EP3617612B1 - Dispositif frigorifique binaire - Google Patents

Dispositif frigorifique binaire Download PDF

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Publication number
EP3617612B1
EP3617612B1 EP17907290.5A EP17907290A EP3617612B1 EP 3617612 B1 EP3617612 B1 EP 3617612B1 EP 17907290 A EP17907290 A EP 17907290A EP 3617612 B1 EP3617612 B1 EP 3617612B1
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EP
European Patent Office
Prior art keywords
stage
refrigerant
condenser
refrigeration cycle
expansion valve
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EP17907290.5A
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German (de)
English (en)
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EP3617612A1 (fr
EP3617612A4 (fr
Inventor
Yasuhiro Kito
Kenichi Hata
Yusuke Arii
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Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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Publication of EP3617612A4 publication Critical patent/EP3617612A4/fr
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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
    • F25B6/00—Compression machines, plants or systems, with several condenser circuits
    • F25B6/04—Compression machines, plants or systems, with several condenser circuits arranged in series
    • 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
    • F25B40/00—Subcoolers, desuperheaters or superheaters
    • F25B40/02—Subcoolers
    • 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
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/30—Expansion means; Dispositions thereof
    • F25B41/37—Capillary tubes
    • 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
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/16—Receivers

Definitions

  • the present invention relates to a cascade refrigeration system usable for freezing or refrigeration.
  • the cascade refrigeration system has a multistage configuration in which the lower-stage refrigeration cycle and the higher-stage refrigeration cycle are coupled to each other by a cascade condenser, which is configured to be able to exchange heat between a lower-stage condenser in the lower-stage refrigeration cycle and a higher-stage evaporator in the higher-stage refrigeration cycle.
  • cascade refrigeration system in which, during a defrosting operation, a primary side refrigeration cycle, that is, a higher-stage refrigeration cycle is operated when a compressor of a secondary side refrigeration cycle, that is, a lower-stage compressor of a lower-stage refrigeration cycle is stopped (see Patent Literature 1, for example).
  • a lower-stage condenser of the lower-stage refrigeration cycle is cooled by cooling a cascade heat exchanger by an evaporator of the higher-stage refrigeration cycle to control an increase in pressure in the lower-stage refrigeration cycle.
  • refrigerant in the lower-stage refrigeration cycle is cooled by a cascade condenser of the cascade heat exchanger, that is, a condenser of a lower-stage refrigerant circuit. Therefore, the refrigerant in the lower-stage refrigeration cycle does not flow in the lower-stage condenser when the lower-stage compressor is stopped.
  • the refrigerant is not adequately cooled and an increase in pressure due to an increase in temperature in the lower-stage refrigeration cycle is not controlled sufficiently.
  • the system needs high design pressures for on-site pipes, unit coolers, showcases, and other units, causing an increase in cost.
  • the refrigerant may be discharged from a safety valve. In such a case, the lower-stage refrigeration cycle needs to be replenished with refrigerant.
  • the present invention has been made to solve the above-mentioned problems, and therefore has an object to provide a cascade refrigeration system in which an increase in pressure due to an increase in temperature in a lower-stage refrigeration cycle is suppressed with a simple configuration.
  • a cascade refrigeration system including: a higher-stage refrigeration cycle in which a higher-stage compressor, a higher-stage condenser, a higher-stage expansion valve, and a higher-stage evaporator are sequentially connected by pipes and in which a higher-stage refrigerant is circulated; a lower-stage refrigeration cycle in which a lower-stage compressor, a first lower-stage condenser, a second lower-stage condenser, a lower-stage liquid receiver, a first lower-stage expansion valve, and a lower-stage evaporator are sequentially connected by pipes and in which a lower-stage refrigerant is circulated; and a cascade condenser including the higher-stage evaporator and the second lower-stage condenser to exchange heat between the higher-stage refrigerant flowing in the higher-stage evaporator and the lower-stage refriger
  • the natural circulation circuit having the vapor refrigerant pipe is provided.
