Patent Description:
Refrigeration systems are used in a variety of settings and for many purposes. For example, refrigeration systems may include a vapor compression refrigeration cycle, which may have a condenser, an evaporator, a compressor, a sump, and/or an expansion device. Some systems include a lubricant (e.g., oil) that circulates through the compressor and the sump to provide lubrication for the compressor. As the lubricant circulates, refrigerant within the compressor may mix with the lubricant. The mixture may cause reduced performance of the compressor (e.g., the mixture may not properly lubricate certain components of the compressor and/or may produce foaming in certain components due to pressure reduction or temperature increase) and the mechanical cooling system generally. Additionally, the lubricant circulating back to the compressor from the sump may include characteristics that may further reduce a performance of the compressor and/or the mechanical cooling system.

For example, <CIT> relates to a conventional vapor compression system having a compressor configured to circulate refrigerant through a refrigerant loop, an oil sump configured to receive a mixture of lubricant and the refrigerant from the compressor, and a controller comprising a memory and a processor. The processor is configured to receive signals indicative of a temperature of the mixture and the pressure of the mixture.

Further conventional vapor compression systems are disclosed in <CIT> and <CIT>.

As discussed above, a vapor compression system generally includes a refrigerant flowing through a refrigeration circuit. The refrigerant flows through multiple conduits and components disposed along the refrigeration circuit, while undergoing phase changes to enable the vapor compression system to condition an interior space of a structure. The vapor compression system generally includes a lubrication circuit (e.g., an oil circuit) flowing through certain components of the refrigeration circuit (e.g., a compressor, a sump, and a cooler) to provide lubrication for a compressor of the refrigeration circuit during operation. As lubricant flows through the lubrication circuit, the lubricant may mix with the refrigerant to form a diluted lubricant mixture (e.g., lubricant diluted with refrigerant). Generally, the amount of refrigerant relative to the amount of lubricant in the diluted lubricant mixture (e.g., a dilution value) increases as the temperature of the diluted lubricant mixture increases (e.g., as the temperature within the sump increases) because more refrigerant may dissolve in the lubricant as temperature increases. The diluted lubricant mixture may reduce an operational efficiency of the vapor compression system as the dilution of refrigerant increases. For example, the mixture may not properly lubricate certain components of the compressor if the dilution value exceeds a threshold value. Additionally, as the lubricant flows from the sump and a cooler to the compressor, the lubricant may include properties that reduce the operational efficiency of the vapor compression system. For example, if the lubricant or the diluted lubricant mixture includes a viscosity that exceeds a threshold range upon entering the compressor, the diluted lubricant mixture may inhibit movement of components of the compressor, may not properly lubricate the components of the compressor, and/or may reduce the efficiency of the compressor. If the viscosity of the mixture is relatively low, lubrication of the compressor may be inadequate. If the viscosity of the mixture is relatively high, frictional losses may increase, thereby reducing an efficiency of the vapor compression system. As should be understood, the viscosity may depend on a temperature of the diluted lubricant mixture.

Some examples of fluids that may be used as refrigerants in embodiments of the vapor compression system of the present disclosure are hydrofluorocarbon (HFC) based refrigerants, such as R-410A, R-<NUM>, or R-134a, hydrofluoroolefin (HFO) based refrigerants, such as R-<NUM> or R-<NUM>, "natural" refrigerants, such as ammonia (NH<NUM>), R-<NUM>, carbon dioxide (COz), R-<NUM>, or hydrocarbon based refrigerants, water vapor, or any other suitable refrigerant. In some embodiments, the vapor compression system may be configured to efficiently utilize refrigerants having a normal boiling point of about <NUM> degrees Celsius (<NUM> degrees Fahrenheit) at one atmosphere of pressure, also referred to as low pressure refrigerants, as compared to 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. Some examples of fluids that may be used as lubricants in embodiments of the vapor compression system of the present disclosure are synthetic oils, mineral oils, or any other suitable lubricant.

The present invention is directed to control of a vapor compression system based on lubricant dilution and lubricant viscosity. The vapor compression system includes sensors that detect operating parameters (e.g., temperature and pressure) of the lubricant or the diluted lubricant mixture (e.g., lubricant having refrigerant dissolved therein) at certain locations within the system. For example, the sensors may be disposed within and/or coupled to the sump and may detect the pressure and the temperature of the diluted lubricant mixture within the sump. Based on the pressure and the temperature of the diluted lubricant mixture within the sump, a controller of the vapor compression system determines or calculates a dilution value of the lubricant in the mixture (e.g., a ratio and/or percentage composition of the refrigerant relative to the lubricant in the mixture). The controller compares the dilution value (e.g., a relative amount of the refrigerant in the mixture) to a threshold value and outputs a control signal to perform a control operation based on the dilution value exceeding the threshold value. The relative amount of the refrigerant in the mixture may be a percentage amount of the refrigerant in the mixture relative to a percentage amount of the lubricant in the mixture. In some embodiments, the control operation may include providing a user-detectable alert and/or shutting down the compressor.

