JP4192904B2 - Refrigeration cycle equipment - Google Patents

Description

  The present invention relates to a refrigeration cycle apparatus using a supercritical fluid, and particularly to a configuration of a refrigeration cycle apparatus using an expander.

  Hereinafter, it is an example of the freezing apparatus using the conventional expander. The conventional refrigeration apparatus is a refrigeration apparatus using an expander, which enables operation of the refrigeration apparatus under various operating conditions and improves the COP of the refrigeration apparatus.

  Specifically, an expander that generates power by the expansion of the high-pressure refrigerant, a first electric motor that drives the expander, and a first motor that is connected to the expander and is driven by the power generated by them to compress the refrigerant. A first compressor and a variable capacity second compressor that is separately provided to the first compressor and connected to the second motor and is driven by power generated by the second motor to compress the refrigerant. In parallel. Moreover, it has bypass piping which connects the inlet side and outlet side of an expander, and this bypass piping is provided with a bypass valve with variable opening.

  In such a conventional structure, the second compressor that is not connected to the expander is arranged in parallel with the first compressor, and the first compressor connected to the expander alone is insufficient in displacement. Even under the conditions, by operating the second compressor, the shortage of displacement could be compensated, and the refrigeration cycle could be continued under appropriate conditions (see, for example, Patent Document 1).

  As another conventional example, in a refrigeration apparatus in which an expander and a plurality of usage-side heat exchangers are provided in a refrigerant circuit, an appropriate amount of refrigerant can be supplied to each indoor heat exchanger, and the target in each indoor heat exchanger There are things that reliably cool things. In the conventional example, in the refrigerant circuit in which a plurality of indoor heat exchangers are connected in parallel, one indoor control valve is provided corresponding to each indoor heat exchanger, so the opening degree of each indoor control valve is adjusted individually. By doing so, the amount of refrigerant supplied to each room can be appropriately controlled, and the object in each indoor heat exchanger can be reliably cooled.

  In addition, since the gas-liquid separator that separates the low-pressure refrigerant into the liquid refrigerant and the gas refrigerant is provided in the refrigerant circuit, a single-phase liquid refrigerant that is easy to control the flow rate is used instead of the gas-liquid two-phase refrigerant. The refrigerant can be sent to the exchanger, and the refrigerant supply amount to the indoor heat exchanger can be more appropriately controlled. (For example, refer to Patent Document 2).

  In addition, as a conventional example, carbon dioxide is used as a refrigerant, and there are an outdoor unit and a plurality of indoor units, and a plurality of indoor units can be simultaneously operated for cooling or heating, or heating operation and cooling operation are mixed. There is a refrigeration apparatus that can be implemented.

In the conventional refrigeration system, an outdoor unit and a plurality of indoor units are connected by inter-unit piping consisting of a high pressure gas pipe, a low pressure gas pipe, and a liquid pipe, and the plurality of indoor units can be simultaneously operated for cooling or heating. Yes. In addition, since carbon dioxide is used as the refrigerant, the refrigerant vapor discharged from the compressor does not condense in the high-pressure gas pipe, and the inconvenience of liquefying and sleeping in the high-pressure gas pipe like the chlorofluorocarbon refrigerant is eliminated. The This eliminates the need for a bypass pipe between the high-pressure gas pipe and the low-pressure gas pipe, which has been conventionally required for collecting the stagnant refrigerant, and prevents the refrigerant from stagnating in the high-pressure gas pipe without complicating the piping structure. (See, for example, Patent Document 3).

Japanese Patent Laying-Open No. 2004-212006 (Claim 1, FIG. 1) Japanese Patent Laid-Open No. 2003-121015 (column 0021, FIG. 1) Japanese Unexamined Patent Publication No. 2004-226018 (column 0032, FIG. 1)

  In the conventional example, in the refrigeration cycle apparatus using the expander, the first compressor is connected to the first electric motor and the expander, and the structure is complicated, and the recovery power from the expander is preferentially used. There was a problem that control was required. In another conventional example, since the gas refrigerant separated by the gas-liquid separator provided on the outlet side of the expander is returned to the suction portion of the compressor, the compressor connected to the expander can be a gas pipe or a liquid. It is necessary to perform extra pressure work corresponding to the pressure loss when passing through an extended pipe such as a pipe, a pressure reducing means, a heat exchanger, and the like, resulting in an increase in power consumption. In addition, a conventional refrigerant circuit configuration (hereinafter referred to as a three-pipe system) in which carbon dioxide is used, the units are connected by three pipes, a high-pressure gas pipe, a low-pressure gas pipe, and a liquid pipe, and cooling operation and heating operation are performed simultaneously. However, it is difficult to construct a refrigerant circuit for a two-pipe system that consists of only a high-pressure pipe and a low-pressure pipe (hereinafter referred to as a two-pipe system) and that uses the recovery power of the expander in all operation modes. There was a problem. Furthermore, there is a problem that the configuration of the refrigerant circuit that uses the recovery power of the expander is not shown in all the operation modes of the two-stage compression refrigeration cycle.

  The present invention has been made to solve the above-described conventional problems, and in a refrigeration cycle apparatus using an expander, a cooling operation and a heating operation can be performed simultaneously, or by a two-stage compression refrigeration cycle. An object of the present invention is to provide a refrigeration cycle apparatus that can recover expansion power under various operating conditions, such as being able to operate at two different evaporation temperatures (or condensation temperatures).

  The refrigeration cycle apparatus of the present invention is provided in a refrigerant circuit using a natural refrigerant that becomes a supercritical state on the high-pressure side as a refrigerant, and a first compressor that sucks low-pressure refrigerant, discharges high-pressure refrigerant, and circulates the refrigerant. The heat source side heat exchanger that condenses or evaporates the refrigerant circulating in the refrigerant circuit, and the refrigerant discharged from the first compressor to the load side via the heat source side heat exchanger or not via the heat source side heat exchanger A plurality of load-side heat exchangers that can individually select a cooling operation and a heating operation by switching the refrigerant flow so as to circulate, an expander that recovers expansion power of the high-pressure refrigerant, and an expander A gas-liquid separator that separates the expanded refrigerant into a gas-liquid separator, and a second compressor that compresses the refrigerant from the gas-side outlet with the power recovered by the expander. 2 Refrigerant discharged from the compressor is discharged from the first compressor Connect the door is to the high-pressure refrigerant.

  In the refrigeration cycle apparatus according to the present invention, a circuit connecting the high-pressure side and the low-pressure side of the refrigerant circuit includes a third compressor and a second load-side heat exchanger different from the load-side heat exchanger that performs indoor air conditioning. Is provided.

  In this invention, since the gas side outlet part of the gas-liquid separator and the discharge part of the first compressor are connected via the second compressor driven by the recovery power from the expander, the expansion power in various operation modes. Can be recovered, and a refrigeration cycle apparatus capable of reducing power consumption can be provided.

  Moreover, since this invention provided the another heat exchanger for an air conditioning through the 3rd compressor, the apparatus used for the efficient wide use is obtained.

Embodiment 1 FIG.
Hereinafter, the refrigeration cycle apparatus according to Embodiment 1 of the present invention will be described. FIG. 1 is a schematic diagram showing a refrigeration cycle apparatus according to Embodiment 1 of the present invention. In the figure, the refrigeration cycle apparatus according to the present embodiment connects the outdoor unit 100 that is a heat source side unit, the branch unit 300, the indoor units 200a, 200b, and 200c that are load side units, and the outdoor unit 100 and the branch unit 300. The high-pressure pipe 52 and the low-pressure pipe 51 are pipes to be connected. Therefore, the refrigeration cycle apparatus of the present invention is a two-pipe system in which the indoor units 200a, 200b, and 200c can individually select a cooling operation and a heating operation. For example, carbon dioxide that is in a supercritical state at a critical temperature (about 31 ° C.) or higher is enclosed as a refrigerant.

  In the outdoor unit 100, there are a first compressor 1 for compressing the refrigerant gas, a four-way valve 2 which is a first refrigerant flow switching means for cooling operation and heating operation, and outdoor heat exchange which is a heat source side heat exchanger. 3, a blower (not shown) for forcing the outside air to the outer surface of the outdoor heat exchanger 3, and further for supplying high pressure gas to the high pressure pipe 52 and low pressure gas to the low pressure pipe 51 in both the cooling operation and the heating operation. Check valves 21a to 21d are accommodated. In the branch unit 300, the expansion degree 4 provided at the liquid side outlet of the expander 4, the gas-liquid separator 5, and the gas-liquid separator 5 that depressurizes the refrigerant to form wet steam in a two-phase state can be changed. 2 Electronic expansion valve 12 as decompression means, second compressor 9 connected coaxially with expander 4 and driven by power recovered by expander 4, discharge gas of second compressor and suction part of first compressor An internal heat exchanger 22 that exchanges heat, a suction pipe 13 that guides the gas refrigerant separated by the gas-liquid separator 5 to the suction side of the second compressor 9, and a first compression of the gas refrigerant separated by the gas-liquid separator 5 The first bypass pipe 14 that leads to the suction side of the machine 1, the electronic expansion valve 10 that is the third pressure reducing means provided in the first bypass pipe and that can change the opening degree, and there are few load-side units that perform the cooling operation. A second bypass pipe 19 for bypassing the refrigerant to the suction side of the first compressor 1; An electronic expansion valve 20 that is a pressure-reducing means that can be changed in opening degree, an on-off valve 30, 31, 32, 33, 34, 35, 42, 43 that is a switching means between cooling operation and heating operation, and a check Valves 36, 37, 38, 39, 40, 41 and piping for connecting them are incorporated.

