WO2024250179A1

WO2024250179A1 - Super-high temperature heat pump

Info

Publication number: WO2024250179A1
Application number: PCT/CN2023/098708
Authority: WO
Inventors: Wuchao WANG; Xiaorui YU; Qingxuan ZHAO
Original assignee: Trane Air Conditioning Systems China Co Ltd; Trane International Inc
Current assignee: Trane Air Conditioning Systems China Co Ltd; Trane International Inc
Priority date: 2023-06-06
Filing date: 2023-06-06
Publication date: 2024-12-12
Anticipated expiration: 2025-12-06

Abstract

A heating, ventilation, air conditioning, and refrigeration (HVACR) system includes a suction adjust valve fluidly connecting an outlet of the evaporator to a suction port of the compressor. The suction adjust valve is to control a refrigerant flow from the outlet of the evaporator to the suction port of the compressor, and control a refrigerant pressure drop based on a result of monitoring at least one of (i) a refrigerant pressure difference at the expansion device and (ii) a refrigerant superheat downstream of the suction adjust valve.

Description

SUPER-HIGH TEMPERATURE HEAT PUMP

FIELD

This disclosure relates generally to a super-high temperature heat pump. More specifically, the disclosure relates to a super-high temperature heat pump to provide hot water with a heat source.

BACKGROUND

A heating, ventilation, air conditioning, and refrigeration (HVACR) system may include a heat pump to provide hot water with a heat source. In a refrigerant circuit of the heat pump, a refrigerant flows through an evaporator and absorbs heat from the heat source to change to a low-pressure refrigerant which can be applied to a compressor. The refrigerant from the compressor flows through a condenser and rejects heat to a process fluid (e.g., water) to provide the hot water.

SUMMARY

This disclosure relates generally to a heating, ventilation, air conditioning, and refrigeration (HVACR) system including a heat pump. More specifically, the disclosure relates to a heat pump to provide, e.g., hot water or steam with a heat source.

Embodiments disclosed herein provide HVACR systems including a super-high temperature heat pump to provide hot water (e.g., at or over 120 ℃) or steam with a heat source (e.g., at or over 40 ℃) . Embodiments described herein can improve the reliability, stability and efficiency of a super-high temperature heat pump, by addressing issues including, for example, wet compression and/or low suction/discharge superheat when the system is in a starting stage, and oil viscosity in a stable running stage.

Briefly, in one embodiment, the present disclosure describes a heating, ventilation, air conditioning and refrigeration (HVACR) system. The HVACR system includes a refrigeration circuit including an evaporator, a compressor, an expansion device, and a condenser to operate a refrigerant therein, and a suction adjust valve fluidly connecting an outlet of the evaporator to a suction port of the compressor. The suction adjust valve is configured to control a refrigerant flow from the outlet of the evaporator to the suction port of the compressor. The system further includes a controller configured to monitor at least one of (i) a pressure difference at the expansion device and (ii) a refrigerant superheat downstream of the suction adjust valve, and adjust the suction adjust valve to control a refrigerant pressure drop from the outlet of the evaporator to the suction port of the compressor based on a result of the monitoring.

In another embodiment, the present disclosure describes a method of controlling a heating, ventilation, air conditioning and refrigeration (HVACR) system including a refrigeration circuit including an evaporator, a compressor, an expansion device, and a condenser to operate a refrigerant therein. The method includes fluidly connecting, via a suction adjust valve, an outlet of the evaporator to a suction port of the compressor. The suction adjust valve is configured to control a refrigerant flow from the evaporator to the suction port of the compressor. The method further includes monitoring at least one of (i) a pressure difference at the expansion device and (ii) a refrigerant superheat downstream of the suction adjust valve, and adjusting the suction adjust valve to control a refrigerant pressure drop from the outlet of the evaporator to the suction portion of the compressor based on a result of the monitoring.

Various aspects and advantages of exemplary embodiments of the disclosure have been summarized. The above Summary is not intended to describe each illustrated embodiment. Other features and aspects will become apparent by consideration of the following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

References are made to the accompanying drawings that form a part of this disclosure and which illustrate the embodiments in which systems and methods described in this specification can be practiced.

FIG. 1 illustrates a schematic diagram of a refrigerant circuit, which may be implemented in an HVACR system, according to an embodiment.

FIG. 2 is a schematic diagram of a control system, according to an embodiment.

FIG. 3 is a schematic diagram of a super-high temperature heat pump, according to an embodiment.

FIG. 4 is a flow diagram of a method for controlling a heat pump, according to an embodiment.

FIG. 5 is a flow diagram of a method for controlling a heat pump in a starting stage or mode change stage, according to an embodiment.

FIG. 6 is a flow diagram of a method for controlling a re-heater of a heat pump, according to an embodiment.

FIG. 7 is a flow diagram of a method for controlling oil cooling and refrigerant superheat in a heat pump, according to an embodiment.

Like reference numbers represent like parts throughout.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to the accompanying drawings, which form a part of the description. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. Furthermore, unless otherwise noted, the description of each successive drawing may reference features from one or more of the previous drawings to provide clearer context and a more substantive explanation of the current example embodiment. Still, the example embodiments described in the detailed description, drawings, and claims are not intended to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings, may be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein.

Particular embodiments of the present disclosure are described herein with reference to the accompanying drawings; however, it is to be understood that the disclosed embodiments are merely examples of the disclosure, which may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure. In this description, as well as in the drawings, like-referenced numbers represent elements that may perform the same, similar, or equivalent functions.

Additionally, the present disclosure may be described herein in terms of functional block components and various processing steps. It should be appreciated that such functional blocks may be realized by any number of hardware and/or software components configured to perform the specified functions.

The scope of the disclosure should be determined by the appended claims and their legal equivalents, rather than by the examples given herein. For example, the steps recited in any method claims may be executed in any order and are not limited to the order presented in the claims. Moreover, no element is essential to the practice of the disclosure unless specifically described herein as “critical” or “essential. ”

As referenced herein, “suction superheat” may refer to a temperature difference between the temperature of refrigerant vapor at a suction line of a compressor and its saturation temperature at the corresponding suction pressure. It can be used as a parameter to evaluate and control the performance of a HVAC system. Suction superheat can be measured using temperature sensors placed at the suction line of the compressor. The measured temperature can be compared to the saturation temperature corresponding to the suction pressure to determine the temperature difference (i.e., superheat) .

As referenced herein, “discharge superheat” may refer to a temperature difference between the temperature of refrigerant vapor at a discharge line of a compressor and its saturation temperature at the corresponding discharge pressure. It can be used as a parameter to evaluate and control the performance of a HVACR system. Discharge superheat can be measured using temperature sensors placed at the discharge line of the compressor. The measured temperature can be compared to the saturation temperature corresponding to the discharge pressure to determine the temperature difference (i.e., superheat) .

As referenced herein, “thermosyphon” or “thermosyphon device” may refer to a passive heat exchange mechanism that is charged by a working fluid (e.g., a refrigerant such as hydrofluorocarbon (HFC) or haloalkane refrigerant, e.g., R-134a) . The working fluid flows (e.g., via its own gravity) into the heat exchange mechanism, receives heat from a process fluid at a relatively higher temperature (e.g., an oil from an oil separator) , evaporates and exits the heat exchange mechanism (e.g., by means of a pressure gradient) . The above process continues while the high-temperature process fluid passes through the heat exchange mechanism to transfer heat to the working fluid and drive the process. In an embodiment, a thermosyphon device may include a brazed plate (BP) heat exchanger.