In other embodiments, the control operation may include adjusting operation of, or shutting down, other components of the vapor compression system to adjust an operating condition of the vapor compression system (e.g., adjusting a temperature of the diluted lubricant mixture within the sump, adjusting a flow rate of the lubricant or of the diluted lubricant mixture from the sump, and/or adjusting a temperature of the lubricant or of the diluted lubricant mixture within the cooler).

During operation of the vapor compression system, the mixture (e.g., diluted lubricant mixture) may exit the sump, flow through a cooler (e.g., a heat exchanger), and into the compressor. The cooler may condition the lubricant to improve an efficiency of the compressor. In certain embodiments, the vapor compression system may include a sensor that detects a temperature of the diluted lubricant mixture at an outlet of the cooler. Based on the temperature at the cooler outlet, the controller may determine a viscosity value of the mixture. The controller may compare the viscosity value to a threshold range and output a control signal to perform a control operation based on the viscosity value exceeding the threshold range. In some embodiments, the control operation may include providing a user-detectable alert and/or shutting down the compressor.

In other embodiments, the control operation may include adjusting operation of, or shutting down, other components of the vapor compression system to adjust an operating condition of the vapor compression system (e.g., adjusting a temperature of the diluted lubricant mixture within the sump, adjusting a flow rate of the lubricant or of the diluted lubricant mixture from the sump, and/or adjusting a temperature of the lubricant or of the diluted lubricant mixture within the cooler). As such, based on the dilution value of the diluted lubricant mixture and/or based on the viscosity value of the diluted lubricant mixture, the controller may alert an operator that the dilution value and/or the viscosity value have exceeded the threshold level/range and/or may shutdown the compressor to prevent inefficient operation of the compressor and/or the vapor compression system.

The control techniques of the present disclosure may be used in a variety of systems. However, to facilitate discussion, examples of systems that may incorporate the control techniques of the present disclosure are depicted in <FIG>, which are described herein below.

Turning now to the drawings, <FIG> is a perspective view of an embodiment of an environment for a heating, ventilation, and air conditioning (HVAC) system <NUM> in a building <NUM> for a typical commercial setting. The HVAC system <NUM> may include a vapor compression system <NUM> that supplies a chilled liquid, which may be used to cool the building <NUM>. The HVAC system <NUM> may also include a boiler <NUM> to supply warm liquid to heat the building <NUM> and an air distribution system which circulates air through the building <NUM>. The air distribution system can also include an air return duct <NUM>, an air supply duct <NUM>, and/or an air handler <NUM>. In some embodiments, the air handler <NUM> may include a heat exchanger that is connected to the boiler <NUM> and the vapor compression system <NUM> by conduits <NUM>. The heat exchanger in the air handler <NUM> may receive either heated liquid from the boiler <NUM> or chilled liquid from the vapor compression system <NUM>, depending on the mode of operation of the HVAC system <NUM>. The HVAC system <NUM> is shown with a separate air handler on each floor of building <NUM>, but in other embodiments, the HVAC system <NUM> may include air handlers <NUM> and/or other components that may be shared between or among floors.

<FIG> and <FIG> illustrate embodiments of the vapor compression system <NUM> that can be used in the HVAC system <NUM>. The vapor compression system <NUM> circulates a refrigerant through a circuit starting with a compressor <NUM>. The circuit may also include a condenser <NUM>, an expansion valve(s) or device(s) <NUM>, and a liquid chiller or an evaporator <NUM>. The vapor compression system <NUM> further includes a control panel <NUM> (e.g., controller) that has an analog to digital (A/D) converter <NUM>, a microprocessor <NUM>, a non-volatile memory <NUM>, and/or an interface board <NUM>.

In some embodiments, the vapor compression system <NUM> may use one or more of a variable speed drive (VSDs) <NUM>, a motor <NUM>, the compressor <NUM>, the condenser <NUM>, the expansion valve or device <NUM>, and/or the evaporator <NUM>. The motor <NUM> may drive the compressor <NUM> and may be powered by a variable speed drive (VSD) <NUM>. The VSD <NUM> 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 <NUM>.

In other embodiments, the motor <NUM> may be powered directly from an AC or direct current (DC) power source. The motor <NUM> 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 <NUM> compresses a refrigerant vapor and delivers the vapor to the condenser <NUM> through a discharge passage. In some embodiments, the compressor <NUM> may be a centrifugal compressor. The compressor <NUM> includes a lubricant (e.g., oil) that lubricates components of the compressor. As described in greater detail below, a portion of the refrigerant within the compressor <NUM> may mix with the lubricant. The refrigerant vapor delivered by the compressor <NUM> to the condenser <NUM> may transfer heat to a cooling fluid (e.g., water or air) in the condenser <NUM>. The refrigerant vapor may condense to a refrigerant liquid in the condenser <NUM> as a result of thermal heat transfer with the cooling fluid. The refrigerant liquid from the condenser <NUM> may flow through the expansion device <NUM> to the evaporator <NUM>. In the illustrated embodiment of <FIG>, the condenser <NUM> is water cooled and includes a tube bundle <NUM> connected to a cooling tower <NUM>, which supplies the cooling fluid to the condenser.