  • the higher-stage refrigeration cycle is operated and lower-stage refrigerant is circulated by using the natural circulation circuit. Therefore, an increase in pressure of the refrigerant in the lower-stage refrigeration cycle can be controlled, and thus the design pressures for devices are not required to be set to high values. As a result, costs for on-site pipes, unit coolers, showcases, and other units in the system can be reduced.
  • a space for installing the refrigeration system is not limited.
  • FIG. 1 is a refrigerant circuit diagram of a cascade refrigeration system according to Embodiment 1 of the present invention.
  • a cascade refrigeration system 100 includes a higher-stage refrigeration cycle 101 and a lower-stage refrigeration cycle 102.
  • the higher-stage refrigeration cycle 101 and the lower-stage refrigeration cycle 102 are thermally coupled to each other by a cascade condenser 30.
  • Each of the elements constituting the higher-stage refrigeration cycle 101 and lower-stage refrigeration cycle 102 is housed in an outdoor unit 1 or a cooling unit 2, which is to be described later.
  • refrigerant to be enclosed in the lower-stage refrigeration cycle 102 in consideration of possible refrigerant leakage, carbon dioxide (CO 2 ) having a small effect on global warming is used.
  • CO 2 carbon dioxide
  • refrigerant to be enclosed in the higher-stage refrigeration cycle 101 R410A, R32, R404A, HFO-1234yf, propane, isobutene, CO 2 , ammonia, or other refrigerant is used, for example.
  • refrigerant to be enclosed in the lower-stage refrigeration cycle 102 is referred to as a lower-stage refrigerant
  • refrigerant to be enclosed in the higher-stage refrigeration cycle 101 is referred to as a higher-stage refrigerant.
  • the higher-stage refrigeration cycle 101 is a refrigeration cycle in which the higher-stage refrigerant is circulated.
  • a higher-stage compressor 10 a higher-stage condenser 11, a higher-stage expansion valve 12, and a higher-stage evaporator 13 are sequentially connected by a refrigerant pipe to form a refrigerant circuit.
  • a refrigerant circuit of the higher-stage refrigeration cycle 101 is referred to as a higher-stage refrigerant circuit.
  • the lower-stage refrigeration cycle 102 is a refrigeration cycle in which a lower-stage refrigerant is circulated.
  • a lower-stage compressor 20, a first lower-stage condenser 21, a second lower-stage condenser 22, a lower-stage liquid receiver 24, a first lower-stage expansion valve 25, and a lower-stage evaporator 26 are sequentially connected by a refrigerant pipe to form a refrigerant circuit.
  • the lower-stage refrigeration cycle 102 also has a second lower-stage expansion valve 23 that is provided between the second lower-stage condenser 22 and the lower-stage liquid receiver 24.
  • a refrigerant circuit of the lower-stage refrigeration cycle 102 is referred to as a lower-stage refrigerant circuit.
  • the cascade refrigeration system 100 includes the abovementioned cascade condenser 30.
  • the higher-stage evaporator 13 and the second lower-stage condenser 22 are configured to be coupled to each other so that heat can be exchanged between the refrigerant passing through the higher-stage evaporator 13 and the refrigerant passing through the second lower-stage condenser 22. That is, the cascade condenser 30 is an inter-refrigerant heat exchanger.
  • the cascade condenser 30 With the cascade condenser 30, the lower-stage refrigerant circuit and the higher-stage refrigerant circuit form a multistage structure.
  • the higher-stage compressor 10 is configured to suck the refrigerant passing through the higher-stage refrigerant circuit, compress the refrigerant sucked, and discharge the refrigerant in a gaseous state having a high temperature and a high pressure.
  • the higher-stage compressor 10 is formed of a compressor in which a rotation speed is controlled by an inverter circuit, for example, such that an amount of refrigerant to be discharged can be adjusted.
  • the higher-stage condenser 11 is configured to exchange heat between air or brine, for example, and the refrigerant flowing in the higher-stage refrigerant circuit to condense and liquefy the refrigerant.
  • the higher-stage condenser 11 exchanges heat between an outdoor air and the refrigerant.
  • the cascade refrigeration system 100 has a higher-stage condenser fan, which is not shown. With the higher-stage condenser fan, the outdoor air is sent to the higher-stage condenser 11 to facilitate the heat exchange in the higher-stage condenser 11.
