EP2565556A1 - Dispositif à cycle de réfrigération - Google Patents

Dispositif à cycle de réfrigération Download PDF

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Publication number
EP2565556A1
EP2565556A1 EP11774593A EP11774593A EP2565556A1 EP 2565556 A1 EP2565556 A1 EP 2565556A1 EP 11774593 A EP11774593 A EP 11774593A EP 11774593 A EP11774593 A EP 11774593A EP 2565556 A1 EP2565556 A1 EP 2565556A1
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EP
European Patent Office
Prior art keywords
stage compressor
pressure
expander
pressure stage
low
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP11774593A
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German (de)
English (en)
Inventor
Atsuo Okaichi
Takeshi Ogata
Masanobu Wada
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Panasonic Intellectual Property Management Co Ltd
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Panasonic Corp
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Publication date
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Publication of EP2565556A1 publication Critical patent/EP2565556A1/fr
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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
    • 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
    • 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
    • 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
    • F25B2400/0401—Refrigeration circuit bypassing means for the compressor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/13—Economisers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/14—Power generation using energy from the expansion of the refrigerant
    • 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
    • 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
    • F25B2600/2519—On-off valves

Definitions

  • the present invention relates to a refrigeration cycle apparatus.
  • a refrigeration cycle apparatus 700 shown in Fig. 15 is conventionally known as a refrigeration cycle apparatus provided with an expander that recovers power by expanding a refrigerant, and a second compressor that preliminarily increases the pressure of the refrigerant (for example, see JP 2003-307358 A ). With reference to Fig. 15 , the configuration of the conventional refrigeration cycle apparatus 700 is described.
  • the refrigeration cycle apparatus 700 is provided with a refrigerant circuit 6 formed of a first compressor 1, a heat radiator 2, an expander 3, an evaporator 4, a second compressor 5, and flow passages 10a to 10e connecting these components in this order.
  • the second compressor 5 is coupled to the expander 3 by a power-recovery shaft 7, and is driven by receiving, via the power-recovery shaft 7, mechanical energy recovered in the expander 3.
  • bypass passage 8 that bypasses the second compressor 5 and a bypass valve 9 that controls the flow of the refrigerant in the bypass passage 8 are provided therein.
  • the upstream end of the bypass passage 8 is connected to the flow passage 10d that connects the outlet of the evaporator 4 and the suction port of the second compressor 5.
  • the downstream end of the bypass passage 8 is connected to the flow passage 10e that connects the discharge port of the second compressor 5 and the suction port of the first compressor 1.
  • the refrigeration cycle apparatus 700 is activated according to the following procedures. First, the operation of the first compressor 1 is started, and the bypass valve 9 is opened. These allow the refrigerant in the evaporator 4 to be drawn into the first compressor 1 through the bypass passage 8 as shown by solid arrows in Fig. 15 . The pressure of the refrigerant is increased in the first compressor 1 and the refrigerant is discharged therefrom, thereby causing an increase in the pressure at the suction port of the expander 3. As a result of this, a pressure difference is produced between before and after the expander 3, as shown in Fig. 16 , so that the expander 3 and the second compressor 5 can be activated rapidly. After the expander 3 and the second compressor 5 are activated, the bypass valve 9 is closed.
  • the refrigerant that has flowed out of the evaporator 4 is drawn into the second compressor 5 through the flow passage 10d as shown by dashed arrows in Fig. 15 . In this way, smooth transfer to regular operation can be achieved by providing the bypass passage 8.
  • Patent Literature 1 JP 2003-307358 A
  • the second compressor 5 is a load during the activation of the expander 3. That is, friction, etc., between the power-recovery shaft 7 and the components of the second compressor 5 cause a driving resistance to the expander 3.
  • the second compressor 5 and the expander 3 form the refrigerant circuit 6 of a single channel, and their rotational speeds are identical because they are coupled to each other by the power-recovery shaft 7 that is commonly shared. Accordingly, the volume of the second compressor 5 and the volume of the expander 3 need to be set so that the mass of the refrigerant to be drawn by the second compressor 5 per unit time should be equal to the mass of the refrigerant to be drawn by the expander 3 per unit time.
  • Fig. 17 is an example of the Mollier diagram when carbon dioxide is used as the refrigerant in the conventional refrigeration cycle apparatus 700.
  • the refrigerant drawn by the second compressor 5 has a pressure of 40 kg/cm 2 , and a temperature of about 10°C (point A in Fig. 17 ), and the refrigerant has a density of 108.0 kg/m 3 .
  • the refrigerant drawn by the expander 3 has a pressure of 100 kg/cm 2 , and a temperature of 40°C (point C in Fig. 17 ), and the refrigerant has a density of 628.61 kg/m 3 at this time point.
  • the suction volume (m 3 ) of the second compressor 5 is referred to as Vc
  • the suction volume (m 3 ) of the expander 3 is referred to as Ve
  • the rotational speed (S -1 ) of the power-recovery shaft 7 per second is referred to as N.
  • the mass (kg/s) of the refrigerant that the second compressor 5 can draw per second and the mass (kg/s) of the refrigerant that the expander 3 can draw per second can be expressed respectively by Formula 1 and Formula 2.
  • the mass of the refrigerant that the second compressor 5 can draw per second 108.0 ⁇ Vc ⁇ N
  • the mass of the refrigerant that the expander 3 can draw per second 628.61 ⁇ Ve ⁇ N
  • the suction volume Vc of the second compressor 5 can be expressed by Formula 3 from the above-mentioned Formula 1 and Formula 2.
  • Vc 628.61 / 108.0 ⁇ Ve ⁇ 5.8 ⁇ Ve
  • the expander 3 is required to drive the second compressor 5 having a suction volume that is about 5.8 times that of the expander 3.
  • the larger the ratio between the density of the refrigerant to be drawn by the second compressor 5 and the density of the refrigerant to be drawn by the expander 3 the larger the ratio between the suction volume of the second compressor 5 and the suction volume of the expander 3 also should be.
  • the suction volume of the expander 3 becomes smaller with respect to the suction volume of the second compressor 5, and the driving resistance to the expander 3 in the activation of the second compressor 5 becomes relatively larger.
  • the present invention aims to solve the above-mentioned problems, and it is an object of the present invention to provide a refrigeration cycle apparatus that can be activated surely and stably.
  • the present invention provides a refrigeration cycle apparatus including: a main refrigerant circuit having a low-pressure stage compressor that compresses a refrigerant, a high-pressure stage compressor that further compresses the refrigerant that has been compressed in the low-pressure stage compressor, a heat radiator that cools the refrigerant that has been compressed in the high-pressure stage compressor, an expander that recovers power from the refrigerant that has been cooled in the heat radiator while expanding the refrigerant, the expander being coupled to the low-pressure stage compressor by a shaft so that the recovered power is transferred to the low-pressure stage compressor, a gas-liquid separator that separates the refrigerant that has been expanded in the expander into a gas refrigerant and a liquid refrigerant, and an evaporator that evaporates the liquid refrigerant that has been separated in the gas-liquid separator; an injection flow passage that introduces the gas refrigerant that has been separated in the gas-liquid separator into a portion of the main refrig
  • the present invention provides a refrigeration cycle apparatus including: a main refrigerant circuit having a low-pressure stage compressor that compresses a refrigerant, a high-pressure stage compressor that further compresses the refrigerant that has been compressed in the low-pressure stage compressor, a heat radiator that cools the refrigerant that has been compressed in the high-pressure stage compressor, an expander that recovers power from the refrigerant that has been cooled in the heat radiator while expanding the refrigerant, the expander being coupled to the low-pressure stage compressor by a shaft so that the recovered power is transferred to the low-pressure stage compressor, a gas-liquid separator that separates the refrigerant that has been expanded in the expander into a gas refrigerant and a liquid refrigerant, an evaporator that evaporates the liquid refrigerant that has been separated in the gas-liquid separator, and an expansion valve provided on the flow passage between the gas-liquid separator and the evaporator; an injection flow passage that introduces the gas ref
  • the high-pressure stage compressor can draw the refrigerant in the evaporator and the gas-liquid separator through the injection flow passage. This allows the pressure on the high-pressure side of the main refrigerant circuit to increase rapidly.
  • the pressure at the discharge port of the expander can be made equal to the pressure at the suction port of the high-pressure stage compressor.
  • the pressure at the suction port of the expander is normally equal to the pressure on the high-pressure side of the main refrigerant circuit.
