US20090044564A1 - Refrigerating Apparatus - Google Patents

Refrigerating Apparatus Download PDF

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Publication number
US20090044564A1
US20090044564A1 US12/224,086 US22408607A US2009044564A1 US 20090044564 A1 US20090044564 A1 US 20090044564A1 US 22408607 A US22408607 A US 22408607A US 2009044564 A1 US2009044564 A1 US 2009044564A1
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Prior art keywords
refrigerant
compression mechanism
gas
pressure side
volume ratio
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US12/224,086
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English (en)
Inventor
Masakazu Okamoto
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Daikin Industries Ltd
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Daikin Industries Ltd
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Assigned to DAIKIN INDUSTRIES, LTD. reassignment DAIKIN INDUSTRIES, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: OKAMOTO, MASAKAZU
Publication of US20090044564A1 publication Critical patent/US20090044564A1/en
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F25B1/04—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B13/00—Compression machines, plants or systems, with reversible cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2309/00—Gas cycle refrigeration machines
    • F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
    • F25B2309/061—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide with cycle highest pressure above the supercritical pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
    • F25B2313/027—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means
    • F25B2313/0272—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means using bridge circuits of one-way valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
    • F25B2313/027—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means
    • F25B2313/02741—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means using one four-way valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/13—Economisers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/23—Separators

Definitions

  • the present invention relates to a refrigerating apparatus including a refrigerant circuit including a gas-liquid separator for performing two-stage compression/two-stage expansion refrigeration cycle utilizing of CO 2 refrigerant at high pressure as that at its critical pressure.
  • refrigerating apparatuses including a refrigerant circuit are widely applied to air conditioners and the like.
  • Patent Document 1 discloses an air conditioner including a refrigerant circuit including a gas-liquid separator for performing a two-stage compression/two-stage expansion refrigeration cycle.
  • the refrigerant circuit of this air conditioner includes a compressor, a first heat exchanger, a first expansion valve, a gas-liquid separator, a second expansion valve, and a second heat exchanger.
  • the compressor is of two-stage compression type in which a low pressure side compression mechanism and a high pressure side compression mechanism are connected by means of a drive shaft.
  • the gas-liquid separator is so composed to separate intermediate-pressure refrigerant in a gas-liquid two-phase state into liquid refrigerant and gas refrigerant.
  • refrigerant discharged form the compressor flows into the first heat exchanger.
  • the refrigerant release heat to the air.
  • the refrigerant having passed through the first heat exchanger is reduced in pressure up to intermediate pressure through the first expansion valve and flows then into the gas-liquid separator.
  • the intermediate-pressure refrigerant in the gas-liquid two-phase state is separated into the gas refrigerant and the liquid refrigerant.
  • the liquid refrigerant thus separated in the gas-liquid separator is reduced in pressure up to low pressure through the second expansion valve and flows then into the second heat exchanger.
  • the refrigerant absorbs heat from the air to be evaporated. In this way, the indoor cooling is performed.
  • the refrigerant having passed through the second heat exchanger is sucked into the compressor to be compressed up to intermediate pressure in the low pressure side compression mechanism.
  • the refrigerant discharged from the low pressure side compression mechanism is mixed with the gas refrigerant separated in the gas-liquid separator.
  • the air conditioner performs generally-called intermediate pressure gas injection in which the intermediate-pressure gas refrigerant is mixed with the refrigerant discharged from the low pressure side compression mechanism. Thereafter, the thus mixed refrigerant is compressed up to high pressure in the high pressure side compression mechanism and is then discharged from the compressor again.
  • the air conditioner of Patent Document 1 performs the intermediate pressure gas injection to lower the temperature of the refrigerant discharged from the compressor for reducing the power required for driving the compressor, thereby increasing the COP (coefficient of performance) of the air conditioner.
  • Patent Document 2 discloses an air conditioner in which the aforementioned intermediate pressure gas injection is performed with CO 2 refrigerant filled in a refrigerant circuit. This air conditioner performs a generally-called supercritical cycle in which the refrigerant discharged from the compressor is compressed over its critical pressure.