  The first port 2a of the four-way valve 2 is the discharge side of the compressor 1, the second port 2b is one end of the outdoor heat exchanger 3, the third port 2c is the suction side of the compressor 1, and the fourth port 2d is reversed. They are connected to the stop valves 21a and 21d, respectively.

  The indoor units 200a, 200b, and 200c include an electronic unit that is a first decompression unit that adjusts refrigerant distribution to the indoor heat exchangers 7a, 7b, and 7c and the indoor heat exchangers 7a, 7b, and 7c that are load-side heat exchangers. The expansion valves 6a, 6b, 6c, a blower (not shown) for forcibly blowing room air to the outer surfaces of the indoor heat exchangers 7a, 7b, 7c, and piping for connecting them are incorporated. One end of the indoor heat exchangers 7a, 7b, 7c is connected to the branch unit 300, and the other end is connected to the branch unit via the electronic expansion valves 6a, 6b, 6c. In the present embodiment, three indoor units 200a, 200b, and 200c are provided, but two or less indoor units or four or more indoor units may be provided.

  The operation of the refrigeration cycle apparatus configured as described above will be described. First, the case where all indoor units perform cooling operation will be described with reference to FIGS. 1 and 2. FIG. 2 shows on the Ph diagram the refrigerant states at symbols A to K shown in the refrigerant circuit of FIG. In the cooling only operation, the four-way valve 2 in the outdoor unit 100 is set so that the first port 2a and the second port 2b communicate with each other and the third port 2c and the fourth port 2d communicate with each other (solid line in FIG. 1). . Further, the solenoid valves 31, 33, 35, 43 are closed, the other solenoid valves are opened, and the electronic expansion valve 20 in the second bypass pipe 19 is fully closed. Further, the check valves 21c, 21d, 36, 38, 40 are closed.

  At this time, the high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the first port 2a of the four-way valve 2 through the second port 2b (state B), and the air that is the medium to be heated in the outdoor heat exchanger 3 (State C) and flows into the expander 4 through the check valve 21b, the high pressure pipe 52, and the electromagnetic valve 42. The liquid refrigerant flowing into the expander 4 becomes a low-pressure and low-temperature gas-liquid two-phase refrigerant (state D) and flows into the gas-liquid separator 5. The liquid refrigerant (state E) separated by the gas-liquid separator 5 passes through the electronic expansion valve 12 and the check valves 37, 39, 41 and flows into the indoor units 200a, 200b, 200c.

  The liquid refrigerant that has flowed into the indoor units 200a, 200b, and 200c is distributed substantially uniformly to the indoor heat exchangers 7a, 7b, and 7c by the electronic expansion valves 6a, 6b, and 6c. This liquid refrigerant absorbs heat from indoor air (not shown) in the indoor heat exchangers 7a, 7b, and 7c, and evaporates itself. The low-temperature and low-pressure gas refrigerant passes through the solenoid valves 30, 32, and 34 (state G), and the remaining gas refrigerant sucked by the second compressor 9 among the gas refrigerant separated by the gas-liquid separator 5. (State H) merges (state I), passes through the internal heat exchanger 22, the low pressure pipe 51, the check valve 21 a, the fourth port 2 d of the four-way valve 2, the third port 2 c, and the first compressor 1. Return to the suction side (state A). At this time, the indoor air sent into the indoor heat exchangers 7a, 7b, and 7c by an indoor blower (not shown) is cooled by the low-temperature and low-pressure liquid refrigerant and blown into the room to cool the room.

  On the other hand, the gas refrigerant (state F) separated by the gas-liquid separator 5 passes through the suction pipe 13 and is compressed by the second compressor 9 up to the outlet pressure of the high-pressure pipe 52 (state J). The gas refrigerant discharged from the second compressor 9 exchanges heat with the suction refrigerant of the first compressor 1 in the internal heat exchanger 22 (state K), and then merges with the liquid refrigerant flowing in from the high-pressure pipe 52.

  In the refrigeration cycle on the Ph diagram shown in FIG. 2, the discharge pressure of the second compressor 9 is lower than the discharge pressure of the first compressor 1 by ΔPd, and the suction pressure of the second compressor is It rises by ΔPs from the suction pressure of one compressor. This is due to the following reason. That is, when the refrigerant compressed by the first compressor 1 passes through the four-way valve 2, the outdoor heat exchanger 3, the check valve 21 b, and the high-pressure pipe 52, a pressure loss is generated and the discharge pressure is reduced. After being separated by the separator 5, the electronic expansion valve 12, the check valves 37, 39, 41, the electronic expansion valves 6a, 6b, 6c, the indoor heat exchangers 7a, 7b, 7c, the internal heat exchanger 22, and the low pressure, respectively. This is because a pressure loss occurs when passing through the pipe 51, the check valve 21a, and the four-way valve 2, and the suction pressure is reduced. Therefore, the second compressor 9 does not need to perform pressure increasing work corresponding to the pressure loss, and the input power of the expander can be effectively utilized by reducing the 9 inputs of the second compressor.

  Next, the case where all the indoor units perform the heating operation will be described with reference to FIGS. 3 and 4. FIG. 4 shows on the Ph diagram the refrigerant states at symbols A to J shown in the refrigerant circuit of FIG. In this case, the four-way valve 2 inside the outdoor unit 100 is set so that the first port 2a and the fourth port 2d communicate with each other and the second port 2b and the third port 2c communicate with each other (solid line in FIG. 3). Further, the electromagnetic valves 30, 32, 34, 42 are closed, the other electromagnetic valves are opened, and the electronic expansion valve 20 is set to an appropriate opening degree. Further, the check valves 21a, 21b, 37, 39, 41 are closed.

  At this time, the refrigerant that has been compressed by the compressor 1 and is in a supercritical state of high temperature and pressure flows from the first port 2a of the four-way valve 2 to the branch unit 300 through the fourth port 2d, the check valve 21d, and the high pressure pipe 52. . Here, the high-temperature and high-pressure refrigerant passes through the electromagnetic valves 31, 33, and 35 and flows into the indoor units 200a, 200b, and 200c, respectively. Here, heat is released to indoor air (not shown) to heat the room, and the temperature itself decreases. This medium-temperature and high-pressure refrigerant passes through the electronic expansion valves 6a, 6b and 6c (state C), and flows into the expander 4 through the check valves 36, 38 and 40. The refrigerant decompressed by the expander 4 flows into the gas-liquid separator 5 (state D). The liquid refrigerant (state E) separated by the gas-liquid separator 5 is decompressed by the electronic expansion valve 20 (state G), passes through the internal heat exchanger 22, and then passes through the low-pressure pipe 51 and the check valve 21c. It flows into the heat exchanger 3. On the other hand, the gas refrigerant (state F) separated by the gas-liquid separator 5 passes through the suction pipe 13 and is compressed by the second compressor 9 up to the outlet pressure of the high-pressure pipe 52 (state J). The discharge gas of the second compressor 9 and the discharge gas of the first compressor merge to be in the state I. At this time, the refrigerant does not flow to the internal heat exchanger 22 due to the pipe resistance.

  The low-temperature and low-pressure liquid refrigerant (state H) flowing into the outdoor heat exchanger 3 absorbs heat from the outside air sent by an outdoor fan (not shown) and evaporates itself. The evaporated gas refrigerant returns from the second port 2b of the four-way valve 2 to the suction side of the first compressor 1 through the third port 2c (state A).

  In the refrigeration cycle on the Ph diagram shown in FIG. 4, the discharge pressure of the second compressor is lower than the discharge pressure of the first compressor by ΔPd, and the suction pressure of the second compressor is the first compression. Increases by ΔPs from the suction pressure of the machine. This is due to the following reason. That is, the refrigerant compressed by the first compressor causes a pressure loss when passing through the four-way valve 2, the check valve 21 d, and the high-pressure pipe 52, and the discharge pressure is reduced. On the other hand, the refrigerant is separated by the gas-liquid separator 5. When the liquid refrigerant passes through the electronic expansion valve 20, the internal heat exchanger 22, the low pressure pipe 51, the check valve 21 c, the outdoor heat exchanger 3, and the four-way valve 2, a pressure loss occurs and the suction pressure decreases. Because. Therefore, the second compressor does not need to perform pressure increasing work corresponding to the pressure loss, and the input power of the second compressor can be reduced and the recovered power of the expander can be used effectively.