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

<FIG> is a schematic diagram of the vapor compression system <NUM> with an intermediate circuit <NUM> incorporated between condenser <NUM> and the expansion device <NUM>. The intermediate circuit <NUM> may have an inlet line <NUM> that is directly fluidly connected to the condenser <NUM>. In other embodiments, the inlet line <NUM> may be indirectly fluidly coupled to the condenser <NUM>. As shown in the illustrated embodiment of <FIG>, the inlet line <NUM> includes a first expansion device <NUM> positioned upstream of an intermediate vessel <NUM>. In some embodiments, the intermediate vessel <NUM> may be a flash tank (e.g., a flash intercooler). In other embodiments, the intermediate vessel <NUM> may be configured as a heat exchanger or a "surface economizer. " In the illustrated embodiment of <FIG>, the intermediate vessel <NUM> is used as a flash tank, and the first expansion device <NUM> is configured to lower the pressure of (e.g., expand) the refrigerant liquid received from the condenser <NUM>.

During the expansion process, a portion of the liquid may vaporize, and thus, the intermediate vessel <NUM> may be used to separate the vapor from the liquid received from the first expansion device <NUM>. Additionally, the intermediate vessel <NUM> may provide for further expansion of the refrigerant liquid because of a pressure drop experienced by the refrigerant liquid when entering the intermediate vessel <NUM> (e.g., due to a rapid increase in volume experienced when entering the intermediate vessel <NUM>).

The vapor in the intermediate vessel <NUM> may be drawn by the compressor <NUM> through a suction line <NUM> of the compressor <NUM>. In other embodiments, the vapor in the intermediate vessel may be drawn to an intermediate stage of the compressor <NUM> (e.g., not the suction stage). The liquid that collects in the intermediate vessel <NUM> may be at a lower enthalpy than the refrigerant liquid exiting the condenser <NUM> because of the expansion in the expansion device <NUM> and/or the intermediate vessel <NUM>. The liquid from intermediate vessel <NUM> may then flow in line <NUM> through a second expansion device <NUM> to the evaporator <NUM>.

<FIG> is a schematic diagram illustrating an embodiment of a lubrication circuit <NUM> (e.g., a portion of the vapor compression system <NUM>) that may include one or more components controlled by the microprocessor <NUM> of the control panel <NUM> to enhance an efficiency of the vapor compression system <NUM>. As described above, the vapor compression system <NUM> includes a lubricant (e.g., oil) that circulates through the compressor <NUM> to lubricate components (e.g., bearings) of the compressor <NUM>. During operation, refrigerant may dissolve or otherwise mix with the lubricant within the compressor <NUM> to form a mixture of lubricant and refrigerant. For example, the refrigerant and the lubricant may mix with one another as the compressor <NUM> receives the refrigerant from the evaporator <NUM>, as the refrigerant circulates within the compressor <NUM>, and/or as the refrigerant flows out of the compressor <NUM> and to the condenser <NUM>.

The lubrication circuit <NUM> includes a sump <NUM> fluidly coupled to the compressor <NUM>. After lubricating components of the compressor <NUM>, the mixture of lubricant and refrigerant flows toward and may accumulate within the sump <NUM>. In some embodiments, the composition of the mixture received by the sump <NUM> may be between approximately (e.g., within <NUM>% of, within <NUM>% of, or within <NUM>% of) <NUM>% and <NUM>% refrigerant by mass and between approximately (e.g., within <NUM>% of, within <NUM>% of, or within <NUM>% of) <NUM>% and <NUM>% lubricant by mass.

In other embodiments, the composition of the mixture may be between approximately <NUM>% and <NUM>% refrigerant by mass and between approximately <NUM>% and <NUM>% lubricant by mass, between approximately <NUM>% and <NUM>% refrigerant by mass and between approximately <NUM>% and <NUM>% lubricant by mass, between approximately <NUM>% and <NUM>% refrigerant by mass and between approximately <NUM>% and <NUM>% lubricant by mass, and/or other suitable compositions.

As shown in the illustrated embodiment of <FIG>, the sump <NUM> is positioned generally below the compressor <NUM> so that lubricant may flow from the compressor <NUM> toward the sump <NUM> via gravity. In certain embodiments, the sump <NUM> may be positioned at other locations relative to the compressor <NUM> to receive the lubricant or the mixture of lubricant and refrigerant from the compressor <NUM>.

Within the sump <NUM>, a portion of the refrigerant in the mixture of lubricant and refrigerant may separate from the mixture (e.g., as a refrigerant gas) as the mixture expands upon entering the sump <NUM>. As such, the mixture exiting the sump <NUM> and returning to the compressor <NUM> generally contains less refrigerant when compared to the mixture entering the sump <NUM> and exiting the compressor <NUM>. The refrigerant gas may flow from the sump <NUM> to an auxiliary condenser <NUM>, which may include a cooling fluid in a heat exchange relationship with the refrigerant gas. The cooling fluid may absorb thermal energy from the refrigerant gas and condense the refrigerant gas to refrigerant liquid. The auxiliary condenser <NUM> is coupled to a pump <NUM> that is configured to direct the refrigerant from the auxiliary condenser <NUM> to the compressor <NUM> or otherwise back to the vapor compression system <NUM>.

