EP2910872B1 - Freezing device - Google Patents

Freezing device Download PDF

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Publication number
EP2910872B1
EP2910872B1 EP12886969.0A EP12886969A EP2910872B1 EP 2910872 B1 EP2910872 B1 EP 2910872B1 EP 12886969 A EP12886969 A EP 12886969A EP 2910872 B1 EP2910872 B1 EP 2910872B1
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EP
European Patent Office
Prior art keywords
low
temperature side
pressure
compressor
refrigerant
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP12886969.0A
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German (de)
French (fr)
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EP2910872A1 (en
EP2910872A4 (en
Inventor
Takeshi Sugimoto
So Nomoto
Tomotaka Ishikawa
Takashi Ikeda
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Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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Publication of EP2910872A1 publication Critical patent/EP2910872A1/en
Publication of EP2910872A4 publication Critical patent/EP2910872A4/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
    • F25B43/00Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat
    • F25B43/006Accumulators
    • 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
    • F25B45/00Arrangements for charging or discharging refrigerant
    • 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
    • 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
    • F25B7/00Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit
    • 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
    • F25B2400/13Economisers
    • 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
    • F25B2500/26Problems to be solved characterised by the startup of the refrigeration cycle
    • 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
    • F25B2600/01Timing
    • 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
    • F25B2600/02Compressor control
    • F25B2600/025Compressor control by controlling speed
    • F25B2600/0251Compressor control by controlling speed with on-off operation
    • 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
    • F25B2600/23Time delays
    • 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
    • F25B2600/2523Receiver 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
    • F25B2700/19Pressures
    • F25B2700/193Pressures of the compressor
    • F25B2700/1931Discharge pressures
    • 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
    • F25B2700/19Pressures
    • F25B2700/193Pressures of the compressor
    • F25B2700/1933Suction pressures
    • 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
    • F25B9/00Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/008Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide

Definitions

  • This invention relates to a refrigeration apparatus including circulation circuits (refrigeration cycles) that circulate a refrigerant.
  • US 2009/0126389 discloses a refrigeration apparatus having a plurality of expansion tanks which are connected to the suction side of a low-temperature compressor by means of a check valve and a capillary tube in parallel.
  • US 2010/0251750 discloses an economized refrigerant system with flow control.
  • a refrigeration apparatus which operates a binary refrigeration cycle with a high-temperature side circulation circuit (high-temperature side refrigeration cycle) and a low-temperature side circulation circuit (low-temperature side refrigeration cycle) cascade-connected via a cascade capacitor.
  • An existing refrigeration apparatus which, when a compressor of a low-temperature side circulation circuit is stopped, operates a compressor of a high-temperature side circulation circuit to cool a refrigerant in the low-temperature side circulation circuit to thereby suppress an increase in pressure of the low-temperature side circulation circuit (see Japanese Unexamined Patent Application Publication No. 2004-190917 (paragraphs [0008]-[0023] and Fig. 1 ).
  • the compressor of the high-temperature side circulation circuit is operated with the compressor of the low-temperature side circulation circuit stopped. Further, when the compressor of the low-temperature side circulation circuit in the stopped (thermo-off) state is restarted, the compressor of the low-temperature side circulation circuit is restarted after the lapse of a predetermined time from the start of the compressor of the high-temperature side circulation circuit.
  • the existing refrigeration apparatus however, has an issue in that the compressor of the high-temperature side circulation circuit needs to be uselessly operated despite the state in which a cooling operation is not performed with the compressor of the low-temperature side circulation circuit stopped.
  • the compressor of the high-temperature side circulation circuit needs to be operated for an extra time of approximately 30 minutes to approximately 40 minutes in the defrosting operation for the evaporator of the low-temperature side circulation circuit in order to keep the design pressure of the low-temperature side circulation circuit no higher than approximately 3 MPa to approximately 4 MPa.
  • the defrosting operation takes place about four times to five times a day.
  • the compressor of the high-temperature side circulation circuit is not operated when the compressor of the low-temperature side circulation circuit is stopped, and if the compressor of the low-temperature side circulation circuit is stopped for a long time, the refrigerant in the low-temperature side circulation circuit is warmed to about outside air temperature, resulting in an increase in pressure.
  • the structure of members forming the low-temperature side circulation circuit needs to be strong.
  • refrigerant pipes need to be thick. This leads to an issue of an increase in manufacturing cost.
  • the pressure of the refrigerant in the low-temperature side circulation circuit is increased to exceed the design pressure, the refrigerant may be discharged from a safety valve. In this case, the low-temperature side circulation circuit needs to be refilled with a refrigerant.
  • This invention has been made to solve the above-described issues, and obtains a refrigeration apparatus capable of suppressing the increase in pressure of the refrigerant in the low-temperature side circulation circuit when the compressor of the low-temperature side circulation circuit is stopped.
  • This invention also obtains a refrigeration apparatus capable of suppressing the increase in pressure of the refrigerant in the low-temperature side circulation circuit without operating the compressor of the high-temperature side circulation circuit when the compressor of the low-temperature side circulation circuit is stopped or restarted.
  • This invention further obtains a refrigeration apparatus capable of reducing the design pressure of the low-temperature side circulation circuit.
  • This invention includes the expansion tanks connected to the pipe between the second evaporator and the second compressor via the opening and closing valve, and therefore is capable of suppressing the increase in pressure of the refrigerant in the low-temperature side circulation circuit without operating the compressor of the high-temperature side refrigerant circuit.
  • Fig. 1 is a refrigerant circuit diagram of a refrigeration apparatus in Embodiment 1 of this invention.
  • the refrigeration apparatus includes a high-temperature side circulation circuit A and a low-temperature side circulation circuit (load side circuit) B.
  • the high-temperature side circulation circuit A and the low-temperature side circulation circuit B are cascade-connected via a cascade capacitor 8.
  • the refrigeration apparatus operates a binary refrigeration cycle by circulating a refrigerant in each of the high-temperature side circulation circuit A and the low-temperature side circulation circuit B.
  • the levels and so forth of the temperature, the pressure, and so forth of configurations referred to as the low-temperature side and the high-temperature side are not particularly determined by the relationship thereof with respective absolute values, but are relatively determined by the state, the operation, and so forth of the refrigeration apparatus.
  • refrigeration apparatuses include a refrigeration apparatus including three or more refrigeration cycles (a multiple refrigeration apparatus).
  • the high-temperature side circulation circuit A includes a high-temperature side compressor 1, a high-temperature side condenser 2, a high-temperature side expansion valve 3, and a high-temperature side evaporator 4.
  • the high-temperature side compressor 1, the high-temperature side condenser 2, the high-temperature side expansion valve 3, and the high-temperature side evaporator 4 are connected in series by refrigerant pipes.
  • the high-temperature side compressor 1, the high-temperature side condenser 2, the high-temperature side expansion valve 3, and the high-temperature side evaporator 4 are stored in a later-described outdoor unit 14.
  • a refrigerant having a relatively small global warming potential (e.g., an R410A, R134a, R32, or HFO refrigerant) is used as the refrigerant circulated through the high-temperature side circulation circuit A.
  • GWP global warming potential
  • the high-temperature side compressor 1 suctions the refrigerant flowing through the high-temperature side circulation circuit A.
  • the high-temperature side compressor 1 compresses the suctioned refrigerant and discharges the refrigerant at a high temperature and high pressure.
  • the high-temperature side condenser 2 exchanges heat between air and the refrigerant discharged from the high-temperature side compressor 1.
  • the high-temperature side expansion valve 3 expands the refrigerant flowing from the high-temperature side condenser 2 by reducing the pressure of the refrigerant.
  • the high-temperature side evaporator 4 exchanges heat between the refrigerant reduced in pressure by the high-temperature side expansion valve 3 and the refrigerant flowing through a low-temperature side condenser 7 of the low-temperature side circulation circuit B.
  • the high-temperature side evaporator 4 and the low-temperature side condenser 7 form the cascade capacitor 8.
  • the cascade capacitor 8 is formed of a plate-type heat exchanger, for example.
  • the cascade capacitor 8 is not limited to the plate-type heat exchanger, and may be a shell-and-tube-type heat exchanger or a double pipe-type heat exchanger.
  • the high-temperature side compressor 1 corresponds to "a first compressor" of the present invention.
  • the high-temperature side condenser 2 corresponds to "a first condenser" of the present invention.
  • the high-temperature side expansion valve 3 corresponds to "a first expansion device" of the present invention.
  • the high-temperature side evaporator 4 corresponds to "a first evaporator" of the present invention.
  • the low-temperature side circulation circuit B includes a low-temperature side compressor 5, an auxiliary capacitor 6, the low-temperature side condenser 7, a liquid receiver 9, a low-temperature side flow control valve 10, a low-temperature side first solenoid valve 11, a low-temperature side evaporator 12, a low-temperature side high pressure sensor 27, and a low-temperature side low pressure sensor 28.
  • the low-temperature side compressor 5, the auxiliary capacitor 6, the low-temperature side condenser 7, the liquid receiver 9, the low-temperature side first solenoid valve 11, the low-temperature side flow control valve 10, and the low-temperature side evaporator 12 are connected in series by refrigerant pipes.
  • a pipe between the low-temperature side condenser 7 and the low-temperature side compressor 5 is connected to an expansion tank 18a, an expansion tank 18b, and an expansion tank 18c via a low-temperature side second solenoid valve 17.
  • the low-temperature side high pressure sensor 27 detects the pressure on a discharge side of the low-temperature side compressor 5.
  • the low-temperature side low pressure sensor 28 detects the pressure on a suction side of the low-temperature side compressor 5.
  • the low-temperature side compressor 5, the auxiliary capacitor 6, the low-temperature side condenser 7, the liquid receiver 9, the low-temperature side high pressure sensor 27, and the low-temperature side low pressure sensor 28 are stored in the later-described outdoor unit 14.
  • the low-temperature side first solenoid valve 11, the low-temperature side flow control valve 10, and the low-temperature side evaporator 12 are stored in a cooling unit 13.
  • the cooling unit 13 is used as a refrigerator-freezer showcase or a unit cooler, for example.
  • the cooling unit 13 is connected to the low-temperature side circulation circuit B by a liquid pipe 15 and a gas pipe 16.
  • the expansion tanks 18a, 18b, and 18c (hereinafter simply referred to as “the expansion tanks 18" where no distinction is made therebetween) are stored in a later-described expansion tank unit housing 31.
  • the expansion tank unit housing 31 corresponds to "an expansion tank unit” of the present invention.
  • the outdoor unit 14, the cooling unit 13, and the expansion tank unit housing 31 are carried separately and connected by pipes at a designated site.
  • a carbon dioxide (CO2) refrigerant having a global warming potential (GWP) of 1, for example, is used as the refrigerant circulated through the low-temperature side circulation circuit B.
  • CO2 carbon dioxide
  • GWP global warming potential
  • the low-temperature side compressor 5 suctions the refrigerant flowing through the low-temperature side circulation circuit B.
  • the low-temperature side compressor 5 compresses the suctioned refrigerant and discharges the refrigerant at a high temperature and high pressure.
  • the auxiliary capacitor 6 exchanges heat between air and the refrigerant discharged from the low-temperature side compressor 5.
  • the low-temperature side condenser 7 exchanges heat between the refrigerant flowing from the auxiliary capacitor 6 and the refrigerant flowing through the high-temperature side evaporator 4 of the high-temperature side circulation circuit A.
  • the liquid receiver 9 stores a surplus of the refrigerant flowing from the low-temperature side condenser 7.
  • the low-temperature side flow control valve 10 expands the refrigerant flowing from the liquid receiver 9 by reducing the pressure of the refrigerant.
  • the low-temperature side flow control valve 10 is a thermostatic automatic expansion valve or an electronic expansion valve.
  • the low-temperature side evaporator 12 exchanges heat between the refrigerant reduced in pressure by the low-temperature side flow control valve 10 and a fluid (e.g., air, water, refrigerant, brine, or the like).
