JP2012107862A - Refrigeration cycle device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigeration cycle device which can keep the inlet temperature of an expansion valve high to improve the unit efficiency of an expansion device, in the refrigeration cycle device configured to recover the power of the expansion device by coaxially connecting a compressor to the expansion device.SOLUTION: The refrigeration cycle device includes: a main refrigerant circuit 6 including a first compressor 1, a radiator 2, an expansion device 3a and an evaporator 4, which are successively connected through piping, and also including a second compressor 3b which is driven by power recovered by the expansion device 3a to receive and compress part of refrigerant flowing from the evaporator 4 to the first compressor 1; and a bypass circuit 7 bypassing the expansion device 3a and including an internal heat exchanger 5a and a flow control valve 12. The internal heat exchanger 5a performs heat exchange between high-pressure refrigerant which has entered the bypass circuit 7 flowing through the radiator 2 and a low-pressure two-phase refrigerant obtained after part of the refrigerant flowing through the either a radiator outlet or the internal heat exchanger outlet is depressed with the flow control valve 12.

Description

  The present invention relates to a refrigeration cycle apparatus using a supercritical fluid, and more particularly to a configuration of a refrigeration cycle apparatus in which a compressor and an expander are connected coaxially and power of the expander is recovered.

  As a conventional refrigeration cycle apparatus, “a compressor that compresses refrigerant, a radiator that cools the refrigerant compressed by the compressor, an internal heat exchanger through which the refrigerant cooled by the radiator passes, and the compression A main refrigerant circuit that is connected directly to the compressor and expands the refrigerant that has passed through the internal heat exchanger, and an evaporator that heats the refrigerant expanded by the expander; and the internal heat A first flow control valve that branches from the main refrigerant circuit between the exchanger and the expander and controls a refrigerant flow rate; a refrigerant that is cooled by the radiator and passes through the internal heat exchanger; The first bypass flow path connected to the main refrigerant circuit between the expander and the evaporator via the internal heat exchanger that exchanges heat with the refrigerant that has passed through the flow control valve A refrigeration cycle apparatus having References 1).

  In this technology, “density ratio = constant” (density ratio = expanding refrigerant inflow refrigerant density / The power recovery amount can be kept high while avoiding the restriction on the compressor inflow refrigerant density.

  In this technology, the flow rate of the refrigerant flowing through the bypass circuit is controlled by the flow rate control valve, thereby not only avoiding the restriction of the operating condition in which the density ratio, which is the ratio of the refrigerant density entering the compressor / the refrigerant density entering the compressor, is constant. By performing internal heat exchange between the refrigerant on the radiator outlet side and the refrigerant in the bypass channel, the refrigerant flowing through the bypass channel that does not contribute to power recovery can be minimized. That is, a high-efficiency refrigeration cycle can be realized while avoiding the restriction of a constant density ratio.

JP 2008-14602 A (Claim 1, FIG. 1)

Incidentally, it is known that the power recovery amount in the expander varies depending on the refrigerant inlet temperature, and generally the power recovery amount increases as the temperature increases, and the effect of the sub-compressor integrated expander increases. This is because when the refrigerant flows into the expander in a supercritical state such as CO ₂ , the refrigerant has a gas property as the temperature is high, and has a liquid property as the temperature is low. That is, when the state of the refrigerant flowing into the expander is close to gas, it expands more in the expansion process and much expansion power is recovered, whereas when the state of the refrigerant flowing into the expander is close to liquid, The expansion amount in the expansion process is small, and the expansion power recovery amount recovered accordingly is also reduced. Therefore, it is desirable to increase the refrigerant temperature at the inlet of the expander. However, in the conventional example, the high-pressure refrigerant that has flowed out of the radiator is allowed to pass through the internal heat exchanger, heat-exchanged with the low-pressure refrigerant in the internal heat exchanger, cooled, and then flowed into the expansion valve. The temperature flowing into the valve will drop. For this reason, the effect of the expander is reduced, and in the case of the sub-compressor integrated structure that requires scrolling, there is a problem that the single unit efficiency (operating efficiency) decreases.

  The present invention has been made in view of such points, and in a refrigeration cycle apparatus that coaxially connects a compressor and an expander to recover the power of the expander, the inlet temperature of the expansion valve can be kept high, It aims at obtaining the refrigerating-cycle apparatus which can improve the single-piece | unit efficiency of an expander.

  In the refrigeration cycle apparatus according to the present invention, a first compressor, a radiator, an expander, and an evaporator are sequentially connected by a pipe, and are driven by power recovered by the expander, and travel from the evaporator to the first compressor. A main refrigerant circuit including a second compressor that receives and compresses a part of the refrigerant; and a bypass circuit that bypasses the expander and includes an internal heat exchanger and a flow rate control valve. Heat exchange between the high-pressure refrigerant that has flowed out of the condenser and flowed into the bypass circuit, and the low-pressure two-phase refrigerant that has been partially depressurized by the flow control valve from the radiator outlet or the internal heat exchanger outlet It is.

