US20070151266A1 - Refrigeration cycle apparatus - Google Patents
Refrigeration cycle apparatus Download PDFInfo
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- US20070151266A1 US20070151266A1 US11/612,958 US61295806A US2007151266A1 US 20070151266 A1 US20070151266 A1 US 20070151266A1 US 61295806 A US61295806 A US 61295806A US 2007151266 A1 US2007151266 A1 US 2007151266A1
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- refrigerant
- compressor
- expander
- flow rate
- control valve
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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
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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
- F25B41/00—Fluid-circulation arrangements
- F25B41/30—Expansion means; Dispositions thereof
- F25B41/39—Dispositions with two or more expansion means arranged in series, i.e. multi-stage expansion, on a refrigerant line leading to the same 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
- F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
- F25B9/06—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point using expanders
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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
- F25B1/04—Compression machines, plants or systems with non-reversible cycle with compressor of rotary 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
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
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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
- 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
- F25B2400/14—Power generation using energy from the expansion of the refrigerant
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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
- F25B2400/23—Separators
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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
- F25B2600/00—Control issues
- F25B2600/25—Control of valves
- F25B2600/2509—Economiser valves
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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
- F25B2600/00—Control issues
- F25B2600/25—Control of valves
- F25B2600/2515—Flow valves
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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
- F25B2700/21151—Temperatures of a compressor or the drive means therefor at the suction 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
- F25B2700/2115—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
Definitions
- the present invention relates to a refrigeration cycle apparatus applied to hot water heaters, air-conditioners, and the like, and more particularly to a configuration and a control method therefor that achieve high efficiency by mixing a refrigerant that flows through a bypass circuit with a refrigerant that is in the process of compression.
- a known refrigeration cycle apparatus uses a fluid machine in which both a positive displacement compressor and a positive displacement expander are coupled uniaxially so that the energy of expansion of the refrigerant recovered by the expander can be used as auxiliary driving power for the compressor.
- the compressor and the expander constantly rotate at the same frequency.
- the intake capacity of the compressor and the intake capacity of the expander are also constant. Therefore, theoretically, the ratio between the density pc of the compressor's intake refrigerant and the density pe of the expander's intake refrigerant is constant at all times.
- the refrigeration cycle apparatus is not permitted to operate outside that constraint.
- such an apparatus originally is intended to achieve high cycle efficiency by the power recovery with the use of the expander, it does not necessarily achieve a high efficiency operation.
- FIG. 12 illustrates a system that employs a bypass circuit for resolving such an issue.
- This system is provided with a control valve 12 for variably adjusting the passage area of the bypass circuit 11 .
- the opening of the control valve 12 to regulate the refrigerant flow rate passing through the expander 4 variably the mass flow rate of the refrigerant that passes through the compressor 3 and the mass flow rate of the refrigerant that passes through the expander 4 may be made different from each other.
- the conventional constraint of constant density ratio on the cycle operation is eliminated (see, for example, JP 2001-116371A ( FIG. 1 )).
- JP 2003-121018A discloses a refrigeration cycle apparatus including a compressor and an expander that are coupled directly by a single shaft.
- the refrigeration cycle apparatus has an expansion valve arranged in series with the expander, and a bypass valve for bypassing the expander.
- a gas-liquid separator is provided between the expander and the expansion valve so that the gas refrigerant separated from the liquid refrigerant by the gas-liquid separator is introduced to an intermediate pressure portion of the compressor.
- the present invention provides refrigeration cycle apparatus including:
- an evaporator for heating the refrigerant expanded by the expander and supplying the refrigerant to the compressor
- bypass circuit including a flow rate control valve and a gas-liquid separator that is provided downstream from the flow rate control valve and that is for separating the refrigerant passed through the flow rate control valve into a gas refrigerant and a liquid refrigerant, one end of the bypass circuit being connected to an intake conduit of the expander and the other end of the bypass circuit being connected to a discharge conduit of the expander so that a portion of the refrigerant passed through the radiator bypasses the expander and is guided to the flow rate control valve and that the liquid refrigerant separated by the gas-liquid separator returns to the discharge conduit of the expander; and
- the present invention by allowing a portion of the refrigerant flowing out of the radiator to flow through the bypass circuit, the constraint of constant density ratio can be avoided. Moreover, since the liquid refrigerant and the gas refrigerant are separated by the gas-liquid separator provided in the bypass circuit and the gas refrigerant is injected into the intermediate pressure portion of the compressor, the refrigerant flow rate through the radiator can be increased.
- the specific enthalpy of the liquid refrigerant that flows out of the gas-liquid separator and returns to the discharge conduit of the expander is smaller than the specific enthalpy of the refrigerant (gas-liquid two-phase refrigerant) that has been expanded by the expander.
- the specific enthalpy of the refrigerant at the inlet of the evaporator lowers and the enthalpy difference between the inlet and the outlet of the evaporator increases, leading to an improvement in the refrigerating capacity. Furthermore, the injection circuit enables the gas refrigerant flowing out of the gas-liquid separator to be mixed with the refrigerant that is in the compression process, preventing liquid compression from occurring in the compressor and thus ensuring a high degree of reliability of the compressor.
- the present invention provides a refrigeration cycle apparatus including:
- an evaporator for heating the refrigerant expanded by the expander and supplying the refrigerant to the compressor
- bypass circuit including a flow rate control valve, one end of the bypass circuit being connected to an intake conduit of the expander and the other end of the bypass circuit being connected to an intermediate pressure portion of the compressor so that a portion of the refrigerant passed through the radiator bypasses the expander and is guided to the flow rate control valve;
- an intake temperature sensor for detecting the refrigerant after flowing out of the evaporator but before being taken into the compressor
- a controller for controlling an opening of the flow rate control valve according to a detection result detected by the intake temperature sensor.
- the refrigerant flow rate through the radiator can be increased while the constraint of constant density ratio is avoided. Therefore, the overall performance of the refrigeration cycle apparatus can be improved.
- FIG. 1 is a configuration diagram illustrating a refrigeration cycle apparatus according to a first embodiment of the present invention
- FIG. 2 is a vertical cross-sectional view illustrating one example of a fluid machine including a compressor and an expander;
- FIG. 3 is a view illustrating one example of injection ports provided in the compressor
- FIG. 4 is a Mollier diagram illustrating the refrigeration cycle according to the first embodiment of the present invention.
- FIG. 5 is a control flow diagram of the refrigeration cycle apparatus according to the first embodiment of the present invention.
- FIG. 6 is a configuration diagram illustrating a refrigeration cycle apparatus according to a second embodiment of the present invention.
- FIG. 7 is a configuration diagram illustrating a refrigeration cycle apparatus according to a third embodiment of the present invention.
- FIG. 8 is a configuration diagram illustrating a refrigeration cycle apparatus according to a fourth embodiment of the present invention.
- FIG. 9 is a configuration diagram illustrating a refrigeration cycle apparatus according to a fifth embodiment of the present invention.
- FIG. 10 is a Mollier diagram illustrating the refrigeration cycle according to the fifth embodiment of the present invention.
- FIG. 11 is a control flow diagram of the refrigeration cycle apparatus according to the fifth embodiment of the present invention.
- FIG. 12 is a configuration diagram illustrating a conventional refrigeration cycle apparatus.
- FIG. 1 is a configuration diagram illustrating a refrigeration cycle apparatus according to a first embodiment of the present invention.
- a refrigeration cycle apparatus 100 A of the present embodiment is furnished with a compressor 101 for compressing a refrigerant such as hydrofluorocarbon or carbon dioxide, a radiator 102 for cooling the refrigerant compressed by the compressor 101 , an expander 103 for decompressing and expanding the refrigerant cooled by the radiator 102 and recovering mechanical power from the refrigerant under expansion, an evaporator 104 for heating the refrigerant decompressed by the expander 103 , and a plurality of main pipes 116 (main conduits) for connecting the compressor 101 , the radiator 102 , the expander 103 , and the evaporator 104 in that order.