  • the pressure at the suction port of the low-pressure stage compressor can be made equal to the pressure on the high-pressure side of the main refrigerant circuit due to the functions of the flow passage-switching mechanism and the high-pressure supply passage.
  • the pressure at the discharge port of the low-pressure stage compressor is normally equal to the pressure at the suction port of the high-pressure stage compressor.
  • a pressure difference can be produced not only before and after the expander but also before and after the low-pressure stage compressor. Therefore, the refrigeration cycle apparatus of the present invention can be activated surely and stably, independent of operational conditions.
  • the high-pressure stage compressor can draw the refrigerant in the gas-liquid separator through the injection flow passage. This allows the pressure on the high-pressure side of the main refrigerant circuit to increase rapidly.
  • the pressure at the discharge port of the expander can be made equal to the pressure at the suction port of the high-pressure stage compressor.
  • the pressure at the suction port of the expander is normally equal to the pressure on the high-pressure side of the main refrigerant circuit.
  • the flow passages before and after the expansion valve can be separated from each other by fully closing the expansion valve. Accordingly, the pressure at the suction port of the low-pressure stage compressor can be prevented from being equal to the pressure at the discharge port of the low-pressure stage compressor via the injection flow passage. As a result, the pressure at the suction port of the low-pressure stage compressor can be maintained at the pressure of the main refrigerant circuit before the high-pressure stage compressor is driven (intermediate pressure). The pressure at the discharge port of the low-pressure stage compressor is normally equal to the pressure at the suction port of the high-pressure stage compressor.
  • a pressure difference can be produced not only before and after the expander but also before and after the low-pressure stage compressor. Therefore, the refrigeration cycle apparatus of the present invention can be activated surely and stably, independent of operational conditions.
  • Fig. 1 is a configuration diagram showing a refrigeration cycle apparatus 100 in Embodiment 1 of the present invention.
  • the refrigeration cycle apparatus 100 is provided with a refrigerant circuit 106 formed by sequentially connecting a high-pressure stage compressor 101, a heat radiator 102, an expander 103, a gas-liquid separator 108, an evaporator 104, and a low-pressure stage compressor 105, with flow passages 106a to 106f.
  • the flow passages 106a to 106f each are constituted by a refrigerant pipe.
  • An expansion valve 110 is provided on the flow passage 106d between the gas-liquid separator 108 and the evaporator 104.
  • a check valve 132 is provided on the flow passage 106e between the evaporator 104 and the low-pressure stage compressor 105.
  • the flow passage 106f connecting the discharge port of the low-pressure stage compressor 105 and the suction port of the high-pressure stage compressor 101 may be referred to also as the "intermediate-pressure flow passage 106f".
  • the high-pressure stage compressor 101 is constituted by a compression mechanism 101a and a motor 101b for driving the compression mechanism 101a.
  • the high-pressure stage compressor 101 compresses the refrigerant to high temperature and high pressure.
  • a positive displacement compressor such as a scroll compressor and a rotary compressor can be used as the high-pressure stage compressor 101.
  • the discharge port of the high-pressure stage compressor 101 is connected to the inlet of the heat radiator 102 via the flow passage 106a.
  • the heat radiator 102 radiates heat (cools) of the refrigerant at high temperature and high pressure that has been compressed by the high-pressure stage compressor 101 through heat exchange with an external heat source.
  • the outlet of the heat radiator 102 is connected to the suction port of the expander 103 via the flow passage 106b.
  • the expander 103 expands the refrigerant at intermediate temperature and high pressure that has flowed out of the heat radiator 102 and converts the expansion energy (power) of the refrigerant into mechanical energy to recover it.
  • the discharge port of the expander 103 is connected to the inlet of the gas-liquid separator 108 via the flow passage 106c.
  • a positive displacement expander such as a scroll expander and a rotary expander can be used as the expander 103.
  • a fluid pressure motor expander can be also used as the expander 103.
  • the fluid pressure motor expander is a positive displacement fluid machine that recovers power from a refrigerant by sequentially performing processes of drawing the refrigerant and discharging the drawn refrigerant without performing any substantial expansion process in a working chamber.
  • the detailed structure and the operational principle of the fluid pressure motor expander are disclosed, for example, in WO 2008/050654 A .
  • the gas-liquid separator 108 serves to separate the refrigerant at low temperature and low pressure that has been expanded in the expander 103 into a gas refrigerant and a liquid refrigerant.
  • the gas-liquid separator 108 can prevent the liquid refrigerant from being drawn into the high-pressure stage compressor 101 in a large amount in the activation of the refrigeration cycle apparatus 100.
  • the gas refrigerant outlet of the gas-liquid separator 108 is connected to the flow passage 106f via an injection flow passage 111.
  • the liquid-refrigerant outlet of the gas-liquid separator 108 is connected to the inlet of the evaporator 104 via the flow passage 106d provided with the expansion valve 110.
  • the expansion valve 110 serves to regulate the flow rate of the liquid refrigerant to flow into the evaporator 104 in the regular operation. Accordingly, a valve, which allows the degree of opening to be varied stepwise, capable of expanding a refrigerant, typically, an electric expansion valve is preferably used as the expansion valve 110. In the activation of the refrigeration cycle apparatus 100, the expansion valve 110 is fully opened or substantially fully opened. This allows the refrigerant in the evaporator 104 to be drawn by the high-pressure stage compressor 101 smoothly.
  • the evaporator 104 evaporates the liquid refrigerant at low temperature and low pressure that has been separated in the gas-liquid separator 108 through heat exchange with an external heat source.
  • the outlet of the evaporator 104 is connected to the suction port of the low-pressure stage compressor 105 via the flow passage 106e provided with the check valve 132.
  • the low-pressure stage compressor 105 draws the refrigerant at intermediate temperature and low pressure that has flowed out of the evaporator 104, and discharges it into the intermediate-pressure flow passage 106f after preliminarily increasing the pressure thereof.
  • the discharge port of the low-pressure stage compressor 105 is connected to the suction port of the high-pressure stage compressor 101 via the intermediate-pressure flow passage 106f.
  • a positive displacement compressor such as a scroll compressor and a rotary compressor can be used as the low-pressure stage compressor 105.
  • a fluid pressure motor compressor can be used as the low-pressure stage compressor 105.
  • the fluid pressure motor compressor is a positive displacement fluid machine that increases the pressure of a refrigerant by substantially sequentially performing processes of drawing the refrigerant from the evaporator 104 and discharging the refrigerant to the high-pressure stage compressor 101.
  • the fluid pressure motor compressor is a fluid machine that allows substantially no change in the volume of the refrigerant in a working chamber.
  • the fluid pressure motor compressor basically has the same structure as the fluid pressure motor expander, the detail of which is disclosed in the above-mentioned literature.
  • the expander 103 is coupled to the low-pressure stage compressor 105 by a power-recovery shaft 107.
  • the mechanical energy (power) recovered in the expander 103 can be transferred to the low-pressure stage compressor 105 via the power-recovery shaft 107. That is, the expander 103, the low-pressure stage compressor 105, and the power-recovery shaft 107 function as a power recovery system 109 that recovers power from the refrigerant.
  • the expander 103 and the low-pressure stage compressor 105 are accommodated in a single closed casing 109a holding lubrication oil, together with the power-recovery shaft 107. Therefore, no particular sealing structure is needed.
  • the low-pressure stage compressor 105 has a larger volume than the expander 103.
  • the ratio (Vc/Ve) of the volume Vc of the low-pressure stage compressor 105 with respect to the volume Ve of the expander 103 is set, for example, to the range of 5 to 15.
  • the ratio (Vc/Ve) is set, for example, to the range of 30 to 40.
  • the ratio (Vc/Ve) also tends to increase.
  • the volume of the low-pressure stage compressor 105" means a confined volume, that is, the volume of the working chamber at the time of completion of the drawing process. This applies also to the expander 103.
  • the refrigeration cycle apparatus 100 is further provided with a high-pressure supply passage 130 and an on-off valve 131.
  • the high-pressure supply passage 130 is connected to the main refrigerant circuit 106 so as to communicate the flow passage 106a and the flow passage 106e.
  • the on-off valve 131 is provided on the high-pressure supply passage 130 and controls the flow of the refrigerant in the high-pressure supply passage 130.