  The present invention bypasses the expander and increases the heating capacity by the internal heat exchanger under conditions where the expansion power is small, such as low outside air, and the bypass is closed under conditions where the expansion power is large and the recovery effect is large. This is a refrigeration cycle apparatus that achieves capacity priority or efficiency priority by switching operation by performing power recovery in response to environmental conditions. Moreover, the density ratio (expander inlet density / compressor inlet density) of the expander can be reduced, and the single unit efficiency of the expander is improved.

It is a figure which shows the refrigerating-cycle apparatus in Embodiment 1 of this invention. It is a figure which shows the cross section of the sub compressor integrated expander of FIG. It is a figure which shows the refrigerating-cycle apparatus in Embodiment 2 of this invention. It is a figure which shows the refrigerating-cycle apparatus in Embodiment 3 of this invention.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of a refrigeration cycle apparatus in Embodiment 1 of the present invention. As shown in FIG. 1, the refrigeration cycle apparatus according to Embodiment 1 includes a first compressor 1 for compressing refrigerant gas, a radiator 2, and expansion of the refrigerant to reduce the refrigerant into two-phase wet steam. It has a main refrigerant circuit 6 in which the low-pressure side flow paths of the machine 3a, the evaporator 4, and the internal heat exchanger 5 are sequentially connected by piping. The main refrigerant circuit 6 includes a second compressor 3b that is coaxially connected to the expander 3a and is driven by power collected by the expander 3a.

  Moreover, the bypass circuit 7 which bypasses the expander 3a is provided. The bypass circuit 7 has an internal heat exchanger 5 and an on-off valve 10 as a flow control valve, and a part of the refrigerant flowing out of the radiator 2 is removed from the high-pressure side of the internal heat exchanger 5 of the bypass circuit 7 and It is made to merge with the exit part of the expander 3a via the on-off valve 10. The internal heat exchanger 5 exchanges heat between the high-pressure refrigerant flowing out of the radiator 2 and flowing into the bypass circuit 7 and the low-pressure refrigerant at the outlet of the evaporator 4. Here, the low-pressure side refrigerant of the internal heat exchanger 5 is the refrigerant at the outlet of the evaporator 4, but in order to make a difference in the suction density of the first compressor 1 and the second compressor 3b, It may be at least one of the suction refrigerant and the suction refrigerant of the second compressor 3b.

  The expander 3a and the second compressor 3b are coaxially connected as described above, and form an integral structure as the sub-compressor-integrated expander 3. In the main refrigerant circuit 6, the suction side of the second compressor 3 b is installed in parallel with the suction side of the first compressor 1, and the discharge side of the second compressor 3 b communicates with the compression chamber of the first compressor 1. Connected to the injection port. As a result, the refrigerant discharged from the second compressor 3b is injected from the injection port of the first compressor 1 into the compression chamber in the middle of compression. For example, carbon dioxide that is in a supercritical state at a critical temperature (about 31 ° C.) or higher is sealed inside the refrigeration cycle apparatus as a refrigerant.

  The detailed structure of the sub compressor-integrated expander 3 is shown in FIG. The expander 3a and the second compressor 3b are both expander units adopting a scroll structure, and the expander 3a includes an expander fixed scroll 351 and an expander swing scroll 352, and the second compressor 3 b includes a second compressor fixed scroll 361 and a second compressor swing scroll 362. A shaft 308 passes through the center of these scrolls in the vertical direction, and balance weights 309 a and 309 b are provided at both ends of the shaft 308. The shaft 308 is supported by an expander bearing portion 351b and a second compressor bearing portion 361b. Further, the back surface of the swing scroll 352 of the expander 3a and the back surface of the swing scroll 362 of the second compressor 3b have a back-to-back structure.

  The expander fixed scroll 351 has a configuration in which spiral teeth 351a are erected upward from the end plate. The expander swing scroll 352 is provided with an expander-side spiral tooth 352a that is engaged with the spiral teeth 351a of the expander fixed scroll 351 on the lower surface facing the expander fixed scroll 351. In addition, the expander 3a is configured.

  The second compressor fixed scroll 361 also has a configuration in which spiral teeth 361a are erected downward from the end plate. The second compressor orbiting scroll 362 is provided with a second compressor side spiral tooth 362 a that is engaged with the spiral teeth 361 a of the second compressor fixed scroll 361 on the upper surface facing the second compressor fixed scroll 361. The second compressor 3b is configured together with the second compressor fixed scroll 361. In addition, an Oldham ring 307 and a crank portion 308 b which are necessary parts are provided, and these are all stored in the hermetic container 310.

