WO2022249565A1 - Multi-stage compression refrigeration apparatus - Google Patents

Multi-stage compression refrigeration apparatus Download PDF

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Publication number
WO2022249565A1
WO2022249565A1 PCT/JP2022/004822 JP2022004822W WO2022249565A1 WO 2022249565 A1 WO2022249565 A1 WO 2022249565A1 JP 2022004822 W JP2022004822 W JP 2022004822W WO 2022249565 A1 WO2022249565 A1 WO 2022249565A1
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Prior art keywords
pressure
refrigerant
gas
heat exchanger
liquid
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PCT/JP2022/004822
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French (fr)
Japanese (ja)
Inventor
直樹 黒田
篤 塩谷
実希 山田
寿幸 石田
有二 岡田
有悟 笹谷
航平 松本
崚平 在本
真悟 佐藤
Original Assignee
三菱重工サーマルシステムズ株式会社
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Priority to EP22810849.4A priority Critical patent/EP4350255A1/en
Publication of WO2022249565A1 publication Critical patent/WO2022249565A1/en

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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00Compression machines, plants or systems with non-reversible cycle
    • F25B1/10Compression machines, plants or systems with non-reversible cycle with multi-stage compression
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00Fluid-circulation arrangements
    • F25B41/30Expansion means; Dispositions thereof
    • F25B41/39Dispositions with two or more expansion means arranged in series, i.e. multi-stage expansion, on a refrigerant line leading to the same evaporator
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00General 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
    • F25B2400/07Details of compressors or related parts
    • F25B2400/072Intercoolers therefor
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00General 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
    • F25B2400/23Separators
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2500/00Problems to be solved
    • F25B2500/31Low ambient temperatures
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00Control issues
    • F25B2600/25Control of valves
    • F25B2600/2509Economiser valves
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21Temperatures
    • F25B2700/2106Temperatures of fresh outdoor air
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00Arrangement or mounting of control or safety devices
    • F25B49/02Arrangement or mounting of control or safety devices for compression type machines, plants or systems