  • Patent Document 1 Japanese Unexamined Patent Application Publication 7-110167
  • Patent Document 2 Japanese Unexamined Patent Application Publication 2001-241797
  • the volume (displacement volume) of each compression mechanism of the two-stage compression type compressor is so designed to attain efficient two-stage compression.
  • the refrigerant after being compressed up to its supercritical pressure and releasing heat in an heat exchanger may be at the supercritical pressure yet in the gas-liquid separator.
  • the refrigerant at supercritical pressure (in the critical state) in the gas-liquid separator is difficult to be separated into the gas refrigerant and the liquid refrigerant. This inhibits sending of only the gas refrigerant to the intermediate-pressure refrigerant in the compressor to inhibit the aforementioned intermediate pressure gas injection. Accordingly, desired effects by the intermediate pressure gas injection cannot be attained to invite lowering of the COP of the air conditioner.
  • the present invention has been made in view of the foregoing and has its object of enabling operation at an optimal COP in a refrigerating apparatus performing two-stage compression/two-stage expansion refrigeration cycle using CO 2 refrigerant.
  • a first aspect of the present invention premises a refrigerating apparatus including a refrigerant circuit for performing a two-stage compression/two-stage expansion refrigeration cycle in which CO 2 refrigerant at high pressure is utilized as that at its critical pressure, the refrigerant circuit including: a compressor including a low pressure side compression mechanism and a high pressure side compression mechanism connected to each other by means of a drive shaft; and a gas-liquid separator for separating refrigerant at intermediate pressure into gas refrigerant and liquid refrigerant.
  • a volume ratio of a displacement volume of the high pressure side compression mechanism to that of the low pressure side compression mechanism falls in a range between 0.8 and 1.3, both exclusive.
  • the refrigerant circuit ( 10 ) in the first aspect is filled with CO 2 refrigerant. Further, the compressor ( 30 ) including the low pressure side compression mechanism ( 34 ) and the high pressure side compression mechanism ( 35 ) is provided in the refrigerant circuit ( 10 ). In the refrigerant circuit ( 10 ), the following two-stage compression/two-stage expansion refrigeration cycle is performed.
  • the refrigerant compressed up to its critical pressure in the high pressure side compression mechanism ( 35 ) releases heat in, for example, an indoor heat exchanger, is reduced in pressure up to intermediate pressure, and flows then into the gas-liquid separator ( 15 ).
  • the intermediate-pressure refrigerant is separated into the gas refrigerant and the liquid refrigerant.
  • the liquid refrigerant is reduced in pressure up to low pressure, is evaporated in, for example, an outdoor heat exchanger, and is then sucked into the low pressure side compression mechanism ( 34 ).
  • This refrigerant is compressed up to intermediate pressure in the low pressure side compression mechanism ( 34 ).
  • the gas refrigerant separated in the liquid-gas separator ( 15 ) is introduced into this refrigerant.
  • the aforementioned intermediate pressure gas injection is performed.
  • the refrigerant is compressed up to high pressure (critical pressure) in the high pressure side compression mechanism ( 35 ).
  • the intermediate-pressure refrigerant in the gas-liquid separator may reach its critical pressure in the conventional refrigerating apparatus. If so, the refrigerant in the gas-liquid separator cannot be separated into the gas refrigerant and the liquid refrigerant to inhibit desired intermediate pressure gas injection.
  • the volume ratio of the high pressure side compression mechanism ( 35 ) to the low pressure side compression mechanism ( 34 ) is set greater than 0.8.
  • the volume ratio When the volume ratio is set equal to or smaller than 0.8, the displacement volume of the high pressure side compression mechanism ( 35 ) becomes relatively smaller than that of the low pressure side compression mechanism ( 34 ), thereby increasing the pressure of the intermediate-pressure refrigerant to invite an increase in pressure of the refrigerant in the gas-liquid separator ( 15 ) over its critical pressure.
  • the volume ratio in which the volume ratio is set greater than 0.8, the refrigerant in the gas-liquid separator ( 15 ) can be suppressed at its subcritical pressure.
  • the refrigerant in the gas-liquid separator ( 15 ) is definitely separated into the gas refrigerant and the liquid refrigerant to attain desired effects by the intermediate pressure gas injection.
