US20110036110A1 - Refrigeration apparatus - Google Patents
Refrigeration apparatus Download PDFInfo
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- US20110036110A1 US20110036110A1 US12/989,440 US98944009A US2011036110A1 US 20110036110 A1 US20110036110 A1 US 20110036110A1 US 98944009 A US98944009 A US 98944009A US 2011036110 A1 US2011036110 A1 US 2011036110A1
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- refrigerant
- temperature
- water
- tube
- heat exchanger
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- 238000005057 refrigeration Methods 0.000 title claims abstract description 186
- 239000003507 refrigerant Substances 0.000 claims abstract description 762
- 230000006835 compression Effects 0.000 claims abstract description 429
- 238000007906 compression Methods 0.000 claims abstract description 429
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 351
- 230000007246 mechanism Effects 0.000 claims abstract description 256
- 230000001953 sensory effect Effects 0.000 claims description 48
- 238000010438 heat treatment Methods 0.000 claims description 24
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical group O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 22
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 11
- 239000001569 carbon dioxide Substances 0.000 claims description 11
- 238000001514 detection method Methods 0.000 claims description 5
- 230000004048 modification Effects 0.000 description 42
- 238000012986 modification Methods 0.000 description 42
- 238000004378 air conditioning Methods 0.000 description 38
- 230000007423 decrease Effects 0.000 description 30
- 238000010586 diagram Methods 0.000 description 28
- 238000001704 evaporation Methods 0.000 description 25
- 230000008020 evaporation Effects 0.000 description 25
- 230000005855 radiation Effects 0.000 description 25
- 230000000694 effects Effects 0.000 description 17
- 230000008859 change Effects 0.000 description 14
- 239000007788 liquid Substances 0.000 description 13
- 238000000926 separation method Methods 0.000 description 12
- 238000001816 cooling Methods 0.000 description 11
- 230000009471 action Effects 0.000 description 10
- 238000004781 supercooling Methods 0.000 description 7
- 230000000903 blocking effect Effects 0.000 description 6
- 238000006073 displacement reaction Methods 0.000 description 6
- 238000011144 upstream manufacturing Methods 0.000 description 5
- 238000000034 method Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000002159 abnormal effect Effects 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 2
- 239000012267 brine Substances 0.000 description 2
- 230000001010 compromised effect Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000002441 reversible effect Effects 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 2
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
- F24D3/00—Hot-water central heating systems
- F24D3/18—Hot-water central heating systems using heat pumps
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
- F24D17/00—Domestic hot-water supply systems
- F24D17/02—Domestic hot-water supply systems using heat pumps
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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
- 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
- F25B30/00—Heat pumps
- F25B30/02—Heat pumps of the compression type
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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
- F25B40/00—Subcoolers, desuperheaters or superheaters
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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
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
- F24D2200/00—Heat sources or energy sources
- F24D2200/16—Waste heat
- F24D2200/24—Refrigeration
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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
- 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
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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
- F25B2339/00—Details of evaporators; Details of condensers
- F25B2339/04—Details of condensers
- F25B2339/047—Water-cooled condensers
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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
- 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
- F25B2400/04—Refrigeration circuit bypassing means
- F25B2400/0405—Refrigeration circuit bypassing means for the desuperheater
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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
- 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
- F25B2400/07—Details of compressors or related parts
- F25B2400/072—Intercoolers therefor
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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
- 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
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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
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/21—Temperatures
- F25B2700/2115—Temperatures of a compressor or the drive means therefor
- F25B2700/21152—Temperatures of a compressor or the drive means therefor at the discharge side of the compressor
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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
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/21—Temperatures
- F25B2700/2116—Temperatures of a condenser
- F25B2700/21161—Temperatures of a condenser of the fluid heated by the condenser
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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
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/21—Temperatures
- F25B2700/2117—Temperatures of an evaporator
- F25B2700/21171—Temperatures of an evaporator of the fluid cooled by the evaporator
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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
- F25B31/00—Compressor arrangements
- F25B31/002—Lubrication
- F25B31/004—Lubrication oil recirculating arrangements
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/12—Hot water central heating systems using heat pumps
Abstract
A refrigeration apparatus performs heat exchange on a water tube system having a water inlet tube leading exterior water to a water branching point, first and second branching water tubes extending from the water branching point, and a water outlet tube leading to the exterior from a convergent point of the first and second branching water tubes. Active refrigerant is in a supercritical state in at least part of a refrigeration cycle. The refrigeration apparatus includes a main expansion mechanism connected to an evaporator, first and second compression elements connected by a first refrigerant tube, a first heat exchanger exchanging heat between the first refrigerant tube and the first branching water tubes, second refrigerant tubes connecting the second compression element and the main expansion mechanism, and a second heat exchanger in which the second refrigerant tubes exchange heat with the second branching water tubes and does not exchange heat with the water inlet tube.
Description
- The present invention relates to a refrigeration apparatus, and particularly relates to a refrigeration apparatus which performs a multi-stage compression-type refrigeration cycle using refrigerant that operates including the process of a supercritical state.
- In conventional practice, one example of a refrigeration apparatus which performs a multi-stage compression-type refrigeration cycle using refrigerant that operates in a supercritical range is an air-conditioning apparatus which performs a two-stage compression-type refrigeration cycle using carbon dioxide as a refrigerant, such as the apparatus disclosed in Patent Literature 1 (Japanese Laid-open Patent Application No. 2007-232263).
- An example of an apparatus that uses such a two-stage compression-type refrigeration cycle as a water heater is a water heater such as the one disclosed in Patent Literature 2 (Japanese Laid-open Patent Application No. 2002-106988), for example. In this water heater, a conventional technique is used for improving compression efficiency by using an intercooler to cool refrigerant heading from a low-stage compression element to a high-stage compression element. Not only is water for a hot water supply heated in a gas cooler, but some of this heated water is branched off, part is successively led to and heated in the gas cooler while the other part is led to and heated in an intercooler, and hot water for a hot water supply is obtained. Thus, the intercooler can be used as a heater of hot water and also as a cooler of refrigerant drawn into the high-stage compression element, and energy efficiency can be improved.
- In the water heater described above, water flowing into the intercooler has already been heated when passing through the gas cooler, and is warm water having a somewhat high temperature. Therefore, there could be cases in which the temperature of the warm water that has passed through the gas cooler and been heated is higher than the temperature of the refrigerant passing through the intercooler, for example. In such cases, not only is it not possible to heat the water in the intercooler, but it is also not possible to cool the refrigerant drawn into the high-stage compression element, and it is therefore not possible to improve compression efficiency.
- An object of the present invention is to provide a refrigeration apparatus which uses refrigerant that operates including the process of a supercritical state, wherein it is possible to more reliably improve compression efficiency and make the heating of water for a hot water supply more efficient.
- A refrigeration apparatus according to a first aspect of the present invention is refrigeration apparatus which performs heat exchange on a water tube system having a water inlet tube for leading water supplied from the exterior to a water branching point, first branching water tubes and second branching water tubes extending from the water branching point, and a water outlet tube leading out to the exterior from a convergent point where the first branching water tubes and the second branching water tubes converge, wherein the active refrigerant is in a supercritical state in at least part of the refrigeration cycle; the refrigeration apparatus comprising a main expansion mechanism, an evaporator, a first compression element, a second compression element, a first refrigerant tube, a first heat exchanger, second refrigerant tubes, and a second heat exchanger. The main expansion mechanism depressurizes the refrigerant. The evaporator is connected with the main expansion mechanism and the evaporator evaporates the refrigerant. The first compression element draws in refrigerant that has passed through the evaporator and compresses and discharges the refrigerant. The second compression element draws in the refrigerant discharged from the first compression element and further compresses and discharges the refrigerant. The first refrigerant tube draws the refrigerant discharged from the first compression element into the second compression element. The first heat exchanger performs heat exchange between the refrigerant passing through the first refrigerant tube and the water flowing through the first branching water tubes. The second refrigerant tubes connect the discharge side of the second compression element and the main expansion mechanism. The second heat exchanger subjects the refrigerant passing through the second refrigerant tubes to heat exchange with the water flowing through the second branching water tubes, and not to heat exchange with the water flowing through the water inlet tube. Herein, the first compression element and the second compression element may be either housed within the same casing or the like and controlled together, or disposed separately and controlled independently of each other.
- Even if the intention is to warm the water passing through the water tube system in the first heat exchanger whose refrigerant temperature is lower than the second heat exchanger, for example, the temperature will sometimes be higher than the temperature of the refrigerant flowing through the first heat exchanger due to the water already being warmed before flowing into the first heat exchanger. In this case, there is a risk that it will not be possible to cool the refrigerant by heat exchange in the first heat exchanger, and that the water will be deprived of its heat by the refrigerant.
- As a countermeasure to this, in this refrigeration apparatus, the second heat exchanger does not subject the refrigerant passing through the second refrigerant tube to heat exchange with the water flowing through the water inlet tube. Therefore, the water can be made to flow in during a state of low temperature in which not only is the water flowing into the second heat exchanger not yet heated by heat exchange with the refrigerant, but neither is the water flowing into the first heat exchanger.
- Thereby, the refrigerant heading from the first compression element toward the second compression element is cooled to reliably improve compression efficiency, heat exchanging which can raise the water temperature can be reliably performed by both the first heat exchanger and the second heat exchanger, and the coefficient of performance of the refrigeration apparatus can be improved.
- A refrigeration apparatus according to a second aspect of the present invention is the refrigeration apparatus according to the first aspect of the present invention, further comprising a flow rate ratio adjustment mechanism capable of adjusting the ratio between a quantity of water flowing through the first branching water tubes and a quantity of water flowing through the second branching water tubes.
- According to this refrigeration apparatus, since it is possible to adjust the flow rate ratio between the quantity of water flowing through the first heat exchanger and the quantity of water flowing through the second heat exchanger, it is possible for the water to be heated efficiently.
- A refrigeration apparatus according to a third aspect of the present invention is the refrigeration apparatus according to the second aspect of the present invention, further comprising a heating capacity detection unit and a water distribution quantity control unit. The heating capacity detection unit is capable of detecting the capacity of the refrigerant passing through the first heat exchanger to heat the water and the capacity of the refrigerant passing through the second heat exchanger to heat the water. The water distribution quantity control unit adjusts the ratio between the quantity of water flowing through the first branching water tubes and the quantity of water flowing through the second branching water tubes by controlling the flow rate adjustment mechanism in accordance with the ratio between the heating capacities of the first heat exchanger and the second heat exchanger detected by the heating capacity detection unit. The control by this water distribution quantity control unit may involve, for example, adjusting the ratio between the quantity of water flowing through the first branching water tubes and the quantity of water flowing through the second branching water tubes, either so as to achieve equality with the ratio between a first specific enthalpy obtained by subtracting the specific enthalpy of the refrigerant discharged from the first compression element from the specific enthalpy of the refrigerant drawn into the second compression element, and a second specific enthalpy obtained by subtracting the specific enthalpy of the refrigerant drawn into the second compression element from the specific enthalpy of the refrigerant discharged from the second compression element, or so as to approach this ratio. The control by this water distribution quantity control unit may otherwise involve, for example, adjusting the ratio between the quantity of water flowing through the first branching water tubes and the quantity of water flowing through the second branching water tubes, so that the water temperature in the outlet of the first heat exchanger in the first branching water tubes and the water temperature in the outlet of the second heat exchanger in the second branching water tubes are substantially equal.
- In this refrigeration apparatus, heat exchange for cooling the refrigerant and heating the water can be performed by both the first heat exchanger and the second heat exchanger, and flow rate control for improving the coefficient of performance of the refrigeration apparatus can be performed automatically.
- A refrigeration apparatus according to a fourth aspect of the present invention is the refrigeration apparatus according to any of the first through third aspects of the present invention, wherein the second refrigerant tubes have a third refrigerant tube for connecting the second heat exchanger and the main expansion mechanism. The refrigeration apparatus further comprises a fourth refrigerant tube for connecting the evaporator and an intake side of the first compression element, a third heat exchanger for performing heat exchange between the refrigerant flowing through the third refrigerant tube and the refrigerant flowing through the fourth refrigerant tube, a third heat exchange bypass tube for connecting one end and another end of a portion of the third refrigerant tube that passes through the third heat exchanger, and a heat exchanger switching mechanism capable of switching between a state in which refrigerant flows through the portion of the third refrigerant tube that passes through the third heat exchanger, and a state in which refrigerant flows through the third heat exchange bypass tube.
- In this refrigeration apparatus, through heat exchange in the third heat exchanger, the coefficient of performance can be improved by raising the degree of supercooling of the refrigerant headed to the main expansion mechanism. Furthermore, through heat exchange in the third heat exchanger, the refrigerant drawn into the first compression element can be subjected to an appropriate amount of superheating, liquid compression in the first compression element can be suppressed, and the discharge temperature can be increased to keep the resulting water temperature high.
- A refrigeration apparatus according to a fifth aspect of the present invention is the refrigeration apparatus according to the fourth aspect of the present invention, further comprising temperature sensory units and a heat exchange quantity control unit. The temperature sensory units sense at least the air temperature surrounding the evaporator or the discharged refrigerant temperature of at least the first compression element or the second compression element. The heat exchange quantity control unit controls the heat exchanger switching mechanism and increases the quantity of refrigerant flowing through the portion of the third refrigerant tube that passes through the third heat exchanger when the following condition is fulfilled: the air temperature is higher than a predetermined high-temperature air temperature when the value sensed by the temperature sensory units is an air temperature, or the refrigerant temperature is lower than a predetermined low-temperature refrigerant temperature when the value sensed by the temperature sensory units is a refrigerant temperature.
- In this refrigeration apparatus, the quantity of refrigerant flowing through the portion of the third refrigerant tube that passes through the third heat exchanger can be increased even in cases in which it appears that the air temperature surrounding the evaporator could increase or that the temperature of the refrigerant discharged from the compression element could decrease.
- It is thereby possible to increase the degree of supercooling of the refrigerant headed to the main expansion mechanism, and to improve the coefficient of performance.
- Since the refrigerant drawn into the first compression element can be subjected to the appropriate degree of superheating, it is possible to impede liquid compression from occurring in the first compression element.
- Furthermore, since the degree of superheating of the refrigerant drawn into the first compression element can be increased, it is possible to conform to cases in which the temperature required in the radiator is high.
- A refrigeration apparatus according to a sixth aspect of the present invention is the refrigeration apparatus according to any of the first through third aspects of the present invention, wherein the second refrigerant tubes have a third refrigerant tube connecting the second heat exchanger and the main expansion mechanism. The refrigeration apparatus further comprises a branching expansion mechanism, a fifth refrigerant tube, sixth refrigerant tubes, and a fourth heat exchanger. The branching expansion mechanism depressurizes refrigerant. The fifth refrigerant tube branches off from the third refrigerant tube and extends to the branching expansion mechanism. The sixth refrigerant tubes extend from the branching expansion mechanism to the first refrigerant tube. The fourth heat exchanger performs heat exchange between refrigerant flowing through the third refrigerant tube and refrigerant flowing through the sixth refrigerant tubes.
- With this refrigeration apparatus, it is possible to improve the coefficient of performance by raising the degree of supercooling of the refrigerant heading to the branching expansion mechanism.
- When the temperature of the refrigerant being mixed in from the sixth refrigerant tubes is lower than the temperature of the refrigerant flowing through the first refrigerant tube, it is also possible to suppress excessive increases in the discharged refrigerant temperature of the second compression element.
- Furthermore, the quantity of refrigerant passing through the second heat exchanger can be increased.