Embodiments described herein can maintain the suction superheat at a desired level for the efficient and reliable operation of the compressor and the refrigeration system. A correct suction/discharge superheat can prevent refrigerant liquid from entering/leaving the compressor, and the so-called “wet compression, ” which may cause damage to the compressor and/or reduce efficiency or reliability of the system.

Embodiments disclosed herein provide HVACR systems including a super-high temperature heat pump. Embodiments described herein can apply a low pressure refrigerant to a compressor to provide hot water (e.g., at or over 120 ℃) or steam with a heat source (e.g., at or over 40 ℃) . A low pressure refrigerant may have a relative low pressure at a given saturated temperature, such as, for example, R245fa, and R1233zdE (E) . R410A is an exemplary high pressure refrigerant. R134a is an exemplary middle pressure refrigerant. Embodiments described herein can improve the reliability, stability and efficiency of a super-high temperature heat pump, by addressing issues including, for example, wet compression and/or low suction/discharge superheat when the system is in a starting stage or a transition stage, and oil viscosity in a stable running stage.

“Starting stage” may refer to the initial phase of a refrigeration system (e.g., a heat pump) when it is turned on or restarted after a shutdown. During the starting stage, the compressor is started to begin the circulation of working fluid (e.g., refrigerant) in the refrigeration system.

“Stable running stage” may refer to the phase of which the refrigeration system operates at its intended and relatively steady state conditions. After the system goes through the starting stage, the system may enter the stable running stage.

“Transition stage” may refer to the phase of a refrigeration system when there are relatively obvious/dramatic changes in operating conditions/states or system requirements. For example, the system may be in a transition stage when the refrigeration system changes its operation mode (e.g., from a heating mode to a cooling mode) , or when the temperature of a process fluid dramatically changes (e.g., water temperature changes from 70 ℃ to 100 ℃) . It is to be understood that a refrigeration system (e.g., a heat pump) may have multiple running phases including the starting stage, the stable running stage and the transition stage. Running parameters such as, e.g., pressure, temperature, etc., in a stable running stage are relatively stable. That is, while the running parameters in the stable running stage may change or fluctuate, they are not as dramatic as in a starting stage and/or a transition stage.

FIG. 1 is a schematic diagram of a refrigerant circuit 100, according to an embodiment. The refrigerant circuit 100 includes a compressor 120, a condenser 140, an expansion device 160, and an evaporator 180. The refrigerant circuit 100 may also include a controller (e.g., controller 145 of FIG. 2) configured to control the operations of the compressor 120, the condenser 140, the expansion device 160, the evaporator 180, and/or other circuit components of the refrigerant circuit 100.

The refrigerant circuit 100 can generally be applied in a variety of systems used to control an environmental condition (e.g., temperature, humidity, air quality, or the like) in a conditioned space. In an embodiment, the refrigerant circuit 100 can be applied to produce cold/hot fluid (e.g., water) . The conditioned space can be a space within an office building, a commercial building, a factory, a laboratory, a data center, a residential building, or the like. In an embodiment, the refrigerant circuit 100 can be configured to be a cooling system (e.g., an air conditioning system) capable of operating in a heating mode or a cooling mode. In an embodiment, the refrigerant circuit 100 can be configured to be a heat pump that can operate in a heating mode. It is appreciated that the refrigerant circuit 100 can be configured to operate in a heating mode and switch to a cooling mode, or operate in a cooling mode and switch to a heating mode.

The compressor 120, the condenser 140, the expansion device 160, and the evaporator 180 can be fluidly connected. An “expansion device” as described herein may also be referred to as an expander. In an embodiment, the expansion device 160 can be an expansion valve, expansion plate, expansion vessel, orifice, or the like, or other such types of expansion mechanisms. It should be appreciated that the expansion device 160 may be any suitable type of expansion device used in the field for expanding a working fluid to cause the working fluid to decrease in pressure and temperature.

The refrigerant circuit 100 is an example and can be configured to include more or less components. For example, in an embodiment, the refrigerant circuit 100 can include other components such as, but not limited to, an economizer heat exchanger, one or more flow control devices (e.g., a valve, a pump, etc. ) , a receiver tank, a dryer, a suction-liquid heat exchanger (e.g., a reheater) , or the like.

The refrigerant circuit 100 can operate according to generally known principles. The refrigerant circuit 100 can be configured to heat and/or cool a liquid process fluid. The liquid process fluid can be a heat transfer fluid or medium (e.g., a liquid such as, but not limited to, water or the like) . The refrigerant circuit 100 may be generally representative of a liquid chiller system. The refrigerant circuit 100 can alternatively be configured to heat and/or cool a gaseous process fluid (e.g., a heat transfer medium or fluid (e.g., a gas such as, but not limited to, air or the like) , in which case the refrigerant circuit 100 may be generally representative of an air conditioner and/or heat pump.

In some embodiments, the refrigerant circuit 100 can operate as a vapor-compression circuit such that the compressor 120 compresses a working fluid (e.g., a heat transfer fluid such as, but not limited to, refrigerant or the like) from a relatively lower pressure gas to a relatively higher-pressure gas. The relatively higher-pressure gas is at a relatively higher temperature, being discharged from the compressor 120 and flowing through the condenser 140. In accordance with generally known principles, the working fluid flows through the condenser 140 and rejects heat to the process fluid (e.g., water, air, etc. ) , thereby cooling the working fluid. In an embodiment, the process fluid can be water which is heated to provide hot water, for example, over 120 ℃ water (steam) . The cooled working fluid, which is now in a liquid form, flows to the expansion device 160 that can reduce the pressure of the working fluid. As a result, a portion of the working fluid is converted to a gaseous form. The working fluid, which is now in a mixed liquid and gaseous form flows to the evaporator 180. The working fluid flows through the evaporator 180 and absorbs heat from the process fluid (e.g., a heat transfer medium such as, but not limited to, water, a solution, air, etc. ) , heating the working fluid, and converting it to a gaseous form. In an embodiment, the process fluid is water with a temperature, for example, at or over 40 ℃. The process fluid (e.g., water at or over 40 ℃) works as a heat source to evaporate the working fluid. The gaseous working fluid then returns to the compressor 120. The above-described process continues while the heat transfer circuit is operating, for example, in a heating mode to provide hot water or steam (e.g., while the compressor 120 is enabled) .

In some embodiments, the refrigerant circuit 100 can be configured to operate as a free cooling/heating circuit to control one or more environmental conditions of the conditioned space. A free cooling/heating circuit can include a first heat exchanger and a second heat exchanger fluidly connected by a working fluid. The first and second heat exchangers of the free cooling/heating circuit can be dedicated heat exchangers in addition to the refrigeration circuit 100 having the compressor 120, the condenser 140, the expansion device 160, and the evaporator 180. In some embodiments, the first and second heat exchangers can share, for example, the condenser 140 and the evaporator 180 such that the refrigeration circuit 100 can operate as a free cooling/heating circuit or a vapor compression circuit.

In some embodiments, the first heat exchanger can exchange thermal energy between a working fluid and an ambient fluid (e.g., outdoor air) . The first exchanger can be disposed in a location suitable to exchange thermal energy with the ambient fluid. The location can include a rooftop of the conditioned space. The second heat exchanger can be the evaporator 180 to exchange thermal energy between the working fluid and fluid in the conditioned space. Fluid in the conditioned space can, for example, be indoor air. In some embodiments, the first heat exchanger can be the condenser 140.