  • the higher-stage condenser fan is formed of a fan capable of adjusting an air flow rate.
  • the higher-stage expansion valve 12 is configured to reduce the pressure of, and expand, the refrigerant flowing in the higher-stage refrigerant circuit, and is formed of a refrigerant flow control unit such as an electronic expansion valve or other device, or a refrigerant flow adjustment unit, for example. That is, the higher-stage expansion valve formed of a refrigerant flow control unit such as an electronic expansion valve or other device, or a refrigerant flow adjustment unit, for example. That is, the higher-stage expansion valve 12 is formed of a pressure reducing device or an expansion device capable of controlling an amount of expansion.
  • the higher-stage evaporator 13 is configured to evaporate and gasify the refrigerant flowing in the higher-stage refrigerant circuit by heat exchange.
  • the higher-stage evaporator 13 is formed of, for example, a heat transmission tube or other device, through which the refrigerant flowing in the higher-stage refrigerant circuit passes in the cascade condenser 30. In the cascade condenser 30, heat is exchanged between the refrigerant flowing in the higher-stage evaporator 13 and the refrigerant flowing in the lower-stage refrigerant circuit.
  • the lower-stage compressor 20 is configured to suck the refrigerant passing through the lower-stage refrigerant circuit, compress the refrigerant sucked, and discharge the refrigerant in a gaseous state having a high temperature and a high pressure.
  • the lower-stage compressor 20 is formed of a compressor in which a rotation speed is controlled by an inverter circuit, for example, such that an amount of refrigerant to be discharged can be adjusted.
  • the first lower-stage condenser 21 is configured to exchange heat between air or brine, for example, and the refrigerant flowing in the lower-stage refrigerant circuit to condense and liquefy the refrigerant.
  • the first lower-stage condenser 21 exchanges heat between an outdoor air and the refrigerant.
  • the cascade refrigeration system 100 has a lower-stage condenser fan, which is not shown. With the lower-stage condenser fan, the outdoor air is sent to the first lower-stage condenser 21 to facilitate the heat exchange in the first lower-stage condenser 21.
  • the lower-stage condenser fan is formed of a fan capable of adjusting an air flow rate.
  • the second lower-stage condenser 22 is configured to further condense the refrigerant that has been condensed and liquefied in the first lower-stage condenser 21 to obtain a subcooled refrigerant.
  • the second lower-stage condenser 22 is formed of, for example, a heat transmission tube or other device, through which the refrigerant flowing in the lower-stage refrigerant circuit passes in the cascade condenser 30. In the cascade condenser 30, heat is exchanged between the refrigerant flowing in the second lower-stage condenser 22 and the refrigerant flowing in the higher-stage refrigerant circuit.
  • the second lower-stage expansion valve 23 is configured to reduce the pressure of, and expand, the refrigerant flowing in the lower-stage refrigerant circuit, and is formed of a refrigerant flow control unit such as an electronic expansion valve or other device, or a refrigerant flow adjustment unit, for example. That is, the second lower-stage expansion valve 23 is formed of a pressure reducing device or an expansion device capable of controlling an amount of expansion.
  • the lower-stage liquid receiver 24 is provided downstream of the second lower-stage condenser 22 and the second lower-stage expansion valve 23.
  • the lower-stage liquid receiver 24 is configured to temporarily store refrigerant.
  • the first lower-stage expansion valve 25 is configured to reduce the pressure of, and expand, the refrigerant flowing in the lower-stage refrigerant circuit, and is formed of a refrigerant flow control unit such as an electronic expansion valve or other device, or a refrigerant flow adjustment unit, for example. That is, the first lower-stage expansion valve 25 is formed of a pressure reducing device or an expansion device capable of controlling an amount of expansion.
  • the lower-stage evaporator 26 is configured to evaporate and gasify the refrigerant flowing in the lower-stage refrigerant circuit by heat exchange.
  • the lower-stage refrigeration cycle 102 includes a natural circulation circuit 40.
  • the natural circulation circuit 40 has a subcooled refrigerant pipe 31 and a vapor refrigerant pipe 32.