  • the high-pressure supply passage 130 has an upstream end E 1 (one end) connected to the flow passage 106a and a downstream end E 2 (the other end) connected to the flow passage 106e. That is, the high-pressure supply passage 130 is a flow passage that can introduce the refrigerant in the flow passage 106a directly to the suction port of the low-pressure stage compressor 105 before the rotation of the power-recovery shaft 107.
  • the high-pressure supply passage 130 typically, is constituted by a refrigerant pipe.
  • the position of the upstream end E 1 is not limited to the position shown in Fig. 1 . That is, the position of the upstream end E 1 is not specifically limited, as long as a portion of the main refrigerant circuit 106 from the discharge port of the high-pressure stage compressor 101 to the suction port of the expander 103 and a portion of the main refrigerant circuit 106 from the outlet of the evaporator 104 to the suction port of the low-pressure stage compressor 105 can be communicated.
  • the high-pressure supply passage 130 may be connected to the main refrigerant circuit 106 so as to communicate the flow passage 106b and the flow passage 106e.
  • the high-pressure supply passage 130 may branch from the heat radiator 102.
  • the heat radiator 102 is constituted by an upstream part and a downstream part, the high-pressure supply passage 130 can easily branch from a portion between these two parts.
  • the density of the refrigerant in the flow passage 106a is lower than the density of the refrigerant in the flow passage 106b.
  • the refrigerant in the flow passage 106a is in a gas phase. It is possible to prevent the liquid refrigerant from flowing into the high-pressure stage compressor 101 through the low-pressure stage compressor 105 by supplying the gas refrigerant to the suction port of the low-pressure stage compressor 105 through the high-pressure supply passage 130. This prevents liquid compression in the high-pressure stage compressor 101, leading to an enhancement in reliability of the refrigeration cycle apparatus 100.
  • the on-off valve 131 and the check valve 132 form a flow passage-switching mechanism capable of selectively connecting one selected from the evaporator 104 and the high-pressure supply passage 130 to the low-pressure stage compressor 105.
  • the refrigerant is introduced from one selected from the evaporator 104 and the high-pressure supply passage 130 to the low-pressure stage compressor 105.
  • the check valve 132 is provided in a portion of the main refrigerant circuit 106 from the outlet of the evaporator 104 to the downstream end E 2 of the high-pressure supply passage 130 (flow passage 106e).
  • the on-off valve 131 is closed in the regular operation, and is opened in the activation of the refrigeration cycle apparatus 100. By opening the on-off valve 131, it is possible to supply the refrigerant in the flow passage 106a directly to the suction port of the low-pressure stage compressor 105 through the high-pressure supply passage 130. At that time, the check valve 132 can block the flow of the refrigerant from the high-pressure supply passage 130 toward the evaporator 104. On the other hand, by closing the on-off valve 131, it is possible to supply the refrigerant from the evaporator 104 to the low-pressure stage compressor 105 while restricting the flow of the refrigerant from the high-pressure supply passage 130 to the low-pressure stage compressor 105.
  • the check valve 132 has an advantage that there is no need for electrical control. Of course, it is also possible to replace the check valve 132 with a valve that can be arbitrarily opened and closed.
  • the refrigeration cycle apparatus 100 is further provided with the injection flow passage 111 and an injection flow-regulating valve 112.
  • the injection flow passage 111 serves to introduce the gas refrigerant separated from the liquid refrigerant in the gas-liquid separator 108, to a portion of the main refrigerant circuit 106 from the discharge port of the low-pressure stage compressor 105 to the suction port of the high-pressure stage compressor 101 (intermediate-pressure flow passage 106f).
  • the injection flow passage 111 is connected to the main refrigerant circuit 106 so as to communicate the gas refrigerant outlet of the gas-liquid separator 108 and the intermediate-pressure flow passage 106f.
  • the injection flow-regulating valve 112 is provided on the injection flow passage 111 and controls the flow of the refrigerant in the injection flow passage 111.
  • the injection flow passage 111 typically, is constituted by a refrigerant pipe.
  • a valve which allows the degree of opening to be varied stepwise, capable of expanding a refrigerant, typically, an electric expansion valve is preferably used.
  • the injection flow-regulating valve 112 serves to regulate the flow rate of the gas refrigerant to be injected into the intermediate-pressure flow passage 106f in the regular operation.
  • the injection flow-regulating valve 112 is fully opened or substantially fully opened in the activation of the refrigeration cycle apparatus 100.
  • the high-pressure stage compressor 101 can draw the refrigerant present in the flow passage 106c, the gas-liquid separator 108, the flow passage 106d, and the evaporator 104. This enables the pressure on the high-pressure side of the main refrigerant circuit 106 to increase rapidly.
  • the gas-liquid separator 108 is provided in this embodiment, it is possible to store a sufficient amount of refrigerant between the discharge port of the expander 103 and the check valve 132 during stoppage.
  • the gas refrigerant can be supplied from the gas-liquid separator 108 to the intermediate-pressure flow passage 106f through the injection flow passage 111 after the activation of the refrigeration cycle apparatus 100.
  • the degree of opening of each of the expansion valve 110 and the injection flow-regulating valve 112 it is possible to prevent the liquid refrigerant from flowing from the gas-liquid separator 108 into the intermediate-pressure flow passage 106f as well as preventing the backflow of the refrigerant from the intermediate-pressure flow passage 106f to the gas-liquid separator 108.
  • the refrigeration cycle apparatus 100 is further provided with a controller 117.
  • the expansion valve 110, the injection flow-regulating valve 112, and the on-off valve 131 are controlled by the controller 117.
  • the controller 117 typically, is constituted by a microcomputer.
  • a command to start the operation of the refrigeration cycle apparatus 100 is given to the controller 117 through an input device (not shown), a predetermined control program stored in an internal memory of the controller 117 is executed.
  • the controller 117 executes the predetermined activation control described below with reference to Fig. 2 .
  • the controller 117 controls the action of the motor 101b that drives the high-pressure stage compressor 101.
  • the refrigeration cycle apparatus 100 is further provided with an activation detector 119 that detects the activation of the expander 103 or the low-pressure stage compressor 105.
  • the controller 117 switches the control of the on-off valve 131 (flow passage-switching mechanism) from the control before the activation to the control after the activation, according to a detection result of the activation detector 119. Specifically, the on-off valve 131 is opened before the activation of the expander 103 and the low-pressure stage compressor 105 so that the refrigerant is introduced from the high-pressure supply passage 130 to the low-pressure stage compressor 105.
  • the on-off valve 131 is closed so that the refrigerant is introduced from the evaporator 104 to the low-pressure stage compressor 105.
  • the controller 117 closes the on-off valve 131. In this way, smooth transfer to the control in the regular operation can be achieved.
  • a temperature detector, a pressure detector, or the like can be used as the activation detector 119.
  • the activation detector 119 as a temperature detector for example, includes a temperature detecting element such as a thermocouple and a thermistor, and detects the difference AT between the temperature of the refrigerant at the suction port of the expander 103 and the temperature of the refrigerant at the discharge port of the expander 103.
  • the activation detector 119 as a pressure detector for example, includes a piezoelectric element, and detects the difference ⁇ P between the pressure of the refrigerant at the suction port of the expander 103 and the pressure of the refrigerant at the discharge port of the expander 103.
  • the activation detector 119 may include a timer that measures an elapsed time from the activation of the high-pressure stage compressor 101. Such a timer can be provided also as a function of the controller 117. In this case, the controller 117 itself can function as the activation detector 119. Furthermore, a contact or noncontact displacement sensor that detects the driving of the power-recovery shaft 107, such as an encoder, may be provided as the activation detector 119.
  • the method for detecting the activation of the power recovery system 109 differs as follows. According to the following methods, it is possible to detect the activation of the power recovery system 109 easily.
  • a threshold P th that has been determined experimentally or theoretically, for example, is preset in the controller 117.
  • the value obtained by subtracting the current pressure difference ⁇ P n+1 detected by the pressure detector from the pressure difference ⁇ P n (n: natural number) that has been detected by the pressure detector at a time going back for a unit time exceeds the specific threshold P th , the activation of the expander 103 or the low-pressure stage compressor 105 is detected.
  • a single threshold P th may be set, or a plurality of thresholds P th associated with the outdoor temperature or the like may be set. In the latter case, the controller 117 selects an optimal threshold P th on the basis of the outdoor temperature or the like. This applies also to other thresholds described below.