- A refrigeration apparatus according to a seventh aspect of the present invention is the refrigeration apparatus according to the sixth aspect of the present invention, further comprising temperature sensory units and a branched quantity control unit. The temperature sensory units sense at least the air temperature surrounding the evaporator or the discharged refrigerant temperature of at least the first compression element or the second compression element. The branched quantity control unit controls the branching expansion mechanism and increases the quantity of refrigerant passing through when the following condition is fulfilled: the air temperature is lower than a predetermined low-temperature air temperature when the value sensed by the temperature sensory units is an air temperature, or the refrigerant temperature is higher than a predetermined high-temperature refrigerant temperature when the value sensed by the temperature sensory units is a refrigerant temperature. The control by the branched quantity control unit for increasing the quantity of refrigerant passing through the branching expansion mechanism herein includes control for creating a flow from conditions of a flow rate of zero (no flow), for example.
- With this refrigeration apparatus, even in cases in which the temperature of the refrigerant discharged from the first compression element or the second compression element will presumably increase or cases in which the air temperature surrounding the evaporator decreases, excessive increases in the discharged refrigerant temperature of the second compression element can be suppressed by increasing the quantity of refrigerant passing through the branching expansion mechanism, and it is possible to improve the reliability of the first compression element or the second compression element.
- A refrigeration apparatus according to an eighth aspect of the present invention is the refrigeration apparatus according to the sixth or seventh aspect of the present invention, further comprising a water temperature sensory unit, a first refrigerant temperature sensory unit, and a refrigerant distribution quantity control unit. The water temperature sensory unit senses the temperature of water flowing through any position in the water tube system. The first refrigerant temperature sensory unit senses the temperature of refrigerant passing through the first refrigerant tube. The refrigerant distribution quantity control unit controls the branching expansion mechanism and increases the quantity of refrigerant passing through when the difference between the temperature sensed by the water temperature sensory unit and the temperature sensed by the first refrigerant temperature sensory unit is less than a predetermined value.
- With this refrigeration apparatus, even when the water's effect of cooling the refrigerant flowing through the first refrigerant tube is insufficient, it is possible to improve the coefficient of performance of the refrigeration cycle by causing the sixth refrigerant tubes to converge and thereby lowering the temperature of the refrigerant passing through the first refrigerant tube.
- A refrigeration apparatus according to a ninth aspect of the present invention is the refrigeration apparatus according to any of the first through third aspects of the present invention, wherein the second refrigerant tubes have a third refrigerant tube connecting the second heat exchanger and the main expansion mechanism. The refrigeration apparatus further comprises a branching expansion mechanism, a fourth refrigerant tube, a third heat exchanger, a fifth refrigerant tube, sixth refrigerant tubes, and a fourth heat exchanger. The branching expansion mechanism depressurizes refrigerant. The fourth refrigerant tubes connect the evaporator and an intake side of the first compression element. The third heat exchanger performs heat exchange between refrigerant flowing through the third refrigerant tube and refrigerant flowing through the fourth refrigerant tubes. The fifth refrigerant tube branches off from the third refrigerant tube and extends to the branching expansion mechanism. The sixth refrigerant tubes connect the branching expansion mechanism and the first refrigerant tube. The fourth heat exchanger performs heat exchange between refrigerant flowing through the third refrigerant tube and refrigerant flowing through the sixth refrigerant tubes.
- With this refrigeration apparatus, it is possible to raise the degree of supercooling of the refrigerant heading to the branching expansion mechanism and improve the coefficient of performance, and to apply the appropriate amount of heating to the refrigerant drawn into the first compression element and prevent liquid compression in the first compression element and/or cool the refrigerant flowing through the third refrigerant tube.
- A refrigeration apparatus according to a tenth aspect of the present invention is the refrigeration apparatus according to the ninth aspect of the present invention, further comprising temperature sensory units and a branched heat quantity control unit. The temperature sensory units sense at least the air temperature surrounding the evaporator or the discharged refrigerant temperature of at least the first compression element or the second compression element. The branched heat quantity control unit controls the branching expansion mechanism and increases the quantity of refrigerant passing through when the following condition is fulfilled: the air temperature is lower than a predetermined low-temperature air temperature when the value sensed by the temperature sensory units is an air temperature, or the refrigerant temperature is higher than a predetermined high-temperature refrigerant temperature when the value sensed by the temperature sensory units is a refrigerant temperature. The control by the branched quantity control unit for increasing the quantity of refrigerant passing through the branching expansion mechanism herein includes control for creating a flow from conditions of a flow rate of zero (no flow), for example.
- With this refrigeration apparatus, even in cases in which the temperature of the refrigerant discharged from the compression element will presumably increase or cases in which the air temperature surrounding the evaporator decreases, excessive increases in the discharged refrigerant temperature of the second compression element can be suppressed by increasing the quantity of refrigerant passing through the branching expansion mechanism, and it is possible to improve the reliability of the second compression element.
- A refrigeration apparatus according to an eleventh aspect of the present invention is the refrigeration apparatus according to the ninth or tenth aspect of the present invention, further comprising a first heat exchange bypass tube and a bypass switching mechanism. The first heat exchange bypass tube connects one end and another end of the portion of the first refrigerant tube that passes through the first heat exchanger. The bypass switching mechanism is capable of switching between a state in which refrigerant flows through the portion of the first refrigerant tube that passes through the first heat exchanger, and a state in which refrigerant flows through the first heat exchange bypass tube.
- With this refrigeration apparatus, in the first heat exchanger, the switching of the bypass switching mechanism makes it possible to switch between a state of allowing and a state of not allowing the passage of refrigerant in the heat exchange bypass tube, and also to adjust the usage condition of the first heat exchanger.
- A refrigeration apparatus according to a twelfth aspect of the present invention is the refrigeration apparatus according to the eleventh aspect of the present invention, further comprising temperature sensory units and a bypass control unit. The temperature sensory units sense at least the air temperature surrounding the evaporator or the discharged refrigerant temperature of at least the first compression element or the second compression element. The bypass control unit controls the bypass switching mechanism and increases the quantity of refrigerant flowing through the portion of the first refrigerant tube that passes through the first heat exchanger when the following condition is fulfilled: the air temperature is higher than a predetermined high-temperature air temperature when the value sensed by the temperature sensory units is an air temperature, or the refrigerant temperature is lower than a predetermined low-temperature refrigerant temperature when the value sensed by the temperature sensory units is a refrigerant temperature. The control by the bypass control unit for increasing the quantity of refrigerant passing through the portion of the first refrigerant tube herein includes control for creating a flow from conditions of a flow rate of zero (no flow), for example.
- With this refrigeration apparatus, even in cases in which the temperature of the refrigerant discharged from the compression element will presumably be low or cases in which the air temperature surrounding the evaporator has increased, the degree of superheating of the refrigerant drawn into the second compression element can be raised by reducing the quantity of refrigerant flowing through the portion of the first refrigerant tube that passes through the first heat exchanger, and it is possible to comply with a high temperature requirement in the radiator.
- A refrigeration apparatus according to a thirteenth aspect of the present invention is the refrigeration apparatus according to any of the ninth through twelfth aspects of the present invention, further comprising a water temperature sensory unit, a first refrigerant temperature sensory unit, and a water-correspondent refrigerant quantity control unit. The water temperature sensory unit senses the temperature of water flowing through any position in the water tube system. The first refrigerant temperature sensory unit senses the temperature of refrigerant passing through the first refrigerant tube. The water-correspondent refrigerant quantity control unit controls the branching expansion mechanism and increases the quantity of refrigerant passing through when the difference between the temperature sensed by the water temperature sensory unit and the temperature sensed by the first refrigerant temperature sensory unit is less than a predetermined value.
- With this refrigeration apparatus, even when the water's effect of cooling the refrigerant flowing through the first refrigerant tube is insufficient, it is possible to improve the coefficient of performance of the refrigeration cycle by causing the refrigerant passing through the sixth refrigerant tubes to mix, thereby lowering the temperature of the refrigerant flowing through the first refrigerant tube.
- A refrigeration apparatus according to a fourteenth aspect of the present invention is the refrigeration apparatus according to any of the first through thirteenth aspects of the present invention, further comprising a first drive unit for driving the first compression element, and a second drive unit for driving the second compression element independently of the first compression element.
- With this refrigeration apparatus, since the capacity of the first compression element and the capacity of the second compression element can be adjusted so as to be different, during control for mixing the water flowing through the first branching water tube and the water flowing through the second branching water tube and attempting to bring the temperature of the water flowing through the output water tube to a target temperature, the coefficient of performance can be made satisfactory and the effect of minimizing the compression work can be further improved by separately adjusting the capacity of the first compression element and the capacity of the second compression element.
- A refrigeration apparatus according to a fifteenth aspect of the present invention is the refrigeration apparatus according to any of the first through thirteenth aspects of the present invention, wherein the first compression element and the second compression element have a shared rotating shaft for performing compression work by rotatably driving each of the compression elements.
- With this refrigeration apparatus, vibrations and/or fluctuations in torque load can be suppressed by driving the compression elements while causing their centrifugal forces to cancel each other out.
- A refrigeration apparatus according to a sixteenth aspect of the present invention is the refrigeration apparatus according to any of the first through fifteenth aspects of the present invention, wherein the active refrigerant is carbon dioxide.
- In this refrigeration apparatus, with carbon dioxide in a supercritical state near a critical point, the density of the refrigerant can be changed dramatically merely by slightly changing the refrigerant pressure. Therefore, the efficiency of the refrigeration apparatus can be improved by a small amount of compression work.
- As stated in the above descriptions, the following effects are achieved according to the present invention.
- In the first aspect, the refrigerant heading from the first compression element toward the second compression element is cooled to reliably improve compression efficiency, heat exchanging which can raise the water temperature can be reliably performed by both the first heat exchanger and the second heat exchanger, and the coefficient of performance of the refrigeration apparatus can be improved.
- In the second aspect, it is possible for the water to be heated efficiently.
- In the third aspect, flow rate control for improving the coefficient of performance of the refrigeration apparatus can be performed automatically.
- In the fourth aspect, it is possible to improve the coefficient of performance, to suppress liquid compression in the first compression element, and to increase the discharge temperature to keep the resulting water temperature high.
- In the fifth aspect, it is possible to increase the degree of supercooling of the refrigerant headed to the main expansion mechanism, and to improve the coefficient of performance.
- In the sixth aspect, it is possible to improve the coefficient of performance by raising the degree of supercooling of the refrigerant heading to the branching expansion mechanism.
- In the seventh aspect, it is possible to improve the reliability of the first compression element or the second compression element.
- In the eighth aspect, even when the water's effect of cooling the refrigerant flowing through the first refrigerant tube is insufficient, it is possible to improve the coefficient of performance of the refrigeration cycle.
- In the ninth aspect, it is possible to improve the coefficient of performance, and to prevent liquid compression in the first compression element and/or cool the refrigerant flowing through the third refrigerant tube.
- In the tenth aspect, even in cases in which the temperature of the refrigerant discharged from the compression element will presumably increase or cases in which the air temperature surrounding the evaporator decreases, it is possible to improve the reliability of the second compression element.
- In the eleventh aspect, it is possible to switch between a state of allowing and a state of not allowing the passage of refrigerant in the heat exchange bypass tube, and also to adjust the usage condition.
- In the twelfth aspect, even in cases in which the temperature of the refrigerant discharged from the compression element will presumably be low or cases in which the air temperature surrounding the evaporator has increased, it is possible to comply with a high temperature requirement in the radiator.
- In the thirteenth aspect, even when the water's effect of cooling the refrigerant flowing through the first refrigerant tube is insufficient, it is possible to improve the coefficient of performance of the refrigeration cycle.
- In the fourteenth aspect, the coefficient of performance can be made satisfactory and the effect of minimizing the compression work can be further improved.
- In the fifteenth aspect, the occurrence of vibrations and/or fluctuations in torque load can be suppressed by driving the compression elements while causing their centrifugal forces to cancel each other out.
- In the sixteenth aspect, the efficiency of the refrigeration apparatus can be improved by a small amount of compression work.