  • a fluid e.g., air, water, refrigerant, brine, or the like.
  • the low-temperature side second solenoid valve 17 is a solenoid valve that is closed when supplied with power.
  • the expansion tanks 18 store therein the refrigerant.
  • the expansion tanks 18 each have an outer diameter of 400 mm or less, for example.
  • the low-temperature side compressor 5 corresponds to "a second compressor" of the present invention.
  • the low-temperature side condenser 7 corresponds to "a second condenser" of the present invention.
  • the low-temperature side flow control valve 10 corresponds to "a second expansion device" of the present invention.
  • the low-temperature side evaporator 12 corresponds to "a second evaporator" of the present invention.
  • the low-temperature side second solenoid valve 17 corresponds to "an opening and closing valve" of the present invention.
  • the refrigerant flowing into the high-temperature side condenser 2 is condensed and liquefied by heat exchange with air and becomes a liquid-phase refrigerant at a high pressure.
  • the liquid-phase refrigerant at a high pressure flowing from the high-temperature side condenser 2 is reduced in pressure by the high-temperature side expansion valve 3 and becomes a two-phase gas-liquid refrigerant at a low temperature and low pressure.
  • the two-phase gas-liquid refrigerant at a low temperature and low pressure evaporates by exchanging heat with the refrigerant flowing through the low-temperature side condenser 7 of the low-temperature side circulation circuit B, and becomes a gas-phase refrigerant at a low pressure.
  • the refrigerant flowing from the high-temperature side evaporator 4 is again suctioned by the high-temperature side compressor 1.
  • auxiliary capacitor 6 heat is exchanged between air and the gas-phase refrigerant at a high temperature and high pressure, and the refrigerant is cooled and slightly reduced in temperature.
  • the refrigerant cooled by the auxiliary capacitor 6 flows into the low-temperature side condenser 7 forming the cascade capacitor 8.
  • the two-phase gas-liquid refrigerant at a low temperature and low pressure evaporates by exchanging heat with the refrigerant flowing through the low-temperature side condenser 7 of the low-temperature side circulation circuit B, and becomes a gas-phase refrigerant at a low pressure.
  • the refrigerant flowing into the low-temperature side condenser 7 is condensed by exchanging heat with the refrigerant flowing through the high-temperature side evaporator 4 of the high-temperature side circulation circuit A, and becomes a liquid-phase refrigerant at a low temperature and high pressure.
  • a portion of the refrigerant flowing into the liquid receiver 9 is stored as a surplus refrigerant, and the remaining portion of the refrigerant flows into the low-temperature side flow control valve 10.
  • the liquid-phase refrigerant at a high pressure flowing into the low-temperature side flow control valve 10 is reduced in pressure and becomes a two-phase gas-liquid refrigerant.
  • the two-phase gas-liquid refrigerant at a low temperature and low pressure flows into the low-temperature side evaporator 12.
  • the refrigerant evaporates by exchanging heat with a fluid (e.g., air), and becomes a gas-phase refrigerant at a high temperature and low pressure.
  • a fluid e.g., air
  • the gas-phase refrigerant at a low pressure flowing from the low-temperature side evaporator 12 is again suctioned by the low-temperature side compressor 5.
  • liquid receiver 9 is connected as one of the component elements of the low-temperature side circulation circuit B in Embodiment 1, the present invention is not limited thereto, and the liquid receiver 9 may not be connected.
  • liquid receiver 9 such as an accumulator may be connected to the suction side of the low-temperature side compressor 5.
  • whether or not to connect the liquid receiver 9 and the choice of the type of the liquid receiver 9 may be determined based on, for example, the purpose of the refrigeration apparatus and the refrigerant to be used.
  • Fig. 2 is a configuration diagram of the refrigeration apparatus in Embodiment 1 of this invention.
  • the outdoor unit 14 includes a high-temperature side housing 19 and a low-temperature side housing 20.
  • the high-temperature side housing 19 and the low-temperature side housing 20 have the same external shape.
  • the high-temperature side housing 19 and the low-temperature side housing 20 share a bottom plate that serves as a common table 21.
  • the high-temperature side housing 19 and the low-temperature side housing 20 are installed adjacent to each other on the common table 21.
  • the high-temperature side compressor 1, the high-temperature side condenser 2, the high-temperature side expansion valve 3, a high-temperature side fan 22, and a high-temperature side controller 24 are installed in the high-temperature side housing 19.
  • the high-temperature side fan 22 is installed in an upper part of the high-temperature side housing 19, and supplies air to the high-temperature side condenser 2.
  • the high-temperature side controller 24 executes a variety of controls of high-temperature side devices.
  • the low-temperature side compressor 5, the auxiliary capacitor 6, the liquid receiver 9, the cascade capacitor 8, a low-temperature side fan 23, and a low-temperature side controller 26 are installed in the low-temperature side housing 20.
  • the low-temperature side fan 23 is installed in an upper part of the low-temperature side housing 20, and supplies air to the auxiliary capacitor 6.
  • the low-temperature side controller 26 executes a variety of controls of low-temperature side devices.
  • the low-temperature side controller 26 controls the low-temperature side second solenoid valve 17.
  • the cascade capacitor 8 extending to both the high-temperature side and the low-temperature side may be disposed in either one of the high-temperature side housing 19 and the low-temperature side housing 20 with the arrangement and so forth taken into account.
  • the low-temperature side controller 26 corresponds to "a controller" of the present invention.
  • Fig. 3 is a configuration diagram of the outdoor unit 14 in Fig. 2 viewed from direction A.
  • the expansion tank unit housing 31 is disposed beside and spaced from the high-temperature side housing 19 and the low-temperature side housing 20.
  • the expansion tanks 18a, 18b, and 18c are stored in the expansion tank unit housing 31.
  • the expansion tank unit housing 31 includes an expansion tank unit table 30, a support 31b, and a support 31c.
  • the expansion tank 18a is mounted on the expansion tank unit table 30.
  • the expansion tank 18b is mounted on the support 31b.
  • the expansion tank 18c is mounted on the support 31c.
  • expansion tanks 18a, 18b, and 18c are mounted in the expansion tank unit housing 31 to be aligned in the vertical direction.
  • a pipe 32a is connected to a lower portion of the expansion tank 18a.
  • a pipe 32b is connected to a lower portion of the expansion tank 18b.
  • a pipe 32c is connected to a lower portion of the expansion tank 18c.
  • the pipes 32a, 32b, and 32c are assembled to a pipe 32 and connected to the low-temperature side second solenoid valve 17.
  • the pipes 32a, 32b, and 32c are connected to the lower portions of the expansion tanks 18a, 18b, and 18c so as to reliably collect refrigerating machine oil.
  • Embodiment 1 Although a case having a single low-temperature side second solenoid valve 17 will be described in Embodiment 1, the present invention is not limited thereto, and the low-temperature side second solenoid valve 17 may be provided to each of the expansion tanks 18a, 18b, and 18c.
  • expansion tanks 18a, 18b, and 18c which are stored in the expansion tank unit housing 31, may be stacked upon one another.
  • the expansion tanks 18a, 18b, and 18c each have an outer diameter of 270 mm (a thickness of 8 mm) and a length of approximately 1500 mm.
  • the depth of the expansion tank unit housing 31 is approximately 400 mm.
  • the depth of the high-temperature side housing 19 and the low-temperature side housing 20 is approximately 800 mm.
  • a suction space of 300 mm is secured for the high-temperature side condenser 2 and the auxiliary capacitor 6.
  • Fig. 4 is a diagram illustrating the relationship between the circuit internal volume and the circuit internal pressure in Embodiment 1 of this invention.
  • Fig. 4 illustrates the relationship between the pressure of the refrigerant in the low-temperature side circulation circuit B and the circuit internal volume of the low-temperature side circulation circuit B when the circulation of the refrigerant is stopped in the high-temperature side circulation circuit A and the low-temperature side circulation circuit B and the refrigerant temperature is increased to ambient temperature under the following conditions.
  • the refrigerant in the low-temperature side circulation circuit B is carbon dioxide.
  • the ambient temperature (outside air temperature) of the outdoor unit 14 is 46 degrees Celsius.
  • the nominal output from the low-temperature side compressor 5 of the low-temperature side circulation circuit B is approximately 28 kW (approximately 10 horsepower).
  • the internal volume of the low-temperature side evaporator 12 is approximately 72 liters.
  • the internal volume of the low-temperature side compressor 5, the auxiliary capacitor 6, the low-temperature side condenser 7, and the liquid receiver 9 is approximately 40 liters.
  • the extension pipes have a length of 70 m, the internal volume thereof is approximately 48 liters.
  • the value resulting from adding the internal volume of the expansion tanks 18a, 18b, and 18c to approximately 160 liters corresponds to the circuit internal volume of the low-temperature side circulation circuit B.
  • the required circuit internal volume (black triangles in the drawing) is approximately 400 liters.
  • the outer diameter and the length thereof are 270 mm (a thickness of 8 mm) and approximately 1500 mm, respectively.
  • the required circuit internal volume (black rhombi in Fig. 4 ) is approximately 300 liters.
  • two expansion tanks 18 having an outer diameter of 270 mm (a thickness of 8 mm) and a length of approximately 1500 mm may suffice.
  • the internal volume and the number of the expansion tanks 18 are not limited to those of the above-described configurations, and may be selected as appropriate in accordance with the necessary internal volume.
  • the pipe diameter of the gas pipe 16 is 31.75 mm if R410A is used, whereas it is possible to set the pipe diameter of the gas pipe 16 to 19.05 mm if carbon dioxide is used.
  • the internal volume is increased by approximately 40 liters.
  • the capacity of the expansion tanks 18 has been calculated on the assumption that the ambient temperature is 46 degrees Celsius under the above-described conditions, the internal volume and the number of the expansion tanks 18 may be selected as appropriate in accordance with the temperature environment in which the refrigeration apparatus is used.
  • the capacity or the number of the expansion tanks 18 may be reduced.
  • the specifications of a copper pipe (hairpin) passing through the plate fin tube-type low-temperature side evaporator 12 include a diameter of approximately 9.52 mm (a thickness of 0.8 mm).
  • the specifications of the hairpin in the low-temperature side evaporator 12 include a diameter of approximately 9.52 mm (a thickness of 0.35 mm).
  • the refrigeration apparatus with the low-temperature side circulation circuit B having a design pressure of 4.15 MPa or lower is capable of reducing the manufacturing cost to half or less compared with the refrigeration apparatus with the low-temperature side circulation circuit B having a design pressure of 8.5 MPa.
  • Fig. 5 is a flowchart illustrating an operation of the refrigeration apparatus in Embodiment 1 of this invention.
  • the low-temperature side controller 26 acquires the pressure on the discharge side of the low-temperature side compressor 5 detected by the low-temperature side high pressure sensor 27 and the pressure on the suction side of the low-temperature side compressor 5 detected by the low-temperature side low pressure sensor 28.
  • the low-temperature side controller 26 determines whether or not at least one of the pressure on the suction side and the pressure on the discharge side of the low-temperature side compressor 5 is equal to or higher than a preset pressure value P1.
  • the low-temperature side controller 26 repeats step S1.
  • the pressure value P1 is set in accordance with, for example, the design pressure of the low-temperature side circulation circuit B. For example, if the design pressure is 4.15 MPa, the pressure value P1 is set to 4 MPa in consideration of measurement errors of the sensors, operating times of the solenoid valves, and so forth.
  • the pressure value P1 corresponds to "a first pressure value" of the present invention.
  • the low-temperature side controller 26 opens the low-temperature side second solenoid valve 17.
  • the refrigerant in the low-temperature side circulation circuit B flows into each of the expansion tanks 18a, 18b, and 18c. That is, the circuit internal volume of the low-temperature side circulation circuit B is increased, and the pressure of the refrigerant is reduced.
  • the low-temperature side controller 26 determines whether or not the pressure on the suction side and the pressure on the discharge side of the low-temperature side compressor 5 is equal to or lower than a preset pressure value P2.