  Next, the cooling main operation in which the indoor units 200b and 200c are the cooling operation and the 200a is the heating operation will be described with reference to FIGS. FIG. 6 shows the refrigerant state of symbols A to L shown in the refrigerant circuit of FIG. 5 on the Ph diagram. In this case, the four-way valve 2 inside the outdoor unit 100 is set so that the first port 2a and the second port 2b communicate with each other and the third port 2c and the fourth port 2d communicate with each other (solid line in FIG. 3). Further, the electromagnetic valves 30, 33, 35, 42 are closed, the other electromagnetic valves are opened, and the electronic expansion valve 20 is fully closed. Further, the check valves 21c, 21d, 36, 38, 41 are closed.

  At this time, the high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the first port 2a of the four-way valve 2 through the second port 2b (state B), and the air that is the medium to be heated in the outdoor heat exchanger 3 Radiates to a certain degree to become a medium-temperature and high-pressure refrigerant (state C), and flows into the indoor unit 200a through the check valve 21b, the high-pressure pipe 52, and the electromagnetic valve 31. Here, the room air is further radiated to the indoor air (not shown) to heat the room, and the temperature itself decreases. This low-temperature and high-pressure refrigerant passes through the electronic expansion valve 6a (state K) and flows into the expander 4 through the check valve 40. The low-temperature and high-pressure refrigerant flowing into the expander 4 becomes a low-temperature and low-pressure gas-liquid two-phase refrigerant (state D) and flows into the gas-liquid separator 5. The liquid refrigerant (state E) separated by the gas-liquid separator 5 passes through the electronic expansion valve 12 and the check valves 37 and 39 and flows into the indoor units 200b and 200c.

  The liquid refrigerant that has flowed into the indoor units 200b and 200c is uniformly distributed to the indoor heat exchangers 7b and 7c by the electronic expansion valves 6b and 6c. This liquid refrigerant absorbs heat from indoor air (not shown) in the indoor heat exchangers 7b and 7c, and evaporates itself. This low-temperature and low-pressure gas refrigerant passes through the solenoid valves 32 and 34 (state G), and among the gas refrigerant separated by the gas-liquid separator 5, the remaining gas refrigerant sucked by the second compressor 9 (state H) (state I), the low-pressure pipe 51, the check valve 21a, the four-way valve 2 through the fourth port 2d through the third port 2c through the internal heat exchanger 22, and the suction side of the first compressor 1 Return to (State A). At this time, the indoor air sent to the indoor heat exchangers 7b and 7c by an indoor blower (not shown) is cooled by the low-temperature and low-pressure liquid refrigerant and blown into the room to cool the room.

  On the other hand, the gas refrigerant (state F) separated by the gas-liquid separator 5 passes through the suction pipe 13 and is compressed by the second compressor 9 up to the outlet pressure of the high-pressure pipe 52 (state J). The gas refrigerant discharged from the second compressor 9 joins the medium-temperature and high-pressure refrigerant that has passed through the electromagnetic valve 43 and has flowed from the high-pressure pipe 52 into the branch unit 300 (state L). At this time, the refrigerant does not flow to the internal heat exchanger 22 due to the pipe resistance.

  In the refrigeration cycle on the Ph diagram shown in FIG. 6, the discharge pressure of the second compressor is lower than the discharge pressure of the first compressor by ΔPd, and the suction pressure of the second compressor is the first compression. Increases by ΔPs from the suction pressure of the machine. This is due to the following reason. That is, when the refrigerant compressed by the first compressor passes through the four-way valve 2, the outdoor heat exchanger 3, the check valve 21 b, and the high-pressure pipe 52, a pressure loss occurs and the discharge pressure decreases, and the gas-liquid separation The liquid refrigerant separated in the vessel 5 is the electronic expansion valve 12, check valves 37 and 39, electronic expansion valves 6b and 6c, indoor heat exchangers 7b and 7c, electromagnetic valves 32 and 34, internal heat exchanger 22, and low pressure. This is because a pressure loss occurs when passing through the pipe 51, the check valve 21a, and the four-way valve 2, and the suction pressure is reduced. Therefore, the second compressor does not need to perform pressure increasing work corresponding to the pressure loss, and the input power of the second compressor can be reduced and the recovered power of the expander can be used effectively.

  Next, a heating main operation in which the indoor units 200a and 200b are in the heating operation and the 200c is in the cooling operation will be described with reference to FIGS. FIG. 8 shows the refrigerant state at symbols A to K shown in the refrigerant circuit of FIG. 7 on the Ph diagram. In this case, the four-way valve 2 inside the outdoor unit 100 is set so that the first port 2a and the fourth port 2d communicate with each other and the second port 2b and the third port 2c communicate with each other (solid line in FIG. 7). The electromagnetic valves 30, 32, 35, and 42 are closed, the other electromagnetic valves are opened, and the electronic expansion valve 20 is set to a certain opening. Further, the check valves 21a, 21b, 36, 39, 41 are closed.

  At this time, the high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes from the first port 2a to the fourth port 2d of the four-way valve 2 (state B), passes through the check valve 21d and the high-pressure pipe 52, and is branched. Flows into 300. Here, the high-temperature and high-pressure refrigerant passes through the electromagnetic valves 31 and 33 and flows into the indoor units 200a and 200b, respectively. Here, heat is released to indoor air (not shown) to heat the room, and the temperature itself decreases. This medium-temperature and high-pressure refrigerant passes through the electronic expansion valves 6a and 6b (state C) and flows into the expander 4 through the check valves 38 and 40. The refrigerant decompressed by the expander 4 flows into the gas-liquid separator 5 (state D). A part of the liquid refrigerant (state E) separated by the gas-liquid separator 5 is decompressed by the electronic expansion valve 20 (state G). The other part flows through the electronic expansion valve 12 into the indoor unit 200c.

  The liquid refrigerant flowing into the indoor unit 200c absorbs heat from indoor air (not shown) in the indoor heat exchanger 7c and evaporates itself. This low-temperature and low-pressure gas refrigerant passes through the electromagnetic valve 34 (state H), and in addition to the gas-liquid two-phase refrigerant decompressed by the electronic expansion valve 20, the second compressor among the gas refrigerant separated by the gas-liquid separator 5 9 merges with the remaining gas refrigerant sucked in 9, passes through the internal heat exchanger 22, passes through the low pressure pipe 51 and the check valve 21 c, and flows into the outdoor heat exchanger 3 (state K).

  The low-temperature and low-pressure liquid refrigerant (state K) flowing into the outdoor heat exchanger 3 absorbs heat from the outside air sent by an outdoor fan (not shown) and evaporates itself. The evaporated gas refrigerant returns from the second port 2b of the four-way valve 2 to the suction side of the first compressor 1 through the third port 2c (state A).

  On the other hand, the gas refrigerant (state F) separated by the gas-liquid separator 5 passes through the suction pipe 13 and is compressed by the second compressor 9 up to the outlet pressure of the high-pressure pipe 52 (state J). The gas refrigerant discharged from the second compressor 9 merges with the high-temperature and high-pressure refrigerant that has passed through the electromagnetic valve 43 and has flowed into the branch unit 300 from the high-pressure pipe 52. At this time, the refrigerant does not flow to the internal heat exchanger 22 due to the pipe resistance.

  In the refrigeration cycle on the Ph diagram shown in FIG. 8, the discharge pressure of the second compressor is reduced by ΔPd from the discharge pressure of the first compressor, and the suction pressure of the second compressor is the first compression. Increases by ΔPs from the suction pressure of the machine. This is due to the following reason. That is, the refrigerant compressed by the first compressor is separated by the gas-liquid separator 5 due to a pressure loss caused by passing through the four-way valve 2, the check valve 21 d, and the high-pressure pipe 52, thereby reducing the discharge pressure. The liquid refrigerant includes the electronic expansion valve 12, the check valve 37, the electronic expansion valve 6c, the indoor heat exchanger 7c, the electromagnetic valve 34, the internal heat exchanger 22, the low pressure pipe 51, the check valve 21c, the outdoor heat exchanger 3, This is because a pressure loss occurs when passing through the four-way valve 2 to reduce the suction pressure. Therefore, the second compressor does not need to perform pressure increasing work corresponding to the pressure loss, and the input power of the second compressor can be reduced and the recovered power of the expander can be used effectively.

