CN116438413A

CN116438413A - Refrigeration cycle device

Info

Publication number: CN116438413A
Application number: CN202080106920.5A
Authority: CN
Inventors: 村田健太
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2020-11-13
Filing date: 2020-11-13
Publication date: 2023-07-14
Also published as: EP4246057A1; EP4246057A4; WO2022102077A1; JP7433470B2; JPWO2022102077A1; US20230358446A1

Abstract

The following refrigeration cycle device was obtained: the refrigerant flow path is configured such that air and refrigerant are in convection in both the cooling case and the heating case, and the low-pressure two-phase refrigerant flows through the liquid pipe, whereby the amount of necessary refrigerant can be reduced. The device comprises: an outdoor unit (1) having a compressor (5), a four-way valve (6) for switching between cooling operation and heating operation, an outdoor heat exchanger (7), and an outdoor expansion valve (9); an indoor unit (2) having an indoor heat exchanger (12) and an indoor expansion valve (14); a gas pipe (3) and a liquid pipe (4) that connect the outdoor unit (1) and the indoor unit (2); and at least one of a 1 st bridge circuit (10) and a 2 nd bridge circuit (15), wherein the 1 st bridge circuit (10) is configured to make the flow of the refrigerant flowing through the outdoor heat exchanger (7) in the same direction in both the cooling operation and the heating operation by using a plurality of flow path opening/closing units (11), and the 2 nd bridge circuit (15) is configured to make the flow of the refrigerant flowing through the indoor heat exchanger (12) in the same direction in both the cooling operation and the heating operation by using a plurality of flow path opening/closing units (16).

Description

Refrigeration cycle device

Technical Field

The present invention relates to a refrigeration cycle apparatus that performs air conditioning, and more particularly, to a refrigeration cycle apparatus configured to be capable of switching between a cooling operation and a heating operation.

Background

In many of the conventional refrigeration cycle apparatuses for performing air conditioning, a cooling operation and a heating operation can be selected by switching the flow direction of a refrigerant.

In recent years, in order to reduce the global warming potential (Global Warming Performance, GWP) of a refrigerant enclosed in a refrigeration cycle apparatus, the use of a non-azeotropic refrigerant mixture in which a plurality of refrigerants having different boiling points are mixed has been studied.

Zeotropic mixed refrigerants have the characteristic that the saturation temperature varies during the condensation process and the evaporation process. Therefore, in the heat exchanger that exchanges heat between air and refrigerant, the flow direction of air and refrigerant is designed such that the inlet side of air exchanges heat with the outlet side of refrigerant and the inlet side of refrigerant exchanges heat with the outlet side of air. That is, the heat exchanger is designed so that the heat exchanger as a whole is easily convected to ensure a temperature difference between air and refrigerant.

However, in the refrigeration cycle apparatus in which the flow direction of the refrigerant is switched between the cooling operation and the heating operation, when any one of the flow directions of the cooling and heating operation is selected, the refrigerant and the air flow in parallel, and the performance of the heat exchanger is degraded.

In order to avoid such a problem, the following methods are known: by employing a bridge circuit using a plurality of check valves, the refrigerant inlet and the refrigerant outlet of the heat exchanger are not reversed during cooling and heating, and both the refrigerant and air become convection during cooling and heating (for example, patent document 1).

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 9-178283

Disclosure of Invention

Problems to be solved by the invention

However, in the refrigeration cycle apparatus configured as in the prior art document, since the high-pressure refrigerant condensed and liquefied is flowed through the liquid pipe between the outdoor heat exchanger and the indoor heat exchanger in both the cooling operation and the heating operation, there is a problem that the amount of the refrigerant required increases.

Further, when the cooling operation is selected, the expansion valve on the indoor side needs to be completely closed, and when the heating operation is selected, the expansion valve on the outdoor side needs to be completely closed, and therefore, the opening and closing operations of the expansion valve are frequent, and there is a problem that durability is deteriorated.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a refrigeration cycle apparatus configured such that at least one of an outdoor heat exchanger and an indoor heat exchanger is convection-type and the amount of necessary refrigerant can be reduced, both in the case of cooling and in the case of heating.

Means for solving the problems

In order to achieve the above object, a refrigeration cycle device according to the present invention includes: an outdoor unit having a compressor, a four-way valve for switching between a cooling operation and a heating operation, an outdoor heat exchanger, and an outdoor expansion valve; an indoor unit having an indoor heat exchanger and an indoor expansion valve; and a gas pipe and a liquid pipe that connect the outdoor unit and the indoor unit to form a refrigerant circuit in which the zeotropic refrigerant mixture is sealed, wherein the refrigeration cycle device has at least one of a 1 st bridge circuit and a 2 nd bridge circuit, the 1 st bridge circuit is housed in the outdoor unit, the flow of the zeotropic refrigerant mixture flowing through the outdoor heat exchanger is configured to be in the same direction in both the cooling operation and the heating operation by using a plurality of flow path opening/closing means, the flow path opening/closing means provided in the flow path connecting the outlet side of the outdoor heat exchanger and the liquid pipe is an outdoor expansion valve, the 2 nd bridge circuit is configured to be in the same direction in both the cooling operation and the heating operation by using a plurality of flow path opening/closing means, and the flow path opening/closing means provided in the flow path connecting the outlet side of the indoor heat exchanger and the liquid pipe is an indoor expansion valve.