  In the sub-compressor-integrated expander 3 having such a structure, if the volume ratio (compressor internal volume / expander internal volume) is designed to be large (for example, 2 or more), at the same tooth height, from the second compressor 3b. The thrust load from the expander 3a side is reduced with respect to the thrust load, and the thrust load cannot be offset on both sides of the orbiting scrolls 352 and 362. For this reason, the configuration of the sub compressor-integrated expander 3 in which the second compressor 3b and the expander 3a are integrated becomes difficult. Further, in order to reduce the thrust load on the second compressor 3b side, it is possible to make the second compressor 3b side a spiral having an extremely high tooth height, but this causes a problem in strength. Therefore, in the sub-compressor integrated type in which both the expander 3a and the second compressor 3b have a scroll structure, by setting the expansion / compression volume ratio in the range of 2 or less, not only in terms of performance but also in terms of structure, reliability is achieved. A high expander unit can be constructed.

The operation of the refrigeration cycle apparatus configured as described above will be described. Here, it demonstrates as the thing which the heat radiator 2 operate | moves as a utilization side heat exchanger.
In normal heating operation, power recovery is performed using only the main refrigerant circuit 6. That is, the bypass flow rate is 0%, the on-off valve 11 is opened, and the on-off valve 10 is closed.
The high-pressure gas refrigerant discharged from the first compressor 1 is sent to the radiator 2. The high-pressure gas refrigerant sent to the radiator 2 exchanges heat with room air to dissipate heat to become a high-pressure medium-temperature refrigerant, and then flows into the expander 3a. The refrigerant flowing into the expander 3a is decompressed to a low-pressure and low-temperature gas-liquid two-phase refrigerant while recovering power, evaporates in the evaporator 4, and flows into the low-pressure side of the internal heat exchanger 5. Since the on-off valve 10 is closed, the refrigerant does not pass through the bypass circuit 7. Therefore, heat exchange is not performed in the internal heat exchanger 5, and the refrigerant flowing out of the evaporator 4 passes through the internal heat exchanger 5 as it is and returns to the suction side of the first compressor 1 and the second compressor 3b.

  The rotation speed of the second compressor 3b is the same as that of the expander 3a, and the discharge pressure (injection pressure) of the second compressor 3b is set so that the recovered power of the expander 3a matches the power consumption of the second compressor 3b. ) Is determined. The injection port position of the first compressor 1 is designed such that the injection port pressure of the first compressor 1 is lower than the discharge pressure of the second compressor 3b, or the discharge pressure of the second compressor 3b is When the pressure is lower than the injection port pressure of the first compressor 1, it is designed not to recover power.

  Here, a case where the outlet temperature of the radiator 2 is relatively low and the performance improvement effect by power recovery is small, as in the heating operation under the low outside air condition, on the other hand, a large heating capacity is required will be described. In this case, the refrigerant is supplied to both the main refrigerant circuit 6 and the bypass circuit 7, and an operation is performed in which both power recovery by the expander 3a and heat exchange by the internal heat exchanger 5 are performed.

Next, an operation for performing both power recovery and heat exchange by the internal heat exchanger 5 will be described. In this operation, since the refrigerant flows through both the expander 3a and the bypass circuit 7, the opening / closing valve 11 and the opening / closing valve 10 are set to appropriate opening degrees.
In this case, the high-temperature and high-pressure gas refrigerant discharged from the first compressor 1 is sent to the radiator 2. The high-pressure gas refrigerant sent to the radiator 2 is condensed by exchanging heat with room air and becomes high-pressure liquid refrigerant, and then the flow rate is controlled by the on-off valve 11 and flows into the expander 3a. The refrigerant flowing into the expander 3a is decompressed to a low-pressure and low-temperature gas-liquid two-phase refrigerant while recovering power, evaporates in the evaporator 4, and flows into the low-pressure side of the internal heat exchanger 5.

  On the other hand, the refrigerant flowing out of the radiator 2 and flowing into the bypass circuit 7 flows into the high-pressure side of the internal heat exchanger 5 and is cooled by exchanging heat with the low-pressure side refrigerant of the internal heat exchanger 5. The dryness decreases. Then, the refrigerant that has flowed out of the high pressure side of the internal heat exchanger 5 is decompressed by the on-off valve 10, and then merges with the refrigerant from the main refrigerant circuit 6 and flows into the evaporator 4. The refrigerant evaporated in the evaporator 4 flows into the low-pressure side of the internal heat exchanger 5, exchanges heat with the high-pressure side refrigerant of the internal heat exchanger 5, and evaporates to the first compressor 1 and the second compressor 3 b. Inhaled. The refrigerant sucked into the second compressor 3b is compressed by the second compressor 3b and then sucked into the first compressor 1.