Definitions

  • the present disclosure relates to a refrigeration system that compresses refrigerant in multiple stages.
  • Patent Document 1 discloses a refrigeration system with a two-stage compression mechanism.
  • Such a refrigeration system includes an electric compressor having a low-stage compression mechanism and a high-stage compression mechanism in a closed housing, a radiator, a high-pressure expansion valve, a gas-liquid separator, a low-pressure expansion valve, an evaporator, It is equipped with gas injection piping. Gas refrigerant introduced into the housing of the electric compressor from the gas-liquid separator through the gas injection pipe is sucked into the high-stage compression mechanism together with refrigerant discharged into the housing from the low-stage compression mechanism.
  • a refrigerant with a low GWP is adopted for the purpose of reducing the global warming potential (GWP) and improving the energy consumption efficiency (COP; Coefficient of Performance). Development and commercialization are underway.
  • GWP global warming potential
  • COP Energy consumption efficiency
  • Development and commercialization are underway.
  • a refrigerant containing CO2 is used as the refrigerant, in order to keep the high refrigerant discharge temperature within the permissible limit due to high-pressure operation, the high pressure set for the radiator and the low pressure set for the evaporator must be maintained. It is effective to introduce intermediate-pressure refrigerant from the gas-liquid separator between the low-stage compression mechanism and the high-stage compression mechanism (intermediate-pressure injection).
  • a refrigerating device that employs a refrigerant with a low GWP
  • the liquid level of each of the plurality of gas-liquid separators is not fixed when the number of stages is increased to 3 or more.
  • the liquid refrigerant is stored in the gas-liquid separator, and the refrigerant is supercooled by the supercooling heat exchanger.
  • an object of the present disclosure is to provide a refrigeration system that can stably operate while improving the efficiency of the refrigeration cycle.
  • the present disclosure is a refrigerating device that circulates a refrigerant by a refrigerating cycle, and includes a compression section that includes three or more stages of compression mechanisms that are connected in series and each compresses the refrigerant, and the refrigerant discharged from the compression section is discharged to the outside air.
  • a first heat exchanger that dissipates heat, a high-pressure pressure reducing mechanism on the relatively high pressure side, and a low pressure pressure reducing mechanism on the relatively low pressure side.
  • a high-pressure decompression unit that is reduced by a mechanism, a second heat exchanger that causes the refrigerant that has passed through the decompression unit to absorb heat from a heat load, and a high pressure that is provided between the high-pressure decompression mechanism and the low-pressure decompression mechanism and set in the first heat exchanger and a plurality of intermediate pressure injection passages for supplying intermediate pressure refrigerant between the compression mechanism and the low pressure set in the second heat exchanger, and among the plurality of intermediate pressure injection passages
  • a gas-liquid separator that supplies gas-phase refrigerant to the high-pressure intermediate pressure injection passage on the relatively high-pressure side, a liquid refrigerant that is a liquid-phase refrigerant supplied from the gas-liquid separator, and a part of the liquid refrigerant an internal heat exchanger that supplies the refrigerant absorbed heat from the liquid refrigerant by exchanging heat with the pressure-reduced two-phase refrigerant to the intermediate-pressure injection passage on the low-pressure side with
  • intermediate pressure injection corresponding to the number of compression stages N (3 or more) and the gas-liquid separator is arranged on the high-pressure side of the internal heat exchanger.
  • the number of gas-liquid separators is smaller than when a gas-liquid separator is arranged at each stage of the intermediate pressure injection, so it is possible to suppress the decrease in efficiency and the instability of the operating state due to the uneven distribution of the liquid refrigerant. can.
  • the gas-liquid separator is arranged on the high-pressure side of the internal heat exchanger, saturated liquid can flow from the gas-liquid separator into the internal heat exchanger to supercool the refrigerant. Stable and efficient operation is possible by supercooling, and there is no need to install a supercooling heat exchanger for inflowing the refrigerant that has passed through the internal heat exchanger, which contributes to cost reduction, miniaturization and weight reduction of the device. can do.
  • FIG. 1 is a diagram showing a circuit configuration of a refrigeration system according to an embodiment of the present disclosure
  • FIG. 2 is a Moliere diagram of the refrigeration system shown in FIG. 1.
  • FIG. It is a Moliere diagram of a refrigeration system according to a comparative example.
  • FIG. 10 is a diagram showing a circuit configuration of a refrigeration system according to a modified example of the present disclosure
  • 5 is a Moliere diagram of the refrigeration system shown in FIG. 4;
  • the multi-stage compression refrigerating apparatus 1 shown in FIG. 1 circulates a refrigerant in a refrigerating cycle to cool an appropriate heat load (for example, the air in the apparatus housing and stored items) using outside air as a heat source.
  • the refrigerating apparatus 1 includes, as basic elements forming a refrigerating cycle, a compression section 10 for compressing the refrigerant, a radiator E1 (first heat exchanger) for releasing heat from the refrigerant to the outside air, and a decompression section 20 for reducing the pressure of the refrigerant.
  • the refrigerant compressed by compression section 10 flows through radiator E ⁇ b>1 , decompression section 20 , and heat absorber E ⁇ b>2 in this order, and is sucked into compression section 10 .
  • the refrigerant circuit of the refrigeration apparatus 1 of the present embodiment is arbitrarily selected from, for example, HFC (Hydro Fluoro Carbon) refrigerant, HFO (Hydro Fluoro Olefin) refrigerant, carbon dioxide (CO 2 ) refrigerant, hydrocarbon refrigerant, and the like.
  • HFC Hydrofluoro Fluoro Carbon
  • HFO Hydrofluoro Fluoro Olefin
  • CO 2 carbon dioxide
  • hydrocarbon refrigerant hydrocarbon refrigerant
  • this embodiment employs a refrigerant containing at least a portion of carbon dioxide (CO 2 ).
  • the compression section 10 includes multiple stages of compression mechanisms 11 to 14 connected in series.
  • the first-stage compression mechanism 11, the second-stage compression mechanism 12, the third-stage compression mechanism 13, and the fourth-stage compression mechanism 14 sequentially compress the refrigerant from the low-pressure side L to the high-pressure side H over a plurality of steps.
  • the number of stages N of the compression unit 10 is 3 or more, and as an example, the number of stages N is "4".
  • the first to fourth stages are indicated by the symbols n1, n2, n3 and n4.
  • FIG. 2 is a Moliere diagram showing the relationship between the pressure of the refrigerant in the refrigeration system 1 and the specific enthalpy.
  • the symbols r1, r2, etc. shown in FIG. 2 correspond to the same symbols shown in FIG.
  • the refrigeration system 1 is operated in a four-stage compression, two-stage expansion refrigeration cycle.
  • the refrigeration system 1 of this embodiment includes two electric compressors 101 and 102, a control device 15 capable of controlling the operation of the electric motors and expansion valves of the electric compressors 101 and 102, and the electric compressors 101 and 102. and an intermediate cooling heat exchanger 16 provided between.
  • the first electric compressor 101 rotates the first stage compression mechanism 11 and the second stage compression mechanism 12 that are connected in series, a housing 101A that houses the compression mechanisms 11 and 12, and the compression mechanisms 11 and 12. and an electric motor 101B.
  • the second electric compressor 102 rotates the third stage compression mechanism 13 and the fourth stage compression mechanism 14 that are connected in series, a housing 102A that houses the compression mechanisms 13 and 14, and the compression mechanisms 13 and 14. and an electric motor 102B.
  • the intermediate cooling heat exchanger 16 cools the refrigerant discharged from the second-stage compression mechanism 12 by radiating heat to the outside air, and supplies the refrigerant to the suction portion of the third-stage compression mechanism 13 (operating points r4 to r5 in FIG. 2). What).
  • the first stage compression mechanism 11 corresponds to, for example, a rotary compression mechanism including a piston rotor and a cylinder.
  • the third stage compression mechanism 13 is also the same.
  • the second stage compression mechanism 12 corresponds to, for example, a scroll compression mechanism including a pair of scroll members. The same applies to the fourth stage compression mechanism 14 .
  • the decompression unit 20 includes a low pressure decompression mechanism 21 on the relatively low pressure side L and a high pressure decompression mechanism 22 on the relatively high pressure side H. As shown in FIG.
  • Each of the decompression mechanisms 21 and 22 may be an expansion valve, a capillary tube, or the like. In particular, it is preferable that the expansion valve is capable of adjusting the degree of opening of the throttle.
  • the high-pressure pressure reducing mechanism 22 and the low-pressure pressure reducing mechanism 21 sequentially reduce the pressure of the refrigerant that has passed through the radiator E1 in this order.
  • the pressure of the refrigerant increases stepwise as the refrigerant is compressed by the multi-stage compression mechanisms 11-14 of n1, n2, n3, and n4. Along with this, the discharge temperature of the refrigerant rises. Lowering the temperature of the refrigerant (from r4 to r5) by the action of the intermediate cooling heat exchanger 16 that releases heat from the refrigerant to the outside air can contribute to suppressing the discharge temperature of the compression section 10 as a whole.
  • the pressure between the suction pressure to the first stage n1 of compression and the discharge pressure from the second stage n2 is called the first intermediate pressure P1 .
  • the pressure between the suction pressure to the second stage n2 and the discharge pressure from the third stage n3 is called a second intermediate pressure P2
  • the pressure from the suction pressure to the third stage n3 and the pressure from the fourth stage n4 is The pressure between it and the discharge pressure is called a third intermediate pressure P3 .
  • a relationship of P 1 ⁇ P 2 ⁇ P 3 holds.
  • the critical temperature of CO2 is lower than that of other refrigerants such as HFCs (Hydro Fluoro Carbon).
  • the CO2 refrigerant is compressed to a pressure exceeding the critical pressure PC by the compression section 10 that compresses the refrigerant in multiple stages.
  • the pressure (r12, r13, r14) of the refrigerant that has passed through the radiator E1 and the high-pressure pressure reducing mechanism 22, that is, the third intermediate pressure P3 remains below the critical pressure PC .
  • the refrigeration system 1 supplies intermediate-pressure refrigerant obtained by gas-liquid separation of the refrigerant between the low-pressure pressure reducing mechanism 21 and the high-pressure pressure reducing mechanism 22 between the first to fourth stage compression mechanisms 11 to 14, respectively.
  • Intermediate pressure injection is performed. Therefore, the refrigerating apparatus 1 corresponds to N-1 intermediate pressure injection means (31 to 33) provided between the low pressure pressure reducing mechanism 21 and the high pressure pressure reducing mechanism 22 and the intermediate pressure injection means (31 to 33), respectively. It has N ⁇ 1 intermediate pressure injection flow paths 41 to 43 .
  • Refrigerant at intermediate pressures P 1 , P 2 , and P 3 is supplied between the serially connected compression mechanisms 11 to 14 through the intermediate pressure injection passages 41 to 43, respectively, thereby performing second to fourth stage compression.
  • the discharge temperature of each of the mechanisms 12-14 can be reduced.
  • a valve can be provided in each of the intermediate pressure injection flow paths 41 to 43 as required. The valve may be switched open or closed depending on operating conditions.
  • the intermediate pressure injection means (31-33) consist of a single gas-liquid separator 33 (liquid receiver) and internal heat exchangers 32, 31, as shown in FIG.
  • the gas-liquid separator 33 is arranged on the high pressure side H with respect to the internal heat exchangers 32 and 31 .
  • the high pressure internal heat exchanger 32 is arranged on the high pressure side H with respect to the low pressure internal heat exchanger 31 .
  • These gas-liquid separator 33, internal heat exchanger 32, and internal heat exchanger 31 pass the intermediate-pressure refrigerant through corresponding intermediate-pressure injection passages 41-43 to the second to fourth-stage compression mechanisms 12-4, respectively. 14.
  • the refrigerant discharged from the fourth stage compression mechanism 14 is decompressed by the high pressure decompression mechanism 22 and flows into the gas-liquid separator 33 .
  • the refrigerant that has flowed into the gas-liquid separator 33 is separated into a gas phase and a liquid phase based on the density difference inside the storage tank 33A. This corresponds to the state change from r12 to r13 and r14 as shown in FIG.
  • a third intermediate pressure injection channel 43 is connected to the gas phase region 33B above the liquid surface in the storage tank 33A.
  • the gas-phase refrigerant at the third intermediate pressure P3 separated from the liquid phase in the gas-liquid separator 33 is supplied to the intermediate-pressure injection on the high-pressure side H through the third intermediate-pressure injection passage 43 (from r13 to r8 ).
  • the temperature of the refrigerant at the third intermediate pressure P3 supplied to the fourth stage compression mechanism 14 through the third intermediate pressure injection passage 43 is lower than the temperature of the refrigerant discharged from the third stage compression mechanism 13 . Therefore, the temperature of the refrigerant to be sucked into the fourth stage compression mechanism 14 is lowered (r7 to r8). As a result, the temperature of the refrigerant discharged from the fourth stage compression mechanism 14 also drops, so the intermediate pressure gas injection contributes to the reduction of the discharge temperature.
  • the liquid-phase refrigerant (liquid refrigerant) stored in the storage tank 33A is supplied to the high-pressure internal heat exchanger 32 and the low-pressure internal heat exchanger 31, and the high-pressure internal heat exchanger 32 and the low-pressure internal heat exchanger 31 While subcooling is provided by each, a part thereof passes through the second intermediate pressure injection passage 42 and the first intermediate pressure injection passage 41, respectively, to the third intermediate pressure injection. It is subjected to intermediate pressure injection. The flow rate of the refrigerant gradually decreases as the injection of the intermediate pressures P 1 , P 2 and P 3 is performed.
  • the capacity of the high-pressure internal heat exchanger 32 upstream of the refrigerant flow from the high-pressure pressure reducing mechanism 22 to the low-pressure pressure reducing mechanism 21 is greater than the capacity of the low-pressure internal heat exchanger 31 downstream.
  • the capacity of the high-pressure internal heat exchanger 32 is, for example, about 2.5 times as large as the capacity of the low-pressure internal heat exchanger 31 .
  • Both the high-pressure internal heat exchanger 32 and the low-pressure internal heat exchanger 31 depressurize the liquid refrigerant supplied from the gas-liquid separator 33 and part of the liquid refrigerant supplied from the gas-liquid separator 33 through the decompression mechanism (321, 311) to exchange heat with a two-phase refrigerant that is depressurized.
  • the high-pressure internal heat exchanger 32 includes a main flow path 320 into which the liquid refrigerant supplied from inside the gas-liquid separator 33 in a saturated state flows, a decompression mechanism 321, and the liquid refrigerant supplied from the gas-liquid separator 33.
  • a two-phase refrigerant that has undergone a branch flow path 322 that partially flows into the decompression mechanism 321 and the decompression from the third intermediate pressure P3 to the second intermediate pressure P2 by the decompression mechanism 321 (from r14 to r15 in FIG. 2) and a heat absorption channel 323 into which the heat is introduced.
  • the refrigerant flowing through the heat absorption passage 323 is gasified (from r15 to r16) by absorbing heat from the refrigerant flowing through the main passage 320 , and is sucked into the third stage compression mechanism 13 through the second intermediate pressure injection passage 42 .
  • the refrigerant flowing through the main flow path 320 is subcooled (from r14 to r17) by dissipating heat to the refrigerant flowing through the heat absorption flow path 323, and flows into the low-pressure internal heat exchanger 31.
  • the second intermediate pressure injection flow path 42 supplies the refrigerant at the second intermediate pressure P2 to the suction portion of the third stage compression mechanism 13 (from r16 to r6), it flows out of the intermediate cooling heat exchanger 16 and flows into the third stage.
  • the temperature of the refrigerant sucked into the three-stage compression mechanism 13 decreases (from r5 to r6).
  • the third-stage compression mechanism is also affected by the action of the intermediate cooling heat exchanger 16 (from r4 to r5). Since the intake temperature to 13 is lowered, the discharge temperature can be further suppressed.
  • the low-pressure internal heat exchanger 31 includes a main flow path 310 into which the supercooled liquid refrigerant (supercooled liquid) flowing out from the high-pressure internal heat exchanger 32 flows, a pressure reducing mechanism 311, and a pressure reducing mechanism for part of the supercooled liquid. 311, and an endothermic flow path 313 into which the two-phase refrigerant that has undergone decompression (from r17 to r18) from the second intermediate pressure P2 to the first intermediate pressure P1 by the decompression mechanism 311 flows.
  • the refrigerant flowing through the heat absorption passage 313 absorbs heat from the refrigerant flowing through the main passage 310 to be gasified (from r18 to r19), and is sucked into the second stage compression mechanism 12 through the first intermediate pressure injection passage 41 ( r19 to r3). As a result, the temperature of the refrigerant sucked into the second stage compression mechanism 12 is lowered (from r2 to r3).
  • the refrigerant flowing through the main flow path 310 increases the degree of subcooling (from r17 to r20) by dissipating heat to the refrigerant flowing through the heat absorption flow path 313, and flows into the low-pressure pressure reducing mechanism 21. Since the liquid refrigerant at the first intermediate pressure P1 flowing out from the low-pressure internal heat exchanger 31 is sufficiently supercooled, it directly flows to the low-pressure pressure reducing mechanism 21 without passing through the heat exchanger for supercooling. It flows in and is decompressed by the low pressure decompression mechanism 21 (from r20 to r21). After passing through the low-pressure pressure reducing mechanism 21, the refrigerant absorbs heat from the heat load by the heat absorber E2, evaporates, and is sucked into the first stage compression mechanism 11 (from r21 to r22).
  • Liquid refrigerant flowing from the gas-liquid separator 33 to the internal heat exchanger 32, liquid refrigerant flowing from the high-pressure internal heat exchanger 32 to the low-pressure internal heat exchanger 31, and low-pressure pressure reducing mechanism 21 from the low-pressure internal heat exchanger 31 correspond to the third intermediate pressure P3 (r14, r17 and r20). Therefore, the expansion process in the refrigeration cycle is aggregated into two stages: decompression from the high pressure PH to the third intermediate pressure P3 by the high pressure decompression mechanism 22, and decompression from the third intermediate pressure P3 to the low pressure PL . . That is, the refrigeration system 1 is operated in a state where the number of stages of expansion is smaller than the number of stages N of compression, that is, in a four-stage compression and two-stage expansion cycle.
  • a decompression mechanism, a gas-liquid separator, a decompression mechanism, a gas-liquid separator, a decompression mechanism, a gas-liquid separator, and a decompression mechanism are arranged from the high pressure side H to the low pressure side L.
  • intermediate-pressure gas-phase refrigerant is supplied from each gas-liquid separator to the suction portion of the compression mechanism through the intermediate-pressure injection passage.
  • Such a comparative refrigeration system operates in a cycle of N-stage compression and N-stage expansion, as indicated by the solid line in FIG. N is, for example, "4".
  • the refrigerating apparatus of the comparative example may include a subcooling heat exchanger that exchanges heat between the liquid refrigerant flowing out of the gas-liquid separator on the lowest pressure side L and the outside air. In that case, the refrigerant is supercooled, as indicated by the dashed-dotted arrows in FIG.
  • the refrigeration system of the comparative example has N-1 gas-liquid separators, so if the number of stages N is 3 or more, it has 2 or more gas-liquid separators. In that case, it is difficult to secure liquid refrigerant in a predetermined gas-liquid separator among the plurality of gas-liquid separators. Even if the subcooling heat exchanger is provided on the lowest pressure side L, in order to prevent the refrigerant from flowing into the low pressure pressure reducing mechanism 21 and the heat absorber E2 in a two-phase state, at least it is located on the lowest pressure side L It is desirable to secure liquid refrigerant in the gas-liquid separator and supply the liquid refrigerant from the gas-liquid separator to the low-pressure pressure reducing mechanism 21 . For this purpose, it is necessary to control the rotation speeds of the compression mechanisms 11 to 14 based on the liquid levels of the N ⁇ 1 gas-liquid separators. At least two level sensors are required to keep track of the level of each of the N-1 gas-liquid separators.
  • the refrigerating apparatus 1 of the present embodiment does not include a number of decompression mechanisms and gas-liquid separators corresponding to the number of stages N when increasing the number of stages N, or a number of internal separators corresponding to the number of stages N
  • a single gas-liquid separator 33 is provided on the high pressure side H and internal heat exchangers 32 and 31 are provided on the low pressure side L without providing a heat exchanger.
  • the refrigeration system 1 of the present embodiment does not have the same number of gas-liquid separators as the required number of intermediate pressure injection stages (N-1), and the number of gas-liquid separators is less than the required intermediate pressure injection stage number (N-1). of gas-liquid separator 33.
  • the number of gas-liquid separators 33 provided in the refrigerating apparatus 1 is small with respect to the required number of stages (N ⁇ 1) for intermediate pressure injection, so gas-liquid separation that can occur when a plurality of gas-liquid separators are provided.
  • the degree of uneven distribution of the refrigerant between the vessels is reduced.
  • the effect of improving efficiency by increasing the number of compression stages N is ensured while suppressing the decrease in efficiency and the instability of the operating state due to the uneven distribution of the liquid refrigerant, and the operating state of the refrigeration system 1 is stabilized. be able to.
  • the refrigerating apparatus 1 of the present embodiment includes only the single gas-liquid separator 33 as a gas-liquid separator, the liquid amount in some of the plurality of gas-liquid separators is It is possible to ensure that the liquid refrigerant is stored in the specific gas-liquid separator 33 without falling into a state of exhaustion. Then, control based on the liquid level of the gas-liquid separator becomes unnecessary, and the liquid level sensor becomes unnecessary. Even if liquid level sensors are installed, the number can be reduced.
  • the following effects can be obtained. (1) Since only a single gas-liquid separator 33 is provided as a gas-liquid separator, unlike the case where a plurality of gas-liquid separators are provided, the liquid refrigerant moves between the gas-liquid separators Without doing so, it is possible to ensure that the liquid refrigerant is stored in a specific gas-liquid separator 33 . Therefore, there is no need to perform control based on the liquid level in the gas-liquid separator. The simplification of control can reduce the cost of the refrigeration system 1 .
  • the gas-liquid separator 33 Since the gas-liquid separator 33 is arranged on the high pressure side H with respect to the internal heat exchangers 32 and 31 , the saturated liquid flows from the gas-liquid separator 33 into the internal heat exchangers 32 and 31 . Therefore, supercooling can be applied to the refrigerant. As a result, the COP can be improved, the occurrence of flash can be suppressed, and the refrigeration system 1 can be operated stably and efficiently. does not need to flow into the subcooling heat exchanger. In other words, the refrigerant that has passed through the internal heat exchangers 32 and 31 should be allowed to flow directly into the low-pressure pressure reducing mechanism 21 .
  • the subcooling heat exchanger is not required as compared with the comparative example, and the refrigerant circuit configuration can be simplified, which can contribute to cost reduction, size reduction, and weight reduction of the device.
  • a sufficient degree of supercooling can be obtained by sequentially flowing the liquid refrigerant from the gas-liquid separator 33 into the two internal heat exchangers 32 and 31 . Therefore, in addition to being highly effective in improving efficiency and stabilizing operation, there is no need to add a supercooling heat exchanger with a large capacity in order to increase the degree of supercooling, which reduces costs and reduces the size and weight of the device. The effect of conversion is also great.
  • the high-pressure internal heat exchanger 32 and/or the low-pressure internal heat exchanger 31 is provided with an expansion valve as a decompression mechanism, by adjusting the degree of opening of the expansion valve, as shown in FIG. It is possible to perform intermediate pressure injection with a phase refrigerant.
  • the high-pressure internal heat exchanger 32 is provided with an expansion valve as the decompression mechanism 321
  • the second intermediate pressure P2 by the two-phase refrigerant is passed through the second intermediate pressure injection passage 42 by adjusting the opening degree of the expansion valve. injection (from r16 to r6) to the third stage compression mechanism 13 becomes possible.
  • the low-pressure internal heat exchanger 31 is provided with an expansion valve as the decompression mechanism 311, the injection of the first intermediate pressure P1 (from r19 to r3) by the two-phase refrigerant is controlled by adjusting the opening of the expansion valve. It becomes possible to perform this for the two-stage compression mechanism 12 . By injecting the two-phase refrigerant, the refrigerant suction temperature into the compression mechanism is lowered, so the discharge temperature can be suppressed to the allowable limit.
  • a gas-liquid separator is provided with a heat insulating material to keep the refrigerant at a low temperature.
  • the pressure in the gas-liquid separator is Since the saturation temperature is high, the temperature difference between the gas-liquid separator 33 and the outside air temperature is small. Therefore, the thickness of the heat insulating material provided in the gas-liquid separator 33 can be reduced, which contributes to cost reduction, miniaturization and weight reduction of the device.
  • the temperature at the liquid outlet of the gas-liquid separator 33 is 20°, which is the smallest temperature difference from the outside air temperature.
  • the liquid outlet temperature is according to cycle calculations. The same applies to the following. Although not shown, it has a single gas-liquid separator corresponding to the second intermediate pressure P2 , and two internal heat exchangers corresponding to the third intermediate pressure P3 and the first intermediate pressure P1 respectively. In the case the temperature at the liquid outlet of the gas-liquid separator is 2°.
  • the temperature at the liquid outlet of the gas-liquid separator is -12°.
  • one or more gas-liquid separators 33 and one or more internal heat exchangers 31 and 32 as two types of intermediate pressure injection means are combined. to satisfy the required number of intermediate pressure injection stages (N-1) corresponding to the number of compression stages N (3 or more), and the gas-liquid separator 33 is arranged on the high pressure side H of the internal heat exchangers 31 and 32.
  • N-1 the required number of intermediate pressure injection stages
  • the COP can be improved while using a low GWP refrigerant such as CO 2 , and the refrigeration system 1 can be stably operated while maintaining the discharge temperature below the allowable limit.
  • the refrigerating apparatus 1 does not necessarily have the high-pressure internal heat exchanger 32 and the low-pressure internal heat exchanger 31, and may have only a single internal heat exchanger, or may have three or more internal heat exchangers, depending on the number of stages N. of internal heat exchangers. Even in such a case, it is possible to obtain the same effects as those obtained by the above-described embodiment.
  • the refrigerating apparatus 1-2 shown in FIG. 4 includes N-stage (four-stage) compression mechanisms 11 to 14, and two gas-liquid separators 33 and 32 as N ⁇ 1 (three) intermediate pressure injection means. -2 and a single internal heat exchanger 31.
  • FIG. 5 is a Moliere diagram of the refrigerator 1-2.
  • the refrigerator 1-2 has three decompression mechanisms 21 to 23 forming a decompression unit 20, including a decompression mechanism 22 positioned between two gas-liquid separators 33 and 32-2. Therefore, it is operated by a cycle of 4-stage compression and 3-stage expansion.
  • the refrigerating device 1-2 also includes two gas-liquid separators 33 and 32-2, which are smaller than the required number of stages (N-1) for intermediate pressure injection. As a result, the degree of uneven distribution of the liquid refrigerant between the gas-liquid separators 33, 32-2 is reduced. As a result, it is possible to secure the effect of improving the efficiency by increasing the number of compression stages N while suppressing the deterioration of the cycle efficiency and the instability of the operating state, and contribute to the stabilization of the operating state of the refrigerating apparatus 1-2. can be done.
  • the gas-liquid separators 33 and 32-2 are arranged on the high pressure side H of the internal heat exchanger 31, the saturated liquid flows into the internal heat exchanger 31 from the gas-liquid separator 32-2. Therefore, the refrigerant can be subcooled (from r17 to r20 in FIG. 5). It is possible to operate stably and efficiently by supercooling, and there is no need to add a supercooling heat exchanger to obtain supercooling. can.
  • the gas-liquid separators 33, 32-2 are arranged on the high pressure side H of the internal heat exchanger 31, the gas-liquid separators 33, 32-2 on the low pressure side L of the internal heat exchanger 31, Compared to the case where 32-2 is arranged, the thickness of the heat insulating material can be reduced, which contributes to the miniaturization and weight reduction of the device.
  • the refrigerating devices 1 and 1-2 that circulate the refrigerant by a refrigerating cycle include a compression section 10 that includes three or more stages of compression mechanisms 11 to 14 that are connected in series and each compresses the refrigerant, and discharge from the compression section 10 A first heat exchanger (E1) for releasing the heat of the discharged refrigerant to the outside air, a relatively high pressure side high pressure pressure reducing mechanism 22, and a relatively low pressure side low pressure pressure reducing mechanism 21, the first heat exchanger A decompression unit 20 that reduces the pressure of the refrigerant that has passed through E1 by a high-pressure decompression mechanism 22 and a low-pressure decompression mechanism 21, a second heat exchanger (E2) that causes the refrigerant that has passed through the decompression unit 20 to absorb heat from a heat load, and a high-pressure decompression mechanism 22.
  • a liquid refrigerant, which is a phase refrigerant, and a two-phase refrigerant, which is a part of the liquid refrigerant whose pressure is reduced, are heat-exchanged to absorb heat from the liquid refrigerant.
  • the refrigerating apparatus 1 is provided with a highest pressure gas-liquid separator (33), which is the gas-liquid separator 33 located on the highest pressure side H and to which the refrigerant is directly supplied from the high-pressure decompression mechanism 22.
  • the refrigerating apparatus 1, 1-2 includes the lowest pressure internal heat exchanger (31), which is the internal heat exchanger 31 located on the lowest pressure side L and causes the refrigerant to flow directly into the low pressure decompression mechanism 21.
  • the internal heat exchangers 31, 32 include expansion valves (311, 321) that reduce the pressure of a portion of the liquid refrigerant to expand it.
  • the refrigerating apparatus 1 includes two or more internal heat exchangers 31 and 32, and the capacity of the internal heat exchanger 32 located on the relatively high pressure side H is determined by the capacity of the internal heat exchanger 32 located on the relatively low pressure side. greater than the capacity of the exchanger 31.
  • the refrigerant contains at least a portion of carbon dioxide.