  • the displacement volume of the high pressure side compression mechanism ( 35 ) is relatively greater than that of the low pressure side compression mechanism ( 34 ).
  • the amount of the refrigerant sucked in the high pressure side compression mechanism ( 35 ) is secured insufficiently to invite lowering of the compression efficiency of the compressor ( 30 ).
  • this aspect of the present invention sets the volume ratio to be smaller than 1.3 to secure a sufficient amount of the refrigerant sucked in the high pressure side compression mechanism ( 35 ), with a result that the refrigerant can be compressed in two stages efficiently.
  • the volume ratio falls in a range between 0.9 and 1.1, both inclusive.
  • the volume ratio of the displacement volume of the high pressure side compression mechanism ( 35 ) to that of the low pressure side compression mechanism ( 34 ) is set in the range between 0.9 and 1.1, both inclusive.
  • the volume ratio exceeding 0.9 definitely makes the refrigerant in the gas-liquid separator ( 15 ) reach its critical pressure. While, the volume ratio not exceeding 1.1 attains further efficient two-stage compression of the refrigerant.
  • the volume ratio is 1.0.
  • the volume of the low pressure side compression mechanism ( 34 ) and that of the high pressure side compression mechanism ( 35 ) are set equal to each other.
  • the low pressure side compression mechanism and the high pressure side compression mechanism are rotary compression mechanisms.
  • the compressor ( 30 ) is so composed that the low pressure side compression mechanism ( 34 ) and the high pressure side compression mechanism ( 35 ) are connected to each other by means of the drive shaft ( 33 ).
  • the volume ratio of the high pressure side compression mechanism ( 35 ) to the low pressure side compression mechanism ( 34 ) is set in the range between 0.8 and 1.3, both exclusive.
  • the volume ratio over 0.8 reduces the pressure of the refrigerant in the gas-liquid separator ( 15 ) lower than its critical pressure. Accordingly, desired intermediate pressure gas injection can be performed in the refrigerant circuit ( 10 ) to increase the COP of the refrigerating apparatus in the present invention.
  • the volume ratio below 1.3 invites no lowering of the compression efficiency accompanied by insufficiency of the amount of the refrigerant sucked in the high pressure side compression mechanism ( 35 ), thereby attaining two-stage compression of the refrigerant.
  • the COP of the refrigerating apparatus can be increased further in the present invention.
  • the volume ratio of the high pressure side compression mechanism ( 35 ) to the low pressure side compression mechanism ( 34 ) is set in the range between 0.9 and 1.1, both inclusive, in the second aspect of the present invention.
  • the volume ratio of the high pressure side compression mechanism ( 35 ) to the low pressure side compression mechanism ( 34 ) is set in further optimum range.
  • the COP of the refrigerating apparatus can be increased further in this aspect.
  • the volume ratio of the low pressure side compression mechanism ( 34 ) to the volume ratio of the high pressure side compression mechanism ( 35 ) are set equal to each other. Accordingly, the low pressure side compression mechanism ( 34 ) and the high pressure side compression mechanism ( 35 ) can be structured according to the same specification in their compression mechanism, thereby contemplating cost reduction and simplification of the compressor ( 30 ).
  • desired intermediate pressure gas injection is performed in the refrigerating apparatus including the compressor ( 30 ) including the two rotary compression mechanisms to thus increase the COP thereof.
  • FIG. 1 is a piping system diagram of a refrigerant circuit in an air conditioner in accordance with one embodiment.
  • FIG. 2 is a piping system diagram for explaining refrigerant flow in a heating operation of the air conditioner.
  • FIG. 3 is a piping system diagram for explaining refrigerant flow in a cooling operation of the air conditioner.
  • FIG. 4 is a graph showing the relationship between the COP and the volume ratio of a high pressure side compression mechanism to a low pressure side compression mechanism.
  • a refrigerating apparatus in accordance with one embodiment composes an air conditioner ( 1 ) performing indoor air conditioning.
  • the air conditioner ( 1 ) is capable of heating and cooling the interior of a room.
  • the air conditioner ( 1 ) includes an indoor unit ( 11 ) installed indoors and an outdoor unit ( 12 ) installed outdoors.