-
FIG. 1 is a schematic structural diagram of an air-conditioning apparatus as an embodiment of the refrigeration apparatus according to the first embodiment of the present invention. -
FIG. 2 is a pressure-enthalpy graph representing the refrigeration cycle of the air-conditioning apparatus according to the first embodiment. -
FIG. 3 is a temperature-entropy graph representing the refrigeration cycle of the air-conditioning apparatus according to the first embodiment. -
FIG. 4 is a schematic structural diagram of an air-conditioning apparatus according toModification 1 of the first embodiment. -
FIG. 5 is a schematic structural diagram of an air-conditioning apparatus according toModification 2 of the first embodiment. -
FIG. 6 is a schematic structural diagram of an air-conditioning apparatus according to Modification 3 of the first embodiment. -
FIG. 7 is a schematic structural diagram of an air-conditioning apparatus according toModification 7 of the first embodiment. -
FIG. 8 is a schematic structural diagram of an air-conditioning apparatus as an embodiment of the refrigeration apparatus according to the second embodiment of the present invention. -
FIG. 9 is a pressure-enthalpy graph representing the refrigeration cycle of the air-conditioning apparatus according to the second embodiment. -
FIG. 10 is a temperature-entropy graph representing the refrigeration cycle of the air-conditioning apparatus according to the second embodiment. -
FIG. 11 is a schematic structural diagram of an air-conditioning apparatus according toModification 1 of the second embodiment. -
FIG. 12 is a schematic structural diagram of an air-conditioning apparatus according toModification 5 of the second embodiment. -
FIG. 13 is a schematic structural diagram of an air-conditioning apparatus as an embodiment of a refrigeration apparatus according to the third embodiment of the present invention. -
FIG. 14 is a pressure-enthalpy graph representing the refrigeration cycle of an air-conditioning apparatus according to the third embodiment. -
FIG. 15 is a temperature-entropy graph representing the refrigeration cycle of an air-conditioning apparatus according to the third embodiment. -
FIG. 16 is a schematic structural diagram of an air-conditioning apparatus according toModification 1 of the third embodiment. -
FIG. 17 is a schematic structural diagram of an air-conditioning apparatus according toModification 4 of the third embodiment. -
FIG. 18 is a schematic structural diagram of an air-conditioning apparatus as an embodiment of a refrigeration apparatus according to the fourth embodiment of the present invention. -
FIG. 19 is a pressure-enthalpy graph representing the refrigeration cycle of an air-conditioning apparatus according to the fourth embodiment. -
FIG. 20 is a temperature-entropy graph representing the refrigeration cycle of an air-conditioning apparatus according to the fourth embodiment. -
FIG. 21 is a schematic structural diagram of an air-conditioning apparatus according toModification 1 of the fourth embodiment. -
FIG. 22 is a schematic structural diagram of an air-conditioning apparatus according toModification 2 of the fourth embodiment. -
FIG. 23 is a schematic structural diagram of an air-conditioning apparatus according to Modification 3 of the fourth embodiment. -
FIG. 24 is a schematic structural diagram of an air-conditioning apparatus according toModification 4 of the fourth embodiment. -
FIG. 25 is a schematic structural diagram of an air-conditioning apparatus according toModification 8 of the fourth embodiment. -
FIG. 1 is a schematic structural diagram of awater heater 1 as an embodiment of the refrigeration apparatus according to the present invention. Thewater heater 1 is an apparatus for producing heated water by using refrigerant that operates in a supercritical range (carbon dioxide in this case) to perform a two-stage compression-type refrigeration cycle. - The
water heater 1 has awater circuit 910 and arefrigerant circuit 10. - (Water Circuit)
- The
water circuit 910 has awater inlet tube 901 for leading water supplied from the exterior to a water branching point W, heatsource water tubes intermediate water tubes water outlet tube 906 leading out to the exterior from a convergent point Z where the heatsource water tubes intermediate water tubes FIG. 1 . - A
pump 921 capable of adjusting the quantity of water passing through is provided to thewater inlet tube 901. Thispump 921 is provided with amotor 921 m, the rotational speed is adjusted by acontrol unit 99, and the flow rate of the pump is adjusted. Thewater circuit 910 is also provided with awater temperature sensor 910T for detecting the temperature of the water passing through thewater inlet tube 901. Through thewater temperature sensor 910T, thecontrol unit 99 can perceive the temperature of the supplied water, thecontrol unit 99 perceives the difference from the output water temperature requested by the user, and a refrigeration cycle of therefrigerant circuit 10 is adjusted. - The heat
source water tube 902 extends from the branching point W to a heat source-side heat exchanger 4 of therefrigerant circuit 10, described hereinafter. The heatsource water tube 903 extends so as to lead water flowing out of the heat source-side heat exchanger 4 to the convergent point Z. Thus, the water flowing through the heatsource water tubes side heat exchanger 4 by heat exchange with the refrigerant flowing through therefrigerant circuit 10, and heated water is produced. A tube configuration is created so that the refrigerant and water flow opposite each other in anintercooler 7, and the heat exchange efficiency is improved. - The
intermediate water tube 904 extends from the branching point W to theintercooler 7 of therefrigerant circuit 10, described hereinafter. Theintermediate water tube 905 extends so as to lead the water flowing out of theintercooler 7 to the convergent point Z. Thus, the water flowing through theintermediate water tubes intercooler 7 by heat exchange with the refrigerant flowing through therefrigerant circuit 10, and heated water is produced. A tube configuration is created so that the refrigerant and water flow opposite each other in the heat source-side heat exchanger 4, and the heat exchange efficiency is improved. Since the refrigerant temperature in theintermediate water tubes side heat exchanger 4, theintermediate water tubes source water tubes side heat exchanger 4. - Hot water which has been warmed in the heat
source water tubes intermediate water tubes water outlet tube 906. - (Refrigerant Circuit)
- The
refrigerant circuit 10 has primarily a low-stage compression element 2 c, a high-stage compression element 2 d, the heat source-side heat exchanger 4, anexpansion mechanism 5, a usage-side heat exchanger 6, an intermediaterefrigerant tube 22, anintercooler 7,connection tubes side temperature sensor 6T. - In the present embodiment, the low-
stage compression element 2 c and the high-stage compression element 2 d compress the refrigerant sequentially in two stages. - The low-
stage compression element 2 c has a hermetically sealed structure in which acompressor drive motor 21 b and adrive shaft 21 c are housed within acasing 21 a. Thecompressor drive motor 21 b is linked to thedrive shaft 21 c. Thisdrive shaft 21 c is linked to thecompression element 2 c. Thecompression element 2 c is a rotary-type, scroll-type, or another type of positive displacement compression element in the present embodiment. The low-stage compression element 2 c draws refrigerant in from anintake tube 2 a, compresses the drawn-in refrigerant, and discharges the refrigerant toward the intermediaterefrigerant tube 22. The intermediaterefrigerant tube 22 connects the discharge side of the low-stage compression element 2 c and the intake side of the high-stage compression element 2 d via theintercooler 7. Adischarge tube 2 b is a refrigerant tube for feeding the refrigerant discharged from the low-stage compression element 2 c to the high-stage compression element 2 d via theintercooler 7, and thedischarge tube 2 b is provided with anon-return mechanism 42 c and a mechanism for separating the refrigerant from refrigeration oil which accompanies the refrigerant discharged from the low-stage compression element 2 c and returning the refrigeration oil to the intake side of the low-stage compression element 2 c. The mechanism for returning the refrigeration oil has primarily anoil separator 41 a for separating the refrigerant from the refrigeration oil accompanying the refrigerant discharged from the low-stage compression element 2 c, and anoil return tube 41 b which is connected to theoil separator 41 a and which returns the refrigeration oil separated from the refrigerant to theintake tube 2 a of the low-stage compression element 2 c. Theoil return tube 41 b is provided with adepressurization mechanism 41 c for depressurizing the refrigeration oil flowing through theoil return tube 41 b. A capillary tube is used as thedepressurization mechanism 41 c in the present embodiment. Thenon-return mechanism 42 c is a mechanism for allowing the flow of refrigerant from the discharge side of the low-stage compression element 2 c to theintercooler 7 and blocking the flow of refrigerant from theintercooler 7 to the discharge side of the low-stage compression element 2 c, and a non-return valve is used in the present embodiment. - The high-
stage compression element 2 d is similar to the low-stage compression element 2 c, and has a hermetically sealed structure in which acompressor drive motor 21 e and adrive shaft 21 f are housed within acasing 21 d. Thecompressor drive motor 21 e is linked to thedrive shaft 21 f. Thisdrive shaft 21 f is linked to thecompression element 2 d. Thecompression element 2 d is a rotary-type, scroll-type, or another type of positive displacement compression element in the present embodiment. The high-stage compression element 2 d draws refrigerant in from the intermediaterefrigerant tube 22, compresses the drawn-in refrigerant, and discharges the refrigerant toward adischarge tube 2 e. Thedischarge tube 2 e connects the discharge side of the high-stage compression element 2 d and the heat source-side heat exchanger 4. Thedischarge tube 2 e is provided with anon-return mechanism 42 d and a mechanism for separating the refrigerant from refrigeration oil which accompanies the refrigerant discharged from the high-stage compression element 2 d and returning the refrigeration oil to the intake side of the high-stage compression element 2 d. The mechanism for returning the refrigeration oil has primarily anoil separator 41 d for separating the refrigerant from the refrigeration oil accompanying the refrigerant discharged from the high-stage compression element 2 d, and anoil return tube 41 e which is connected to theoil separator 41 d and which returns the refrigeration oil separated from the refrigerant to the intermediaterefrigerant tube 22, which is on the intake side of the high-stage compression element 2 d. Theoil return tube 41 e is provided with adepressurization mechanism 41 f for depressurizing the refrigeration oil flowing through theoil return tube 41 e. A capillary tube is used as thedepressurization mechanism 41 f in the present embodiment. Thenon-return mechanism 42 d is a mechanism for allowing the flow of refrigerant from the discharge side of the high-stage compression element 2 d to the heat source-side heat exchanger 4 and blocking the flow of refrigerant from the heat source-side heat exchanger 4 to the discharge side of the high-stage compression element 2 d, and a non-return valve is used in the present embodiment. - That is, the two
compression elements individual drive shafts compression elements compressor drive motors - The
intercooler 7 warms the water flowing through theintermediate water tubes refrigerant tube 22, and cools the refrigerant flowing through the intermediaterefrigerant tube 22 by the water flowing through theintermediate water tubes stage compression element 2 d can thereby be reduced, and the temperature of the refrigerant discharged from the high-stage compression element 2 d is prevented from increasing excessively. The refrigeration capacity can also be improved because the density of the refrigerant drawn into the high-stage compression element 2 d is increased by lowering the temperature of the refrigerant flowing through the intermediaterefrigerant tube 22 in this manner. - The heat source-
side heat exchanger 4 is a heat exchanger which has air as a heat source and functions as a radiator of refrigerant. The heat source-side heat exchanger 4 is connected at one end to the discharge side of the high-stage compression element 2 d via theconnection tube 71 and thenon-return mechanism 42, and is connected at the other end to theexpansion mechanism 5 via theconnection tube 72. In this heat source-side heat exchanger 4, the water flowing through the heatsource water tubes connection tube 71 to theconnection tube 72, and the refrigerant heading from theconnection tube 71 to theconnection tube 72 is cooled by the water flowing through the heatsource water tubes - The
expansion mechanism 5 is connected at one end to theconnection tube 72, and is connected at the other end to the usage-side heat exchanger 6 via theconnection tube 76. Theexpansion mechanism 5 is a mechanism for depressurizing the refrigerant, and an electric expansion valve is used in the present embodiment. In the present embodiment, theexpansion mechanism 5 depressurizes the high-pressure refrigerant cooled in the heat source-side heat exchanger 4 nearly to the saturation pressure of the refrigerant before feeding the refrigerant to the usage-side heat exchanger 6. - The usage-
side heat exchanger 6 is a heat exchanger which functions as an evaporator of refrigerant. The usage-side heat exchanger 6 is connected at one end to theexpansion mechanism 5 via theconnection tube 76, and is connected at the other end to the intake side of the low-stage compression element 2 c via theintake tube 2 a. Though not shown in the diagram, the usage-side heat exchanger 6 is supplied with water and/or air as a heating source for performing heat exchange with the refrigerant flowing through the usage-side heat exchanger 6. - The usage-
side temperature sensor 6T detects the temperature of the water and/or air supplied as a heating source in order to perform heat exchange with the refrigerant flowing through the usage-side heat exchanger 6 described above. - As described above, the
water heater 1 is provided with acontrol unit 99 which perceives the temperature sensed by the usage-side temperature sensor 6T, and which controls the actions of the low-stage compression element 2 c, the high-stage compression element 2 d, theexpansion mechanism 5, thepump 921, and other components constituting thewater heater 1. - Next, the action of the
water heater 1 of the present embodiment will be described usingFIGS. 1 , 2 and 3. - Herein,
FIG. 2 is a pressure-enthalpy graph representing the refrigeration cycle, andFIG. 3 is a temperature-entropy graph representing the refrigeration cycle. - The states of the refrigerant at the points indicated by A, B, C, D, K, and M in the
refrigerant circuit 10 ofFIG. 1 correspond to the same points in the pressure-enthalpy graph shown inFIG. 2 and the temperature-entropy graph shown inFIG. 3 . - In this refrigeration cycle, the refrigerant flowing through the intermediate
refrigerant tube 22 is cooled by the refrigerant flowing through theintermediate water tubes water circuit 910 when passing through the intercooler 7 (refer to point B point C inFIGS. 2 and 3 ). - (Target Capacity Output Control)
- In this type of refrigeration cycle, the
control unit 99 performs target capacity output control as follows. - First, the
control unit 99 receives an input value of output water temperature and an input value of a required output water quantity from the user via a controller or the like (not shown). Thecontrol unit 99 controls the flow rate of water by controlling the rotational speed of themotor 921 m of thepump 921 on the basis of the input value of the required output water quantity. - The
control unit 99 then perceives the water temperature detected by thewater temperature sensor 910T and the flow rate controlled by themotor 921 m of thepump 921, and calculates emitted heat quantity required for the refrigerant supplied to the heat source-side heat exchanger 4. Based on this required emitted heat quantity, thecontrol unit 99 then calculates the target discharge pressure for the pressure of the refrigerant discharged from the high-stage compression element 2 d. - A case of a target discharge pressure being the target value in the target capacity output control is herein described as an example, but instead of the target discharge pressure, target values of the discharged refrigerant pressure and the discharged refrigerant temperature may be established so that the value obtained by multiplying the discharged refrigerant temperature by the discharged refrigerant pressure is within a predetermined range. This is because in cases in which the load has changed, the density of the discharged refrigerant decreases when the degree of superheating of the drawn-in refrigerant is high; therefore, even if it is possible to maintain the temperature of the refrigerant discharged from the high-
stage compression element 2 d, it becomes impossible to guarantee the emitted heat quantity required in the heat source-side heat exchanger 4. - Next, based on the temperature sensed by the usage-
side temperature sensor 6T, thecontrol unit 99 establishes a target evaporation temperature and a target evaporation pressure (a pressure equal to or less than the critical pressure). This setting of the target evaporation pressure is performed every time the temperature sensed by the usage-side temperature sensor 6T changes. - Based on this target evaporation temperature value, the
control unit 99 performs superheat degree control so that the degree of superheating of the refrigerant drawn in by the low-stage compression element 2 c is a target value x (degree of superheating target value) of 5° C. or less. - The
control unit 99 then controls the low-stage compression element 2 c so as to raise the refrigerant pressure and refrigerant temperature while causing isentropic change for maintaining the entropy value at the degree of superheating established in this manner, and refrigerant is discharged to the intermediaterefrigerant tube 22. In theintercooler 7 provided to the intermediaterefrigerant tube 22, heat exchange is performed while the water and refrigerant flow against each other, the refrigerant is cooled by the water flowing through theintermediate water tubes intermediate water tubes refrigerant tube 22 is cooled in theintercooler 7 and drawn into the high-stage compression element 2 d. In the high-stage compression element 2 d, refrigerant is discharged at a pressure exceeding the critical pressure due to the operating capacity being controlled by controlling the rotational speed. Having been increased in temperature by being further compressed by the high-stage compression element 2 d in this manner, the refrigerant is fed to the heat source-side heat exchanger 4. In the heat source-side heat exchanger 4, heat exchange is performed while the high-temperature, high-pressure refrigerant in a supercritical state and the water flow against each other, and water having the target output water temperature is obtained. - In this heat radiation process in the heat source-
side heat exchanger 4, since the refrigerant is in a supercritical state, the refrigerant temperature continuously decreases while the pressure is being changed such that the refrigerant is maintained at the target discharge pressure as an isobaric change. The refrigerant flowing through the heat source-side heat exchanger 4 has a temperature equal to or greater than the temperature of the water supplied as a heating target through the heatsource water tubes motor 921 m of thepump 921. - The refrigerant cooled in the heat source-
side heat exchanger 4 in this manner is depressurized to the target evaporation pressure (a pressure equal to or less than the critical pressure) by theexpansion mechanism 5, and the refrigerant flows into the usage-side heat exchanger 6. - The refrigerant flowing through the usage-