  On the other hand, the on-off valve 10 is closed (the bypass circuit 7 is closed) under conditions where the outlet temperature of the radiator 2 is relatively high, the expansion power is large, and the performance improvement effect is large, as in the cooling operation under high outside air conditions. ), Power recovery operation using the expander 3a is performed.

  As described above, in the refrigeration cycle apparatus of the first embodiment, the internal heat exchanger 5 is provided in the bypass circuit 7 that branches from between the radiator 2 and the expander 3a and is connected to the outlet of the expander 3a. The refrigerant that has flowed out of the vessel 2 is branched and directly flows into the expander 3a. Therefore, compared with the structure which provided the internal heat exchanger between the heat radiator and the expander like patent document 1, the inlet temperature of the expander 3a can be raised, and the single unit efficiency of the expander 3a can be increased. It is possible to improve.

  In the heating operation under the low outside air condition, a part of the high-pressure refrigerant flowing out from the radiator 2 is passed through the bypass circuit 7 and cooled by the refrigerant passing through the low-pressure side in the internal heat exchanger 5. Then, the pressure was reduced and the gas was allowed to flow into the evaporator 4. As a result, the temperature at the evaporator inlet can be lowered, and the enthalpy difference between the inlet and outlet of the evaporator 4 (note that the evaporator outlet temperature is fixed) can be increased. Thus, the enthalpy difference can be increased, so that the heating capacity can be improved, and as a result, an energy-saving refrigeration cycle apparatus can be obtained.

  Further, since the refrigerant passing through the low pressure side in the internal heat exchanger 5 is heated by the refrigerant passing through the high pressure side and then sucked into the first compressor 1, the intake temperature of the first compressor 1 is increased. be able to. Therefore, the heating capacity can be improved also from this point.

  By the way, if the bypass flow rate is increased, the power recovery efficiency in the expander 3a is lowered, and the operation efficiency of the refrigeration cycle apparatus is lowered accordingly. However, on the other hand, since the temperature at the evaporator inlet can be lowered in the heating operation, the enthalpy difference can be increased and the heating capacity can be improved. Therefore, the ratio between the expander passage flow rate and the bypass passage flow rate may be determined so that the cycle efficiency is maximized. The opening degree of the on-off valve 11 is determined according to this flow rate ratio.

  Further, since the internal heat exchanger 5 is provided in the bypass circuit 7, the bypass flow rate (that is, the bypass circuit) is independent of the density ratio and the flow rate ratio in the expander 3a and the second compressor 3b coaxially connected to the expander 3a. 7) can be determined. Therefore, it is possible to increase the bypass flow rate by giving priority to the heating capacity.

  Further, since the inlet temperature of the expander 3a is not affected by the heat exchange amount of the internal heat exchanger 5, the density ratio (expander 3a inlet density / second compressor 3b inlet density) becomes small, and the orbiting scroll. The difference between the spiral tooth heights of 352 and 362 can be reduced. For this reason, the single unit efficiency of the expander 3a also improves in terms of structure.

  In addition, since the refrigerant is carbon dioxide and a naturally occurring substance is used as the refrigerant, even if it leaks unexpectedly from the refrigeration cycle device, the ozone layer is not destroyed and the refrigeration cycle is excellent in safety and is friendly to the global environment. It can be a device.

Embodiment 2. FIG.
FIG. 3 is a diagram showing a configuration of the refrigeration cycle apparatus according to Embodiment 2 of the present invention. In FIG. 3, the same parts as those in FIG. Since the basic configuration of the second embodiment is the same as that of the first embodiment, the following description will focus on different points.
In the second embodiment, as in the first embodiment, instead of the internal heat exchanger 5 in which the refrigerant at the radiator outlet and the refrigerant at the evaporator outlet exchange heat, the refrigerant at the radiator outlet and the heat radiation The example using the internal heat exchanger 5a which heat-exchanges with the refrigerant | coolant which pressure-reduced some refrigerant | coolants of the container exit part is shown. As a specific circuit configuration, the main refrigerant circuit 6 similar to that of the first embodiment, the radiator 2 of the main refrigerant circuit 6 and the expander 3a are branched, and the internal heat exchanger 5a and the on-off valve 10 are provided. Via the bypass circuit 7 connected to the outlet side of the expander 3a, and between the internal heat exchanger 5a of the bypass circuit 7 and the on-off valve 10 and branching between the on-off valve 12 and the low-pressure side of the internal heat exchanger 5a And an injection circuit 7a joined and connected on the discharge side of the second compressor 3b.

