EP4113035B1 - Freezing device, freezing system, and control method of freezing device - Google Patents

Freezing device, freezing system, and control method of freezing device Download PDF

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Publication number
EP4113035B1
EP4113035B1 EP22181615.0A EP22181615A EP4113035B1 EP 4113035 B1 EP4113035 B1 EP 4113035B1 EP 22181615 A EP22181615 A EP 22181615A EP 4113035 B1 EP4113035 B1 EP 4113035B1
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EP
European Patent Office
Prior art keywords
refrigerant
pressure
compressor
gas cooler
control
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.)
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Application number
EP22181615.0A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP4113035A1 (en
EP4113035C0 (en
Inventor
Kosei Nishimura
Kenichi Murakami
Takahide Goto
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Heavy Industries Thermal Systems Ltd
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Mitsubishi Heavy Industries Thermal Systems Ltd
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Publication of EP4113035C0 publication Critical patent/EP4113035C0/en
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Classifications

    • 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
    • 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
    • F25B2500/00—Problems to be solved
    • F25B2500/31—Low ambient temperatures
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/19—Pressures
    • F25B2700/193—Pressures of the compressor
    • F25B2700/1931—Discharge pressures
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/19—Pressures
    • F25B2700/193—Pressures of the compressor
    • F25B2700/1933—Suction pressures
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2106—Temperatures of fresh outdoor air
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2115—Temperatures of a compressor or the drive means therefor
    • F25B2700/21151—Temperatures of a compressor or the drive means therefor at the suction side of the compressor
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2115—Temperatures of a compressor or the drive means therefor
    • F25B2700/21152—Temperatures of a compressor or the drive means therefor at the discharge side of the compressor
    • 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
    • F25B6/00—Compression machines, plants or systems, with several condenser circuits
    • F25B6/02—Compression machines, plants or systems, with several condenser circuits arranged in parallel