  • the low-temperature side controller 26 If the pressure on the suction side and the pressure on the discharge side of the low-temperature side compressor 5 is not equal to or lower than the preset pressure value P2, the low-temperature side controller 26 returns to step S2 to maintain the low-temperature side second solenoid valve 17 in the open state.
  • the pressure value P2 is set to a value lower than the pressure value P1.
  • the pressure value P2 corresponds to "a second pressure value" of the present invention.
  • the low-temperature side controller 26 closes the low-temperature side second solenoid valve 17 and returns to step S1.
  • the low-temperature side second solenoid valve 17 is closed to stop the flow of the refrigerant into the expansion tanks 18. It is thereby possible to collect the refrigerant in a short time when the low-temperature side compressor 5 is restarted.
  • Power supply to the refrigeration apparatus may be stopped for a long time owing to a power failure, for example.
  • the low-temperature side second solenoid valve 17 in Embodiment 1 is a solenoid valve that is closed when supplied with power. Even when the low-temperature side compressor 5 is stopped owing to a power failure or the like, therefore, the low-temperature side second solenoid valve 17 is open, increasing the circuit internal volume of the low-temperature side circulation circuit B and reducing the pressure of the refrigerant.
  • the low-temperature side controller 26 opens the low-temperature side second solenoid valve 17 for a preset time.
  • the low-temperature side controller 26 opens the low-temperature side second solenoid valve 17 when the low-temperature side compressor 5 is started, and closes the low-temperature side second solenoid valve 17 after the lapse of a preset time.
  • steps S3 and S4 described above may be omitted to maintain the low-temperature side second solenoid valve 17 in the open state. Further, the low-temperature side second solenoid valve 17 may be closed after the lapse of a preset time from the restart of the low-temperature side compressor 5.
  • Embodiment 1 includes the expansion tanks 18 connected to the pipe between the low-temperature side evaporator 12 and the low-temperature side compressor 5 via the low-temperature side second solenoid valve 17.
  • the design pressure of the low-temperature side circulation circuit B is set to 4.15 MPa, which is equal to the design pressure in the case using the R410A refrigerant.
  • materials employed in a case using the versatile HFC refrigerant are usable in the low-temperature side compressor 5, the auxiliary capacitor 6, the cascade capacitor 8, the liquid receiver 9, the low-temperature side evaporator 12 (a showcase or a unit cooler), the liquid pipe 15, the gas pipe 16, and the expansion tanks 18, which are components of the low-temperature side circulation circuit B.
  • the low-temperature side second solenoid valve 17 is a solenoid valve that is closed when supplied with power, it is possible to suppress the increase in pressure of the refrigerant in the low-temperature side circulation circuit B even if power supply to the refrigeration apparatus is stopped for a long time owing to a power failure or the like.
  • Fig. 6 is a configuration diagram of a refrigeration apparatus in Embodiment 2 of this invention.
  • a pipe 33a is inserted in the expansion tank 18a from an upper portion of the expansion tank 18a.
  • An end portion of the pipe 33a is disposed at a position near the bottom of the expansion tank 18a.
  • a pipe 33b is inserted in the expansion tank 18b from an upper portion of the expansion tank 18b. An end portion of the pipe 33b is disposed at a position near the bottom of the expansion tank 18b.
  • a pipe 33c is inserted in the expansion tank 18c from an upper portion of the expansion tank 18c. An end portion of the pipe 33c is disposed at a position near the bottom of the expansion tank 18c.
  • the pipes 33a, 33b, and 33c are assembled to a pipe 33 and connected to the low-temperature side second solenoid valve 17.
  • the end portions of the pipes 33a, 33b, and 33c are disposed at the positions near the bottoms of the expansion tanks 18a, 18b, and 18c so as to reliably collect the refrigerating machine oil.
  • Embodiment 2 Effects similar to those of Embodiment 1 are also obtainable in Embodiment 2.
  • Fig. 7 is a configuration diagram of a refrigeration apparatus in Embodiment 3 of this invention.
  • an expansion tank table 35 is provided below the common table 21 for the high-temperature side housing 19 and the low-temperature side housing 20.
  • the expansion tanks 18a, 18b, and 18c are mounted on the expansion tank table 35.
  • the expansion tank table 35 is disposed below and adjacent to the high-temperature side housing 19 and the low-temperature side housing 20, and the expansion tanks 18a, 18b, and 18c are mounted on the expansion tank table 35 to be aligned in the horizontal direction.
  • the expansion tank table 35 corresponds to "an expansion tank unit" of the present invention.
  • a pipe 34a is connected to a lower portion of the expansion tank 18a.
  • a pipe 34b is connected to a lower portion of the expansion tank 18b.
  • a pipe 34c is connected to a lower portion of the expansion tank 18c.
  • the pipes 34a, 34b, and 34c are assembled to a pipe 34 and connected to the low-temperature side second solenoid valve 17.
  • the pipes 34a, 34b, and 34c are connected to the lower portions of the expansion tanks 18a, 18b, and 18c so as to reliably collect the refrigerating machine oil.
  • Embodiment 3 Effects similar to those of Embodiment 1 are also obtainable in Embodiment 3.
  • expansion tank table 35 is provided below the common table 21 for the high-temperature side housing 19 and the low-temperature side housing 20, it is possible to make the installation widths (depths) of the expansion tanks 18a and the outdoor unit 14 less than those in Embodiment 1 described above.
  • each of the expansion tanks 18 is 300 mm or less, it is possible to set the depth of the outdoor unit 14 to 1000 mm or less.
  • Fig. 8 is a configuration diagram of a refrigeration apparatus in Embodiment 4 of this invention.
  • a pipe 36a is inserted in the expansion tank 18a from an upper portion of the expansion tank 18a.
  • An end portion of the pipe 36a is disposed at a position near the bottom of the expansion tank 18a.
  • a pipe 36b is inserted in the expansion tank 18b from an upper portion of the expansion tank 18b. An end portion of the pipe 36b is disposed at a position near the bottom of the expansion tank 18b.
  • a pipe 36c is inserted in the expansion tank 18c from an upper portion of the expansion tank 18c. An end portion of the pipe 36c is disposed at a position near the bottom of the expansion tank 18c.
  • the pipes 36a, 36b, and 36c are assembled to a pipe 36 and connected to the low-temperature side second solenoid valve 17.
  • the end portions of the pipes 36a, 36b, and 36c are disposed at the positions near the bottoms of the expansion tanks 18a, 18b, and 18c so as to reliably collect the refrigerating machine oil.
  • Embodiment 4 Effects similar to those of Embodiment 3 are also obtainable in Embodiment 4.
  • Embodiments 1 to 4 described above the description has been given of the refrigeration apparatus in which the high-temperature side circulation circuit A and the low-temperature side circulation circuit B are cascade-connected.
  • Embodiment 5 description will be given of a refrigeration apparatus that performs two-stage compression.
  • Fig. 9 is a refrigerant circuit diagram of the refrigeration apparatus in Embodiment 5 of this invention.
  • the refrigeration apparatus of Embodiment 5 includes a circulation circuit in which a low-stage side compressor 55, a high-stage side compressor 51, an intermediate cooler 54, a low-stage side first solenoid valve 57, a low-stage side first flow control valve 56, and a low-stage side evaporator 58 are sequentially connected by pipes to circulate a refrigerant therethrough.
  • the refrigeration apparatus of Embodiment 5 further includes an intermediate pressure circuit that branches from an outlet side of a gas cooler 52 and supplies the refrigerant passed through an intermediate cooling flow control valve 53 and the intermediate cooler 54 and reduced in pressure to between the low-stage side compressor 55 and the high-stage side compressor 51.
  • a pipe between the low-stage side evaporator 58 and the low-stage side compressor 55 is connected to an expansion tank 63a, an expansion tank 63b, and an expansion tank 63c via a low-stage side second solenoid valve 62.
  • a carbon dioxide (CO2) refrigerant having a global warming potential (GWP) of 1 is used as the refrigerant circulated through the circulation circuit and the intermediate pressure circuit of the refrigeration apparatus in Embodiment 5.
  • CO2 carbon dioxide
  • GWP global warming potential
  • a low-stage side high pressure sensor 64 detects the pressure on a discharge side of the low-stage side compressor 55.
  • a low-stage side low pressure sensor 65 detects the pressure on a suction side of the low-stage side compressor 55.
  • the low-stage side first flow control valve 56, the low-stage side first solenoid valve 57, and the low-stage side evaporator 58 are stored in a low-stage side cooling unit 59.
  • the low-stage side cooling unit 59 is used as a refrigerator-freezer showcase or a unit cooler, for example.
  • the low-stage side cooling unit 59 is connected to the circulation circuit by a low-stage side liquid pipe 60 and a low-stage side gas pipe 61.
  • the low-stage side second solenoid valve 62 is a solenoid valve that is closed when supplied with power.
  • the low-stage side second solenoid valve 62 is controlled by a controller 66.
  • the internal volume and the number of the expansion tanks 63a, 63b, and 63c may be selected as appropriate based on the relationship between the circuit internal volume and the circuit internal pressure and the design pressure with the application of the technical concept described in Embodiment 1.
  • the low-stage side compressor 55 corresponds to "a first-stage compressor" of the present invention.
  • the high-stage side compressor 51 corresponds to "a second-stage compressor" of the present invention.
  • the gas cooler 52 corresponds to "a radiator" of the present invention.
  • the low-stage side first flow control valve 56 corresponds to "an expansion device" of the present invention.
  • the low-stage side evaporator 58 corresponds to "an evaporator" of the present invention.
  • the low-stage side second solenoid valve 62 corresponds to "an opening and closing valve" of the present invention.
  • the controller 66 corresponds to "a controller" of the present invention.
  • Fig. 10 is a Mollier chart illustrating the operation of the refrigeration apparatus in Embodiment 5 of this invention.
  • a gas-phase refrigerant at a low pressure flowing from the low-stage side evaporator 58 (point F in Fig. 10 ) is suctioned by the low-stage side compressor 55 and compressed to an intermediate pressure.
  • Superheated vapor discharged from the low-stage side compressor 55 joins a refrigerant at an intermediate pressure flowing from the intermediate cooler 54 (point H in Fig. 10 ) and enters the high-stage side compressor 51.
  • the gas refrigerant compressed by the high-stage side compressor 51 (point J in Fig. 10 ) is cooled by the gas cooler 52 to be slightly subcooled (point K in Fig. 10 ).
  • the subcooled liquid refrigerant flowing into the low-stage side first flow control valve 56 is reduced in pressure and becomes a two-phase gas-liquid refrigerant (point Q in Fig. 10 ).
  • the two-phase gas-liquid refrigerant at a low temperature and low pressure flows into the low-stage side evaporator 58.
  • the refrigerant evaporates by exchanging heat with a fluid (e.g., air), and becomes a gas-phase refrigerant at a high temperature and low pressure.
  • a fluid e.g., air
  • the gas-phase refrigerant at a low pressure flowing from the low-stage side evaporator 58 (point F in Fig. 10 ) is again suctioned by the low-stage side compressor 55.
  • the refrigerant branching from the outlet side of the gas cooler 52 becomes a refrigerant reduced in pressure to the intermediate pressure by the intermediate cooling flow control valve 53 (point N in Fig. 10 ).
  • the refrigerant at the intermediate pressure flows into an intermediate-pressure side of the intermediate cooler 54.
  • the refrigerant flowing into the intermediate-pressure side of the intermediate cooler 54 exchanges heat with the refrigerant flowing on the high-pressure side of the intermediate cooler 54 to increase the degree of subcooling of the high-pressure gas flowing toward the low-stage side first solenoid valve 57 (point K in Fig. 10 ) (point M in Fig. 10 ).
  • a technical concept similar to that of the control operation of the low-temperature side second solenoid valve 17 in Embodiment 1 described above is applicable to the control operation of the low-stage side second solenoid valve 62.