The operation switching method and the power recovery operation by the expander 3a using only the main refrigerant circuit 6 are the same as those in the first embodiment. Therefore, below, the operation | movement which performs both power collection | recovery and the heat exchange by the internal heat exchanger 5a performed by the heating operation by low external air conditions is demonstrated. In this case, all the on-off valves 10 to 12 are set to an appropriate opening degree.
The high-temperature and high-pressure gas refrigerant discharged from the first compressor 1 is sent to the radiator 2. The high-pressure gas refrigerant sent to the radiator 2 performs heat exchange with room air to condense into a high-pressure liquid refrigerant, and then the flow rate is controlled by the on-off valve 11 and flows into the expander 3a. The refrigerant that has flowed into the expander 3a is reduced in pressure to a low-pressure and low-temperature gas-liquid two-phase refrigerant while being recovered in power, and flows into the evaporator 4.

  On the other hand, a part of the refrigerant that flows out of the radiator 2 and goes to the expander 3 a flows into the bypass circuit 7. The refrigerant that has flowed into the bypass circuit 7 flows into the high-pressure side of the internal heat exchanger 5a, is cooled by exchanging heat with the low-pressure two-phase refrigerant on the low-pressure side of the internal heat exchanger 5a, and the dryness is lowered. The refrigerant that has flowed out of the high-pressure side of the internal heat exchanger 5 a is decompressed by the on-off valve 10, merges with the refrigerant from the main refrigerant circuit 6, and flows into the evaporator 4.

  The refrigerant evaporated in the evaporator 4 is sucked into the first compressor 1 and the second compressor 3b. The refrigerant sucked into the second compressor 3b is compressed by the second compressor 3b and then sucked into the first compressor 1.

  A part of the refrigerant that has passed through the high-pressure side of the internal heat exchanger 5a flows into the injection circuit 7a and is reduced to a low-pressure low-temperature two-phase refrigerant by the on-off valve 12, and then the low-pressure side of the internal heat exchanger 5a. Flow into. The low-pressure two-phase refrigerant flowing into the low-pressure side of the internal heat exchanger 5a evaporates by exchanging heat with the refrigerant passing through the high-pressure side, and then compressed in the compression process from the injection port communicating with the compression chamber of the first compressor 1 It is injected into the room as injection gas. In the configuration of FIG. 3, the refrigerant merges with the refrigerant from the expander 3 a and is injected into the compression chamber of the first compressor 1.

  Here, the on-off valve 12 is a pressure reducing valve whose internal opening degree (flow resistance) is variable, and the opening degree is controlled so that the refrigerant state at the low-pressure side outlet of the internal heat exchanger 5a has a predetermined superheat degree. Is done. The degree of superheat at the low-pressure side outlet of the internal heat exchanger 5a is defined by the temperature difference between the low-pressure side outlet refrigerant temperature in an overheated state and the two-phase refrigerant temperature at the outlet of the on-off valve 12.

  According to the second embodiment, the same effect as in the first embodiment can be obtained, and a part of the liquid refrigerant from the internal heat exchanger 5a toward the evaporator 4 is branched to reduce the low pressure side of the internal heat exchanger 5a. The following effects can be obtained. That is, the flow rate of the two-phase refrigerant passing through the evaporator 4 is reduced, and the suction refrigerant of the first compressor 1 and the second compressor 3b passes through the low pressure side of the internal heat exchanger 5a as in the first embodiment. Therefore, the pressure loss at the suction portion can be reduced, and the cycle performance is improved. In the second embodiment, the example in which the refrigerant branched at the outlet of the internal heat exchanger 5a is caused to flow into the low pressure side of the internal heat exchanger 5a is shown. However, the inlet side (heat radiator) of the internal heat exchanger 5a is shown. The refrigerant branched off at the (2 outlet side) may be allowed to flow into the low pressure side of the internal heat exchanger 5a. In this case, the same effect is exhibited.

  In the second embodiment, a part of the high-pressure refrigerant that flows out of the radiator 2 and is introduced into the expander 3a is first bypassed through the bypass circuit 7 and the injection circuit 7a, bypassing the expander 3a. Injection was made into the compression chamber in the compressor 1. Thereby, there exists an effect (injection effect) which can reduce the compression power for the bypass flow volume from a compressor suction pressure to the pressure in the middle of compression (intermediate pressure).