- the compressor 101 , the radiator 102 , the expander 103 , the evaporator 104 , and the main pipes 116 constitute a main circuit 117 through which the refrigerant circulates.
- FIG. 2 is a vertical cross-sectional view illustrating one example of fluid machine including the compressor 101 and the expander 103 of this kind, and according to the present embodiment, the refrigeration cycle apparatus 100 A includes such a fluid machine 200 .
- mechanical power obtained by the expander 103 is supplied to a shaft 7 and is utilized as auxiliary driving power for the compressor 101 , which contributes to reducing the power consumption of the motor 6 . Since the expander 103 and the compressor 101 revolve at the same frequency at all times, the refrigeration cycle apparatus including the fluid machine 200 is constrained by the constraint of constant density ratio.
- the refrigeration cycle apparatus 100 A is, as illustrated in FIG. 1 , further furnished with a bypass circuit 113 , one end of which is connected to one of the main pipes 116 that is between the radiator 102 and the expander 103 and the other end of which is connected to another one of the main pipes 116 that is between the expander 103 and the evaporator 104 , so that a portion of the refrigerant that has passed through the radiator 102 bypasses the expander 103 .
- the former of the main pipes 116 is an intake conduit of the expander 103 and is also a discharge conduit of the radiator 102 .
- the latter of the main pipes 116 is a discharge conduit of the expander 103 and is also an intake conduit of the evaporator 104 .
- the bypass circuit 113 includes a first flow rate control valve 105 , a gas-liquid separator 110 provided downstream from the first flow rate control valve 105 , and a plurality of bypass pipes 115 .
- the refrigerant that bypasses the expander 103 is introduced to the first flow rate control valve 105 .
- the gas-liquid separator 110 has the function of separating the refrigerant that has passed through the first flow rate control valve 105 into a gas refrigerant and a liquid refrigerant, and it has a liquid outlet portion and a gas outlet portion.
- a bypass pipe 115 is connected to the liquid outlet portion so that the gas-liquid two-phase refrigerant that has changed from the liquid refrigerant into the gas-liquid two-phase refrigerant can be returned to one of the main pipes 116 that is between the expander 103 and the evaporator 104 .
- the refrigeration cycle apparatus 100 A further includes an injection circuit 109 , one end of which is connected to the gas outlet portion of the gas-liquid separator 110 and the other end of which is connected to an intermediate pressure portion of the compressor 101 (an intermediate pressure portion of the main circuit 117 ).
- the injection circuit 109 includes a second flow rate control valve 108 and a plurality of injection pipes 119 . A portion or all of the gas refrigerant that has been separated from the liquid refrigerant by the gas-liquid separator 110 is injected into the intermediate pressure portion of the compressor 101 through the injection circuit 109 .
- the intermediate pressure portion of the compressor 101 can be a portion of the interior of the compressor 101 that faces the refrigerant flow channel, that is, a portion thereof that faces a compression chamber 28 .
- the compressor 101 is a scroll-type compressor in which the compression chamber 28 is formed between a stationary scroll 21 and an orbiting scroll 22 , and an injection port 120 provided in the stationary scroll 21 serves as the intermediate pressure portion.
- One of the injection pipes 119 is connected to the injection port 120 .
- the injection port 120 is located between an intake port 21 a and an outlet port 21 b in the refrigerant flow channel within the compressor 101 .
- the gas refrigerant that has flowed out of the gas outlet portion of the gas-liquid separator 110 passes through the injection circuit 109 , is injected into the compression chamber 28 through the injection port 120 , and is mixed with the refrigerant that is being compressed.
- An injection port 120 may be provided at one location in the stationary scroll 21 , or, as illustrated in FIG. 3 , a plurality of injection ports 120 , 120 may be provided at a plurality of locations in the stationary scroll 21 .
- the type of the compressor is not limited to the scroll type, and may be other types of positive displacement compressors such as a rotary type compressor.
- the type of the expander is not limited either, although FIG. 2 shows a two-stage rotary compressor as the expander 103 .
- intermediate pressure is intended to mean a pressure that is between a high pressure and a low pressure in the refrigeration cycle, in other words, a pressure between the pressure of the refrigerant flowing into the radiator 102 and the pressure of the refrigerant flowing out of the evaporator 104 .
- the bypass circuit 113 further may include a throttling device 114 provided downstream from the gas-liquid separator 110 .
- the throttling device 114 may be a common expansion valve.
- Such a throttling device 114 is capable of changing the liquid refrigerant flowing out of the gas-liquid separator 110 into a gas-liquid two-phase refrigerant. This allows the gas-liquid two-phase refrigerant to be returned to the main pipe 116 that is between the expander 103 and the evaporator 104 , which is advantageous in maintaining a desired operating condition.
- the first flow rate control valve 105 the second flow rate control valve 108 , and the throttling device 114 have a common function, so the same kind of expansion valves may be used for them.
- two temperature sensors 111 and 112 be provided as a means for detecting the temperature of the refrigerant that circulates in the main circuit 117 .
- One of the temperature sensors 111 is an intake temperature sensor that detects the temperature of the refrigerant after flowing out of the evaporator 104 but before being taken into the compressor 101 , and it detects what is called a superheat temperature.
- the other one of the temperature sensors 112 is an outlet temperature sensor that detects the temperature of the refrigerant after being discharged from the compressor 101 but before flowing into the radiator 102 .
- a controller 107 which controls the openings of the first flow rate control valve 105 and the throttling device 114 of the bypass circuit 113 as well as the opening of the second flow rate control valve 108 of the injection circuit 109 .
- Signals that can identify the temperatures of the refrigerant are input from the two temperature sensors 111 and 112 to the controller 107 .
- the controller 107 controls the openings of the first flow rate control valve 105 , the throttling device 114 , and the second flow rate control valve 108 according to the signals from the temperature sensors 111 and 112 . This makes it possible to optimize the efficiency of the refrigeration cycle apparatus 100 A.
- the change of the refrigerant circulating in the main circuit 117 is represented as A ⁇ B ⁇ C ⁇ D ⁇ E ⁇ F ⁇ A.
- the refrigerant flowing through the bypass circuit 113 is branched at point E, which corresponds to the portion of the main circuit 117 that is between the radiator 102 and the expander 103 , is then decompressed to point G by the first flow rate control valve 105 , and is thereafter separated into a gas refrigerant and a liquid refrigerant by the gas-liquid separator 110 .
- the liquid refrigerant which is in the state of point H on the saturated liquid curve, is decompressed to point I by the throttling device 114 , and is then merged with the refrigerant being at point F, which is discharged from the expander 103 .
- the specific enthalpy of the refrigerant that has been discharged from the expander 103 and merged with the liquid refrigerant from the bypass circuit 113 is represented by point J.
- the gas refrigerant separated from the liquid refrigerant by the gas-liquid separator 110 flows into the compressor 101 and merges with the refrigerant at point B, which is the refrigerant under compression.
- the specific enthalpy of the refrigerant that has undergone the merge with the refrigerant being compressed by the compressor 101 and the gas refrigerant injected from the injection circuit 109 is represented by point C.
- the refrigerant flow rate flowing through the radiator 102 is the sum of the refrigerant flow rate Ge flowing through the evaporator 104 and the refrigerant flow rate Gi flowing through the bypass circuit 106 , and thus is represented as (Ge+Gi); therefore, the amount of heat exchanged by the radiator increases. In this way, it is possible to improve the performance of the refrigeration cycle apparatus 100 A while avoiding the constraint of constant density ratio.