  • the difference ⁇ P between the pressure of the refrigerant at the suction port of the expander 103 and the pressure of the refrigerant at the discharge port of the expander 103 generally monotonically increases during the period after the activation of the high-pressure stage compressor 101 and before the activation of the expander 103.
  • the pressure difference ⁇ P turns to decrease temporarily, and becomes smaller than that immediately before the activation of the expander 103. It is possible to detect the activation of the expander 103 or the low-pressure stage compressor 105 by capturing this change in the pressure difference ⁇ P.
  • the pressure difference ⁇ P is detected at every unit time and stored in the memory of the controller 117.
  • the last pressure difference ⁇ P n previously stored in the memory and the current pressure difference ⁇ P n+1 are compared.
  • the expander 103 or the low-pressure stage compressor 105 can be determined to have been activated.
  • the expander 103 or the low-pressure stage compressor 105 can be determined to have been activated.
  • the "unit time" can be set arbitrarily to a sufficient time to capture a sudden decrease in the pressure difference ⁇ P, for example, in the range of 1 to 5 seconds.
  • the pressure difference ⁇ P it is also possible to use the temperature difference ⁇ T. That is, when a value obtained by subtracting the current temperature difference ⁇ T n+1 detected by the temperature detector from the temperature difference ⁇ T n (n: natural number) that has been detected by the temperature detector at a time going back for a unit time exceeds a specific threshold T th , the activation of the expander 103 or the low-pressure stage compressor 105 is detected.
  • the activation of the power recovery system 109 can be detected on the basis of the discharge temperature from the expander 103 or the discharge pressure from the expander 103.
  • the expander 103 is also rotated.
  • the expander 103 draws the refrigerant, then expands the drawn refrigerant, and discharges it. Therefore, the temperature and pressure of the refrigerant after being discharged from the expander 103 are lower than those before being drawn.
  • the power recovery system 109 can be determined to have been activated by capturing a sudden change in the temperature (or pressure) at the discharge port of the expander 103 while monitoring the temperature (or pressure) in chronological order.
  • the activation of the expander 103 or the low-pressure stage compressor 105 may be detected by the method described below.
  • the below-described method is rather a method of determining whether the power recovery system 109 is in a state that allows continuous operation, than a method of capturing the activation of the expander 103 or the low-pressure stage compressor 105.
  • the control of the on-off valve 131 can be switched from the control before the activation to the control after the activation according to the detected results. In this way, the power recovery system 109 continues to operate stably even after the on-off valve 131 is closed.
  • a threshold T 1 that has been determined experimentally or theoretically, for example, is preset in the controller 117.
  • the temperature difference ⁇ T detected by the temperature detector exceeds the threshold T 1 , the activation of the expander 103 or the low-pressure stage compressor 105 is detected.
  • a threshold P 1 that has been determined experimentally or theoretically, for example, is preset in the controller 117.
  • the pressure difference ⁇ P detected by the pressure detector exceeds the specific threshold P 1 , the activation of the expander 103 or the low-pressure stage compressor 105 is detected.
  • the reason why the activation of the expander 103 or the low-pressure stage compressor 105 can be detected by comparison between the temperature difference AT and the threshold T 1 , or comparison between the pressure difference ⁇ P and the threshold P 1 is as follows.
  • the high-pressure stage compressor 101 When the high-pressure stage compressor 101 is activated, the refrigerant discharged from the high-pressure stage compressor 101 is supplied to the suction port of the low-pressure stage compressor 105 through the high-pressure supply passage 130. This activates the power recovery system 109.
  • the low-pressure stage compressor 105 serves as a driving source, the power recovery system 109 starts to rotate before the temperature difference between the suction temperature of the high-pressure stage compressor 101 and the discharge temperature of the high-pressure stage compressor 101 becomes significant.
  • the power to rotate the expander 103 and the low-pressure stage compressor 105 also increases, and the rotational speed of the power recovery system 109 increases. Then, when a high rotational speed is achieved, the power recovery system 109 stably rotates under the influence of the inertial force.
  • the on-off valve 131 is desirably maintained open until such a stable rotation state is reached.
  • the suction temperature of the expander 103 gradually increases from the temperature during stoppage, which is substantially the same as the outdoor temperature.
  • the discharge temperature (or discharge pressure) of the expander 103 is determined.
  • the refrigerant is carbon dioxide.
  • the suction temperature of the expander 103 and the discharge temperature of the expander 103 each gradually increase as mentioned above.
  • the difference between the suction temperature and the discharge temperature gradually increase as well. This applies also to the pressure. Therefore, the activation of the power recovery system 109 can be detected by setting appropriate values as the threshold T 1 and the threshold P 1 , e.g., respective values that are slightly larger than the temperature difference and the pressure difference to be reached when the activation of the power recovery system 109 can be estimated.
  • a threshold time t 1 that has been determined experimentally or theoretically, for example, is preset in the controller 117.
  • the time t measured by the timer exceeds the threshold time t 1 , the activation of the expander 103 or the low-pressure stage compressor 105 is detected.
  • the "threshold time t 1 " is written in the activation control program to be executed by the controller 117.
  • the time from the activation of the high-pressure stage compressor 101 to the activation of the low-pressure stage compressor 105 is actually measured under various operational conditions (such as outdoor temperatures). Then, a time at which the activation of the low-pressure stage compressor 105 can be surely determined under all the operational conditions can be set as the "threshold time t 1 ".
  • a model of the refrigeration cycle apparatus 100 is constructed, and a pressure difference that is necessary and sufficient to activate the power recovery system 109 is estimated by computer simulation.
  • the initial activation time necessary to produce the estimated pressure difference is calculated.
  • the calculated initial activation time can be set as the "threshold time t 1 ".
  • the method for detecting the activation of the expander 103 or the low-pressure stage compressor 105 is not limited to one, and a plurality of methods can be performed in combination.
  • the activation of the expander 103 or the low-pressure stage compressor 105 is accurately captured by a method of monitoring the pressure difference ⁇ P and/or the temperature difference ⁇ T between the suction port and the discharge port of the expander 103.
  • whether the power recovery system 109 is in a state that allows continuous operation is determined by a method of comparing the temperature difference ⁇ T with the threshold T 1 , a method of comparing the pressure difference ⁇ P with the threshold P 1 , or a method of comparing the elapsed time t with the threshold time t 1 .
  • the expander 103 or the low-pressure stage compressor 105 is determined to be activated, and the on-off valve 131 is closed.
  • Fig. 2 is a flow chart showing the activation control of the refrigeration cycle apparatus 100.
  • the refrigeration cycle apparatus 100 starts the regular operation after performing the activation control shown in Fig. 2 .
  • the high-pressure stage compressor 101 is stopped, the expansion valve 110 is opened, and the pressure of the refrigerant in the main refrigerant circuit 106 is substantially uniform.
  • the controller 117 transmits control signals to the actuators of the expansion valve 110 and the injection flow-regulating valve 112 so that these valves 110 and 112 are fully opened (step S12). Further, it transmits control signals to the actuator of the on-off valve 131 so that the on-off valve 131 is opened (step S13). This allows the high-pressure supply passage 130 to be open.
  • the controller 117 starts to supply power to the motor 101b in order to activate the high-pressure stage compressor 101 (step S14).
  • This activates the high-pressure stage compressor 101 and causes the refrigerant present in the intermediate-pressure flow passage 106f, the injection flow passage 111, the flow passage 106c, the gas-liquid separator 108, the flow passage 106d, the evaporator 104, and a part of the flow passage 106e (portion between the evaporator 104 and the check valve 132) to be drawn into the high-pressure stage compressor 101.
  • the on-off valve 131 instead of opening the on-off valve 131 before the activation of the high-pressure stage compressor 101, it is also possible to open the on-off valve 131 upon the activation of the high-pressure stage compressor 101.
  • a fan or pump that causes a fluid (air or water) for heat exchange with the refrigerant to flow into the heat radiator 102 is activated. This can prevent an excessive increase in the high pressure of the cycle.
  • a fan or pump of the evaporator 104 is activated upon the activation of the high-pressure stage compressor 101. This allows efficient production of the gas refrigerant to be drawn into the high-pressure stage compressor 101.
  • the internal pressure of the intermediate-pressure flow passage 106f, etc. decreases.
  • the pressure in flow passages from the discharge port of the high-pressure stage compressor 101 to the suction port of the expander 103 the flow passage 106a, the heat radiator 102, and the flow passage 106b
  • the high-pressure supply passage 130, and a part of the flow passage 106e portions between the check valve 132 and the suction port of the low-pressure stage compressor 105) increases.
