EP4382827A1 - Kältekreislaufvorrichtung und kältekreislaufsteuerungsverfahren - Google Patents

Kältekreislaufvorrichtung und kältekreislaufsteuerungsverfahren Download PDF

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Publication number
EP4382827A1
EP4382827A1 EP21952785.0A EP21952785A EP4382827A1 EP 4382827 A1 EP4382827 A1 EP 4382827A1 EP 21952785 A EP21952785 A EP 21952785A EP 4382827 A1 EP4382827 A1 EP 4382827A1
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EP
European Patent Office
Prior art keywords
low
stage
refrigerant
stage circuit
refrigeration cycle
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP21952785.0A
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English (en)
French (fr)
Inventor
Tomotaka Ishikawa
Takumi NISHIYAMA
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Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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Publication date
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Publication of EP4382827A1 publication Critical patent/EP4382827A1/de
Pending legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B7/00—Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide

Definitions

  • the present disclosure relates to a refrigeration cycle apparatus provided with a two-stage refrigeration cycle, and also relates to a method for controlling the refrigeration cycle apparatus.
  • a refrigeration apparatus including a low-stage circuit through which a low-stage refrigerant circulates, a high-stage circuit through which a high-stage refrigerant circulates, and a cascade condenser configured to exchange heat between the low-stage refrigerant and the high-stage refrigerant has been known (for example, Patent Literature 1).
  • Patent Literature 1 International Publication No. WO 2014/030236
  • the low-stage circuit is provided with a receiver configured to accumulate surplus refrigerant therein, and a zeotropic refrigerant mixture is used as refrigerant for the low-stage circuit.
  • refrigerant having a low-boiling-point contained in the zeotropic refrigerant mixture accumulates as gas in the receiver, which may vary the composition of refrigerant circulating in the low-stage circuit.
  • the present disclosure has been made to solve the above problems, and it is an object of the present disclosure to provide a refrigeration cycle apparatus and a method for controlling the refrigeration cycle apparatus that can reduce variations in composition of refrigerant.
  • a refrigeration cycle apparatus includes: a high-stage circuit through which a high-stage refrigerant circulates, the high-stage circuit including a first compressor, a condenser, a first expansion device, and a cascade heat exchanger; and a low-stage circuit through which a low-stage refrigerant circulates, the low-stage circuit including a second compressor, the cascade heat exchanger, a receiver, a second expansion device, and an evaporator, wherein the cascade heat exchanger is configured to exchange heat between the high-stage refrigerant and the low-stage refrigerant, the low-stage refrigerant is a zeotropic refrigerant mixture, and high pressure of the low-stage refrigerant circulating in the low-stage circuit is maintained to be equal to or lower than a pressure at or below which the low-stage refrigerant is non-flammable.
  • a method for controlling a refrigeration cycle apparatus is a method for controlling a refrigeration cycle apparatus, the refrigeration cycle apparatus including a high-stage circuit through which a high-stage refrigerant circulates and a low-stage circuit through which a low-stage refrigerant circulates, the high-stage circuit including a first compressor, a condenser, a first expansion device, and a cascade heat exchanger, the low-stage circuit including a second compressor, the cascade heat exchanger, a receiver, a second expansion device, and an evaporator, the cascade heat exchanger being configured to exchange heat between the high-stage refrigerant and the low-stage refrigerant, the low-stage refrigerant being a zeotropic refrigerant mixture, the method including maintaining a high pressure of the low-stage refrigerant circulating in the low-stage circuit to be equal to or lower than a pressure at or below which the low-stage refrigerant is non-flammable.
  • the high pressure of the low-stage refrigerant circulating in the low-stage circuit is maintained to be equal to or lower than the pressure at or below which the low-stage refrigerant is non-flammable, so that it is possible to reduce variations in composition of the refrigerant.
  • a refrigeration cycle apparatus 100 according to Embodiment 1 is described below.