Definitions

  • the present invention relates to a freezing device, a freezing system, and a control method of a freezing device.
  • Japanese Patent Application Laid-Open No. 2008-530501 discloses a cooling circuit with use of a carbon dioxide (CO 2 ) refrigerant.
  • the cooling circuit of Japanese Patent Application Laid-Open No. 2008-530501 performs control by switching the mode between a transcritical mode in which the CO 2 refrigerant is in a transcritical state in a gas cooler and a subcritical mode in which the CO 2 refrigerant is in a subcritical state.
  • the high-pressure value of the CO 2 refrigerant may be greater than is required relative to an amount of exhaust heat required to be removed by a gas cooler. Further, since the rotational rate of a compressor is increased in order to have the transcritical mode, power loss is increased. Due to the above, there is a drive state where the thermal efficiency is reduced in relation to the outside air temperature.
  • a target evaporation temperature in an evaporator is determined by a request from equipment that uses cold generated by the evaporator. Under the determined target evaporation temperature, it is required to ensure a difference between high and low pressures of a refrigerant required for obtaining predetermined freezing performance.
  • the present disclosure has been made in view of such circumstances, and an object is to provide a freezing device, a freezing system, and a control method of a freezing device that can improve thermal efficiency even in a low outside air temperature and obtain required freezing performance.
  • the freezing device, the freezing system, and the control method of the freezing device of the present invention employ the following solutions.
  • the freezing device of the present invention as defined in claim 1 includes: a compressor configured to compress a CO 2 refrigerant; a gas cooler configured to cool a CO 2 refrigerant discharged from the compressor; and a control unit configured to set a high-pressure target value of the CO 2 refrigerant so that the CO 2 refrigerant in the gas cooler becomes subcritical and perform subcritical control when an outside air temperature is less than a first predetermined temperature, which is lower than the critical point of the CO 2 refrigerant, and a target evaporation temperature in an evaporator to which the CO 2 refrigerant cooled by the gas cooler is guided via an expansion valve is less than or equal to a second predetermined temperature.
  • the freezing system of the present invention includes: the freezing device described in any of the above; an expansion valve configured to expand a CO 2 refrigerant supplied from the gas cooler; and an evaporator configured to evaporate the CO 2 refrigerant guided from the expansion valve.
  • the control method of a freezing device of the present invention as defined in claim 6 is a control method of a freezing device including a compressor configured to compress a CO 2 refrigerant, and a gas cooler configured to cool a CO 2 refrigerant discharged from the compressor, and the control method includes: setting a high-pressure target value of a CO 2 refrigerant so that a CO 2 refrigerant in the gas cooler becomes subcritical and performing subcritical control when an outside air temperature is less than a first predetermined temperature, which is lower than the critical point of the CO 2 refrigerant, and a target evaporation temperature in an evaporator to which the CO 2 refrigerant cooled by the gas cooler is guided via an expansion valve is less than or equal to a second predetermined temperature.
  • the freezing system of the present invention includes a condensing unit (freezing device) 1 and a load device 2. As illustrated in Fig. 1 , a refrigerant circuit of the condensing unit 1 is illustrated.
  • the condensing unit 1 supplies a liquid refrigerant to the load device 2.
  • carbon dioxide (CO 2 ) is used as the refrigerant.
  • the CO 2 refrigerant is not limited to a single refrigerant in which the content of CO 2 is 100% and may be a mixture refrigerant whose main component is CO 2 as long as the refrigerant has mainly properties of a CO 2 refrigerant.
  • the load device 2 may be, for example, a refrigerator or a freezer that cools or refrigerates and stores products and refrigerating/freezing equipment such as a showcase that cools or refrigerates and displays products.
  • the load device 2 can be any device that supplies cold and may be used for interior equipment of an air-conditioner, for example.
  • the load device 2 is supplied with a liquid refrigerant from the condensing unit 1.
  • the load device 2 includes an evaporator 6, a low-stage expansion valve 8, a temperature sensor (not illustrated), and the like.
  • a target evaporation temperature set in the evaporator 6 is set by a user, for example, and is stored in a control unit (not illustrated).
  • a plurality of load devices 2 may be provided in parallel to each other.
  • the condensing unit 1 includes a compressor 3, gas coolers 5, a high-stage expansion valve 7, and intermediate-pressure receivers 9.
  • the compressor 3, the gas coolers 5, the high-stage expansion valve 7, and the intermediate-pressure receivers 9 are connected to each other by refrigerant pipes.
  • the compressor 3 compresses the refrigerant supplied from the load device 2 via an accumulator 13 by an intake tube 11.
  • the intake tube 11 includes a low-pressure sensor 12 on the inlet side of the accumulator 13 and includes an intake tube temperature sensor 14 on the inlet side of the compressor 3. Measurement values of the low-pressure sensor 12 and the intake tube temperature sensor 14 are transmitted to the control unit.
  • the compressor 3 is a two-stage compressor and includes a low-stage compressor on the first stage and a high-stage compressor on the second stage.
  • the low-stage compressor compresses a drawn refrigerant guided from the accumulator 13 to an intermediate pressure.
  • the high-stage compressor further compresses the refrigerant compressed to the intermediate pressure by the low-stage compressor to a high pressure.