side heat exchanger 6 absorbs heat from the water and/or air supplied as a heating source, whereby the dryness of the refrigerant is progressively improved while isobaric-isothermal change is conducted such that the target evaporation temperature and the target evaporation pressure are maintained. Thecontrol unit 99 then controls the quantity supplied by a heating source supply device (not shown) (a pump in the case of water, and a fan or the like in the case of air) so that the degree of superheating reaches the degree of superheating target value. - When performing control in this manner, the
control unit 99 calculates the value of x and the value of y so that the coefficient of performance (COP) in the refrigeration cycle will be as high as possible, and performs the target capacity output control described above. When calculating the value of x and the value of y which yield the best coefficient of performance, thecontrol unit 99 performs the calculation on the basis of the properties (a Mollier diagram or the like) of carbon dioxide as the active refrigerant. A condition may be established at which the coefficient of performance can be satisfactorily maintained to a certain extent, and if this condition is met, the value of x and the value of y may be determined such that the compression work will be a smaller value. Another option is to use a precondition that the compression work is suppressed to a predetermined value or lower, and to determine the value of x and the value of y which yield the best coefficient of performance while this precondition is being met. - The relationship between heat radiation quantity control guaranteed in the heat source-
side heat exchanger 4 and/or the intermediaterefrigerant tube 22 of therefrigerant circuit 10 and flow rate control of thepump 921, which are performed by thecontrol unit 99, includes a large adjustment of the flow rate of thepump 921 of thewater circuit 910 or another action when therefrigerant circuit 10 is controlled so that the heat radiation quantity in the heat source-side heat exchanger 4 and/or the intermediaterefrigerant tube 22 increases, for example. This relationship between heat radiation quantity control and flow rate control also includes control for minimizing the flow rate of thepump 921 of thewater circuit 910 when, conversely, a large heat radiation quantity cannot be achieved in the heat source-side heat exchanger 4 and/or the intermediaterefrigerant tube 22. Thecontrol unit 99 gives less priority to controlling the output water quantity than to the output water temperature while achieving the output water temperature requested by the user. - (Characteristics of First Embodiment)
- The water that has branched off in the branching point W and that flows through the
intermediate water tubes side heat exchanger 4, and this water has the same temperature as the temperature of the refrigerant flowing through thewater inlet tube 901. During control performed by thecontrol unit 99, in therefrigerant circuit 10 which uses carbon dioxide as the active refrigerant, degree of superheating control is performed so that the degree of superheating reaches a target value x of 5° C. or less, and the compression ratio in the low-stage compression element 2 c and the compression ratio in the high-stage compression element 2 d are adjusted so as to be equal. Therefore, according to the properties of carbon dioxide in a Mollier diagram, the temperature of the refrigerant flowing through the heat source-side heat exchanger 4 is inevitably higher than the temperature of the refrigerant flowing through theintercooler 7. Thus, in a refrigeration cycle in which the temperature of the refrigerant flowing through theintercooler 7 and the temperature of the refrigerant flowing through the heat source-side heat exchanger 4 are different and the temperature of the refrigerant flowing through theintercooler 7 is the lower of the two, in order to achieve the refrigeration cycle effect by way of theintercooler 7, i.e., effect of cooling the refrigerant drawn into the high-stage compression element 2 d, the refrigeration cycle is limited to cases in which the temperature of the water flowing through theintermediate water tubes refrigerant tube 22. Therefore, if the water flowing into theintercooler 7 has already been heated to a certain extent in the heat source-side heat exchanger 4 before flowing into theintercooler 7, not only is this effect of cooling the refrigerant drawn into the high-stage compression element 2 d lessened, but the reverse effect will sometimes occur when the temperature of the water flowing through theintermediate water tubes refrigerant tube 22. As a countermeasure to this, in thewater heater 1 of the present embodiment, the water flowing into theintercooler 7 can be made to flow into theintercooler 7 via theintermediate water tube 904 without taking heat from the exterior after the water has branched off at the branching point W. Therefore, the effect of cooling the refrigerant drawn into the high-stage compression element 2 d can be achieved merely due to the temperature of the water flowing through thewater inlet tube 901 at least being lower than the temperature of the refrigerant flowing through the intermediaterefrigerant tube 22, and it is possible to prevent this effect from lessening or to prevent the reverse effect from occurring due to the water flowing through theintermediate water tubes intercooler 7. - As one example of control by the
control unit 99 in the embodiment described above, the following type of control can be performed, for example. - In this example, the design pressure resistance of the low-
stage compression element 2 c and the high-stage compression element 2 d is 12 MPa, and the discharged refrigerant pressure must be maintained at or below this design pressure resistance. - In cases in which the
control unit 99 establishes the discharged refrigerant temperature on the basis of the input value of the output water temperature from the user, the target discharge pressure and target discharge temperature are established so as to achieve a refrigerant pressure and refrigerant temperature which are equal to or less than the design pressure described above and which can guarantee a heat radiation quantity of the refrigerant supplied to the heat source-side heat exchanger 4. The target state of the discharged refrigerant thereby converges at one point in a Mollier diagram of the refrigeration cycle which uses carbon dioxide as the active refrigerant. - On the other hand, the target evaporation pressure of the refrigeration cycle is established according to the temperature sensed by the usage-
side temperature sensor 6T. - In cases in which a control is performed so that the compression ratio in the low-
stage compression element 2 c and the compression ratio in the high-stage compression element 2 d are equal, the target intermediate pressure flowing through the intermediaterefrigerant tube 22 is established according to the above-described relationship between the target discharge pressure and the evaporation pressure. - When the degree of superheating of the refrigerant drawn into the low-
stage compression element 2 c is set at 5° C., the discharged refrigerant temperature and pressure are established by causing isentropic change in the low-stage compression element 2 c. Furthermore, if isentropic change takes place in the high-stage compression element 2 d so that the target discharge pressure and target discharge temperature can be achieved, the temperature of the refrigerant drawn into the high-stage compression element 2 d is established. - The quantity of cold energy needed to cool the refrigerant discharged from the low-
stage compression element 2 c until it is drawn into the high-stage compression element 2 d is thereby established, and thecontrol unit 99 may control the flow rate of thepump 921 on the basis of the value detected by thewater temperature sensor 910T so that this cold energy quantity can be supplied. - The degree of superheating is not limited to 5° C., and can be selected within a range of 0 to 5° C. The temperature of the refrigerant flowing into the
expansion mechanism 5 is also adjustable, and the value of x and the value of y may be established so as to yield the best coefficient of performance of the refrigeration cycle while these values are being adjusted. - As shown in
FIG. 4 , for example, arefrigerant circuit 10A may be used which has a dischargedrefrigerant temperature sensor 2T for sensing the temperature of the refrigerant discharged from the high-stage compression element 2 d. - If the temperature detected by this discharged
refrigerant temperature sensor 2T is too high, it will not be possible to maintain the reliability of the high-stage compression element 2 d, and thecontrol unit 99 may therefore perform control for reducing the flow rate of thepump 921 while reducing the discharged refrigerant temperature. - It is thereby possible to achieve the output water temperature requested by the user while guaranteeing the reliability of the high-
stage compression element 2 d. - In the embodiment described above, an example was described in which the diameters of the
intermediate water tubes source water tubes - However, the present invention is not limited to this example, and another option is to use a
refrigerant circuit 10B provided with a flow rateratio adjustment mechanism 911 capable of adjusting the ratio between the quantity of water flowing through theintermediate water tubes source water tubes FIG. 5 , for example. - For example, the flow rate
ratio adjustment mechanism 911 can be provided at an intermediate point in theintermediate water tubes intermediate water tubes source water tubes - When the flow rate ratio between the quantity of water flowing through the heat
source water tubes intermediate water tubes control unit 99 may control the flow rate ratio so as to achieve equality between the ratio of the heating amount in the heat source-side heat exchanger 4 and the heating amount in theintercooler 7 as obtained from the Mollier diagram, and the ratio of the quantity of water flowing through the heatsource water tubes intermediate water tubes intercooler 7 in this case can be perceived according to an intermediate specific enthalpy (point B→point C in the Mollier diagram) obtained by subtracting the specific enthalpy of the refrigerant discharged from the low-stage compression element 2 c from the specific enthalpy of the refrigerant drawn into the high-stage compression element 2 d. The heating amount in the heat source-side heat exchanger 4 can be perceived according to a heat source specific enthalpy (point D→point K in the Mollier diagram) obtained by subtracting the specific enthalpy of the refrigerant discharged from the high-stage compression element 2 d from the specific enthalpy of the refrigerant in the outlet of the heat source-side heat exchanger 4. Thus, thecontrol unit 99 performs a control so that the ratio of the quantity of water flowing through the heatsource water tubes intermediate water tubes control unit 99 may perform feedback control in accordance with predetermined time intervals (or a predetermined degree of ratio deviation) so as to adapt to the ratio between the heat source specific enthalpy and the intermediate specific enthalpy at the point in time of the change. - Instead of merely performing control using the values of the heat source specific enthalpy and/or the intermediate specific enthalpy in this manner, the
control unit 99 may control the ratio between the quantity of water flowing through the heatsource water tubes intermediate water tubes side heat exchanger 4 in the heatsource water tube 903 and the outlet temperature of theintercooler 7 in theintermediate water tube 905 are substantially equal, for example. Thecontrol unit 99 may cause the outlet temperatures to coincide through a predetermined feedback control in this case as well. - In cases in which the intention is to increase only the quantity of water in the heat
source water tubes control unit 99 to also make adjustments for increasing the quantity of water flowing through the heatsource water tubes intermediate water tubes pump 921 to increase the flow rate and by narrowing the opening degree of the flow rateratio adjustment mechanism 911. - The
control unit 99 can thereby perform control for bringing the coefficient of performance of the refrigeration cycle to a satisfactory value in an operation for achieving not only the user's desired output water temperature but the user's desired output water quantity as well. - Another possibility, for example, is to use a
refrigerant circuit 10C which is provided with a heat sourcerefrigerant temperature sensor 4T for detecting the temperature of the refrigerant passing through the heat source-side heat exchanger 4, a heat sourcerefrigerant pressure sensor 4P for detecting the pressure of the refrigerant passing through the heat source-side heat exchanger 4, an intermediaterefrigerant temperature sensor 22T for detecting the temperature of the refrigerant passing through the intermediaterefrigerant tube 22, an intermediaterefrigerant pressure sensor 22P for detecting the pressure of the refrigerant passing through the intermediaterefrigerant tube 22, and the flow rateratio adjustment mechanism 911 shown in Modification 3. - The radiated heat quantity that can be supplied to the water from the refrigerant in the heat source-
side heat exchanger 4 can be perceived according to the values sensed by the heat sourcerefrigerant temperature sensor 4T for detecting the temperature of the refrigerant passing through the heat source-side heat exchanger 4 and the heat sourcerefrigerant pressure sensor 4P for detecting the pressure of the refrigerant passing through the heat source-side heat exchanger 4, and the heat radiation quantity that can be supplied to the water from the refrigerant in theintercooler 7 can be perceived according to the values sensed by intermediaterefrigerant temperature sensor 22T for detecting the temperature of the refrigerant passing through the intermediaterefrigerant tube 22 and the intermediaterefrigerant pressure sensor 22P for detecting the pressure of the refrigerant passing through the intermediaterefrigerant tube 22. Therefore, thecontrol unit 99 can adjust the opening degree of the flow rateratio adjustment mechanism 911 so as to adapt to the radiated heat quantity that can be supplied to the water from the refrigerant in the heat source-side heat exchanger 4 and the heat radiation quantity that can be supplied to the water from the refrigerant in theintercooler 7, and thecontrol unit 99 can perform control so as to achieve an efficient flow rate ratio for obtaining the required output water temperature. - In
Modification 4 described above, awater circuit 910 provided with a flow rateratio adjustment mechanism 911 was described as an example. - However, the present invention is not limited to this example, and a water circuit may be used in which an on/off valve is provided to the heat
source water tubes intermediate water tubes ratio adjustment mechanism 911, for example. - In the embodiment described above, an example of a refrigerant circuit was described in which only one two-stage compression mechanism was provided, wherein compression took place in two stages in the low-
stage compression element 2 c and the high-stage compression element 2 d. - However, the present invention is not limited to this example; another possibility is to use a refrigerant circuit wherein the aforementioned two-stage compression mechanisms which perform compression in two stages are provided in parallel to each other, for example.
- In the refrigerant circuit, a plurality of usage-
side heat exchangers 6 may be disposed in parallel to each other. In this case, a refrigerant circuit may be used in which expansion mechanisms are disposed immediately ahead of the respective usage-side heat exchangers so that the quantity of refrigerant supplied to the usage-side heat exchangers 6 can be controlled, and the expansion mechanisms are also disposed in parallel to each other. - In the embodiment described above, an example was described in which the low-
stage compression element 2 c and the high-stage compression element 2 d were provided withseparate drive shafts compressor drive motors - However, the present invention is not limited to this example; another possibility is a
refrigerant circuit 10D which uses acompression mechanism 2 having a shareddrive shaft 121 c which is a drive shaft shared by the low-stage compression element 2 c and the high-stage compression element 2 d, wherein one sharedcompressor drive motor 121 b is used to transmit drive force to the shareddrive shaft 121 c, as shown inFIG. 7 , for example. - This
compression mechanism 2 has a hermetically sealed structure in which thecompressor drive motor 121 b, the shareddrive shaft 121 c, and thecompression elements casing 21 a. The sharedcompressor drive motor 121 b is linked to the shareddrive shaft 121 c. This shareddrive shaft 121 c is linked to the twocompression elements compression elements drive shaft 121 c, and the twocompression elements compressor drive motor 121 b. Thecompression elements stage compression element 2 c draws refrigerant in from anintake tube 2 a, compresses the drawn-in refrigerant, and discharges the refrigerant toward the intermediaterefrigerant tube 22. The intermediaterefrigerant tube 22 connects the discharge side of the low-stage compression element 2 c and the intake side of the high-stage compression element 2 d via theintercooler 7. The high-stage compression element 2 d further compresses the refrigerant drawn in via the intermediaterefrigerant tube 22 and then discharges the refrigerant to thedischarge tube 2 b. InFIG. 7 , thedischarge tube 2 b is a refrigerant tube for feeding the refrigerant discharged from thecompression mechanism 2 to the heat source-side heat exchanger 4, and thedischarge tube 2 b is provided with anoil separation mechanism 41 and anon-return mechanism 42. Theoil separation mechanism 41 is a mechanism for separating the refrigerant from refrigeration oil which accompanies the refrigerant discharged from thecompression mechanism 2 and returning the refrigeration oil to the intake side of thecompression mechanism 2, and theoil separation mechanism 41 has primarily anoil separator 41 a for separating the refrigerant from the refrigeration oil accompanying the refrigerant discharged from thecompression mechanism 2, and anoil return tube 41 b which is connected to theoil separator 41 a and which returns the refrigeration oil separated from the refrigerant to theintake tube 2 a of thecompression mechanism 2. Theoil return tube 41 b is provided with adepressurization mechanism 41 c for depressurizing the refrigeration oil flowing through theoil return tube 41 b. A capillary tube is used as thedepressurization mechanism 41 c. Thenon-return mechanism 42 is a mechanism for allowing the flow of refrigerant from the discharge side of thecompression mechanism 2 to the heat source-side heat exchanger 4 and blocking the flow of refrigerant from the heat source-side heat exchanger 4 to the discharge side of thecompression mechanism 2, and a non-return valve is used. - Thus, the
compression mechanism 2 has twocompression elements compression mechanism 2 is configured so that refrigerant discharged from the first-stage compression element of thesecompression elements - Since a single-shaft two-stage compression mechanism is used herein, the
control unit 99 drives the low-stage compression element 2 c and the high-stage compression element 2 d while causing their centrifugal forces to cancel each other out to suppress vibrations and/or fluctuations in torque load, and thecontrol unit 99 can perform control so that the operating capacity of the low-stage compression element 2 c and the operating capacity of the high-stage compression element 2 d are balanced, and the compression ratios are equal in the low-stage and high-stage elements. -
FIG. 8 is a schematic structural diagram of awater heater 201 as a refrigeration apparatus according to the second embodiment of the present invention. - Components in the second embodiment having the same specifics as those of the first embodiment are not described hereinbelow.