  • the refrigeration cycle apparatus 100 is provided with a two-stage refrigeration cycle in which refrigerant circulates independently in each refrigeration cycle.
  • the refrigeration cycle apparatus 100 is used for various purposes such as freezing, refrigeration, hot-water supply, or air-conditioning.
  • an example is described in which the refrigeration cycle apparatus 100 is used as a refrigeration apparatus configured to cool a freezer compartment or the like.
  • Fig. 1 is a schematic configuration diagram of the refrigeration cycle apparatus 100 according to Embodiment 1.
  • the refrigeration cycle apparatus 100 in the present embodiment includes a high-stage circuit 1, a low-stage circuit 2, and a controller 3.
  • the high-stage circuit 1 is a high-temperature circuit through which a high-stage refrigerant circulates.
  • the low-stage circuit 2 is a low-temperature circuit through which a low-stage refrigerant circulates.
  • the low-stage refrigerant has a boiling point lower than that of the high-stage refrigerant.
  • the high-stage circuit 1 and the low-stage circuit 2 include a cascade heat exchanger 14 that is shared between them. Through the cascade heat exchanger 14, the high-stage refrigerant circulating in the high-stage circuit 1 exchanges heat with the low-stage refrigerant circulating in the low-stage circuit 2.
  • the high-stage circuit 1 includes a first compressor 11, a condenser 12, a first expansion device 13, and the cascade heat exchanger 14.
  • the first compressor 11, the condenser 12, the first expansion device 13, and the cascade heat exchanger 14 are connected in this order by pipes.
  • Examples of the high-stage refrigerant circulating in the high-stage circuit 1 include an HFC-based single refrigerant such as R134a, R32, or R410A, a refrigerant mixture thereof, an HFO-based single refrigerant such as HFO-1234yf, and a refrigerant mixture thereof.
  • the first compressor 11 is, for example, an inverter-type compressor whose capacity is controllable.
  • the first compressor 11 suctions a high-stage refrigerant, compresses the suctioned high-stage refrigerant into a high-temperature high-pressure state, and discharges the compressed high-stage refrigerant to be circulated in the high-stage circuit 1.
  • the condenser 12 is, for example, a fin-and-tube heat exchanger.
  • the condenser 12 is configured to exchange heat between air and the high-stage refrigerant, and condense and liquefy the high-stage refrigerant.
  • the refrigeration cycle apparatus 100 includes a first fan 15 configured to supply air to the condenser 12. Examples of the first fan 15 include a propeller fan and a cross flow fan whose airflow volume is controllable.
  • the condenser 12 may be, for example, a plate heat exchanger configured to exchange heat between water or brine and the high-stage refrigerant. In this case, the first fan 15 may be omitted.
  • the first expansion device 13 is, for example, an electronic expansion valve whose opening degree is controllable.
  • the first expansion device 13 is connected to the condenser 12 to reduce a pressure of the high-stage refrigerant flowing out from the condenser 12 and expand the high-stage refrigerant.
  • the first expansion device 13 may be a capillary tube or a thermostatic expansion valve.
  • the cascade heat exchanger 14 is, for example, a plate heat exchanger.
  • the cascade heat exchanger 14 includes a high-stage flow passage 141 connected to the high-stage circuit 1, and a low-stage flow passage 142 connected to the low-stage circuit 2.
  • the cascade heat exchanger 14 is configured to exchange heat between the high-stage refrigerant flowing through the high-stage flow passage 141 and the low-stage refrigerant flowing through the low-stage flow passage 142.
  • the high-stage flow passage 141 in the cascade heat exchanger 14 serves as an evaporator to evaporate and gasify the high-stage refrigerant.
  • the low-stage flow passage 142 in the cascade heat exchanger 14 serves as a condenser to condense and liquefy the low-stage refrigerant.
  • the low-stage circuit 2 includes a second compressor 21, the cascade heat exchanger 14, a receiver 22, a second expansion device 23, and an evaporator 24.