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Abstract

Provided is a refrigeration apparatus capable of stably operating while improving the efficiency of a refrigeration cycle. The refrigeration apparatus is provided with a compression section including three or more stages of compression mechanisms, a first heat exchanger, a pressure reduction section, a second heat exchanger, a plurality of intermediate-pressure injection flow paths that are provided between a high-pressure pressure reduction mechanism and a low-pressure pressure reduction mechanism and supply a refrigerant at an intermediate pressure, which is between a high pressure and a low pressure, between the compression mechanisms, a gas-liquid separator that supplies a gas-phase refrigerant to a high-pressure intermediate-pressure injection flow path on a relatively high-pressure side among the plurality of intermediate-pressure injection flow paths, and an internal heat exchanger that supplies a refrigerant that has absorbed heat from a liquid refrigerant, which is a liquid-phase refrigerant supplied from the gas-liquid separator, by heat exchange between the liquid refrigerant and a two-phase refrigerant obtained by reducing pressure of a part of the liquid refrigerant to the intermediate-pressure injection flow path on a low-pressure side relative to the high-pressure intermediate-pressure injection flow path.

Description

多段圧縮冷凍装置Multi-stage compression refrigeration equipment
 本開示は、多段に亘り冷媒を圧縮する冷凍装置に関する。 The present disclosure relates to a refrigeration system that compresses refrigerant in multiple stages.
 特許文献1は、2段圧縮機構を備えた冷凍装置を開示する。かかる冷凍装置は、密閉ハウジング内に低段圧縮機構および高段圧縮機構を備えた電動圧縮機と、放熱器と、高圧膨張弁と、気液分離器と、低圧膨張弁と、蒸発器と、ガスインジェクション配管とを備えている。ガスインジェクション配管により、気液分離器から電動圧縮機のハウジング内に導入されたガス冷媒は、低段圧縮機構からハウジング内に吐出された冷媒と共に高段圧縮機構へと吸入される。 Patent Document 1 discloses a refrigeration system with a two-stage compression mechanism. Such a refrigeration system includes an electric compressor having a low-stage compression mechanism and a high-stage compression mechanism in a closed housing, a radiator, a high-pressure expansion valve, a gas-liquid separator, a low-pressure expansion valve, an evaporator, It is equipped with gas injection piping. Gas refrigerant introduced into the housing of the electric compressor from the gas-liquid separator through the gas injection pipe is sucked into the high-stage compression mechanism together with refrigerant discharged into the housing from the low-stage compression mechanism.
特開2017-44420号公報JP 2017-44420 A
 地球温暖化係数(GWP;Global Warming Potential)の低減、およびエネルギー消費効率(COP;Coefficient of Performance)の向上を目的として、GWPが低い冷媒が採用されるとともに、2段圧縮機構を含む冷凍装置の開発および製品化が進められている。
 冷媒としてCOを含む冷媒が採用される場合には、高圧運転に伴い高い冷媒吐出温度を許容限度に抑えるため、放熱器に設定される高圧と、蒸発器に設定される低圧との間の中間圧の冷媒を気液分離器から低段圧縮機構と高段圧縮機構との間に導入すること(中間圧インジェクション)が有効である。かかる構成によれば、低段圧縮機構から吐出される冷媒の温度と比べて低温の冷媒のインジェクションにより、吐出温度を抑制することができる。それに加え、気液分離器から低圧膨張弁に液冷媒が供給されることにより、蒸発器によって得られるエンタルピが単段圧縮の場合に対して拡大するため、冷凍能力を増加させ、COPを向上させることができる。
A refrigerant with a low GWP is adopted for the purpose of reducing the global warming potential (GWP) and improving the energy consumption efficiency (COP; Coefficient of Performance). Development and commercialization are underway.
When a refrigerant containing CO2 is used as the refrigerant, in order to keep the high refrigerant discharge temperature within the permissible limit due to high-pressure operation, the high pressure set for the radiator and the low pressure set for the evaporator must be maintained. It is effective to introduce intermediate-pressure refrigerant from the gas-liquid separator between the low-stage compression mechanism and the high-stage compression mechanism (intermediate-pressure injection). According to such a configuration, it is possible to suppress the discharge temperature by injecting refrigerant having a temperature lower than that of the refrigerant discharged from the low-stage compression mechanism. In addition, since the liquid refrigerant is supplied from the gas-liquid separator to the low-pressure expansion valve, the enthalpy obtained by the evaporator is expanded compared to the case of single-stage compression, so the refrigeration capacity is increased and the COP is improved. be able to.
 低GWPの冷媒を採用する冷凍装置にあって、圧縮機構の段数をさらに増やしていくことにより、圧縮機からの吐出温度を抑制しつつ、COPが高められた冷凍装置を実現することが望まれる。しかしながら、本開示の発明者による試験研究によると、段数を3以上に増やした場合における複数の気液分離器のそれぞれの液面が定まらないという知見を得た。一般に、フラッシュ(冷媒における気泡の発生)が起こるのを避けるため、気液分離器に液冷媒を貯留させるとともに、過冷却用熱交換器により冷媒に過冷却を与える。
 例えば、圧縮機構・膨張弁の段数を例えば「4」に増やした場合、4段圧縮4膨張サイクルにより運転される冷凍装置においては、局所的な冷媒圧力の変動等に起因して、3つの気液分離器のそれぞれに貯留される液冷媒の液位に偏りが生じてしまう。液冷媒の偏在により、蒸発器に冷媒を流入させる低圧側の気液分離器に液を確保できず、冷媒が二相の状態で低圧減圧機構および蒸発器に流入するのならば、効率が悪化するとともに、冷凍装置の動作が不安定となる可能性がある。それを避けるため、3つの気液分離器のそれぞれにおける液位を検知し、液位に基づいて圧縮機の動作を制御することが考えられるが、そうした制御は難しい。
In a refrigerating device that employs a refrigerant with a low GWP, it is desired to realize a refrigerating device that increases the COP while suppressing the discharge temperature from the compressor by further increasing the number of stages of the compression mechanism. . However, according to test research by the inventor of the present disclosure, it was found that the liquid level of each of the plurality of gas-liquid separators is not fixed when the number of stages is increased to 3 or more. Generally, in order to avoid flashing (generation of air bubbles in the refrigerant), the liquid refrigerant is stored in the gas-liquid separator, and the refrigerant is supercooled by the supercooling heat exchanger.
For example, when the number of stages of the compression mechanism/expansion valve is increased to, for example, "4", in a refrigeration system operated by a four-stage compression and four-expansion cycle, due to local fluctuations in refrigerant pressure, etc., three gas The liquid level of the liquid refrigerant stored in each of the liquid separators is uneven. Due to the uneven distribution of the liquid refrigerant, if the liquid cannot be secured in the gas-liquid separator on the low-pressure side that flows the refrigerant into the evaporator, and the refrigerant flows into the low-pressure decompression mechanism and the evaporator in a two-phase state, the efficiency will deteriorate. In addition, the operation of the refrigeration system may become unstable. In order to avoid this, it is conceivable to detect the liquid level in each of the three gas-liquid separators and control the operation of the compressor based on the liquid level, but such control is difficult.
 以上より、本開示は、冷凍サイクルの効率を向上させつつ、安定して動作させることが可能な冷凍装置を提供することを目的とする。 In view of the above, an object of the present disclosure is to provide a refrigeration system that can stably operate while improving the efficiency of the refrigeration cycle.
 本開示は、冷凍サイクルにより冷媒を循環させる冷凍装置であって、直列に接続されてそれぞれ冷媒を圧縮する3段以上の圧縮機構を含む圧縮部と、圧縮部から吐出された冷媒を外気へと放熱させる第1熱交換器と、相対的に高圧側の高圧減圧機構と、相対的に低圧側の低圧減圧機構とを含み、第1熱交換器を経た冷媒の圧力を高圧減圧機構および低圧減圧機構により減少させる減圧部と、減圧部を経た冷媒を熱負荷から吸熱させる第2熱交換器と、高圧減圧機構と低圧減圧機構との間に与えられ、第1熱交換器に設定される高圧と、第2熱交換器に設定される低圧との間の中間圧の冷媒を圧縮機構と圧縮機構との間に供給する複数の中間圧インジェクション流路と、複数の中間圧インジェクション流路のうち相対的に高圧側の高圧中間圧インジェクション流路に気相の冷媒を供給する気液分離器と、気液分離器から供給される液相の冷媒である液冷媒と、液冷媒の一部を減圧させてなる二相冷媒とを熱交換させることで液冷媒から吸熱させた冷媒を、高圧中間圧インジェクション流路に対して低圧側の中間圧インジェクション流路に供給する内部熱交換器と、を備える。 The present disclosure is a refrigerating device that circulates a refrigerant by a refrigerating cycle, and includes a compression section that includes three or more stages of compression mechanisms that are connected in series and each compresses the refrigerant, and the refrigerant discharged from the compression section is discharged to the outside air. A first heat exchanger that dissipates heat, a high-pressure pressure reducing mechanism on the relatively high pressure side, and a low pressure pressure reducing mechanism on the relatively low pressure side. A high-pressure decompression unit that is reduced by a mechanism, a second heat exchanger that causes the refrigerant that has passed through the decompression unit to absorb heat from a heat load, and a high pressure that is provided between the high-pressure decompression mechanism and the low-pressure decompression mechanism and set in the first heat exchanger and a plurality of intermediate pressure injection passages for supplying intermediate pressure refrigerant between the compression mechanism and the low pressure set in the second heat exchanger, and among the plurality of intermediate pressure injection passages A gas-liquid separator that supplies gas-phase refrigerant to the high-pressure intermediate pressure injection passage on the relatively high-pressure side, a liquid refrigerant that is a liquid-phase refrigerant supplied from the gas-liquid separator, and a part of the liquid refrigerant an internal heat exchanger that supplies the refrigerant absorbed heat from the liquid refrigerant by exchanging heat with the pressure-reduced two-phase refrigerant to the intermediate-pressure injection passage on the low-pressure side with respect to the high-pressure intermediate-pressure injection passage; Prepare.
 本開示においては、2種類の中間圧インジェクション手段としての1つ以上の気液分離器および1つ以上の内部熱交換器を組み合わせることにより、圧縮の段数N(3以上)に相応の中間圧インジェクションの必要段数(N-1)を満足するとともに、内部熱交換器に対して高圧側に気液分離器を配置する。そうすると、中間圧インジェクションの各段に気液分離器を配置する場合と比べて気液分離器の数が少ない分、液冷媒の偏在に起因する効率低下と運転状態の不安定さを抑えることができる。
 加えて、内部熱交換器に対して高圧側に気液分離器が配置されるため、気液分離器から内部熱交換器へと飽和液を流入させて冷媒に過冷却を与えることができる。過冷却により安定して効率よく運転させることができる上、内部熱交換器を経た冷媒を流入させる過冷却熱交換器を備える必要がないので、コストの低減、装置の小型化および軽量化に寄与することができる。
In the present disclosure, by combining one or more gas-liquid separators and one or more internal heat exchangers as two types of intermediate pressure injection means, intermediate pressure injection corresponding to the number of compression stages N (3 or more) and the gas-liquid separator is arranged on the high-pressure side of the internal heat exchanger. As a result, the number of gas-liquid separators is smaller than when a gas-liquid separator is arranged at each stage of the intermediate pressure injection, so it is possible to suppress the decrease in efficiency and the instability of the operating state due to the uneven distribution of the liquid refrigerant. can.
In addition, since the gas-liquid separator is arranged on the high-pressure side of the internal heat exchanger, saturated liquid can flow from the gas-liquid separator into the internal heat exchanger to supercool the refrigerant. Stable and efficient operation is possible by supercooling, and there is no need to install a supercooling heat exchanger for inflowing the refrigerant that has passed through the internal heat exchanger, which contributes to cost reduction, miniaturization and weight reduction of the device. can do.
本開示の実施形態に係る冷凍装置の回路構成を示す図である。1 is a diagram showing a circuit configuration of a refrigeration system according to an embodiment of the present disclosure; FIG. 図1に示す冷凍装置のモリエール線図である。2 is a Moliere diagram of the refrigeration system shown in FIG. 1. FIG. 比較例に係る冷凍装置のモリエール線図である。It is a Moliere diagram of a refrigeration system according to a comparative example. 本開示の変形例に係る冷凍装置の回路構成を示す図である。FIG. 10 is a diagram showing a circuit configuration of a refrigeration system according to a modified example of the present disclosure; 図4に示す冷凍装置のモリエール線図である。5 is a Moliere diagram of the refrigeration system shown in FIG. 4; FIG.
 以下、添付図面を参照しながら、本開示の一実施形態について説明する。
〔冷凍サイクルの基本要素〕
 図1に示す多段圧縮式の冷凍装置1は、冷凍サイクルにより冷媒を循環させることにより、外気を熱源として、適宜な熱負荷(例えば、装置筐体内の空気および収容物品)を冷却する。
 冷凍装置1は、冷凍サイクルをなす基本要素として、冷媒を圧縮する圧縮部10と、冷媒を外気へと放熱させる放熱器E1(第1熱交換器)と、冷媒の圧力を減少させる減圧部20と、熱負荷から冷媒へと吸熱させる吸熱器E2(第2熱交換器)とを備えている。圧縮部10により圧縮された冷媒は、放熱器E1、減圧部20、および吸熱器E2をこの順序で流れ、圧縮部10へと吸入される。
An embodiment of the present disclosure will be described below with reference to the accompanying drawings.
[Basic elements of the refrigeration cycle]
The multi-stage compression refrigerating apparatus 1 shown in FIG. 1 circulates a refrigerant in a refrigerating cycle to cool an appropriate heat load (for example, the air in the apparatus housing and stored items) using outside air as a heat source.
The refrigerating apparatus 1 includes, as basic elements forming a refrigerating cycle, a compression section 10 for compressing the refrigerant, a radiator E1 (first heat exchanger) for releasing heat from the refrigerant to the outside air, and a decompression section 20 for reducing the pressure of the refrigerant. and a heat absorber E2 (second heat exchanger) that absorbs heat from the heat load to the refrigerant. The refrigerant compressed by compression section 10 flows through radiator E<b>1 , decompression section 20 , and heat absorber E<b>2 in this order, and is sucked into compression section 10 .
 本実施形態の冷凍装置1の冷媒回路には、例えば、HFC(Hydro Fluoro Carbon)冷媒、HFO(Hydro Fluoro Olefin)冷媒、二酸化炭素(CO)冷媒、炭化水素系冷媒等から任意に選択される単一冷媒あるいは混合冷媒が封入されている。GWP低減の観点から、本実施形態では、二酸化炭素(CO)を少なくとも一部に含む冷媒を採用している。 The refrigerant circuit of the refrigeration apparatus 1 of the present embodiment is arbitrarily selected from, for example, HFC (Hydro Fluoro Carbon) refrigerant, HFO (Hydro Fluoro Olefin) refrigerant, carbon dioxide (CO 2 ) refrigerant, hydrocarbon refrigerant, and the like. A single refrigerant or mixed refrigerant is enclosed. From the viewpoint of GWP reduction, this embodiment employs a refrigerant containing at least a portion of carbon dioxide (CO 2 ).
〔複数段の圧縮機構・減圧機構〕
 圧縮部10は、直列に接続される複数段の圧縮機構11~14を含んでいる。第1段圧縮機構11、第2段圧縮機構12、第3段圧縮機構13、および第4段圧縮機構14は、低圧側Lから高圧側Hへと複数のステップに亘り冷媒を順次圧縮する。圧縮部10の段数Nは3以上であり、一例として段数Nは「4」である。第1段~第4段は、n1,n2,n3,n4の符号により示されている。
[Multi-stage compression mechanism/decompression mechanism]
The compression section 10 includes multiple stages of compression mechanisms 11 to 14 connected in series. The first-stage compression mechanism 11, the second-stage compression mechanism 12, the third-stage compression mechanism 13, and the fourth-stage compression mechanism 14 sequentially compress the refrigerant from the low-pressure side L to the high-pressure side H over a plurality of steps. The number of stages N of the compression unit 10 is 3 or more, and as an example, the number of stages N is "4". The first to fourth stages are indicated by the symbols n1, n2, n3 and n4.
 図2は、冷凍装置1の冷媒の圧力と比エンタルピとの関係を示すモリエール線図である。図2に示されているr1,r2…等の記号は、図1に示されている同じ記号と対応している。
 図2に示すように、冷凍装置1は、4段圧縮、2段膨張の冷凍サイクルにより運転される。