  • the indoor unit ( 11 ) and the outdoor unit ( 12 ) are connected to each other by means of two communication pipes. Accordingly, a refrigerant circuit ( 10 ) is formed across the indoor unit ( 11 ) and the outdoor unit ( 12 ) in the air conditioner ( 1 ).
  • CO 2 refrigerant is filled so that a two-stage compression/two-stage expansion refrigeration cycle is performed with the CO 2 refrigerant at high pressure utilized as that at its critical pressure.
  • an indoor heat exchanger ( 13 ) is provided which is of fin-and-tube type.
  • the indoor air blown by an indoor fan is heat-exchanged with the refrigerant.
  • the outdoor unit ( 12 ) includes a compressor ( 30 ), which will be described later, an outdoor heat exchanger ( 14 ), and a gas-liquid separator ( 15 ).
  • the outdoor heat exchanger ( 14 ) is of fin-and-tube type. In the outdoor heat exchanger ( 14 ), the outdoor air blown by an outdoor fan is heat-exchanged with the refrigerant.
  • the gas-liquid separator ( 15 ) is composed of a cylindrical hermetic container.
  • An inflow pipe ( 15 a ) and a gas injection pipe ( 15 b ) are connected to the gas-liquid separator ( 15 ) so as to pass through the top of the gas-liquid separator ( 15 ).
  • the gas injection pipe ( 15 b ) forms a flow path for introducing gas refrigerant at intermediate pressure into the compressor ( 30 ).
  • An outflow pipe ( 15 c ) is connected to the gas-liquid separator ( 15 ) so as to pass through the lower part of the gas-liquid separator ( 15 ).
  • the intermediate-pressure refrigerant in a gas-liquid two-phase state is separated into gas refrigerant and liquid refrigerant.
  • the outdoor unit ( 12 ) further includes a four-way switching valve ( 16 ), a bridge circuit ( 17 ), a first expansion valve ( 18 ), and a second expansion valve ( 19 ).
  • the four-way switching valve ( 16 ) includes first to fourth ports.
  • the first port is connected to a discharge pipe ( 41 ) of the compressor ( 30 )
  • the second port is connected to the outdoor heat exchanger ( 14 )
  • the third port is connected to the indoor heat exchanger ( 13 )
  • the fourth port is connected to a suction pipe ( 42 ) of the compressor ( 30 ).
  • the four-way switching valve ( 16 ) is exchangeable between a state (the state indicated by solid lines in FIG. 1 ) in which the first port and the second port communicate with each other while the third port and the fourth port communicate with each other and a state (the state indicated by broken lines in FIG. 1 ) in which the first port and the third port communicate with each other while the second port and the fourth port communicate with each other.
  • the bridge circuit ( 17 ) is composed of four pipes in a bridge like combination and four check valves provided at the pipes.
  • the check valves of the bridge circuit ( 17 ) allow the refrigerant to flow only in the directions indicated by the arrows in FIG. 1 .
  • the first expansion valve ( 18 ) and the second expansion valve ( 19 ) are electronic expansion valves of which opening is adjustable.
  • the first expansion valve ( 18 ) is provided in the piping on the inflow side of the gas-liquid separator ( 15 ) while the second expansion valve ( 19 ) is provided in the piping on the outflow side thereof.
  • the compressor ( 30 ) is composed of a generally-called two-stage compression type compressor that compresses refrigerant in two stages by two compression mechanisms.
  • the compressor ( 30 ) includes a cylindrical hermetic casing ( 31 ).
  • An electric motor ( 32 ), a drive shaft ( 33 ), a first compression mechanism ( 34 ), and a second compression mechanism ( 35 ) are accommodated in the casing ( 31 ).
  • the electric motor ( 32 ) is composed of a stator fixed on the inner peripheral face of the casing ( 31 ) and a rotor fixed on the outer peripheral face of the drive shaft ( 33 ).
  • the drive shaft ( 33 ) is supported by a bearing so as to extend vertically.
  • the drive shaft ( 33 ) is rotatable by being driven by the electric motor ( 32 ).