  • the second compressor 21, the cascade heat exchanger 14, the receiver 22, the second expansion device 23, and the evaporator 24 are connected in this order by pipes.
  • the low-stage refrigerant circulating in the low-stage circuit 2 is a zeotropic refrigerant mixture having a boiling point lower than that of the high-stage refrigerant. A lower evaporating temperature can be obtained by using the zeotropic refrigerant mixture, compared to the evaporating temperature obtained by using a single refrigerant.
  • a zeotropic refrigerant mixture containing CO 2 and R290 (propane) is used as the low-stage refrigerant.
  • CO 2 is refrigerant having a low-boiling-point
  • R290 is refrigerant having a high-boiling-point whose boiling point is higher than that of CO 2 . It is possible to decrease an environmental load by using natural refrigerants such as CO 2 and R290. Mixing CO 2 into the low-stage refrigerant leads to an improvement in the cooling capacity, while mixing R290 into the low-stage refrigerant leads to an improvement in COP and a decrease in triple point of CO 2 , which allows applications in low temperature.
  • the second compressor 21 is, for example, an inverter-type compressor whose capacity is controllable.
  • the second compressor 21 suctions the low-stage refrigerant, compresses the suctioned low-stage refrigerant into a high-temperature high-pressure state, and discharges the compressed low-stage refrigerant to be circulated in the low-stage circuit 2.
  • the receiver 22 is located between the cascade heat exchanger 14 and the second expansion device 23 to temporarily accumulate therein the low-stage refrigerant flowing out from the low-stage flow passage 142 in the cascade heat exchanger 14. Surplus refrigerant generated due to variations in cooling load is accumulated in the receiver 22.
  • the second expansion device 23 is, for example, an electronic expansion valve whose opening degree is controllable.
  • the second expansion device 23 is connected to the refrigerant outlet of the receiver 22 to reduce the pressure of the low-stage refrigerant flowing out from the receiver 22 and expand the low-stage refrigerant.
  • the second expansion device 23 may be a capillary tube or a thermostatic expansion valve.
  • the evaporator 24 is, for example, a fin-and-tube heat exchanger.
  • the evaporator 24 is configured to exchange heat between air and the low-stage refrigerant, and evaporate and gasify the low-stage refrigerant.
  • the refrigeration cycle apparatus 100 includes a second fan 25 configured to supply air to the evaporator 24.
  • the second fan 25 include a propeller fan and a cross flow fan whose airflow volume is controllable.
  • the evaporator 24 may be, for example, a plate heat exchanger configured to exchange heat between water or brine and the low-stage refrigerant. In this case, the second fan 25 may be omitted.
  • the refrigeration cycle apparatus 100 includes a pressure sensor 26 configured to detect a high pressure P H of the low-stage refrigerant circulating in the low-stage circuit 2.
  • the pressure sensor 26 is provided on a pipe connecting the receiver 22 and the low-stage flow passage 142 in the cascade heat exchanger 14. Note that the pressure sensor 26 can be provided at any location in a high-pressure side of the low-stage circuit 2.
  • the high-pressure side of the low-stage circuit 2 is between a discharge port of the second compressor 21 and a refrigerant inlet of the second expansion device 23.
  • the high pressure P H of the low-stage refrigerant detected by the pressure sensor 26 is transmitted to the controller 3.
  • the refrigeration cycle apparatus 100 may include a sensor configured to detect any other physical quantity (for example, condensing temperature) that is convertible to the high pressure P H of the low-stage refrigerant, such that the controller 3 converts the detected physical quantity to the high pressure P H .
  • the refrigeration cycle apparatus 100 may further include various types of sensors (not illustrated) such as an outside-air temperature sensor configured to detect an outside-air temperature, a room temperature sensor configured to detect a temperature in the freezer compartment, or a sensor configured to detect a refrigerant temperature or pressure at any location in the high-stage circuit 1 and the low-stage circuit 2.