  • the subcooled refrigerant pipe 31 connects a position between the second lower-stage condenser 22 and the second lower-stage expansion valve 23 and a position between the second lower-stage expansion valve 23 and the lower-stage liquid receiver 24.
  • the vapor refrigerant pipe 32 connects a position between the second lower-stage expansion valve 23 and the lower-stage liquid receiver 24 and a position between the first lower-stage condenser 21 and the second lower-stage condenser 22.
  • a capillary tube 33 is provided in a middle of the subcooled refrigerant pipe 31.
  • the capillary tube 33 is a pressure adjustment unit of the present invention.
  • a check valve 34 is provided in a middle of the vapor refrigerant pipe 32.
  • the cooling unit 2 is used as a refrigerating/freezing showcase or a unit cooler, for example.
  • the higher-stage compressor 10 the higher-stage condenser 11, the higher-stage expansion valve 12, the higher-stage evaporator 13, the lower-stage compressor 20, the first lower-stage condenser 21, the second lower-stage condenser 22, the second lower-stage expansion valve 23, the lower-stage liquid receiver 24, the subcooled refrigerant pipe 31, the vapor refrigerant pipe 32, the capillary tube 33, and the check valve 34 are housed in the outdoor unit 1.
  • the first lower-stage expansion valve 25 and the lower-stage evaporator 26 are housed in the cooling unit 2.
  • the outdoor unit 1 and the cooling unit 2 are connected to each other by two pipes, that is, a liquid pipe 3 and a gas pipe 4.
  • Fig. 2 is an equipment layout of the natural circulation circuit according to Embodiment 1 of the present invention.
  • the second lower-stage condenser 22 of the cascade condenser 30 is disposed at an upper part of the outdoor unit 1
  • the lower-stage liquid receiver 24 is disposed at a lower part of the outdoor unit 1
  • the second lower-stage expansion valve 23 is arranged at an intermediate part of the outdoor unit 1, and as described above, the second lower-stage condenser 22, the lower-stage liquid receiver 24, and the second lower-stage expansion valve 23 are sequentially connected by pipes. That is, in the top-bottom direction of the outdoor unit 1, the second lower-stage condenser 22 is positioned higher than the lower-stage liquid receiver 24 is.
  • the subcooled refrigerant pipe 31 and the vapor refrigerant pipe 32 are connected as described above to obtain a difference in height in the circuit. As illustrated in Fig. 2 , in the top-bottom direction of the outdoor unit 1, the vapor refrigerant pipe 32 is disposed higher than the subcooled refrigerant pipe 31.
  • the check valve 34 of the vapor refrigerant pipe 32 is configured to prevent the refrigerant that is discharged from the lower-stage compressor 20 illustrated in Fig. 1 and then flows out from the first lower-stage condenser 21, from entering the vapor refrigerant pipe 32.
  • the higher-stage compressor 10 sucks the higher-stage refrigerant, compresses it into a high-temperature and high-pressure gaseous state and discharges it.
  • the discharged higher-stage refrigerant flows into the higher-stage condenser 11.
  • the higher-stage condenser 11 exchanges heat between the outdoor air, which is supplied by the higher-stage condenser fan (not shown), and the higher-stage refrigerant in a gaseous state to condense and liquefy the higher-stage refrigerant.
  • the condensed and liquefied higher-stage refrigerant passes through the higher-stage expansion valve 12.
  • the higher-stage expansion valve 12 reduces the pressure of the condensed and liquefied higher-stage refrigerant.
  • the higher-stage refrigerant that has been reduced in pressure flows into the higher-stage evaporator 13 in the cascade condenser 30.
  • heat is exchanged between the higher-stage refrigerant and the lower-stage refrigerant passing through the second lower-stage condenser 22 to evaporate and gasify the higher-stage refrigerant.
  • the evaporated and gasified higher-stage refrigerant is sucked into the higher-stage compressor 10.
  • the lower-stage compressor 20 sucks and compresses the lower-stage refrigerant to discharge the lower-stage refrigerant in a high-temperature and high-pressure gaseous state.