  • the first compression mechanism ( 34 ) is arranged near the bottom of the casing ( 31 ) and serves as a low pressure side compression mechanism.
  • the second compression mechanism ( 35 ) is arranged near the electric motor ( 32 ) and serves as a high pressure side compression mechanism.
  • the first compression mechanism ( 34 ) and the second compression mechanism ( 35 ) are rotary swing type compression mechanisms. Pistons are accommodated in cylindrical cylinder chambers of the compression mechanisms ( 34 , 35 ). Each piston is connected to the drive shaft ( 33 ) so as to be eccentric from the axis of the drive shaft ( 33 ). Accordingly, when the drive shaft ( 33 ) is rotated, each piston of the compression mechanisms ( 34 , 35 ) rotates with their centers being eccentric with respect to the drive shaft ( 33 ). Further, the pistons of the compression mechanisms ( 34 , 35 ) are connected to the drive shaft ( 33 ) so as to be phase-sifted by 180° from each other. This offsets the centrifugal forces of the pistons in operation, thereby suppressing vibration and variation in torque load.
  • the first compression mechanism ( 34 ) is connected on the suction side thereof to the suction pipe ( 42 ) and is connected on the discharge side thereof to one end of an intermediate communication pipe ( 43 ).
  • the second compression mechanism ( 35 ) is connected on the suction side thereof to the other end of the intermediate communication pipe ( 43 ) and is connected on the discharge side thereof to the discharge pipe ( 41 ).
  • the intermediate communication pipe ( 43 ) forms a flow path for introducing the refrigerant after being compressed in the first compression mechanism ( 34 ) into the suction side of the second compression mechanism ( 35 ).
  • the outflow end of the gas injection pipe ( 15 b ) is connected to a U-shape curved part of the intermediate communication pipe ( 43 ).
  • the ratio (volume ratio V2/V1) of the displacement volume V2 of the second compression mechanism ( 35 ) to that V1 of the first compression mechanism ( 34 ) are set in the range between 0.8 and 1.3, both exclusive. This increases the COP (coefficient of performance) of the air conditioner ( 1 ).
  • the relationship between the volume ratio V2/V1 and the COP will be described later in detail.
  • the air conditioner ( 1 ) is capable of performing the following heating and cooling operations.
  • the four-way switching valve ( 16 ) is set as shown in FIG. 2 .
  • Each opening of the first expansion valve ( 18 ) and the second expansion valve ( 19 ) is adjusted appropriately.
  • the refrigerant compressed up to its critical pressure is discharged from the compressor ( 30 ).
  • the refrigerant passes through the four-way switching valve ( 16 ) and then flows into the indoor heat exchanger ( 13 ).
  • the indoor heat exchanger ( 13 ) the refrigerant releases heat to the indoor air. This means indoor heating.
  • the refrigerant flowing out from the indoor heat exchanger ( 13 ) passes through the first expansion valve ( 18 ) to be reduced in pressure up to intermediate pressure and flows then into the gas-liquid separator ( 15 ).
  • the intermediate-pressure refrigerant in the gas-liquid two-phase state is retained. This refrigerant is separated into the gas refrigerant and the liquid refrigerant in the gas-liquid separator ( 15 ).
  • the gas refrigerant retained in the upper part of the gas-liquid separator ( 15 ) flows into the gas injection pipe ( 15 b ).
  • the liquid refrigerant retained in the lower part of the gas-liquid separator ( 15 ) passes through the second expansion valve ( 19 ) to be reduced in pressure up to low pressure and flows then into the outdoor heat exchanger ( 14 ).
  • the refrigerant absorbs heat from the outdoor air to be evaporated. The refrigerant flowing out from the outdoor heat exchanger ( 14 ) is sucked into the compressor ( 30 ).
  • the refrigerant is first sucked into the first compression mechanism ( 34 ) through the suction pipe ( 42 ).
  • the refrigerant is compressed up to intermediate pressure in the first compression mechanism ( 34 ).
  • the refrigerant discharged from the first compression mechanism ( 34 ) flows into the intermediate communication pipe ( 43 ).
  • This discharged refrigerant is mixed with the gas refrigerant flowing out from the gas injection pipe ( 15 b ).