  • the controller 3 controls operation of the refrigeration cycle apparatus 100 in its entirety.
  • the controller 3 is constituted by a processing device including a memory configured to store data and programs necessary for controlling the operation, and a CPU configured to execute the programs, or is constituted by dedicated hardware such as ASIC or FPGA or by both the processing device and the dedicated hardware.
  • the controller 3 in the present embodiment controls the high-stage circuit 1 based on the high pressure P H of the low-stage refrigerant detected by the pressure sensor 26.
  • the controller 3 controls the respective devices in the high-stage circuit 1 and the low-stage circuit 2 as well as the first fan 15 and the second fan 25 based on the information received from the various types of sensors and an operating instruction given by a user.
  • Operation of the refrigeration cycle apparatus 100 in the present embodiment is described below based on a flow of refrigerant circulating in each refrigerant circuit.
  • operation of the high-stage circuit 1 is described.
  • the first compressor 11 and the second compressor 21 are driven upon receiving an instruction to start operation of the refrigeration cycle apparatus 100.
  • the first compressor 11 in the high-stage circuit 1 suctions the high-stage refrigerant, compresses the suctioned high-stage refrigerant into a high-temperature high-pressure state, and discharges the compressed high-stage refrigerant.
  • the high-stage refrigerant discharged from the first compressor 11 flows into the condenser 12.
  • the condenser 12 is configured to exchange heat between air supplied by the first fan 15 and the high-stage refrigerant, and condense and liquefies the high-stage refrigerant.
  • the high-stage refrigerant condensed and liquefied through the condenser 12 passes through the first expansion device 13.
  • the first expansion device 13 reduces the pressure of the condensed and liquefied high-stage refrigerant.
  • the high-stage refrigerant with its pressure reduced by the first expansion device 13 flows into the high-stage flow passage 141 in the cascade heat exchanger 14.
  • the high-stage refrigerant flowing into the high-stage flow passage 141 exchanges heat with the low-stage refrigerant flowing through the low-stage flow passage 142 in the cascade heat exchanger 14, and is thus evaporated and gasified.
  • the high-stage refrigerant evaporated and gasified in the cascade heat exchanger 14 is suctioned into the first compressor 11 again.
  • the second compressor 21 in the low-stage circuit 2 suctions the low-stage refrigerant, compresses the suctioned low-stage refrigerant into a high-temperature high-pressure state, and discharges the compressed low-stage refrigerant.
  • the low-stage refrigerant discharged from the second compressor 21 flows into the low-stage flow passage 142 in the cascade heat exchanger 14.
  • the low-stage refrigerant flowing into the low-stage flow passage 142 exchanges heat with the high-stage refrigerant flowing through the high-stage flow passage 141 in the cascade heat exchanger 14, and is thus condensed and liquefied.
  • the low-stage refrigerant condensed and liquefied through the cascade heat exchanger 14 flows into the receiver 22.
  • the low-stage refrigerant flowing out from the receiver 22 passes through the second expansion device 23.
  • the second expansion device 23 reduces the pressure of the low-stage refrigerant.
  • the low-stage refrigerant with its pressure reduced by the second expansion device 23 flows into the evaporator 24.
  • the evaporator 24 is configured to exchange heat between air supplied by the second fan 25 and the low-stage refrigerant, and evaporate and gasify the low-stage refrigerant. At this time, the low-stage refrigerant removes heat from the air, so that the freezer compartment is cooled.
  • the low-stage refrigerant evaporated and gasified through the evaporator 24 is suctioned into the second compressor 21 again.
  • the ratio of R290 that is a flammable refrigerant increases in the circulation composition of the low-stage refrigerant. This increases the flammability of the low-stage refrigerant circulating in the low-stage circuit 2, and accordingly increases the risk due to the flammability at the time of refrigerant leakage.