  • the discharged lower-stage refrigerant flows into the first lower-stage condenser 21.
  • the first lower-stage condenser 21 exchanges heat between the outdoor air, which is supplied by the lower-stage condenser fan (not shown), and the lower-stage refrigerant to condense the lower-stage refrigerant.
  • the condensed lower-stage refrigerant flows into the second lower-stage condenser 22 in the cascade condenser 30.
  • the second lower-stage condenser 22 exchanges heat between the lower-stage refrigerant and the higher-stage refrigerant passing through the higher-stage evaporator 13 to further condense the lower-stage refrigerant to obtain the lower-stage refrigerant in a subcooled and liquefied state.
  • the subcooled and liquefied lower-stage refrigerant passes through the second lower-stage expansion valve 23.
  • the second lower-stage expansion valve 23 reduces the pressure of the subcooled and liquefied lower-stage refrigerant to obtain the refrigerant having an intermediate pressure.
  • the lower-stage refrigerant that has been reduced in pressure to the intermediate pressure then passes through the lower-stage liquid receiver 24, and becomes the lower-stage refrigerant having a low pressure after being reduced in pressure at the first lower-stage expansion valve 25.
  • the lower-stage refrigerant that has been reduced in pressure to the low pressure flows into the lower-stage evaporator 26.
  • the lower-stage evaporator 26 exchanges heat between an indoor air of the refrigerated warehouse and the lower-stage refrigerant to evaporate and gasify the lower-stage refrigerant.
  • the evaporated and gasified lower-stage refrigerant is sucked into the lower-stage compressor 20.
  • the stoppage of the lower-stage refrigeration cycle 102 described here indicates mainly a case in which the lower-stage compressor 20 is in a stop state.
  • the higher-stage refrigerant circuit of the higher-stage refrigeration cycle 101 is operated with another power supply. Therefore, the lower-stage refrigerant can be cooled by the higher-stage evaporator 13 of the cascade condenser 30, and an increase in pressure of the lower-stage refrigerant due to an increase in temperature can be reduced.
  • the lower-stage refrigerant is not circulated, operation of the higher-stage refrigeration cycle 101 alone cannot sufficiently cool down the lower-stage refrigerant, and hence an increase in pressure in the lower-stage refrigerant circuit is not controlled adequately.
  • the abovementioned natural circulation circuit 40 is provided in the lower-stage refrigeration cycle 102 to circulate the lower-stage refrigerant.
  • the subcooled refrigerant In the natural circulation circuit 40, the subcooled refrigerant, the heat of which has been exchanged in the cascade condenser 30, passes through the second lower-stage expansion valve 23 and the pipe, at which the second lower-stage expansion valve 23 is provided, or passes through the subcooled refrigerant pipe 31, and then drips into the lower-stage liquid receiver 24.
  • the subcooled refrigerant does not enter the vapor refrigerant pipe 32, to which the second lower-stage condenser 22 is connected above.
  • the volume of the subcooled refrigerant remaining above the second lower-stage condenser 22 is reduced, and thus a part higher than the second lower-stage condenser 22 has a negative pressure and a part at or around the lower-stage liquid receiver 24 has a positive pressure.
  • the vapor refrigerant stored in the lower-stage liquid receiver 24 is sucked to the higher side, where the second lower-stage condenser 22 is located, via a pipe connecting the second lower-stage expansion valve 23 and the lower-stage liquid receiver 24, and the vapor refrigerant pipe 32 that branches off from the pipe.
  • the vapor refrigerant that has been sucked to the higher side flows into the second lower-stage condenser 22, and then the heat of the vapor refrigeration is exchanged again in the second lower-stage condenser 22 to obtain a subcooled refrigerant, and the subcooled refrigerant drips into the lower-stage liquid receiver 24.
  • Such natural circulation of the refrigerant flowing in the natural circulation circuit 40 is repeated, and thus an increase in pressure in the lower-stage refrigerant circuit is controlled efficiently.
  • the subcooled refrigerant pipe 31 is provided to make the subcooled refrigerant circulate even at the time of power failure or malfunction, such as a case where the second lower-stage expansion valve 23, which is an electronic expansion valve, is closed.