- (Water Circuit)
- The
water circuit 910 is the water circuit of the embodiment described above, but further having the flow rateratio adjustment mechanism 911 disposed at an intermediate point in theintermediate water tubes ratio adjustment mechanism 911 is controlled by thecontrol unit 99, and the ratio between the quantity of water flowing through the heatsource water tubes intermediate water tubes - (Refrigerant Circuit)
- The
refrigerant circuit 210 is the refrigerant circuit of the embodiment described above, but further having a liquid-gas heat exchanger 8, a liquid-gas three-way valve 8C, a liquid-gas bypass tube 8B, and connectingtubes - The liquid-
gas heat exchanger 8 has a liquid-side liquid-gas heat exchanger 8L through which passes the refrigerant flowing from the connectingtube 73 to the connectingtube 74, and a gas-side liquid-gas heat exchanger 8G through which passes the refrigerant flowing from the connectingtube 77 to theintake tube 2 a. The liquid-gas heat exchanger 8 performs heat exchange between the refrigerant flowing through the liquid-side liquid-gas heat exchanger 8L and the refrigerant flowing through the gas-side liquid-gas heat exchanger 8G. Although the description uses wording such as “liquid”-side “liquid”-gas heat exchanger 8, the refrigerant passing through the liquid-side liquid-gas heat exchanger 8L is not limited to a liquid state, and may be refrigerant in a supercritical state, for example. Nor is the refrigerant flowing through the gas-side liquid-gas heat exchanger 8G limited to refrigerant in a gas state, and refrigerant as moisture may flow through, for example. - The liquid-
gas bypass tube 8B connects one switching port of the liquid-gas three-way valve 8C connected to the connectingtube 73, which is on the upstream side of the liquid-side liquid-gas heat exchanger 8L, and an end of the connectingtube 74 extending downstream of the liquid-side liquid-gas heat exchanger 8L. - The liquid-gas three-
way valve 8C can switch between a liquid-gas usage connection state in which theconnection tube 72 extending from the heat source-side heat exchanger 4 is connected to the connectingtube 73 extending from the liquid-side liquid-gas heat exchanger 8L, and a liquid-gas non-usage connection state in which theconnection tube 72 extending from the heat source-side heat exchanger 4 is not connected to the connectingtube 73 extending from the liquid-side liquid-gas heat exchanger 8L but is connected to the liquid-gas bypass tube 8B. - Next, the action of the
water heater 201 of the second embodiment is described usingFIGS. 8 , 9, and 10. -
FIG. 9 is a pressure-enthalpy graph representing the refrigeration cycle, andFIG. 10 is a temperature-entropy graph representing the refrigeration cycle. - (Liquid-Gas Usage Connection State)
- In the liquid-gas usage connection state, the connection state of the liquid-gas three-
way valve 8C is switchably controlled by thecontrol unit 99 so that heat exchange is performed in the liquid-gas heat exchanger 8 between the refrigerant passing through the liquid-side liquid-gas heat exchanger 8L and the refrigerant passing through the gas-side liquid-gas heat exchanger 8G. - Herein, the refrigerant drawn in from the
intake tube 2 a of the low-stage compression element 2 c (refer to point A inFIGS. 9 and 10 ) is compressed by the low-stage compression element 2 c (refer to point B inFIGS. 9 and 10 ), and the refrigerant flowing through the intermediaterefrigerant tube 22 is cooled in theintercooler 7 by the water flowing through theintermediate water tubes 904, 905 (refer to point C inFIGS. 9 and 10 ). - Having been compressed to a pressure exceeding the critical pressure by the high-
stage compression element 2 d (refer to point D inFIGS. 9 and 10 ), the refrigerant is fed to the heat source-side heat exchanger 4. In the heat source-side heat exchanger 4, the water flowing through the heatsource water tubes side heat exchanger 4 in a supercritical state, heat is radiated to the exterior by the change in sensible heat while the refrigerant pressure remains constant in the heat radiation step, and the temperature of the refrigerant itself continuously decreases (refer to point K inFIGS. 9 and 10 ). Having exited the heat source-side heat exchanger 4, the refrigerant flows into the liquid-side liquid-gas heat exchanger 8L, where heat is further radiated due to heat exchange with the low-temperature, low-pressure gas refrigerant flowing through the gas-side liquid-gas heat exchanger 8G, and the temperature of the refrigerant itself continuously decreases further (refer to point L inFIGS. 9 and 10 ). Having exited the liquid-side liquid-gas heat exchanger 8L, the refrigerant is depressurized by the expansion mechanism 5 (refer to point M inFIGS. 9 and 10 ), and the refrigerant flows into the usage-side heat exchanger 6. In the usage-side heat exchanger 6, due to heat exchange with external air and/or water while the pressure remains constant, the refrigerant evaporates while the heat taken from the exterior is consumed in a change of latent heat, whereby the dryness of the refrigerant increases (refer to point P inFIGS. 9 and 10 ). Having exited the usage-side heat exchanger 6, the refrigerant evaporates further while undergoing a change in latent heat in the gas-side liquid-gas heat exchanger 8G due this time to the heat taken by heat exchange with the high-temperature, high-pressure refrigerant passing through the liquid-side liquid-gas heat exchanger 8L while the pressure remains constant, and the refrigerant reaches a superheated state above the dry saturated vapor curve at this pressure. This refrigerant in a superheated state is then drawn into the low-stage compression element 2 c through theintake tube 2 a (point A inFIGS. 9 and 10 ). This refrigerant circulation is repeated in the liquid-gas usage connection state. - (Liquid-Gas Non-Usage Connection State)
- In the liquid-gas non-usage connection state, the
control unit 99 controls the connection state of the liquid-gas three-way valve 8C and creates a state in which theconnection tube 72 and the liquid-gas bypass tube 8B are connected, so that heat exchange is not performed in the liquid-gas heat exchanger 8. - The points A, B, C, D, and K of
FIGS. 9 and 10 in the liquid-gas non-usage connection state are the same as in the liquid-gas usage connection state and are therefore not described. - The refrigerant that has exited the heat source-
side heat exchanger 4 herein flows through the liquid-gas bypass tube 8B to be depressurized in theexpansion mechanism 5 without flowing into the liquid-side liquid-gas heat exchanger 8L (refer to point L′ inFIGS. 9 and 10 ). The refrigerant is then depressurized in theexpansion mechanism 5, and the refrigerant flows into the usage-side heat exchanger 6 (refer to point M′ inFIGS. 9 and 10 ). In the usage-side heat exchanger 6, through heat exchange with external air and/or water while the pressure remains constant, the refrigerant evaporates while the heat taken from the exterior is consumed in a latent heat change, whereby the refrigerant reaches a superheated state above the dry saturated vapor curve at this pressure. This refrigerant in a superheated state is then drawn into the low-stage compression element 2 c through theintake tube 2 a (refer to point P′ inFIGS. 9 and 10 ). This refrigerant circulation is repeated in the liquid-gas non-usage connection state. - (Liquid-Gas Heat Exchanger Switching Control)
- The
control unit 99 performs the same control as the target capacity output control described inEmbodiment 1 above, and also performs liquid-gas heat exchanger switching control for switching between the above-described liquid-gas usage connection state and liquid-gas non-usage connection state. - In this liquid-gas heat exchanger switching control, the
control unit 99 switches the connection state of the liquid-gas three-way valve 8C in accordance with the temperature sensed by the usage-side temperature sensor 6T. - In the target capacity output control described above, the target evaporation temperature is established based on the temperature sensed by the usage-
side temperature sensor 6T, but when the temperature sensed by the usage-side temperature sensor 6T decreases and the target evaporation temperature is set to be even lower, the discharged refrigerant temperature increases under the control condition that the target discharge pressure of the high-stage compression element 2 d does not change (under the condition that the required radiated heat quantity must be guaranteed in the heat source-side heat exchanger 4). The reliability of the high-stage compression element 2 d is compromised when the discharged refrigerant temperature increases too much in this manner. Therefore, thecontrol unit 99 herein performs a control for bringing the connection state of the liquid-gas three-way valve 8C to the liquid-gas non-usage connection state. Thereby, even if the temperature sensed by the usage-side temperature sensor 6T decreases and the target evaporation temperature is set to be even lower, the extent of the increase in the degree of superheating of the refrigerant drawn in by the high-stage compression element 2 d can be minimized to minimize the increase in the discharged refrigerant temperature, and the required heat radiation quantity can be maintained. - On the other hand, in the target capacity output control described above, the target evaporation temperature is established based on the temperature sensed by the usage-
side temperature sensor 6T, but when the temperature sensed by the usage-side temperature sensor 6T increases and the target evaporation temperature is set to be even higher, the discharged refrigerant temperature decreases under the control condition that the target discharge pressure of the high-stage compression element 2 d does not change (under the condition that the required radiated heat quantity must be guaranteed in the heat source-side heat exchanger 4). In this case, it will sometimes not be possible to supply the heat source-side heat exchanger 4 with refrigerant having the required heat radiation quantity. In such cases, thecontrol unit 99 is capable of switching the connection state of the liquid-gas three-way valve 8C to the liquid-gas usage connection state, raising the degree of superheating of the refrigerant drawn into the high-stage compression element 2 d, and guaranteeing the heat radiation quantity required in the heat source-side heat exchanger 4. There are also cases in which it is possible to improve the coefficient of performance even when the required heat radiation quantity can be supplied in this manner. In such cases, thecontrol unit 99 is capable of guaranteeing the required heat radiation quantity and improving the coefficient of performance by switching the connection state of the liquid-gas three-way valve 8C to the liquid-gas usage connection state, lowering the specific enthalpy of the refrigerant drawn into theexpansion mechanism 5, and improving the refrigerating capacity of the refrigeration cycle. Since the refrigerant drawn into the low-stage compression element 2 c can be guaranteed to have the appropriate degree of superheating, it is possible to prevent the risk of liquid compression occurring in the low-stage compression element 2 c. - In the embodiment described above, an example was described in which the
control unit 99 switches the connection state of the liquid-gas three-way valve 8C on the basis of the temperature sensed by the usage-side temperature sensor 6T (on the basis of the established target evaporation temperature). - However, the present invention is not limited to this example; another possibility is to use a
refrigerant circuit 210A having a dischargedrefrigerant temperature sensor 2T for sensing the temperature of the refrigerant discharged from the high-stage compression element 2 d, instead of the usage-side temperature sensor 6T, as shown inFIG. 11 , for example. - With this discharged
refrigerant temperature sensor 2T, an increase in the temperature sensed by the usage-side temperature sensor 6T described above corresponds to a decrease in the temperature sensed by the dischargedrefrigerant temperature sensor 2T, and a decrease in the temperature sensed by the usage-side temperature sensor 6T described above corresponds to an increase in the temperature sensed by the dischargedrefrigerant temperature sensor 2T. That is, if the temperature sensed by the dischargedrefrigerant temperature sensor 2T is too high, it will not be possible to maintain the reliability of the high-stage compression element 2 d, and thecontrol unit 99 will therefore bring the connection state of the liquid-gas three-way valve 8C to the liquid-gas non-usage connection state, preventing the degree of superheating of the refrigerant drawn into the low-stage compression element 2 c from increasing. If the temperature sensed by the dischargedrefrigerant temperature sensor 2T decreases, it will not be possible to supply the heat radiation quantity required in the heat source-side heat exchanger 4, and thecontrol unit 99 therefore will bring the connection state of the liquid-gas three-way valve 8C to the liquid-gas usage connection state and increase the degree of superheating of the refrigerant drawn into the low-stage compression element 2 c, guaranteeing a capacity. In conditions in which the refrigerant drawn into the low-stage compression element 2 c has a low temperature and the temperature of the refrigerant discharged by the high-stage compression element 2 d does not increase excessively even if the degree of superheating has been raised, thecontrol unit 99 brings the connection state of the liquid-gas three-way valve 8C to the liquid-gas usage connection state and lowers the specific enthalpy of the refrigerant fed to theexpansion mechanism 5 to improve the refrigerating capacity of the refrigeration cycle, thereby raising the coefficient of performance. - In the embodiment described above, an example was described in which the connection state of the liquid-gas three-
way valve 8C is switched to switch between the liquid-gas usage connection state and the liquid-gas non-usage connection state. - However, the present invention is not limited to this example; another possibility is to cause refrigerant to flow to both the liquid-
gas bypass tube 8B and the liquid-gas heat exchanger 8L and control the refrigerant flow rate ratio of both refrigerant passages by adjusting the switched state of the liquid-gas three-way valve 8C, for example. - In the embodiment described above, an example was described of a refrigerant circuit provided with the liquid-gas three-
way valve 8C. - However, the present invention is not limited to this example; another possibility is to use a refrigerant circuit which has an on/off valve provided to the connecting
tube 73 and an on/off valve also provided to the liquid-gas bypass tube 8B, instead of the liquid-gas three-way valve 8C, for example. - In the embodiment described above, an example was described of a refrigerant circuit provided with only one two-stage compression mechanism, wherein refrigerant is compressed in two stages in the low-
stage compression element 2 c and the high-stage compression element 2 d. - However, the present invention is not limited to this example; another possibility is to use a refrigerant circuit wherein the aforementioned two-stage compression mechanisms which perform compression in two stages are provided in parallel to each other, for example.
- In the refrigerant circuit, a plurality of usage-
side heat exchangers 6 may be disposed in parallel to each other. In this case, a refrigerant circuit may be used in which expansion mechanisms are disposed immediately ahead of the respective usage-side heat exchangers and the expansion mechanisms are also disposed in parallel to each other so that the quantity of refrigerant supplied to the usage-side heat exchangers 6 can be controlled. - In the embodiment described above, an example was described in which the low-
stage compression element 2 c and the high-stage compression element 2 d were provided withseparate drive shafts compressor drive motors - However, the present invention is not limited to this example; another possibility is a
refrigerant circuit 210B which uses acompression mechanism 2 having a shareddrive shaft 121 c which is a drive shaft shared by the low-stage compression element 2 c and the high-stage compression element 2 d, wherein one sharedcompressor drive motor 121 b is used to transmit drive force to the shareddrive shaft 121 c, as shown inFIG. 12 , for example. - This
compression mechanism 2 has a hermetically sealed structure in which thecompressor drive motor 121 b, the shareddrive shaft 121 c, and thecompression elements casing 21 a. The sharedcompressor drive motor 121 b is linked to the shareddrive shaft 121 c. This shareddrive shaft 121 c is linked to the twocompression elements compression elements drive shaft 121 c, and the twocompression elements compressor drive motor 121 b. Thecompression elements stage compression element 2 c draws refrigerant in from anintake tube 2 a, compresses the drawn-in refrigerant, and discharges the refrigerant toward the intermediaterefrigerant tube 22. The intermediaterefrigerant tube 22 connects the discharge side of the low-stage compression element 2 c and the intake side of the high-stage compression element 2 d via theintercooler 7. The high-stage compression element 2 d further compresses the refrigerant drawn in via the intermediaterefrigerant tube 22 and then discharges the refrigerant to thedischarge tube 2 b. InFIG. 12 , thedischarge tube 2 b is a refrigerant tube for feeding the refrigerant discharged from thecompression mechanism 2 to the heat source-side heat exchanger 4, and thedischarge tube 2 b is provided with anoil separation mechanism 41 and anon-return mechanism 42. Theoil separation mechanism 41 is a mechanism for separating the refrigerant from refrigeration oil which accompanies the refrigerant discharged from thecompression mechanism 2 and returning the refrigeration oil to the intake side of thecompression mechanism 2, and theoil separation mechanism 41 has primarily anoil separator 41 a for separating the refrigerant from the refrigeration oil accompanying the refrigerant discharged from thecompression mechanism 2, and anoil return tube 41 b which is connected to theoil separator 41 a and which returns the refrigeration oil separated from the refrigerant to theintake tube 2 a of thecompression mechanism 2. Theoil return tube 41 b is provided with adepressurization mechanism 41 c for depressurizing the refrigeration oil flowing through theoil return tube 41 b. A capillary tube is used as thedepressurization mechanism 41 c. Thenon-return mechanism 42 is a mechanism for allowing the flow of refrigerant from the discharge side of thecompression mechanism 2 to the heat source-side heat exchanger 4 and blocking the flow of refrigerant from the heat source-side heat exchanger 4 to the discharge side of thecompression mechanism 2, and a non-return valve is used. - Thus, the
compression mechanism 2 has twocompression elements compression mechanism 2 is configured so that refrigerant discharged from the first-stage compression element of thesecompression elements - Since a single-shaft two-stage compression mechanism is used herein, the
control unit 99 drives the low-stage compression element 2 c and the high-stage compression element 2 d while causing their centrifugal forces to cancel each other out to suppress vibrations and/or fluctuations in torque load, and thecontrol unit 99 can perform control so that the operating capacity of the low-stage compression element 2 c and the operating capacity of the high-stage compression element 2 d are balanced, and the compression ratios are equal in the low-stage and high-stage elements. -
FIG. 13 is a schematic structural diagram of awater heater 301, which is a refrigeration apparatus according to the third embodiment of the present invention. - Components in the third embodiment that have the same specifications as those of the first embodiment are not described hereinbelow.