  • the controller 3 in the present embodiment controls the capacity of the high-stage circuit 1 to maintain the high pressure P H of the low-stage refrigerant to be equal to or lower than a pressure value at or below which the low-stage refrigerant is non-flammable.
  • Fig. 2 is a graph illustrating the relationship between flammability and the high pressure P H of the low-stage refrigerant.
  • Fig. 2 is a graph when the low-stage refrigerant is a zeotropic refrigerant mixture in which refrigerant having a higher-boiling-point is flammable as described in the present embodiment. As illustrated in Fig.
  • the high pressure P H of the low-stage refrigerant needs to be equal to or lower than a threshold P T to maintain the low-stage refrigerant to be non-flammable.
  • the threshold P T is uniquely determined by physical properties of refrigerants that constitute the low-stage refrigerant.
  • the threshold P T is set in advance appropriate to the low-stage refrigerant and stored in the controller 3.
  • the controller 3 controls the capacity of the high-stage circuit 1 such that the high pressure P H of the low-stage refrigerant detected by the pressure sensor 26 is equal to or lower than the threshold P T .
  • Fig. 3 is a flowchart illustrating operation of the refrigeration cycle apparatus 100 according to Embodiment 1.
  • the controller 3 drives the first compressor 11 and the second compressor 21 (S1). This causes the high-stage refrigerant to circulate in the high-stage circuit 1, and causes the low-stage refrigerant to circulate in the low-stage circuit 2, so that the freezer compartment is cooled.
  • the pressure sensor 26 detects the high pressure P H of the low-stage refrigerant (S2).
  • the controller 3 determines whether the high pressure P H of the low-stage refrigerant detected by the pressure sensor 26 is equal to or lower than the threshold P T (S3).
  • the controller 3 maintains the capacity of the high-stage circuit 1 and shifts to step S5.
  • the controller 3 increases the capacity of the high-stage circuit 1 (S4).
  • the controller 3 increases the operating frequency of the first compressor 11 in the high-stage circuit 1.
  • the controller 3 may increase the operating frequency of the first compressor 11 by a predetermined constant value, or may increase it by a value corresponding to a difference between the high pressure P H of the low-stage refrigerant and the threshold P T .
  • the temperature of the high-stage refrigerant flowing through the high-stage flow passage 141 in the cascade heat exchanger 14 is decreased.
  • the temperature of the low-stage refrigerant that exchanges heat with the high-stage refrigerant through the cascade heat exchanger 14 is decreased, and accordingly the high pressure P H of the low-stage refrigerant is decreased.
  • the high pressure P H of the low-stage refrigerant is decreased, the density of the gas in the receiver 22 is decreased, and accordingly the mass of the gas refrigerant in the receiver 22 is reduced.
  • the controller 3 determines whether to stop operation of the refrigeration cycle apparatus 100 upon receiving an instruction from a user or other information (S5). When the controller 3 does not stop operation of the refrigeration cycle apparatus 100 (S5: NO), the controller 3 returns to step S2 to repeat the subsequent processes. In contrast, when the controller 3 stops operation of the refrigeration cycle apparatus 100 (S5: YES), the controller 3 deactivates the first compressor 11 and the second compressor 21 (S6). With this control, during operation of the refrigeration cycle apparatus 100, the high pressure P H of the low-stage refrigerant is maintained to be equal to or lower than the threshold P T .
  • the high-stage circuit 1 is controlled in such a manner that the high pressure P H of the low-stage refrigerant is equal to or lower than the threshold P T at or below which the low-stage refrigerant is non-flammable.
  • This can reduce variations in the composition of the low-stage refrigerant flowing out from the receiver 22 and circulating in the low-stage circuit 2.
  • a zeotropic refrigerant mixture containing a flammable refrigerant is used as the low-stage refrigerant, it is still possible to suppress the increase in risk due to the flammability at the time of refrigerant leakage.
  • the freezing point of CO 2 can be decreased. This makes it possible to achieve cooling at the freezing point (-56 degrees C) or lower.