Additionally or alternatively, the pump <NUM> may facilitate the flow of the refrigerant gas from the sump <NUM> to the auxiliary condenser <NUM>. In certain embodiments, the vapor compression system <NUM> may include a valve <NUM> that controls a flow of the refrigerant gas to and from the auxiliary condenser <NUM>. As illustrated, the valve <NUM> is disposed adjacent to an outlet of the sump <NUM> and adjacent to an inlet of the auxiliary condenser <NUM> and, thus, may control the flow of the refrigerant gas to the auxiliary condenser <NUM>. In certain embodiments, the auxiliary condenser <NUM> may be omitted from the vapor compression system <NUM> and the lubrication circuit <NUM> such that the refrigerant gas may be vented to the compressor <NUM>.

After a portion of the refrigerant gas is removed from the mixture, a pump <NUM> within the sump <NUM> (e.g., a submersible pump) directs the lubricant or the mixture to a cooler <NUM>. In some embodiments, the pump <NUM> may be disposed outside the sump <NUM> and/or may be positioned between the cooler <NUM> and the compressor <NUM>. The cooler <NUM> is fluidly coupled to the sump <NUM> at a cooler inlet <NUM> and is fluidly coupled to the compressor <NUM> at a cooler outlet <NUM>. The cooler <NUM> may be a shell-and-tube heat exchanger or another suitable heat exchanger configured to absorb thermal energy from the mixture flowing from the sump <NUM> to the compressor <NUM>. For example, the cooler <NUM> may remove heat from the mixture that is absorbed by the mixture via mechanical friction within the compressor <NUM>. In other words, the cooler <NUM> may remove heat that is absorbed by the mixture when lubricating the compressor <NUM>. After passing through the cooler <NUM>, the mixture flows to the compressor <NUM> for lubrication of the components of the compressor <NUM>.

In some embodiments, the sump <NUM> includes a heating element <NUM> that provides heat to the mixture within the sump <NUM> in order to vaporize refrigerant within the mixture and remove the refrigerant from the lubricant. As described in greater detail below, the temperature and the pressure of the mixture within the sump <NUM> affects the dilution of the mixture. As such, the heating element <NUM> may be controlled to remove the refrigerant from the mixture, and thus, adjust the dilution of the lubricant that is ultimately directed toward the compressor <NUM>.

Portions of the lubrication circuit <NUM>, and the vapor compression system <NUM> generally, are controlled based on feedback indicative of operating parameters of the vapor compression system <NUM>. For example, the vapor compression system <NUM> is controlled based on feedback indicative of a temperature and a pressure of the mixture within the sump <NUM>, and may be controlled based on feedback indicative of a temperature of the mixture at the cooler outlet <NUM>, and/or based on other feedback. As shown in the illustrated embodiment of <FIG>, the sump <NUM> includes a temperature sensor <NUM> and a pressure sensor <NUM> configured to provide feedback indicative of the temperature and/or the pressure of the mixture within the sump <NUM>, respectively. The temperature sensor <NUM> and the pressure sensor <NUM> are communicatively coupled to the control panel <NUM> and are configured to output signals to the control panel <NUM> indicative of the temperature and the pressure of the mixture within the sump <NUM>. Additionally, the vapor compression system <NUM> may include a temperature sensor <NUM> at the cooler outlet <NUM> that is configured to provide feedback indicative of a temperature of the lubricant and/or the mixture at the cooler outlet <NUM>. The temperature sensor <NUM> is communicatively coupled to the control panel <NUM> and is configured to output a signal to the control panel <NUM> indicative of the temperature at the cooler outlet <NUM>.

Based on the feedback indicative of the temperature and/or the pressure within the sump <NUM>, the microprocessor <NUM> (e.g., using instructions stored in the memory <NUM>) determines a dilution (e.g., a dilution value) of the mixture (e.g., a relative amount or percentage composition of the refrigerant relative to the lubricant in the mixture). Additionally or alternatively, the microprocessor <NUM> may determine a viscosity (e.g., a viscosity value) of the mixture based on the temperature at the outlet of the cooler <NUM>. In other embodiments, the microprocessor <NUM> may determine the dilution and/or the viscosity of the mixture based on other operating parameters (e.g., a pressure of the mixture in the cooler <NUM>, properties of the refrigerant, and/or properties of the lubricant).

The microprocessor <NUM> compares the dilution and/or the viscosity of the mixture to threshold values and/or threshold ranges (e.g., dilution threshold values and viscosity threshold ranges stored in the memory <NUM>). The threshold values and/or the threshold ranges may be determined by the microprocessor <NUM> based on inputs <NUM> to the interface board <NUM> (e.g., inputs indicative of properties of the lubricant and/or the refrigerant). For example, the control panel <NUM> is configured to receive the inputs <NUM> at the control panel <NUM> indicative of properties of the lubricant, the refrigerant, and/or the mixture. Such properties may include a type of lubricant, a type of refrigerant, and/or other properties of the lubricant and/or of the refrigerant. In some embodiments, the inputs <NUM> may include an operating mode of the vapor compressor compression <NUM>. Alternatively, the inputs <NUM> may include threshold values and/or the threshold ranges.