  • the pressure at the suction port of each of the expander 103 and the low-pressure stage compressor 105 is rendered relatively high, and the pressure at the discharge port of each of the expander 103 and the low-pressure stage compressor 105 is rendered relatively low. That is, a pressure difference can be produced not only between the suction port and the discharge port of the expander 103, but also between the suction port and the discharge port of the low-pressure stage compressor 105.
  • the pressure difference of the refrigerant acts on each of the expander 103 and the low-pressure stage compressor 105, and thus self-activation of the power recovery system 109 can be achieved easily.
  • the high-pressure stage compressor 101 can draw a sufficient amount of the refrigerant to produce a large pressure difference because the injection flow passage 111 and the gas-liquid separator 108 are provided.
  • step S15 Upon detecting the activation of the low-pressure stage compressor 105 through the activation detector 119 (step S15), the controller 117 transmits control signals to the actuator of the on-off valve 131 so that the on-off valve 131 is closed (step S16). This allows the backpressure acting on the check valve 132 to be released, and the refrigerant is supplied from the evaporator 104 to the low-pressure stage compressor 105 through the flow passage 106e. Meanwhile, the gas-liquid two-phase refrigerant whose pressure has been reduced in the expander 103 is supplied to the gas-liquid separator 108.
  • each of the expansion valve 110 and the injection flow-regulating valve 112 is adjusted so that excess supply of the liquid refrigerant to the high-pressure stage compressor 101 through the injection flow passage 111 and the flow passage 106f is prevented (step S17). After the completion of the activation control shown in Fig. 2 , transfer to the regular operation where the refrigerant is circulated in the main refrigerant circuit 106 is performed in the refrigeration cycle apparatus 100.
  • the rotational speed of the high-pressure stage compressor 101 is progressively reduced.
  • the refrigerant moves through the high-pressure stage compressor 101, the expander 103, and the low-pressure stage compressor 105, taking sufficient time. Therefore, the pressure difference in the main refrigerant circuit 106 is naturally released, and the pressure in the main refrigerant circuit 106 becomes substantially uniform to be stabilized. This causes the expander 103 and the low-pressure stage compressor 105 to be stopped naturally.
  • the high-pressure stage compressor 101 can draw and compress the refrigerant in the evaporator 104 and the gas-liquid separator 108 in the activation of the refrigeration cycle apparatus 100. Therefore, the pressure in flow passages from the discharge port of the high-pressure stage compressor 101 to the suction port of the expander 103 can be rapidly increased. Since a large pressure difference is produced between the suction port and the discharge port of the expander 103, the power recovery system 109 is self-activated smoothly.
  • the compressed refrigerant is introduced into a part of the flow passage 106e from the check valve 132 to the suction port of the low-pressure stage compressor 105 through the high-pressure supply passage 130.
  • This produces a large pressure difference also between the suction port and the discharge port of the low-pressure stage compressor 105.
  • This fact contributes to a smoother self-activation of the power recovery system 109.
  • the low-pressure stage compressor 105 and the expander 103 each have a certain suction volume. Particularly, when the suction volume of the low-pressure stage compressor 105 is larger than the suction volume of the expander 103, the power recovery system 109 is activated more smoothly by producing a pressure difference between the suction port and the discharge port of the low-pressure stage compressor 105.
  • the controller 117 stops the high-pressure stage compressor 101 and performs the control to activate the power recovery system 109 again. In this way, it is possible to prevent an excessive increase in the pressure in flow passages from the discharge port of the high-pressure stage compressor 101 to the suction port of the expander 103. It is also possible to prevent damages to the components of the expander 103 from occurring due to an excessive pressure difference between before and after the expander 103. Thus, the reliability of the refrigeration cycle apparatus 100 can be improved.
  • the heat radiator 102 is connected to the suction port of the expander 103
  • the evaporator 104 is connected to the suction port of the low-pressure stage compressor 105
  • the gas-liquid separator 108 is connected to the discharge port of the expander 103.
  • the gas-liquid separator 108 is connected also to the discharge port of the low-pressure stage compressor 105 via the injection flow passage 111. Since the volumes of the heat radiator 102, the evaporator 104, and the gas-liquid separator 108 are comparatively large, these components can function as a buffer space for the refrigerant in the activation of the refrigeration cycle apparatus 100. Thus, an effect of suppressing the pressure pulsation in the activation can be obtained.
  • refrigerant working fluid
  • fluorine refrigerant such as R410A
  • natural refrigerant such as carbon dioxide
  • low GWP (Global Warming Potential) refrigerant such as R1234yf
  • Fig. 3 is a configuration diagram of a refrigeration cycle apparatus 200 in Modification 1.
  • the flow passage-switching mechanism is constituted by a three-way valve 133 in the refrigeration cycle apparatus 200.
  • a PTC (Positive Temperature Coefficient) heater 140 and a current detector 141 are used as the activation detector 119.
  • a bypass flow passage 201 and a bypass valve 202 are provided as the activation detector 119.
  • Other configurations are the same as those in Embodiment 1.
  • the same components as those in Embodiment 1 are denoted by the same reference numerals, and the detailed descriptions thereof are omitted.
  • the three-way valve 133 as a flow passage-switching mechanism is provided at the downstream end E 2 of the high-pressure supply passage 130 so as to be capable of switching between a first state in which the refrigerant is introduced from the evaporator 104 into the low-pressure stage compressor 105 and a second state in which the refrigerant is introduced from the high-pressure supply passage 130 into the low-pressure stage compressor 105.
  • the first state the flow of the refrigerant from the high-pressure supply passage 130 to the low-pressure stage compressor 105 is blocked.
  • the second state the flow of the refrigerant from the evaporator 104 to the low-pressure stage compressor 105 is blocked.
  • the on-off valve 131 and the check valve 132 in Embodiment 1 can be replaced with the three-way valve 133.
  • the three-way valve 133 can suppress an increase in the number of components.
  • the bypass flow passage 201 is connected to the main refrigerant circuit 106 so as to bypass the expander 103.
  • the upstream end E 3 of the bypass flow passage 201 is located on the flow passage 106b, and the downstream end E 4 thereof is located on the flow passage 106c.
  • the bypass valve 202 is provided on the bypass flow passage 201.
  • the bypass flow passage 201 typically, is constituted by a refrigerant pipe.
  • As the bypass valve 202 a valve, which allows the degree of opening to be varied stepwise, capable of expanding a refrigerant, typically, an electric expansion valve is preferably used.
  • the current detector 141 detects the magnitude of the current flowing in the PTC heater 140.
  • the PTC heater 140 is provided in a portion of the main refrigerant circuit 106 from the outlet of the heat radiator 102 to the suction port of the expander 103, that is, on the flow passage 106b. Specifically, the PTC heater 140 is located on the expander 103 side as seen from the upstream end E 3 of the bypass flow passage 201. When the PTC heater 140 is provided at such a position, the PTC heater 140 is less likely to be affected by the flow of the refrigerant toward the bypass flow passage 201. Therefore, it is possible to detect the flow of the refrigerant into the expander 103 accurately.
  • a threshold ⁇ I 1 that has been determined experimentally or theoretically, for example, is preset in the controller 117.
  • the power recovery system 109 When the power recovery system 109 is activated, the refrigerant starts to flow also at the suction port of the expander 103. Then, the magnitude of the current also suddenly changes due to the temperature change (temperature reduction) of the PTC heater 140.
  • the amount of change per unit time in the current flowing in the PTC heater 140 can be preset as the threshold ⁇ I 1 .
  • the "unit time" for example, can be set arbitrarily in the range of 1 to 5 seconds.
  • the amount of change per unit time in the current flowing in the PTC heater 140 is calculated by the current detector 141, and when the calculated amount of change exceeds the threshold ⁇ I 1 , the activation of the expander 103 or the low-pressure stage compressor 105 is detected.
  • the PTC heater 140 and the current detector 141 can be used also in other embodiments and modifications.
  • Fig. 4 is a flow chart showing the activation control of the refrigeration cycle apparatus 200.
  • the controller 117 transmits control signals to the actuators of the expansion valve 110, the injection flow-regulating valve 112, and the bypass valve 202 so that the expansion valve 110 and the injection flow-regulating valve 112 are fully opened as well as the bypass valve 202 is opened to a specific degree (step S22).