  • the capillary tube 33 installed in a middle of the subcooled refrigerant pipe 31 is provided to reduce the pressure of the lower-stage refrigerant, similarly to the second lower-stage expansion valve 23, even when the subcooled refrigerant flowing out from the second lower-stage condenser 22 of the cascade condenser 30 in a normal cooling operation is bypassed to the subcooled refrigerant pipe 31.
  • Fig. 3 is an equipment layout of the natural circulation circuit according to Embodiment 1 of the present invention.
  • the capillary tube 33 which is provided in a middle of the subcooled refrigerant pipe 31, may be replaced with a solenoid valve 35, as illustrated in Fig. 3 .
  • the solenoid valve 35 is a pressure adjustment unit of the present invention.
  • the solenoid valve 35 is set to "close” in a normal cooling operation and to "open” at the time of power failure.
  • the subcooled refrigerant flowing out from the second lower-stage condenser 22 of the cascade condenser 30 does not enter the lower-stage liquid receiver 24 via the subcooled refrigerant pipe 31.
  • the second lower-stage expansion valve 23 is closed at the time of power failure or malfunction, the lower-stage refrigerant is bypassed to the subcooled refrigerant pipe 31, and flows into the lower-stage liquid receiver 24.
  • capillary tube 33 or the solenoid valve 35 is not required depending on pressure losses of the second lower-stage expansion valve 23 and the pipe on which the second lower-stage expansion valve 23 is installed.
  • the higher-stage refrigeration cycle 101 is operated with another power supply, and the lower-stage refrigerant in the lower-stage refrigerant circuit is cooled by the second lower-stage condenser 22 of the cascade condenser 30.
  • the natural circulation circuit 40 is provided in the lower-stage refrigeration cycle 102 to circulate the lower-stage refrigerant by itself, and hence the increase in pressure due to the increase in temperature can be controlled efficiently. As a result, high design pressures are not required for on-site pipes, unit coolers, showcases and other units in the system, and thus the cost of equipment can be reduced.
  • Fig. 4 is an equipment layout of a natural circulation circuit according to Embodiment 2 of the present invention.
  • Fig. 4 illustrates an equipment layout of a natural circulation circuit 40a of a cascade refrigeration system 100a according to Embodiment 2. Configuration and operation of the natural circulation circuit 40a are described based on Fig. 4 . Note that, in Fig. 4 , components similar to those in Embodiment 1 are denoted by the same reference symbols. In Embodiment 2, differences from Embodiment 1 described above are mainly described, and description of the same functions and configurations as Embodiment 1, such as configurations of refrigerant circuits, is omitted.
  • the natural circulation circuit 40a of the cascade refrigeration system 100a includes a subcooled refrigerant pipe 31 and a vapor refrigerant pipe 32a.
  • the subcooled refrigerant pipe 31 connects a position between the second lower-stage condenser 22 and the second lower-stage expansion valve 23 and a position between the second lower-stage expansion valve 23 and the lower-stage liquid receiver 24.
  • the vapor refrigerant pipe 32a connects a position between the second lower-stage condenser 22 and the second lower-stage first condenser 21 and the lower-stage liquid receiver 24. That is, the vapor refrigerant pipe 32a is directly connected to the lower-stage liquid receiver 24.