- the refrigeration cycle will be balanced so that the intake density of the compressor 101 increases. Accordingly, when the intake superheat of the compressor 101 needs to be reduced, the opening of the first flow rate control valve 105 provided in the bypass circuit 113 should be increased.
- the specific enthalpy at point C becomes smaller, and thereby, the refrigerant discharge temperature (point D) of the compressor 101 can be controlled to be lower.
- the refrigeration cycle will be balanced so that the refrigerant discharge temperature of the compressor 101 decreases.
- the opening of the second flow rate control valve 108 provided in the injection circuit 109 should be decreased.
- the control procedure for the first flow rate control valve 105 and the second flow rate control valve 108 executed by the controller 107 will be described with reference to the flowchart of FIG. 5 .
- the tolerance t 1 may be set to be about 5% of the target superheat TH 1 .
- step 302 it is assessed whether or not the actual superheat temperature T 1 is greater than the target superheat TH 1 . If the actual superheat temperature T 1 is greater than the target superheat TH 1 , the process proceeds to step 303 , in which a control process for increasing the opening of the first flow rate control valve 105 is executed. When the opening of the first flow rate control valve 105 is increased, the refrigerant flow rate flowing through the bypass circuit 113 increases; therefore, the refrigeration cycle will be balanced so that the superheat temperature T 1 decreases.
- step 302 if it is assessed at step 302 that the actual superheat temperature T 1 is lower than the target superheat TH 1 , the process proceeds to step 304 , in which a control process for decreasing the opening of the first flow rate control valve 105 is executed. Thereby, the refrigeration cycle will be balanced so that the superheat temperature T 1 rises, and therefore, the superheat temperature can be controlled so as to approach the target value.
- step 305 it is assessed at step 305 whether or not the difference between an actual refrigerant discharge temperature T 2 detected by the outlet temperature sensor 112 and a target refrigerant discharge temperature TH 2 falls within the tolerance range ⁇ t 2 (dead zone).
- the tolerance t 2 may be set to be about 5% of the target refrigerant discharge temperature, for example. If it is assessed that the difference between the actual refrigerant discharge temperature T 2 and the target refrigerant discharge temperature TH 2 falls within the tolerance range ⁇ t 2 , the control process is terminated.
- step 305 if it is assessed at step 305 that the difference between the actual refrigerant discharge temperature T 2 and the target refrigerant discharge temperature TH 2 (absolute value) is greater than the tolerance t 2 , the process proceeds to step 306 , in which it is assessed whether or not the actual refrigerant discharge temperature T 2 is greater than the target refrigerant discharge temperature TH 2 . If the actual refrigerant discharge temperature T 2 is greater than the target refrigerant discharge temperature TH 2 , the process proceeds to step 307 , in which a control process for increasing the opening of the second flow rate control valve 108 is executed.
- step 306 If it is assessed at step 306 that the actual refrigerant discharge temperature T 2 is lower than the target refrigerant discharge temperature TH 2 , the process proceeds to step 308 , in which a control process for decreasing the opening of the second flow rate control valve 108 is executed.
- the refrigeration cycle will be balanced so that the refrigerant discharge temperature T 2 rises, and therefore, the refrigerant discharge temperature can be controlled so as to approach the target value.
- the specific enthalpy at point C increases, and the refrigerant discharge temperature T 2 of the compressor 101 (temperature at point D) rises.
- the opening of the second flow rate control valve 108 is changed, the process returns to step 301 .
- adjusting the openings of the first flow rate control valve 105 and the second flow rate control valve 108 to control the superheat temperature and the refrigerant discharge temperature enables the system performance to be kept optimally high while avoiding the constraint of constant density ratio.
- the foregoing has described an embodiment in which the openings of the first and second flow rate control valves 105 and 108 are adjusted using the superheat temperature and the refrigerant discharge temperature of the compressor 101 .
- the openings of the first and second flow rate control valves 105 and 108 may be controlled by one or a plurality of parameters selected from the group consisting of the superheat temperature, the refrigerant discharge temperature of the compressor 101 , the high pressure of the refrigeration cycle, the evaporator temperature, and the frequency of the compressor 101 , in addition to the combination of the superheat temperature and the refrigerant discharge temperature of the compressor 101 .
- the first embodiment has described the case in which the injection circuit 109 is connected directly to the compressor 101 .
- the refrigeration cycle apparatus according to the second embodiment differs from the first embodiment in that it has a plurality of compressors. It should be noted, however, that the advantageous effects achieved by the bypass circuit and the injection circuit are common between the second embodiment and the first embodiment.
- a refrigeration cycle apparatus 100 B of the second embodiment is furnished with a low-pressure-side compressor 101 A, and a high-pressure-side compressor 101 B connected in series with the low-pressure-side compressor 101 A via one of the main pipes 116 .
- a multi-stage compressor including the low-pressure-side compressor 101 A and the high-pressure-side compressor 101 B is employed as the compressor for compressing a refrigerant.
- the intermediate pressure portion of the compressors 101 A and 101 B, to which the injection circuit 109 is connected may be the main pipe 116 that is a joint portion for joining the low-pressure-side compressor 101 A and the high-pressure-side compressor 101 B.
- the injection circuit 109 and the compressors 101 A, 101 B can be connected by connecting the injection pipe 119 and the main pipe 116 , so the designing and assembling of the apparatus are made easy.
- a connecting component such as a joint may be provided between the injection pipe 119 and the main pipe 116 .
- the compressor that is coupled uniaxially to the expander 103 may be either the low-pressure-side compressor 101 A or the high-pressure-side compressor 101 B.
- the type of each of the compressors 101 A and 101 B is not particularly limited, and various types of positive displacement compressors such as a scroll type, a rotary type, or a reciprocating type compressor may be employed suitably.
- the type of the compressor that is not coupled uniaxially to the expander 103 may be a centrifugal compressor.
- FIG. 7 illustrates a configuration diagram of a refrigeration cycle apparatus according to a third embodiment.
- a refrigeration cycle apparatus 100 C shown in FIG. 7 differs from that of the first embodiment in that an injection circuit 109 ′ further includes an injector 123 provided downstream from the second flow rate control valve 108 .
- the present embodiment is similar to the first embodiment, and in the drawings, the same reference numerals designate the same components.
- the injector 123 in the injection circuit 109 ′ is capable of switching between an open state that permits passage of the refrigerant (gas refrigerant) and a closed state that inhibits passage of the refrigerant, and it may be, for example, a solenoid valve controlled by the controller 107 .
- the present embodiment makes it possible to control even the timing of injecting the gas refrigerant into the intermediate pressure portion of the compressor 101 .
- the second flow rate control valve 108 may be omitted and only the injector 123 of this kind may be provided.
- the injector 123 may be disposed inside the shell of the compressor 101 .
- FIG. 8 illustrates a configuration diagram of a refrigeration cycle apparatus according to a fourth embodiment.
- a refrigeration cycle apparatus 100 D shown in FIG. 8 additionally has a liquid refrigerant return circuit 125 for enabling the expander 103 to take in the liquid refrigerant that has been separated from the gas refrigerant by the gas-liquid separator 110 , in addition to the elements of the refrigeration cycle apparatus of the first embodiment.
- the liquid refrigerant return circuit 125 may be constituted by a similar pipe such as that used for the main pipes 116 and the bypass pipes 115 .
- One end of the liquid refrigerant return circuit 125 is connected to a portion of the bypass circuit 113 that is between the liquid outlet portion of the gas-liquid separator 110 and the throttling device 114 .
- the other end of the liquid refrigerant return circuit 125 is connected to the intake conduit of the expander 103 (corresponding to a portion of the main pipes 116 ) downstream from the branching location to the bypass circuit 113 .