  The injection flow rate is controlled by the on-off valve 12, and the on-off valve 12 is provided in an injection circuit 7 a branched from the bypass circuit 7 and connected to the compression chamber in the first compressor 1. For this reason, the opening degree of the on-off valve 12, that is, the injection flow rate does not affect the inlet temperature of the expander 3a. Since the inlet temperature of the expander 3a affects the inflow refrigerant density of the expander 3a, the expander 3a and the second compressor 3b coaxially connected to the expander 3a are restricted by the density ratio and the flow rate ratio. For this reason, if the injection flow rate is configured to affect the inlet temperature of the expander 3a, the injection flow rate is also restricted by the density ratio and flow rate ratio, and cannot be freely changed. For example, in the configuration of Patent Document 1, since an internal heat exchanger is provided on the inlet side of the expansion valve, the inlet temperature of the expansion valve varies depending on the heat exchange amount of the internal heat exchanger. For this reason, it is necessary to determine the bypass flow rate (injection flow rate) for passing the internal heat exchanger according to the inlet temperature of the expansion valve. However, in the second embodiment, since the injection flow rate does not affect the inlet temperature of the expander 3a, the injection flow rate can be determined regardless of the density ratio or the flow rate ratio. Therefore, it is possible to increase the injection flow rate by giving priority to the heating capacity.

Embodiment 3 FIG.
FIG. 4 is a diagram showing a configuration of the refrigeration cycle apparatus according to Embodiment 3 of the present invention. In FIG. 4, the same parts as those in the second embodiment shown in FIG. The refrigeration cycle apparatus of the third embodiment is basically provided with the refrigeration cycle apparatus of the second embodiment shown in FIG. 3, and further has a configuration in which the expander 3a can be used for both the cooling operation and the heating operation. That is, a four-way valve 20 for switching the flow direction of the refrigerant is provided on the discharge side of the first compressor 1, and a bridge circuit including four check valves around the expander 3a (check valves 16a, 16b, A rectifier circuit formed by a combination of 16c and 16d). In addition, although the structure provided fundamentally with the refrigerating-cycle apparatus of Embodiment 2 shown in FIG. 3 here is shown, it is good also as a structure provided with the refrigerating-cycle apparatus of Embodiment 1 shown in FIG.

  As shown in FIG. 4, the refrigeration cycle apparatus according to Embodiment 3 includes an outdoor unit 100, indoor units 200a and 200b, and a liquid pipe 50 and a gas pipe 51 that connect the pipes. This is a multi-type air conditioner in which a plurality of indoor units are connected to the outdoor unit 100.

  In the outdoor unit 100, there are provided a first compressor 1 for compressing the refrigerant gas, an outdoor heat exchanger 4, and an expander 3 a that decompresses the refrigerant into a two-phase wet steam, A part of the main refrigerant circuit 6 is configured by being sequentially connected by piping. The main refrigerant circuit 6 includes a second compressor 3b that is coaxially connected to the expander 3a and is driven by power collected by the expander 3a. In FIG. 4, a portion excluding a later-described bypass circuit 7 and injection circuit 7 a is referred to as a main refrigerant circuit 6.

  In the outdoor unit 100, a bypass circuit 7 that bypasses the expander 3a is provided. The bypass circuit 7 has an internal heat exchanger 5 a and an on-off valve 10, and the refrigerant flowing out of the outdoor heat exchanger 4 is supplied to the expander 3 a through the high-pressure side of the internal heat exchanger 5 a and the on-off valve 10. Join the exit. Further, an injection branched from the internal heat exchanger 5a and the on-off valve 10 in the bypass circuit 7 and joined to the discharge side of the second compressor 3b via the on-off valve 12 and the low-pressure side of the internal heat exchanger 5a. A circuit 7a is provided. A gas-liquid separator 8 is installed at the outlet of the expander 3a, and the gas refrigerant separated by the gas-liquid separator 8 is sucked into the suction portion of the first compressor 1. Further, the liquid refrigerant separated by the gas-liquid separator 8 flows to the indoor heat exchangers 2a and 2b in the case of cooling, and to the outdoor heat exchanger 4 in the case of heating.

  The expander 3a and the second compressor 3b are coaxially connected as described above, and form an integral structure as the sub-compressor-integrated expander 3 as in the first embodiment. In the main refrigerant circuit 6, the suction side of the second compressor 3 b is installed in parallel with the suction side of the first compressor 1, and the discharge side of the second compressor 3 b is the compression chamber of the first compressor 1. It is connected to an injection port provided in communication. For example, carbon dioxide that is in a supercritical state at a critical temperature (about 31 ° C.) or higher is sealed as a refrigerant.

  The indoor units 200a and 200b include indoor heat exchangers 2a and 2b that constitute a part of the main refrigerant circuit 6, and indoor expansion valves 9a and 9b.