In a cooling operation, the first heat exchanger can release thermal energy to the ambient fluid and cool the working fluid. A pump can move the cooled working fluid to the second heat exchanger to exchange thermal energy with the fluid in the conditioned space, heating the working fluid to be cooled by the ambient fluid again. In some embodiments, in a cooling operation, the ambient fluid can have a temperature lower than the temperature of the fluid in the conditioned space. In a heating operating, the pump can circulate the working fluid between the first and the second heat exchangers to move thermal energy from the ambient fluid to the fluid in the conditioned space. In some embodiments, in a heating operation, the ambient fluid can have a temperature higher than the temperature of the fluid in the conditioned space. The working fluid can be any heat transfer fluid such as a refrigerant, water, a water solution, glycol fluid, or the like.

FIG. 2 illustrates a schematic diagram of a control system 130, according to an embodiment. The control system 130 includes a controller 145 configured to control a suction adjust valve 190 such as, for example, a suction adjust valve 350 in a refrigerant circuit 300 of FIG. 3. The suction adjust valve 190 is controlled by the controller 145 and configured to control a refrigerant pressure drop from an outlet of an evaporator (e.g., evaporator 350 of FIG. 3) to a suction port of a compressor (e.g., compressor 310 of FIG. 3) to obtain a desired/required pressure difference between a suction port and a discharge port of the compressor. The operation of suction adjust valve in a refrigeration system and the associated control methods are further described in detail in embodiments depicted in FIGS. 3-5.

The controller 145 can receive various sensing data from sensor (s) 182 distributed in a HVACR system and generate control signals based on the received sensing data. The sensor (s) 182 may include, for example, temperature sensor (s) , pressure sensor (s) , etc. The sensors can be located at various locations of a refrigeration system.

The controller 145 is generally representative of hardware aspects of a controller for the refrigerant circuit 100 (FIG. 1) . The controller 145 is an example and is not intended to be limiting. The controller 145 includes a processor 150, a memory 155, input/output 175, and storage 165. It is to be appreciated that the controller 145 can include one or more additional components.

The processor 150 can retrieve and execute programming instructions stored in the memory 155 and/or the storage 165. The processor 150 can also store and retrieve application data residing in the memory 155. The processor 150 can be a single processor, multiple processors, co-processors, or a single processor having multiple processing cores. In some embodiments, the processor 150 can be a single-threaded processor. In some embodiments, the processor 150 can be a multi-threaded processor.

An interconnect 170 is used to transmit programming instructions and/or application data between the processor 150, the memory 155, the storage 165, and the input/output 175. The interconnect 170 can, for example, be one or more buses or the like.

The memory 155 is generally included to be representative of a random access memory such as, but not limited to, Static Random Access Memory (SRAM) , Dynamic Random Access Memory (DRAM) , Flash, suitable combinations thereof, or the like. In some embodiments, the memory 155 can be a volatile memory. In some embodiments, the memory 155 can be a non-volatile memory.

The input/output 175 can include both wired and wireless connections. In an embodiment, the input/output 175 can transmit data and/or control signals via a wire line, an optical fiber cable, or the like.

Aspects described herein can be embodied as a system, method, or computer readable medium. In an embodiment, the aspects described can be implemented in hardware, software (including firmware or the like) , or combinations thereof. Some aspects can be implemented in a computer readable medium, including computer readable instructions for execution by a processor. Any combination of one or more computer readable medium (s) can be used.

The computer readable medium can include a computer readable signal medium and/or a computer readable storage medium. A computer readable storage medium can include any tangible medium capable of storing a computer program for use by a programmable processor to perform functions described herein by operating on input data and generating an output. A computer program is a set of instructions that can be used, directly or indirectly, in a computer system to perform a certain function or determine a certain result.

Examples of computer readable storage media include, but are not limited to, a floppy disk; a hard disk; a random access memory (RAM) ; a read-only memory (ROM) ; a semiconductor memory device such as, but not limited to, an erasable programmable read-only memory (EPROM) , an electrically erasable programmable read-only memory (EEPROM) , Flash memory, or the like; a portable compact disk read-only memory (CD-ROM) ; an optical storage device; a magnetic storage device; other similar device; or suitable combinations of the foregoing.

A computer readable signal medium can include a propagated data signal having computer readable instructions. Examples of propagated signals include, but are not limited to, an optical propagated signal, an electro-magnetic propagated signal, or the like. A computer readable signal medium can include any computer readable medium that is not a computer readable storage medium that can propagate a computer program for use by a programmable processor to perform functions described herein by operating on input data and generating an output.

FIG. 3 is a schematic diagram of a refrigerant circuit 300 which can be a super-high temperature heat pump implemented in an HVACR system, according to an embodiment. The heat pump 300 includes a refrigeration circuit including a compressor 310, an evaporator 320, an expansion device 330, and a condenser 340 to operate a working fluid (e.g., a refrigerant) therein.

The compressor 310 may include a compression mechanism and a motor. The compressor 310 may include a suction adjust valve (e.g., suction adjust valve 350) at an inlet (i.e., suction port 310a) to control the flow of refrigerant vapor into the compressor 310, and a discharge check valve at an outlet (i.e., discharge port 310b) to prevent a backward flow when the refrigerant circuit is shutting down. One or more pressure sensors and temperature sensors can be disposed at or adjacent to the discharge port 310b to measure refrigerant pressures and temperatures. In an embodiment, the compressor 310 is a screw compressor. It is to be understood that the compressor 310 can be any suitable types of compressor other than a screw compressor.

The compressor 310 may also include an oil system to provide lubrication to reduce friction and wear between moving parts. An oil separator 315 is connected, via the discharge line 313, to the compressor 310 to separate oil from the refrigerant vapor. The separated oil is returned to the compressor 310 via a thermosyphon circuit to cool down the oil, which will be described further below. The refrigerant vapor then proceeds to the condenser 340 and rejects heat to the process fluid, thereby cooling the refrigerant. In the embodiment depicted in FIG. 3, the process fluid is water which enters the condenser 340 via an inlet 341, and the heated water exits the condenser 340 via an outlet 343. In an embodiment, the water can be heated to a temperature, for example, at or over 120 ℃. The hot water can be injected to a flash tank (not shown) to generate water steam. The inlet 341 and the outlet 343 may each include a temperature sensor to measure the respective water temperatures. The cooled refrigerant liquid then flows to the expansion device 330 that can reduce the pressure of the refrigerant and may convert the refrigerant liquid into a mixed liquid and gaseous form flowing to the evaporator 320.

The refrigerant flows through the evaporator 320 and absorbs heat from the process fluid, which heats the working fluid, and converts it to a gaseous form. The gaseous refrigerant then exits the evaporator 320 via an outlet 320a. In the embodiment depicted in FIG. 3, the process fluid is water which enters the evaporator 320 via an inlet 321, and acts as a heat source for the refrigerant in the evaporator 320. The cooled water exits the evaporator 320 via an outlet 323. The inlet 321 and the outlet 323 may each include a temperature sensor to measure the respective water temperatures. In an embodiment, the heat source (e.g., water) may have a temperature, for example, at or over 40 ℃, or from about 40 ℃ to about 85 ℃.

It is to be understood that the process fluid for the evaporator 320 may be any suitable process fluid other than water as the heat source. The choice of a process fluid may depend on various factors such as, for example, the load of the system (e.g., the desired amount of hot water or steam provided at the condenser 340) . In an embodiment, water with a temperature at or over 40 ℃ (e.g., from about 40 ℃ to about 85 ℃) may be used as the heat source of any tonnage chiller for providing/generating any desired amount of hot water or steam.