  • Fig. 11 is a flowchart illustrating the operation of the refrigeration apparatus in Embodiment 5 of this invention.
  • the controller 66 acquires the pressure on the discharge side of the low-stage side compressor 55 detected by the low-stage side high pressure sensor 64 and the pressure on the suction side of the low-stage side compressor 55 detected by the low-stage side low pressure sensor 65.
  • the controller 66 determines whether or not at least one of the pressure on the suction side and the pressure on the discharge side of the low-stage side compressor 55 is equal to or higher than a preset pressure value P1.
  • step S11 If at least one of the pressure on the suction side and the pressure on the discharge side of the low-stage side compressor 55 is not equal to or higher than the preset pressure value P1, the controller 66 repeats step S11.
  • the pressure value P1 is set in accordance with, for example, the design pressure of the circulation circuit. For example, if the design pressure is 4.15 MPa, the pressure value P1 is set to 4 MPa in consideration of measurement errors of the sensors, operating times of the solenoid valves, and so forth.
  • the pressure value P1 corresponds to "a first pressure value" of the present invention.
  • the controller 66 opens the low-stage side second solenoid valve 62.
  • the refrigerant in the circulation circuit flows into each of the expansion tanks 63a, 63b, and 63c. That is, the circuit internal volume of the circulation circuit is increased, and the pressure of the refrigerant is reduced.
  • the controller 66 determines whether or not the pressure on the suction side and the pressure on the discharge side of the low-stage side compressor 55 is equal to or lower than a preset pressure value P2.
  • the controller 66 If the pressure on the suction side and the pressure on the discharge side of the low-stage side compressor 55 is not equal to or lower than the preset pressure value P2, the controller 66 returns to step S12 to maintain the low-stage side second solenoid valve 62 in the open state.
  • the pressure value P2 is set to a value lower than the pressure value P1.
  • the pressure value P2 corresponds to "a second pressure value" of the present invention.
  • the controller 66 closes the low-stage side second solenoid valve 62 and returns to step S11.
  • the low-stage side second solenoid valve 62 is closed to stop the flow of the refrigerant into the expansion tanks 63. It is thereby possible to collect the refrigerant in a short time when the low-stage side compressor 55 is restarted.
  • Power supply to the refrigeration apparatus may be stopped for a long time owing to a power failure, for example.
  • the low-stage side second solenoid valve 62 in Embodiment 5 is a solenoid valve that is closed when supplied with power. Even when the low-stage side compressor 55 is stopped owing to a power failure or the like, therefore, the low-stage side second solenoid valve 62 is open, increasing the circuit internal volume of the circulation circuit and reducing the pressure of the refrigerant.
  • the controller 66 opens the low-stage side second solenoid valve 62 for a preset time.
  • the controller 66 opens the low-stage side second solenoid valve 62 when the low-stage side compressor 55 is started, and closes the low-stage side second solenoid valve 62 after the lapse of a preset time.
  • steps S13 and S14 described above may be omitted to maintain the low-stage side second solenoid valve 62 in the open state. Further, the low-stage side second solenoid valve 62 may be closed after the lapse of a preset time from the restart of the low-stage side compressor 55.
  • Embodiment 5 includes the expansion tanks 63 connected to the pipe between the low-stage side evaporator 58 and the low-stage side compressor 55 via the low-stage side second solenoid valve 62.
  • the low-stage side second solenoid valve 62 is a solenoid valve that is closed when supplied with power, it is possible to suppress the increase in pressure of the refrigerant in the circulation circuit even if power supply to the refrigeration apparatus is stopped for a long time owing to a power failure or the like.

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Description

    Technical Field
  • This invention relates to a refrigeration apparatus including circulation circuits (refrigeration cycles) that circulate a refrigerant.
  • Background Art
  • US 2009/0126389 discloses a refrigeration apparatus having a plurality of expansion tanks which are connected to the suction side of a low-temperature compressor by means of a check valve and a capillary tube in parallel.
  • US 6,539,735 discloses a refrigerant expansion tank.
  • US 2006/0075775 discloses an efficient heat exchange for refrigeration process.
  • US 2010/0251750 discloses an economized refrigerant system with flow control.
  • In the past, a refrigeration apparatus has been known which operates a binary refrigeration cycle with a high-temperature side circulation circuit (high-temperature side refrigeration cycle) and a low-temperature side circulation circuit (low-temperature side refrigeration cycle) cascade-connected via a cascade capacitor.
  • An existing refrigeration apparatus has been proposed which, when a compressor of a low-temperature side circulation circuit is stopped, operates a compressor of a high-temperature side circulation circuit to cool a refrigerant in the low-temperature side circulation circuit to thereby suppress an increase in pressure of the low-temperature side circulation circuit (see Japanese Unexamined Patent Application Publication No. 2004-190917 (paragraphs [0008]-[0023] and Fig. 1).
  • For example, when a defrosting operation is performed for an evaporator of the low-temperature side circulation circuit, the compressor of the high-temperature side circulation circuit is operated with the compressor of the low-temperature side circulation circuit stopped. Further, when the compressor of the low-temperature side circulation circuit in the stopped (thermo-off) state is restarted, the compressor of the low-temperature side circulation circuit is restarted after the lapse of a predetermined time from the start of the compressor of the high-temperature side circulation circuit.
  • Summary of Invention Technical Problem
  • The existing refrigeration apparatus, however, has an issue in that the compressor of the high-temperature side circulation circuit needs to be uselessly operated despite the state in which a cooling operation is not performed with the compressor of the low-temperature side circulation circuit stopped.
  • For example, if carbon dioxide is used as the refrigerant in the low-temperature side circulation circuit, the compressor of the high-temperature side circulation circuit needs to be operated for an extra time of approximately 30 minutes to approximately 40 minutes in the defrosting operation for the evaporator of the low-temperature side circulation circuit in order to keep the design pressure of the low-temperature side circulation circuit no higher than approximately 3 MPa to approximately 4 MPa. The defrosting operation takes place about four times to five times a day.
  • Further, there is another issue in that, when the compressor of the low-temperature side circulation circuit is stopped (thermo-off) and then is restarted, the compressor of the low-temperature side circulation circuit is started after the lapse of a predetermined time (tens of seconds to a few minutes) from the start of the compressor of the high-temperature side circulation circuit, and thus the pull-down speed is reduced.
  • Further, if the compressor of the high-temperature side circulation circuit is not operated when the compressor of the low-temperature side circulation circuit is stopped, and if the compressor of the low-temperature side circulation circuit is stopped for a long time, the refrigerant in the low-temperature side circulation circuit is warmed to about outside air temperature, resulting in an increase in pressure.
  • To address such an increase in pressure of the low-temperature side circulation circuit, the structure of members forming the low-temperature side circulation circuit needs to be strong. For example, refrigerant pipes need to be thick. This leads to an issue of an increase in manufacturing cost.
  • Further, if the pressure of the refrigerant in the low-temperature side circulation circuit is increased to exceed the design pressure, the refrigerant may be discharged from a safety valve. In this case, the low-temperature side circulation circuit needs to be refilled with a refrigerant.
  • This invention has been made to solve the above-described issues, and obtains a refrigeration apparatus capable of suppressing the increase in pressure of the refrigerant in the low-temperature side circulation circuit when the compressor of the low-temperature side circulation circuit is stopped.
  • This invention also obtains a refrigeration apparatus capable of suppressing the increase in pressure of the refrigerant in the low-temperature side circulation circuit without operating the compressor of the high-temperature side circulation circuit when the compressor of the low-temperature side circulation circuit is stopped or restarted.
  • This invention further obtains a refrigeration apparatus capable of reducing the design pressure of the low-temperature side circulation circuit.
  • Solution to Problem
  • A refrigeration apparatus as set forth in claim 1 and claim 9.
  • Advantageous Effects of Invention
  • This invention includes the expansion tanks connected to the pipe between the second evaporator and the second compressor via the opening and closing valve, and therefore is capable of suppressing the increase in pressure of the refrigerant in the low-temperature side circulation circuit without operating the compressor of the high-temperature side refrigerant circuit.
  • Brief Description of Drawings
    • [Fig. 1] Fig. 1 is a refrigerant circuit diagram of a refrigeration apparatus in Embodiment 1 of this invention.
    • [Fig. 2] Fig. 2 is a configuration diagram of the refrigeration apparatus in Embodiment 1 of this invention.
    • [Fig. 3] Fig. 3 is a configuration diagram of an outdoor unit in Fig. 2 viewed from direction A.
    • [Fig. 4] Fig. 4 is a diagram illustrating the relationship between circuit internal volume and circuit internal pressure in Embodiment 1 of this invention.
    • [Fig. 5] Fig. 5 is a flowchart illustrating an operation of the refrigeration apparatus in Embodiment 1 of this invention.
    • [Fig. 6] Fig. 6 is a configuration diagram of a refrigeration apparatus in Embodiment 2 of this invention.
    • [Fig. 7] Fig. 7 is a configuration diagram of a refrigeration apparatus in Embodiment 3 of this invention.
    • [Fig. 8] Fig. 8 is a configuration diagram of a refrigeration apparatus in Embodiment 4 of this invention.
    • [Fig. 9] Fig. 9 is a refrigerant circuit diagram of a refrigeration apparatus in Embodiment 5 of this invention.
    • [Fig. 10] Fig. 10 is a Mollier chart illustrating an operation of the refrigeration apparatus in Embodiment 5 of this invention.
    • [Fig. 11] Fig. 11 is a flowchart illustrating the operation of the refrigeration apparatus in Embodiment 5 of this invention.
    Description of Embodiments
  • Embodiments of the present invention will be described below based on the drawings.
  • In the following drawings, the dimensional relationship between component members may be different from the actual one.
  • Embodiment 1 [Configuration]
  • Fig. 1 is a refrigerant circuit diagram of a refrigeration apparatus in Embodiment 1 of this invention.
  • As illustrated in Fig. 1, the refrigeration apparatus includes a high-temperature side circulation circuit A and a low-temperature side circulation circuit (load side circuit) B.
  • The high-temperature side circulation circuit A and the low-temperature side circulation circuit B are cascade-connected via a cascade capacitor 8.
  • The refrigeration apparatus operates a binary refrigeration cycle by circulating a refrigerant in each of the high-temperature side circulation circuit A and the low-temperature side circulation circuit B.
  • It is assumed herein that the levels and so forth of the temperature, the pressure, and so forth of configurations referred to as the low-temperature side and the high-temperature side are not particularly determined by the relationship thereof with respective absolute values, but are relatively determined by the state, the operation, and so forth of the refrigeration apparatus.
  • Although the binary refrigeration cycle including two refrigerant circuits will be described in Embodiment 1, refrigeration apparatuses according to the present invention include a refrigeration apparatus including three or more refrigeration cycles (a multiple refrigeration apparatus).
  • (High-Temperature Side Circulation Circuit A)
  • The high-temperature side circulation circuit A includes a high-temperature side compressor 1, a high-temperature side condenser 2, a high-temperature side expansion valve 3, and a high-temperature side evaporator 4.
  • The high-temperature side compressor 1, the high-temperature side condenser 2, the high-temperature side expansion valve 3, and the high-temperature side evaporator 4 are connected in series by refrigerant pipes.
  • The high-temperature side compressor 1, the high-temperature side condenser 2, the high-temperature side expansion valve 3, and the high-temperature side evaporator 4 are stored in a later-described outdoor unit 14.
  • A refrigerant having a relatively small global warming potential (GWP) (e.g., an R410A, R134a, R32, or HFO refrigerant) is used as the refrigerant circulated through the high-temperature side circulation circuit A.
  • The high-temperature side compressor 1 suctions the refrigerant flowing through the high-temperature side circulation circuit A.
  • The high-temperature side compressor 1 compresses the suctioned refrigerant and discharges the refrigerant at a high temperature and high pressure.
  • The high-temperature side condenser 2 exchanges heat between air and the refrigerant discharged from the high-temperature side compressor 1.