Next, the indoor unit 200a, 200b, 200c is a Ph diagram during heating operation, and the recovery power in the expander 4, the amount of gas generated in the gas-liquid separator 5, The compression work in the compressor 9 is compared. If the refrigerant flow rate passing through the expander 4 is Gr and the enthalpy difference at the inlet / outlet of the expander 4 is ΔH1, the recovered power We in the expander 4 is expressed by the following equation (1).
We = Gr × ΔH1 (1)
Similarly, the compression work W2 in the second compressor is expressed by the following equation (2), where the refrigerant flow rate is Gr2 and the enthalpy difference in the second compressor 9 is ΔH2.
W2 = Gr2 × ΔH2 (2)
Since the recovered power is equal to the compression work in the second compressor 9 (We = W2), Equation (3) is obtained from Equations (1) and (2).
Gr2 = Gr × (ΔH1 / ΔH2) (3)
Further, the flow rate Gs of the gas separated by the gas-liquid separator 5 is generated by the ratio of the enthalpy difference ΔH3 between D and E to the enthalpy difference ΔH0 between FE, that is, the dryness X (ΔH3 / ΔH0). From this, it is expressed by equation (4).
Gs = Gr × (ΔH3 / ΔH0) (4)
Here, ΔH1 / ΔH2 in the equation (3) is a ratio of the enthalpy difference of the expander to the enthalpy difference of the compressor, and is generally about 0 to 0.2. Moreover, (DELTA) H3 / (DELTA) H0 in (4) Formula is the dryness X, and when a refrigerant | coolant is CO2, generally it will be about 0.2-0.6. Therefore, Gr2 <Gs from the equations (3) and (4), and the refrigerant flow rate Gr2 required by the second compressor 9 can be sufficiently supplied by the gas-liquid separator 5 and the difference in refrigerant flow rate (Gs− Gr2) will be bypassed through the electronic expansion valve 10.

On the other hand, the expander 4 and the second compressor 9 are connected coaxially, and the second compressor 9 rotates at the same rotational speed as the expander 4. As an example, both the expander 4 and the second compressor 9 are of a scroll type that is a positive displacement fluid machine with a constant displacement volume, and the displacement volume ratio is ε (= second compressor displacement volume / expansion chamber displacement volume). = Vc / Ve), and the suction densities of the expander 4 and the second compressor 9 are ρe and ρc, respectively, the equation (5) can be obtained from the condition of constant rotation speed.
Gr2 = Gr × ε × (ρc / ρe) (5)
From the expressions (3) and (5), the expression (6) is obtained.
ρc / ρe = (ΔH1 / ΔH2) / ε (6)
From the above, the expression (6) is established so that any one of the suction density ρc and the enthalpy difference ΔH2 of the second compressor 9 and the suction density ρe of the expander 9 and the inlet / outlet enthalpy difference ΔH1 and ε (= Vc / Ve) is satisfied. Need to control. In the conventional example, an example in which a bypass valve is provided in the expander 4 and the flow rate passing through the expander 4 is controlled is shown. This corresponds to the adjustment of ε.

  In the present embodiment, when an imbalance occurs between the refrigerant flow rate Gs supplied from the gas-liquid separator 5 and the refrigerant flow rate Gr2 of the second compressor 9 due to environmental conditions such as the outside air temperature, the room temperature, and the air conditioning load, The difference (Gs−Gr2) is bypassed by the electronic expansion valve 10. That is, the opening degree of the electronic expansion valve 10 is adjusted so that the difference refrigerant flow rate flows. Similarly, when an imbalance occurs between the recovery power of the expander 4 and the compression power of the second compressor 9, the opening degree of the electronic expansion valve 12 is appropriately controlled so that the expression (6) is satisfied. That is, when the right side of the equation (6) is large (ρc / ρe <(ΔH1 / ΔH2) / ε), the opening of the electronic expansion valve 12 is decreased, and the expander outlet portion and the evaporator inlet portion shown in FIG. Is increased to increase ρc. At this time, ΔH1 / ΔH2 on the right side of equation (6) also changes at the same time, but both the denominator and numerator become smaller, so the change in ΔH1 / ΔH2 is small, and the operation is performed so that equation (6) is established in the practical range. On the other hand, when the left side of the equation (6) is large (ρc / ρe> (ΔH1 / ΔH2) / ε), the opening degree of the electronic expansion valve 12 is increased, and the expander outlet portion and the evaporator inlet portion shown in FIG. Ρc is decreased by reducing the pressure difference ΔPe. At this time, ΔH1 / ΔH2 on the right side of equation (6) also changes at the same time, but both the denominator and the numerator increase, so that the change in ΔH1 / ΔH2 is small, and the operation is performed so that equation (6) is established.

  In the present embodiment, the opening degree of the electronic expansion valve 12 is adjusted to establish the expression (6). However, the present invention is not limited to this, and the electronic expansion valve in the indoor units 200a, 200b, and 200c is shown. You may comprise so that (6) Formula may be materialized by adjusting the opening degree of 6a, 6b, 6c. Further, an electronic expansion valve that is a fourth pressure reducing means may be provided in the suction pipe 13 of the second compressor, and the opening degree of the electronic expansion valve may be changed. In addition, as an example of an air conditioner using an air heat exchanger as a heat source side heat exchanger and a load side heat exchanger, a double tube type or plate using brine or water as a cooling medium or a heating medium You may make it comprise a chiller or a water heater using liquid-liquid heat exchangers, such as a formula.

  As described above, in the present embodiment, the load side unit is a refrigeration cycle apparatus capable of individually selecting the cooling operation and the heating operation, and all of the cooling only operation, the heating only operation, the cooling main operation, and the heating main operation are performed. The expansion power can be recovered using the expander in the operation mode. Further, since the second compressor 9 connected to the expander is not provided with an electric motor, the recovery power of the expander can be used with a simple configuration and control. At this time, the second compressor driven by the recovery power of the expander is a boosting work corresponding to a pressure loss when passing through an extension pipe such as a high-pressure pipe or a low-pressure pipe, an electronic expansion valve, a heat exchanger, or a four-way valve. The input of the second compressor 9, that is, the power consumption is reduced. Furthermore, by controlling the opening degree of the electronic expansion valve 12, it is possible to provide a refrigeration cycle apparatus that can use recovered power under any operating conditions. In the above description, the case where there is one outdoor unit 100 is taken as an example, but a plurality of outdoor units may be provided. Also, it is possible to provide a configuration in which the indoor units that are load-side units are provided separately, or a plurality of heat exchangers and electronic expansion valves are provided in one indoor unit. Furthermore, it is natural that the branch unit component may be housed in an outdoor unit or an indoor unit and connected by piping. In addition, each equipment and device for convenience has been described separately for each unit. However, it has a refrigeration cycle structure in which necessary equipment is arranged at a required place without a unit configuration and connected with a high-pressure pipe and a low-pressure pipe. Of course it is good.

Embodiment 2. FIG.
Hereinafter, a refrigeration cycle apparatus according to Embodiment 2 of the present invention will be described. FIG. 10 is a schematic diagram showing a refrigeration cycle apparatus according to Embodiment 2 of the present invention. In the figure, the refrigeration cycle apparatus according to the present embodiment is a two-stage compression refrigeration cycle apparatus that operates at two different evaporation temperatures during cooling operation and operates at two different condensation temperatures during heating operation. During cooling operation, the latent heat load is processed on the low stage side, and the sensible heat load is processed on the high stage side. During heating operation, medium temperature air is blown out on the lower stage side, and hot air is blown out on the higher stage side. The refrigeration cycle apparatus includes an outdoor unit 100 that is a heat source side unit, indoors 200a, 200b, and 200c that are first load side units, a second load side unit 300, and a second load side unit 300 that connects the outdoor unit 100 and the second load side unit 300. The first liquid pipe 54, the first gas pipe 53, the second load side unit 300, and the second liquid pipe 56 and the second gas pipe 55 that connect the indoor units 200a, 200b, 200c are configured. For example, carbon dioxide that is in a supercritical state at a critical temperature (about 31 ° C.) or higher is enclosed as a refrigerant. Note that parts and components having the same reference numerals as those described in FIGS. 1 to 9 have the same configurations and operations as those described in the first embodiment. The operation of the entire refrigeration cycle is the same as that in the first embodiment.

  In the outdoor unit 100, there are a first compressor 1 that becomes a high stage side compressor during cooling operation, a four-way valve 2 that is a first refrigerant flow switching means between cooling operation and heating operation, and a heat source side heat exchanger. The outdoor heat exchanger 3 and a blower (not shown) for forcing the outside air to the outer surface of the outdoor heat exchanger 3 are housed. In the second load side unit 300, a third compressor 63 that is a low-stage side compressor during cooling operation, a four-way valve 61 that is a second flow path switching means, a four-way valve 60 that is a third flow path switching means, The second load-side heat exchanger 64, the electronic expansion valve 65 as the second decompression means, the expander 4, the gas-liquid separator 5, and the liquid of the gas-liquid separator 5 by depressurizing the refrigerant into a two-phase wet steam An electronic expansion valve 12, which is a third decompression means capable of changing the opening provided at the side outlet, a second compressor 9 connected coaxially with the expander 4 and driven by power recovered by the expander 4, during cooling operation An internal heat exchanger 22 for exchanging heat between the discharge gas of the second compressor 9 and the suction portion of the first compressor, and a suction pipe for guiding the gas refrigerant separated by the gas-liquid separator 5 to the suction side of the second compressor 9 13. First bypass pipes 14, 67 for guiding the gas refrigerant separated by the gas-liquid separator 5 to the low pressure side, the first bypass Electronic expansion valves 10,68 is a fourth pressure reducing means capable opening degree variation provided in the piping, the on-off valve 66, and piping for connecting them is incorporated.