- One end of the liquid refrigerant return circuit 125 may be connected to the liquid outlet portion of the gas-liquid separator 110 , and the other end thereof may be connected to the inlet (or a neighboring part of the inlet) of the expander 103 .
- the throttling device 114 By restricting the opening of the throttling device 114 , a portion of the liquid refrigerant separated from the gas refrigerant by the gas-liquid separator 110 can be supplied to the liquid refrigerant return circuit 125 . After circulating through the liquid refrigerant return circuit 125 , the liquid refrigerant is taken into the expander 103 . Thus, the refrigerant flow rate through the expander 103 can be increased, and therefore, the amount of power recovery can be increased and further improvement in the efficiency can be expected. Of course, the constraint of constant density ratio can be avoided because of the working of the injection circuit 109 .
- liquid refrigerant return circuit 125 may include a flow rate control valve (not shown).
- FIG. 9 illustrates a configuration diagram of a refrigeration cycle apparatus according to a fifth embodiment.
- a refrigeration cycle apparatus 100 E is furnished with a main circuit 117 and a bypass circuit 106 .
- the configuration of the main circuit 117 is the same as that of the other embodiments, but the configuration of the bypass circuit 106 is different from that of the other embodiments.
- the bypass circuit 106 connects the intake conduit of the expander 103 and the intermediate pressure portion of the compressor 101 via the first flow rate control valve 105 , and it is the circuit for introducing a portion of the refrigerant that has passed through the radiator 102 to the intermediate pressure portion of the compressor 101 .
- the injection port(s) 120 (see FIG. 2 ) of the compressor 101 may be used as the intermediate pressure portion of the compressor 101 .
- the change of the refrigerant circulating in the main circuit 117 is represented as A ⁇ B ⁇ C ⁇ D ⁇ E ⁇ F ⁇ A.
- the refrigerant flowing through the bypass circuit 106 is branched at point E, which corresponds to the portion of the main circuit 117 that is between the radiator 102 and the expander 103 , is then decompressed to point G by the first flow rate control valve 105 , and thereafter is introduced into the intermediate pressure portion of the compressor 101 , which is represented as point C.
- the refrigerant flow rate flowing through the radiator 102 is the sum of the refrigerant flow rate Ge flowing through the evaporator 104 and the refrigerant flow rate Gi flowing through the bypass circuit 106 , and thus is represented as (Ge+Gi); therefore, the amount of heat exchanged by the radiator increases. In this way, it is possible to improve the performance of the refrigeration cycle apparatus 100 E while avoiding the constraint of constant density ratio.
- the volume flow rate of the refrigerant that passes through the compressor 101 is represented as VC; the refrigerant density at the inlet of the compressor 101 is DC; the volume flow rate of the refrigerant that passes through the expander 103 is VE; the refrigerant density at the inlet of the expander 103 is DE; and the mass flow rate ratio of the refrigerant that flows through the bypass circuit 113 with respect to the total refrigerant is h, whereby the mass flow rate ratio of the refrigerant that flows through the expander 103 can be expressed as (1 ⁇ h). It should be noted that the mass flow rate ratio of the compressor 101 is approximated as “1.”
- VC ⁇ DC:VE ⁇ DE 1:(1 ⁇ h) (1)
- VE ⁇ DE (1 ⁇ h) ⁇ VC ⁇ DC (2)
- the control procedure for the first flow rate control valve 105 executed by the controller 107 will be described with reference to the flowchart of FIG. 11 .
- the tolerance ti may be set to be about 5% of the target superheat TH 1 . If it is assessed that the difference between the actual superheat temperature T 1 and the target superheat TH 1 falls within the tolerance range ⁇ t 1 , the control process is terminated.
- step 202 in which it is assessed whether or not the actual superheat temperature T 1 is greater than the target superheat TH 1 . If the actual superheat temperature T 1 is greater than the target superheat TH 1 , the process proceeds to step 203 , in which a control process for increasing the opening of the first flow rate control valve 105 is executed. Increasing the opening of the first flow rate control valve 105 results in a greater refrigerant flow rate flowing through the bypass circuit 106 , and therefore, the refrigeration cycle will be balanced so that the superheat temperature T 1 decreases.
- step 202 If it is assessed at step 202 that the actual superheat temperature T 1 is lower than the target superheat TH 1 , the process proceeds to step 204 , in which a control process for decreasing the opening of the first flow rate control valve 105 is executed. Thereby, the refrigeration cycle will be balanced so that the superheat temperature T 1 increases, and therefore the superheat temperature can be controlled to be closer to the target value.
- the bypass circuit 106 may include an injector 123 (see FIG. 7 ) as described in the third embodiment.
- the refrigeration cycle apparatus according to the present invention can be used for not only hot water heaters and air-conditioners but also for other various electric appliances such as dish dryers and garbage dryers.
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Abstract
Description
- 1. Field of the Invention
- The present invention relates to a refrigeration cycle apparatus applied to hot water heaters, air-conditioners, and the like, and more particularly to a configuration and a control method therefor that achieve high efficiency by mixing a refrigerant that flows through a bypass circuit with a refrigerant that is in the process of compression.
- 2. Description of Related Art
- A known refrigeration cycle apparatus uses a fluid machine in which both a positive displacement compressor and a positive displacement expander are coupled uniaxially so that the energy of expansion of the refrigerant recovered by the expander can be used as auxiliary driving power for the compressor. In this kind of refrigeration cycle apparatus, the compressor and the expander constantly rotate at the same frequency. Unless some special mechanism is provided, the intake capacity of the compressor and the intake capacity of the expander are also constant. Therefore, theoretically, the ratio between the density pc of the compressor's intake refrigerant and the density pe of the expander's intake refrigerant is constant at all times. When this constraint of constant density ratio exists, the refrigeration cycle apparatus is not permitted to operate outside that constraint. Thus, although such an apparatus originally is intended to achieve high cycle efficiency by the power recovery with the use of the expander, it does not necessarily achieve a high efficiency operation.
-
FIG. 12 illustrates a system that employs a bypass circuit for resolving such an issue. This system is provided with acontrol valve 12 for variably adjusting the passage area of thebypass circuit 11. By adjusting the opening of thecontrol valve 12 to regulate the refrigerant flow rate passing through the expander 4 variably, the mass flow rate of the refrigerant that passes through thecompressor 3 and the mass flow rate of the refrigerant that passes through the expander 4 may be made different from each other. In other words, the conventional constraint of constant density ratio on the cycle operation is eliminated (see, for example, JP 2001-116371A (FIG. 1 )). - JP 2003-121018A discloses a refrigeration cycle apparatus including a compressor and an expander that are coupled directly by a single shaft. The refrigeration cycle apparatus has an expansion valve arranged in series with the expander, and a bypass valve for bypassing the expander. A gas-liquid separator is provided between the expander and the expansion valve so that the gas refrigerant separated from the liquid refrigerant by the gas-liquid separator is introduced to an intermediate pressure portion of the compressor.
- However, a problem has been that the refrigerant flowing through the circuit that bypasses the expander does not contribute to improvements in system efficiency at all. This applies to both of the foregoing publications.
- In view of this, it is an object of the present invention to provide a refrigeration cycle apparatus provided with a compressor, a radiator, an expander, and an evaporator, connected successively in series, that can increase the refrigerant flow rate through the radiator and at the same time avoid the constraint of constant density ratio.