  • Fig. 4 is a flowchart illustrating operation of the refrigeration cycle apparatus 100 according to Embodiment 2.
  • the refrigeration cycle apparatus 100 after receiving an instruction to stop operation, the refrigeration cycle apparatus 100 operates differently from Embodiment 1.
  • the configuration of the refrigeration cycle apparatus 100 is the same as that in Embodiment 1.
  • the refrigeration cycle apparatus 100 performs processes (steps S1 to S4) in the same manner as in Embodiment 1 during its operation.
  • the controller 3 determines whether to stop operation of the refrigeration cycle apparatus 100 upon receiving an instruction from a user or other information (S5). When the controller 3 does not stop the operation (S5: NO), the controller 3 returns to step S2 to repeat the subsequent processes.
  • the controller 3 stops operation of the refrigeration cycle apparatus 100 (S5: YES)
  • the controller 3 performs pump-down operation on the low-stage circuit 2 (S11).
  • the controller 3 fully closes the second expansion device 23, while continuously driving the second compressor 21. Since the second expansion device 23 located downstream of the receiver 22 is closed, the low-stage refrigerant in the low-stage circuit 2 is collected into the low-stage flow passage 142 in the cascade heat exchanger 14 and into the receiver 22. Thereafter, the controller 3 deactivates the second compressor 21 (S12). This causes circulation of the low-stage refrigerant in the low-stage circuit 2 to stop.
  • a solenoid valve may be provided between the refrigerant outlet of the receiver 22 and the second expansion device 23 to perform the pump-down operation by closing the solenoid valve.
  • a pressure sensor configured to detect a low pressure of the low-stage refrigerant may be provided in a low-pressure side of the low-stage circuit 2.
  • the low-pressure side of the low-stage circuit 2 is between the refrigerant outlet of the second expansion device 23 and a suction port of the second compressor 21.
  • the second compressor 21 may be deactivated. This can prevent a fault or other problems caused by continuously driving the second compressor 21 even after there is no refrigerant left on the low-pressure side of the low-stage circuit 2.
  • the pressure sensor 26 detects the high pressure P H of the low-stage refrigerant (S13).
  • the controller 3 determines whether the high pressure P H of the low-stage refrigerant detected by the pressure sensor 26 is equal to or lower than the threshold P T (S14).
  • the controller 3 maintains the capacity of the high-stage circuit 1 and shifts to step S16.
  • the controller 3 increases the capacity of the high-stage circuit 1 (S15). Specifically, similarly to Embodiment 1, the controller 3 increases the operating frequency of the first compressor 11 in the high-stage circuit 1.
  • the low-boiling-point refrigerant is still gasified in the receiver 22 in the low-stage circuit 2, which may vary the composition of liquid refrigerant in the receiver 22.
  • CO 2 which is the refrigerant having a low-boiling-point is gasified in the receiver 22
  • the ratio of R290 that is a flammable refrigerant increases in the composition of the liquid refrigerant in the receiver 22.
  • the high-stage circuit 1 is controlled in such a manner that the high pressure P H of the low-stage refrigerant is equal to or lower than the threshold P T at or below which the low-stage refrigerant is non-flammable, even after the low-stage circuit 2 is deactivated.
  • the temperature of the low-stage refrigerant accumulated in the low-stage flow passage 142 in the cascade heat exchanger 14 is decreased, and accordingly the high pressure P H of the low-stage refrigerant is decreased.
  • the low-stage refrigerant with its temperature decreased in the cascade heat exchanger 14 flows into the receiver 22 by natural convection in such a manner as to maintain the balance between temperature and pressure.
  • the gas density in the receiver 22 is decreased, and accordingly the mass of gas refrigerant in the receiver 22 is reduced.
  • the gas amount of the refrigerant having the low-boiling-point (CO 2 ) in the receiver 22 is reduced. This can minimize variations in the composition of the liquid refrigerant in the receiver 22.