  The first port 2a of the four-way valve 2 is the discharge side of the compressor 1, the second port 2b is one end of the outdoor heat exchanger 3, the third port 2c is the suction side of the compressor 1, and the fourth port 2d is a low pressure. Each is connected to a pipe 51. The first port 60a of the four-way valve 60 is the outlet side of the first liquid tube 54, the second port 60b is the inlet side of the expander 4, the third port 60c is the inlet side of the second liquid tube 56, and the fourth port. 60 d is connected to the electronic expansion valve 12. The first port 61a of the four-way valve 61 is the discharge side of the third compressor 63, the second port 61b is a pipe connected between the internal heat exchanger 22 and the second gas pipe 55, and the third port 61c is the second port 61c. The suction side of the three compressor 63 and the fourth port 60d are connected to one end of the second load side heat exchanger 64, respectively.

  The indoor units 200a, 200b, and 200c include indoor heat exchangers 7a, 7b, and 7c that are first load-side heat exchangers, and an electronic expansion valve 6a that is first decompression means for adjusting refrigerant distribution to the indoor heat exchanger. 6b, 6c, a blower (not shown) for forcibly blowing room air to the outer surfaces of the indoor heat exchangers 7a, 7b, 7c and a pipe for connecting them are incorporated. One end of the indoor heat exchangers 7a, 7b, and 7c is connected to the second load side unit 300, and the other end is connected to the second load side unit via the electronic expansion valves 6a, 6b, and 6c. In the present embodiment, three indoor units 200a, 200b, and 200c are provided, but two or less indoor units or four or more indoor units may be provided.

  The operation of the refrigeration cycle apparatus configured as described above will be described. First, the case where the cooling operation is performed will be described with reference to FIGS. 10 and 11. FIG. 11 shows the refrigerant state at symbols A to O shown in the refrigerant circuit of FIG. 10 on the Ph diagram. In the cooling operation, the four-way valve 2 inside the outdoor unit 100 is set so that the first port 2a and the second port 2b communicate with each other, and the third port 2c and the fourth port 2d communicate with each other. The four-way valve 60 is set so that the first port 60a and the second port 60b communicate with each other, and the third port 60c and the fourth port 60d communicate with each other. The four-way valve 61 communicates with the first port 61a and the second port 61b. The third port 61c and the fourth port 61d are set to communicate with each other. The electromagnetic valve 66 is closed, the electronic expansion valve 68 is fully closed, and the electronic expansion valve 67 is set to an appropriate opening degree.

  At this time, the high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the first port 2a of the four-way valve 2 through the second port 2b (state B), and the air that is the medium to be heated in the outdoor heat exchanger 3 (State C) and flows into the second load side unit 300 through the first liquid pipe 54. The refrigerant flowing into the second load side unit 300 merges with the liquid refrigerant from the internal heat exchanger 22 (state O), passes through the first port 60a of the four-way valve 60 through the second port 60b, and enters the expander 4. Inflow. The liquid refrigerant flowing into the expander 4 becomes a low-pressure and low-temperature gas-liquid two-phase refrigerant (state D) and flows into the gas-liquid separator 5. The liquid refrigerant (state E) separated by the gas-liquid separator 5 passes through the electronic expansion valve 12 and the fourth port 60d of the four-way valve 60 through the third port 60c (state H), and a part thereof is the second liquid pipe 56. And flows into the indoor units 200a, 200b, 200c.

  The liquid refrigerant flowing into the indoor units 200a, 200b, 200c is uniformly distributed to the indoor heat exchangers 7a, 7b, 7c by the electronic expansion valves 6a, 6b, 6c. This liquid refrigerant absorbs heat from indoor air (not shown) in the indoor heat exchangers 7a, 7b, and 7c, and evaporates itself. This low-temperature and low-pressure gas refrigerant (state I) merges with the refrigerant (state L) discharged from the third compressor 63 in the second load-side unit 300 after passing through the second gas pipe 55 to generate internal heat. It returns to the suction side of the first compressor 1 through the first gas pipe 53 and the fourth port 2d of the four-way valve 2 through the third port 2c through the exchanger 22 (state A). At this time, the indoor air sent into the indoor heat exchangers 7a, 7b, and 7c by an indoor blower (not shown) is cooled by the low-temperature and low-pressure liquid refrigerant and blown into the room to cool the room.

  At this time, the gas refrigerant (state F) separated by the gas-liquid separator 5 passes through the suction pipe 13 and is compressed by the second compressor 9 up to the outlet pressure of the first liquid pipe 54 (state G). The gas refrigerant discharged from the second compressor 9 exchanges heat with the intake refrigerant of the first compressor 1 in the internal heat exchanger 22 (state N), and then merges with the refrigerant flowing in from the first liquid pipe 54 ( State O).

  In addition, in the second load side unit 300, the refrigerant (state J) in which other part of the refrigerant not supplied to the second liquid pipe 56 flows from the electronic expansion valve 65 evaporates in the second load side heat exchanger 64. , Mainly dealing with indoor latent heat load. The evaporated gas refrigerant (state K) is compressed by the third compressor 63 from the fourth port 61d of the four-way valve 61 through the third port 61c (state L). The compressed refrigerant merges with the refrigerant that has flowed through the second gas pipe 55 (state M).

  In the refrigeration cycle on the Ph diagram shown in FIG. 11, the discharge pressure of the second compressor is lower than the discharge pressure of the first compressor by ΔPd, and the suction pressure of the second compressor is the first compression. Increases by ΔPs from the suction pressure of the machine. This is due to the following reason. That is, when the refrigerant compressed by the first compressor passes through the four-way valve 2, the outdoor heat exchanger 3, and the first liquid pipe 54, a pressure loss occurs and the discharge pressure decreases, and the gas-liquid separator 5 The separated liquid refrigerant includes the electronic expansion valve 12, the four-way valve 60, the second liquid pipe 56, the electronic expansion valves 6a, 6b, 6c, the indoor heat exchangers 7a, 7b, 7c, the second gas pipe 55, and the internal heat exchange. This is because a pressure loss occurs when passing through the vessel 22, the first gas pipe 53, and the four-way valve 2, and the suction pressure decreases. Therefore, the second compressor does not need to perform pressure increasing work corresponding to the pressure loss, and the input power of the second compressor can be reduced and the recovered power of the expander can be used effectively.

  Next, the heating operation will be described with reference to FIGS. FIG. 13 shows on the Ph diagram the refrigerant states at symbols A to H and J to M shown in the refrigerant circuit of FIG. In this case, the four-way valve 2 inside the outdoor unit 100 is set so that the first port 2a and the fourth port 2d communicate with each other, and the second port 2b and the third port 2c communicate with each other. The four-way valve 60 is set so that the first port 60a and the fourth port 60d communicate with each other, and the second port 60b and the third port 60c communicate with each other. The four-way valve 61 communicates with the first port 61a and the fourth port 61d. The second port 61b and the third port 61c are set to communicate with each other. The electromagnetic valve 66 is opened, the electronic expansion valve 10 is fully closed, and the electronic expansion valve 68 is set to an appropriate opening degree.

  At this time, the refrigerant that has been compressed by the compressor 1 and is in a supercritical state of high temperature and pressure flows from the first port 2a of the four-way valve 2 to the second load side unit 300 through the fourth port 2d and the first gas pipe 53. . The high-temperature and high-pressure refrigerant (state B) flowing into the second load side unit 300 passes through the internal heat exchanger 22 (state M), and the refrigerant flow rate according to the heating load of the indoor units 200a, 200b, and 200c is the second. The gas is supplied to the gas pipe 55 and flows into the indoor units 200a, 200b, and 200c. Here, heat is released to indoor air (not shown) to heat the room, and the temperature itself decreases. The medium-temperature and high-pressure refrigerant passes through the electronic expansion valves 6a, 6b, and 6c (state C), and flows into the second load side unit 300 through the second liquid pipe 56. The refrigerant that has flowed into the second load side unit 300 flows into the expander 4 via the third port 60c and the second port 60b of the four-way valve 60. The refrigerant decompressed by the expander 4 flows into the gas-liquid separator 5 (state D). The liquid refrigerant (state E) separated by the gas-liquid separator 5 is depressurized by the electronic expansion valve 12 and passes through the fourth port 60d, the first port 60a, and the first liquid pipe 54 of the four-way valve 60, and the outdoor heat exchanger. 3 (state H).