The operation of the refrigeration cycle apparatus configured as described above will be described.
In normal heating operation, power recovery is performed using only the main refrigerant circuit 6. In other words, the bypass flow rate is 0%, the on-off valve 11 is opened, and the on-off valve 10 and the on-off valve 12 are closed.
The high-pressure gas refrigerant discharged from the first compressor 1 is sent to the indoor units 200a and 200b via the four-way valve 20 and the gas pipe 51. The high-pressure gas refrigerant sent to the indoor units 200a, 200b exchanges heat with the indoor air in the indoor heat exchangers 2a, 2b of the indoor units 200a, 200b to dissipate heat and become high-pressure medium-temperature refrigerant. The high-pressure medium temperature refrigerant passes through the indoor expansion valves 9 a and 9 b and is decompressed, and then flows into the outdoor unit 100 through the liquid pipe 50.

  The refrigerant flowing into the outdoor unit 100 passes through the check valve 16c, then flows into the second expander 3a, where it is further decompressed, and then flows into the gas-liquid separator 8. The liquid refrigerant separated by the gas-liquid separator 8 flows into the outdoor heat exchanger 4 through the check valve 16b. Then, the low-pressure refrigerant flowing into the outdoor heat exchanger 4 evaporates by exchanging heat with the outdoor air, becomes a low-pressure gas refrigerant, passes through the four-way valve 20, and returns to the suction portion of the first compressor 1. . Further, the gas refrigerant separated by the gas-liquid separator 8 is branched into two, one is compressed by the second compressor 3b and then sucked into the compression chamber of the first compressor 1, and the other is The refrigerant that has returned through the valve 20 joins and is sucked into the suction portion of the first compressor 1.

  Here, as in the heating operation under the low outside air condition, the case where the outlet temperature of the radiator 2 is relatively low and the performance improvement effect by power recovery is small, but a large heating capacity is required will be described. In this case, the refrigerant is supplied to both the main refrigerant circuit 6 and the bypass circuit 7, and an operation for performing both power recovery by the expander 3a and heat exchange by the internal heat exchanger 5a is performed. The refrigerant flow in this operation is basically the same as in the second embodiment.

Hereinafter, an operation for performing both power recovery and heat exchange by the internal heat exchanger 5a will be described. In this operation, since the refrigerant flows through both the expander 3a and the bypass circuit 7, all of the on-off valves 10 to 12 are set to an appropriate opening degree.
The high-temperature and high-pressure gas refrigerant discharged from the first compressor 1 passes through the gas pipe 51 and is sent to the indoor heat exchangers 2a and 2b as the radiators of the indoor units 200a and 200b. The high-pressure gas refrigerant sent to the indoor heat exchangers 2a and 2b exchanges heat with the indoor air to dissipate heat and become high-pressure medium-temperature refrigerant, and then the flow rate is controlled by the on-off valve 11 and flows into the expander 3a. . The refrigerant that has flowed into the expander 3 a is decompressed to a low-pressure and low-temperature gas-liquid two-phase refrigerant while recovering power, and flows into the gas-liquid separator 8. The gas-liquid two-phase refrigerant that has flowed into the gas-liquid separator 8 is separated into a gas refrigerant and a liquid refrigerant by the gas-liquid separator 8, and the liquid refrigerant flows into the outdoor heat exchanger 4 through the check valve 16b. Then, the low-pressure two-phase refrigerant flowing into the outdoor heat exchanger 4 evaporates by exchanging heat with the outdoor air, becomes low-pressure gas refrigerant, passes through the four-way valve 20, and returns to the suction portion of the first compressor 1. . Further, the gas refrigerant separated by the gas-liquid separator 8 is branched into two, one is compressed by the second compressor 3b and then sucked into the compression chamber of the first compressor 1, and the other is The refrigerant that has returned through the valve 20 joins and is sucked into the suction portion of the first compressor 1.

  On the other hand, a part of the refrigerant flowing out of the indoor heat exchangers 2a and 2b and going to the expander 3a flows into the bypass circuit 7. The refrigerant that has flowed into the bypass circuit 7 flows into the high-pressure side of the internal heat exchanger 5a, is cooled by exchanging heat with the low-pressure two-phase refrigerant on the low-pressure side of the internal heat exchanger 5a, and the dryness decreases. The refrigerant that has flowed out of the high pressure side of the internal heat exchanger 5a is decompressed by the on-off valve 10, and then merges with the refrigerant that has flowed out of the expander 3a of the main refrigerant circuit 6 and flows into the gas-liquid separator 8. The flow of the refrigerant after flowing into the gas-liquid separator 8 is the same as described above.

  A part of the refrigerant that has passed through the high-pressure side of the internal heat exchanger 5a flows into the injection circuit 7a and is reduced to a low-pressure low-temperature two-phase refrigerant by the on-off valve 12, and then the low-pressure side of the internal heat exchanger 5a. Flow into. The low-pressure two-phase refrigerant flowing into the low-pressure side of the internal heat exchanger 5a evaporates by exchanging heat with the refrigerant passing through the high-pressure side, and then compressed in the compression process from the injection port communicating with the compression chamber of the first compressor 1 It is injected into the room as injection gas. In the configuration of FIG. 4, the refrigerant merges with the refrigerant from the expander 3 a and is injected into the compression chamber of the first compressor 1.