  • The high-temperature side expansion valve 3 expands the refrigerant flowing from the high-temperature side condenser 2 by reducing the pressure of the refrigerant.
  • The high-temperature side evaporator 4 exchanges heat between the refrigerant reduced in pressure by the high-temperature side expansion valve 3 and the refrigerant flowing through a low-temperature side condenser 7 of the low-temperature side circulation circuit B.
  • The high-temperature side evaporator 4 and the low-temperature side condenser 7 form the cascade capacitor 8.
  • The cascade capacitor 8 is formed of a plate-type heat exchanger, for example.
  • The cascade capacitor 8 is not limited to the plate-type heat exchanger, and may be a shell-and-tube-type heat exchanger or a double pipe-type heat exchanger.
  • The high-temperature side compressor 1 corresponds to "a first compressor" of the present invention.
  • The high-temperature side condenser 2 corresponds to "a first condenser" of the present invention.
  • The high-temperature side expansion valve 3 corresponds to "a first expansion device" of the present invention.
  • The high-temperature side evaporator 4 corresponds to "a first evaporator" of the present invention.
  • (Low-Temperature Side Circulation Circuit B)
  • The low-temperature side circulation circuit B includes a low-temperature side compressor 5, an auxiliary capacitor 6, the low-temperature side condenser 7, a liquid receiver 9, a low-temperature side flow control valve 10, a low-temperature side first solenoid valve 11, a low-temperature side evaporator 12, a low-temperature side high pressure sensor 27, and a low-temperature side low pressure sensor 28.
  • The low-temperature side compressor 5, the auxiliary capacitor 6, the low-temperature side condenser 7, the liquid receiver 9, the low-temperature side first solenoid valve 11, the low-temperature side flow control valve 10, and the low-temperature side evaporator 12 are connected in series by refrigerant pipes.
  • A pipe between the low-temperature side condenser 7 and the low-temperature side compressor 5 is connected to an expansion tank 18a, an expansion tank 18b, and an expansion tank 18c via a low-temperature side second solenoid valve 17.
  • The low-temperature side high pressure sensor 27 detects the pressure on a discharge side of the low-temperature side compressor 5.
  • The low-temperature side low pressure sensor 28 detects the pressure on a suction side of the low-temperature side compressor 5.
  • The low-temperature side compressor 5, the auxiliary capacitor 6, the low-temperature side condenser 7, the liquid receiver 9, the low-temperature side high pressure sensor 27, and the low-temperature side low pressure sensor 28 are stored in the later-described outdoor unit 14.
  • The low-temperature side first solenoid valve 11, the low-temperature side flow control valve 10, and the low-temperature side evaporator 12 are stored in a cooling unit 13.
  • The cooling unit 13 is used as a refrigerator-freezer showcase or a unit cooler, for example.
  • The cooling unit 13 is connected to the low-temperature side circulation circuit B by a liquid pipe 15 and a gas pipe 16.
  • The expansion tanks 18a, 18b, and 18c (hereinafter simply referred to as "the expansion tanks 18" where no distinction is made therebetween) are stored in a later-described expansion tank unit housing 31.
  • The expansion tank unit housing 31 corresponds to "an expansion tank unit" of the present invention.
  • For example, in the installation of the refrigeration apparatus, the outdoor unit 14, the cooling unit 13, and the expansion tank unit housing 31 are carried separately and connected by pipes at a designated site.
  • A carbon dioxide (CO2) refrigerant having a global warming potential (GWP) of 1, for example, is used as the refrigerant circulated through the low-temperature side circulation circuit B.
  • The low-temperature side compressor 5 suctions the refrigerant flowing through the low-temperature side circulation circuit B.
  • The low-temperature side compressor 5 compresses the suctioned refrigerant and discharges the refrigerant at a high temperature and high pressure.
  • The auxiliary capacitor 6 exchanges heat between air and the refrigerant discharged from the low-temperature side compressor 5.
  • The low-temperature side condenser 7 exchanges heat between the refrigerant flowing from the auxiliary capacitor 6 and the refrigerant flowing through the high-temperature side evaporator 4 of the high-temperature side circulation circuit A.
  • The liquid receiver 9 stores a surplus of the refrigerant flowing from the low-temperature side condenser 7.
  • The low-temperature side flow control valve 10 expands the refrigerant flowing from the liquid receiver 9 by reducing the pressure of the refrigerant.
  • The low-temperature side flow control valve 10 is a thermostatic automatic expansion valve or an electronic expansion valve.
  • The low-temperature side evaporator 12 exchanges heat between the refrigerant reduced in pressure by the low-temperature side flow control valve 10 and a fluid (e.g., air, water, refrigerant, brine, or the like).
  • The low-temperature side second solenoid valve 17 is a solenoid valve that is closed when supplied with power.
  • The expansion tanks 18 store therein the refrigerant.
  • The expansion tanks 18 each have an outer diameter of 400 mm or less, for example.
  • The low-temperature side compressor 5 corresponds to "a second compressor" of the present invention.
  • The low-temperature side condenser 7 corresponds to "a second condenser" of the present invention.
  • The low-temperature side flow control valve 10 corresponds to "a second expansion device" of the present invention.
  • The low-temperature side evaporator 12 corresponds to "a second evaporator" of the present invention.
  • The low-temperature side second solenoid valve 17 corresponds to "an opening and closing valve" of the present invention.
  • (Operation of High-Temperature Side Circulation Circuit A)
  • The gas-phase refrigerant at a high temperature and high pressure discharged from the high-temperature side compressor 1 flows into the high-temperature side condenser 2.
  • The refrigerant flowing into the high-temperature side condenser 2 is condensed and liquefied by heat exchange with air and becomes a liquid-phase refrigerant at a high pressure.
  • The liquid-phase refrigerant at a high pressure flowing from the high-temperature side condenser 2 is reduced in pressure by the high-temperature side expansion valve 3 and becomes a two-phase gas-liquid refrigerant at a low temperature and low pressure.
  • In the high-temperature side evaporator 4 forming the cascade capacitor 8, the two-phase gas-liquid refrigerant at a low temperature and low pressure evaporates by exchanging heat with the refrigerant flowing through the low-temperature side condenser 7 of the low-temperature side circulation circuit B, and becomes a gas-phase refrigerant at a low pressure.
  • In this process, the refrigerant flowing through the low-temperature side condenser 7 of the low-temperature side circulation circuit B is cooled.
  • The refrigerant flowing from the high-temperature side evaporator 4 is again suctioned by the high-temperature side compressor 1.
  • (Operation of Low-Temperature Side Circulation Circuit B)
  • The gas-phase refrigerant at a high temperature and high pressure discharged from the low-temperature side compressor 5 flows into the auxiliary capacitor 6.
  • In the auxiliary capacitor 6, heat is exchanged between air and the gas-phase refrigerant at a high temperature and high pressure, and the refrigerant is cooled and slightly reduced in temperature.
  • The refrigerant cooled by the auxiliary capacitor 6 flows into the low-temperature side condenser 7 forming the cascade capacitor 8.
  • In the high-temperature side evaporator 4 forming the cascade capacitor 8, the two-phase gas-liquid refrigerant at a low temperature and low pressure evaporates by exchanging heat with the refrigerant flowing through the low-temperature side condenser 7 of the low-temperature side circulation circuit B, and becomes a gas-phase refrigerant at a low pressure.
  • The refrigerant flowing into the low-temperature side condenser 7 is condensed by exchanging heat with the refrigerant flowing through the high-temperature side evaporator 4 of the high-temperature side circulation circuit A, and becomes a liquid-phase refrigerant at a low temperature and high pressure.
  • In this process, the refrigerant flowing through the high-temperature side evaporator 4 of the high-temperature side circulation circuit A is warmed.
  • The liquid-phase refrigerant at a low temperature and high pressure flowing from the low-temperature side condenser 7 flows into the liquid receiver 9.
  • A portion of the refrigerant flowing into the liquid receiver 9 is stored as a surplus refrigerant, and the remaining portion of the refrigerant flows into the low-temperature side flow control valve 10.
  • The liquid-phase refrigerant at a high pressure flowing into the low-temperature side flow control valve 10 is reduced in pressure and becomes a two-phase gas-liquid refrigerant.
  • The two-phase gas-liquid refrigerant at a low temperature and low pressure flows into the low-temperature side evaporator 12.
  • In the low-temperature side evaporator 12, the refrigerant evaporates by exchanging heat with a fluid (e.g., air), and becomes a gas-phase refrigerant at a high temperature and low pressure.
  • In this process, a cooling target space is cooled in the cooling unit 13.
  • The gas-phase refrigerant at a low pressure flowing from the low-temperature side evaporator 12 is again suctioned by the low-temperature side compressor 5.
  • Although the liquid receiver 9 is connected as one of the component elements of the low-temperature side circulation circuit B in Embodiment 1, the present invention is not limited thereto, and the liquid receiver 9 may not be connected.
  • Further, in place of the liquid receiver 9, a liquid receiver such as an accumulator may be connected to the suction side of the low-temperature side compressor 5.
  • That is, whether or not to connect the liquid receiver 9 and the choice of the type of the liquid receiver 9 may be determined based on, for example, the purpose of the refrigeration apparatus and the refrigerant to be used.
  • Description will now be given of the arrangement of devices in the respective units and details of the devices.
  • (Outdoor Unit 14)
  • Fig. 2 is a configuration diagram of the refrigeration apparatus in Embodiment 1 of this invention.
  • As illustrated in Fig. 2, the outdoor unit 14 includes a high-temperature side housing 19 and a low-temperature side housing 20.
  • The high-temperature side housing 19 and the low-temperature side housing 20 have the same external shape.
  • The high-temperature side housing 19 and the low-temperature side housing 20 share a bottom plate that serves as a common table 21.
  • The high-temperature side housing 19 and the low-temperature side housing 20 are installed adjacent to each other on the common table 21.
  • The high-temperature side compressor 1, the high-temperature side condenser 2, the high-temperature side expansion valve 3, a high-temperature side fan 22, and a high-temperature side controller 24 are installed in the high-temperature side housing 19.
  • The high-temperature side fan 22 is installed in an upper part of the high-temperature side housing 19, and supplies air to the high-temperature side condenser 2.
  • The high-temperature side controller 24 executes a variety of controls of high-temperature side devices.
  • The low-temperature side compressor 5, the auxiliary capacitor 6, the liquid receiver 9, the cascade capacitor 8, a low-temperature side fan 23, and a low-temperature side controller 26 are installed in the low-temperature side housing 20.
  • The low-temperature side fan 23 is installed in an upper part of the low-temperature side housing 20, and supplies air to the auxiliary capacitor 6.
  • The low-temperature side controller 26 executes a variety of controls of low-temperature side devices.
  • The low-temperature side controller 26 controls the low-temperature side second solenoid valve 17.
  • The cascade capacitor 8 extending to both the high-temperature side and the low-temperature side may be disposed in either one of the high-temperature side housing 19 and the low-temperature side housing 20 with the arrangement and so forth taken into account.
  • The low-temperature side controller 26 corresponds to "a controller" of the present invention.
  • (Expansion Tank Unit Housing 31)
  • Fig. 3 is a configuration diagram of the outdoor unit 14 in Fig. 2 viewed from direction A.
  • As illustrated in Fig. 3, the expansion tank unit housing 31 is disposed beside and spaced from the high-temperature side housing 19 and the low-temperature side housing 20.
  • The expansion tanks 18a, 18b, and 18c are stored in the expansion tank unit housing 31.
  • The expansion tank unit housing 31 includes an expansion tank unit table 30, a support 31b, and a support 31c.
  • The expansion tank 18a is mounted on the expansion tank unit table 30.
  • The expansion tank 18b is mounted on the support 31b.
  • The expansion tank 18c is mounted on the support 31c.
  • That is, the expansion tanks 18a, 18b, and 18c are mounted in the expansion tank unit housing 31 to be aligned in the vertical direction.