The dilution and the viscosity may each be compared to one or multiple threshold values and/or threshold ranges. Based on the comparison, the microprocessor <NUM> outputs control signals to perform control operations on various components of the vapor compression system <NUM>. For example, the microprocessor <NUM> may compare the dilution to a first threshold value and a second threshold value and output a control signal to perform first and/or second control operations based on the dilution exceeding the first or second threshold value, respectively. The first threshold value may be based on a target percentage or a relative amount of refrigerant in the mixture and/or a target percentage or a relative amount of lubricant in the mixture. Additionally, the second threshold value may include an additional target percentage or a relative amount of refrigerant in the mixture that is greater than the first threshold value. In some embodiments, when the dilution exceeds the second threshold value, the compressor <NUM> may be shut down. The first threshold value of the dilution may be <NUM>% refrigerant by mass (e.g., a maximum of <NUM>% refrigerant in the mixture), and the second threshold value may be <NUM>% refrigerant by mass. In other embodiments, the first threshold value may be any value between <NUM>% and <NUM>% refrigerant by mass, and the second threshold value may be any value between <NUM>% and <NUM>% refrigerant by mass, with the second threshold value being greater than the first threshold value.

Further, the microprocessor <NUM> may compare the viscosity to a first threshold range and a second threshold range and output a control signal to perform third and/or fourth control operations based on the viscosity exceeding the first or second threshold ranges, respectively. For example, each of the first threshold range and the second threshold range may include an upper limit and a lower limit. The viscosity may exceed the first threshold range and/or the second threshold range if the viscosity is greater than the upper limit or less than the lower limit. The viscosity may be within the threshold range (e.g., not exceed the threshold range) if the viscosity is less than or equal to the upper limit and greater than or equal to the lower limit. The threshold ranges of the viscosity may be based on target viscosities of the mixture. In certain embodiments, the first threshold range may be generally within the second threshold range such that the second threshold range is larger than the first threshold range. For example, the first threshold range may be between about <NUM><NUM>/s (<NUM> centistokes ("cSt")) and about <NUM><NUM>/s (<NUM> cSt), between about <NUM><NUM>/s (<NUM> cSt) and about <NUM><NUM>/s (<NUM> cSt), between about <NUM><NUM>/s (<NUM> cSt) and about <NUM><NUM>/s (<NUM> cSt), or between about <NUM><NUM>/s (<NUM> cSt) and about <NUM><NUM>/s (<NUM> cSt). The second threshold range may be between about <NUM><NUM>/s (<NUM> cSt) and about <NUM><NUM>/s (<NUM> cSt), between about <NUM><NUM>/s (<NUM> cSt) and about <NUM><NUM>/s (<NUM> cSt), between about <NUM><NUM>/s (<NUM> cSt) and about <NUM><NUM>/s (<NUM> cSt), or between about <NUM><NUM>/s (<NUM> cSt) and about <NUM><NUM>/s (<NUM> cSt). In some embodiments, the first threshold range may be between about <NUM><NUM>/s (<NUM> cSt) to about <NUM><NUM>/s (<NUM> cSt), and the second threshold range may be between about <NUM><NUM>/s (<NUM> cSt) and about <NUM><NUM>/s (<NUM> cSt).

The microprocessor <NUM> may output control signals based on the dilution exceeding the first and/or second threshold values, the viscosity exceeding the first and/or second threshold ranges, or both. Such control operations may include providing a user-detectable warning or alert via an indicator <NUM> of the interface board <NUM>, adjusting a speed or other operational parameter of the compressor <NUM>, shutting down operation of the compressor <NUM>, shutting down operation of other components of the vapor compression system <NUM> (e.g., the sump <NUM>, the auxiliary condenser <NUM>, or the cooler <NUM>), adjusting the heating element <NUM> to control the temperature and/or pressure within the sump <NUM>, adjusting a speed of the pump <NUM>, adjusting a speed of the pump <NUM>, adjusting a position of the valve <NUM> positioned adjacent to the auxiliary condenser <NUM> to control the flow of the refrigerant gas through the auxiliary condenser <NUM>, other suitable operating parameters, or any combination thereof. The indicator <NUM> may be any user-detectable notification, such as a light emitting diode (LED), an audible alert, a display, text, and/or another suitable notification. The microprocessor <NUM> of the control panel <NUM> may be communicatively coupled to the compressor <NUM>, the sump <NUM>, the auxiliary condenser <NUM>, the pump <NUM>, pump <NUM>, the cooler <NUM>, and/or other components of the vapor compression system <NUM> to provide such control signals.