  • the refrigerant flowing out from the intermediate communication pipe ( 43 ) is sucked into the second compression mechanism ( 35 ).
  • the refrigerant is compressed up to its critical pressure.
  • the four-way switching valve ( 16 ) is set as shown in FIG. 3 .
  • Each opening of the first expansion valve ( 18 ) and the second expansion valve ( 19 ) is adjusted appropriately.
  • the refrigerant compressed up to its critical pressure is discharged from the compressor ( 30 ).
  • the refrigerant passes through the four-way switching valve ( 16 ) and flows then into the outdoor heat exchanger ( 14 ).
  • the refrigerant release heat to the outdoor air.
  • the refrigerant flowing out from the outdoor heat exchanger ( 14 ) passes through the first expansion valve ( 18 ) to be reduced in pressure up to intermediate pressure and flows then into the gas-liquid separator ( 15 ).
  • the intermediate-pressure refrigerant in the gas-liquid two-phase state is retained. This refrigerant is separated into the gas refrigerant and the liquid refrigerant in the gas-liquid separator ( 15 ).
  • the gas refrigerant retained in the upper part of the gas-liquid separator ( 15 ) flows into the gas injection pipe ( 15 b ).
  • the liquid refrigerant retained in the lower part of the gas-liquid separator ( 15 ) passes through the second expansion valve ( 19 ) to be reduced in pressure up to low pressure and flows then into the indoor heat exchanger ( 13 ).
  • the indoor heat exchanger ( 13 ) the refrigerant absorbs heat from the indoor air to be evaporated. This means indoor cooling.
  • the refrigerant flowing out from the indoor heat exchanger ( 13 ) is sucked into the compressor ( 30 ).
  • the refrigerant is first sucked into the first compression mechanism ( 34 ) through the suction pipe ( 42 ).
  • the refrigerant is compressed up to intermediate pressure in the first compression mechanism ( 34 ).
  • the refrigerant discharged from the first compression mechanism ( 34 ) flows into the intermediate communication pipe ( 43 ).
  • This discharged refrigerant is mixed with the gas refrigerant flowing out from the gas injection pipe ( 15 b ).
  • the refrigerant flowing out from the intermediate communication pipe ( 43 ) is sucked into the second compression mechanism ( 35 ).
  • the refrigerant is compressed up to its critical pressure.
  • the generally-called intermediate pressure gas injection is performed by mixing the gas refrigerant separated in the gas-liquid separator ( 15 ) with the intermediate-pressure refrigerant in the compressor ( 30 ).
  • this air conditioner ( 1 ) the temperature of the refrigerant discharged from the first compression mechanism ( 34 ) is lowered and the power required for driving the compressor ( 30 ) is reduced, thereby increasing the COP.
  • the volume ratio (V2/V1) of the volume V2 of the second compression mechanism ( 35 ) to that V1 of the first compression mechanism ( 34 ) is set in the optimum range to allow the pressure of the intermediate-pressure refrigerant in the gas-liquid separator ( 15 ) to be lower than its critical pressure, thereby enabling desired intermediate pressure gas injection.
  • FIG. 4 shows the result obtained by examining the above relationship between the volume ratio (V2/V1) and the COP.
  • the COPs in the heating operation and the cooling operation are obtained in air conditioners having volume ratios (V2/V1) different form each other.
  • each COP of the air conditioners is obtained in the heating operation under a temperature condition in the outdoor temperature range (from ⁇ 10° C. to 15° C.) in general winter season and in the cooling operation under a temperature condition in the outdoor temperature range (from 25° C. to 35° C.) in general summer season.
  • the “COP ratio” herein means a relative evaluation of each COP of the air conditioners with various volume ratios with reference to, as a standard, the lowest COP of an air condition with a volume ratio of 0.65 (for example, the COP in the heating operation at an outdoor temperature of 15° C. and the COP in the cooling operation at an outdoor temperature of 25° C.).