- (Water Circuit)
- The
water circuit 910 is the water circuit of the embodiment described above, but further having the flow rateratio adjustment mechanism 911 disposed at an intermediate point in theintermediate water tubes ratio adjustment mechanism 911 is controlled by thecontrol unit 99, and the ratio between the quantity of water flowing through the heatsource water tubes intermediate water tubes - (Refrigerant Circuit)
- The
refrigerant circuit 310 is the refrigerant circuit of the embodiment described above, but further having aneconomizer circuit 9, and connecting tubes 73 c, 74 c, etc. connecting the other components. - The
economizer circuit 9 has a branchingupstream tube 9 a branching off from a branching point X between theconnection tube 72 and the connecting tube 73 c, aneconomizer expansion mechanism 9 e for depressurizing refrigerant, a branchingmidstream tube 9 b for leading the refrigerant depressurized in theeconomizer expansion mechanism 9 e to theeconomizer heat exchanger 20, and a branchingdownstream tube 9 c for leading the refrigerant that has flowed out of theeconomizer heat exchanger 20 to a convergent point Y in the intermediaterefrigerant tube 22. - The connecting tube 73 c leads refrigerant through the
economizer heat exchanger 20 to a connectingtube 75 c. This connectingtube 75 c is connected to theexpansion mechanism 5. - The configuration is otherwise the same as that of the
water heater 1 of the first embodiment described above. - Next, the action of the
water heater 301 of the third embodiment will be described usingFIGS. 13 , 14, and 15. -
FIG. 14 is a pressure-enthalpy graph representing the refrigeration cycle, andFIG. 15 is a temperature-entropy graph representing the refrigeration cycle. - (Economizer Usage State)
- In an economizer usage state, refrigerant is caused to flow to the
economizer circuit 9 by adjusting the opening degree of theeconomizer expansion mechanism 9 e. - In the
economizer circuit 9, refrigerant that has branched off from the branching point X and flowed into the branchingupstream tube 9 a is depressurized in theeconomizer expansion mechanism 9 e (refer to point R inFIGS. 13 , 14, and 15), and the refrigerant flows into theeconomizer heat exchanger 20 via the branchingmidstream tube 9 b. - In the
economizer heat exchanger 20, heat exchange takes place between the refrigerant flowing through the connecting tube 73 c and the connectingtube 75 c (refer to point X→point Q inFIGS. 13 , 14, and 15), and the refrigerant flowing into theeconomizer heat exchanger 20 via the branchingmidstream tube 9 b (refer to point R→point Y inFIGS. 13 , 14, and 15). - At this time, the refrigerant flowing through the connecting tube 73 c and the connecting
tube 75 c is cooled by the refrigerant flowing through the branchingmidstream tube 9 b, which is being depressurized and reduced in temperature in theeconomizer heat exchanger 20, and the specific enthalpy decreases (refer to point X point Q inFIGS. 13 , 14, and 15). Thus, the degree of supercooling of the refrigerant fed to theexpansion mechanism 5 increases, whereby the refrigeration capacity of the refrigeration cycle increases and the coefficient of performance improves. The refrigerant whose specific enthalpy has decreased is depressurized by passing through theexpansion mechanism 5, and the refrigerant flows into the usage-side heat exchanger 6 (refer to point Q point M in FIGS. 13, 14, and 15). The refrigerant evaporates in the usage-side heat exchanger 6, and the refrigerant is drawn into the low-stage compression element 2 c (refer to point M point A inFIGS. 13 , 14, and 15). The refrigerant drawn into the low-stage compression element 2 c is compressed and increased in temperature, creating a state in which refrigerant increased in pressure to an intermediate pressure flows through the intermediaterefrigerant tube 22. - When the refrigerant flowing through the intermediate
refrigerant tube 22 passes through theintercooler 7, the refrigerant radiates heat upon heating the water flowing through theintermediate water tubes FIGS. 13 , 14, and 15). - The refrigerant flowing into the
economizer heat exchanger 20 via the branchingmidstream tube 9 b is heated by the refrigerant flowing through the connecting tube 73 c and the connectingtube 75 c, whereby the dryness of the refrigerant improves (refer to point R→point Y inFIGS. 13 , 14, and 15). - Thus, refrigerant that has passed through the economizer circuit 9 (refer to point Y in
FIGS. 13 , 14, an 15) mixes with refrigerant that has been cooled in theintercooler 7 while flowing through the intermediate refrigerant tube 22 (refer to point S inFIGS. 13 , 14, and 15) at the convergent point Y in the intermediaterefrigerant tube 22 described above, the refrigerant temperature decreases while the intermediate pressure is maintained, the degree of superheating of the refrigerant discharged from the low-stage compression element 2 c is reduced, and the refrigerant is drawn into the high-stage compression element 2 d (refer to points Y, S, and C inFIGS. 13 , 14, and 15). The temperature of the refrigerant drawn into the high-stage compression element 2 d thereby decreases, and it is therefore possible to prevent the temperature of the refrigerant discharged from the high-stage compression element 2 d from increasing excessively. The refrigerant density also increases due to the temperature of the refrigerant drawn into the high-stage compression element 2 d decreasing, and the quantity of refrigerant circulating through the heat source-side heat exchanger 4 is increased by the refrigerant injected via theeconomizer circuit 9; therefore, the capacity to supply refrigerant to the heat source-side heat exchanger 4 can be greatly improved. - In the economizer usage state, this manner of refrigerant circulation is repeated.
- (Economizer Non-Usage State)
- In the economizer non-usage state, the
economizer expansion mechanism 9 e in theeconomizer circuit 9 is brought to a fully closed state. A state thereby arises in which the flow of refrigerant in the branchingmidstream tube 9 b ceases and theeconomizer heat exchanger 20 does not function (refer to points Q′, M′, and D′ inFIGS. 13 , 14, and 15). - The cooling effects of the refrigerant flowing through the intermediate
refrigerant tube 22 thereby ceases, the temperature of the refrigerant discharged from the high-stage compression element 2 d therefore increases, and it is possible to comply with a high output water temperature requested by the user. - (Economizer Switching Control)
- The
control unit 99 performs the same control as the target capacity output control described inEmbodiment 1 described above, and performs economizer switching control for switching between the economizer usage state and the economizer non-usage state described above. - In this economizer switching control, the
control unit 99 controls the opening degree of theeconomizer expansion mechanism 9 e in accordance with the temperature sensed by the usage-side temperature sensor 6T. - In the target capacity output control described above, the target evaporation temperature is established based on the temperature sensed by the usage-
side temperature sensor 6T, but when the temperature sensed by the usage-side temperature sensor 6T decreases and the target evaporation temperature is set to be even lower, the discharged refrigerant temperature increases under the control condition that the target discharge pressure of the high-stage compression element 2 d does not change (under the condition that the required radiated heat quantity must be guaranteed in the heat source-side heat exchanger 4). The reliability of the high-stage compression element 2 d is compromised when the discharged refrigerant temperature increases too much in this manner. Therefore, thecontrol unit 99 herein performs a control for creating the economizer usage state, wherein theeconomizer heat exchanger 20 is made to function by opening theeconomizer expansion mechanism 9 e and causing refrigerant to flow to theeconomizer circuit 9. Thereby, even if the temperature sensed by the usage-side temperature sensor 6T decreases and the target evaporation temperature is set to be even lower, the extent of the increase in the temperature of the refrigerant drawn in by the high-stage compression element 2 d can be minimized to minimize the increase in the discharged refrigerant temperature, and the required heat radiation quantity can be maintained. - On the other hand, in the target capacity output control described above, the target evaporation temperature is established based on the temperature sensed by the usage-
side temperature sensor 6T, but when the temperature sensed by the usage-side temperature sensor 6T increases and the target evaporation temperature is set to be even higher, the discharged refrigerant temperature decreases under the control condition that the target discharge pressure of the high-stage compression element 2 d does not change (under the condition that the required radiated heat quantity must be guaranteed in the heat source-side heat exchanger 4). In this case, it will sometimes not be possible to supply the heat source-side heat exchanger 4 with refrigerant having the required heat radiation quantity. In such cases, thecontrol unit 99 is capable of creating the economizer non-usage state in which theeconomizer expansion mechanism 9 e is fully closed, ensuring that the degree of superheating of the refrigerant drawn in by the high-stage compression element 2 d does not decrease, and guaranteeing the heat radiation quantity required in the heat source-side heat exchanger 4. There are also cases in which it is possible to improve the coefficient of performance even when the required heat radiation quantity can be supplied in this manner. In such cases, thecontrol unit 99 is capable of guaranteeing the required heat radiation quantity and improving the coefficient of performance by opening theeconomizer expansion mechanism 9 e to create the economizer usage state, lowering the specific enthalpy of the refrigerant drawn into theexpansion mechanism 5, and improving the refrigerating capacity of the refrigeration cycle. - In the embodiment described above, an example was described in which the
control unit 99 switches the opening degree of theeconomizer expansion mechanism 9 e on the basis of the temperature sensed by the usage-side temperature sensor 6T (on the basis of the established target evaporation temperature). - However, the present invention is not limited to this example; another possibility is to use a
refrigerant circuit 310A having a dischargedrefrigerant temperature sensor 2T for sensing the temperature of the refrigerant discharged from the high-stage compression element 2 d, instead of the usage-side temperature sensor 6T, as shown inFIG. 16 , for example. - With this discharged
refrigerant temperature sensor 2T, an increase in the temperature sensed by the usage-side temperature sensor 6T described above corresponds to a decrease in the temperature sensed by the dischargedrefrigerant temperature sensor 2T, and a decrease in the temperature sensed by the usage-side temperature sensor 6T described above corresponds to an increase in the temperature sensed by the dischargedrefrigerant temperature sensor 2T. That is, if the temperature sensed by the dischargedrefrigerant temperature sensor 2T is too high, it will not be possible to maintain the reliability of, the high-stage compression element 2 d, and thecontrol unit 99 will therefore increase the opening degree of theeconomizer expansion mechanism 9 e to bring about the economizer usage state, preventing the discharged refrigerant temperature of the high-stage compression element 2 d from increasing excessively by reducing the degree of superheating of the refrigerant drawn into the low-stage compression element 2 c. If the temperature sensed by the dischargedrefrigerant temperature sensor 2T decreases, it will not be possible to supply the heat radiation quantity required in the heat source-side heat exchanger 4, and thecontrol unit 99 therefore will fully close theeconomizer expansion mechanism 9 e to bring about the economizer non-usage state and guarantee a capacity without reducing the degree of superheating of the refrigerant drawn into the high-stage compression element 2 d. In conditions in which the refrigerant drawn into the high-stage compression element 2 d has a low temperature and the temperature of the refrigerant discharged by the high-stage compression element 2 d does not increase excessively even if the degree of superheating has been raised, thecontrol unit 99 increases the opening degree of theeconomizer expansion mechanism 9 e to bring about the economizer usage state and lowers the specific enthalpy of the refrigerant fed to theexpansion mechanism 5 to improve the refrigerating capacity of the refrigeration cycle, thereby raising the coefficient of performance. - In the embodiment described above, an example was described in which the opening degree of the
economizer expansion mechanism 9 e is adjusted to switch between the economizer usage state and the economizer non-usage state. - However, the present invention is not limited to this example; another possibility is to control the flow rate ratio of the refrigerants flowing to the
economizer circuit 9 and the connectingtubes 73 c, 75 c by adjusting the valve opening degree of theeconomizer expansion mechanism 9 e, for example. - In the embodiment described above, an example was described of a refrigerant circuit provided with only one two-stage compression mechanism, wherein refrigerant is compressed in two stages in the low-
stage compression element 2 c and the high-stage compression element 2 d. - However, the present invention is not limited to this example; another possibility is to use a refrigerant circuit wherein the aforementioned two-stage compression mechanisms which perform compression in two stages are provided in parallel to each other, for example.
- In the refrigerant circuit, a plurality of usage-
side heat exchangers 6 may be disposed in parallel to each other. In this case, a refrigerant circuit may be used in which expansion mechanisms are disposed immediately ahead of the respective usage-side heat exchangers and the expansion mechanisms are also disposed in parallel to each other so that the quantity of refrigerant supplied to the usage-side heat exchangers 6 can be controlled. - In the embodiment described above, an example was described in which the low-
stage compression element 2 c and the high-stage compression element 2 d were provided with theseparate drive shafts compressor drive motors - However, the present invention is not limited to this example; another possibility is a
refrigerant circuit 310B which uses acompression mechanism 2 having a shareddrive shaft 121 c which is a drive shaft shared by the low-stage compression element 2 c and the high-stage compression element 2 d, wherein one sharedcompressor drive motor 121 b is used to transmit drive force to the shareddrive shaft 121 c, as shown inFIG. 17 , for example. - This
compression mechanism 2 has a hermetically sealed structure in which thecompressor drive motor 121 b, the shareddrive shaft 121 c, and thecompression elements casing 21 a. The sharedcompressor drive motor 121 b is linked to the shareddrive shaft 121 c. This shareddrive shaft 121 c is linked to the twocompression elements compression elements drive shaft 121 c, and the twocompression elements compressor drive motor 121 b. Thecompression elements stage compression element 2 c draws refrigerant in from anintake tube 2 a, compresses the drawn-in refrigerant, and discharges the refrigerant toward the intermediaterefrigerant tube 22. The intermediaterefrigerant tube 22 connects the discharge side of the low-stage compression element 2 c and the intake side of the high-stage compression element 2 d via theintercooler 7. The high-stage compression element 2 d further compresses the refrigerant drawn in via the intermediaterefrigerant tube 22 and then discharges the refrigerant to thedischarge tube 2 b. InFIG. 17 , thedischarge tube 2 b is a refrigerant tube for feeding the refrigerant discharged from thecompression mechanism 2 to the heat source-side heat exchanger 4, and thedischarge tube 2 b is provided with anoil separation mechanism 41 and anon-return mechanism 42. Theoil separation mechanism 41 is a mechanism for separating the refrigerant from refrigeration oil which accompanies the refrigerant discharged from thecompression mechanism 2 and returning the refrigeration oil to the intake side of thecompression mechanism 2, and theoil separation mechanism 41 has primarily anoil separator 41 a for separating the refrigerant from the refrigeration oil accompanying the refrigerant discharged from thecompression mechanism 2, and anoil return tube 41 b which is connected to theoil separator 41 a and which returns the refrigeration oil separated from the refrigerant to theintake tube 2 a of thecompression mechanism 2. Theoil return tube 41 b is provided with adepressurization mechanism 41 c for depressurizing the refrigeration oil flowing through theoil return tube 41 b. A capillary tube is used as thedepressurization mechanism 41 c. Thenon-return mechanism 42 is a mechanism for allowing the flow of refrigerant from the discharge side of thecompression mechanism 2 to the heat source-side heat exchanger 4 and blocking the flow of refrigerant from the heat source-side heat exchanger 4 to the discharge side of thecompression mechanism 2, and a non-return valve is used. - Thus, the
compression mechanism 2 has the twocompression elements compression mechanism 2 is configured so that refrigerant discharged from the first-stage compression element of thesecompression elements - Since a single-shaft two-stage compression mechanism is used herein, the
control unit 99 drives the low-stage compression element 2 c and the high-stage compression element 2 d while causing their centrifugal forces to cancel each other out to suppress vibrations and/or fluctuations in torque load, and thecontrol unit 99 can perform control so that the operating capacity of the low-stage compression element 2 c and the operating capacity of the high-stage compression element 2 d are balanced, and the compression ratios are equal in the low-stage and high-stage elements. -
FIG. 18 is a schematic structural diagram of awater heater 401, which is a refrigeration apparatus according to the fourth embodiment of the present invention. - Components in the fourth embodiment that have the same specifics as those of the first embodiment are not described herein.