  • a rotary compressor is used, for example, and as the high-stage compressor, a scroll compressor is used, for example.
  • the displacement volume of the low-stage compressor is 15 cc/rev, for example, and the displacement volume of the high-stage compressor is 13 cc/rev, for example.
  • the inside of a housing 3a of the compressor 3 is filled with the intermediate-pressure refrigerant discharged from the low-stage compressor.
  • the compressor 3 includes an electric motor (not illustrated), and the rotational rate is variable with inverter control. The rotational rate of the compressor 3 is controlled by the control unit.
  • an under-dome temperature sensor 4 is provided in the housing 3a of the compressor 3. A measurement value of the under-dome temperature sensor 4 is transmitted to the control unit.
  • a high-pressure and high-temperature refrigerant is supplied to the gas cooler 5 via an oil separator 15.
  • the gas cooler 5 is a fin tube, for example, and performs heat exchange between the supplied high-pressure and high-temperature refrigerant and the air supplied by a fan 17 to cool the refrigerant.
  • a plurality of (in the present embodiment, two) gas coolers are provided in parallel to each other.
  • the high-stage expansion valve 7 is provided on the inlet side of the intermediate-pressure receivers 9 and expands the refrigerant cooled in the gas coolers 5.
  • the high-stage expansion valve 7 is an electronic expansion valve, and the opening is controlled by the control unit.
  • Each intermediate-pressure receiver 9 separates the refrigerant expanded in the high-stage expansion valve 7 into a gas refrigerant and a liquid refrigerant.
  • the plurality of (in the present embodiment, two) intermediate-pressure receivers 9 are provided in parallel to each other.
  • a liquid feeding tube 19 and an injection circuit 21 are connected to the intermediate-pressure receivers 9.
  • the liquid refrigerant separated in the intermediate-pressure receivers 9 is supplied to the external load device 2 through the liquid feeding tube 19.
  • a supercooling coil 23 is provided in the liquid feeding tube 19.
  • heat is exchanged with a refrigerant expanded by a supercooling coil electronic expansion valve 27 through a branch tube 25 branched from the liquid feeding tube 19. Accordingly, supercooling is provided to the liquid refrigerant fed to the external load device 2.
  • the downstream end of the branch tube 25 passing through the supercooling coil 23 is connected to the accumulator 13.
  • the gas refrigerant separated in the intermediate-pressure receiver 9 is guided to the inside of the housing 3a of the compressor 3 via the injection circuit 21.
  • an intermediate-pressure sensor 31 and an intermediate-pressure intake electromagnetic valve 33 are provided in the injection circuit 21.
  • a measurement value of the intermediate-pressure sensor 31 is transmitted to the control unit. Opening and closing of the intermediate-pressure intake electromagnetic valve 33 is controlled by the control unit.
  • the oil separator 15 is provided in a discharge tube 35 connected to the discharge side of the high-stage compressor of the compressor 3.
  • a discharge temperature sensor 37 is provided, and a measurement value of the discharge temperature sensor 37 is transmitted to the control unit.
  • the oil separator 15 collects a lubricating oil included in a discharge refrigerant.
  • the upstream end of an oil return tube 39 is connected to the bottom of the oil separator 15.
  • the downstream end that is the other end of the oil return tube 39 is connected to the compressor 3.
  • an oil return electromagnetic valve 41 and a capillary 43 as a regulation unit are provided in the oil return tube 39. Opening and closing of the oil return electromagnetic valve 41 is controlled by the control unit.
  • a high-pressure refrigerant from which the lubricating oil has been removed by the oil separator 15 is guided to the gas cooler 5 via a high-pressure gas pipe 45.
  • a check valve 47, and a high-pressure sensor 49 are provided in this order from the upstream.
  • a gas cooler inlet temperature sensor 51 is provided on the gas cooler 5 side of the high-pressure gas pipe 45. Measurement values of the high-pressure sensor 49 and the gas cooler inlet temperature sensor 51 are transmitted to the control unit.
  • the condensing unit 1 includes an outside air temperature sensor 53 that measures an outside air temperature. A measurement value of the outside air temperature sensor 53 is transmitted to the control unit.
  • the control unit is formed of a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), a computer readable storage medium, and the like, for example. Further, a series of processes for implementing respective functions is stored in a storage medium or the like in a form of a program as one example, and when the CPU loads the program into the RAM or the like and performs a processing and calculation process on information, respective functions are implemented.
  • an applicable form of the program may be a form in which a program is installed in advance in a ROM or another storage medium, a form in which a program is provided in a state of being stored in a computer readable storage medium, a form in which a program is delivered via a wired or wireless communication scheme, or the like.
  • the computer readable storage medium may be a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.
  • Fig. 3 is a pressure-enthalpy (p-h) diagram in which the horizontal axis corresponds to a specific enthalpy, and the vertical axis corresponds to a pressure, and illustrates the operation of the freezing device.
  • the transcritical control is illustrated by the dashed line in Fig. 3 , which means that the refrigerant CO 2 refrigerant) is in the transcritical state in the gas cooler 5.
  • the dash-dot line represents a saturation vapor line and a saturation liquid line of CO 2 .
  • CO 2 is in the transcritical state in the gas cooler 5.