  • the air conditioners with volume ratios of 0.8 or smaller have low COPs in the heating operation and the cooling operation. This is because: with a volume ratio of 0.8 or smaller, the displacement volume of the second compression mechanism ( 35 ) is too small relative to that of the first compression mechanism ( 34 ), so that the refrigerant in the gas-liquid separator ( 15 ) exceeds its critical pressure to inhibit separation of the gas refrigerant from the refrigerant in the gas-liquid separator ( 15 ), thereby inhibiting desired intermediate pressure gas injection.
  • the refrigerant in the gas-liquid separator ( 15 ) can be allowed to reach its subcritical pressure to leads to separation of the gas refrigerant from the refrigerant in the gas-liquid separator ( 15 ).
  • the air conditioner with a volume ratio greater than 0.8 can perform desired intermediate pressure gas injection, thereby attaining a high COP.
  • the air conditioner with a volume ratio of 1.3 has low COPs in the heating operation and in the cooling operation under a low outdoor temperature condition. This is because: with a volume ratio of 1.3 or greater, the displacement volume of the second compression mechanism ( 35 ) is too great relative to that of the first compression mechanism ( 34 ), so that an insufficient amount of the refrigerant sucked in the second compression mechanism ( 35 ) is secured. In other words, with a volume ratio of 1.3 or greater, the refrigerant is compressed in two stages inefficiently to increase the power required for driving the compressor ( 30 ) with a result of lowering of the COP. In reverse, the air conditioner with a volume ratio smaller than 1.3 can perform relatively efficient two-stage compression of the refrigerant to attain a high COP.
  • each COP in the cooling operation and in the heating operation is high when the volume ratio is not within the range between 0.9 and 1.1, both inclusive.
  • the volume ratio (V2/V1) of the volume V2 of the second compression mechanism ( 35 ) to that V1 of the first compression mechanism ( 34 ) is preferably within the range between 0.9 and 1.1, both inclusive.
  • the volume ratio is set at 1.0, a high COP can be attained in each of the cooling operation and the heating operation.
  • the volume ratio of the second compression mechanism ( 35 ) to the first compression mechanism ( 34 ) is set within the range between 0.8 and 1.3, both exclusive.
  • the volume ratio is set greater than 0.8, the pressure of the refrigerant in the gas-liquid separator ( 15 ) is allowed to be smaller than its critical pressure. This attains desired intermediate pressure gas injection in the refrigerant circuit ( 10 ) to increase the COP of the air conditioner ( 1 ) in the present embodiment.
  • the volume ratio is set smaller than 1.3, the refrigerant can be compressed in two stages with no lowering of the compression efficiency invited, which is accompanied by an insufficient amount of the refrigerant sucked in the second compression mechanism ( 35 ).
  • the COP of the air conditioner ( 1 ) can be increased further.
  • volume ratio of the second compression mechanism ( 35 ) to the first compression mechanism ( 34 ) is set within the range between 0.9 and 1.1, both inclusive, a high COP can be obtained as shown in FIG. 4 .
  • the compression mechanisms can be structured according to the same specification in their compression mechanism. Hence, the compressor ( 30 ) can be manufactured comparatively easily at low cost.
  • the above embodiment may have any of the following structure.
  • the discharge side of the low pressure side compression mechanism ( 34 ) and the suction side of the high pressure side compression mechanism ( 35 ) are connected by means of the intermediate communication pipe ( 43 ), and the outflow end of the gas injection pipe ( 15 b ) is connected to the intermediate communication pipe ( 43 ).
  • the intermediate-pressure gas refrigerant may be introduced into the casing ( 31 ) in the case where the compressor ( 30 ) is a generally-called intermediate pressure dome type compressor by filling the casing ( 31 ) of the compressor ( 30 ) with the refrigerant discharged from, for example, the low pressure side compression mechanism ( 34 ).
  • the low pressure side compression mechanism ( 34 ) and the high pressure side compression mechanism ( 35 ) are composed of swing type compression mechanisms in the above embodiment but may be rotary piston type compression mechanisms or compression mechanisms each composed of an anchor tooth and a movable tooth (of scroll type, for example).