- Accordingly, the present invention provides refrigeration cycle apparatus including:
- a compressor for compressing a refrigerant;
- a radiator for cooling the refrigerant compressed by the compressor;
- an expander for expanding the refrigerant cooled by the radiator and recovering mechanical power from the refrigerant under expansion;
- an evaporator for heating the refrigerant expanded by the expander and supplying the refrigerant to the compressor;
- a bypass circuit including a flow rate control valve and a gas-liquid separator that is provided downstream from the flow rate control valve and that is for separating the refrigerant passed through the flow rate control valve into a gas refrigerant and a liquid refrigerant, one end of the bypass circuit being connected to an intake conduit of the expander and the other end of the bypass circuit being connected to a discharge conduit of the expander so that a portion of the refrigerant passed through the radiator bypasses the expander and is guided to the flow rate control valve and that the liquid refrigerant separated by the gas-liquid separator returns to the discharge conduit of the expander; and
- an injection circuit, one end of which being connected to a gas outlet portion of the gas-liquid separator and the other end of which being connected to an intermediate pressure portion of the compressor.
- According to the present invention as described above, by allowing a portion of the refrigerant flowing out of the radiator to flow through the bypass circuit, the constraint of constant density ratio can be avoided. Moreover, since the liquid refrigerant and the gas refrigerant are separated by the gas-liquid separator provided in the bypass circuit and the gas refrigerant is injected into the intermediate pressure portion of the compressor, the refrigerant flow rate through the radiator can be increased. The specific enthalpy of the liquid refrigerant that flows out of the gas-liquid separator and returns to the discharge conduit of the expander is smaller than the specific enthalpy of the refrigerant (gas-liquid two-phase refrigerant) that has been expanded by the expander. Therefore, the specific enthalpy of the refrigerant at the inlet of the evaporator lowers and the enthalpy difference between the inlet and the outlet of the evaporator increases, leading to an improvement in the refrigerating capacity. Furthermore, the injection circuit enables the gas refrigerant flowing out of the gas-liquid separator to be mixed with the refrigerant that is in the compression process, preventing liquid compression from occurring in the compressor and thus ensuring a high degree of reliability of the compressor.
- In another aspect, the present invention provides a refrigeration cycle apparatus including:
- a compressor for compressing a refrigerant;
- a radiator for cooling the refrigerant compressed by the compressor;
- an expander for expanding the refrigerant cooled by the radiator and recovering mechanical power from the refrigerant under expansion;
- an evaporator for heating the refrigerant expanded by the expander and supplying the refrigerant to the compressor;
- a bypass circuit including a flow rate control valve, one end of the bypass circuit being connected to an intake conduit of the expander and the other end of the bypass circuit being connected to an intermediate pressure portion of the compressor so that a portion of the refrigerant passed through the radiator bypasses the expander and is guided to the flow rate control valve;
- an intake temperature sensor for detecting the refrigerant after flowing out of the evaporator but before being taken into the compressor; and
- a controller for controlling an opening of the flow rate control valve according to a detection result detected by the intake temperature sensor.
- According to the present invention as described above, by allowing the refrigerant to flow through the bypass circuit, the refrigerant flow rate through the radiator can be increased while the constraint of constant density ratio is avoided. Therefore, the overall performance of the refrigeration cycle apparatus can be improved.
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FIG. 1 is a configuration diagram illustrating a refrigeration cycle apparatus according to a first embodiment of the present invention; -
FIG. 2 is a vertical cross-sectional view illustrating one example of a fluid machine including a compressor and an expander; -
FIG. 3 is a view illustrating one example of injection ports provided in the compressor; -
FIG. 4 is a Mollier diagram illustrating the refrigeration cycle according to the first embodiment of the present invention; -
FIG. 5 is a control flow diagram of the refrigeration cycle apparatus according to the first embodiment of the present invention; -
FIG. 6 is a configuration diagram illustrating a refrigeration cycle apparatus according to a second embodiment of the present invention; -
FIG. 7 is a configuration diagram illustrating a refrigeration cycle apparatus according to a third embodiment of the present invention; -
FIG. 8 is a configuration diagram illustrating a refrigeration cycle apparatus according to a fourth embodiment of the present invention; -
FIG. 9 is a configuration diagram illustrating a refrigeration cycle apparatus according to a fifth embodiment of the present invention; -
FIG. 10 is a Mollier diagram illustrating the refrigeration cycle according to the fifth embodiment of the present invention; -
FIG. 11 is a control flow diagram of the refrigeration cycle apparatus according to the fifth embodiment of the present invention; and -
FIG. 12 is a configuration diagram illustrating a conventional refrigeration cycle apparatus. - Hereinbelow, embodiments of the refrigeration cycle apparatus according to the present invention will be described in detail with reference to the drawings.
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FIG. 1 is a configuration diagram illustrating a refrigeration cycle apparatus according to a first embodiment of the present invention. Arefrigeration cycle apparatus 100A of the present embodiment is furnished with acompressor 101 for compressing a refrigerant such as hydrofluorocarbon or carbon dioxide, aradiator 102 for cooling the refrigerant compressed by thecompressor 101, anexpander 103 for decompressing and expanding the refrigerant cooled by theradiator 102 and recovering mechanical power from the refrigerant under expansion, anevaporator 104 for heating the refrigerant decompressed by theexpander 103, and a plurality of main pipes 116 (main conduits) for connecting thecompressor 101, theradiator 102, theexpander 103, and theevaporator 104 in that order. Thecompressor 101, theradiator 102, theexpander 103, theevaporator 104, and themain pipes 116 constitute amain circuit 117 through which the refrigerant circulates. - In the first embodiment, the
compressor 101 and theexpander 103 are coupled uniaxially to amotor 6 for driving thecompressor 101.FIG. 2 is a vertical cross-sectional view illustrating one example of fluid machine including thecompressor 101 and theexpander 103 of this kind, and according to the present embodiment, therefrigeration cycle apparatus 100A includes such afluid machine 200. As illustrated inFIG. 2 , mechanical power obtained by theexpander 103 is supplied to ashaft 7 and is utilized as auxiliary driving power for thecompressor 101, which contributes to reducing the power consumption of themotor 6. Since theexpander 103 and thecompressor 101 revolve at the same frequency at all times, the refrigeration cycle apparatus including thefluid machine 200 is constrained by the constraint of constant density ratio. - As a means to avoid the constraint of constant density ratio, the
refrigeration cycle apparatus 100A is, as illustrated inFIG. 1 , further furnished with abypass circuit 113, one end of which is connected to one of themain pipes 116 that is between theradiator 102 and theexpander 103 and the other end of which is connected to another one of themain pipes 116 that is between theexpander 103 and theevaporator 104, so that a portion of the refrigerant that has passed through theradiator 102 bypasses theexpander 103. The former of themain pipes 116 is an intake conduit of theexpander 103 and is also a discharge conduit of theradiator 102. The latter of themain pipes 116 is a discharge conduit of theexpander 103 and is also an intake conduit of theevaporator 104. - The
bypass circuit 113 includes a first flowrate control valve 105, a gas-liquid separator 110 provided downstream from the first flowrate control valve 105, and a plurality ofbypass pipes 115. By allowing a portion of the refrigerant that has passed through theradiator 102 to flow through thebypass circuit 113, the ratio between the density of the refrigerant at the inlet of thecompressor 101 and the density of the refrigerant at the inlet of theexpander 103 can be varied. - The refrigerant that bypasses the