FIG. 2 is a Moliere diagram showing the relationship between the pressure of the refrigerant in the refrigeration system 1 and the specific enthalpy. The symbols r1, r2, etc. shown in FIG. 2 correspond to the same symbols shown in FIG.
As shown in FIG. 2, the refrigeration system 1 is operated in a four-stage compression, two-stage expansion refrigeration cycle.
 本実施形態の冷凍装置1は、2つの電動圧縮機101,102と、電動圧縮機101,102のそれぞれの電動機や膨張弁等の動作を制御可能な制御装置15と、電動圧縮機101,102の間に設けられる中間冷却熱交換器16とを備えている。
 第1電動圧縮機101は、直列に接続される第1段圧縮機構11および第2段圧縮機構12と、それら圧縮機構11,12を収容するハウジング101Aと、圧縮機構11,12を回転駆動する電動機101Bとを備えている。
 第2電動圧縮機102は、直列に接続される第3段圧縮機構13および第4段圧縮機構14と、それら圧縮機構13,14を収容するハウジング102Aと、圧縮機構13,14を回転駆動する電動機102Bとを備えている。
The refrigeration system 1 of this embodiment includes two electric compressors 101 and 102, a control device 15 capable of controlling the operation of the electric motors and expansion valves of the electric compressors 101 and 102, and the electric compressors 101 and 102. and an intermediate cooling heat exchanger 16 provided between.
The first electric compressor 101 rotates the first stage compression mechanism 11 and the second stage compression mechanism 12 that are connected in series, a housing 101A that houses the compression mechanisms 11 and 12, and the compression mechanisms 11 and 12. and an electric motor 101B.
The second electric compressor 102 rotates the third stage compression mechanism 13 and the fourth stage compression mechanism 14 that are connected in series, a housing 102A that houses the compression mechanisms 13 and 14, and the compression mechanisms 13 and 14. and an electric motor 102B.
 中間冷却熱交換器16は、第2段圧縮機構12から吐出された冷媒を外気への放熱により冷却し、第3段圧縮機構13の吸入部へと供給する(図2における作動点r4からr5へ)。 The intermediate cooling heat exchanger 16 cools the refrigerant discharged from the second-stage compression mechanism 12 by radiating heat to the outside air, and supplies the refrigerant to the suction portion of the third-stage compression mechanism 13 (operating points r4 to r5 in FIG. 2). What).
 第1段圧縮機構11は、例えば、ピストンロータおびシリンダを含むロータリー式圧縮機構に相当する。第3段圧縮機構13も同様である。第2段圧縮機構12は、例えば、一対のスクロール部材を含むスクロール式圧縮機構に相当する。第4段圧縮機構14も同様である。 The first stage compression mechanism 11 corresponds to, for example, a rotary compression mechanism including a piston rotor and a cylinder. The third stage compression mechanism 13 is also the same. The second stage compression mechanism 12 corresponds to, for example, a scroll compression mechanism including a pair of scroll members. The same applies to the fourth stage compression mechanism 14 .
 減圧部20は、相対的に低圧側Lの低圧減圧機構21と、相対的に高圧側Hの高圧減圧機構22とを含んでいる。減圧機構21,22はそれぞれ、膨張弁、あるいはキャピラリーチューブ等であってよい。特に、絞りの開度調整が可能な膨張弁であることが好ましい。
 高圧減圧機構22および低圧減圧機構21は、この順で、放熱器E1を経た冷媒の圧力を順次減少させる。
The decompression unit 20 includes a low pressure decompression mechanism 21 on the relatively low pressure side L and a high pressure decompression mechanism 22 on the relatively high pressure side H. As shown in FIG. Each of the decompression mechanisms 21 and 22 may be an expansion valve, a capillary tube, or the like. In particular, it is preferable that the expansion valve is capable of adjusting the degree of opening of the throttle.
The high-pressure pressure reducing mechanism 22 and the low-pressure pressure reducing mechanism 21 sequentially reduce the pressure of the refrigerant that has passed through the radiator E1 in this order.
 図2に示すように、複数段n1,n2,n3,n4の圧縮機構11~14により冷媒が圧縮されることで、冷媒の圧力が段階的に増大する。これに伴い冷媒の吐出温度が上昇する。
 冷媒を外気へと放熱させる中間冷却熱交換器16の作用により冷媒の温度を低下させることで(r4からr5へ)、圧縮部10の全体としての吐出温度の抑制に寄与することができる。
As shown in FIG. 2, the pressure of the refrigerant increases stepwise as the refrigerant is compressed by the multi-stage compression mechanisms 11-14 of n1, n2, n3, and n4. Along with this, the discharge temperature of the refrigerant rises.
Lowering the temperature of the refrigerant (from r4 to r5) by the action of the intermediate cooling heat exchanger 16 that releases heat from the refrigerant to the outside air can contribute to suppressing the discharge temperature of the compression section 10 as a whole.
 圧縮の第1段n1への吸入圧力と第2段n2からの吐出圧力との間の圧力を第1中間圧Pと称する。同様に、第2段n2への吸入圧力と第3段n3からの吐出圧力との間の圧力を第2中間圧Pと称し、第3段n3への吸入圧力と第4段n4からの吐出圧力との間の圧力を第3中間圧Pと称する。P<P<Pの関係が成り立つ。
 COの臨界温度は、他の冷媒、例えば、HFC;Hydro Fluoro Carbon)の臨界温度よりも低い。そのため、冷凍装置1の定常運転において、CO冷媒は、複数段に亘り冷媒を圧縮する圧縮部10により臨界圧力Pを超える圧力まで圧縮される。但し、放熱器E1および高圧減圧機構22を経た冷媒の圧力(r12,r13,r14)、すなわち第3中間圧Pは、臨界圧力P以下に留まる。
The pressure between the suction pressure to the first stage n1 of compression and the discharge pressure from the second stage n2 is called the first intermediate pressure P1 . Similarly, the pressure between the suction pressure to the second stage n2 and the discharge pressure from the third stage n3 is called a second intermediate pressure P2 , and the pressure from the suction pressure to the third stage n3 and the pressure from the fourth stage n4 is The pressure between it and the discharge pressure is called a third intermediate pressure P3 . A relationship of P 1 <P 2 <P 3 holds.
The critical temperature of CO2 is lower than that of other refrigerants such as HFCs (Hydro Fluoro Carbon). Therefore, in steady operation of the refrigeration system 1, the CO2 refrigerant is compressed to a pressure exceeding the critical pressure PC by the compression section 10 that compresses the refrigerant in multiple stages. However, the pressure (r12, r13, r14) of the refrigerant that has passed through the radiator E1 and the high-pressure pressure reducing mechanism 22, that is, the third intermediate pressure P3 remains below the critical pressure PC .
(中間圧インジェクション)
 冷凍装置1は、低圧減圧機構21と高圧減圧機構22との間における冷媒の気液分離により得られた中間圧の冷媒を第1~第4段圧縮機構11~14のそれぞれの間に供給する中間圧インジェクションを実施する。そのため、冷凍装置1は、低圧減圧機構21および高圧減圧機構22の間に与えられるN-1個の中間圧インジェクション手段(31~33)と、中間圧インジェクション手段(31~33)にそれぞれ対応するN-1個の中間圧インジェクション流路41~43とを備えている。
(intermediate pressure injection)
The refrigeration system 1 supplies intermediate-pressure refrigerant obtained by gas-liquid separation of the refrigerant between the low-pressure pressure reducing mechanism 21 and the high-pressure pressure reducing mechanism 22 between the first to fourth stage compression mechanisms 11 to 14, respectively. Intermediate pressure injection is performed. Therefore, the refrigerating apparatus 1 corresponds to N-1 intermediate pressure injection means (31 to 33) provided between the low pressure pressure reducing mechanism 21 and the high pressure pressure reducing mechanism 22 and the intermediate pressure injection means (31 to 33), respectively. It has N−1 intermediate pressure injection flow paths 41 to 43 .
 各中間圧インジェクション流路41~43を通じて、直列接続の圧縮機構11~14のそれぞれの間に中間圧P,P,Pの冷媒が供給されることにより、第2~第4段圧縮機構12~14のそれぞれの吐出温度を低減することができる。
 なお、中間圧インジェクション流路41~43には、それぞれ、必要に応じてバルブを設けることができる。運転条件に応じて当該バルブを開または閉に切り替えるようにしてもよい。
Refrigerant at intermediate pressures P 1 , P 2 , and P 3 is supplied between the serially connected compression mechanisms 11 to 14 through the intermediate pressure injection passages 41 to 43, respectively, thereby performing second to fourth stage compression. The discharge temperature of each of the mechanisms 12-14 can be reduced.
A valve can be provided in each of the intermediate pressure injection flow paths 41 to 43 as required. The valve may be switched open or closed depending on operating conditions.
 中間圧インジェクション手段(31~33)は、図1に示すように、単一の気液分離器33(受液器)と、内部熱交換器32,31とからなる。気液分離器33は、内部熱交換器32,31に対して高圧側Hに配置されている。高圧内部熱交換器32は、低圧内部熱交換器31に対して高圧側Hに配置されている。
 これら気液分離器33、内部熱交換器32、および内部熱交換器31は、それぞれ、対応する中間圧インジェクション流路41~43を通じて、中間圧の冷媒を第2~第4段圧縮機構12~14に供給する。
The intermediate pressure injection means (31-33) consist of a single gas-liquid separator 33 (liquid receiver) and internal heat exchangers 32, 31, as shown in FIG. The gas-liquid separator 33 is arranged on the high pressure side H with respect to the internal heat exchangers 32 and 31 . The high pressure internal heat exchanger 32 is arranged on the high pressure side H with respect to the low pressure internal heat exchanger 31 .
These gas-liquid separator 33, internal heat exchanger 32, and internal heat exchanger 31 pass the intermediate-pressure refrigerant through corresponding intermediate-pressure injection passages 41-43 to the second to fourth-stage compression mechanisms 12-4, respectively. 14.
 第4段圧縮機構14から吐出された冷媒は、高圧減圧機構22により減圧されて気液分離器33へと流入する。気液分離器33に流入した冷媒は、貯留タンク33Aの内部における密度差に基づいて気相と液相とに分離される。これは、図2に示すように、r12から、r13およびr14への状態変化に相当する。貯留タンク33A内の液面よりも上方の気相領域33Bには、第3中間圧インジェクション流路43が接続されている。 The refrigerant discharged from the fourth stage compression mechanism 14 is decompressed by the high pressure decompression mechanism 22 and flows into the gas-liquid separator 33 . The refrigerant that has flowed into the gas-liquid separator 33 is separated into a gas phase and a liquid phase based on the density difference inside the storage tank 33A. This corresponds to the state change from r12 to r13 and r14 as shown in FIG. A third intermediate pressure injection channel 43 is connected to the gas phase region 33B above the liquid surface in the storage tank 33A.
 気液分離器33において液相と分離された第3中間圧Pの気相の冷媒は、第3中間圧インジェクション流路43を通じて高圧側Hの中間圧インジェクションに供される(r13からr8へ)。
 第3中間圧インジェクション流路43により第4段圧縮機構14へ供給される第3中間圧Pの冷媒の温度は、第3段圧縮機構13から吐出される冷媒の温度よりも低い。そのため、第3中間圧インジェクション流路43により供給する冷媒と、第3段圧縮機構13から吐出される冷媒との全体として、第4段圧縮機構14へと吸入させる冷媒の温度が低下する(r7からr8へ)。そうすると、第4段圧縮機構14から吐出される冷媒の温度も低下するから、中間圧ガスインジェクションは、吐出温度の低減に寄与する。
The gas-phase refrigerant at the third intermediate pressure P3 separated from the liquid phase in the gas-liquid separator 33 is supplied to the intermediate-pressure injection on the high-pressure side H through the third intermediate-pressure injection passage 43 (from r13 to r8 ).
The temperature of the refrigerant at the third intermediate pressure P3 supplied to the fourth stage compression mechanism 14 through the third intermediate pressure injection passage 43 is lower than the temperature of the refrigerant discharged from the third stage compression mechanism 13 . Therefore, the temperature of the refrigerant to be sucked into the fourth stage compression mechanism 14 is lowered (r7 to r8). As a result, the temperature of the refrigerant discharged from the fourth stage compression mechanism 14 also drops, so the intermediate pressure gas injection contributes to the reduction of the discharge temperature.
 一方、貯留タンク33Aに貯留される液相の冷媒(液冷媒)は、高圧内部熱交換器32および低圧内部熱交換器31へと供給され、高圧内部熱交換器32および低圧内部熱交換器31によりそれぞれ過冷却が与えられるのと並行して、その一部が第2中間圧インジェクション流路42および第1中間圧インジェクション流路41のそれぞれを通じて、第3中間圧インジェクションに対して低圧側Lの中間圧インジェクションに供される。中間圧P,P,Pのインジェクションの実施に伴い、冷媒の流量は順次減少する。そのため、高圧減圧機構22から低圧減圧機構21までの冷媒の流れの上流である高圧内部熱交換器32の能力は、下流の低圧内部熱交換器31の能力よりも大きい。冷凍装置1の定格条件において、高圧内部熱交換器32の能力は、低圧内部熱交換器31の能力に対して例えば、2.5倍程度大きい。 On the other hand, the liquid-phase refrigerant (liquid refrigerant) stored in the storage tank 33A is supplied to the high-pressure internal heat exchanger 32 and the low-pressure internal heat exchanger 31, and the high-pressure internal heat exchanger 32 and the low-pressure internal heat exchanger 31 While subcooling is provided by each, a part thereof passes through the second intermediate pressure injection passage 42 and the first intermediate pressure injection passage 41, respectively, to the third intermediate pressure injection. It is subjected to intermediate pressure injection. The flow rate of the refrigerant gradually decreases as the injection of the intermediate pressures P 1 , P 2 and P 3 is performed. Therefore, the capacity of the high-pressure internal heat exchanger 32 upstream of the refrigerant flow from the high-pressure pressure reducing mechanism 22 to the low-pressure pressure reducing mechanism 21 is greater than the capacity of the low-pressure internal heat exchanger 31 downstream. Under the rated conditions of the refrigeration system 1 , the capacity of the high-pressure internal heat exchanger 32 is, for example, about 2.5 times as large as the capacity of the low-pressure internal heat exchanger 31 .
 高圧内部熱交換器32および低圧内部熱交換器31のいずれも、気液分離器33から供給される液冷媒と、気液分離器33から供給される液冷媒の一部を減圧機構(321,311)により減圧させてなる二相冷媒とを熱交換させる。
 高圧内部熱交換器32は、飽和状態にある気液分離器33の内部から供給される液冷媒を流入させる主流路320と、減圧機構321と、気液分離器33から供給される液冷媒の一部を減圧機構321へと流入させる分岐流路322と、減圧機構321による第3中間圧Pから第2中間圧Pへの減圧(図2におけるr14からr15へ)を経た二相冷媒を流入させる吸熱流路323とを備えている。
Both the high-pressure internal heat exchanger 32 and the low-pressure internal heat exchanger 31 depressurize the liquid refrigerant supplied from the gas-liquid separator 33 and part of the liquid refrigerant supplied from the gas-liquid separator 33 through the decompression mechanism (321, 311) to exchange heat with a two-phase refrigerant that is depressurized.
The high-pressure internal heat exchanger 32 includes a main flow path 320 into which the liquid refrigerant supplied from inside the gas-liquid separator 33 in a saturated state flows, a decompression mechanism 321, and the liquid refrigerant supplied from the gas-liquid separator 33. A two-phase refrigerant that has undergone a branch flow path 322 that partially flows into the decompression mechanism 321 and the decompression from the third intermediate pressure P3 to the second intermediate pressure P2 by the decompression mechanism 321 (from r14 to r15 in FIG. 2) and a heat absorption channel 323 into which the heat is introduced.
 吸熱流路323を流れる冷媒は、主流路320を流れる冷媒から吸熱することでガス化し(r15からr16へ)、第2中間圧インジェクション流路42を通じて第3段圧縮機構13へと吸入される。
 一方、主流路320を流れる冷媒は、吸熱流路323を流れる冷媒へと放熱することで過冷却され(r14からr17へ)、低圧内部熱交換器31へと流入する。
The refrigerant flowing through the heat absorption passage 323 is gasified (from r15 to r16) by absorbing heat from the refrigerant flowing through the main passage 320 , and is sucked into the third stage compression mechanism 13 through the second intermediate pressure injection passage 42 .
On the other hand, the refrigerant flowing through the main flow path 320 is subcooled (from r14 to r17) by dissipating heat to the refrigerant flowing through the heat absorption flow path 323, and flows into the low-pressure internal heat exchanger 31.
 第2中間圧インジェクション流路42により、第2中間圧Pの冷媒を第3段圧縮機構13の吸入部へと供給すると(r16からr6へ)、中間冷却熱交換器16から流出して第3段圧縮機構13へと吸入される冷媒の温度が低下する(r5からr6へ)。第2段圧縮機構12と第3段圧縮機構13との間においては、中間圧Pのインジェクション作用に加え、中間冷却熱交換器16による作用(r4からr5へ)によっても第3段圧縮機構13への吸入温度が低下するため、吐出温度をより抑えることができる。 When the second intermediate pressure injection flow path 42 supplies the refrigerant at the second intermediate pressure P2 to the suction portion of the third stage compression mechanism 13 (from r16 to r6), it flows out of the intermediate cooling heat exchanger 16 and flows into the third stage. The temperature of the refrigerant sucked into the three-stage compression mechanism 13 decreases (from r5 to r6). Between the second-stage compression mechanism 12 and the third-stage compression mechanism 13, in addition to the injection action of the intermediate pressure P2 , the third-stage compression mechanism is also affected by the action of the intermediate cooling heat exchanger 16 (from r4 to r5). Since the intake temperature to 13 is lowered, the discharge temperature can be further suppressed.