  • the present invention is useful in refrigerating apparatuses including a refrigerant circuit including a gas-liquid separator for performing two-stage compression/two-state expansion refrigeration cycle utilizing CO 2 refrigerant at high pressure as that at its critical pressure.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)
  • Compression-Type Refrigeration Machines With Reversible Cycles (AREA)
  • Compressors, Vaccum Pumps And Other Relevant Systems (AREA)
US12/224,086 2006-02-28 2007-02-22 Refrigerating Apparatus Abandoned US20090044564A1 (en)

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JP2006053431A JP2007232263A (ja) 2006-02-28 2006-02-28 冷凍装置
JP2006-053431 2006-02-28
PCT/JP2007/053255 WO2007105440A1 (ja) 2006-02-28 2007-02-22 冷凍装置

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EP (1) EP1990587B1 (ja)
JP (1) JP2007232263A (ja)
KR (1) KR20080090528A (ja)
CN (1) CN101384865B (ja)
AU (1) AU2007226005B2 (ja)
ES (1) ES2733021T3 (ja)
TR (1) TR201909681T4 (ja)
WO (1) WO2007105440A1 (ja)

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US20100251741A1 (en) * 2007-11-30 2010-10-07 Daikin Industries, Ltd. Refrigeration apparatus
US20100257894A1 (en) * 2007-11-30 2010-10-14 Daikin Industries, Ltd. Refrigeration apparatus
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US20110030407A1 (en) * 2008-04-22 2011-02-10 Daikin Industries, Ltd. Refrigeration apparatus
US20110162397A1 (en) * 2008-09-29 2011-07-07 Carrier Corporation Flash tank economizer cycle control
US20110203309A1 (en) * 2008-10-01 2011-08-25 Mitsubishi Electric Corporation Refrigerating cycle apparatus
US20110232325A1 (en) * 2008-12-05 2011-09-29 Shuji Furui Refrigerating apparatus
US20140250936A1 (en) * 2011-10-07 2014-09-11 Daikin Industries, Ltd. Heat exchange unit and refrigeration device
US20140305150A1 (en) * 2013-04-15 2014-10-16 Lg Electronics Inc. Air conditioner and method for controlling the same
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US8327661B2 (en) 2007-11-30 2012-12-11 Daikin Industries, Ltd. Refrigeration apparatus
US20100251741A1 (en) * 2007-11-30 2010-10-07 Daikin Industries, Ltd. Refrigeration apparatus
US20100257894A1 (en) * 2007-11-30 2010-10-14 Daikin Industries, Ltd. Refrigeration apparatus
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US8387411B2 (en) 2007-11-30 2013-03-05 Daikin Industries, Ltd. Refrigeration apparatus
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US20110005270A1 (en) * 2008-02-29 2011-01-13 Daikin Industries, Ltd. Refrigeration apparatus
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US20110000246A1 (en) * 2008-02-29 2011-01-06 Daikin Industries, Ltd. Refrigeration apparatus
US20110030407A1 (en) * 2008-04-22 2011-02-10 Daikin Industries, Ltd. Refrigeration apparatus
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US20140250936A1 (en) * 2011-10-07 2014-09-11 Daikin Industries, Ltd. Heat exchange unit and refrigeration device
US10274245B2 (en) * 2011-10-07 2019-04-30 Daikin Industries, Ltd. Heat exchange unit and refrigeration device
US20140305150A1 (en) * 2013-04-15 2014-10-16 Lg Electronics Inc. Air conditioner and method for controlling the same
US9989281B2 (en) * 2013-04-15 2018-06-05 Lg Electronics Inc. Air conditioner and method for controlling the same
US10330350B2 (en) * 2015-12-10 2019-06-25 Gree Electric Appliances, Inc. Of Zhuhai Air conditioning system, compression system with gas secondary injection and judgment and control method thereof

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TR201909681T4 (tr) 2019-07-22
JP2007232263A (ja) 2007-09-13
AU2007226005A1 (en) 2007-09-20
EP1990587A1 (en) 2008-11-12
WO2007105440A1 (ja) 2007-09-20
KR20080090528A (ko) 2008-10-08
ES2733021T3 (es) 2019-11-27
EP1990587A4 (en) 2014-11-19
EP1990587B1 (en) 2019-04-17
AU2007226005B2 (en) 2010-05-20
CN101384865A (zh) 2009-03-11
CN101384865B (zh) 2012-04-18

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