A suction adjust valve 350 fluidly connects the outlet 320a of the evaporator 320 to the suction port 310a of the compressor 310. The suction adjust valve 350 is configured to control a refrigerant flow from the outlet 320a of the evaporator 320 to the suction port 310a of the compressor 310. The suction adjust valve 350 can be any type of valves capable of controlling the refrigerant flow, including, for example, a butterfly valve, a solenoid valve, a ball valve, etc. The suction adjust valve 350 may regulate the refrigerant flow continuously or at discrete level (s) between a fully open state and a fully closed state. For example, a butterfly valve may regulate the flow of fluids by adjusting among multiple states including, for example, a fully opened state to allow the maximum flow, a fully closed state to completely shut off the flow, and one or more partially closed/opened states between the fully opened state and the fully closed state.

In the embodiment depicted in FIG. 3, the suction adjust valve 350 is illustrated as a separate device and located at a suction line 352 fluidly connecting the outlet 320a of the evaporator 320 to the suction port 310a of the compressor 310. It is to be understood that a suitable suction adjust valve described herein may have various configurations and/or locations as long as the suction adjust valve can generate and control a refrigerant pressure drop from an evaporator to a compressor which are fluidly connected by a suction line. In an embodiment, the suction adjust valve 350 can be installed at the suction port 310a of the compressor 310, or at the outlet 320a of the evaporator 320. In an embodiment, the suction adjust valve 350 may be integrated with the compressor 310 or the evaporator 320 as a component thereof instead of as a separate device.

The heat pump 300 further includes a controller system or controller (e.g., the controller 145 of FIG. 2) . The controller can monitor at least one of (i) a refrigerant pressure difference at the expansion device 330 and (ii) a refrigerant superheat (e.g., a refrigerant discharge superheat) downstream of the suction adjust valve 350. The controller can adjust the suction adjust valve 350 to control a refrigerant pressure drop from the outlet 320a of the evaporator 320 to the suction port 310a of the compressor 310 and to obtain a desired/required level of refrigerant pressure difference between the inlet and outlet (i.e., 310a and 310b) of the compressor 310, based on a result of the monitoring, which will be described further below in FIGS. 4 and 5.

The heat pump 300 further includes a re-heater 370 configured to conduct and control a heat exchange between the refrigerant liquid at a relatively higher temperature from the condenser 340 and the refrigerant vapor at a relatively lower temperature from the suction adjust valve 350. The re-heater 370 may include any suitable type of heat exchanger to conduct the heat exchange. The high-temperature refrigerant liquid leaving the condenser 340 is directed to the heat exchanger or re-heater 370. The low-temperature refrigerant vapor from the evaporator 320 is also directed into the heat exchanger or re-heater 370. The heat exchange causes the high-temperature refrigerant liquid to cool down to get more sub-cooling, while the low-temperature refrigerant vapor gains heat and starts to warm up. The heated refrigerant vapor is directed to the suction port 310a of the compressor 310. The cooled refrigerant can be directed to a downstream throttle or pressure drop device such as, for example, the evaporation device 330.

In the embodiment depicted in FIG. 3, the re-heater 370 is illustrated as a separate device fluidly connecting the evaporator 320 and the condenser 340. It is to be understood that a suitable re-heater described herein may have various configurations and/or locations as long as the re-heater can conduct a heat exchange between the high-temperature refrigerant fluid (e.g., liquid) from the condenser 340 and the low-temperature refrigerant fluid (e.g., vapor) from the evaporator 320. In an embodiment, the re-heater 370 may be integrated with the evaporator 320 or the condenser 340 as a component thereof instead of as a separate device.

A refrigerant bypass valve 332 is provided between the condenser 340 and the re-heater 370 to control a flow of the high-temperature refrigerant liquid from the condenser 340 to the re-heater 370. The controller can instruct an operation of the refrigerant bypass valve 332 to control the amount of high-temperature refrigerant liquid from the condenser 340 to pass through the re-heater 370. For example, the controller can instruct an operation of the bypass valve 332 to allow more/less high-temperature refrigerant liquid to pass through the re-heater 370 to heat the low-temperature refrigerant vapor via the re-heater 370. Doing so can increase/decrease the refrigerant suction superheat at the suction port 310a of the compressor 310.

The heat pump 300 further includes a thermosyphon circuit to conduct and control a heat exchange at least between (i) the oil from the oil separator 315 and the refrigerant liquid from the evaporator 320, and (ii) the oil from the oil separator 315 and the refrigerant liquid from the condenser 340. The thermosyphon circuit can provide a staged cooling to the oil from the oil separator 315. In the embodiment depicted in FIG. 3, the thermosyphon circuit includes a condenser thermosyphon 362 as a heat exchanger between the oil from the oil separator 315 and the refrigerant liquid from the condenser 340 to cool down the oil from the separator 315. The evaporated refrigerant returns to the condenser 340.

The thermosyphon circuit further includes an evaporator thermosyphon 364 as a heat exchanger between the oil from the condenser thermosyphon 362 and the refrigerant liquid from the evaporator 320. The refrigerant liquid is directed from the evaporator 320 via a liquid line 356 to flow through the evaporator thermosyphon 364 and absorb heat from the oil from the condenser thermosyphon 362 to further cool down the oil. The evaporated refrigerant is directed from the evaporator thermosyphon 364 to the suction port 310a of the compressor 310 via a vent line 365.

An oil bypass valve 367 is provided between the condenser thermosyphon 362 and the evaporator thermosyphon 364 to control a flow of the oil from the condenser thermosyphon 362 to the evaporator thermosyphon 364. The controller can control the opening level of the oil bypass valve 367 to control the amount of high-temperature oil to conduct a heat exchange with the low-temperature refrigerant liquid through the evaporator thermosyphon 364. For example, the controller can instruct an operation of the bypass valve 367 to allow more/less oil to pass through the evaporator thermosyphon 364 to increase/decrease the corresponding refrigerant superheat at an outlet of the evaporator thermosyphon 364. In an embodiment, the oil bypass valve 367 allows a portion of the oil from the condenser thermosyphon 362 to pass through the evaporator thermosyphon 364 to maintain the corresponding refrigerant superheat in a desired range (e.g., between about 0 °F and about 50 °F) .

A control valve 368 is provided at the vent line 365 to control the refrigerant flow from the evaporator thermosyphon 364 to the suction port 310a of the compressor 310. The controller can monitor the refrigerant pressure difference between the suction port 310a and the evaporator 350, i.e., a refrigerant pressure drop from the outlet 320a of the evaporator 320 to the suction port 310a of the compressor 310, and adjust the control valve based on results of the monitoring. One or more pressure sensors can be provided at the outlet 320a and the suction port 310a to measure refrigerant pressures. In an embodiment, the control valve 368 can be controlled to coordinate with the operation of suction adjust valve 350. For example, when the suction adjust valve 350 partially closes and the refrigerant pressure difference increases, the controller can instruct the control valve 368 to operate to decrease the valve opening to prevent too much liquid refrigerant flow entering into the compressor 310. The level of the valve opening may be determined based on the monitored refrigerant pressure difference.