 低圧内部熱交換器31は、高圧内部熱交換器32から流出した過冷却状態の液冷媒(過冷却液)を流入させる主流路310と、減圧機構311と、過冷却液の一部を減圧機構311へと流入させる分岐流路312と、減圧機構311による第2中間圧Pから第1中間圧Pへの減圧(r17からr18へ)を経た二相冷媒を流入させる吸熱流路313とを備えている。吸熱流路313を流れる冷媒は、主流路310を流れる冷媒から吸熱することでガス化し(r18からr19へ)、第1中間圧インジェクション流路41を通じて第2段圧縮機構12へと吸入される(r19からr3へ)。これによって第2段圧縮機構12へと吸入させる冷媒の温度が低下する(r2からr3へ)。 The low-pressure internal heat exchanger 31 includes a main flow path 310 into which the supercooled liquid refrigerant (supercooled liquid) flowing out from the high-pressure internal heat exchanger 32 flows, a pressure reducing mechanism 311, and a pressure reducing mechanism for part of the supercooled liquid. 311, and an endothermic flow path 313 into which the two-phase refrigerant that has undergone decompression (from r17 to r18) from the second intermediate pressure P2 to the first intermediate pressure P1 by the decompression mechanism 311 flows. It has The refrigerant flowing through the heat absorption passage 313 absorbs heat from the refrigerant flowing through the main passage 310 to be gasified (from r18 to r19), and is sucked into the second stage compression mechanism 12 through the first intermediate pressure injection passage 41 ( r19 to r3). As a result, the temperature of the refrigerant sucked into the second stage compression mechanism 12 is lowered (from r2 to r3).
 一方、主流路310を流れる冷媒は、吸熱流路313を流れる冷媒へと放熱することで過冷却度を増大させ(r17からr20へ)、低圧減圧機構21へと流入する。
 低圧内部熱交換器31から流れ出る第1中間圧Pの液冷媒は、十分な過冷却が与えられているから、過冷却用熱交換器を経ることなく、低圧減圧機構21へと直接的に流入し、低圧減圧機構21により減圧される(r20からr21へ)。低圧減圧機構21を経た冷媒は、吸熱器E2により熱負荷から吸熱することで蒸発し、第1段圧縮機構11へと吸入される(r21からr22へ)。
On the other hand, the refrigerant flowing through the main flow path 310 increases the degree of subcooling (from r17 to r20) by dissipating heat to the refrigerant flowing through the heat absorption flow path 313, and flows into the low-pressure pressure reducing mechanism 21.
Since the liquid refrigerant at the first intermediate pressure P1 flowing out from the low-pressure internal heat exchanger 31 is sufficiently supercooled, it directly flows to the low-pressure pressure reducing mechanism 21 without passing through the heat exchanger for supercooling. It flows in and is decompressed by the low pressure decompression mechanism 21 (from r20 to r21). After passing through the low-pressure pressure reducing mechanism 21, the refrigerant absorbs heat from the heat load by the heat absorber E2, evaporates, and is sucked into the first stage compression mechanism 11 (from r21 to r22).
 気液分離器33から内部熱交換器32へと流入する液冷媒、高圧内部熱交換器32から低圧内部熱交換器31へと流入する液冷媒、および低圧内部熱交換器31から低圧減圧機構21へと流入する冷媒のそれぞれの圧力は、第3中間圧Pに相当する(r14、r17、およびr20)。そのため、冷凍サイクルにおける膨張工程は、高圧減圧機構22による高圧Pから第3中間圧Pまでの減圧と、第3中間圧Pから低圧Pまでの減圧との2段に集約される。つまり、冷凍装置1は、圧縮の段数Nよりも膨張の段数が少ない状態で、つまり、4段圧縮2段膨張サイクルにより運転される。 Liquid refrigerant flowing from the gas-liquid separator 33 to the internal heat exchanger 32, liquid refrigerant flowing from the high-pressure internal heat exchanger 32 to the low-pressure internal heat exchanger 31, and low-pressure pressure reducing mechanism 21 from the low-pressure internal heat exchanger 31 correspond to the third intermediate pressure P3 (r14, r17 and r20). Therefore, the expansion process in the refrigeration cycle is aggregated into two stages: decompression from the high pressure PH to the third intermediate pressure P3 by the high pressure decompression mechanism 22, and decompression from the third intermediate pressure P3 to the low pressure PL . . That is, the refrigeration system 1 is operated in a state where the number of stages of expansion is smaller than the number of stages N of compression, that is, in a four-stage compression and two-stage expansion cycle.
〔主な作用および効果〕
 低GWPの冷媒を使用しつつCOPを向上させるため、単段圧縮から2段圧縮へ、さらには3段圧縮、4段圧縮というように、段数Nを増加させることが有効である。
 以下に比較例を示しつつ、本実施形態の冷凍装置1の作用および効果を説明する。
 3段以上の多段圧縮を採用する場合、2段圧縮の例(例えば、上述の特許文献1)に基づいて、冷凍装置に対して圧縮段数Nと同数の減圧機構およびN-1個の気液分離器を与えることが考えられる。かかる冷凍装置は、例えば4段の場合、高圧側Hから低圧側Lに向けて、減圧機構、気液分離器、減圧機構、気液分離器、減圧機構、気液分離器、および減圧機構がこの順に配置され、各気液分離器から中間圧の気相冷媒が中間圧インジェクション流路を通じて圧縮機構の吸入部へと供給される。
 こうした比較例の冷凍装置は、図3に実線で示すように、N段圧縮、N段膨張のサイクルにより動作する。Nは、例えば「4」である。
 比較例の冷凍装置は、最も低圧側Lの気液分離器から流出した液冷媒と外気とを熱交換させる過冷却用熱交換器を備えていてもよい。その場合は、図3に一点鎖線の矢印で示すように、冷媒に過冷却が与えられる。
[Main actions and effects]
In order to improve the COP while using a refrigerant with a low GWP, it is effective to increase the number of stages N, such as from single-stage compression to two-stage compression, three-stage compression, and four-stage compression.
The operation and effect of the refrigeration system 1 of this embodiment will be described below with reference to comparative examples.
When adopting multi-stage compression of three or more stages, based on the example of two-stage compression (for example, the above-mentioned Patent Document 1), the refrigeration system is provided with the same number of pressure reduction mechanisms as the number of compression stages N and N-1 gas-liquid It is conceivable to provide a separator. For example, in the case of a four-stage refrigeration system, a decompression mechanism, a gas-liquid separator, a decompression mechanism, a gas-liquid separator, a decompression mechanism, a gas-liquid separator, and a decompression mechanism are arranged from the high pressure side H to the low pressure side L. Arranged in this order, intermediate-pressure gas-phase refrigerant is supplied from each gas-liquid separator to the suction portion of the compression mechanism through the intermediate-pressure injection passage.
Such a comparative refrigeration system operates in a cycle of N-stage compression and N-stage expansion, as indicated by the solid line in FIG. N is, for example, "4".
The refrigerating apparatus of the comparative example may include a subcooling heat exchanger that exchanges heat between the liquid refrigerant flowing out of the gas-liquid separator on the lowest pressure side L and the outside air. In that case, the refrigerant is supercooled, as indicated by the dashed-dotted arrows in FIG.
 比較例の冷凍装置は、N-1個の気液分離器を備えているから、段数Nが3以上の場合は、2以上の気液分離器を備えている。その場合は、複数の気液分離器のうちの所定の気液分離器に液冷媒を確保することが難しい。最も低圧側Lに過冷却熱交換器が設けられているとしても、冷媒が二相の状態で低圧減圧機構21および吸熱器E2に流入するのを避けるため、少なくとも、最も低圧側Lに位置する気液分離器には液冷媒を確保し、当該気液分離器から低圧減圧機構21へと液冷媒を供給することが望まれる。そのためには、N-1個の気液分離器のそれぞれの液位に基づいて圧縮機構11~14の回転数を制御する必要がある。N-1個の気液分離器のそれぞれの液位を把握するため、少なくとも2つの液位センサが必要となる。 The refrigeration system of the comparative example has N-1 gas-liquid separators, so if the number of stages N is 3 or more, it has 2 or more gas-liquid separators. In that case, it is difficult to secure liquid refrigerant in a predetermined gas-liquid separator among the plurality of gas-liquid separators. Even if the subcooling heat exchanger is provided on the lowest pressure side L, in order to prevent the refrigerant from flowing into the low pressure pressure reducing mechanism 21 and the heat absorber E2 in a two-phase state, at least it is located on the lowest pressure side L It is desirable to secure liquid refrigerant in the gas-liquid separator and supply the liquid refrigerant from the gas-liquid separator to the low-pressure pressure reducing mechanism 21 . For this purpose, it is necessary to control the rotation speeds of the compression mechanisms 11 to 14 based on the liquid levels of the N−1 gas-liquid separators. At least two level sensors are required to keep track of the level of each of the N-1 gas-liquid separators.
 比較例とは異なり、本実施形態の冷凍装置1は、段数Nを増やすにあたり、段数Nに相応の数の減圧機構および気液分離器を備えることなく、あるいは、段数Nに相応の数の内部熱交換器を備えることなく、単一の気液分離器33を高圧側Hに備えるとともに、低圧側Lには内部熱交換器32,31を備えている。つまり、本実施形態の冷凍装置1は、中間圧インジェクションの必要段数(N-1)と同数の気液分離器を備えておらず、中間圧インジェクションの必要段数(N-1)よりも少ない数の気液分離器33を備えている。
 中間圧インジェクションの必要段数(N-1)に対して、冷凍装置1が備えている気液分離器33の数が少ない分、複数の気液分離器を備えている場合に起こりうる気液分離器の相互間における冷媒の偏在の度合が軽減される。その結果、液冷媒の偏在に起因する効率低下と運転状態の不安定さを抑えつつ、圧縮段数Nの増加による効率向上の効果を担保し、また、冷凍装置1の運転状態の安定に寄与することができる。
Unlike the comparative example, the refrigerating apparatus 1 of the present embodiment does not include a number of decompression mechanisms and gas-liquid separators corresponding to the number of stages N when increasing the number of stages N, or a number of internal separators corresponding to the number of stages N A single gas-liquid separator 33 is provided on the high pressure side H and internal heat exchangers 32 and 31 are provided on the low pressure side L without providing a heat exchanger. In other words, the refrigeration system 1 of the present embodiment does not have the same number of gas-liquid separators as the required number of intermediate pressure injection stages (N-1), and the number of gas-liquid separators is less than the required intermediate pressure injection stage number (N-1). of gas-liquid separator 33.
The number of gas-liquid separators 33 provided in the refrigerating apparatus 1 is small with respect to the required number of stages (N−1) for intermediate pressure injection, so gas-liquid separation that can occur when a plurality of gas-liquid separators are provided. The degree of uneven distribution of the refrigerant between the vessels is reduced. As a result, the effect of improving efficiency by increasing the number of compression stages N is ensured while suppressing the decrease in efficiency and the instability of the operating state due to the uneven distribution of the liquid refrigerant, and the operating state of the refrigeration system 1 is stabilized. be able to.
 特に本実施形態の冷凍装置1は、気液分離器として、単一の気液分離器33のみを備えているから、複数の気液分離器のうちの一部の気液分離器において液量が尽きる状態に陥らずに、特定の気液分離器33に液冷媒が貯留されることを担保することができる。そうすると、気液分離器の液位に基づく制御が不要となり、液位センサも不要となる。液位センサを設置するとしても、その数を削減することができる。 In particular, since the refrigerating apparatus 1 of the present embodiment includes only the single gas-liquid separator 33 as a gas-liquid separator, the liquid amount in some of the plurality of gas-liquid separators is It is possible to ensure that the liquid refrigerant is stored in the specific gas-liquid separator 33 without falling into a state of exhaustion. Then, control based on the liquid level of the gas-liquid separator becomes unnecessary, and the liquid level sensor becomes unnecessary. Even if liquid level sensors are installed, the number can be reduced.
 以上より、本実施形態の冷凍装置1によれば、次のような効果を得ることができる。
(1)気液分離器として単一の気液分離器33のみを備えているため、複数の気液分離器を備えている場合とは異なり、気液分離器相互の間で液冷媒が移動することなく、特定の気液分離器33に液冷媒が貯留されることを担保することができる。そのため、気液分離器における液位に基づく制御を行う必要がない。制御の簡素化により、冷凍装置1のコストを低減することができる。
As described above, according to the refrigerating apparatus 1 of the present embodiment, the following effects can be obtained.
(1) Since only a single gas-liquid separator 33 is provided as a gas-liquid separator, unlike the case where a plurality of gas-liquid separators are provided, the liquid refrigerant moves between the gas-liquid separators Without doing so, it is possible to ensure that the liquid refrigerant is stored in a specific gas-liquid separator 33 . Therefore, there is no need to perform control based on the liquid level in the gas-liquid separator. The simplification of control can reduce the cost of the refrigeration system 1 .
(2)内部熱交換器32,31に対して高圧側Hに気液分離器33が配置されているため、気液分離器33から内部熱交換器32,31へと飽和液が流入する。そのため、冷媒に過冷却を与えることができる。そうすると、COPを向上させ、フラッシュの発生を抑えて冷凍装置1を安定して効率よく運転させることができるばかりでなく、確実に過冷却が与えられるので、内部熱交換器32,31を経た冷媒を過冷却熱交換器に流入させる必要がない。つまり、内部熱交換器32,31を経た冷媒を低圧減圧機構21に直接的に流入させればよい。
 そうすると、比較例に対して過冷却熱交換器が不要となって、冷媒回路構成の簡素化が図られるため、コストの低減、装置の小型化および軽量化に寄与することができる。
 本実施形態では、気液分離器33から液冷媒を2つの内部熱交換器32,31へと順次流入させることにより、過冷却度を十分に得ることができる。そのため、効率向上および運転安定化の効果が大きいことに加え、過冷却度を増大させるために能力の大きな過冷却熱交換器を追加する必要がないから、コストの低減、装置の小型化および軽量化の効果も大きい。
(2) Since the gas-liquid separator 33 is arranged on the high pressure side H with respect to the internal heat exchangers 32 and 31 , the saturated liquid flows from the gas-liquid separator 33 into the internal heat exchangers 32 and 31 . Therefore, supercooling can be applied to the refrigerant. As a result, the COP can be improved, the occurrence of flash can be suppressed, and the refrigeration system 1 can be operated stably and efficiently. does not need to flow into the subcooling heat exchanger. In other words, the refrigerant that has passed through the internal heat exchangers 32 and 31 should be allowed to flow directly into the low-pressure pressure reducing mechanism 21 .
Then, the subcooling heat exchanger is not required as compared with the comparative example, and the refrigerant circuit configuration can be simplified, which can contribute to cost reduction, size reduction, and weight reduction of the device.
In the present embodiment, a sufficient degree of supercooling can be obtained by sequentially flowing the liquid refrigerant from the gas-liquid separator 33 into the two internal heat exchangers 32 and 31 . Therefore, in addition to being highly effective in improving efficiency and stabilizing operation, there is no need to add a supercooling heat exchanger with a large capacity in order to increase the degree of supercooling, which reduces costs and reduces the size and weight of the device. The effect of conversion is also great.
(3)高圧内部熱交換器32および/または低圧内部熱交換器31に減圧機構としての膨張弁が備えられることによれば、膨張弁の開度の調整により、図2に示すが如く、二相冷媒による中間圧インジェクションを行うことが可能となる。例えば、高圧内部熱交換器32に減圧機構321としての膨張弁が備えられる場合は、膨張弁の開度調整により、第2中間圧インジェクション流路42を通じて、二相冷媒による第2中間圧Pのインジェクション(r16からr6へ)を第3段圧縮機構13に対して行うことが可能となる。
 あるいは、低圧内部熱交換器31に減圧機構311としての膨張弁が備えられる場合は、膨張弁の開度調整により、二相冷媒による第1中間圧Pのインジェクション(r19からr3へ)を第2段圧縮機構12に対して行うことが可能となる。
 二相冷媒のインジェクションにより、圧縮機構への冷媒の吸入温度が下がるため、吐出温度を許容限度に抑えることができる。
(3) If the high-pressure internal heat exchanger 32 and/or the low-pressure internal heat exchanger 31 is provided with an expansion valve as a decompression mechanism, by adjusting the degree of opening of the expansion valve, as shown in FIG. It is possible to perform intermediate pressure injection with a phase refrigerant. For example, when the high-pressure internal heat exchanger 32 is provided with an expansion valve as the decompression mechanism 321, the second intermediate pressure P2 by the two-phase refrigerant is passed through the second intermediate pressure injection passage 42 by adjusting the opening degree of the expansion valve. injection (from r16 to r6) to the third stage compression mechanism 13 becomes possible.