- (Water Circuit)
- The
water circuit 910 is the water circuit of the embodiment described above, but further having the flow rateratio adjustment mechanism 911 disposed at an intermediate point in theintermediate water tubes ratio adjustment mechanism 911 is controlled by thecontrol unit 99, and the ratio between the quantity of water flowing through the heatsource water tubes intermediate water tubes - (Refrigerant Circuit)
- The
refrigerant circuit 410 is the refrigerant circuit of the embodiment described above, but further having the liquid-gas heat exchanger 8, a switching three-way valve 28C, the liquid-gas bypass tube 8B, theeconomizer circuit 9, and connectingtubes 74 g, 75 g, etc. connecting these components. - The liquid-
gas heat exchanger 8 has a liquid-side liquid-gas heat exchanger 8L through which passes the refrigerant flowing from the connectingtube 73 to the connectingtube 74, and a gas-side liquid-gas heat exchanger 8G through which passes the refrigerant flowing from the connectingtube 77 to theintake tube 2 a. The liquid-gas heat exchanger 8 performs heat exchange between the refrigerant flowing through the liquid-side liquid-gas heat exchanger 8L and the refrigerant flowing through the gas-side liquid-gas heat exchanger 8G. Although the description uses wording such as “liquid”-side “liquid”-gas heat exchanger 8, the refrigerant passing through the liquid-side liquid-gas heat exchanger 8L is not limited to a liquid state, and may be refrigerant in a supercritical state, for example. Nor is the refrigerant flowing through the gas-side liquid-gas heat exchanger 8G limited to refrigerant in a gas state, and refrigerant as moisture may flow through, for example. Anexpansion mechanism 95 e is provided at an intermediate point in the connectingtube 74. - The liquid-
gas bypass tube 8B connects one switching port of the switching three-way valve 28C connected to the connectingtube 73, which is on the upstream side of the liquid-side liquid-gas heat exchanger 8L, and an end of the connectingtube 74 extending downstream of the liquid-side liquid-gas heat exchanger 8L. - The switching three-
way valve 28C can switch between a liquid-gas state in which theconnection tube 72 extending from the heat source-side heat exchanger 4 is connected to the connectingtube 73 extending from the liquid-side liquid-gas heat exchanger 8L, and an economizer state in which theconnection tube 72 extending from the heat source-side heat exchanger 4 is not connected to the connectingtube 73 extending from the liquid-side liquid-gas heat exchanger 8L but is connected to the liquid-gas bypass tube 8B. By fully closing theeconomizer expansion mechanism 9 e in the economizer state, a dual-function non-usage state can be brought about in which neither theeconomizer circuit 9 nor the liquid-gas heat exchanger 8 are used. - The
economizer circuit 9 has a branchingupstream tube 9 a branching off from a branching point X between the liquid-gas bypass tube 8B and the connecting tube 74 g, aneconomizer expansion mechanism 9 e for depressurizing refrigerant, a branchingmidstream tube 9 b for leading the refrigerant depressurized in theeconomizer expansion mechanism 9 e to theeconomizer heat exchanger 20, and a branchingdownstream tube 9 c for leading the refrigerant that has flowed out of theeconomizer heat exchanger 20 to a convergent point Y in the intermediaterefrigerant tube 22. - The connecting tube 74 g leads refrigerant through the
economizer heat exchanger 20 to a connectingtube 75 g. This connectingtube 75 g is connected to theexpansion mechanism 5. - The refrigerant that has passed through the liquid-side liquid-
gas heat exchanger 8L and the refrigerant that has passed through theeconomizer heat exchanger 20 mix together at a convergent point L and flow into the usage-side heat exchanger 6 via theconnection tube 76. - The
control unit 99 can switch between the economizer state, the liquid-gas state, and the dual-function non-usage stage by adjusting the connection state of the switching three-way valve 28C and the opening degree of theeconomizer expansion mechanism 9 e. - The configuration otherwise has the same specifics as those described in the above-described
water heater 1 of the first embodiment, thewater heater 201 of the second embodiment, and/or thewater heater 301 of the third embodiment. - Next, the action of the
water heater 401 of the fourth embodiment will be described usingFIGS. 18 , 19, and 20. -
FIG. 19 is a pressure-enthalpy graph representing the refrigeration cycle, andFIG. 20 is a temperature-entropy graph representing the refrigeration cycle. - Between the specific enthalpy at point Q in the economizer state and the specific enthalpy at point T in the liquid-gas state, whichever has the greater value changes depending on the opening degree of the
expansion mechanism 5 and/or theexpansion mechanism 95 e, and these specific enthalpies are therefore not limited to the examples shown inFIGS. 19 and 20 . - (Economizer State)
- In the economizer state, the
control unit 99 switches the connection state of the switching three-way valve 28C so that refrigerant does not flow to the connectingtube 73 but refrigerant does flow to the liquid-gas bypass tube 8B, increases the opening degree of theeconomizer expansion mechanism 9 e, and performs the refrigeration cycle so that the refrigerant flows to theeconomizer circuit 9. The same refrigeration cycle as in the economizer usage state in Embodiment 3 described above is performed here, as shown by points A, B, C, D, K, X, R, Y, Q, L, and P inFIGS. 18 , 19, and 20. - The specific enthalpy of the refrigerant flowing through the connecting
tube 75 g into theexpansion mechanism 5 herein can be lowered by heat exchange in theeconomizer heat exchanger 20, and the refrigerating capacity of the refrigeration cycle can be improved to bring the coefficient of performance to a satisfactory value. Furthermore, the degree of superheating of the refrigerant drawn into the high-stage compression element 2 d can be further reduced by the refrigerant passing through theeconomizer circuit 9 and mixing at the convergent point Y of the intermediaterefrigerant tube 22, rather than by theintercooler 7 alone, the density of the refrigerant drawn into thecompression element 2 d can be raised to improve compression efficiency, and abnormal increases in the discharged refrigerant temperature can be prevented. At this time, injection into the intermediaterefrigerant tube 22 via theeconomizer circuit 9 makes it possible to increase the quantity of refrigerant supplied to the heat source-side heat exchanger 4 and to increase the quantity of heat supplied as well. - (Liquid-Gas State)
- In the liquid-gas state, the
control unit 99 switches the connection state of the switching three-way valve 28C so that refrigerant does not flow to the liquid-gas bypass tube 8B but does flow to the connectingtube 73, and performs a refrigeration cycle that makes the liquid-gas heat exchanger 8 function. The same refrigeration cycle as in the liquid-gas usage connection state inEmbodiment 2 described above is performed here, as shown by points A, B, C′, D, K, T, L′, and P′ inFIGS. 18 , 19, and 20. - The specific enthalpy of the refrigerant flowing into the
expansion mechanism 95 e here can be lowered; therefore, the refrigerating capacity in the refrigeration cycle can be improved to bring the coefficient of performance to a satisfactory value, a degree of superheating can be guaranteed in the refrigerant drawn into the low-stage compression element 2 c to prevent liquid compression, and the discharge temperature can be increased to guarantee the heat quantity required in the heat source-side heat exchanger 4. - (Dual-Function Non-Usage State)
- In the dual-function non-usage state, the
control unit 99 switches the connection state of the switching three-way valve 28C so that refrigerant does not flow to the connectingtube 73 but does flow to the liquid-gas bypass tube 8B, fully closes theeconomizer expansion mechanism 9 e, and performs the refrigeration cycle so that neither theeconomizer circuit 9 nor the liquid-gas heat exchanger 8 are used. A simple refrigeration cycle is performed here, as shown by points A, B, C, D″, K, X, Q″, L″, and P inFIGS. 18 , 19, and 20. - Since the temperature of the refrigerant discharged from the high-
stage compression element 2 d can be increased here, it is possible to supply the required heat quantity even in cases in which the radiated heat quantity required in the heat source-side heat exchanger 4 has increased. - (Switching Control of Economizer State, Liquid-Gas State, and Dual-Function Non-Usage State)
- The
control unit 99 performs a control for switching the above-described states such that the first priority is that the discharged refrigerant temperature be within a range of not increasing abnormally and the discharged refrigerant pressure be a pressure equal to or less than the pressure capacity of the low-stage compression element 2 c and the high-stage compression element 2 d, the second priority is that the output water temperature and output water quantity requested by the user be achieved, and the third priority is that the operating efficiency be satisfactory (that an appropriate balance can be established between improving the coefficient of performance and increasing compression efficiency). - That is, in cases in which the radiated heat quantity of the refrigerant in the heat source-
side heat exchanger 4 is insufficient, control is performed such that the liquid-gas state goes into effect if the discharge temperature is within a range of not increasing abnormally, and the dual-function non-usage state goes into effect if an abnormal increase in the discharge temperature is avoided. In cases in which the heat radiation quantity in the heat source-side heat exchanger 4 is sufficient, the economizer state goes into effect, the opening degree of theeconomizer expansion mechanism 9 e is controlled, the valve opening degree is increased within a margin whereby the heat radiation quantity required in the heat source-side heat exchanger 4 can be supplied, the coefficient of performance is brought to a satisfactory value by improving the refrigerating capacity of the refrigeration cycle, and control is performed for increasing the supplied heat quantity by increasing the quantity of refrigerant that can be supplied to the heat source-side heat exchanger 4. - The heat radiation quantity herein is determined by the
control unit 99 on the basis of the temperature sensed by thewater temperature sensor 910T, as well as the output water temperature and the output water quantity required by the user. Whether or not the discharge temperature has increased abnormally is determined by thecontrol unit 99 on the basis of (the evaporation temperature established corresponding to) the temperature sensed by the usage-side temperature sensor 6T. - In the embodiment described above, an example was described of a case in which the
control unit 99 performs a control for switching between the economizer state, the liquid-gas state, and the dual-function non-usage state. - However, the present invention is not limited to this example; another possibility is to allow the use of a dual-usage state in which the
economizer circuit 9 is used while the liquid-gas heat exchanger 8 is used as well, for example. - On the preconditions that the discharged refrigerant temperature of the high-
stage compression element 2 d be within a range of not increasing abnormally, the discharged refrigerant pressure be one equal to or less than the pressure capacity of the low-stage compression element 2 c and the high-stage compression element 2 d, and it be possible to supply the output water temperature and output water quantity requested by the user, for example, thecontrol unit 99 herein may control the ratio between the flow rate of refrigerant flowing through theeconomizer circuit 9 and the flow rate of the liquid-gas heat exchanger 8L while refrigerant is flowing simultaneously to both theeconomizer circuit 9 and the liquid-gas heat exchanger 8L, rather than simply alternately switching the connection state of the switching three-way valve 28C, so that the operating efficiency can be made satisfactory (an appropriate balance can be established between improving the coefficient of performance and increasing compression efficiency). The configuration which can adjust the ratio herein is not limited to the switching three-way valve 28C, and an expansion mechanism may be provided immediately ahead of the liquid-gas heat exchanger 8L to perform flow rate ratio control, for example. - For the ratio between the flow rate in the
economizer circuit 9 and the flow rate in the liquid-gas heat exchanger 8, thecontrol unit 99 herein ensures that the discharged refrigerant temperature of the high-stage compression element 2 d is within a range of not increasing abnormally (under conditions such as the temperature of the refrigerant discharged from the high-stage compression element 2 d being equal to or less than a predetermined temperature) when the target evaporation temperature is established based on the temperature sensed by the usage-side temperature sensor 6T, and also that the discharged refrigerant pressure is equal to or less than the pressure capacity of the low-stage compression element 2 c and the high-stage compression element 2 d; and thecontrol unit 99 calculates a heat quantity sufficient to guarantee the output water temperature and output water quantity requested by the user. - Assuming that the flow rate of the
economizer circuit 9 is zero, for example, thecontrol unit 99 then calculates a flow rate of the liquid-gas heat exchanger 8L needed in order to guarantee a radiated heat quantity, whereby abnormal increases in the discharged refrigerant temperature at the target evaporation temperature can be prevented, and the discharge pressure is equal to or less than a predetermined pressure corresponding to the pressure capacity of the low-stage compression element 2 c and the high-stage compression element 2 d. Next, while reducing this calculated flow rate in the liquid-gas heat exchanger 8L and assuming that refrigerant equivalent to the reduced flow rate has flowed to theeconomizer circuit 9, thecontrol unit 99 controls the flow rate ratio so that the respective compression ratios of the low-stage compression element 2 c and the high-stage compression element 2 d are within a predetermined range and the coefficient of performance is within a predetermined range, while taking into account the decrease in the refrigerating capacity resulting from the increase in specific enthalpy accompanying the decrease in the flow rate of the liquid-gas heat exchanger 8, the increase in the refrigerating capacity resulting from the decrease in specific enthalpy accompanying the increase in the flow rate of theeconomizer circuit 9, the increase in the compression ratio of the compression mechanism resulting from the high pressure increasing in order to guarantee the heat radiation quantity by increasing the flow rate of theeconomizer circuit 9, and the increase in the supplied heat amount accompanying the increase in the refrigerant density supplied to the heat source-side heat exchanger 4 resulting from the increase in the flow rate of theeconomizer circuit 9. - For example, in this flow rate control by the
control unit 99, an intermediate pressure at which the compression ratio of the low-stage compression element 2 c and the compression ratio of the high-stage compression element 2 d are equal may be calculated as the intermediate pressure for minimizing the compression work, and theeconomizer expansion mechanism 9 e may be controlled so that the extent of depressurization in theeconomizer expansion mechanism 9 e yields this intermediate pressure (and pressures within a predetermined range from this intermediate pressure), whereupon the flow rate ratio in the switching three-way valve 28C may be adjusted so that the coefficient of performance is satisfactory. - In the embodiment described above, an example was described in which the
control unit 99 switches the opening degree of the switching three-way valve 28C and/or theeconomizer expansion mechanism 9 e on the basis of the temperature sensed by the usage-side temperature sensor 6T (on the basis of the established target evaporation temperature). - However, the present invention is not limited to this example; another possibility is to use a
refrigerant circuit 410A having a dischargedrefrigerant temperature sensor 2T for sensing the temperature of the refrigerant discharged from the high-stage compression element 2 d, instead of the usage-side temperature sensor 6T, as shown inFIG. 21 , for example. - With this discharged
refrigerant temperature sensor 2T, an increase in the temperature sensed by the usage-side temperature sensor 6T described above corresponds to a decrease in the temperature sensed by the dischargedrefrigerant temperature sensor 2T, and a decrease in the temperature sensed by the usage-side temperature sensor 6T described above corresponds to an increase in the temperature sensed by the dischargedrefrigerant temperature sensor 2T. - In the embodiment described above, an example was described of a case in which the connection state of the switching three-
way valve 28C is switched to switch between the liquid-gas state, the economizer state, and the dual-function non-usage state. - However, the present invention is not limited to this example; another possibility is to use a refrigerant circuit which has an on/off valve provided to the connecting tube 73 g and an on/off valve also provided to the connecting
tube 73, instead of the switching three-way valve 28C, for example. - In the embodiment described above, an example was described of a
refrigerant circuit 410 provided with both anexpansion mechanism 5 and anexpansion mechanism 95 e. - However, the present invention is not limited to this example; another possibility is to use a
refrigerant circuit 410B having a dual-use expansion mechanism 405B which can be used both in control during the economizer state and control during the liquid-gas state, as shown inFIG. 22 , for example. This dual-use expansion mechanism 405B is provided at an intermediate point in a connectingtube 76 g extending from the convergent point L to the usage-side heat exchanger 6. - In this case, the number of expansion mechanisms can be reduced to fewer than that of the
refrigerant circuit 410 in the fourth embodiment described above. - In the embodiment described above, an example was described of a
refrigerant circuit 410 in which the branching point X which branches in theeconomizer circuit 9 is bypassed by the liquid-gas heat exchanger 8. - However, the present invention is not limited to this example; another possibility is to use a
refrigerant circuit 410C in which the branching point X which branches in theeconomizer circuit 9 is provided between a dual-use expansion mechanism 405C and a convergent point V between the connectingtube 74 and the liquid-gas bypass tube 8B which extends from the liquid-gas three-way valve 8C for switching between the liquid-gas state and the economizer state, as shown inFIG. 23 , for example. - Furthermore, another possibility is to use a
refrigerant circuit 410D in which the branching point X which branches in theeconomizer circuit 9 is provided between the liquid-gas three-way valve 8C and the heat source-side heat exchanger 4, as shown inFIG. 24 . - In this
refrigerant circuit 410D, the connection in the liquid-gas three-way valve 8C is switched between leading to the connectingtube 73 and leading to the liquid-gas bypass tube 8B. The refrigerant that has passed through the liquid-gas heat exchanger 8L then passes through the connectingtube 74 and mixes at the convergent point L with the liquid-gas bypass tube 8B. The connectingtube 76 g and a dual-use expansion mechanism 405D are provided between this convergent point L and the usage-side heat exchanger 6. - In the embodiment described above, an example was described of a refrigerant circuit provided with only one two-stage compression mechanism, wherein refrigerant is compressed in two stages in the low-
stage compression element 2 c and the high-stage compression element 2 d. - However, the present invention is not limited to this example; another possibility is to use a refrigerant circuit wherein the above-described two-stage compression mechanisms which perform compression in two stages are provided in parallel to each other, for example.