  • the phrase "the bypass valve 202 is opened to a specific degree” means to be set within a range of the degree of opening that allows the pressure difference between the suction port and the discharge port of the expander 103 to be maintained to the level that is required for the activation of the expander 103.
  • This "specific degree of opening" can be determined experimentally or theoretically.
  • the bypass valve 202 is slightly opened so as to prevent excessive reduction in the pressure difference between before and after the expander 103.
  • step S23 the low-pressure stage compressor 105 and the high-pressure supply passage 130 are connected by controlling the three-way valve 133 (step S23).
  • the controller 117 starts to supply power to the motor 101b in order to activate the high-pressure stage compressor 101 (step S24).
  • This activates the high-pressure stage compressor 101 and causes the refrigerant present in the intermediate-pressure flow passage 106f, the injection flow passage 111, the flow passage 106c, the gas-liquid separator 108, the flow passage 106d, the evaporator 104, and a part of the flow passage 106e (portion between the evaporator 104 and the three-way valve 133) to be drawn into the high-pressure stage compressor 101.
  • the controller 117 Upon detecting the activation of the low-pressure stage compressor 105 through the activation detector 119 (step S25), the controller 117 controls the three-way valve 133 so that the low-pressure stage compressor 105 and the evaporator 104 are connected (step S26). This allows the refrigerant to be supplied from the evaporator 104 to the low-pressure stage compressor 105 through the flow passage 106e.
  • the opening degree of each of the expansion valve 110 and the injection flow-regulating valve 112 is adjusted because of the same reason as in Embodiment 1 (step S27). Further, the bypass valve 202 is closed. Thereafter, transfer to the regular operation is performed.
  • the controller 117 opens the bypass valve 202, before the activation of the expander 103 and the low-pressure stage compressor 105, to a degree within the range that allows a pressure difference required for the activation of the expander 103 to be produced between the suction port and the discharge port of the expander 103. That is, the activation of the power recovery system 109 is attempted while the bypass valve 202 is slightly opened. The controller 117 closes the bypass valve 202 after the activation of the expander 103 and the low-pressure stage compressor 105.
  • Fig. 5 is a configuration diagram of a refrigeration cycle apparatus 300 in Modification 2.
  • the refrigeration cycle apparatus 300 differs from Embodiment 1 in that a temperature detector that detects the temperature of the refrigerant at the discharge port of the low-pressure stage compressor 105 is used as the activation detector 119.
  • the same components as those in Embodiment 1 are denoted by the same reference numerals, and the detailed descriptions thereof are omitted.
  • a threshold T 2 that has been determined experimentally or theoretically, for example, is preset in the controller 117.
  • the temperature of the refrigerant at the discharge port of the low-pressure stage compressor 105 is low during the period after the activation of the high-pressure stage compressor 101 and before the activation of the expander 103.
  • the temperature of the refrigerant at the discharge port of the low-pressure stage compressor 105 suddenly increases.
  • the change in the temperature of the refrigerant at the discharge port of the low-pressure stage compressor 105 is about 10°C, though it depends also on the intended use, operational conditions, etc., of the refrigeration cycle apparatus 100. By capturing this temperature change, the activation of the expander 103 or the low-pressure stage compressor 105 can be detected.
  • the temperature T of the refrigerant at the discharge port of the low-pressure stage compressor 105 is detected per unit time and stored in the memory of the controller 117. Then, the last temperature T n (n: natural number) previously stored in the memory and the current temperature T n+1 are compared. When the current temperature T n+1 significantly exceeds the last past temperature T n , in other words, when (T n+1 -T n ) > T 2 is satisfied, the expander 103 or the low-pressure stage compressor 105 can be determined to have been activated. It should be noted that the "unit time" can be set to a sufficient time to capture the sudden reduction in the temperature T, for example, can be arbitrarily set in the range of 1 to 5 seconds.
  • the low-pressure stage compressor 105 Upon the activation of the low-pressure stage compressor 105, the refrigerant at high pressure and high temperature is drawn into the low-pressure stage compressor 105 from the high-pressure supply passage 130. Since the pressure in the flow passage 106f is low, the low-pressure stage compressor 105 temporarily functions as an expander. The refrigerant that has been expanded in the low-pressure stage compressor 105 is discharged into the flow passage 106f. The refrigerant that has been compressed in the high-pressure stage compressor 101 and that has been expanded again in the low-pressure stage compressor 105 obtains an enthalpy corresponding to the loss occurring in each of the high-pressure stage compressor 101 and the low-pressure stage compressor 105.
  • the refrigerant present in the flow passage 106f flows through the high-pressure stage compressor 101 and the low-pressure stage compressor 105, and when it returns to the flow passage 106f again, the temperature of the refrigerant increases by the increment in the enthalpy of the refrigerant.
  • the temperature detector detects the activation of the low-pressure stage compressor 105 by comparing the temperature increase with the threshold T 2 .
  • the following effects can be obtained in addition to the effects described in Embodiment 1.
  • the activation is detected on the basis of the temperature of the refrigerant at the discharge port of the low-pressure stage compressor 105. This can ensure the capture of the activation of the power recovery system 109, thereby enabling rapid transfer to the regular operation.
  • Fig. 8 is a configuration diagram of a refrigeration cycle apparatus 400 in Embodiment 2. As shown in Fig. 8 , the refrigeration cycle apparatus 400 differs from Embodiment 1 in that the high-pressure supply passage 130, the on-off valve 131, and the check valve 132 are omitted. In this embodiment, the same components as those in Embodiment 1 are denoted by the same reference numerals, and the detailed descriptions thereof are omitted.
  • activation control that is different from that in Embodiment 1 is performed. That is, the expansion valve 110 is fully closed in the activation of the refrigeration cycle apparatus 400. This allows the pressure at the suction port of the low-pressure stage compressor 105 to be maintained at the pressure in a standby state (before the activation of the high-pressure stage compressor 101). Upon the activation of the high-pressure stage compressor 101, a pressure difference occurs between the suction port and the discharge port of the expander 103. Likewise, a pressure difference occurs between the suction port and the discharge port of the low-pressure stage compressor 105. As a result, the power recovery system 109 is activated.
  • the injection flow-regulating valve 112 is fully opened or substantially fully opened.
  • the high-pressure stage compressor 101 can draw the refrigerant present in the flow passage 106c, the gas-liquid separator 108, and a part of the flow passage 106d. This enables the pressure on the high-pressure side of the main refrigerant circuit 106 to increase rapidly.
  • the gas-liquid separator 108 is provided in this embodiment, it is possible to store a sufficient amount of refrigerant between the discharge port of the expander 103 and the expansion valve 110 during stoppage.
  • the controller 117 controls the expansion valve 110 according to a detection result of the activation detector 119. Specifically, it fully closes the expansion valve 110 in the activation of the refrigeration cycle apparatus 400. This can prevent the pressure at the suction port of the low-pressure stage compressor 105 from being equal to the pressure at the discharge port of the low-pressure stage compressor 105 via the injection flow passage 111.
  • the controller 117 opens the expansion valve 110 after the activation of the expander 103 and the low-pressure stage compressor 105. For example, upon the reception of signals that indicate the activation of the low-pressure stage compressor 105 from the activation detector 119, the controller 117 fully opens the expansion valve 110.
  • the activation of the power recovery system 109 can be detected by the method described in Embodiment 1.
  • the control of the expansion valve 110 can be switched from the control before the activation to the control after the activation, according to the detection result. In this way, after the expansion valve 110 is opened, the power recovery system 109 continues to operate stably.
  • a temperature detector that detects the temperature of the refrigerant in a portion of the main refrigerant circuit 106 from the expansion valve 110 to the suction port of the low-pressure stage compressor 105 (a part of the flow passage 106d, the evaporator 104, and the flow passage 106e) can be further used as the activation detector 119.
  • the difference between a temperature in a standby state (before the activation of the high-pressure stage compressor 101) detected by the temperature detector and the current temperature detected by the temperature detector exceeds a specific threshold To, the activation of the expander 103 or the low-pressure stage compressor 105 is detected.
  • a temperature detector that detects the evaporation temperature of the refrigerant in the evaporator 104 can be used as the activation detector 119.
  • a pressure detector that detects the pressure of the refrigerant in a portion of the main refrigerant circuit 106 from the expansion valve 110 to the suction port of the low-pressure stage compressor 105 can be used as the activation detector 119.