Alternatively, if the low-pressure internal heat exchanger 31 is provided with an expansion valve as the decompression mechanism 311, the injection of the first intermediate pressure P1 (from r19 to r3) by the two-phase refrigerant is controlled by adjusting the opening of the expansion valve. It becomes possible to perform this for the two-stage compression mechanism 12 .
By injecting the two-phase refrigerant, the refrigerant suction temperature into the compression mechanism is lowered, so the discharge temperature can be suppressed to the allowable limit.
(4)一般に、気液分離器には、冷媒を低温に保つために断熱材が設けられる。内部熱交換器31,32に対して高圧側Hに気液分離器33が配置されることによれば、低圧側Lに気液分離器が配置される場合に比べ、気液分離器における圧力飽和温度が高くなるため、気液分離器33と外気温との温度差が小さい。したがって、気液分離器33に設けられる断熱材の厚さを薄くすることができるので、コストの低減、装置の小型化および軽量化に寄与することができる。 (4) In general, a gas-liquid separator is provided with a heat insulating material to keep the refrigerant at a low temperature. By arranging the gas-liquid separator 33 on the high pressure side H with respect to the internal heat exchangers 31 and 32, the pressure in the gas-liquid separator is Since the saturation temperature is high, the temperature difference between the gas-liquid separator 33 and the outside air temperature is small. Therefore, the thickness of the heat insulating material provided in the gas-liquid separator 33 can be reduced, which contributes to cost reduction, miniaturization and weight reduction of the device.
 例えば、冷凍装置1の定格条件において、図1の如く、第3中間圧Pに対応する単一の気液分離器33を備え、第2中間圧Pおよび第1中間圧Pにそれぞれ対応する2つの内部熱交換器32,31を備える場合には、気液分離器33の液出口の温度は20°であり、この場合に最も外気温との温度差が小さい。液出口の温度は、サイクル計算による。以下も同様である。
 図示を省略するが、第2中間圧Pに対応する単一の気液分離器を備え、第3中間圧Pおよび第1中間圧Pにそれぞれ対応する2つの内部熱交換器を備える場合には、気液分離器の液出口の温度は2°である。
 さらに、第1中間圧Pに対応する単一の気液分離器を備え、第3中間圧Pおよび第2中間圧Pにそれぞれ対応する2つの内部熱交換器を備える場合には、気液分離器の液出口の温度は-12°である。
For example, under rated conditions of the refrigeration system 1, as shown in FIG . When two corresponding internal heat exchangers 32 and 31 are provided, the temperature at the liquid outlet of the gas-liquid separator 33 is 20°, which is the smallest temperature difference from the outside air temperature. The liquid outlet temperature is according to cycle calculations. The same applies to the following.
Although not shown, it has a single gas-liquid separator corresponding to the second intermediate pressure P2 , and two internal heat exchangers corresponding to the third intermediate pressure P3 and the first intermediate pressure P1 respectively. In the case the temperature at the liquid outlet of the gas-liquid separator is 2°.
Furthermore, if we have a single gas-liquid separator corresponding to the first intermediate pressure P1 and two internal heat exchangers corresponding to the third intermediate pressure P3 and the second intermediate pressure P2 respectively, The temperature at the liquid outlet of the gas-liquid separator is -12°.
 気液分離器の位置が高圧側であるほど、圧力飽和温度が高いため気液分離器と外気との温度差が小さいことは、比較例に係る図3のモリエール図によっても説明することができる。図3から理解されるように、高圧の気液分離器(r12)の圧力飽和温度をT1、中圧の気液分離器(r15)の圧力飽和温度をT2、低圧の気液分離器(r18)の圧力飽和温度をT3とすると、T1>T2>T3であることが明らかである。圧力飽和温度が高いほど、気液分離器と外気との温度差が小さい。 The higher the pressure saturation temperature of the gas-liquid separator is, the smaller the temperature difference between the gas-liquid separator and the outside air can be explained by the Moliere diagram of FIG. . As can be seen from FIG. 3, the pressure saturation temperature of the high-pressure gas-liquid separator (r12) is T1, the pressure saturation temperature of the medium-pressure gas-liquid separator (r15) is T2, and the low-pressure gas-liquid separator (r18) ) is T3, it is clear that T1>T2>T3. The higher the pressure saturation temperature, the smaller the temperature difference between the gas-liquid separator and the outside air.
 以上で説明したように、本実施形態の冷凍装置1によれば、2種類の中間圧インジェクション手段としての1つ以上の気液分離器33および1つ以上の内部熱交換器31,32を組み合わせて、圧縮の段数N(3以上)に相応の中間圧インジェクションの必要段数(N-1)を満足するとともに、内部熱交換器31,32に対して高圧側Hに気液分離器33を配置することにより、例えばCOのように低GWPの冷媒を使用しつつCOPを向上させ、かつ吐出温度を許容限度以下に維持しながら冷凍装置1を安定して運転させることができる。 As described above, according to the refrigeration system 1 of the present embodiment, one or more gas-liquid separators 33 and one or more internal heat exchangers 31 and 32 as two types of intermediate pressure injection means are combined. to satisfy the required number of intermediate pressure injection stages (N-1) corresponding to the number of compression stages N (3 or more), and the gas-liquid separator 33 is arranged on the high pressure side H of the internal heat exchangers 31 and 32. As a result, the COP can be improved while using a low GWP refrigerant such as CO 2 , and the refrigeration system 1 can be stably operated while maintaining the discharge temperature below the allowable limit.
〔変形例〕
 冷凍装置1は、必ずしも高圧内部熱交換器32および低圧内部熱交換器31を備えている必要はなく、段数Nに応じて、単一の内部熱交換器のみを備えていたり、あるいは3つ以上の内部熱交換器を備えていたりしてもよい。そうした場合も、上記実施形態により得られる作用効果と同様の作用効果を得ることができる。
[Modification]
The refrigerating apparatus 1 does not necessarily have the high-pressure internal heat exchanger 32 and the low-pressure internal heat exchanger 31, and may have only a single internal heat exchanger, or may have three or more internal heat exchangers, depending on the number of stages N. of internal heat exchangers. Even in such a case, it is possible to obtain the same effects as those obtained by the above-described embodiment.
 図4に示す冷凍装置1-2は、N段(4段)の圧縮機構11~14を備え、N-1個(3個)の中間圧インジェクション手段として、2つの気液分離器33,32-2と、単一の内部熱交換器31とを備えている。図5は、冷凍装置1-2のモリエール線図である。
 冷凍装置1-2は、2つの気液分離器33,32-2の間に位置する減圧機構22を含め、減圧部20を構成する3つの減圧機構21~23を備えている。そのため、4段圧縮3段膨張のサイクルにより運転される。
The refrigerating apparatus 1-2 shown in FIG. 4 includes N-stage (four-stage) compression mechanisms 11 to 14, and two gas- liquid separators 33 and 32 as N−1 (three) intermediate pressure injection means. -2 and a single internal heat exchanger 31. FIG. 5 is a Moliere diagram of the refrigerator 1-2.
The refrigerator 1-2 has three decompression mechanisms 21 to 23 forming a decompression unit 20, including a decompression mechanism 22 positioned between two gas-liquid separators 33 and 32-2. Therefore, it is operated by a cycle of 4-stage compression and 3-stage expansion.
 冷凍装置1-2も、上記実施形態の冷凍装置1と同様に、中間圧インジェクションの必要段数(N-1)に対して少ない数である2つの気液分離器33,32-2を備えていることにより、気液分離器33,32-2の間の液冷媒の偏在の度合が軽減される。その結果、サイクル効率低下と運転状態の不安定さを抑えつつ、圧縮段数Nの増加による効率向上の効果を担保することができ、また、冷凍装置1-2の運転状態の安定に寄与することができる。 Like the refrigerating device 1 of the above embodiment, the refrigerating device 1-2 also includes two gas-liquid separators 33 and 32-2, which are smaller than the required number of stages (N-1) for intermediate pressure injection. As a result, the degree of uneven distribution of the liquid refrigerant between the gas-liquid separators 33, 32-2 is reduced. As a result, it is possible to secure the effect of improving the efficiency by increasing the number of compression stages N while suppressing the deterioration of the cycle efficiency and the instability of the operating state, and contribute to the stabilization of the operating state of the refrigerating apparatus 1-2. can be done.
 加えて、内部熱交換器31に対して高圧側Hに気液分離器33,32-2が配置されているため、気液分離器32-2から内部熱交換器31へと飽和液が流入するので、冷媒に過冷却を与えることができる(図5におけるr17からr20へ)。過冷却により安定して効率よく運転させることができる上、過冷却を得るために過冷却熱交換器を追加する必要がないので、コストの低減、装置の小型化および軽量化に寄与することができる。 In addition, since the gas-liquid separators 33 and 32-2 are arranged on the high pressure side H of the internal heat exchanger 31, the saturated liquid flows into the internal heat exchanger 31 from the gas-liquid separator 32-2. Therefore, the refrigerant can be subcooled (from r17 to r20 in FIG. 5). It is possible to operate stably and efficiently by supercooling, and there is no need to add a supercooling heat exchanger to obtain supercooling. can.
 その他、内部熱交換器31に減圧機構311として備えられる膨張弁の開度の調整により、二相冷媒による第1中間圧Pのインジェクションを行うことが可能となる(r19からr3へ)。そうすると、第2段圧縮機構12への冷媒の吸入温度が低下するため、圧縮部10からの冷媒の吐出温度を許容限度に抑えることができる。
 さらに、内部熱交換器31に対して高圧側Hに気液分離器33,32-2が配置されることによれば、内部熱交換器31に対して低圧側Lに気液分離器33,32-2が配置される場合に対し、断熱材の厚さを低減できるため、装置の小型化および軽量化に寄与できる。
In addition, by adjusting the degree of opening of the expansion valve provided as the decompression mechanism 311 in the internal heat exchanger 31, it is possible to inject the two-phase refrigerant at the first intermediate pressure P1 (from r19 to r3). As a result, the temperature of the refrigerant sucked into the second-stage compression mechanism 12 is lowered, so that the temperature of the refrigerant discharged from the compression section 10 can be suppressed to the allowable limit.
Furthermore, by arranging the gas-liquid separators 33, 32-2 on the high pressure side H of the internal heat exchanger 31, the gas-liquid separators 33, 32-2 on the low pressure side L of the internal heat exchanger 31, Compared to the case where 32-2 is arranged, the thickness of the heat insulating material can be reduced, which contributes to the miniaturization and weight reduction of the device.
 上記以外にも、上記実施形態で挙げた構成を取捨選択したり、他の構成に適宜変更したりすることが可能である。 In addition to the above, it is possible to select the configurations mentioned in the above embodiments or change them to other configurations as appropriate.
(付記)
 以上で説明した冷凍装置は、以下のように把握される。
〔1〕冷凍サイクルにより冷媒を循環させる冷凍装置1,1-2は、直列に接続されてそれぞれ冷媒を圧縮する3段以上の圧縮機構11~14を含む圧縮部10と、圧縮部10から吐出された冷媒を外気へと放熱させる第1熱交換器(E1)と、相対的に高圧側の高圧減圧機構22と、相対的に低圧側の低圧減圧機構21とを含み、第1熱交換器E1を経た冷媒の圧力を高圧減圧機構22および低圧減圧機構21により減少させる減圧部20と、減圧部20を経た冷媒を熱負荷から吸熱させる第2熱交換器(E2)と、高圧減圧機構22と低圧減圧機構21との間に与えられ、第1熱交換器(E1)に設定される高圧Pと、第2熱交換器(E2)に設定される低圧Pとの間の中間圧P,P,Pの冷媒を圧縮機構と圧縮機構との間に供給する複数の中間圧インジェクション流路41~43と、複数の中間圧インジェクション流路41~43のうち相対的に高圧側Hの高圧中間圧インジェクション流路(43、または43,42)に気相の冷媒を供給する気液分離器33(または33,32-2)と、気液分離器33から供給される液相の冷媒である液冷媒と、液冷媒の一部を減圧させてなる二相冷媒とを熱交換させることで液冷媒から吸熱させた冷媒を、高圧中間圧インジェクション流路(43、または43,42)に対して低圧側Lの中間圧インジェクション流路42,41(または41)に供給する内部熱交換器32,31(または31)と、を備える。
〔2〕冷凍装置1には、気液分離器33は、1つだけ備えられ、内部熱交換器32,31は、気液分離器33と低圧減圧機構21との間に1つ以上が備えられる。
〔3〕冷凍装置1は、最も高圧側Hに位置する気液分離器33であって高圧減圧機構22から直接的に冷媒が供給される最高圧気液分離器(33)を備える。
〔4〕冷凍装置1,1-2は、最も低圧側Lに位置する内部熱交換器31であって低圧減圧機構21へと直接的に冷媒を流入させる最低圧内部熱交換器(31)を備える。
〔5〕内部熱交換器31,32は、液冷媒の一部の圧力を減少させて膨張させる膨張弁(311,321)を含む。
〔6〕冷凍装置1は、2つ以上の内部熱交換器31,32を備え、相対的に高圧側Hに位置する内部熱交換器32の能力は、相対的に低圧側に位置する内部熱交換器31の能力よりも大きい。
〔7〕冷媒は、二酸化炭素を少なくとも一部に含む。
(Appendix)
The refrigeration system described above is understood as follows.
[1] The refrigerating devices 1 and 1-2 that circulate the refrigerant by a refrigerating cycle include a compression section 10 that includes three or more stages of compression mechanisms 11 to 14 that are connected in series and each compresses the refrigerant, and discharge from the compression section 10 A first heat exchanger (E1) for releasing the heat of the discharged refrigerant to the outside air, a relatively high pressure side high pressure pressure reducing mechanism 22, and a relatively low pressure side low pressure pressure reducing mechanism 21, the first heat exchanger A decompression unit 20 that reduces the pressure of the refrigerant that has passed through E1 by a high-pressure decompression mechanism 22 and a low-pressure decompression mechanism 21, a second heat exchanger (E2) that causes the refrigerant that has passed through the decompression unit 20 to absorb heat from a heat load, and a high-pressure decompression mechanism 22. and the low-pressure pressure reducing mechanism 21, and the intermediate pressure between the high pressure PH set in the first heat exchanger (E1) and the low pressure PL set in the second heat exchanger (E2) A plurality of intermediate pressure injection passages 41 to 43 for supplying the refrigerants P 1 , P 2 and P 3 between the compression mechanisms, and a relatively high pressure among the plurality of intermediate pressure injection passages 41 to 43 A gas-liquid separator 33 (or 33, 32-2) that supplies gas-phase refrigerant to the high-pressure intermediate-pressure injection flow path (43 or 43, 42) on the side H, and the liquid supplied from the gas-liquid separator 33 A liquid refrigerant, which is a phase refrigerant, and a two-phase refrigerant, which is a part of the liquid refrigerant whose pressure is reduced, are heat-exchanged to absorb heat from the liquid refrigerant. 42) are provided with internal heat exchangers 32, 31 (or 31) that supply to the intermediate pressure injection passages 42, 41 (or 41) on the low pressure side L.
[2] Only one gas-liquid separator 33 is provided in the refrigeration system 1, and one or more internal heat exchangers 32 and 31 are provided between the gas-liquid separator 33 and the low-pressure pressure reducing mechanism 21. be done.
[3] The refrigerating apparatus 1 is provided with a highest pressure gas-liquid separator (33), which is the gas-liquid separator 33 located on the highest pressure side H and to which the refrigerant is directly supplied from the high-pressure decompression mechanism 22.
[4] The refrigerating apparatus 1, 1-2 includes the lowest pressure internal heat exchanger (31), which is the internal heat exchanger 31 located on the lowest pressure side L and causes the refrigerant to flow directly into the low pressure decompression mechanism 21. Prepare.
[5] The internal heat exchangers 31, 32 include expansion valves (311, 321) that reduce the pressure of a portion of the liquid refrigerant to expand it.
[6] The refrigerating apparatus 1 includes two or more internal heat exchangers 31 and 32, and the capacity of the internal heat exchanger 32 located on the relatively high pressure side H is determined by the capacity of the internal heat exchanger 32 located on the relatively low pressure side. greater than the capacity of the exchanger 31.
[7] The refrigerant contains at least a portion of carbon dioxide.
1,1-2   冷凍装置
10   圧縮部
11   1段圧縮機構
12   2段圧縮機構
13   3段圧縮機構
14   4段圧縮機構
15   制御装置
16   中間冷却熱交換器
20   減圧部
21   低圧減圧機構
22   高圧減圧機構
21~23   減圧機構
31   低圧内部熱交換器(最低圧内部熱交換器)
32   高圧内部熱交換器
32-2 気液分離器
33   気液分離器(最高圧気液分離器)
33A  貯留タンク
33B  気相領域
41   第1中間圧インジェクション流路
42   第2中間圧インジェクション流路
43   第3中間圧インジェクション流路(高圧中間圧インジェクション流路)
101  第1電動圧縮機
101A ハウジング
101B 電動機
102  第2電動圧縮機
102A ハウジング
102B 電動機
310  主流路
311  減圧機構
312  分岐流路
313  吸熱流路
320  主流路
321  減圧機構
322  分岐流路
323  吸熱流路
E1   放熱器(第1熱交換器)
E2   吸熱器(第2熱交換器)
H    高圧側
L    低圧側
N    段数
,P,P   中間圧
   臨界圧力
   高圧
   低圧
n1,n2,n3,n4   段
 