- In the refrigerant circuit, a plurality of usage-
side heat exchangers 6 may be disposed in parallel to each other. In this case, a refrigerant circuit may be used in which expansion mechanisms are disposed immediately ahead of the respective usage-side heat exchangers and the expansion mechanisms are also disposed in parallel to each other so that the quantity of refrigerant supplied to the usage-side heat exchangers 6 can be controlled. - In the embodiment described above, an example was described in which the low-
stage compression element 2 c and the high-stage compression element 2 d were provided with theseparate drive shafts compressor drive motors - However, the present invention is not limited to this example; another possibility is a
refrigerant circuit 410E which uses acompression mechanism 2 having a shareddrive shaft 121 c which is a drive shaft shared by the low-stage compression element 2 c and the high-stage compression element 2 d, wherein one sharedcompressor drive motor 121 b is used to transmit drive force to the shareddrive shaft 121 c, as shown inFIG. 25 , for example. - This
compression mechanism 2 has a hermetically sealed structure in which thecompressor drive motor 121 b, the shareddrive shaft 121 c, and thecompression elements casing 21 a. The sharedcompressor drive motor 121 b is linked to the shareddrive shaft 121 c. This shareddrive shaft 121 c is linked to the twocompression elements compression elements drive shaft 121 c, and the twocompression elements compressor drive motor 121 b. Thecompression elements stage compression element 2 c draws refrigerant in from anintake tube 2 a, compresses the drawn-in refrigerant, and discharges the refrigerant toward the intermediaterefrigerant tube 22. The intermediaterefrigerant tube 22 connects the discharge side of the low-stage compression element 2 c and the intake side of the high-stage compression element 2 d via theintercooler 7. The high-stage compression element 2 d further compresses the refrigerant drawn in via the intermediaterefrigerant tube 22 and then discharges the refrigerant to thedischarge tube 2 b. InFIG. 25 , thedischarge tube 2 b is a refrigerant tube for feeding the refrigerant discharged from thecompression mechanism 2 to the heat source-side heat exchanger 4, and thedischarge tube 2 b is provided with anoil separation mechanism 41 and anon-return mechanism 42. Theoil separation mechanism 41 is a mechanism for separating the refrigerant from refrigeration oil which accompanies the refrigerant discharged from thecompression mechanism 2 and returning the refrigeration oil to the intake side of thecompression mechanism 2, and theoil separation mechanism 41 has primarily anoil separator 41 a for separating the refrigerant from the refrigeration oil accompanying the refrigerant discharged from thecompression mechanism 2, and anoil return tube 41 b which is connected to theoil separator 41 a and which returns the refrigeration oil separated from the refrigerant to theintake tube 2 a of thecompression mechanism 2. Theoil return tube 41 b is provided with adepressurization mechanism 41 c for depressurizing the refrigeration oil flowing through theoil return tube 41 b. A capillary tube is used as thedepressurization mechanism 41 c. Thenon-return mechanism 42 is a mechanism for allowing the flow of refrigerant from the discharge side of thecompression mechanism 2 to the heat source-side heat exchanger 4 and blocking the flow of refrigerant from the heat source-side heat exchanger 4 to the discharge side of thecompression mechanism 2, and a non-return valve is used. - Thus, the
compression mechanism 2 has twocompression elements compression mechanism 2 is configured so that refrigerant discharged from the first-stage compression element of thesecompression elements - Since a single-shaft two-stage compression mechanism is used herein, the
control unit 99 drives the low-stage compression element 2 c and the high-stage compression element 2 d while causing their centrifugal forces to cancel each other out to suppress vibrations and/or fluctuations in torque load, and thecontrol unit 99 can perform control so that the operating capacity of the low-stage compression element 2 c and the operating capacity of the high-stage compression element 2 d are balanced, and the compression ratios are equal in the low-stage and high-stage elements. - Embodiments of the present invention and modifications thereof were described above based on the drawings, but the specific configuration is not limited to these embodiments and their modifications; other changes can be made within a range that does not deviate from the scope of the invention.
- For example, in the embodiments and their modifications described above, the present invention may be applied to a so-called chiller-type air-conditioning apparatus in which water and/or brine is used as the heating source or cooling source for performing heat exchange with the refrigerant flowing through the usage-
side heat exchanger 6, and a secondary heat exchanger is provided for performing heat exchange between indoor air and the water and/or brine that has undergone heat exchange in the usage-side heat exchanger 6. - The present invention can also be applied even to a refrigeration apparatus of a type different from the aforementioned chiller-type air-conditioning apparatus, such as a cooling-only air-conditioning apparatus or the like.
- The refrigerant that operates in a supercritical range is not limited to carbon dioxide; ethylene, ethane, nitric oxide, and the like may also be used.
- In the refrigeration apparatus of the present invention, since compression efficiency can be more reliably improved in the refrigeration apparatus and the heating of the water for the hot water supply can be made more efficient, the refrigeration apparatus is particularly useful in cases in which the present invention is applied to a refrigeration apparatus which has multi-stage compression-type compression elements and which uses refrigerant that operates including the supercritical state process as the active refrigerant.
-
- 1 Air-conditioning apparatus (refrigeration apparatus)
- 2 Compression mechanism
- 4 Heat source-side heat exchanger
- 5 Expansion mechanism
- 6 Usage-side heat exchanger
- 7 Intercooler
- 8 Liquid-gas heat exchanger
- 10 Refrigerant circuit
- 20 Economizer heat exchanger
- 22 Intermediate refrigerant tube
- 99 Control unit
- 902, 903 Heat source water tubes
- 904, 905 Intermediate water tubes
- 910 Water circuit
- 911 Flow rate ratio adjustment mechanism
- Japanese Laid-open Patent Application No. 2007-232263
- Japanese Laid-open Patent Application No. 2002-106988
Claims (16)
1. A refrigeration apparatus which performs heat exchange on a water tube system having a water inlet tube to lead water supplied from an exterior to a water branching point, first branching water tubes and second branching water tubes extending from the water branching point, and a water outlet tube leading out to the exterior from a convergent point where the first branching water tubes and the second branching water tubes converge, active refrigerant being in a supercritical state in at least part of a refrigeration cycle; the refrigeration apparatus comprising:
a main expansion mechanism arranged and configured to depressurize the refrigerant;
an evaporator connected to the main expansion mechanism, the evaporator being arranged and configured to evaporate refrigerant;
a first compression element arranged and configured to draw refrigerant that has passed through the evaporator, and to compress and discharge the refrigerant drawn into the first compression element;
a second compression element arranged and configured to draw in the refrigerant discharged from the first compression element and to compress and discharge the refrigerant drawn into the second compression element;
a first refrigerant tube arranged and configured to draw the refrigerant discharged from the first compression element into the second compression element;
a first heat exchanger arranged and configured to perform heat exchange between the refrigerant passing through the first refrigerant tube and the water flowing through the first branching water tubes;
second refrigerant tubes arranged and configured to connect a discharge side of the second compression element and the main expansion mechanism; and
a second heat exchanger arranged and configured to such that refrigerant passing through the second refrigerant tubes
exchanges heat with the water flowing through the second branching water tubes, and
does not exchange heat with the water flowing through the water inlet tube.
2. The refrigeration apparatus according to claim 1 , further comprising:
a flow rate ratio adjustment mechanism arranged and configured to adjust a ratio between a quantity of water flowing through the first branching water tubes and a quantity of water flowing through the second branching water tubes.
3. The refrigeration apparatus according to claim 2 , further comprising:
a heating capacity detection unit arranged and configured to detect
a capacity of the refrigerant passing through the first heat exchanger to heat the water and
a capacity of the refrigerant passing through the second heat exchanger to heat the water; and
a water distribution quantity control unit arranged and configured to adjust the ratio between the quantity of water flowing through the first branching water tubes and the quantity of water flowing through the second branching water tubes by controlling the flow rate adjustment mechanism in accordance with a ratio between the heating capacities of the first heat exchanger and the second heat exchanger detected by the heating capacity detection unit.
4. The refrigeration apparatus according to claim 1 , wherein
the second refrigerant tubes have a third refrigerant tube connecting the second heat exchanger and the main expansion mechanism; and the refrigeration apparatus further comprises:
a fourth refrigerant tube arranged and configured to connect the evaporator and an intake side of the first compression element;
a third heat exchanger arranged and configured to perform heat exchange between the refrigerant flowing through the third refrigerant tube and the refrigerant flowing through the fourth refrigerant tube;
a third heat exchange bypass tube arranged and configured to connect one end and another end of a portion of the third refrigerant tube that passes through the third heat exchanger; and
a heat exchanger switching mechanism arranged and configured to switch between
a state in which refrigerant flows through the portion of the third refrigerant tube that passes through the third heat exchanger, and
a state in which refrigerant flows through the third heat exchange bypass tube.
5. The refrigeration apparatus according to claim 4 , further comprising:
temperature sensory units arranged and configured to sense a value of at least an air temperature surrounding the evaporator or a discharged refrigerant temperature of at least the first compression element or the second compression element; and
a heat exchange quantity control unit arranged and configured to control the heat exchanger switching mechanism and to increase the quantity of refrigerant flowing through the portion of the third refrigerant tube that passes through the third heat exchanger when
the air temperature is higher than a predetermined high-temperature air temperature when a value sensed by the temperature sensory units is an air temperature, or
the refrigerant temperature is lower than a predetermined low-temperature refrigerant temperature when the value sensed by the temperature sensory units is a refrigerant temperature.
6. The refrigeration apparatus according to claim 1 , wherein
the second refrigerant tubes have a third refrigerant tube connecting the second heat exchanger and the main expansion mechanism; and the refrigeration apparatus further comprises:
a branching expansion mechanism arranged and configured to depressurize refrigerant;
a fifth refrigerant tube which branches off from the third refrigerant tube and extends to the branching expansion mechanism;
sixth refrigerant tubes extending from the branching expansion mechanism to the first refrigerant tube; and
a fourth heat exchanger arranged and configured to perform heat exchange between refrigerant flowing through the third refrigerant tube and refrigerant flowing through the sixth refrigerant tubes.
7. The refrigeration apparatus according to claim 6 , further comprising:
temperature sensory units arranged and configured to sense a value of at least an air temperature surrounding the evaporator or a discharged refrigerant temperature of at least the first compression element or the second compression element; and
a branched quantity control unit arranged and configured to control the branching expansion mechanism and to increase the quantity of refrigerant passing therethrough when
the air temperature is lower than a predetermined low-temperature air temperature when the value sensed by the temperature sensory units is an air temperature, or
the refrigerant temperature is higher than a predetermined high-temperature refrigerant temperature when the value sensed by the temperature sensory units is a refrigerant temperature.
8. The refrigeration apparatus according to claim 6 , further comprising:
a water temperature sensory unit arranged and configured to sense a temperature of water flowing through any position in the water tube system;
a first refrigerant temperature sensory unit arranged and configured to sense a temperature of refrigerant passing through the first refrigerant tube; and
a refrigerant distribution quantity control unit arranged and configured to control the branching expansion mechanism and to increase the quantity of refrigerant passing therethrough when a difference between the temperature sensed by the water temperature sensory unit and the temperature sensed by the first refrigerant temperature sensory unit is less than a predetermined value.
9. The refrigeration apparatus according to claim 1 , wherein
the second refrigerant tubes have a third refrigerant tube connecting the second heat exchanger and the main expansion mechanism; and the refrigeration apparatus further comprises:
a branching expansion mechanism arranged and configured to depressurize refrigerant;
fourth refrigerant tubes connecting the evaporator and an intake side of the first compression element;
a third heat exchanger arranged and configured to perform heat exchange between refrigerant flowing through the third refrigerant tube and refrigerant flowing through the fourth refrigerant tubes;
a fifth refrigerant tube which branches off from the third refrigerant tube and extends to the branching expansion mechanism;
sixth refrigerant tubes connecting the branching expansion mechanism and the first refrigerant tube; and
a fourth heat exchanger arranged and configured to perform heat exchange between refrigerant flowing through the third refrigerant tube and refrigerant flowing through the sixth refrigerant tubes.
10. The refrigeration apparatus according to claim 9 , further comprising:
temperature sensory units arranged and configured to sense a value of at least the air temperature surrounding the evaporator or the discharged refrigerant temperature of at least the first compression element or the second compression element; and
a branched heat quantity control unit arranged and configured to control the branching expansion mechanism and to increase quantity of refrigerant passing therethrough when
the air temperature is lower than a predetermined low-temperature air temperature when the value sensed by the temperature sensory units is an air temperature, or
the refrigerant temperature is higher than a predetermined high-temperature refrigerant temperature when the value sensed by the temperature sensory units is a refrigerant temperature.
11. The refrigeration apparatus according to claim 9 , further comprising:
a first heat exchange bypass tube connecting one end and another end of a portion of the first refrigerant tube that passes through the first heat exchanger; and
a bypass switching mechanism arranged and configured to switch between
a state in which refrigerant flows through the portion of the first refrigerant tube that passes through the first heat exchanger, and
a state in which refrigerant flows through the first heat exchange bypass tube.
12. The refrigeration apparatus according to claim 11 , further comprising:
temperature sensory units arranged and configured to sense a value of at least an air temperature surrounding the evaporator or a discharged refrigerant temperature of at least the first compression element or the second compression element; and
a bypass control unit arranged and configured to control the bypass switching mechanism and to increase using the quantity of refrigerant flowing through the portion of the first refrigerant tube that passes through the first heat exchanger when
the air temperature is higher than a predetermined high-temperature air temperature when the value sensed by the temperature sensory units is an air temperature, or
the refrigerant temperature is lower than a predetermined low-temperature refrigerant temperature when the value sensed by the temperature sensory units is a refrigerant temperature.
13. The refrigeration apparatus according to claim 9 , further comprising:
a water temperature sensory unit arranged and configured to sense a temperature of water flowing through any position in the water tube system;
a first refrigerant temperature sensory unit arranged and configured to sense a for sensing the temperature of refrigerant passing through the first refrigerant tube; and
a water-correspondent refrigerant quantity control unit arranged and configured to cont the branching expansion mechanism and to increase the quantity of refrigerant passing therethrough when a difference between the temperature sensed by the water temperature sensory unit and the temperature sensed by the first refrigerant temperature sensory unit is less than a predetermined value.
14. The refrigeration apparatus according to claim 1 , further comprising:
a first drive unit arranged and configured to drive the first compression element; and
a second drive unit arranged and configured to drive the second compression element independently of the first compression element.
15. The refrigeration apparatus according to claim 1 , wherein
the first compression element and the second compression element have a shared rotating shaft in order to perform compression work by rotatably driving each of the first and second compression elements.
16. The refrigeration apparatus according to claim 1 , wherein
the active refrigerant is carbon dioxide.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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JP2008-120738 | 2008-05-02 | ||
JP2008120738A JP5181813B2 (en) | 2008-05-02 | 2008-05-02 | Refrigeration equipment |
PCT/JP2009/058311 WO2009133868A1 (en) | 2008-05-02 | 2009-04-28 | Refrigeration unit |
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US20110036110A1 true US20110036110A1 (en) | 2011-02-17 |
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US12/989,440 Abandoned US20110036110A1 (en) | 2008-05-02 | 2009-04-28 | Refrigeration apparatus |
Country Status (8)
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US (1) | US20110036110A1 (en) |
EP (1) | EP2309209B1 (en) |
JP (1) | JP5181813B2 (en) |
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CN (1) | CN102016449B (en) |
AU (1) | AU2009240983B2 (en) |
ES (1) | ES2869938T3 (en) |
WO (1) | WO2009133868A1 (en) |
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AU2009240983B2 (en) | 2012-08-09 |
KR20110015582A (en) | 2011-02-16 |
WO2009133868A1 (en) | 2009-11-05 |
AU2009240983A1 (en) | 2009-11-05 |
JP2009270747A (en) | 2009-11-19 |
EP2309209B1 (en) | 2021-03-24 |
ES2869938T3 (en) | 2021-10-26 |
EP2309209A4 (en) | 2014-11-19 |
CN102016449A (en) | 2011-04-13 |
JP5181813B2 (en) | 2013-04-10 |
EP2309209A1 (en) | 2011-04-13 |
CN102016449B (en) | 2013-12-25 |
KR101213257B1 (en) | 2012-12-18 |
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