  • the difference between a pressure in a standby state detected by the pressure detector and the current pressure detected by the pressure detector exceeds a specific threshold Po, the activation of the expander 103 or the low-pressure stage compressor 105 is detected.
  • the low-pressure stage compressor 105 draws the refrigerant present in the evaporator 104. This causes a reduction in the temperature and the pressure in the evaporator 104.
  • An optimal threshold To or threshold Po determined by an experimental or theoretical technique is preset in the controller 117.
  • the activation of the power recovery system 109 can be detected by comparing the temperature change in flow passages from the expansion valve 110 to the suction port of the low-pressure stage compressor 105 (flow passages on the low-pressure side) with the threshold To.
  • the activation of the power recovery system 109 can be detected by comparing the pressure change in flow passages on the low-pressure side with the threshold Po.
  • the method for detecting the activation of the expander 103 or the low-pressure stage compressor 105 is not limited to one, and a plurality of methods can be performed in combination.
  • the activation of the expander 103 or the low-pressure stage compressor 105 is accurately captured by a method of monitoring the temperature or pressure of the refrigerant in a portion of the main refrigerant circuit 106 from the expansion valve 110 to the suction port of the low-pressure stage compressor 105.
  • the power recovery system 109 is in a state that allows continuous operation is determined by a method of comparing the temperature difference AT with the threshold T 1 , a method of comparing the pressure difference ⁇ P with the threshold P 1 , or a method of comparing the elapsed time t with the threshold time t 1 .
  • the expander 103 or the low-pressure stage compressor 105 is determined to have been activated, and the expansion valve 110 is opened.
  • Fig. 9 is a flow chart showing the activation control of the refrigeration cycle apparatus 400.
  • the refrigeration cycle apparatus 400 starts the regular operation after performing the activation control shown in Fig. 9 .
  • the high-pressure stage compressor 101 is stopped, the expansion valve 110 and the injection valve 112 are opened, and the pressure of the refrigerant in the main refrigerant circuit 106 is substantially uniform.
  • step ST11 When an activation command is input in step ST11, the controller 117 transmits control signals to the actuator of the expansion valve 110 so that the expansion valve 110 is closed (fully closed) (step ST12).
  • the controller 117 starts to supply power to the motor 101b in order to activate the high-pressure stage compressor 101 (step ST13).
  • This activates the high-pressure stage compressor 101 and causes the refrigerant present in the intermediate-pressure flow passage 106f, the injection flow passage 111, the flow passage 106c, the gas-liquid separator 108, and a part of the flow passage 106d (portion between the gas-liquid separator 108 and the expansion valve 110) to be drawn into the high-pressure stage compressor 101.
  • a fan or pump that causes a fluid (air or water) for heat exchange with the refrigerant to flow into the heat radiator 102 is activated, corresponding to the activation of the high-pressure stage compressor 101. This can prevent an excessive increase in the high pressure of the cycle.
  • the fan or pump of the evaporator 104 may be activated corresponding to the activation of the high-pressure stage compressor 101, or may be activated after the expansion valve 110 is opened. In order to maintain the pressure at the suction port of the low-pressure stage compressor 105 to the pressure in a standby state, the latter operation is recommended.
  • the internal pressure of the intermediate-pressure flow passage 106f, etc. decreases.
  • the pressure in flow passages from the discharge port of the high-pressure stage compressor 101 to the suction port of the expander 103 increases.
  • the pressure of the refrigerant in flow passages from the expansion valve 110 to the suction port of the low-pressure stage compressor 105 (a part of the flow passage 106d, the evaporator 104, and the flow passage 106e) is maintained to the pressure in the refrigerant circuit 106 during stoppage of the refrigeration cycle apparatus 400.
  • a pressure difference can be produced not only between the suction port and the discharge port of the expander 103, but also between the suction port and the discharge port of the low-pressure stage compressor 105.
  • the pressure difference of the refrigerant acts on each of the expander 103 and the low-pressure stage compressor 105, and thus self-activation of the power recovery system 109 can be achieved easily.
  • the high-pressure stage compressor 101 can draw a sufficient amount of the refrigerant to produce a large pressure difference because the injection flow passage 111 and the gas-liquid separator 108 are provided.
  • the controller 117 Upon detecting the activation of the low-pressure stage compressor 105 through the activation detector 119 (step ST14), the controller 117 transmits control signals to the actuator of the expansion valve 110 so that the expansion valve 110 is fully opened (or substantially fully opened) (step ST15). This causes the gas-liquid two-phase refrigerant whose pressure has been reduced in the expander 103 to be supplied to the gas-liquid separator 108.
  • step ST15 the controller 117 transmits control signals to the actuator of the expansion valve 110 so that the expansion valve 110 is fully opened (or substantially fully opened) (step ST15). This causes the gas-liquid two-phase refrigerant whose pressure has been reduced in the expander 103 to be supplied to the gas-liquid separator 108.
  • transfer to the regular operation where the refrigerant is circulated in the main refrigerant circuit 106 is performed in the refrigeration cycle apparatus 400.
  • the opening degree of each of the expansion valve 110 and the injection flow-regulating valve 112 is adjusted so that excess supply of the liquid refrigerant
  • the operation of the refrigeration cycle apparatus 400 can be stopped according to the method described in Embodiment 1.
  • the high-pressure stage compressor 101 can draw and compress the refrigerant in the gas-liquid separator 108 in the activation of the refrigeration cycle apparatus 400. Therefore, the pressure in flow passages from the discharge port of the high-pressure stage compressor 101 to the suction port of the expander 103 can be increased rapidly. Since a large pressure difference is produced between the suction port and the discharge port of the expander 103, the power recovery system 109 is self-activated smoothly.
  • the low-pressure stage compressor 105 and the expander 103 each have a certain suction volume.
  • the power recovery system 109 is activated more smoothly by producing a pressure difference between the suction port and the discharge port of the low-pressure stage compressor 105.
  • the controller 117 stops the high-pressure stage compressor 101 and performs the control to activate the power recovery system 109 again. That is, when a failure of the activation is detected, the expansion valve 110 is once fully opened. Thereafter, the activation control described with reference to Fig. 9 is performed. In this way, it is possible to prevent an excessive increase in the pressure in flow passages from the discharge port of the high-pressure stage compressor 101 to the suction port of the expander 103. It is also possible to prevent damages to the components of the expander 103 from occurring due to an excessive pressure difference between before and after the expander 103. Thus, the reliability of the refrigeration cycle apparatus 400 can be improved.
  • the method for detecting a failure in the activation of the power recovery system 109 is not specifically limited.
  • the current temperature (or pressure) of the refrigerant in flow passages from the expansion valve 110 to the suction port of the low-pressure stage compressor 105 (flow passages on the low-pressure side), e.g., in the evaporator 104 is detected.
  • the difference between the detected temperature (or pressure) and a reference temperature (or reference pressure) does not reach a specific threshold within a certain period of time, the power recovery system 109 can be determined to have failed to be activated.
  • the threshold the aforementioned threshold To or threshold P 0 can be used.
  • the temperature (or pressure) of the refrigerant in the evaporator 104 before the activation of the high-pressure stage compressor 101 can be used. In the case where a certain period of time has elapsed without detecting the activation of the power recovery system 109 after the activation of the high-pressure stage compressor 101, it can be determined that the activation of the power recovery system 109 has been failed.
  • Fig. 10 is a configuration diagram of a refrigeration cycle apparatus 500 in Modification 3. As shown in Fig. 10 , the refrigeration cycle apparatus 500 is provided with the bypass flow passage 201 and the bypass valve 202. Other configurations are the same as those in Embodiment 2. In this modification, the same components as those in Embodiment 2 are denoted by the same reference numerals, and the detailed descriptions thereof are omitted.
  • the bypass flow passage 201 is connected to the main refrigerant circuit 106 so as to bypass the expander 103.
  • the upstream end E 3 of the bypass flow passage 201 is located on the flow passage 106b, and the downstream end E 4 thereof is located on the flow passage 106c.
  • the bypass valve 202 is provided on the bypass flow passage 201.
  • the bypass flow passage 201 typically, is constituted by a refrigerant pipe.
  • As the bypass valve 202 a valve, which allows the degree of opening to be varied stepwise, capable of expanding a refrigerant, typically, an electric expansion valve is preferably used.
  • the element portion of the activation detector 119 is provided on the flow passage 106b.