1, 1-2 Refrigerating device 10 compression unit 11 first-stage compression mechanism 12 two-stage compression mechanism 13 three-stage compression mechanism 14 four-stage compression mechanism 15 controller 16 intermediate cooling heat exchanger 20 decompression unit 21 low-pressure decompression mechanism 22 high-pressure decompression mechanism 21 to 23 decompression mechanism 31 low pressure internal heat exchanger (minimum pressure internal heat exchanger)
32 high-pressure internal heat exchanger 32-2 gas-liquid separator 33 gas-liquid separator (highest pressure gas-liquid separator)
33A storage tank 33B gas phase region 41 first intermediate pressure injection channel 42 second intermediate pressure injection channel 43 third intermediate pressure injection channel (high pressure intermediate pressure injection channel)
101 First electric compressor 101A Housing 101B Electric motor 102 Second electric compressor 102A Housing 102B Electric motor 310 Main channel 311 Pressure reducing mechanism 312 Branch channel 313 Heat absorption channel 320 Main channel 321 Pressure reducing mechanism 322 Branch channel 323 Heat absorption channel E1 Heat dissipation vessel (first heat exchanger)
E2 heat absorber (second heat exchanger)
H High pressure side L Low pressure side N Number of stages P 1 , P 2 , P 3 Intermediate pressure P C Critical pressure PH High pressure P L Low pressure n1, n2, n3, n4 Stages