  • A pipe 32a is connected to a lower portion of the expansion tank 18a.
  • A pipe 32b is connected to a lower portion of the expansion tank 18b.
  • A pipe 32c is connected to a lower portion of the expansion tank 18c.
  • The pipes 32a, 32b, and 32c are assembled to a pipe 32 and connected to the low-temperature side second solenoid valve 17.
  • The pipes 32a, 32b, and 32c are connected to the lower portions of the expansion tanks 18a, 18b, and 18c so as to reliably collect refrigerating machine oil.
  • Although a case having a single low-temperature side second solenoid valve 17 will be described in Embodiment 1, the present invention is not limited thereto, and the low-temperature side second solenoid valve 17 may be provided to each of the expansion tanks 18a, 18b, and 18c.
  • Further, the expansion tanks 18a, 18b, and 18c, which are stored in the expansion tank unit housing 31, may be stacked upon one another.
  • As described later, the expansion tanks 18a, 18b, and 18c each have an outer diameter of 270 mm (a thickness of 8 mm) and a length of approximately 1500 mm.
  • With the expansion tanks 18a, 18b, and 18c disposed to be aligned in the vertical direction, the depth of the expansion tank unit housing 31 is approximately 400 mm.
  • The depth of the high-temperature side housing 19 and the low-temperature side housing 20 is approximately 800 mm.
  • A suction space of 300 mm is secured for the high-temperature side condenser 2 and the auxiliary capacitor 6.
  • It is therefore possible to install the expansion tank unit housing 31 and the outdoor unit 14 in a space of approximately 1500 mm.
  • The capacity of the expansion tanks 18 will now be described.
  • Fig. 4 is a diagram illustrating the relationship between the circuit internal volume and the circuit internal pressure in Embodiment 1 of this invention.
  • Fig. 4 illustrates the relationship between the pressure of the refrigerant in the low-temperature side circulation circuit B and the circuit internal volume of the low-temperature side circulation circuit B when the circulation of the refrigerant is stopped in the high-temperature side circulation circuit A and the low-temperature side circulation circuit B and the refrigerant temperature is increased to ambient temperature under the following conditions.
  • The refrigerant in the low-temperature side circulation circuit B is carbon dioxide.
  • The ambient temperature (outside air temperature) of the outdoor unit 14 is 46 degrees Celsius.
  • The nominal output from the low-temperature side compressor 5 of the low-temperature side circulation circuit B is approximately 28 kW (approximately 10 horsepower).
  • The internal volume of the low-temperature side evaporator 12 is approximately 72 liters.
  • The internal volume of the low-temperature side compressor 5, the auxiliary capacitor 6, the low-temperature side condenser 7, and the liquid receiver 9 is approximately 40 liters.
  • If the liquid pipe 15 and the gas pipe 16 connecting the cooling unit 13 and the outdoor unit 14 (hereinafter also referred to as "the extension pipes") have a length of 70 m, the internal volume thereof is approximately 48 liters.
  • That is, if the length of the extension pipes is 70 m, the value resulting from adding the internal volume of the expansion tanks 18a, 18b, and 18c to approximately 160 liters corresponds to the circuit internal volume of the low-temperature side circulation circuit B.
  • As illustrated in Fig. 4, the larger the circuit internal volume of the low-temperature side circulation circuit B is, the smaller the increase in pressure is.
  • For example, if the design pressure of the low-temperature side circulation circuit B is 4.15 MPa, which is equal to the design pressure for the use of R410A, the required circuit internal volume (black triangles in the drawing) is approximately 400 liters.
  • Under the above-described conditions, 240 liters corresponding to the difference between 400 liters and 160 liters is required as the total internal volume of the expansion tanks 18.
  • If the three expansion tanks 18a, 18b, and 18c are provided, therefore, the outer diameter and the length thereof are 270 mm (a thickness of 8 mm) and approximately 1500 mm, respectively.
  • Further, if the length of the extension pipes is 35 m, the required circuit internal volume (black rhombi in Fig. 4) is approximately 300 liters.
  • Under the above-described conditions, 140 liters corresponding to the difference between 300 liters and 160 liters is required as the total internal volume of the expansion tanks 18.
  • In this case, two expansion tanks 18 having an outer diameter of 270 mm (a thickness of 8 mm) and a length of approximately 1500 mm may suffice.
  • The internal volume and the number of the expansion tanks 18 are not limited to those of the above-described configurations, and may be selected as appropriate in accordance with the necessary internal volume.
  • Herein, if carbon dioxide is used as the refrigerant in the low-temperature side circulation circuit B, the pressure loss is small, and thus it is possible to make the pipe diameter of the gas pipe 16 smaller than that in a case using an HFC refrigerant.
  • In a refrigeration apparatus having a refrigeration capacity of 28 kW, for example, the pipe diameter of the gas pipe 16 is 31.75 mm if R410A is used, whereas it is possible to set the pipe diameter of the gas pipe 16 to 19.05 mm if carbon dioxide is used.
  • Even in the case using carbon dioxide, however, if the pipe diameter is set to the pipe diameter for the case using the HFC refrigerant (31.75 mm) so as to secure the pipe internal volume, it is possible to increase the internal volume of the extension pipes.
  • For example, if the pipe diameter of the gas pipe 16 is changed from 19.05 mm to 31.75 mm when the length of the extension pipes is 70 m, the internal volume is increased by approximately 40 liters.
  • Accordingly, it is possible to reduce the internal volume of the expansion tanks 18.
  • Although the capacity of the expansion tanks 18 has been calculated on the assumption that the ambient temperature is 46 degrees Celsius under the above-described conditions, the internal volume and the number of the expansion tanks 18 may be selected as appropriate in accordance with the temperature environment in which the refrigeration apparatus is used.
  • For example, if the ambient temperature is approximately 32 degrees Celsius, the capacity or the number of the expansion tanks 18 may be reduced.
  • As described above, with the presence of the expansion tanks 18, it is possible to suppress the increase in pressure of the refrigerant in the low-temperature side circulation circuit B and reduce the design pressure of the low-temperature side circulation circuit B.
  • It is therefore possible to reduce the manufacturing cost of the members forming the low-temperature side circulation circuit B.
  • For example, if the design pressure of the low-temperature side circulation circuit B is set to 8.5 MPa without the presence of the expansion tanks 18, the specifications of a copper pipe (hairpin) passing through the plate fin tube-type low-temperature side evaporator 12 include a diameter of approximately 9.52 mm (a thickness of 0.8 mm).
  • Meanwhile, if the design pressure is set to 4.15 MPa with the presence of the expansion tanks 18, the specifications of the hairpin in the low-temperature side evaporator 12 include a diameter of approximately 9.52 mm (a thickness of 0.35 mm).
  • It is thus possible to reduce the thickness of the hairpin to about half, reducing the material cost alone to about half.
  • It is similarly possible to reduce the thickness of each of the low-temperature side compressor 5, the auxiliary capacitor 6, the cascade capacitor 8, the liquid receiver 9, the liquid pipe 15, the gas pipe 16, and the expansion tanks 18.
  • That is, the refrigeration apparatus with the low-temperature side circulation circuit B having a design pressure of 4.15 MPa or lower is capable of reducing the manufacturing cost to half or less compared with the refrigeration apparatus with the low-temperature side circulation circuit B having a design pressure of 8.5 MPa.
  • Description will now be given of a control operation of the low-temperature side second solenoid valve 17 that communicates with the expansion tanks 18.
  • Fig. 5 is a flowchart illustrating an operation of the refrigeration apparatus in Embodiment 1 of this invention.
  • Description will be given below based on steps in Fig. 5.
  • (S1)
  • When the low-temperature side compressor 5 is stopped, the low-temperature side controller 26 acquires the pressure on the discharge side of the low-temperature side compressor 5 detected by the low-temperature side high pressure sensor 27 and the pressure on the suction side of the low-temperature side compressor 5 detected by the low-temperature side low pressure sensor 28.
  • The low-temperature side controller 26 then determines whether or not at least one of the pressure on the suction side and the pressure on the discharge side of the low-temperature side compressor 5 is equal to or higher than a preset pressure value P1.
  • If at least one of the pressure on the suction side and the pressure on the discharge side of the low-temperature side compressor 5 is not equal to or higher than the preset pressure value P1, the low-temperature side controller 26 repeats step S1.
  • Herein, the pressure value P1 is set in accordance with, for example, the design pressure of the low-temperature side circulation circuit B. For example, if the design pressure is 4.15 MPa, the pressure value P1 is set to 4 MPa in consideration of measurement errors of the sensors, operating times of the solenoid valves, and so forth.
  • The pressure value P1 corresponds to "a first pressure value" of the present invention.
  • (S2)
  • If at least one of the pressure on the suction side and the pressure on the discharge side of the low-temperature side compressor 5 is equal to or higher than the preset pressure value P1, the low-temperature side controller 26 opens the low-temperature side second solenoid valve 17.
  • Thereby, the refrigerant in the low-temperature side circulation circuit B flows into each of the expansion tanks 18a, 18b, and 18c. That is, the circuit internal volume of the low-temperature side circulation circuit B is increased, and the pressure of the refrigerant is reduced.
  • (S3)
  • The low-temperature side controller 26 determines whether or not the pressure on the suction side and the pressure on the discharge side of the low-temperature side compressor 5 is equal to or lower than a preset pressure value P2.
  • If the pressure on the suction side and the pressure on the discharge side of the low-temperature side compressor 5 is not equal to or lower than the preset pressure value P2, the low-temperature side controller 26 returns to step S2 to maintain the low-temperature side second solenoid valve 17 in the open state.
  • Herein, the pressure value P2 is set to a value lower than the pressure value P1.
  • The pressure value P2 corresponds to "a second pressure value" of the present invention.
  • (S4)
  • If the pressure on the suction side or the pressure on the discharge side of the low-temperature side compressor 5 is equal to or lower than the preset pressure value P2, the low-temperature side controller 26 closes the low-temperature side second solenoid valve 17 and returns to step S1.
  • As described above, if the pressure of the refrigerant is reduced, the low-temperature side second solenoid valve 17 is closed to stop the flow of the refrigerant into the expansion tanks 18. It is thereby possible to collect the refrigerant in a short time when the low-temperature side compressor 5 is restarted.
  • Power supply to the refrigeration apparatus may be stopped for a long time owing to a power failure, for example.
  • The low-temperature side second solenoid valve 17 in Embodiment 1 is a solenoid valve that is closed when supplied with power. Even when the low-temperature side compressor 5 is stopped owing to a power failure or the like, therefore, the low-temperature side second solenoid valve 17 is open, increasing the circuit internal volume of the low-temperature side circulation circuit B and reducing the pressure of the refrigerant.
  • (Restart of Low-Temperature Side Compressor 5)
  • When the low-temperature side compressor 5 is restarted, the low-temperature side controller 26 opens the low-temperature side second solenoid valve 17 for a preset time.
  • That is, the low-temperature side controller 26 opens the low-temperature side second solenoid valve 17 when the low-temperature side compressor 5 is started, and closes the low-temperature side second solenoid valve 17 after the lapse of a preset time.
  • It is thereby possible to collect the refrigerant in the expansion tanks 18 into the low-temperature side circulation circuit B.
  • The operations of steps S3 and S4 described above may be omitted to maintain the low-temperature side second solenoid valve 17 in the open state. Further, the low-temperature side second solenoid valve 17 may be closed after the lapse of a preset time from the restart of the low-temperature side compressor 5.
  • As described above, Embodiment 1 includes the expansion tanks 18 connected to the pipe between the low-temperature side evaporator 12 and the low-temperature side compressor 5 via the low-temperature side second solenoid valve 17.
  • It is therefore possible to suppress the increase in pressure of the refrigerant in the low-temperature side circulation circuit B when the low-temperature side compressor 5 of the low-temperature side circulation circuit B is stopped.