  The low-temperature and low-pressure liquid refrigerant (state H) flowing into the outdoor heat exchanger 3 absorbs heat from the outside air sent by an outdoor fan (not shown) and evaporates itself. The evaporated gas refrigerant returns from the second port 2b of the four-way valve 2 to the suction side of the first compressor 1 through the third port 2c (state A). On the other hand, the gas refrigerant (state F) separated by the gas-liquid separator 5 is compressed by the second compressor 9 up to the outlet pressure (state M) of the internal heat exchanger 22 (state G). The discharge gas of the second compressor 9 passes through the electromagnetic valve 66, merges with the discharge gas of the first compressor, and flows into the four-way valve 61. The refrigerant that has passed through the second port 61b and the third port 61c of the four-way valve 61 (state L) is further compressed by the third compressor 63, and passes through the first port 61a and the fourth port 61d of the four-way valve 61 to be second. It flows into the load side heat exchanger 64 (state K). The refrigerant radiated by the second load-side heat exchanger 64 (state J) is decompressed by the electronic expansion valve 65 and merges with the refrigerant that has flowed into the second load-side unit 300 from the second liquid pipe 56.

  In the refrigeration cycle on the Ph diagram shown in FIG. 13, the discharge pressure of the second compressor is lower than the discharge pressure of the first compressor by ΔPd, and the suction pressure of the second compressor is the first compression. Increases by ΔPs from the suction pressure of the machine. This is due to the following reason. That is, when the refrigerant compressed by the first compressor 1 passes through the four-way valve 2, the second gas pipe 53, and the internal heat exchanger 22, a pressure loss occurs and the discharge pressure decreases, and the gas-liquid separator 5 This is because the liquid refrigerant separated in the step passes through the electronic expansion valve 12, the four-way valve 60, the first liquid pipe 54, the outdoor heat exchanger 3, and the four-way valve 2, causing a pressure loss and reducing the suction pressure. . Therefore, the second compressor does not need to perform pressure increasing work corresponding to the pressure loss, and the input power of the second compressor can be reduced and the recovered power of the expander can be used effectively.

Next, the recovery power in the expander 4, the amount of gas generated in the gas-liquid separator 5, and the compression work in the second compressor 9 are compared using FIG. 14 which is a Ph diagram during heating operation. To do. As in the first embodiment, the refrigerant flow rate passing through the expander 4 is Gr, the enthalpy difference at the inlet / outlet of the expander 4 is ΔH1, the refrigerant flow rate at the second compressor is Gr2, and the enthalpy difference at the second compressor 9 is Is ΔH2, the following expression (7) is obtained under the condition that the recovered power in the expander 4 and the compression work in the second compressor are equal.
Gr2 = Gr × (ΔH1 / ΔH2) (7)
Further, the flow rate Gs of the gas separated by the gas-liquid separator 5 is generated by the dryness X (ΔH3 / ΔH0), and is expressed by the equation (8).
Gs = Gr × (ΔH3 / ΔH0) (8)
Here, ΔH1 / ΔH2 in the equation (7) is generally about 0 to 0.2, and ΔH3 / ΔH0 in the equation (8) is generally about 0.2 to 0.6, so that Gr2 <Gs. The refrigerant flow rate Gr2 required by the two compressors 9 can be sufficiently supplied by the gas-liquid separator 5. Further, the refrigerant flow rate difference (Gs−Gr2) is bypassed through the electronic expansion valve 10 during the cooling operation, and is bypassed through the electronic expansion valve 68 during the heating operation.

On the other hand, the expander 4 and the second compressor 9 are coaxially connected, and the displacement ratio between the expander 4 and the second compressor 9 is ε (= second compressor excluded volume / expander expanded volume). = Vc / Ve), and the suction densities of the expander 4 and the second compressor 9 are ρe and ρc, respectively, the equation (9) can be obtained from the condition of constant rotation speed.
Gr2 = Gr × ε × (ρc / ρe) (9)
From the expressions (7) and (9), the expression (10) is obtained.
ρc / ρe = (ΔH1 / ΔH2) / ε (10)
From the above, the expression (10) is established so that any one of the suction density ρc and enthalpy difference ΔH2 of the second compressor 9, the suction density ρe of the expander 9, the inlet / outlet enthalpy difference ΔH1 and ε (= Vc / Ve) is satisfied. Need to control.

  In the present embodiment, when an imbalance occurs between the refrigerant flow rate Gs supplied from the gas-liquid separator 5 and the refrigerant flow rate Gr2 of the second compressor 9 due to environmental conditions such as the outside air temperature, the room temperature, and the air conditioning load, The difference (Gs−Gr2) is bypassed by the electronic expansion valves 10 and 68. That is, the opening degree of the electronic expansion valve 10 is adjusted during the cooling operation, and the opening degree of the electronic expansion valve 68 is adjusted during the heating operation so that the refrigerant flow rate having the above difference flows. Similarly, when an imbalance occurs between the recovery power of the expander 4 and the compression power of the second compressor 9, the opening degree of the electronic expansion valve 12 is appropriately controlled so that the expression (10) is satisfied. That is, when the right side of the equation (10) is large (ρc / ρe <(ΔH1 / ΔH2) / ε), the opening of the electronic expansion valve 12 is reduced, and the expander outlet portion and the evaporator inlet portion shown in FIG. Is increased to increase ρc. At this time, ΔH1 / ΔH2 on the right side of equation (10) also changes at the same time, but both the denominator and numerator become smaller, so the change in ΔH1 / ΔH2 is small, and the operation is performed so that equation (10) is established in the practical range. On the other hand, when the left side of equation (10) is large (ρc / ρe> (ΔH1 / ΔH2) / ε), the opening of the electronic expansion valve 12 is increased, and the expander outlet portion and the evaporator inlet portion shown in FIG. Ρc is decreased by reducing the pressure difference ΔPe. At this time, ΔH1 / ΔH2 on the right side of the equation (10) also changes at the same time, but both the denominator and the numerator increase, so the change in ΔH1 / ΔH2 is small and the operation is performed so that the equation (10) is established.

  As described above, in the present embodiment, expansion power is recovered for all operation modes in a two-stage compression refrigeration cycle apparatus that generates two different evaporation temperatures during cooling operation and two different condensation temperatures during heating operation. can do. Further, since the second compressor 9 connected to the expander is not provided with an electric motor, the recovery power of the expander can be used with a simple configuration and control. In addition, the second compressor driven by the recovery power of the expander performs a boosting work corresponding to a pressure loss when passing through an extension pipe such as a gas pipe or a liquid pipe, an electronic expansion valve, a heat exchanger, or a four-way valve. There is no need to do so, and the input of the second compressor 9, that is, power consumption, is reduced. Furthermore, by controlling the opening degree of the electronic expansion valve 12, it is possible to provide a refrigeration cycle apparatus that can use recovered power under any operating conditions.

  As described in the first and second embodiments, the refrigeration cycle apparatus according to the present invention uses an expander, and uses the high-pressure side refrigerant from the first compressor 1 as the expansion power of the expander 4. The refrigerant converted into the rotational force is separated by the gas-liquid separator 5, and the gas refrigerant is compressed by the second compressor 9 driven by the expander and returned to the high pressure side for energy saving. Further, an efficient refrigeration cycle apparatus is obtained through the internal heat exchanger 22 through the refrigerant compressed by the second compressor before returning to the high pressure side. In this case, the expander is an expansion work associated with the volume expansion of the fluid that has been wasted as heat in the form of friction loss or vortex loss in the conventional throttle device, and the enthalpy at the inlet / outlet of the expander 4 as shown in equation (1). The adiabatic heat drop which is the difference ΔH1 is collected and converted into mechanical energy such as rotational power or reciprocating power and used as compression work of the compressor. As described above, in the present invention, the second compressor driven by the expander is operated as a means for reducing the flow rate of the first compressor both during cooling and during heating by indoor air conditioning. It is used as a means of reduction. On the other hand, the first and third compressors are motor driven.

  As the refrigeration apparatus of the present invention, a natural refrigerant that is supercritical at high pressure and is also good for the global environment is used. In conventional HFC refrigerants, the high-pressure side is a liquid with a small volume expansion and the low-pressure dryness corresponding to the outlet of the expansion device is small, so the expansion loss is small and the recovery power of the expansion power is small. As the volume expansion on the high pressure side increases, that is, the density decrease increases and the dryness at low pressure increases, so that the expansion loss increases. Therefore, the use of expansion power is effective for energy saving. In addition, energy can be further saved by using only this expansion power as the driving force of the second compressor and returning the refrigerant to the high pressure side again. In other words, when the high-pressure fluid expands to a low pressure, the expansion work is performed, and the work consumed as conventional heat is used as the driving force of the compressor. Particularly, CO2 in a supercritical state is close to a gas state. Therefore, a large recovery effect is to be obtained. Note that the refrigerant that performs such work may be air, nitrogen, helium, or a mixed refrigerant of a carbon dioxide refrigerant and other refrigerants such as HFC.