Claims (7)

  1.  冷凍サイクルにより冷媒を循環させる冷凍装置であって、
     直列に接続されてそれぞれ前記冷媒を圧縮する3段以上の圧縮機構を含む圧縮部と、
     前記圧縮部から吐出された前記冷媒を外気へと放熱させる第1熱交換器と、
     相対的に高圧側の高圧減圧機構と、相対的に低圧側の低圧減圧機構とを含み、前記第1熱交換器を経た前記冷媒の圧力を前記高圧減圧機構および前記低圧減圧機構により減少させる減圧部と、
     前記減圧部を経た前記冷媒を熱負荷から吸熱させる第2熱交換器と、
     前記高圧減圧機構と前記低圧減圧機構との間に与えられ、前記第1熱交換器に設定される高圧と、前記第2熱交換器に設定される低圧との間の中間圧の前記冷媒を前記圧縮機構と前記圧縮機構との間に供給する複数の中間圧インジェクション流路と、
     前記複数の中間圧インジェクション流路のうち相対的に高圧側の高圧中間圧インジェクション流路に気相の前記冷媒を供給する気液分離器と、
     前記気液分離器から供給される液相の前記冷媒である液冷媒と、前記液冷媒の一部を減圧させてなる二相冷媒とを熱交換させることで前記液冷媒から吸熱させた前記冷媒を、前記高圧中間圧インジェクション流路に対して低圧側の前記中間圧インジェクション流路に供給する内部熱交換器と、を備える、冷凍装置。
    A refrigeration device that circulates a refrigerant by a refrigeration cycle,
    a compression unit including three or more stages of compression mechanisms that are connected in series and each compresses the refrigerant;
    a first heat exchanger that releases the heat of the refrigerant discharged from the compression unit to the outside air;
    A pressure reducing mechanism including a high pressure pressure reducing mechanism on a relatively high pressure side and a low pressure pressure reducing mechanism on a relatively low pressure side, wherein the pressure of the refrigerant that has passed through the first heat exchanger is reduced by the high pressure pressure reducing mechanism and the low pressure pressure reducing mechanism. Department and
    a second heat exchanger that causes the refrigerant that has passed through the decompression unit to absorb heat from a heat load;
    The refrigerant at an intermediate pressure between the high pressure set in the first heat exchanger and the low pressure set in the second heat exchanger is provided between the high pressure pressure reduction mechanism and the low pressure pressure reduction mechanism. a plurality of intermediate pressure injection flow paths supplied between the compression mechanism and the compression mechanism;
    a gas-liquid separator that supplies the gas-phase refrigerant to a relatively high-pressure-side high-pressure intermediate-pressure injection channel among the plurality of intermediate-pressure injection channels;
    The refrigerant absorbed heat from the liquid refrigerant by exchanging heat between the liquid refrigerant, which is the liquid-phase refrigerant supplied from the gas-liquid separator, and the two-phase refrigerant obtained by decompressing a part of the liquid refrigerant. to the intermediate pressure injection channel on the low pressure side with respect to the high pressure intermediate pressure injection channel.
  2.  前記気液分離器は、1つだけ備えられ、
     前記内部熱交換器は、前記気液分離器と前記低圧減圧機構との間に1つ以上が備えられる、
    請求項1に記載の冷凍装置。
    Only one gas-liquid separator is provided,
    One or more internal heat exchangers are provided between the gas-liquid separator and the low-pressure pressure reducing mechanism,
    Refrigeration equipment according to claim 1 .
  3.  最も高圧側に位置する前記気液分離器であって、前記高圧減圧機構から直接的に前記冷媒が供給される最高圧気液分離器を備える、
    請求項1または2に記載の冷凍装置。
    The gas-liquid separator located on the highest pressure side, comprising the highest pressure gas-liquid separator to which the refrigerant is directly supplied from the high pressure decompression mechanism,
    3. The refrigeration system according to claim 1 or 2.
  4.  最も低圧側に位置する前記内部熱交換器であって、前記低圧減圧機構へと直接的に前記冷媒を流入させる最低圧内部熱交換器を備える、
    請求項1または2に記載の冷凍装置。
    The internal heat exchanger located on the lowest pressure side, comprising the lowest pressure internal heat exchanger that allows the refrigerant to flow directly into the low pressure decompression mechanism,
    3. The refrigeration system according to claim 1 or 2.
  5.  前記内部熱交換器は、
     前記液冷媒の一部の圧力を減少させて膨張させる膨張弁を含む、
    請求項1から4のいずれか一項に記載の冷凍装置。
    The internal heat exchanger is
    including an expansion valve that reduces the pressure of a portion of the liquid refrigerant to expand it,
    A refrigeration system according to any one of claims 1 to 4.
  6.  2つ以上の前記内部熱交換器を備え、
     相対的に高圧側に位置する前記内部熱交換器の能力は、相対的に低圧側に位置する前記内部熱交換器の能力よりも大きい、
    請求項1から5のいずれか一項に記載の冷凍装置。
    comprising two or more of the internal heat exchangers;
    The capacity of the internal heat exchanger located on the relatively high pressure side is greater than the capacity of the internal heat exchanger located on the relatively low pressure side.
    A refrigeration system according to any one of claims 1 to 5.
  7.  前記冷媒は、二酸化炭素を少なくとも一部に含む、
    請求項1から6のいずれか一項に記載の冷凍装置。
     
    The refrigerant contains at least a portion of carbon dioxide,
    A refrigeration apparatus according to any one of claims 1 to 6.
PCT/JP2022/004822 2021-05-27 2022-02-08 Multi-stage compression refrigeration apparatus WO2022249565A1 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007046332A1 (en) * 2005-10-17 2007-04-26 Mayekawa Mfg. Co., Ltd. Co2 refrigerator
US20110113804A1 (en) * 2009-11-18 2011-05-19 Simwon Chin Heat pump
JP2012154616A (en) * 2011-01-21 2012-08-16 Lg Electronics Inc Air conditioner
JP2013024436A (en) * 2011-07-15 2013-02-04 Daikin Industries Ltd Refrigeration device
US20130055754A1 (en) * 2011-09-06 2013-03-07 Beomchan Kim Air conditioner
JP2017044420A (en) 2015-08-27 2017-03-02 三菱重工業株式会社 Two-stage compression freezing system

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007046332A1 (en) * 2005-10-17 2007-04-26 Mayekawa Mfg. Co., Ltd. Co2 refrigerator
US20110113804A1 (en) * 2009-11-18 2011-05-19 Simwon Chin Heat pump
JP2012154616A (en) * 2011-01-21 2012-08-16 Lg Electronics Inc Air conditioner
JP2013024436A (en) * 2011-07-15 2013-02-04 Daikin Industries Ltd Refrigeration device
US20130055754A1 (en) * 2011-09-06 2013-03-07 Beomchan Kim Air conditioner
JP2017044420A (en) 2015-08-27 2017-03-02 三菱重工業株式会社 Two-stage compression freezing system

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