  • the refrigerant guided via the intake tube 11 is drawn into the low-stage compressor of the compressor 3 under intake pressure P1 (state S1).
  • the pressure of the drawn refrigerant is increased to intermediate pressure P2 in the low-stage compressor (state S2).
  • the refrigerant whose pressure has been increased to intermediate pressure P2 is discharged into the housing 3a.
  • the intermediate-pressure refrigerant guided from the intermediate-pressure receiver 9 via the injection circuit 21 is guided into the housing 3a.
  • the pressure of the intermediate-pressure refrigerant in the housing 3a is increased to high pressure P3 by the high-stage compressor (state S3).
  • the high-pressure refrigerant whose pressure has been increased is guided to the oil separator 15 via the discharge tube 35 and a lubricating oil in the refrigerant is separated therefrom.
  • the refrigerant from which the oil has been removed by the oil separator 15 passes through the high-pressure gas pipe 45 and is guided to the gas cooler 5.
  • the refrigerant is cooled by being subjected to heat exchange with air (outside air) supplied by the fan 17 (state S4). At this time, the refrigerant is in the transcritical state.
  • the refrigerant that has left from the gas cooler 5 is expanded to intermediate pressure P2 by the high-stage expansion valve 7 and guided to the intermediate-pressure receiver 9.
  • the liquid refrigerant taken out from the intermediate-pressure receiver 9 passes through the liquid feeding tube 19 and is then supercooled by the supercooling coil 23 (state S5).
  • the liquid refrigerant is then fed to the external load device 2.
  • the liquid refrigerant is expanded to intake pressure P1 by the low-stage expansion valve 8 (state S6) and fed to the evaporator 6.
  • the refrigerant removes heat from the load and evaporates into a gas refrigerant. Evaporation latent heat generated in the evaporator 6 is taken out as a freezing load.
  • the gas refrigerant that has left from the evaporator 6 is returned to the condensing unit 1 and again fed to the compressor 3 via the intake tube 11.
  • the subcritical control is illustrated by the solid line in Fig. 3 , which means that the refrigerant (CO 2 refrigerant) is in a subcritical state in the gas cooler 5. That is, in the subcritical control, high pressure P3' is a pressure lower than that at the critical point CP, and a gas-liquid two-phase state is in the gas cooler 5.
  • step 102 If the temperature measured by the outside air temperature sensor 53 is less than a first predetermined temperature (step 102) and a target evaporation temperature is less than or equal to a second predetermined temperature (step 103) in the operation under the transcritical control (step 101), the control is switched to the subcritical control after step 104 by an instruction from the control unit.
  • the first predetermined temperature is 18 °C, for example.
  • the first predetermined temperature is variable in accordance with the capacity of the freezing system or the like and is set to a temperature that is less than the critical temperature (31.1 °C) of CO 2 and at which the thermal efficiency of the freezing system is greater than that in the transcritical control.
  • the first predetermined temperature is determined by a test operation or a simulation in advance, for example. When the outside air temperature is greater than or equal to the first predetermined temperature, the process returns to step 101 from step 102, and the transcritical control is maintained.
  • the second predetermined temperature is -10 °C, for example.
  • the second predetermined temperature is a temperature set by the user and is set as a target value for the control unit.
  • the target evaporation temperature is greater than the second predetermined temperature, a difference between high and low pressures is small, the bore diameter of an expansion valve is insufficient, and a differential pressure required for the operation of the compressor is not ensured. In such a case, the process returns to step 101 from step 103, and the transcritical control is maintained.
  • step 104 the control unit sets a high-pressure target value to the value for the subcritical state. Specifically, as illustrated in Fig. 3 , the control unit sets a high-pressure target value from high pressure P3 to high pressure P3'.
  • the high-pressure target value that is a set value is stored in the control unit.
  • step 105 the rotational rate of the fan 17 is adjusted by an instruction from the control unit.
  • the CO 2 refrigerant is operated under the subcritical state, since the work of the compressor decreases compared to a case of being operated under the transcritical state, the amount of exhaust heat from the gas cooler also decreases. Since electric power consumption is determined by the work of the compressor and the fan, the fan rotational rate is adjusted so that the electric power consumption decreases.
  • the pressure in the gas cooler 5 decreases from high pressure P3 to high pressure P3', and intermediate pressure P2 also tends to decrease. Since the temperature in the compressor 3 decreases in response to a decrease in intermediate pressure P2, an oil temperature in the compressor 3 decreases. When the oil temperature decreases, the refrigerant is easily dissolved, and the dilution ratio increases. When the dilution ratio increases, the viscosity of the oil decreases, and an oil film is not ensured, and this may lead to damage of a sliding portion.
  • This protection control makes it possible not only to protect the compressor 3 but also to prevent liquid back where a liquid refrigerant is drawn into the intake side of the compressor 3.
  • the outside air temperature is less than the first predetermined temperature (for example, -18 °C) that is lower than the critical point CP of CO 2 , even if the operation is performed so that the CO 2 refrigerant in the gas cooler 5 becomes transcritical, the difference between high and low pressures of the CO 2 refrigerant may be greater than is required and the thermal efficiency may decrease.
  • the first predetermined temperature for example, -18 °C