  • the controller 3 determines whether to start operation of the refrigeration cycle apparatus 100 upon receiving an instruction from a user or other information (S16). When the controller 3 does not start operation of the refrigeration cycle apparatus 100 (S16: NO), the controller 3 returns to step S13 to repeat the subsequent processes. When the controller 3 starts operation of the refrigeration cycle apparatus 100 (S16: YES), the controller 3 shifts to step S1 and drives the second compressor 21 to cause the low-stage refrigerant to circulate in the low-stage circuit 2.
  • the refrigeration cycle apparatus 100 in the present embodiment can still reduce variations in the composition of the liquid refrigerant accumulating in the receiver 22 even when the refrigeration cycle apparatus 100 is deactivated, in addition to achieving the same effects as those obtained in Embodiment 1.
  • a zeotropic refrigerant mixture containing a flammable refrigerant is used as the low-stage refrigerant, it is still possible to suppress the increase in risk due to the flammability at the time of refrigerant leakage from the receiver 22.
  • the low-stage refrigerant is not limited to the zeotropic refrigerant mixture of CO 2 and R290, but may be other zeotropic refrigerant mixtures.
  • the low-stage refrigerant is the zeotropic refrigerant mixture containing CO 2 and a flammable refrigerant, the effects achieved by the above embodiments can be particularly obtained.
  • the refrigeration cycle apparatus 100 has the configuration in which the controller 3 controls the refrigeration cycle apparatus 100 in its entirety.
  • the controller 3 may be provided in each of the high-stage circuit 1 and the low-stage circuit 2, such that the controllers 3 individually control operation of the high-stage circuit 1 and operation of the low-stage circuit 2.
  • the refrigeration cycle apparatus 100 has the configuration in which the controller 3 controls the operating frequency of the first compressor 11 to thereby control the capacity of the high-stage circuit 1.
  • the refrigeration cycle apparatus 100 is not limited to having this configuration.
  • the controller 3 may control the opening degree of the first expansion device 13 or the rotation speed of the first fan 15 in the high-stage circuit 1 to thereby control the capacity of the high-stage circuit 1.
  • the controller 3 increases the opening degree of the first expansion device 13 or the rotation speed of the first fan 15 to thereby increase the capacity of the high-stage circuit 1.
  • the refrigeration cycle apparatus 100 has the configuration in which the controller 3 controls the high-stage circuit 1 based on the high pressure P H of the low-stage refrigerant detected by the pressure sensor 26.
  • the refrigeration cycle apparatus 100 is not limited to having this configuration.
  • the controller 3 may control the high-stage circuit 1 based on the condensing temperature of the low-stage refrigerant associated with the high pressure P H of the low-stage refrigerant.
  • the controller 3 may control the high-stage circuit 1 based on the cooling load on the low-stage circuit 2 to thereby maintain the high pressure P H of the low-stage refrigerant to be equal or lower than a pressure value at or below which the low-stage refrigerant is non-flammable.
  • the cooling load on the low-stage circuit 2 is calculated based on the room temperature or other factors of the freezer compartment or other targets to be cooled.
  • the controller 3 increases the capacity of the high-stage circuit 1, and when the cooling load on the low-stage circuit 2 decreases, the controller 3 reduces the capacity of the high-stage circuit 1.
  • the capacity of the high-stage circuit 1 still increases, so that it is possible to reduce the high pressure P H of the low-stage refrigerant.
  • the high pressure P H of the low-stage refrigerant can be maintained to be equal to or lower than a pressure value at or below which the low-stage refrigerant is non-flammable.
  • the pressure sensor 26 may be omitted, or a control based on the high pressure P H of the low-stage refrigerant detected by the pressure sensor 26 may be combined with the present modification.
  • the low-stage circuit 2 may be provided with a pressure relief device configured to be open when the pressure or temperature increases to a reference value, and the pressure relief device is used to maintain the high pressure P H of the low-stage refrigerant to be equal to or lower than a pressure value at or below which the low-stage refrigerant is non-flammable.