The heat pump 300 further includes an optional oil cooler 366 downstream of the evaporator thermosyphon 364 and the bypass valve 367 to provide an active cooling to the oil passing through the oil cooler 366. The cooling refrigerant liquid may be directed, via a pressure, from an oil cooler expansion device 366a which receives the refrigerant liquid from the condenser 340. The cooled oil returns to the compressor 310 via an oil return line 369, where a temperature sensor can be provided to measure the oil temperature. The evaporated refrigerant is directed to the suction port 310a of the compressor 310, where a temperature sensor can be provided to measure the refrigerant temperature. It is to be understood that the operation of oil cooler 366 and/or oil cooler expansion device 366a is optional, and it can be activated to further cool down the oil if it is desired to do so.

In an embodiment, the heat pump 300 may include one or more heaters installed at one or more of components of the heat pump 300 including, for example, the oil separator 315, a discharge cavity of the compressor 310, a motor cavity of the compressor 310, a suction line or port 310a of the compressor 310, etc. When the heat pump 300 is turned down, the controller can monitor a component temperature of the heat pump 300, for example, a motor temperature of the compressor 310. When the motor temperature is lower than a predetermined threshold (e.g., 60 ℃ to 80 ℃) , the controller can instruct one or more of the heaters to heat the relevant components to prevent refrigerant migration and condensing in the compressor 310 and the oil separator 315. The heater (s) can also heat suction line (s) (e.g., the suction line 352) and/or other refrigerant circuit components (e.g., the re-heater 370) when the heat pump 300 is turned off. The heated suction line (s) and/or other refrigerant circuit components can heat refrigerant fluid (e.g., vapor) in the starting stage to increase the suction/discharge superheat to a desired range within a shortened period of time, and to prevent refrigerant flooding of the compressor 310 and the oil separator 315.

FIG. 4 is a flowchart 400 of a method for controlling a heat pump such as, e.g., the heat pump 300 of FIG. 3, according to an embodiment.

The flowchart 400 may include one or more operations, actions, or functions depicted by one or more blocks 410, 415, 420, 430, 435, and 440. Although illustrated as discrete blocks, various blocks may be divided into additional blocks, combined into fewer blocks, or eliminated, depending on the desired implementation. In an embodiment, the method 400 can be performed by the control system 130 of FIG. 2, or any other suitable control systems or controllers.

The flowchart 400 may begin at block 410. At block 410 (Detect a starting or transition stage) , the control system or controller detects whether a heating, ventilation, air conditioning and refrigeration (HVACR) system starts to work or is in a transition stage (e.g., changing from a first mode to a second mode) . For example, the control system or controller detects whether the heat pump 300 of FIG. 3 is in a starting stage, in a normal operation stage, or during a change from a first operation mode to a second operation mode. The method 400 may proceed to block 415.

At block 415 (Activate suction adjust valve) , the control system or controller sends an instruction to activate the suction adjust valve when the system starts to work or is in a transition stage (e.g., changing operation modes) . For example, the suction adjust valve 350 may be activated to change from a fully open state to a partially closed state when the starts to work. The method 400 may proceed to block 420.

At block 420 (Monitor at least one of (i) pressure difference and (ii) superheat) , the control system or controller receives sensing data from various sensor (s) 182 in the HVACR system to monitor at least one of (i) a refrigerant pressure difference at the expansion device 330 and (ii) a refrigerant superheat downstream of the suction adjust valve 350. For example, the control system or controller can receive the pressure data from pressure sensors at the monitoring point (s) to monitor the refrigerant pressures at the condenser 340 and the evaporator 320 to determine the pressure difference at downstream/upstream sides of the expansion device 330, temperature data from temperature sensors at the suction port 310a of the compressor 310 to monitor the temperature of refrigerant to determine the suction superheat, and/or temperature data from temperature sensors at the discharge line 313 of the compressor 310 to monitor the temperature of refrigerant to determine the discharge superheat. It is to be understood that in an embodiment, an ultimate goal of the suction adjust valve 350 is to control the refrigerant pressure difference at an expansion device and the discharge superheat at an outlet of a compressor to be within their respective desired ranges. Maintaining the discharge superheat within the desired range can improve the reliability of the compressor. The method 400 may proceed to block 430.

In an embodiment, the refrigerant pressure difference at the downstream/upstream sides of the expansion device 330 can be determined by measuring the refrigerant pressure at the condenser 340 and the refrigerant pressure at the evaporator 320, and the expansion device pressure difference is the refrigerant pressure difference between the condenser 340 and the evaporator 320. The condenser 340 and the evaporator 320 each may include a pressure sensor to measure the respective refrigerant pressures. In an embodiment, the refrigerant pressure difference at the downstream/upstream sides of the expansion device 330 can be determined by measuring a first refrigerant pressure at a first point downstream of the expansion device 330, and a second refrigerant pressure at a second point upstream of the expansion device 330. The first point can be, for example, at an outlet of the expansion device 330. The second point can be, for example, at an inlet of the expansion device 330. It is to be understood that the first and second measuring points can be any locations in the refrigeration system except for the portion of between the suction adjust valve 350 and the compressor 310.

In an embodiment, the refrigerant superheat downstream of the suction adjust valve 350 can be determined based on a measured temperature of refrigerant vapor at the discharge line 313 of the compressor 310. The difference between the measured temperature and the refrigerant saturation temperature at the corresponding discharge pressure can be determined as the measured discharge superheat. In an embodiment, the refrigerant superheat downstream of the suction adjust valve 350 can be determined based on a measured temperature of refrigerant vapor at the suction line 352 of the compressor 310. The difference between the measured temperature and the refrigerant saturation temperature at the corresponding suction pressure can be determined as the measured suction superheat. The suction pressure can be measured by a pressure sensor located at or adjacent to the suction port 310a of the compressor 310.

At block 430 (Pressure/Superheat) , the control system or controller determines (i) whether the refrigerant pressure difference at the downstream/upstream sides of the expansion device 330 is at a level at or lower than a predetermined pressure level, and/or (ii) whether the refrigerant discharge superheat is at or lower than a predicted refrigerant superheat level. When the control system or controller determines that (i) the refrigerant pressure difference at the downstream/upstream sides of the expansion device 330 (e.g., between the condenser 340 and the evaporator 320) is at a level at or lower a predetermined pressure level, or (ii) the refrigerant discharge superheat is at or lower than a predicted refrigerant superheat level, the method 400 proceeds to 435. When the control system or controller determines that (i) the pressure difference at the downstream/upstream sides of the expansion device 330 is at a level greater than the predetermined pressure level, and (ii) the refrigerant discharge superheat is greater than the predicted refrigerant superheat level, the method 400 may proceed to block 440.

It is to be understood that a refrigerant discharge superheat and a refrigerant suction superheat may be correlated with each other. In an embodiment, the suction adjust valve 320 can be controlled to change the suction superheat, and the discharge superheat can be changed accordingly. In an embodiment, the control system or controller can monitor the discharge superheat directly, instead of monitoring the suction superheat.

At block 435 (Maintain valve state) , the control system or controller sends an instruction to the suction adjust valve 350 to maintain its partially closed state. In an embodiment, the partially closed state can be maintained when at least one of the pressure difference and the refrigerant discharge superheat does not increase to the corresponding threshold levels (e.g., the predetermined pressure level, and the predicted refrigerant superheat level) . The method 400 may proceed to block 420.

At block 440 (Adjust valve state) , the control system or controller sends instructions to the suction adjust valve 320 to open the suction adjust valve 320 from its partially closed state to increase a refrigerant flow from the outlet 320a of the evaporator 320 to the suction port 310a of the compressor 310. In an embodiment, the suction adjust valve 320 can be opened from its partially closed state when the pressure difference and the refrigerant discharge superheat each increase to reach the corresponding threshold levels or above (e.g., about 5 psi above the predetermined pressure level, about 3 °F above the predicted refrigerant superheat level) . The method 400 may proceed to block 420.