By way of a non-limiting example, the microprocessor <NUM> may output a first control signal to provide a user-detectable notification via the indicator <NUM> in response to the dilution exceeding the first threshold value. Further, the microprocessor <NUM> may output a second control signal to shutdown operation of the compressor <NUM> in response to the dilution exceeding the second threshold value. Additionally or alternatively, the microprocessor <NUM> may output a third control signal to provide the user-detectable notification via the indicator <NUM> in response to the viscosity exceeding the first threshold range. Further still, the microprocessor <NUM> may output a fourth control signal to shutdown operation of the compressor <NUM> in response to the viscosity exceeding the second threshold range.

<FIG> is a flow chart illustrating an embodiment of a process <NUM> for operating the vapor compression system <NUM> and/or the lubrication circuit <NUM>. It is to be understood that the steps discussed herein are merely exemplary, and certain steps may be omitted or performed in a different order than the order described below. In some embodiments, the process <NUM> may be stored in the memory <NUM> and executed by the microprocessor <NUM> of the control panel <NUM> or stored in other suitable memory and executed by other suitable processing circuitry.

As shown in the illustrated embodiment of <FIG>, at block <NUM>, the microprocessor <NUM> receives an input indicative of properties of the lubricant and/or the refrigerant (e.g., operating properties of the lubricant, operating properties of the refrigerant, a type of lubricant, a type of refrigerant, and operating properties of other fluids within the vapor compression system <NUM>). For example, the input may include the inputs <NUM> provided to the interface board <NUM>. In some embodiments, the input may include the first threshold value and the second threshold value. Alternatively, the microprocessor <NUM> may determine the first threshold value and the second threshold value based on the input and/or based on information stored in the memory <NUM>.

At block <NUM>, the microprocessor <NUM> receives feedback indicative of the temperature and/or the pressure of the mixture within the sump <NUM>. According to the invention, the microprocessor <NUM> receives a first signal indicative of the temperature from the temperature sensor <NUM> and a second signal indicative of the pressure from the pressure sensor <NUM>. In some not-claimed examples, the microprocessor <NUM> may receive feedback indicative of only the temperature or only the pressure of the mixture.

At block <NUM>, the microprocessor <NUM> determines the dilution of the lubricant based on the input, the feedback indicative of the temperature in the sump <NUM>, and/or the feedback indicative of the pressure in the sump <NUM>. Additionally or alternatively, the microprocessor <NUM> may reference data (e.g., temperature and pressure tables, fluid property charts, fluid density tables, and/or other suitable data) stored in the memory <NUM> to determine the dilution of the lubricant. As described above, the dilution is a relative amount of refrigerant within the mixture of refrigerant and lubricant. The relative amount of the refrigerant in the mixture may be a percentage amount of the refrigerant in the mixture relative to a percentage amount of the lubricant in the mixture.

At block <NUM>, the microprocessor <NUM> determines whether the dilution exceeds a first threshold value. The first threshold value may be received via a user input to the interface board <NUM> and/or may be determined based on various properties of the refrigerant and lubricant received at block <NUM>. In some embodiments, the first threshold value may be a percentage composition of the lubricant by mass and/or a percentage composition of the refrigerant by mass. The microprocessor <NUM> compares the dilution determined at block <NUM> to the first threshold value to determine whether the dilution exceeds the first threshold value. When the dilution exceeds the first threshold value, the process <NUM> proceeds to block <NUM>. When the dilution does not exceed the first threshold value (e.g., the dilution is less than or equal to the first threshold value), the process <NUM> returns to block <NUM>. As such, if the dilution does not exceed the first threshold value, the microprocessor <NUM> may continue to receive feedback indicative of the temperature and/or pressure in the sump <NUM> (e.g., block <NUM>) to determine the dilution of the mixture (e.g., block <NUM>).

At block <NUM>, the microprocessor <NUM> performs a first control operation in response to the dilution exceeding the first threshold value. For example, the microprocessor <NUM> may output a first control signal to adjust an operating condition of a component of the vapor compression system <NUM> (e.g., adjusting a speed of the pump <NUM> and/or the pump <NUM>, adjusting an amount of heat supplied by the heating element <NUM>, adjusting a speed of the compressor <NUM>, adjusting a flow of cooling fluid to the cooler <NUM>, and/or adjusting another suitable operating condition). Additionally or alternatively, the first control operation may include providing the user-detectable notification via the indicator <NUM>.

At block <NUM>, the microprocessor <NUM> determines whether the dilution exceeds a second threshold value, greater than the first threshold value. The second threshold value may be received via a user input to the interface board <NUM> and/or may be determined based on various properties of the lubricant and/or the refrigerant. In some embodiments, the second threshold value may be a percentage composition of the refrigerant by mass and/or a percentage composition of the lubricant by mass. The microprocessor <NUM> compares the dilution to the second threshold value to determine whether the dilution exceeds the second threshold value. When the dilution exceeds the second threshold value, the process <NUM> proceeds to block <NUM>. When the dilution does not exceed the second threshold value (e.g., the dilution is less than or equal to the second threshold value), the process <NUM> returns to block <NUM>. As such, if the dilution does not exceed the second threshold value, the microprocessor <NUM> may continue to receive feedback indicative of temperature and/or the pressure in the sump <NUM> (e.g., block <NUM>) and to determine the dilution of the mixture (e.g., block <NUM>).