  • Further, when the low-temperature side compressor 5 of the low-temperature side circulation circuit B is stopped or restarted, it is possible to suppress the increase in pressure of the refrigerant in the low-temperature side circulation circuit B without operating the high-temperature side compressor 1 of the high-temperature side circulation circuit A.
  • It is also possible to reduce the design pressure of the low-temperature side circulation circuit B.
  • Further, if carbon dioxide is used as the refrigerant in the low-temperature side circulation circuit B, it is possible to set the design pressure of the low-temperature side circulation circuit B to 4.15 MPa, which is equal to the design pressure in the case using the R410A refrigerant.
  • Therefore, materials employed in a case using the versatile HFC refrigerant are usable in the low-temperature side compressor 5, the auxiliary capacitor 6, the cascade capacitor 8, the liquid receiver 9, the low-temperature side evaporator 12 (a showcase or a unit cooler), the liquid pipe 15, the gas pipe 16, and the expansion tanks 18, which are components of the low-temperature side circulation circuit B.
  • It is therefore possible to substantially reduce the increase in cost of the model using the HFC refrigerant by using the carbon dioxide refrigerant capable of addressing global warming.
  • Further, when the low-temperature side compressor 5 of the low-temperature side circulation circuit B is stopped or restarted, it is unnecessary to uselessly operate the high-temperature side compressor 1 of the high-temperature side circulation circuit A.
  • Further, when the low-temperature side compressor 5 of the low-temperature side circulation circuit B is stopped (thermo-off) and thereafter restarted, it is unnecessary to restart the low-temperature side compressor 5 after the lapse of a predetermined time from the start of the high-temperature side compressor 1 of the high-temperature side circulation circuit A. Therefore, the pull-down speed is not reduced.
  • Further, since the low-temperature side second solenoid valve 17 is a solenoid valve that is closed when supplied with power, it is possible to suppress the increase in pressure of the refrigerant in the low-temperature side circulation circuit B even if power supply to the refrigeration apparatus is stopped for a long time owing to a power failure or the like.
  • Embodiment 2
  • Fig. 6 is a configuration diagram of a refrigeration apparatus in Embodiment 2 of this invention.
  • As illustrated in Fig. 6, a pipe 33a is inserted in the expansion tank 18a from an upper portion of the expansion tank 18a. An end portion of the pipe 33a is disposed at a position near the bottom of the expansion tank 18a.
  • A pipe 33b is inserted in the expansion tank 18b from an upper portion of the expansion tank 18b. An end portion of the pipe 33b is disposed at a position near the bottom of the expansion tank 18b.
  • A pipe 33c is inserted in the expansion tank 18c from an upper portion of the expansion tank 18c. An end portion of the pipe 33c is disposed at a position near the bottom of the expansion tank 18c.
  • The pipes 33a, 33b, and 33c are assembled to a pipe 33 and connected to the low-temperature side second solenoid valve 17.
  • The end portions of the pipes 33a, 33b, and 33c are disposed at the positions near the bottoms of the expansion tanks 18a, 18b, and 18c so as to reliably collect the refrigerating machine oil.
  • The other configurations and operations are similar to those of Embodiment 1 described above.
  • Effects similar to those of Embodiment 1 are also obtainable in Embodiment 2.
  • Embodiment 3
  • Fig. 7 is a configuration diagram of a refrigeration apparatus in Embodiment 3 of this invention.
  • As illustrated in Fig. 7, an expansion tank table 35 is provided below the common table 21 for the high-temperature side housing 19 and the low-temperature side housing 20.
  • The expansion tanks 18a, 18b, and 18c are mounted on the expansion tank table 35.
  • That is, the expansion tank table 35 is disposed below and adjacent to the high-temperature side housing 19 and the low-temperature side housing 20, and the expansion tanks 18a, 18b, and 18c are mounted on the expansion tank table 35 to be aligned in the horizontal direction.
  • The expansion tank table 35 corresponds to "an expansion tank unit" of the present invention.
  • A pipe 34a is connected to a lower portion of the expansion tank 18a.
  • A pipe 34b is connected to a lower portion of the expansion tank 18b.
  • A pipe 34c is connected to a lower portion of the expansion tank 18c.
  • The pipes 34a, 34b, and 34c are assembled to a pipe 34 and connected to the low-temperature side second solenoid valve 17.
  • The pipes 34a, 34b, and 34c are connected to the lower portions of the expansion tanks 18a, 18b, and 18c so as to reliably collect the refrigerating machine oil.
  • The other configurations and operations are similar to those of Embodiment 1 described above.
  • Effects similar to those of Embodiment 1 are also obtainable in Embodiment 3.
  • Further, since the expansion tank table 35 is provided below the common table 21 for the high-temperature side housing 19 and the low-temperature side housing 20, it is possible to make the installation widths (depths) of the expansion tanks 18a and the outdoor unit 14 less than those in Embodiment 1 described above.
  • For example, if the outer diameter of each of the expansion tanks 18 is 300 mm or less, it is possible to set the depth of the outdoor unit 14 to 1000 mm or less.
  • It is therefore possible to provide a compact refrigeration apparatus despite the presence of the expansion tanks 18.
  • Embodiment 4
  • Fig. 8 is a configuration diagram of a refrigeration apparatus in Embodiment 4 of this invention.
  • As illustrated in Fig. 8, a pipe 36a is inserted in the expansion tank 18a from an upper portion of the expansion tank 18a. An end portion of the pipe 36a is disposed at a position near the bottom of the expansion tank 18a.
  • A pipe 36b is inserted in the expansion tank 18b from an upper portion of the expansion tank 18b. An end portion of the pipe 36b is disposed at a position near the bottom of the expansion tank 18b.
  • A pipe 36c is inserted in the expansion tank 18c from an upper portion of the expansion tank 18c. An end portion of the pipe 36c is disposed at a position near the bottom of the expansion tank 18c.
  • The pipes 36a, 36b, and 36c are assembled to a pipe 36 and connected to the low-temperature side second solenoid valve 17.
  • The end portions of the pipes 36a, 36b, and 36c are disposed at the positions near the bottoms of the expansion tanks 18a, 18b, and 18c so as to reliably collect the refrigerating machine oil.
  • The other configurations and operations are similar to those of Embodiment 3 described above.
  • Effects similar to those of Embodiment 3 are also obtainable in Embodiment 4.
  • Embodiment 5
  • In Embodiments 1 to 4 described above, the description has been given of the refrigeration apparatus in which the high-temperature side circulation circuit A and the low-temperature side circulation circuit B are cascade-connected. In Embodiment 5, description will be given of a refrigeration apparatus that performs two-stage compression.
  • Fig. 9 is a refrigerant circuit diagram of the refrigeration apparatus in Embodiment 5 of this invention.
  • As illustrated in Fig. 9, the refrigeration apparatus of Embodiment 5 includes a circulation circuit in which a low-stage side compressor 55, a high-stage side compressor 51, an intermediate cooler 54, a low-stage side first solenoid valve 57, a low-stage side first flow control valve 56, and a low-stage side evaporator 58 are sequentially connected by pipes to circulate a refrigerant therethrough.
  • The refrigeration apparatus of Embodiment 5 further includes an intermediate pressure circuit that branches from an outlet side of a gas cooler 52 and supplies the refrigerant passed through an intermediate cooling flow control valve 53 and the intermediate cooler 54 and reduced in pressure to between the low-stage side compressor 55 and the high-stage side compressor 51.
  • A pipe between the low-stage side evaporator 58 and the low-stage side compressor 55 is connected to an expansion tank 63a, an expansion tank 63b, and an expansion tank 63c via a low-stage side second solenoid valve 62.
  • A carbon dioxide (CO2) refrigerant having a global warming potential (GWP) of 1 is used as the refrigerant circulated through the circulation circuit and the intermediate pressure circuit of the refrigeration apparatus in Embodiment 5.
  • A low-stage side high pressure sensor 64 detects the pressure on a discharge side of the low-stage side compressor 55.
  • A low-stage side low pressure sensor 65 detects the pressure on a suction side of the low-stage side compressor 55.
  • The low-stage side first flow control valve 56, the low-stage side first solenoid valve 57, and the low-stage side evaporator 58 are stored in a low-stage side cooling unit 59.
  • The low-stage side cooling unit 59 is used as a refrigerator-freezer showcase or a unit cooler, for example.
  • The low-stage side cooling unit 59 is connected to the circulation circuit by a low-stage side liquid pipe 60 and a low-stage side gas pipe 61.
  • The low-stage side second solenoid valve 62 is a solenoid valve that is closed when supplied with power.
  • The low-stage side second solenoid valve 62 is controlled by a controller 66.
  • The internal volume and the number of the expansion tanks 63a, 63b, and 63c (hereinafter simply referred to as "the expansion tanks 63" where no distinction is made therebetween) may be selected as appropriate based on the relationship between the circuit internal volume and the circuit internal pressure and the design pressure with the application of the technical concept described in Embodiment 1.
  • The low-stage side compressor 55 corresponds to "a first-stage compressor" of the present invention.
  • The high-stage side compressor 51 corresponds to "a second-stage compressor" of the present invention.
  • The gas cooler 52 corresponds to "a radiator" of the present invention.
  • The low-stage side first flow control valve 56 corresponds to "an expansion device" of the present invention.
  • The low-stage side evaporator 58 corresponds to "an evaporator" of the present invention.
  • The low-stage side second solenoid valve 62 corresponds to "an opening and closing valve" of the present invention.
  • The controller 66 corresponds to "a controller" of the present invention.
  • Description will now be given of an operation of the refrigeration apparatus in Embodiment 5.
  • Fig. 10 is a Mollier chart illustrating the operation of the refrigeration apparatus in Embodiment 5 of this invention.
  • A gas-phase refrigerant at a low pressure flowing from the low-stage side evaporator 58 (point F in Fig. 10) is suctioned by the low-stage side compressor 55 and compressed to an intermediate pressure.
  • Superheated vapor discharged from the low-stage side compressor 55 (point G in Fig. 10) joins a refrigerant at an intermediate pressure flowing from the intermediate cooler 54 (point H in Fig. 10) and enters the high-stage side compressor 51.
  • The gas refrigerant compressed by the high-stage side compressor 51 (point J in Fig. 10) is cooled by the gas cooler 52 to be slightly subcooled (point K in Fig. 10).
  • Most of the refrigerant flowing from the gas cooler 52 passes through a high-pressure side of the intermediate cooler 54 to be further subcooled (point M in Fig. 10), and flows into the low-stage side first flow control valve 56.
  • The subcooled liquid refrigerant flowing into the low-stage side first flow control valve 56 is reduced in pressure and becomes a two-phase gas-liquid refrigerant (point Q in Fig. 10).
  • The two-phase gas-liquid refrigerant at a low temperature and low pressure flows into the low-stage side evaporator 58.
  • In the low-stage side evaporator 58, the refrigerant evaporates by exchanging heat with a fluid (e.g., air), and becomes a gas-phase refrigerant at a high temperature and low pressure.
  • In this process, a cooling target space is cooled in the low-stage side cooling unit 59.
  • The gas-phase refrigerant at a low pressure flowing from the low-stage side evaporator 58 (point F in Fig. 10) is again suctioned by the low-stage side compressor 55.
  • Meanwhile, the refrigerant branching from the outlet side of the gas cooler 52 becomes a refrigerant reduced in pressure to the intermediate pressure by the intermediate cooling flow control valve 53 (point N in Fig. 10). The refrigerant at the intermediate pressure flows into an intermediate-pressure side of the intermediate cooler 54.
  • The refrigerant flowing into the intermediate-pressure side of the intermediate cooler 54 exchanges heat with the refrigerant flowing on the high-pressure side of the intermediate cooler 54 to increase the degree of subcooling of the high-pressure gas flowing toward the low-stage side first solenoid valve 57 (point K in Fig. 10) (point M in Fig. 10).
  • From the intermediate-pressure side of the intermediate cooler 54, in which the refrigerant liquid and the vapor coexist, vapor close to a quality saturation state (point H in Fig. 10) is suctioned by the high-stage side compressor 51.