In an embodiment, the control system or controller may instruct the suction adjust valve 320 to wait for a period of time before opening from its partially closed state until the pressure difference and the refrigerant discharge superheat each increase to a range above the corresponding threshold levels. This is the so-called “deadband, ” which refers to a range or band of values within which no adjustment is made. For example, the control system or controller may instruct the suction adjust valve 320 to wait and maintain the partially closed state until the monitored pressure difference is above a range, for example, 5 psi above the predetermined pressure level. It is to be understood that a range for the deadband may be dynamically determined. For example, the control system or controller may compare the refrigerant discharge superheat measured in real time to a predefined/preset refrigerant superheat level and calculate an integration of the difference between the measured value and the predefined/preset level based on time. The control system or controller can instruct the suction adjust valve 320 to wait and maintain the partially closed state until the integration result is greater than a preset level. The deadband or threshold level of refrigerant superheat can be predicted or simulated by any suitable mathematic equations or methods.

It is to be understood that the opening level of the suction adjust valve 320 can be continuously adjusted according to the monitored the pressure difference at the downstream/upstream sides of the expansion device 330, and/or the refrigerant superheat downstream of the suction adjust valve 350 (e.g., the refrigerant discharge superheat) .

In an embodiment, the control system or controller may determine a first opening level of the suction adjust valve 320 according to the monitored pressure difference at the downstream/upstream sides of the expansion device 330 (e.g., the refrigerant pressure difference between the condenser 340 and the evaporator 320) , and determine a second opening level of the suction adjust valve 320 according to the monitored refrigerant superheat downstream of the suction adjust valve 350 (e.g., the refrigerant discharge superheat) . The control system or controller may instruct the suction adjust valve 320 to open with a smaller one of the first and second opening levels to ensure the operating stability and reliability of the system. For example, when the control system or controller determines to fully open the suction adjust valve 320 based on the monitored the pressure difference, and determines to partially close the suction adjust valve 320 based on the monitored refrigerant superheat, the final decision made by the control system or controller may be to partially close the suction adjust valve 320.

FIG. 5 is a flowchart 500 of a method for controlling a heat pump in a starting stage or mode change stage, according to an embodiment.

The flowchart 500 may include one or more operations, actions, or functions depicted by one or more blocks 510, 520, 530, 535, 540 and 550. Although illustrated as discrete blocks, various blocks may be divided into additional blocks, combined into fewer blocks, or eliminated, depending on the desired implementation. In an embodiment, the method 500 can be performed by the control system 130 of FIG. 2, or any other suitable control systems or controllers.

The flowchart 500 may begin at block 510. At block 510 (Detect a standby state) , the control system or controller detects whether a heating, ventilation, air conditioning and refrigeration (HVACR) system is at a standby state, waiting for an instruction to start or change from a first mode to a second mode. For example, the control system or controller detects whether the heat pump 300 of FIG. 3 is at a standby state, where the system is operational, not actively engaged in its primary function, and is available to be put into service when needed. The method 500 may proceed to block 520.

At block 520 (Determine refrigerant saturation pressure difference) , the control system or controller determines a refrigerant saturation pressure difference at the respective temperatures of the condenser 340 and the evaporator 320. In an embodiment, the control system or controller detect can monitor a first temperature of the process fluid (e.g., water) at the condenser 340, and a second temperature of the process fluid (e.g., water) at the evaporator 320, respectively. The respective saturation pressures of the refrigerant at the first and second temperatures of the respective process fluids at the condenser 340 and the evaporator 320, and the associated refrigerant saturation pressure difference can be determined. The method 500 may proceed to block 530.

At block 530 (Lower? ) , the control system or controller compares the refrigerant saturation pressure difference to a predetermined pressure level, which may be the same as or different from the predetermined pressure level at block 430 in FIG. 400. When the refrigerant saturation pressure difference is at or lower than the predetermined pressure level, the method 500 may proceed to block 540. When the refrigerant saturation pressure difference is greater than the predetermined level, the method 500 may proceed to block 535.

At block 535 (Fully open suction adjust valve) , the control system or controller sends an instruction to activate the suction adjust valve 350 to a fully open state, when the refrigerant saturation pressure difference is greater than the predetermined level.

At block 540 (Detect a starting stage or transition stage) , the control system or controller detects whether the system starts to work or is in a transition stage (e.g., changing from a first mode to a second mode) . For example, the control system or controller detects whether the heat pump 300 of FIG. 3 is in a starting stage, in a normal operation stage, or during a change from a first operation mode to a second operation mode. The method 500 may proceed to block 550.

At block 550 (Partially close suction adjust valve) , the control system or controller sends an instruction to activate the suction adjust valve 350 when the system starts to work or is in a transition stage (e.g., changing operation modes) . For example, the suction adjust valve 350 may be activated to change from a fully open state to a partially closed state when the system starts to work.

FIG. 6 is a flowchart 600 of a method for controlling a re-heater of a heat pump, according to an embodiment.

The flowchart 600 may include one or more operations, actions, or functions depicted by one or more blocks 605, 610, 620, 630, 635, and 640. Although illustrated as discrete blocks, various blocks may be divided into additional blocks, combined into fewer blocks, or eliminated, depending on the desired implementation. In an embodiment, the method 600 can be performed by the control system 130 of FIG. 2, or any other suitable control systems or controllers.

The flowchart 600 may begin at block 605. At block 605 (Determine system working status) , the control system or controller detects what working status a heating, ventilation, air conditioning and refrigeration (HVACR) system is at. For example, the control system or controller detects that the heat pump 300 of FIG. 3 is at a stable running stage by receiving an indication that the suction adjust valve is at a fully open state. It is to be understood that the system may be detected at any running phase/stage including, e.g., a starting stage, a stable running stage, or a transition stage. It might be relatively easier for a re-heater to control the refrigerant suction superheat in a stable running stage. The method 600 may proceed to block 610.

At block 610 (Reheat refrigerant vapor) , the control system or controller instructs the system to direct the refrigerant liquid at a relatively high temperature from the condenser 340 and the refrigerant vapor at a relatively low temperature from the evaporator 350 to conduct a heat exchange at the re-heater 370. The re-heated refrigerant vapor is directed to the suction port 310a of the compressor 310. The method 600 may proceed to block 615.

At block 620 (Measure suction superheat) , the control system or controller receives sensor data to measure refrigerant superheat. In an embodiment, the refrigerant superheat downstream of the suction adjust valve 350 (e.g., the refrigerant suction superheat) can be determined based on a measured temperature of refrigerant vapor at the suction line 352 of the compressor 310. The difference between the measured temperature and the refrigerant saturation temperature at the corresponding suction pressure can be determined as the measured suction superheat. The method 600 may proceed to block 620.

At block 630 (Lower than goal? ) , the control system or controller determines whether the measured refrigerant suction superheat is lower than a predetermined/predefined/preset/target refrigerant suction superheat level (i.e., a suction superheat goal) . In an embodiment, the superheat goal can be determined based on operation parameters of the system at the stable running state. When the measured refrigerant suction superheat is greater than the superheat goal, the method 600 may proceed to block 635. When the measured refrigerant suction superheat is at or lower than the superheat goal, the method 600 may proceed to block 640.

At block 635 (Open refrigerant bypass valve) , the control system or controller sends an instruction to open the refrigerant bypass valve to decrease the amount of the refrigerant from the condenser to pass through the re-heater 370, when the measured refrigerant suction superheat is greater than the superheat goal. The method 600 may proceed to block 620.