expander 103 is introduced to the first flowrate control valve 105. The gas-liquid separator 110 has the function of separating the refrigerant that has passed through the first flowrate control valve 105 into a gas refrigerant and a liquid refrigerant, and it has a liquid outlet portion and a gas outlet portion. Abypass pipe 115 is connected to the liquid outlet portion so that the gas-liquid two-phase refrigerant that has changed from the liquid refrigerant into the gas-liquid two-phase refrigerant can be returned to one of themain pipes 116 that is between theexpander 103 and theevaporator 104. - The
refrigeration cycle apparatus 100A further includes aninjection circuit 109, one end of which is connected to the gas outlet portion of the gas-liquid separator 110 and the other end of which is connected to an intermediate pressure portion of the compressor 101 (an intermediate pressure portion of the main circuit 117). Theinjection circuit 109 includes a second flowrate control valve 108 and a plurality ofinjection pipes 119. A portion or all of the gas refrigerant that has been separated from the liquid refrigerant by the gas-liquid separator 110 is injected into the intermediate pressure portion of thecompressor 101 through theinjection circuit 109. - As illustrated in
FIG. 2 , the intermediate pressure portion of thecompressor 101 can be a portion of the interior of thecompressor 101 that faces the refrigerant flow channel, that is, a portion thereof that faces acompression chamber 28. Thecompressor 101 is a scroll-type compressor in which thecompression chamber 28 is formed between astationary scroll 21 and anorbiting scroll 22, and aninjection port 120 provided in thestationary scroll 21 serves as the intermediate pressure portion. One of theinjection pipes 119 is connected to theinjection port 120. Theinjection port 120 is located between anintake port 21 a and anoutlet port 21 b in the refrigerant flow channel within thecompressor 101. The gas refrigerant that has flowed out of the gas outlet portion of the gas-liquid separator 110 passes through theinjection circuit 109, is injected into thecompression chamber 28 through theinjection port 120, and is mixed with the refrigerant that is being compressed. - An
injection port 120 may be provided at one location in thestationary scroll 21, or, as illustrated inFIG. 3 , a plurality ofinjection ports stationary scroll 21. The type of the compressor is not limited to the scroll type, and may be other types of positive displacement compressors such as a rotary type compressor. Likewise, the type of the expander is not limited either, althoughFIG. 2 shows a two-stage rotary compressor as theexpander 103. - It should be noted that in the present specification the term “intermediate pressure” is intended to mean a pressure that is between a high pressure and a low pressure in the refrigeration cycle, in other words, a pressure between the pressure of the refrigerant flowing into the
radiator 102 and the pressure of the refrigerant flowing out of theevaporator 104. - Referring back to
FIG. 1 , the description will proceed further. Thebypass circuit 113 further may include athrottling device 114 provided downstream from the gas-liquid separator 110. Thethrottling device 114 may be a common expansion valve. Such athrottling device 114 is capable of changing the liquid refrigerant flowing out of the gas-liquid separator 110 into a gas-liquid two-phase refrigerant. This allows the gas-liquid two-phase refrigerant to be returned to themain pipe 116 that is between theexpander 103 and theevaporator 104, which is advantageous in maintaining a desired operating condition. However, if the amount of the liquid refrigerant is small, it is possible to send the liquid refrigerant to themain pipe 116 without expanding it by thethrottling device 114. It should be noted that the first flowrate control valve 105, the second flowrate control valve 108, and thethrottling device 114 have a common function, so the same kind of expansion valves may be used for them. - In addition, it is recommended that two
temperature sensors main circuit 117. One of thetemperature sensors 111 is an intake temperature sensor that detects the temperature of the refrigerant after flowing out of theevaporator 104 but before being taken into thecompressor 101, and it detects what is called a superheat temperature. The other one of thetemperature sensors 112 is an outlet temperature sensor that detects the temperature of the refrigerant after being discharged from thecompressor 101 but before flowing into theradiator 102. Furthermore, acontroller 107 is provided, which controls the openings of the first flowrate control valve 105 and thethrottling device 114 of thebypass circuit 113 as well as the opening of the second flowrate control valve 108 of theinjection circuit 109. Signals that can identify the temperatures of the refrigerant are input from the twotemperature sensors controller 107. Thecontroller 107 controls the openings of the first flowrate control valve 105, thethrottling device 114, and the second flowrate control valve 108 according to the signals from thetemperature sensors refrigeration cycle apparatus 100A. - The operations and effects of the
refrigeration cycle apparatus 100A will be described with reference to the Mollier diagram ofFIG. 4 . - In the Mollier diagram of
FIG. 4 , the change of the refrigerant circulating in themain circuit 117 is represented as A→B→C→D→E→F→A. The refrigerant flowing through thebypass circuit 113 is branched at point E, which corresponds to the portion of themain circuit 117 that is between theradiator 102 and theexpander 103, is then decompressed to point G by the first flowrate control valve 105, and is thereafter separated into a gas refrigerant and a liquid refrigerant by the gas-liquid separator 110. The liquid refrigerant, which is in the state of point H on the saturated liquid curve, is decompressed to point I by thethrottling device 114, and is then merged with the refrigerant being at point F, which is discharged from theexpander 103. Accordingly, the specific enthalpy of the refrigerant that has been discharged from theexpander 103 and merged with the liquid refrigerant from thebypass circuit 113 is represented by point J. On the other hand, the gas refrigerant separated from the liquid refrigerant by the gas-liquid separator 110 flows into thecompressor 101 and merges with the refrigerant at point B, which is the refrigerant under compression. The specific enthalpy of the refrigerant that has undergone the merge with the refrigerant being compressed by thecompressor 101 and the gas refrigerant injected from theinjection circuit 109 is represented by point C. - The refrigerant flow rate flowing through the
radiator 102 is the sum of the refrigerant flow rate Ge flowing through theevaporator 104 and the refrigerant flow rate Gi flowing through thebypass circuit 106, and thus is represented as (Ge+Gi); therefore, the amount of heat exchanged by the radiator increases. In this way, it is possible to improve the performance of therefrigeration cycle apparatus 100A while avoiding the constraint of constant density ratio. - When the refrigerant flow rate flowing through the
bypass circuit 113 is increased, the refrigeration cycle will be balanced so that the intake density of thecompressor 101 increases. Accordingly, when the intake superheat of thecompressor 101 needs to be reduced, the opening of the first flowrate control valve 105 provided in thebypass circuit 113 should be increased. - In addition, by increasing the opening of the second flow
rate control valve 108 provided in theinjection circuit 109 so as to increase the refrigerant flow rate flowing through theinjection circuit 109, the specific enthalpy at point C becomes smaller, and thereby, the refrigerant discharge temperature (point D) of thecompressor 101 can be controlled to be lower. - Thus, when the refrigerant flow rate flowing through the
injection circuit 109 is increased, the refrigeration cycle will be balanced so that the refrigerant discharge temperature of thecompressor 101 decreases. Conversely, when it is desired to elevate the refrigerant discharge temperature of thecompressor 101, the opening of the second flowrate control valve 108 provided in theinjection circuit 109 should be decreased. - The control procedure for the first flow
rate control valve 105 and the second flowrate control valve 108 executed by thecontroller 107 will be described with reference to the flowchart ofFIG. 5 . Upon starting the operation, it is assessed atstep 301 whether or not the difference between an actual superheat temperature T1 detected by theintake temperature sensor 111 and a target superheat TH1 falls within the tolerance range ±t1 (dead zone). The tolerance t1 may be set to be about 5% of the target superheat TH1. - If it is assessed that the difference (absolute value) between the actual superheat temperature T1 and the target superheat TH1 is greater than the tolerance t1, the process proceeds to step 302, in which it is assessed whether or not the actual superheat temperature T1 is greater than the target superheat TH1. If the actual superheat temperature T1 is greater than the target superheat TH1, the process proceeds to step 303, in which a control process for increasing the opening of the first flow