  • the element portion of the activation detector 119 may be located on the heat radiator 102 side, or may be located on the expander 103 side, as seen from the upstream end E 3 of the bypass flow passage 201.
  • Fig. 11 is a flow chart showing the activation control of the refrigeration cycle apparatus 500.
  • the controller 117 transmits control signals to the actuators of the expansion valve 110 and the bypass valve 202 so that the expansion valve 110 is fully closed, and the bypass valve 202 is opened to a specific degree (step ST22).
  • the phrase "the bypass valve 202 is opened to a specific degree” means to be set within a range of the degree of opening that allows the pressure difference between the suction port and the discharge port of the expander 103 to be maintained to the level that is required for the activation of the expander 103.
  • This "specific degree of opening" can be determined experimentally or theoretically.
  • the bypass valve 202 is slightly opened so as to prevent excessive reduction in the pressure difference between before and after the expander 103.
  • the controller 117 starts to supply power to the motor 101b in order to activate the high-pressure stage compressor 101 (step ST23). This activates the high-pressure stage compressor 101 and causes the refrigerant present in the intermediate-pressure flow passage 106f, the injection flow passage 111, the flow passage 106c, the gas-liquid separator 108, and a part of the flow passage 106d to be drawn into the high-pressure stage compressor 101.
  • a pressure difference can be produced not only between the suction port and the discharge port of the expander 103, but also between the suction port and the discharge port of the low-pressure stage compressor 105.
  • the pressure difference of the refrigerant acts on each of the expander 103 and the low-pressure stage compressor 105, and thus self-activation of the power recovery system 109 can be achieved easily.
  • the controller 117 Upon detecting the activation of the low-pressure stage compressor 105 through the activation detector 119 (step ST24), the controller 117 transmits control signals to the actuator of the expansion valve 110 so that the expansion valve 110 is fully opened (or substantially fully opened) (step ST25). Further, it transmits control signals to the actuator of the bypass valve 202 so that the bypass valve 202 is fully closed.
  • the controller 117 opens the bypass valve 202, before the activation of the expander 103 and the low-pressure stage compressor 105, to a degree within the range that allows a pressure difference required for the activation of the expander 103 to be produced between the suction port and the discharge port of the expander 103. That is, the activation of the power recovery system 109 is attempted while the bypass valve 202 is slightly opened. The controller 117 closes the bypass valve 202 after the activation of the expander 103 and the low-pressure stage compressor 105.
  • Fig. 12 is a configuration diagram of a refrigeration cycle apparatus 600 in Modification 4. As shown in Fig. 12 , the refrigeration cycle apparatus 600 is further provided with a bypass flow passage 301 and a bypass valve 302. Other configurations are the same as in Embodiment 2. In this modification, the same components as those in Embodiment 2 are denoted by the same reference numerals, and the detailed descriptions thereof are omitted.
  • the bypass flow passage 301 is connected to the main refrigerant circuit 106 so as to communicate the flow passage 106b and the flow passage 106d.
  • the bypass valve 302 is provided on the bypass flow passage 301 and controls the flow of the refrigerant in the bypass flow passage 301.
  • the bypass flow passage 301 typically, is constituted by a refrigerant pipe.
  • an on-off valve can be used as the bypass valve 302
  • the bypass flow passage 301 has an upstream end E 5 located at a portion of the main refrigerant circuit 106 from the outlet of the heat radiator 102 to the suction port of the expander 103 (the flow passage 106b), and a downstream end E 6 located at a portion of the main refrigerant circuit 106 from the expansion valve 110 to the inlet of the evaporator 104 (a part of the flow passage 106d).
  • the bypass flow passage 301 allows the refrigerant at high pressure in the flow passage 106b to be introduced directly to the suction port of the low-pressure stage compressor 105.
  • the positions of the upstream end E 5 and the downstream end E 6 are not limited to the positions shown in Fig. 12 . That is, as long as the portion of the main refrigerant circuit 106 from the discharge port of the high-pressure stage compressor 101 to the suction port of the expander 103 and a portion of the main refrigerant circuit 106 from the expander 110 to the suction port of the low-pressure stage compressor 105 can be communicated, the position of the upstream end E 5 is not specifically limited.
  • the bypass flow passage 301 may be connected to the main refrigerant circuit 106 so as to communicate the flow passage 106a and the flow passage 106e.
  • the bypass flow passage 301 may branch from the heat radiator 102.
  • the bypass flow passage 301 can easily branch from a portion between these two parts.
  • Fig. 13 is a flow chart showing the activation control of the refrigeration cycle apparatus 600.
  • the controller 117 transmits control signals to the actuators of the expansion valve 110 and the bypass valve 302 so that the expansion valve 110 is fully closed, and the bypass valve 302 is fully opened (step ST32).
  • the controller 117 starts to supply power to the motor 101b in order to activate the high-pressure stage compressor 101 (step ST33). This activates the high-pressure stage compressor 101 and causes the refrigerant present in the intermediate-pressure flow passage 106f, the injection flow passage 111, the flow passage 106c, the gas-liquid separator 108, and a part of the flow passage 106d to be drawn into the high-pressure stage compressor 101.
  • a large pressure difference can be produced not only between the suction port and the discharge port of the expander 103, but also between the suction port and the discharge port of the low-pressure stage compressor 105.
  • the pressure difference of the refrigerant acts on each of the expander 103 and the low-pressure stage compressor 105, and thus self-activation of the power recovery system 109 can be achieved easily.
  • the pressure at the suction port of the low-pressure stage compressor 105 can be increased due to the functions of the bypass flow passage 301 and the bypass valve 302.
  • the controller 117 Upon detecting the activation of the low-pressure stage compressor 105 through the activation detector 119 (step ST34), the controller 117 transmits control signals to the actuator of the expansion valve 110 so that the expansion valve 110 is fully opened (or substantially fully opened) (step ST35). Further, it transmits control signals to the actuator of the bypass valve 302 so that the bypass valve 302 is fully closed.
  • the following effects can be obtained in addition to the effects described in Embodiment 2.
  • the pressure at the suction port of the low-pressure stage compressor 105 can be also increased through the bypass flow passage 301. Accordingly, the drive torque to be imparted to the low-pressure stage compressor 105 increases, and a smoother activation of the power recovery system 109 is enabled.
  • the refrigeration cycle apparatus of the present invention is useful for devices such as water heaters, air conditioners, and dryers.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)
  • Control Of Positive-Displacement Pumps (AREA)
EP11774593A 2010-04-28 2011-04-21 Dispositif à cycle de réfrigération Withdrawn EP2565556A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2010104374 2010-04-28
JP2010104375 2010-04-28
PCT/JP2011/002330 WO2011135805A1 (fr) 2010-04-28 2011-04-21 Dispositif à cycle de réfrigération

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EP2565556A1 true EP2565556A1 (fr) 2013-03-06

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US (1) US20130036757A1 (fr)
EP (1) EP2565556A1 (fr)
JP (1) JP5367164B2 (fr)
CN (1) CN102859295B (fr)
WO (1) WO2011135805A1 (fr)

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JP6342755B2 (ja) * 2014-09-05 2018-06-13 株式会社神戸製鋼所 圧縮装置
ES2807850T3 (es) * 2015-11-05 2021-02-24 Danfoss As Procedimiento de conmutación de capacidad de compresor
CN108131855A (zh) * 2017-12-19 2018-06-08 珠海格力节能环保制冷技术研究中心有限公司 制冷循环系统及具有其的空调器
KR20210082468A (ko) * 2018-10-26 2021-07-05 터보알고르 에스.알.엘. 냉동 장치 및 그 작동 방법
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JP7082098B2 (ja) * 2019-08-27 2022-06-07 ダイキン工業株式会社 熱源ユニット及び冷凍装置
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JP6866910B2 (ja) * 2019-09-30 2021-04-28 ダイキン工業株式会社 熱源ユニット及び冷凍装置
JP6904396B2 (ja) * 2019-09-30 2021-07-14 ダイキン工業株式会社 熱源ユニット及び冷凍装置
WO2021142085A1 (fr) * 2020-01-07 2021-07-15 Johnson Controls Technology Company Système de commande de rapport de volume pour un compresseur
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CN102859295A (zh) 2013-01-02
JP5367164B2 (ja) 2013-12-11
CN102859295B (zh) 2014-08-20
JPWO2011135805A1 (ja) 2013-07-18
US20130036757A1 (en) 2013-02-14
WO2011135805A1 (fr) 2011-11-03

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