At block <NUM>, the microprocessor <NUM> may perform a second control operation in response to the dilution exceeding the second threshold value. For example, the microprocessor <NUM> may output a second control signal indicative of instructions to perform a second control operation to a component of the vapor compression system <NUM> (e.g., shutting down and/or adjusting the operation of the compressor <NUM>, adjusting a speed the pump <NUM> and/or the pump <NUM>, adjusting an amount of heat supplied by the heating element <NUM>, a flow rate of the cooling fluid through the cooler <NUM>, and/or adjusting another operating parameter).

In some embodiments, the second control operation may include providing a second user-detectable notification via the indicator <NUM> (e.g., a notification different from the notification provided at block <NUM>).

It should be noted that, in some embodiments, blocks <NUM> and <NUM> may be performed substantially simultaneously with one another. As such, when the microprocessor <NUM> determines that the dilution exceeds the second threshold value, the microprocessor <NUM> may skip block <NUM> and proceed directly to block <NUM> to perform the second control operation.

<FIG> is a flow chart illustrating a process <NUM> for operating the vapor compression system <NUM> and/or the lubrication circuit <NUM>. It is to be understood that the steps discussed herein are merely exemplary, and certain steps may be omitted or performed in a different order than the order described below. In some embodiments, the process <NUM> may be stored in the memory <NUM> and executed by the microprocessor <NUM> of the control panel <NUM> or stored in other suitable memory and executed by other suitable processing circuitry.

As shown in the illustrated example of <FIG>, at block <NUM>, the microprocessor <NUM> receives an input indicative of properties of the lubricant and/or of the refrigerant (e.g., operating properties of the lubricant, operating properties of the refrigerant, a type of lubricant, a type of refrigerant, and operating properties of other fluids within the vapor compression system <NUM>). For example, the input may include the inputs <NUM> provided to the interface board <NUM>. The input may include the first threshold range and the second threshold range. Alternatively, the microprocessor <NUM> may determine the first threshold range and the second threshold range based on the input and/or based on information stored in the memory <NUM>.

At block <NUM>, the microprocessor <NUM> receives feedback indicative of the temperature of the mixture at the cooler outlet <NUM>. For example, the microprocessor <NUM> may receive a signal indicative of the temperature from the temperature sensor <NUM> at the cooler outlet <NUM>.

At block <NUM>, the microprocessor <NUM> determines the viscosity of the mixture based on the input and/or the feedback indicative of the temperature at the cooler outlet <NUM> and/or based on the oil dilution determined during the process <NUM>. Additionally or alternatively, the microprocessor <NUM> may reference data (e.g., temperature tables, fluid property charts, fluid density tables, and/or other suitable data) stored in the memory <NUM> to determine the viscosity of the mixture. As described above, the viscosity of the mixture corresponds to a thickness of the mixture and the ability of the mixture to flow through the vapor compression system <NUM> (e.g., through the sump <NUM> and the compressor <NUM>).

At block <NUM>, the microprocessor <NUM> determines whether the viscosity exceeds a first threshold range. The first threshold range may be received via a user input to the interface board <NUM> and/or may be determined based on various properties of the refrigerant and lubricant received at block <NUM>. The first threshold range may be a particular range viscosities of the mixture. The microprocessor <NUM> compares the viscosity determined at block <NUM> to the first threshold range to determine whether the viscosity exceeds the first threshold range (e.g., to determine whether the viscosity is greater than an upper limit of the first threshold range or less than a lower limit of the first threshold range). When the viscosity exceeds the first threshold range, the process <NUM> proceeds to block <NUM>. When the viscosity does not exceed the first threshold range (e.g., when the viscosity is less than or equal to the upper limit of the first threshold range or greater than or equal to the lower limit of the first threshold range), the process <NUM> returns to block <NUM>. As such, if the viscosity does not exceed the first threshold range, the microprocessor <NUM> may continue to receive feedback indicative of the temperature measurement at the cooler outlet <NUM> (e.g., block <NUM>) to determine the viscosity of the mixture (e.g., block <NUM>).

At block <NUM>, the microprocessor <NUM> performs a third control operation in response to the viscosity exceeding the first threshold range (e.g., a first control operation relative to the viscosity). For example, the microprocessor <NUM> may output a third control signal to adjust an operating condition of a component of the vapor compression system <NUM> (e.g., adjusting a speed of the pump <NUM> and/or of the pump <NUM>, adjusting an amount of heat supplied by the heat element <NUM>, adjusting a speed of the compressor <NUM>, adjusting a flow of cooling fluid to the cooler <NUM>, and/or adjusting another suitable operating condition). Additionally or alternatively, the third control operation may include providing the user-detectable notification via the indicator <NUM>.