  In the present invention, the expansion power is recovered and used for the compressor to improve the efficiency by returning the gas refrigerant to high pressure again. However, the gas at the gas-liquid separator outlet is sucked in, and the pressure loss is caused by bypassing the high pressure and low pressure parts. It is possible to save energy by reducing. The expander 4 and the second compressor 9 shown in FIG. 1 and FIG. 10 are the most efficient ones that transmit the expansion power of the refrigerant to the refrigerant compression with a scroll structure integrated in the closed container. is there. That is, the expansion fixed scroll and the second compression fixed scroll are fixed to both ends of the sealed container, and a bearing for supporting the rotating shaft is provided at the center. Each oscillating scroll that oscillates and rotates by a rotating shaft at the center of the container so as to face each fixed scroll is provided as an integral rotor so as to oscillate and rotate with the same eccentricity. That is, the high pressure refrigerant is sucked from the expansion / intake pipe through the expansion / fixing scroll to a position close to the axial center of the meshing space with the expansion / swing scroll, and the rotor is rotated while swinging the swing scroll to be outside the container wall. The refrigerant is discharged from the meshing space to the expansion discharge pipe, and the refrigerant is guided to the gas-liquid separator 9. The gas-liquid separated high-pressure gas is located near the outer side away from the axial center of the meshing space with the second compression swing scroll from the second compression suction pipe provided in the same sealed container via the second compression fixed scroll. When the gas refrigerant is sucked into the second compression scroll and the second compression orbiting scroll is swung, that is, the rotor is rotated by the expansion power, the gas is transferred from the inner meshing space near the shaft center to the second compression discharge pipe. The pressure is increased and discharged and returned to the high pressure pipe.

  Further, in the present invention, as shown in FIG. 10, when the high-pressure fluid expands to a low pressure, expansion work is performed, and the work that has been consumed as conventional heat is used as the driving force of the compressor to increase the refrigerant pressure. The third compressor 63 driven by the motor further increases the pressure to perform the heating operation in which the second load side heat exchanger and the second pressure reducing means are passed, and during the cooling operation, the load side heat exchanger performs the air conditioning target space. In addition to performing sensible heat treatment of the air inside, the second load side heat exchanger can dehumidify the air in the air-conditioning target space, and further energy saving can be achieved by separating latent heat from sensible heat. .

  In the present invention, as shown in FIG. 1 and the like, a heat source side unit 100 that is an outdoor unit is provided with a first compressor 1, an outdoor heat exchanger 3, an outdoor blower, and the like, and is intermediate between a plurality of indoor load side units 200. A branch unit 300 is provided at the point, and the expander 4 and the gas-liquid separator 5 are provided in the branch unit 300. During heating, the gas refrigerant separated from the gas and liquid is pressurized by the second compressor 9, and the high-pressure pipe in the branch unit is provided. Connect to. During cooling, the high-pressure gas boosted by the second compressor is heat-exchanged with the low-pressure gas pipe in the branch unit and connected to the high-pressure liquid pipe as a high-pressure liquid. As a result, energy saving operation in which the expander can be used at all times in various operation modes such as a cooling only operation, a cooling main operation, a heating main operation, and a heating operation with a two-tube type is possible. In addition, equipment including the second compressor can be arranged in the branch unit, and the refrigeration cycle apparatus can be easily assembled, and excessive compression work due to pressure loss of the extension pipe can be reduced. In other words, the second compressor directly connected to the expander reduces the pressure boosting work corresponding to the pressure loss of the extension pipe, heat exchanger, and valves, thereby improving the efficiency.

  Further, according to the present invention, a gas-liquid separator is provided at the outlet of the expander in the second load side unit 300 provided outside, and the gas refrigerant after the gas-liquid separation is used as a high pressure in a unit 300 different from the outdoor unit 100. Connect to piping. That is, during heating, the high-pressure gas boosted by the sub-compressor that is the second compressor is connected in the unit 300 to the high-pressure gas pipe that is the suction side of the third compressor that is the latent heat compressor. During cooling, the high pressure gas boosted by the sub-compressor is heat-exchanged with the low pressure gas pipe in the unit 300 and then connected to the high pressure liquid pipe in the unit 300 as a high pressure liquid. As a result, the expander can be used for cooling and heating operation, and energy saving operation can be performed.

  Therefore, the compression work of the first compressor provided in the outdoor air conditioner unit 100 such as a building mulch that separates and processes latent heat and sensible heat can be greatly reduced and the efficiency can be improved. In addition, the second compressor is arranged in the unit 300, so that excessive compression work due to pressure loss of the extension pipe can be reduced, and further, the flow of refrigerant flowing to the low pressure side is reduced by the gas-liquid separator, so the compression work due to low pressure loss is also reduced. And an efficient device.

  As described in the first and second embodiments, the refrigeration cycle apparatus according to the present invention includes the first compressor that compresses the refrigerant, the heat source side heat exchanger that condenses or evaporates the refrigerant, and the operating state of the load. A gas-liquid that separates the gas-liquid of the refrigerant through the heat source side unit comprising the first flow path switching means for switching the refrigerant flow and the expander that obtains the rotational force by the high-pressure refrigerant from the heat source side unit or the load side and expands. A natural refrigerant having a very high pressure difference, such as a supercritical state such as carbon dioxide, having a branch unit made of a separator, a plurality of load side units made of a first pressure reducing means and a load side heat exchanger. And a refrigeration cycle apparatus in which a plurality of load-side units can individually select a cooling operation and a heating operation, through only a recovery power from the expander, that is, through a second compressor that is driven without using an electric motor. It is characterized in that connects the discharge portion of the gas-liquid separator of a gas-side outlet and the first compressor.

  The refrigeration cycle apparatus of the present invention is characterized in that an internal heat exchanger for exchanging heat between the outlet portion of the second compressor and the suction portion of the first compressor is provided. The refrigeration cycle apparatus of the present invention is characterized in that the second pressure reducing means is provided at the liquid side outlet of the gas-liquid separator. Further, the present invention is characterized in that the suction portion of the first compressor and the gas side outlet portion of the gas-liquid separator are connected by a first bypass pipe via a third pressure reducing means whose opening degree can be changed. It is. The refrigeration cycle apparatus of the present invention is characterized in that a fourth pressure reducing means capable of changing the opening degree is provided between the gas side outlet of the gas-liquid separator and the suction part of the second compressor. is there.

  Further, the refrigeration cycle apparatus of the present invention switches the first compressor that compresses the low-pressure refrigerant and discharges the high-pressure refrigerant, the heat source side heat exchanger that evaporates or condenses the discharged and circulated refrigerant, and switches the flow direction of the circulated refrigerant. A heat source side unit comprising a first flow path switching means, a first load side unit provided with a plurality of first load side heat exchangers having a first pressure reducing means capable of adjusting the refrigerant flow rate, at least a second compressor, A second load side heat exchanger, a second flow path switching means, an expander, a second load side unit comprising a gas-liquid separator, and a two-stage compression refrigeration cycle apparatus using carbon dioxide as a refrigerant, The gas-side outlet portion of the gas-liquid separator and the discharge portion of the first compressor are connected via a second compressor that is driven only by the recovery power from the expander.

  The refrigeration cycle apparatus of the present invention is characterized in that an internal heat exchanger for exchanging heat between the outlet portion of the second compressor and the suction portion of the first compressor is provided. The refrigeration cycle apparatus of the present invention is characterized in that the second pressure reducing means is provided at the liquid side outlet of the gas-liquid separator. In the refrigeration cycle apparatus of the present invention, the suction portion of the first compressor and the gas side outlet portion of the gas-liquid separator are connected by the first bypass pipe via the third decompression means capable of changing the opening degree. It is a feature. The refrigeration cycle apparatus of the present invention is characterized in that a fourth pressure reducing means capable of changing the opening degree is provided between the gas side outlet of the gas-liquid separator and the suction part of the second compressor. is there. The refrigeration cycle apparatus of the present invention is characterized in that a third flow path switching means is provided at the inlet of the expander.

  The refrigeration cycle apparatus according to the present invention includes a heat source side unit including at least a first compressor, a heat source side heat exchanger, and a first flow path switching unit, a branch unit including at least an expander and a gas-liquid separator, and at least a first unit. Expansion in a refrigeration cycle apparatus having a plurality of load side units composed of decompression means and load side heat exchangers, using carbon dioxide as a refrigerant, and capable of individually selecting a cooling operation and a heating operation by the plurality of load side units Since the gas side outlet part of the gas-liquid separator and the discharge part of the first compressor are connected via the second compressor driven only by the recovery power from the compressor, the expansion power can be recovered in all operation modes. A refrigeration cycle apparatus capable of reducing power consumption can be provided.