  • Description will now be given of a control operation of the low-stage side second solenoid valve 62 that communicates with the expansion tanks 63.
  • A technical concept similar to that of the control operation of the low-temperature side second solenoid valve 17 in Embodiment 1 described above is applicable to the control operation of the low-stage side second solenoid valve 62.
  • Fig. 11 is a flowchart illustrating the operation of the refrigeration apparatus in Embodiment 5 of this invention.
  • Description will be given below based on steps in Fig. 11.
  • (S11)
  • When the low-stage side compressor 55 is stopped, the controller 66 acquires the pressure on the discharge side of the low-stage side compressor 55 detected by the low-stage side high pressure sensor 64 and the pressure on the suction side of the low-stage side compressor 55 detected by the low-stage side low pressure sensor 65.
  • The controller 66 then determines whether or not at least one of the pressure on the suction side and the pressure on the discharge side of the low-stage side compressor 55 is equal to or higher than a preset pressure value P1.
  • If at least one of the pressure on the suction side and the pressure on the discharge side of the low-stage side compressor 55 is not equal to or higher than the preset pressure value P1, the controller 66 repeats step S11.
  • Herein, the pressure value P1 is set in accordance with, for example, the design pressure of the circulation circuit. For example, if the design pressure is 4.15 MPa, the pressure value P1 is set to 4 MPa in consideration of measurement errors of the sensors, operating times of the solenoid valves, and so forth.
  • The pressure value P1 corresponds to "a first pressure value" of the present invention.
  • (S12)
  • If at least one of the pressure on the suction side and the pressure on the discharge side of the low-stage side compressor 55 is equal to or higher than the preset pressure value P1, the controller 66 opens the low-stage side second solenoid valve 62.
  • Thereby, the refrigerant in the circulation circuit flows into each of the expansion tanks 63a, 63b, and 63c. That is, the circuit internal volume of the circulation circuit is increased, and the pressure of the refrigerant is reduced.
  • (S13)
  • The controller 66 determines whether or not the pressure on the suction side and the pressure on the discharge side of the low-stage side compressor 55 is equal to or lower than a preset pressure value P2.
  • If the pressure on the suction side and the pressure on the discharge side of the low-stage side compressor 55 is not equal to or lower than the preset pressure value P2, the controller 66 returns to step S12 to maintain the low-stage side second solenoid valve 62 in the open state.
  • Herein, the pressure value P2 is set to a value lower than the pressure value P1.
  • The pressure value P2 corresponds to "a second pressure value" of the present invention.
  • (S14)
  • If the pressure on the suction side or the pressure on the discharge side of the low-stage side compressor 55 is equal to or lower than the preset pressure value P2, the controller 66 closes the low-stage side second solenoid valve 62 and returns to step S11.
  • As described above, if the pressure of the refrigerant is reduced, the low-stage side second solenoid valve 62 is closed to stop the flow of the refrigerant into the expansion tanks 63. It is thereby possible to collect the refrigerant in a short time when the low-stage side compressor 55 is restarted.
  • Power supply to the refrigeration apparatus may be stopped for a long time owing to a power failure, for example.
  • The low-stage side second solenoid valve 62 in Embodiment 5 is a solenoid valve that is closed when supplied with power. Even when the low-stage side compressor 55 is stopped owing to a power failure or the like, therefore, the low-stage side second solenoid valve 62 is open, increasing the circuit internal volume of the circulation circuit and reducing the pressure of the refrigerant.
  • (Restart of Low-Stage Side Compressor 55)
  • When the low-stage side compressor 55 is restarted, the controller 66 opens the low-stage side second solenoid valve 62 for a preset time.
  • That is, the controller 66 opens the low-stage side second solenoid valve 62 when the low-stage side compressor 55 is started, and closes the low-stage side second solenoid valve 62 after the lapse of a preset time.
  • It is thereby possible to collect the refrigerant in the expansion tanks 63 into the circulation circuit.
  • The operations of steps S13 and S14 described above may be omitted to maintain the low-stage side second solenoid valve 62 in the open state. Further, the low-stage side second solenoid valve 62 may be closed after the lapse of a preset time from the restart of the low-stage side compressor 55.
  • As described above, Embodiment 5 includes the expansion tanks 63 connected to the pipe between the low-stage side evaporator 58 and the low-stage side compressor 55 via the low-stage side second solenoid valve 62.
  • It is therefore possible to suppress the increase in pressure of the refrigerant in the circulation circuit when the low-stage side compressor 55 of the circulation circuit is stopped.
  • Further, it is possible to reduce the design pressure of the circulation circuit. It is therefore possible to reduce the manufacturing cost of the members forming the circulation circuit.
  • Further, since the low-stage side second solenoid valve 62 is a solenoid valve that is closed when supplied with power, it is possible to suppress the increase in pressure of the refrigerant in the circulation circuit even if power supply to the refrigeration apparatus is stopped for a long time owing to a power failure or the like.
  • Reference Signs List
    • 1 high-temperature side compressor 2 high-temperature side condenser 3 high-temperature side expansion valve 4 high-temperature side evaporator 5 low-temperature side compressor 6
    • auxiliary capacitor 7 low-temperature side condenser 8
    • cascade capacitor 9 liquid receiver 10 low-temperature side flow control valve 11 low-temperature side first solenoid valve 12 low-temperature side evaporator 13 cooling unit 14 outdoor unit 15
    • liquid pipe 16 gas pipe 17 low-temperature side second solenoid valve 18a expansion tank 18b expansion tank 18c
    • expansion tank 19 high-temperature side housing 20 low-temperature side housing 21 common table 22 high-temperature side fan 23 low-temperature side fan 24 high-temperature side controller 26 low-temperature side controller 27 low-temperature side high pressure sensor 28 low-temperature side low pressure sensor 30
    • expansion tank unit table 31 expansion tank unit housing 31b
    • support 31c support 32 pipe 32a pipe 32b pipe 32c
    • pipe 33 pipe 33a pipe 33b pipe 33c pipe 34 pipe 34a
    • pipe 34b pipe 34c pipe 35 expansion tank table 36 pipe
    • 36a pipe 36b pipe 36c pipe 51 high-stage side compressor
    • 52 gas cooler 53 intermediate cooling flow control valve54
    • intermediate cooler 55 low-stage side compressor 56 low-stage side first flow control valve 57 low-stage side first solenoid valve
    • 58 low-stage side evaporator 59 low-stage side cooling unit
    • 60 low-stage side liquid pipe61 low-stage side gas pipe 62 low-stage side second solenoid valve 63 expansion tank 63a expansion tank 63b expansion tank 63c expansion tank 64 low-stage side high pressure sensor 65 low-stage side low pressure sensor 66
    • controller A high-temperature side circulation circuit B low-temperature side circulation circuit

Claims (9)

  1. A refrigeration apparatus comprising:
    a first circulation circuit (A) including a first compressor (1), a first condenser (2), a first expansion device (3), and a first evaporator (4) sequentially connected by piping to circulate a refrigerant therethrough;
    a second circulation circuit (B) including a second compressor (5), a second condenser (7), a second expansion device (10), and a second evaporator (12) sequentially connected by piping to circulate a refrigerant therethrough;
    a cascade capacitor (8) formed of the first evaporator (4) and the second condenser (7) to exchange heat between the refrigerant flowing through the first evaporator (4) and the refrigerant flowing through the second condenser (7);
    an opening and closing valve (17);
    a plurality of expansion tanks (18a, 18b, 18c) connected to a pipe between the second evaporator (12) and the second compressor (5) via the opening and closing valve (17);
    an expansion tank unit (31); and
    a controller (26) configured to control the opening and closing valve (17),
    wherein the first compressor (1), the first condenser (2), the first expansion device (3), the first evaporator (4), the second compressor (5), and the second condenser (7) are mounted in an outdoor unit (14),
    wherein the plurality of expansion tanks (18a, 18b, 18c) are mounted in the expansion tank unit (31), and
    wherein the controller (26)
    opens the opening and closing valve (17) if at least one of a pressure on a suction side and a pressure on a discharge side of the second compressor (5) is equal to or higher than a first pressure value, and closes the opening and closing valve (17) if the pressure on the suction side and the pressure on the discharge side of the second compressor (5) are equal to or lower than a second pressure value that is lower than the first pressure value, when the second compressor (5) is stopped, and
    opens the opening and closing valve (17) for a preset time when the second compressor (5) is restarted.
  2. The refrigeration apparatus of claim 1, wherein the expansion tank unit (31) is disposed beside and spaced from the outdoor unit (14), and
    wherein the plurality of expansion tanks (18a, 18b, 18c) are mounted in the expansion tank unit (31) to be aligned in a vertical direction.
  3. The refrigeration apparatus of claim 1, wherein the expansion tank unit (31) is disposed below and adjacent to the outdoor unit (14), and
    wherein the plurality of expansion tanks (18a, 18b, 18c) are mounted in the expansion tank unit (31) to be aligned in a horizontal direction.
  4. The refrigeration apparatus of claim 1 or 2, wherein pipes (32) connecting the plurality of expansion tanks (18a, 18b, 18c) and the opening and closing valve (17) have respective end portions on a side of the plurality of expansion tanks (18a, 18b, 18c) connected to respective lower portions of the plurality of expansion tanks (18a, 18b, 18c).
  5. The refrigeration apparatus of claim 1 or 2, wherein pipes (32) connecting the plurality of expansion tanks (18a, 18b, 18c) and the opening and closing valve (17) have respective end portions on a side of the plurality of expansion tanks (18a, 18b, 18c) inserted from respective upper portions of the plurality of expansion tanks (18a, 18b, 18c) and disposed in respective bottom portions of the plurality of expansion tanks (18a, 18b, 18c).
  6. The refrigeration apparatus of any one of claims 1 to 5, wherein the opening and closing valve (17) is a solenoid valve that is closed when supplied with power.
  7. The refrigeration apparatus of any one of claims 1 to 6, wherein the refrigerant circulated through the second circulation circuit (B) is carbon dioxide.
  8. The refrigeration apparatus of any one of claims 1 to 6, wherein the refrigerant circulated through the second circulation circuit (B) is carbon dioxide, and
    wherein a diameter of the pipe (16) between the second evaporator (12) and the second compressor (5) is equal to a diameter of a pipe for use of HFC as the refrigerant circulated through the second circulation circuit (B).
  9. A refrigeration apparatus comprising:
    a circulation circuit including a first-stage compressor (55), a second-stage compressor (51), a radiator (52), an expansion device (56), and an evaporator (58) sequentially connected by piping to circulate a refrigerant therethrough;
    an intermediate pressure circuit branching from an outlet side of the radiator (52) to reduce a pressure of the refrigerant and supply the refrigerant to between the first-stage compressor (55) and the second-stage compressor (51);
    an opening and closing valve (17);
    an expansion tank (63a, 63b, 63c) connected to a pipe between the evaporator (58) and the second-stage compressor (51) via the opening and closing valve (62); and
    a controller (66) configured to control the opening and closing valve (62), wherein the controller (66)
    opens the opening and closing valve (62) if at least one of a pressure on a suction side and a pressure on a discharge side of the second-stage compressor (51) is equal to or higher than a first pressure value, and closes the opening and closing valve (17, 62) if the pressure on the suction side and the pressure on the discharge side of the second-stage compressor (51) are equal to or lower than a second pressure value that is lower than the first pressure value, when the second-stage compressor (51) is stopped, and
    opens the opening and closing valve (62) for a preset time when the second-stage compressor (51) is restarted.
EP12886969.0A 2012-10-22 2012-10-22 Freezing device Active EP2910872B1 (en)

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JPWO2014064744A1 (en) 2016-09-05
EP2910872A1 (en) 2015-08-26
JP5819006B2 (en) 2015-11-18
EP2910872A4 (en) 2016-10-19
WO2014064744A1 (en) 2014-05-01

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