At block <NUM>, the microprocessor <NUM> determines whether the viscosity exceeds a second threshold range, larger than the first threshold range. The second threshold range may be received via a user input to the interface board <NUM> and/or may be determined based on various properties of the lubricant, the refrigerant, and/or the mixture of the lubricant and refrigerant. The second threshold range may be a particular range of viscosities of the mixture different from the first threshold range. The microprocessor <NUM> compares the viscosity to the second threshold range to determine whether the viscosity exceeds the second threshold range (e.g., to determine whether the viscosity is greater than an upper limit of the second threshold range or less than a lower limit of the second threshold range). When the viscosity exceeds the second threshold range, the process <NUM> proceeds to block <NUM>. When the viscosity does not exceed the fourth threshold value (e.g., when the viscosity is less than or equal to the upper limit of the second threshold range or greater than or equal to the lower limit of the second threshold range), the process <NUM> returns to block <NUM>. As such, if the viscosity does not exceed the second threshold range, the microprocessor <NUM> may continue to receive feedback indicative of the temperature at the cooler outlet <NUM> (e.g., block <NUM>) and to determine the viscosity of the mixture (e.g., block <NUM>).

At block <NUM>, the microprocessor <NUM> may perform a fourth control operation in response to the viscosity exceeding the second threshold value. For example, the microprocessor <NUM> may output a fourth control signal indicative of instructions to perform a fourth control operation to a component of the vapor compression system <NUM> (e.g., shutting down and/or adjusting the operation of the compressor <NUM>, adjusting a speed of the pump <NUM> and/or of the pump <NUM>, adjusting an amount of heat supplied by the heat element <NUM>, adjusting a flow rate of the cooling fluid through the cooler <NUM>, or adjusting another operating parameter). The fourth control operation may include providing a second user-detectable notification via the indicator <NUM> (e.g., a notification different from the notification provided at block <NUM>).

It should be noted that blocks <NUM> and <NUM> may be performed substantially simultaneously with one another. As such, when the microprocessor <NUM> determines that the viscosity exceeds the second threshold range, the microprocessor <NUM> may skip block <NUM> and proceed directly to block <NUM> to perform the fourth control operation.

Although the processes <NUM> and <NUM> are described herein as individual processes, the processes <NUM> and <NUM>, or certain steps thereof, may be combined into a single process or method. For example, the vapor compression <NUM> may perform steps of the processes <NUM> and <NUM> simultaneously or independently. By way of non-limiting example, the vapor compression system <NUM>, via the microprocessor <NUM>, may determine both the dilution and the viscosity of the mixture, compare the dilution to the first and second threshold values, compare the viscosity to the first and second threshold ranges, and perform certain control operations (e.g., first, second, third, and/or fourth control operations) based on both comparisons. As such, the vapor compression system <NUM>, via the microprocessor <NUM>, may control certain components and/or provide user-detectable notifications based on the determined dilution and/or the determined viscosity of the mixture.

Accordingly, the present disclosure is directed to control of a vapor compression system based on a dilution (e.g., a dilution value) and a viscosity (e.g., a viscosity value) of a mixture of lubricant and refrigerant of a lubrication circuit. The vapor compression system includes sensors that provide feedback indicative of operating parameters (e.g., temperature and pressure) of the mixture at certain locations within the system. For example, the sensors may be disposed within and/or coupled to a sump of the lubrication circuit and may provide feedback indicative of the pressure and the temperature of the mixture within the sump. Based on the pressure and the temperature of the mixture within the sump, the vapor compression system, via a controller, may determine a dilution of the refrigerant in the mixture (e.g., a ratio and/or percentage composition of the refrigerant in the mixture). The controller may compare the dilution to a threshold value and output a control signal to perform a control operation within the vapor compression system based on the dilution exceeding the threshold value.

The control operation may include providing a user-detectable notification and/or adjusting a component of the vapor compression system (e.g., shutting down the compressor, adjusting an amount of heat supplied to the mixture within the sump via a heating element, adjusting a flow rate of the mixture from the sump via a pump, and/or adjusting a flow rate of cooling fluid supplied to a cooler of the lubrication circuit).

During operation of the vapor compression system, the mixture may exit the sump, flow through the cooler, and into the compressor. The cooler may condition the lubricant or mixture to have a target temperature, which may improve an efficiency of the compressor. In certain embodiments, the vapor compression system may include a sensor that detects a temperature of the lubricant or the mixture at an outlet of the cooler. Based on the temperature at the cooler outlet, the controller may determine a viscosity of the mixture. The controller may compare the viscosity to a threshold range and output a control signal to perform a control operation within the vapor compression system based on the viscosity exceeding the threshold range.

Claim 1:
A vapor compression system (<NUM>), comprising:
- a compressor (<NUM>) configured to circulate a refrigerant through a refrigerant loop;
- a sump (<NUM>) configured to receive a mixture of lubricant and the refrigerant from the compressor (<NUM>); and
- a controller (<NUM>) comprising a memory (<NUM>) and a processor (<NUM>), wherein the processor (<NUM>) is configured to:
- receive a first signal indicative of a temperature of the mixture within the sump (<NUM>);
- receive a second signal indicative of a pressure of the mixture within the sump (<NUM>);
- determine a relative amount of the refrigerant in the mixture based on the first signal and the second signal; and
- output a control signal in response to the relative amount of the refrigerant in the mixture exceeding a threshold value.