  Here, the on-off valve 12 is a pressure reducing valve whose internal opening degree (flow resistance) is variable, and the opening degree is controlled so that the refrigerant state at the low-pressure side outlet of the internal heat exchanger 5a has a predetermined superheat degree. Is done. The degree of superheat at the low-pressure side outlet of the internal heat exchanger 5a is defined by the temperature difference between the low-pressure side outlet refrigerant temperature in an overheated state and the two-phase refrigerant temperature at the outlet of the on-off valve 12.

  Next, a case where power recovery by the expander 3a is performed in the cooling operation will be described. The high-temperature and high-pressure gas refrigerant discharged from the first compressor 1 dissipates heat in the outdoor heat exchanger 4 and flows into the expander 3a. The refrigerant that has flowed into the expander 3a is decompressed to a low-pressure and low-temperature gas-liquid two-phase refrigerant while recovering power during expansion, evaporates in the indoor heat exchangers 2a and 2b, and flows into the first compressor 1 and the second compressor 3b. Return to suction side. The rotation speed of the second compressor 3b is the same as that of the expander 3a, and the high pressure (injection pressure) of the second compressor 3b is set so that the recovered power of the expander 3a matches the power consumption of the second compressor 3b. Determined.

  According to the third embodiment, even in an air conditioner that performs heating / cooling operation by switching the four-way valve 20, the same effects as those of the first and second embodiments can be obtained.

  In the first to third embodiments, the suction side of the second compressor 3b is installed in parallel with the suction side of the first compressor 1, and the discharge side of the second compressor 3b is in the middle of compression of the first compressor 1. Although the structure connected to the compression chamber is shown, the present invention is not limited to this, and the first compressor 1 and the second compressor 3b are arranged completely in parallel, and the discharge side of the second compressor 3b is the first compressor 1. It is good also as a structure which merges with the discharge side. In this case, the excluded volume of the second compressor 3 b is designed to be sufficiently smaller than the excluded volume of the first compressor 1.

  DESCRIPTION OF SYMBOLS 1 1st compressor, 2 radiator, 2a, 2b indoor heat exchanger, 3 subcompressor integrated expander, 3a expander, 3b 2nd compressor, 4 evaporator (outdoor heat exchanger), 5 internal heat Exchanger, 5a Internal heat exchanger, 6 Main refrigerant circuit, 7 Bypass circuit, 7a Injection circuit, 8 Gas-liquid separator, 9a, 9b Indoor expansion valve, 10 Open / close valve, 11 Open / close valve, 12 Open / close valve, 16a-16d Check valve, 20 four-way valve, 50 liquid pipe, 51 gas pipe, 100 outdoor unit, 200a, 200b indoor unit, 307 Oldham ring, 308 shaft, 308b crank part, 309a, 309b balance weight, 310 airtight container, 351 expander Fixed scroll, 351a spiral teeth, 351b expander bearing, 352 expander swing scroll, 352a expander side vortex Teeth, 361 second compressor fixed scroll, 361a spiral tooth, 361b bearing portion for the second compressor, 362 second compressor orbiting scroll, 362a compressor side spiral tooth.

Claims (5)

A first compressor, a radiator, an expander, and an evaporator are sequentially connected by piping, and are driven by the power recovered by the expander, and receive a part of the refrigerant from the evaporator toward the first compressor. A main refrigerant circuit comprising a second compressor for compressing
A bypass circuit that bypasses the expander and includes an internal heat exchanger and a flow control valve;
The internal heat exchanger depressurizes the high-pressure refrigerant flowing out of the radiator and flowing into the bypass circuit, and a part of the refrigerant flowing out of the radiator outlet or the internal heat exchanger outlet with the flow control valve. A refrigeration cycle apparatus characterized by exchanging heat with the low-pressure two-phase refrigerant after being heated.   2. The refrigeration cycle apparatus according to claim 1, further comprising an injection circuit that injects a low-pressure side refrigerant after heat exchange in the internal heat exchanger into a compression chamber in the middle of compression of the first compressor.   3. The refrigeration cycle apparatus according to claim 1, wherein the refrigerant flows through both the main refrigerant circuit and the bypass circuit during heating operation at a low outside air temperature. 4.   4. The refrigeration cycle apparatus according to claim 1, wherein each of the expander and the second compressor has a scroll type structure. 5.   The refrigeration cycle apparatus according to any one of claims 1 to 4, wherein the refrigerant is carbon dioxide.

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