fluid directed to the first input 120 of the ejector 116 to enable a greater amount of lubricant to be drawn from the evaporator 112 via the ejector 116.
In some implementations, the controller 130 may be configured to increase the pressure in the area 248 to a target pressure level. To this end, the controller 130 may be communicatively coupled to a sensor 250 configured to determine a current pressure level in the area 248. Thus, the controller 130 may receive sensor data indicative of the current pressure level from the sensor 250, compare the current pressure level with the target pressure level, and transmit a signal to adjust the position of the diffuser ring 242 and/or the rotational speed of the impeller 230 accordingly to achieve the target pressure level.
At block 262, the controller 130 receives feedback indicative of operation of the HVAC&R system 100 in the lubricant return operating mode. The feedback may include an operating parameter, such as liquid level in the sump 102 (e.g., received from the liquid level indicator 136), a temperature and/or pressure of the refrigerant in the refrigerant circuit 104, a concentration of lubricant in the refrigerant circuit 104, a pressure in the condenser 108, an operating parameter associated with operation of the compressor 106, an interval of time, another suitable operating parameter, or any combination thereof. The feedback may also include a user input (e.g., received via a user interface of the HVAC&R system 100) to override a current operation of the HVAC&R system 100.
At block 264, the controller 130 transmits a signal to adjust the position of the first valve 202 and/or the second valve 204 of the lubricant circuit 101 in response to receipt of the feedback to operate the HVAC&R system 100 in the lubricant return operating mode. In certain embodiments, the controller 130 may instruct the second valve 204 to open to enable fluid flow through the compressor line 200 and may instruct the first valve 202 to close to block fluid flow through the condenser line 118. In other embodiments, the controller 130 may enable some fluid flow through the condenser line 118 in addition to the fluid flow through the compressor line 200.
At block 266, the controller 130 may also transmit a signal to increase the pressure at the area 248 of the diffusion passage 238 in the compressor 106. As mentioned above, the controller 130 may increase the pressure at the area 248 by transmitting a signal to move the diffuser ring 242 in the first direction 244 to decrease a cross-sectional area of the diffusion passage 238 and/or may transmit a signal to increase a rotational speed of the impeller 230. In certain embodiments, the controller 130 may instruct the diffuser ring 242 to move in the first direction 244 to a target position and/or may instruct the impeller 230 to rotate at a target speed to achieve a target pressure of the refrigerant in the area 248.
At block 268, the controller 130 receives feedback indicative of operation of the HVAC&R system 100 in the normal operating mode. That is, the controller 130 may receive feedback indicative of an operating parameter (e.g., a level of lubricant in the sump 102) and/or a user input to operate the HVAC&R system 100 in the normal operating mode. To transition from the lubricant return operating mode to the normal operating mode, the controller 130 may transmit a signal to adjust the positions of the first valve 202 and the second valve 204, as shown at block 270. For example, the controller 130 may transmit a signal to adjust the second valve 204 to the closed position to block fluid flow through the compressor line 200 and/or to adjust the first valve 202 to an open position to enable fluid flow through the condenser line 118. As a result, the first input 120 of the ejector 116 may receive high pressure fluid from the condenser 108.
Additionally or alternatively, the controller 130 may transmit a signal to decrease the pressure at the area 248, as shown at block 272. By way of example, the controller 130 may transmit a signal to adjust the diffuser ring 242 to move in the second direction 246 to increase the cross-sectional area of the diffusion passage 238 and/or instruct the impeller 230 to rotate at a reduced rotational speed. The position of the diffuser ring 242 and/or the rotational speed of the impeller 230 in the normal operating mode may be based on the feedback, such as an amount of lubricant in the sump 102. Decreasing the pressure at the area 248 may reduce a rate at which lubricant is directed from the refrigerant circuit 104 to the sump 102, but may enable the HVAC&R system 100 to operate (e.g., to cool the conditioning fluid) more efficiently, for example.
Embodiments of the present disclosure are directed to an HVAC&R system that includes a lubricant circuit for circulating a lubricant to components of the HVAC&R system. The lubricant circuit may include a sump configured to direct the lubricant to a refrigerant circuit (e.g., to a compressor) of the HVAC&R system. The lubricant circuit may further include an ejector configured to draw liquid that contains the lubricant from the refrigerant circuit (e.g., from an evaporator) to the sump. For example, a high pressure vapor (e.g., from a condenser) may be directed to the ejector to generate a suction force (e.g., a vacuum or reduced pressure) that draws the liquid (e.g., from an evaporator) toward the sump. In some embodiments, the ejector may not adequately draw the lubricant into the sump, such that a lubricant level in the sump decreases. As such, the HVAC&R system may transition operating modes to a lubricant return operating mode.
In the lubricant return operating mode, a position of an expansion device of the HVAC&R system may be adjusted such that the evaporating temperature of the refrigerant is decreased and/or a pressure within the evaporator decreases. As such, a concentration of lubricant drawn by the ejector may increase, and the flow rate at which the lubricant is directed into the sump may increase. In additional or alternative embodiments, during the lubricant return operating mode, the high pressure vapor entering the ejector may be directed from an intake of the compressor of the HVAC&R system. Furthermore, operation of the compressor may be adjusted to increase the pressure of the fluid directed toward the ejector, which may increase the flow rate at which liquid is drawn by the ejector and directed into the sump. The technical effects and technical problems in the specification are examples and are not limiting. It should be noted that the embodiments described in the specification may have other technical effects and can solve other technical problems.
While only certain features and embodiments of the disclosure have been illustrated and described, many modifications and changes may occur to those skilled in the art (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters (e.g., temperatures, pressures, etc.), mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the disclosure. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described (i.e., those unrelated to the presently contemplated best mode of carrying out the disclosure, or those unrelated to enabling the claimed disclosure). It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.
This application claims priority from and the benefit of U.S. Provisional Application Ser. No. 62/862,536, entitled “LUBRICATION SYSTEM FOR A COMPRESSOR,” filed Jun. 17, 2019, which is hereby incorporated by reference in its entirety for all purposes.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2020/037291 | 6/11/2020 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 62862536 | Jun 2019 | US |