At block 640 (Close refrigerant bypass valve) , the control system or controller sends an instruction to open the refrigerant bypass valve to increase the amount of the refrigerant from the condenser to pass through the re-heater 370, when the measured refrigerant suction superheat is at or lower than the superheat goal. The method 600 may proceed to block 620.

FIG. 7 is a flowchart 700 of a method for controlling oil cooling and refrigerant superheat in a heat pump, according to an embodiment.

The flowchart 700 may include one or more operations, actions, or functions depicted by one or more blocks 705, 710, 720, 730, 740, 745, and 750. Although illustrated as discrete blocks, various blocks may be divided into additional blocks, combined into fewer blocks, or eliminated, depending on the desired implementation. In an embodiment, the method 700 can be performed by the control system 130 of FIG. 2, or any other suitable control systems or controllers.

The flowchart 700 may begin at block 705. At block 705 (Cool down oil from oil separator via first thermosyphon) , the control system or controller instructs the system to direct hot oil from the oil separator and the refrigerant liquid from the condenser 340 to the condenser thermosyphon 362 to conduct a heat exchange to cool down the oil. The method 700 may proceed to block 710.

At block 710 (Cool down oil from first thermosyphon via second thermosyphon) , the control system or controller instructs the system to direct the oil from the condenser thermosyphon 362 and the refrigerant liquid from the evaporator 320 to the evaporator thermosyphon 364 to conduct a heat exchange to further cool down the oil. The method 700 may proceed to block 720.

At block 720 (Adjust oil bypass valve) , the control system or controller sends an instruction to activate the oil bypass valve 367 to control the amount of oil from the condenser thermosyphon 362 to pass through the evaporator thermosyphon 364. The controller can instruct an operation of the bypass valve 367 to allow more/less oil to pass through the evaporator thermosyphon 364 to heat the refrigerant liquid from the liquid line 356, and to increase/decrease the corresponding refrigerant superheat at an outlet of the evaporator thermosyphon 364. In an embodiment, the bypass valve 367 can control the amount of oil at a level to have the corresponding refrigerant superheat within a desired range for a stable operation of the system. In an embodiment, the optional oil cooler 366 of FIG. 3 can be provided downstream of the evaporator thermosyphon 364 and the bypass valve 367 to provide an active cooling to the oil passing through the oil cooler 366. The method 700 may proceed to block 730.

At block 730 (Monitor status of suction adjust valve) , the control system or controller monitors the status of the suction adjust valve 350. For example, the control system or controller can receive sensing data or signal (s) from the suction adjust valve 350 to determine whether the suction adjust valve 350 is at a fully open state or a partially closed state. The method 700 may proceed to block 740.

At block 740 (Partially closed? ) , the control system or controller determines whether the suction adjust valve 350 is partially closed or fully open. When the control system or controller determines that the suction adjust valve 350 is fully open, the method 700 may proceed to block 745. When the control system or controller determines that the suction adjust valve 350 is partially closed, the method 700 may proceed to block 750.

At block 745 (Open control valve) , the control system or controller sends an instruction to the control valve 368 to fully open the control valve 368, when the control system or controller determines that the suction adjust valve 350 is fully open.

At block 750 (Close control valve) , the control system or controller sends an instruction to at least partially close the control valve 368 to decrease the refrigerant flow and to prevent too much refrigerant liquid flow from the evaporator thermosyphon 364 to the suction port 310a of the compressor 310, when the control system or controller determines that the suction adjust valve 350 is partially closed. In an embodiment, the controller can monitor the refrigerant pressure drop induced by the suction adjust valve 350, and adjust the control valve 368 with an amount based on the monitored refrigerant pressure drop. While not wanting to be bound by theory, it is believed that partially closing the suction adjust valve may introduce a pressure drop which may induce an undesired, large amount of refrigerant liquid from the liquid line 356 to flow into the evaporator thermosyphon 364, which may introduce undesired effects on the compressor 310. The control system or controller can coordinate the operation of the suction adjust valve 350 and the control valve 368 to prevent such an issue.

Aspects:

It is appreciated that any one of aspects 1-10 and any one of aspects 11-20 can be combined with each other.

Aspect 1. A heating, ventilation, air conditioning and refrigeration (HVACR) system comprising:

a refrigeration circuit including an evaporator, a compressor, an expansion device, and a condenser to operate a refrigerant therein;

a suction adjust valve fluidly connecting an outlet of the evaporator to a suction port of the compressor, the suction adjust valve being configured to control a refrigerant flow from the outlet of the evaporator to the suction port of the compressor; and

a controller configured to:

monitor at least one of (i) a refrigerant pressure difference at the expansion device and (ii) a refrigerant superheat downstream of the suction adjust valve; and adjust the suction adjust valve to control a refrigerant pressure drop from the

outlet of the evaporator to the suction port of the compressor based on a result of the monitoring.

Aspect 2. The system of Aspect 1, wherein the controller is further configured to:

determine a refrigerant saturation pressure difference at respective temperatures of the condenser and the evaporator before the compressor starts to work; and

adjust the suction adjust valve according to the refrigerant saturation pressure difference when the compressor starts to work.

Aspect 3. The system of Aspect 1 or 2, wherein the controller is further configured to:

monitor the refrigerant pressure difference upstream and downstream of the expansion device; and

activate the suction adjust valve to a partially closed state with an opening level according to the refrigerant pressure difference, when the compressor starts to work.

Aspect 4. The system of any one of Aspects 1-3, wherein the controller is further configured to:

monitor a change of the refrigerant pressure difference at the expansion device; and

activate the suction adjust valve to open with an opening level according to the change of the refrigerant pressure difference.

Aspect 5. The system of any one of Aspects 1-4, wherein the controller is further configured to:

compare the refrigerant superheat downstream of the suction adjust valve to a predetermined refrigerant superheat level; and

activate the suction adjust valve to open with an opening level according to a result of the comparing.

Aspect 6. The system of any one of Aspects 1-5, further comprising a re-heater configured to conduct a heat exchange between a refrigerant liquid from the condenser and a refrigerant vapor from the evaporator to heat the refrigerant vapor.

Aspect 7. The system of Aspect 6, further comprising a refrigerant bypass valve to control a flow of the refrigerant liquid from the condenser to the re-heater.

Aspect 8. The system of any one of Aspects 1-7, further comprising a thermosyphon circuit to conduct a heat exchange between a refrigerant liquid from the evaporator and an oil from the compressor to vaporize the refrigerant liquid to a refrigerant vapor.

Aspect 9. The system of Aspect 8, wherein the thermosyphon circuit comprises a control valve to control a flow of the refrigerant vapor to the suction port of the compressor.

Aspect 10. The system of Aspect 8 or 9, wherein the thermosyphon circuit further comprises an oil bypass valve to control a flow of the oil to the thermosyphon circuit.

Aspect 11. A method of controlling a heating, ventilation, air conditioning and refrigeration (HVACR) system comprising a refrigeration circuit including an evaporator, a compressor, an expansion device, and a condenser to operate a refrigerant therein, the method comprising:

fluidly connecting, via a suction adjust valve, an outlet of the evaporator to a suction port of the compressor, the suction adjust valve being configured to control a refrigerant flow from the evaporator to the suction port of the compressor;

monitoring at least one of (i) a refrigerant pressure difference at the expansion device and

(ii) a refrigerant superheat downstream of the suction adjust valve; and

adjusting the suction adjust valve to control a refrigerant pressure drop from the outlet of the evaporator to the suction portion of the compressor based on a result of the monitoring.