rate control valve 105 is executed. When the opening of the first flowrate control valve 105 is increased, the refrigerant flow rate flowing through thebypass circuit 113 increases; therefore, the refrigeration cycle will be balanced so that the superheat temperature T1 decreases. - On the other hand, if it is assessed at step 302 that the actual superheat temperature T1 is lower than the target superheat TH1, the process proceeds to step 304, in which a control process for decreasing the opening of the first flow
rate control valve 105 is executed. Thereby, the refrigeration cycle will be balanced so that the superheat temperature T1 rises, and therefore, the superheat temperature can be controlled so as to approach the target value. - Next, it is assessed at
step 305 whether or not the difference between an actual refrigerant discharge temperature T2 detected by theoutlet temperature sensor 112 and a target refrigerant discharge temperature TH2 falls within the tolerance range ±t2 (dead zone). The tolerance t2 may be set to be about 5% of the target refrigerant discharge temperature, for example. If it is assessed that the difference between the actual refrigerant discharge temperature T2 and the target refrigerant discharge temperature TH2 falls within the tolerance range ±t2, the control process is terminated. - On the other hand, if it is assessed at
step 305 that the difference between the actual refrigerant discharge temperature T2 and the target refrigerant discharge temperature TH2 (absolute value) is greater than the tolerance t2, the process proceeds to step 306, in which it is assessed whether or not the actual refrigerant discharge temperature T2 is greater than the target refrigerant discharge temperature TH2. If the actual refrigerant discharge temperature T2 is greater than the target refrigerant discharge temperature TH2, the process proceeds to step 307, in which a control process for increasing the opening of the second flowrate control valve 108 is executed. Increasing the opening of the second flowrate control valve 108 results in a greater refrigerant flow rate flowing through theinjection circuit 109, and therefore, the refrigeration cycle will be balanced so that the refrigerant discharge temperature T2 decreases. Referring to the Mollier diagram ofFIG. 4 , the specific enthalpy at point C becomes smaller, and the refrigerant discharge temperature T2 of the compressor 101 (temperature at point D) decreases. - If it is assessed at
step 306 that the actual refrigerant discharge temperature T2 is lower than the target refrigerant discharge temperature TH2, the process proceeds to step 308, in which a control process for decreasing the opening of the second flowrate control valve 108 is executed. Thereby, the refrigeration cycle will be balanced so that the refrigerant discharge temperature T2 rises, and therefore, the refrigerant discharge temperature can be controlled so as to approach the target value. According to the Mollier diagram ofFIG. 4 , the specific enthalpy at point C increases, and the refrigerant discharge temperature T2 of the compressor 101 (temperature at point D) rises. If the opening of the second flowrate control valve 108 is changed, the process returns to step 301. By executing the control process depicted in the flowchart ofFIG. 5 repeatedly, in other words, by executing the control process periodically as needed, the superheat temperature and the refrigerant discharge temperature always can be kept at optimal values. - As has been described above, adjusting the openings of the first flow
rate control valve 105 and the second flowrate control valve 108 to control the superheat temperature and the refrigerant discharge temperature enables the system performance to be kept optimally high while avoiding the constraint of constant density ratio. - The foregoing has described an embodiment in which the openings of the first and second flow
rate control valves compressor 101. The openings of the first and second flowrate control valves compressor 101, the high pressure of the refrigeration cycle, the evaporator temperature, and the frequency of thecompressor 101, in addition to the combination of the superheat temperature and the refrigerant discharge temperature of thecompressor 101. - The first embodiment has described the case in which the
injection circuit 109 is connected directly to thecompressor 101. By contrast, the refrigeration cycle apparatus according to the second embodiment differs from the first embodiment in that it has a plurality of compressors. It should be noted, however, that the advantageous effects achieved by the bypass circuit and the injection circuit are common between the second embodiment and the first embodiment. - As illustrated in
FIG. 6 , arefrigeration cycle apparatus 100B of the second embodiment is furnished with a low-pressure-side compressor 101A, and a high-pressure-side compressor 101B connected in series with the low-pressure-side compressor 101A via one of themain pipes 116. Specifically, a multi-stage compressor including the low-pressure-side compressor 101A and the high-pressure-side compressor 101B is employed as the compressor for compressing a refrigerant. In this case, the intermediate pressure portion of thecompressors injection circuit 109 is connected, may be themain pipe 116 that is a joint portion for joining the low-pressure-side compressor 101A and the high-pressure-side compressor 101B. According to the present embodiment, theinjection circuit 109 and thecompressors injection pipe 119 and themain pipe 116, so the designing and assembling of the apparatus are made easy. Of course, a connecting component such as a joint may be provided between theinjection pipe 119 and themain pipe 116. - The compressor that is coupled uniaxially to the
expander 103 may be either the low-pressure-side compressor 101A or the high-pressure-side compressor 101B. The type of each of thecompressors expander 103 may be a centrifugal compressor. -
FIG. 7 illustrates a configuration diagram of a refrigeration cycle apparatus according to a third embodiment. Arefrigeration cycle apparatus 100C shown inFIG. 7 differs from that of the first embodiment in that aninjection circuit 109′ further includes aninjector 123 provided downstream from the second flowrate control valve 108. In other respects, the present embodiment is similar to the first embodiment, and in the drawings, the same reference numerals designate the same components. - The
injector 123 in theinjection circuit 109′ is capable of switching between an open state that permits passage of the refrigerant (gas refrigerant) and a closed state that inhibits passage of the refrigerant, and it may be, for example, a solenoid valve controlled by thecontroller 107. Thus, the present embodiment makes it possible to control even the timing of injecting the gas refrigerant into the intermediate pressure portion of thecompressor 101. For example, by controlling the open/close operations of theinjector 123 so as to synchronize the rotation of thecompressor 101, the gas refrigerant can be injected into thecompression chamber 28 inside thecompressor 101 with more appropriate timing. It should be noted that the second flowrate control valve 108 may be omitted and only theinjector 123 of this kind may be provided. Theinjector 123 may be disposed inside the shell of thecompressor 101. -
FIG. 8 illustrates a configuration diagram of a refrigeration cycle apparatus according to a fourth embodiment. Arefrigeration cycle apparatus 100D shown inFIG. 8 additionally has a liquidrefrigerant return circuit 125 for enabling theexpander 103 to take in the liquid refrigerant that has been separated from the gas refrigerant by the gas-liquid separator 110, in addition to the elements of the refrigeration cycle apparatus of the first embodiment. - The liquid
refrigerant return circuit 125 may be constituted by a similar pipe such as that used for themain pipes 116 and thebypass pipes 115. One end of the liquidrefrigerant return circuit 125 is connected to a portion of thebypass circuit 113 that is between the liquid outlet portion of the gas-liquid separator 110 and thethrottling device 114. The other end of the liquidrefrigerant return circuit 125 is connected to the intake conduit of the expander 103 (corresponding to a portion of the main pipes 116) downstream from the branching location to thebypass circuit 113. One end of the liquidrefrigerant return circuit 125 may be connected to the liquid outlet portion of the gas-liquid separator 110, and the other end thereof may be connected to the inlet (or a neighboring part of the inlet) of theexpander 103. - By restricting the opening of the
throttling device 114, a portion of the liquid refrigerant separated from the gas refrigerant by the gas-liquid separator 110 can be supplied to the liquidrefrigerant return circuit 125. After circulating through the liquidrefrigerant return circuit 125, the liquid refrigerant is taken into theexpander 103. Thus, the refrigerant flow rate through theexpander 103 can be increased, and therefore, the amount of power recovery can be increased and further improvement in the efficiency can be expected. Of course, the constraint of constant density ratio can be avoided because of the working of theinjection circuit 109. - In addition, it is possible to supply the whole amount of the liquid refrigerant that has been separated from the gas refrigerant by the gas-