  Further, the refrigeration cycle apparatus of the present invention is provided with an internal heat exchanger that exchanges heat between the outlet portion of the second compressor and the suction portion of the first compressor, so that expansion power can be recovered in all operation modes. A refrigeration cycle apparatus can be provided.

  In the refrigeration cycle apparatus of the present invention, since the second pressure reducing means is provided at the liquid side outlet of the gas-liquid separator, there is an imbalance between the recovery power of the expander and the compression power of the second compressor. But you can adjust the power appropriately.

  Further, in the refrigeration cycle apparatus of the present invention, the suction portion of the first compressor and the gas side outlet portion of the gas-liquid separator are connected by the first bypass pipe via the third decompression means capable of changing the opening degree. Even when an imbalance occurs between the refrigerant flow rate supplied from the gas-liquid separator and the refrigerant flow rate of the second compressor, the refrigerant flow rate can be adjusted appropriately.

  In the refrigeration cycle apparatus according to the present invention, the fourth decompression means capable of changing the opening degree is provided between the gas side outlet portion of the gas-liquid separator and the suction portion of the second compressor. Even when an imbalance occurs between the recovered power and the compressed power of the second compressor, the power can be adjusted appropriately.

  The refrigeration cycle apparatus of the present invention comprises at least a first compressor, a heat source side heat exchanger, a heat source side unit comprising first flow path switching means, and at least a first pressure reducing means and a first load side heat exchanger. A plurality of first load-side units, and a second load-side unit including at least a third compressor, a second load-side heat exchanger, a second flow path switching unit, an expander, and a gas-liquid separator; In the two-stage compression type refrigeration cycle apparatus using carbon dioxide as a gas outlet portion of the gas-liquid separator and a discharge portion of the first compressor via a second compressor driven only by recovery power from the expander Is connected, the recovered power of the expander can be used in all operation modes of the two-stage compression refrigeration cycle.

  Further, since the refrigeration cycle apparatus of the present invention includes the internal heat exchanger that exchanges heat between the outlet portion of the second compressor and the suction portion of the first compressor, all the operation modes of the two-stage compression refrigeration cycle are provided. The recovery power of the expander can be used.

  In the refrigeration cycle apparatus of the present invention, since the second pressure reducing means is provided at the liquid side outlet of the gas-liquid separator, there is an imbalance between the recovery power of the expander and the compression power of the second compressor. But you can adjust the power appropriately.

  Further, in the refrigeration cycle apparatus of the present invention, the suction portion of the first compressor and the gas side outlet portion of the gas-liquid separator are connected by the first bypass pipe via the third decompression means capable of changing the opening degree. Even when an imbalance occurs between the refrigerant flow rate supplied from the gas-liquid separator and the refrigerant flow rate of the second compressor, the refrigerant flow rate can be adjusted appropriately.

  In the refrigeration cycle apparatus according to the present invention, the fourth decompression means capable of changing the opening degree is provided between the gas side outlet portion of the gas-liquid separator and the suction portion of the second compressor. Even when an imbalance occurs between the recovered power and the compressed power of the second compressor, the power can be adjusted appropriately.

  Moreover, since the refrigeration cycle apparatus of the present invention is provided with the third flow path switching means at the inlet of the expander, the recovery power of the expander can be used in all operation modes.

It is a figure which shows the refrigerant | coolant flow of the cooling only operation of the refrigerating-cycle apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the operation | movement of the cooling only operation on the Ph diagram which concerns on Embodiment 1 of this invention. It is a figure which shows the refrigerant | coolant flow of the heating only operation | movement of the refrigerating-cycle apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the operation | movement of the heating only operation on the Ph diagram which concerns on Embodiment 1 of this invention. It is a figure which shows the refrigerant | coolant flow of the cooling main operation | movement of the refrigerating-cycle apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the operation | movement of the cooling main operation | movement on the Ph diagram which concerns on Embodiment 1 of this invention. It is a figure which shows the refrigerant | coolant flow of the heating main driving | operation of the refrigeration cycle apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the operation | movement of the heating main driving | operation on the Ph diagram which concerns on Embodiment 1 of this invention. It is a figure explaining the relationship of the recovery power in the expander which concerns on Embodiment 1 of this invention, the compression power in a 2nd compressor, the refrigerant | coolant flow rate of an expander, a 2nd compressor, and a gas-liquid separator. It is a figure which shows the refrigerant | coolant flow of the cooling operation of the refrigerating-cycle apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows the operation | movement of the air_conditionaing | cooling operation on the Ph diagram which concerns on Embodiment 2 of this invention. It is a figure which shows the refrigerant | coolant flow of the heating operation of the refrigeration cycle apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows the operation | movement of the heating operation on the Ph diagram which concerns on Embodiment 2 of this invention. It is a figure explaining the relationship of the recovery power in the expander which concerns on Embodiment 2 of this invention, the compression power in a 2nd compressor, the refrigerant | coolant flow rate of an expander, a 2nd compressor, and a gas-liquid separator.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 1st compressor, 2, 60, 61 Four-way valve, 3 Heat source side heat exchanger, 4 Expansion machine, 5 Gas-liquid separator, 6a, 6b, 6c 10, 12, 20, 65, 68 Electronic expansion valve, 7a, 7b, 7c Indoor heat exchanger, 9 Second compressor, 13 Suction pipe, 14, 67 First bypass pipe, 19 Second bypass pipe, 21a, 21b, 21c, 21d, 36, 37, 38, 39, 40, 41 Check valve, 22 Internal heat exchanger, 30, 31, 32, 33, 34, 35, 42, 43, 66 Solenoid valve, 51 High pressure pipe, 52 Low pressure pipe, 53 First gas pipe, 54 First Liquid pipe, 55 second gas pipe, 56 second liquid pipe, 63 third compressor, 64 second load side heat exchanger, 100 outdoor unit, 200a, 200b, 200c indoor unit, 300 branch unit Rui second load unit.

Claims (10)

A first compressor that is provided in a refrigerant circuit that uses natural refrigerant that is in a supercritical state on the high-pressure side as a refrigerant, sucks low-pressure refrigerant, discharges high-pressure refrigerant, and circulates the refrigerant, and circulates through the refrigerant circuit. A heat source side heat exchanger that condenses or evaporates the refrigerant, and a refrigerant discharged from the first compressor is circulated to the load side through the heat source side heat exchanger or not through the heat source side heat exchanger. A plurality of load-side heat exchangers capable of individually selecting a cooling operation and a heating operation by switching the refrigerant flow in the refrigerant circuit, an expander for recovering the expansion power of the high-pressure refrigerant, and the expander A gas-liquid separator that separates the expanded refrigerant into a gas-liquid separator, and a second compressor that compresses the refrigerant from the gas-side outlet with the power recovered by the expander. The refrigerant discharged from the second compressor Serial refrigerating cycle apparatus characterized by a high-pressure refrigerant connects the discharge side of the first compressor. A circuit connecting the high pressure side and the low pressure side of the refrigerant circuit is provided with a third load and a second load side heat exchanger different from the load side heat exchanger that performs indoor air conditioning in parallel. The refrigeration cycle apparatus according to claim 1. The refrigeration cycle apparatus according to claim 2, wherein the load-side heat exchanger and the second load-side heat exchanger are operated at different pressures during cooling operation or heating operation. The refrigeration cycle apparatus according to claim 1 or 2, further comprising an internal heat exchanger for exchanging heat between the outlet portion of the second compressor and the suction portion of the first compressor. The refrigeration cycle apparatus according to any one of claims 1 to 4, wherein a decompression means is provided at a liquid side outlet of the gas-liquid separator. 6. The suction unit of the first compressor and the gas side outlet of the gas-liquid separator are connected to each other by a bypass pipe through a decompression unit capable of changing an opening degree. The refrigeration cycle apparatus described in 1. 7. The gas pipe according to claim 1, wherein the gas side outlet of the gas-liquid separator and the suction part of the second compressor are connected by a bypass pipe through a pressure reducing means capable of changing an opening degree. The refrigeration cycle apparatus according to crab. The refrigeration cycle apparatus according to any one of claims 1 to 7, wherein a flow path switching means is provided at an inlet of the expander. A heat source side unit provided with at least the first compressor and the heat source side heat exchanger, a load side unit comprising a plurality of the load side heat exchangers provided in the room, at least the second compressor, and the expansion And a branch unit provided with the gas-liquid separator, carbon dioxide is used as a refrigerant, and the equipment disposed in the branch unit is connected to the high-pressure side pipe and the low-pressure side pipe of the refrigerant circuit. The refrigeration cycle apparatus according to claim 1 or 2. The refrigeration cycle apparatus according to claim 9, wherein a load-side heat exchanger different from the load-side heat exchanger is provided in the branch unit to perform air conditioning in the room.

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