Aspect 12. The method of Aspect 11, further comprising:

monitoring temperatures of the condenser and the evaporator;

determining a refrigerant saturation pressure difference at the temperatures of the condenser and the evaporator before the compressor starts to work; and

adjusting the suction adjust valve with an opening level according to the refrigerant saturation pressure difference when the compressor starts to work.

Aspect 13. The method of Aspect 12, further comprising:

activating the suction adjust valve to a partially closed state when the refrigerant saturation pressure difference is lower than a predetermined value; and

activating the suction adjust valve to a fully open state when the refrigerant saturation pressure difference is greater than the predetermined value.

Aspect 14. The method of any one of Aspects 11-13, further comprising:

monitoring the refrigerant pressure difference at the expansion device when the compressor starts to work; and

activating the suction adjust valve to open with an opening level according to the pressure difference.

Aspect 15. The method of any one of Aspects 11-14, further comprising:

monitoring a change of the pressure difference the expansion device; and

activate the suction adjust valve to open with an opening level according to the change of the pressure difference.

Aspect 16. The method of any one of Aspects 11-15, further comprising:

comparing the refrigerant superheat downstream of the suction adjust valve to a predetermined refrigerant superheat level; and

activating the suction adjust valve to open with an opening level according to a result of the comparing.

Aspect 17. The method of any one of Aspects 11-16, further comprising conducting, via a re-heater, a heat exchange between a controlled amount of refrigerant from the condenser and the refrigerant from the evaporator.

Aspect 18. The method of any one of Aspects 11-17, further comprising conducting, via a thermosyphon circuit, a heat exchange between a controlled amount of oil from the compressor and a refrigerant liquid from the evaporator to vaporize the liquid refrigerant to a refrigerant vapor.

Aspect 19. The method of Aspect 18, further comprising controlling, via a control valve, a flow of the refrigerant vapor to the suction port of the compressor.

Aspect 20. The method of Aspect 19, further comprising at least partially closing the control valve upon a detection of the suction adjust valve being at a partially closed state.

The terminology used in this specification is intended to describe particular embodiments and is not intended to be limiting. The terms “a, ” “an, ” and “the” include the plural forms as well, unless clearly indicated otherwise. The terms “comprises” and/or “comprising, ” when used in this specification, specify the presence of the stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, and/or components.

With regard to the preceding description, it is to be understood that changes may be made in detail, especially in matters of the construction materials employed and the shape, size, and arrangement of parts without departing from the scope of the present disclosure. This specification and the embodiments described are exemplary only, with the true scope and spirit of the disclosure being indicated by the claims that follow.

Claims

A heating, ventilation, air conditioning and refrigeration (HVACR) system comprising:

a refrigeration circuit including an evaporator, a compressor, an expansion device, and a condenser to operate a refrigerant therein;

a suction adjust valve fluidly connecting an outlet of the evaporator to a suction port of the compressor, the suction adjust valve being configured to control a refrigerant flow from the outlet of the evaporator to the suction port of the compressor; and

a controller configured to:

monitor at least one of (i) a refrigerant pressure difference at the expansion device and (ii) a refrigerant superheat downstream of the suction adjust valve; and

adjust the suction adjust valve to control a refrigerant pressure drop from the outlet of the evaporator to the suction port of the compressor based on a result of the monitoring.
The system of claim 1, wherein the controller is further configured to:

determine a refrigerant saturation pressure difference at respective temperatures of the condenser and the evaporator before the compressor starts to work; and

adjust the suction adjust valve according to the refrigerant saturation pressure difference when the compressor starts to work.
The system of claim 1, wherein the controller is further configured to:

monitor the refrigerant pressure difference upstream and downstream of the expansion device; and

activate the suction adjust valve to a partially closed state with an opening level according to the refrigerant pressure difference, when the compressor starts to work.
The system of claim 1, wherein the controller is further configured to:

monitor a change of the refrigerant pressure difference at the expansion device; and

activate the suction adjust valve to open with an opening level according to the change of the refrigerant pressure difference.
The system of claim 1, wherein the controller is further configured to:

compare the refrigerant superheat downstream of the suction adjust valve to a predetermined refrigerant superheat level; and

activate the suction adjust valve to open with an opening level according to a result of the comparing.
The system of claim 1, further comprising a re-heater configured to conduct a heat exchange between a refrigerant liquid from the condenser and a refrigerant vapor from the evaporator to heat the refrigerant vapor.
The system of claim 6, further comprising a refrigerant bypass valve to control a flow of the refrigerant liquid from the condenser to the re-heater.
The system of claim 1, further comprising a thermosyphon circuit to conduct a heat exchange between a refrigerant liquid from the evaporator and an oil from the compressor to vaporize the refrigerant liquid to a refrigerant vapor.
The system of claim 8, wherein the thermosyphon circuit comprises a control valve to control a flow of the refrigerant vapor to the suction port of the compressor.
The system of claim 8, wherein the thermosyphon circuit further comprises an oil bypass valve to control a flow of the oil to the thermosyphon circuit.
A method of controlling a heating, ventilation, air conditioning and refrigeration (HVACR) system comprising a refrigeration circuit including an evaporator, a compressor, an expansion device, and a condenser to operate a refrigerant therein, the method comprising:

fluidly connecting, via a suction adjust valve, an outlet of the evaporator to a suction port of the compressor, the suction adjust valve being configured to control a refrigerant flow from the evaporator to the suction port of the compressor;

monitoring at least one of (i) a refrigerant pressure difference at the expansion device and

(ii) a refrigerant superheat downstream of the suction adjust valve; and

adjusting the suction adjust valve to control a refrigerant pressure drop from the outlet of the evaporator to the suction portion of the compressor based on a result of the monitoring.
The method of claim 11, further comprising:

monitoring temperatures of the condenser and the evaporator;

determining a refrigerant saturation pressure difference at the temperatures of the condenser and the evaporator before the compressor starts to work; and

adjusting the suction adjust valve with an opening level according to the refrigerant saturation pressure difference when the compressor starts to work.
The method of claim 12, further comprising:

activating the suction adjust valve to a partially closed state when the refrigerant saturation pressure difference is lower than a predetermined value; and

activating the suction adjust valve to a fully open state when the refrigerant saturation pressure difference is greater than the predetermined value.
The method of claim 11, further comprising:

monitoring the refrigerant pressure difference at the expansion device when the compressor starts to work; and

activating the suction adjust valve to open with an opening level according to the pressure difference.
The method of claim 11, further comprising:

monitoring a change of the pressure difference the expansion device; and

activate the suction adjust valve to open with an opening level according to the change of the pressure difference.
The method of claim 11, further comprising:

comparing the refrigerant superheat downstream of the suction adjust valve to a predetermined refrigerant superheat level; and

activating the suction adjust valve to open with an opening level according to a result of the comparing.
The method of claim 11, further comprising conducting, via a re-heater, a heat exchange between a controlled amount of refrigerant from the condenser and the refrigerant from the evaporator.
The method of claim 11, further comprising conducting, via a thermosyphon circuit, a heat exchange between a controlled amount of oil from the compressor and a refrigerant liquid from the evaporator to vaporize the liquid refrigerant to a refrigerant vapor.
The method of claim 18, further comprising controlling, via a control valve, a flow of the refrigerant vapor to the suction port of the compressor.
The method of claim 19, further comprising at least partially closing the control valve upon a detection of the suction adjust valve being at a partially closed state.