  • the target evaporation temperature in the evaporator is less than or equal to the second predetermined temperature (for example, -10 °C) and the difference between high and low pressures of the CO 2 refrigerant can be ensured, a thermally efficient operation can be realized by setting the high-pressure target value of the CO 2 refrigerant to be lower so that the CO 2 refrigerant in the gas cooler 5 becomes subcritical and reducing the load on the compressor 3.
  • the second predetermined temperature for example, -10 °C
  • the freezing device, the freezing system, and the control method of a freezing device according to respective embodiments described above are recognized as follows, for example.
  • the freezing device of the present invention includes: a compressor (3) configured to compress a CO 2 refrigerant; a gas cooler (5) configured to cool a CO 2 refrigerant discharged from the compressor (3); and a control unit configured to set a high-pressure target value of the CO 2 refrigerant so that the CO 2 refrigerant in the gas cooler becomes subcritical and perform subcritical control when an outside air temperature is less than a first predetermined temperature, which is lower than the critical point of the CO 2 refrigerant, and a target evaporation temperature in an evaporator (6) to which the CO 2 refrigerant cooled by the gas cooler is guided via an expansion valve (7, 8) is less than or equal to a second predetermined temperature.
  • the difference between high and low pressures of the CO 2 refrigerant may be greater than is required and the thermal efficiency may decrease. Accordingly, when the target evaporation temperature in the evaporator is less than or equal to the second predetermined temperature and the difference between high and low pressures of the CO 2 refrigerant can be ensured, a thermally efficient operation is realized by setting the high-pressure target value of the CO 2 refrigerant to be lower so that the CO 2 refrigerant in the gas cooler becomes subcritical, performing the subcritical control, and reducing the load on the compressor.
  • the first predetermined temperature may be, for example, 18 °C
  • the second predetermined temperature may be, for example, -10 °C.
  • the CO 2 refrigerant is not limited to a single refrigerant in which the content of CO 2 is 100% and may be a mixture refrigerant whose main component is CO 2 as long as the refrigerant has mainly properties of a CO 2 refrigerant.
  • the control unit sets the high-pressure target value so that the CO 2 refrigerant in the gas cooler becomes transcritical and performs transcritical control.
  • the high-pressure target value is increased to obtain a difference between the high and low pressures corresponding to the amount of exhaust heat required for the gas cooler, and the CO 2 refrigerant is operated under the transcritical state.
  • the freezing device of the present disclosure includes a fan (17) configured to supply cooling air to the gas cooler, and when the subcritical control is performed, the control unit adjusts rotational rate of the fan.
  • the compressor includes a low-stage compressor configured to compress a refrigerant guided from the evaporator to an intermediate pressure and a high-stage compressor configured to draw in and compress the refrigerant, which was compressed to the intermediate pressure by the low-stage compressor, to a high pressure, and the control unit performs control so that discharge pressure of the high-stage compressor becomes the high-pressure target value.
  • the compressor is a two-stage compressor including a low-stage compressor and a high-stage compressor
  • the discharge pressure of the high-stage compressor is controlled to become a high-pressure target value.
  • the freezing system of the present invention includes: the freezing device described in any of the above; an expansion valve configured to expand a CO 2 refrigerant supplied from the gas cooler; and an evaporator configured to evaporate the CO 2 refrigerant guided from the expansion valve.
  • the control method of a freezing device of the present invention is a control method of a freezing device including a compressor configured to compress a CO 2 refrigerant, and a gas cooler configured to cool a CO 2 refrigerant discharged from the compressor, and the control method includes: setting a high-pressure target value of a CO 2 refrigerant so that a CO 2 refrigerant in the gas cooler becomes subcritical and performing subcritical control when an outside air temperature is less than a first predetermined temperature, which is lower than the critical point of the CO 2 refrigerant, and a target evaporation temperature in an evaporator to which the CO 2 refrigerant cooled by the gas cooler is guided via an expansion valve is less than or equal to a second predetermined temperature.

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  • 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)
  • Devices That Are Associated With Refrigeration Equipment (AREA)
  • Air Conditioning Control Device (AREA)
EP22181615.0A 2021-07-02 2022-06-28 Freezing device, freezing system, and control method of freezing device Active EP4113035B1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2021110944A JP2023007844A (ja) 2021-07-02 2021-07-02 冷凍装置及び冷凍システム並びに冷凍装置の制御方法

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EP4113035A1 EP4113035A1 (en) 2023-01-04
EP4113035B1 true EP4113035B1 (en) 2023-09-27
EP4113035C0 EP4113035C0 (en) 2023-09-27

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Publication number Priority date Publication date Assignee Title
WO2003019085A1 (en) * 2001-08-31 2003-03-06 Mærsk Container Industri A/S A vapour-compression-cycle device
MX2007010004A (es) 2005-02-18 2008-04-08 Carrier Corp Metodo para controlar alta presion en un circuito de refrigeracion que opera intermitente y supercriticamente.

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EP4113035A1 (en) 2023-01-04
JP2023007844A (ja) 2023-01-19
EP4113035C0 (en) 2023-09-27

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