  • Fig. 5 is a schematic configuration diagram of a refrigeration cycle apparatus 100A according to the modification. As illustrated in Fig. 5 , the refrigeration cycle apparatus 100A includes a pressure relief device 27.
  • the pressure relief device 27 is provided in a refrigerant pipe on the high-pressure side of the low-stage circuit 2 or in the receiver 22.
  • the pressure relief device 27 is a pressure relief valve or a fusible plug.
  • the threshold P T refers to a pressure value or a temperature at or below which the low-stage refrigerant is non-flammable, similarly to the above embodiments. This helps maintain the high pressure P H of the low-stage refrigerant to be equal to or lower than the pressure value at or below which the low-stage refrigerant is non-flammable.
  • a control of the high-stage circuit 1 based on the high pressure P H of the low-stage refrigerant detected by the pressure sensor 26, or a control of the high-stage circuit 1 based on the cooling load may be omitted, or these controls may be combined with the present modification.
  • 1 high-stage circuit
  • 2 low-stage circuit
  • 3 controller
  • 11 first compressor
  • 12 condenser
  • 13 first expansion device
  • 14 cascade heat exchanger
  • 15 first fan
  • 21 second compressor
  • 22 receiver
  • 23 second expansion device
  • 24 evaporator
  • 25 second fan
  • 26 pressure sensor
  • 27 pressure relief device
  • 100 100A: refrigeration cycle apparatus
  • 141 high-stage flow passage
  • 142 low-stage flow passage

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Compression-Type Refrigeration Machines With Reversible Cycles (AREA)
  • Devices That Are Associated With Refrigeration Equipment (AREA)
EP21952785.0A 2021-08-05 2021-08-05 Kältekreislaufvorrichtung und kältekreislaufsteuerungsverfahren Pending EP4382827A1 (de)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/JP2021/029052 WO2023012960A1 (ja) 2021-08-05 2021-08-05 冷凍サイクル装置、及び冷凍サイクル装置の制御方法

Publications (1)

Publication Number Publication Date
EP4382827A1 true EP4382827A1 (de) 2024-06-12

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EP (1) EP4382827A1 (de)
JP (1) JPWO2023012960A1 (de)
CN (1) CN117716185A (de)
WO (1) WO2023012960A1 (de)

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001019944A (ja) * 1999-07-09 2001-01-23 Matsushita Electric Ind Co Ltd 低温作動流体とそれを用いた冷凍サイクル装置
JP2008215672A (ja) * 2007-03-01 2008-09-18 Mac:Kk 可燃性冷媒ガスを使用する冷凍サイクルの残留ガス回収方法及びその装置
JP5323023B2 (ja) * 2010-10-19 2013-10-23 三菱電機株式会社 冷凍装置
JP5627416B2 (ja) * 2010-11-26 2014-11-19 三菱電機株式会社 二元冷凍装置
JPWO2014030236A1 (ja) 2012-08-23 2016-07-28 三菱電機株式会社 冷凍装置
EP2910870B1 (de) * 2012-09-21 2020-01-01 Mitsubishi Electric Corporation Kühlvorrichtung und verfahren zur steuerung davon
JP5963969B2 (ja) * 2013-09-27 2016-08-03 パナソニックヘルスケアホールディングス株式会社 冷凍装置
US10254016B2 (en) * 2014-03-17 2019-04-09 Mitsubishi Electric Corporation Refrigeration cycle apparatus and method for controlling refrigeration cycle apparatus
WO2018198203A1 (ja) * 2017-04-25 2018-11-01 三菱電機株式会社 二元冷凍装置

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Publication number Publication date
CN117716185A (zh) 2024-03-15
JPWO2023012960A1 (de) 2023-02-09
WO2023012960A1 (ja) 2023-02-09

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