  • Embodiment 2 in the natural circulation circuit 40a with such configuration, the connecting location of the vapor refrigerant pipe 32a is provided at the lower-stage liquid receiver 24. Thus, the subcooled refrigerant dripping into the lower-

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Claims (5)

  1. Système de réfrigération en cascade (100), comprenant :
    un cycle de réfrigération d'étage supérieur (101) dans lequel un compresseur d'étage supérieur (10), un condenseur d'étage supérieur (11), un détendeur d'étage supérieur (12) et un évaporateur d'étage supérieur (13) sont connectés séquentiellement par des tuyaux et dans lequel un réfrigérant d'étage supérieur est mis en circulation ;
    un cycle de réfrigération d'étage inférieur (102) dans lequel un compresseur d'étage inférieur (20), un premier condenseur d'étage inférieur (21), un second condenseur d'étage inférieur (22), un récepteur de liquide d'étage inférieur (24), un premier détendeur d'étage inférieur (25) et un évaporateur d'étage inférieur (26) sont connectés séquentiellement par des tuyaux et dans lequel un réfrigérant d'étage inférieur est mis en circulation ; et
    un condenseur en cascade (30) comprenant l'évaporateur d'étage supérieur (13) et le second condenseur d'étage inférieur (22) pour échanger de la chaleur entre le réfrigérant d'étage supérieur s'écoulant dans l'évaporateur d'étage supérieur (13) et le réfrigérant d'étage inférieur s'écoulant dans le second condenseur d'étage inférieur (22), dans lequel
    le cycle de réfrigération d'étage inférieur (102) est pourvu d'un circuit de circulation naturel (40) présentant un tuyau de réfrigérant de vapeur (32) qui connecte le récepteur de liquide d'étage inférieur (24) et une position entre le premier condenseur d'étage inférieur (21) et le second condenseur d'étage inférieur (22) et qui a un clapet anti-retour (34) dans une position au milieu du tuyau de réfrigérant de vapeur (32), et un second détendeur d'étage inférieur (23) étant prévu entre le second condenseur d'étage inférieur (22) et le récepteur de liquide d'étage inférieur (24), et dans lequel
    le circuit de circulation naturel (40) présente un tuyau de réfrigérant sous-refroidi (31) qui connecte une position entre le second condenseur d'étage inférieur (22) et le second détendeur d'étage inférieur (23) et une position entre le second détendeur d'étage inférieur (23) et le récepteur de liquide d'étage inférieur (24) et qui présente une unité d'ajustement de pression (33) dans une position au milieu du tuyau de réfrigérant sous-refroidi (31), et
    le tuyau de réfrigérant de vapeur (32) est connecté une position entre le second détendeur d'étage inférieur (23) et le récepteur de liquide d'étage inférieur (24).
  2. Système de réfrigération en cascade (100) selon la revendication 1, dans lequel l'unité d'ajustement de pression (33) est un tube capillaire (33).
  3. Système de réfrigération en cascade (100) selon la revendication 1, dans lequel l'unité d'ajustement de pression (33) est une électrovanne (35).
  4. Système de réfrigération en cascade (100) selon l'une quelconque des revendications 1 à 3, dans lequel le second condenseur d'étage inférieur (22) est disposé plus haut que le récepteur de liquide d'étage inférieur (24) dans le circuit de circulation naturel (40).
  5. Système de réfrigération en cascade (100) selon l'une quelconque des revendications 1 à 4, dans lequel le tuyau de réfrigérant de vapeur (32) est disposé plus haut que le tuyau de réfrigérant sous-refroidi (31) dans le circuit de circulation naturel (40).
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CN109631375A (zh) * 2018-12-12 2019-04-16 厦门铸力节能科技有限公司 一种复合型制冷机组可回收蒸汽的热回收系统
CN111735224A (zh) * 2020-01-21 2020-10-02 天津冷源工程设计院 一种适用于多种负荷工况的制冷系统
EP4328522A4 (fr) * 2021-04-21 2024-05-29 Mitsubishi Electric Corporation Dispositif à cycle frigorifique de type binaire
CN117716185A (zh) * 2021-08-05 2024-03-15 三菱电机株式会社 制冷循环装置和制冷循环装置的控制方法
WO2023012961A1 (fr) * 2021-08-05 2023-02-09 三菱電機株式会社 Dispositif de circuit de réfrigération et procédé de commande pour dispositif de circuit de réfrigération
CN118103644A (zh) * 2021-10-22 2024-05-28 三菱电机株式会社 二元制冷装置

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JP2004190917A (ja) 2002-12-10 2004-07-08 Sanyo Electric Co Ltd 冷凍装置
WO2011077720A1 (fr) * 2009-12-22 2011-06-30 ダイキン工業株式会社 Dispositif de refrigeration
JP5800994B2 (ja) * 2012-09-21 2015-10-28 三菱電機株式会社 冷凍装置及びその制御方法
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