liquid separator 110 to the liquidrefrigerant return circuit 125 by fully closing thethrottling device 114. Under certain circumstances, thethrottling device 114 and thebypass pipe 115 downstream from thethrottling device 114 may be omitted. Furthermore, the liquidrefrigerant return circuit 125 may include a flow rate control valve (not shown). -
FIG. 9 illustrates a configuration diagram of a refrigeration cycle apparatus according to a fifth embodiment. Arefrigeration cycle apparatus 100E is furnished with amain circuit 117 and abypass circuit 106. The configuration of themain circuit 117 is the same as that of the other embodiments, but the configuration of thebypass circuit 106 is different from that of the other embodiments. - As illustrated in
FIG. 9 , thebypass circuit 106 connects the intake conduit of theexpander 103 and the intermediate pressure portion of thecompressor 101 via the first flowrate control valve 105, and it is the circuit for introducing a portion of the refrigerant that has passed through theradiator 102 to the intermediate pressure portion of thecompressor 101. As has been explained previously, the injection port(s) 120 (seeFIG. 2 ) of thecompressor 101 may be used as the intermediate pressure portion of thecompressor 101. - As illustrated in the Mollier diagram of
FIG. 10 , the change of the refrigerant circulating in themain circuit 117 is represented as A→B→C→D→E→F→A. The refrigerant flowing through thebypass circuit 106 is branched at point E, which corresponds to the portion of themain circuit 117 that is between theradiator 102 and theexpander 103, is then decompressed to point G by the first flowrate control valve 105, and thereafter is introduced into the intermediate pressure portion of thecompressor 101, which is represented as point C. The refrigerant flow rate flowing through theradiator 102 is the sum of the refrigerant flow rate Ge flowing through theevaporator 104 and the refrigerant flow rate Gi flowing through thebypass circuit 106, and thus is represented as (Ge+Gi); therefore, the amount of heat exchanged by the radiator increases. In this way, it is possible to improve the performance of therefrigeration cycle apparatus 100E while avoiding the constraint of constant density ratio. - Here, the following equations (1) and (2) hold, wherein: the volume flow rate of the refrigerant that passes through the
compressor 101 is represented as VC; the refrigerant density at the inlet of thecompressor 101 is DC; the volume flow rate of the refrigerant that passes through theexpander 103 is VE; the refrigerant density at the inlet of theexpander 103 is DE; and the mass flow rate ratio of the refrigerant that flows through thebypass circuit 113 with respect to the total refrigerant is h, whereby the mass flow rate ratio of the refrigerant that flows through theexpander 103 can be expressed as (1−h). It should be noted that the mass flow rate ratio of thecompressor 101 is approximated as “1.”
VC×DC:VE×DE=1:(1−h) (1)
VE×DE=(1−h)×VC×DC (2) - According to these relationships, when the refrigerant flow rate flowing through the
bypass circuit 106 is increased, the refrigeration cycle will be balanced so that the refrigerant density DC at the inlet of thecompressor 101 increases. Accordingly, when the intake superheat of thecompressor 101 is desired to be reduced, the opening of the first flowrate control valve 105 provided in thebypass circuit 106 should be increased. - The control procedure for the first flow
rate control valve 105 executed by thecontroller 107 will be described with reference to the flowchart ofFIG. 11 . Upon starting the operation, it is assessed at step 201 whether or not the difference between an actual superheat temperature T1 detected by theintake temperature sensor 111 and a target superheat TH1 falls within the tolerance range ±t1 (dead zone). The tolerance ti may be set to be about 5% of the target superheat TH1. If it is assessed that the difference between the actual superheat temperature T1 and the target superheat TH1 falls within the tolerance range ±t1, the control process is terminated. - On the other hand, if it is assessed that the difference between the actual superheat temperature T1 and the target superheat TH1 (absolute value) is greater than the tolerance t1, the process proceeds to step 202, in which it is assessed whether or not the actual superheat temperature T1 is greater than the target superheat TH1. If the actual superheat temperature T1 is greater than the target superheat TH1, the process proceeds to step 203, in which a control process for increasing the opening of the first flow
rate control valve 105 is executed. Increasing the opening of the first flowrate control valve 105 results in a greater refrigerant flow rate flowing through thebypass circuit 106, and therefore, the refrigeration cycle will be balanced so that the superheat temperature T1 decreases. If it is assessed at step 202 that the actual superheat temperature T1 is lower than the target superheat TH1, the process proceeds to step 204, in which a control process for decreasing the opening of the first flowrate control valve 105 is executed. Thereby, the refrigeration cycle will be balanced so that the superheat temperature T1 increases, and therefore the superheat temperature can be controlled to be closer to the target value. - Thus, by adjusting the opening of the first flow
rate control valve 105 so as to control the superheat temperature optimally, system performance can be kept high while avoiding the constraint of constant density ratio. - The foregoing has described an embodiment in which the first flow
rate control valve 105 is controlled to optimize the superheat temperature. It is also possible to control the opening of the first flowrate control valve 105 in order to optimize the refrigerant discharge temperature of thecompressor 101, using theoutlet temperature sensor 112 of the compressor 101 (seeFIG. 1 ). In addition, thebypass circuit 106 may include an injector 123 (seeFIG. 7 ) as described in the third embodiment. - The foregoing several embodiments have described examples of refrigeration cycle apparatus furnished with a fluid machine in which a compressor and an expander are coupled, but it should be understood that the present invention is also applicable to separate-type systems in which the compressor and the expander are not coupled physically to each other. In the separate-type system, power consumption of the motor for driving the compressor can be reduced by converting the mechanical power that is recovered by the expander into electric power by a generator, and regenerating the electric power to a power supply line. In such a system, the frequencies of the compressor and the expander may be changed individually and freely, so the system is essentially free from the constraint of constant density ratio.
- However, because the efficiencies of the motor and the generator change depending of their frequencies, the efficiency of the system may degrade significantly if the efficiencies of the motor and the generator are ignored. For this reason, for the separate-type system as well, it may be advantageous to provide and utilize the bypass circuit and the injection circuit as described in the present specification, and this makes it possible to avoid the constraint of constant density ratio while maintaining highly efficient workings of the motor and the generator, leading to further enhancement in the system efficiency.
- The refrigeration cycle apparatus according to the present invention can be used for not only hot water heaters and air-conditioners but also for other various electric appliances such as dish dryers and garbage dryers.
Claims (9)
Applications Claiming Priority (2)
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JP2005364587A JP2009052752A (en) | 2005-12-19 | 2005-12-19 | Refrigeration cycle device |
JP2005-364587 | 2005-12-19 |
Publications (1)
Publication Number | Publication Date |
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US20070151266A1 true US20070151266A1 (en) | 2007-07-05 |
Family
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US11/612,958 Abandoned US20070151266A1 (en) | 2005-12-19 | 2006-12-19 | Refrigeration cycle apparatus |
Country Status (3)
Country | Link |
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US (1) | US20070151266A1 (en) |
JP (1) | JP2009052752A (en) |
WO (1) | WO2007072760A1 (en) |
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US20090031738A1 (en) * | 2005-05-06 | 2009-02-05 | Tomoichiro Tamura | Refrigerating machine |
US20090158764A1 (en) * | 2007-12-24 | 2009-06-25 | Lg Electronics Inc. | Air conditioning system |
US20100011787A1 (en) * | 2007-03-09 | 2010-01-21 | Alexander Lifson | Prevention of refrigerant solidification |
US20100089092A1 (en) * | 2007-05-16 | 2010-04-15 | Panasonic Corporation | Refrigeration cycle apparatus and fluid machine used therefor |
US20100131115A1 (en) * | 2006-11-13 | 2010-05-27 | Bum Suk Kim | Controlling method of air conditioner |
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US20130239602A1 (en) * | 2011-01-31 | 2013-09-19 | Mitsubishi Electric Corporation | Air-conditioning apparatus |
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