Effects of the invention

The refrigeration cycle apparatus of the present invention can use the 1 st bridge circuit and the 2 nd bridge circuit to make the outdoor heat exchanger and the indoor heat exchanger be convection in both cooling and heating, and therefore, even if a non-azeotropic refrigerant is applied, the temperature difference between the air and the refrigerant is sufficiently ensured from the inlet to the outlet of the heat exchanger, thereby heat exchange can be efficiently performed, and the performance of the refrigeration cycle apparatus is improved.

Since the refrigerant flowing through the liquid pipe is in a low-pressure two-phase state in both the cooling operation and the heating operation, there is no operation state in which the liquid pipe is filled with the liquid refrigerant, and therefore, the amount of refrigerant enclosed in the refrigerant circuit can be reduced.

Drawings

Fig. 1 is a refrigerant circuit configuration diagram of a refrigeration cycle apparatus according to embodiment 1.

Fig. 2 is a schematic diagram showing a relationship between a refrigerant flow path and a flow direction of air in the outdoor heat exchanger according to embodiment 1.

Fig. 3 is a graph showing an example of a temperature change from the inflow of the refrigerant and the air to the outflow thereof.

Fig. 4 is a graph showing an example of a temperature change from the inflow of the refrigerant and the air into the evaporator to the outflow thereof.

Fig. 5 is a refrigerant circuit configuration diagram of the refrigeration cycle apparatus according to embodiment 2.

Fig. 6 is a cross-sectional view showing a flow path structure of the indoor bridge circuit according to embodiment 2 from the indoor heat exchanger outlet toward the liquid pipe.

Fig. 7 is a refrigerant circuit configuration diagram of the refrigeration cycle apparatus according to embodiment 3.

Fig. 8 is a refrigerant circuit configuration diagram of the refrigeration cycle apparatus according to embodiment 4.

Detailed Description

A refrigeration cycle apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will be omitted.

Embodiment 1

< construction of refrigeration cycle device >

Fig. 1 is a refrigerant circuit configuration diagram of a refrigeration cycle apparatus according to embodiment 1 of the present invention. As shown in fig. 1, in a refrigeration cycle apparatus 100, an outdoor unit 1 and an indoor unit 2 are connected by an air pipe 3 and a liquid pipe 4 to form a single refrigerant circuit. The refrigerant circuit is filled with R407C, which is a mixed refrigerant of 3 HFC refrigerants having different boiling points. The refrigerant to be sealed is not limited to this, and may be, for example, a mixed refrigerant of R1234yf and R32 as HFO refrigerant. In addition, a mixed refrigerant containing an HC refrigerant such as R290 or a natural refrigerant such as CO2 as one of the components may be used.

The outdoor unit 1 includes a compressor 5, a four-way valve 6, an outdoor heat exchanger 7, an outdoor fan 8, and an outdoor bridge circuit 10, the operation capacity of which can be adjusted. An outdoor inlet header 17a and an outdoor outlet header 17b are provided in front of and behind the outdoor heat exchanger 7, and the other end side of each header is connected to the outdoor bridge circuit 10. The outdoor fan 8 attached to the outdoor heat exchanger 7 changes the amount of air blown toward the outdoor heat exchanger 7, thereby adjusting the amount of heat exchange between the refrigerant and the outdoor air.

The outdoor bridge circuit 10 has 4 inlets and outlets in total from one end of the outdoor inlet header 17a, one end of the outdoor outlet header 17b, one end of the four-way valve 6, and the connection end of the liquid pipe 4, and is composed of 3

check valves

11a, 11b, 11c and an outdoor expansion valve 9. The outdoor expansion valve 9 is configured to be capable of moving the valve body by a pulse motor or the like, and is capable of continuously adjusting the opening degree from a fully closed state to a fully open state. The outdoor bridge circuit 10 constitutes a refrigerant flow path in the following manner: in both the cooling operation in which the refrigerant flows in from the four-way valve 6 and the heating operation in which the refrigerant flows in from the liquid pipe 4, the refrigerant flows out toward the indoor inlet header 17 a.

The indoor unit 2 incorporates an indoor heat exchanger 12, an indoor blower 13 for adjusting the amount of heat exchange between the refrigerant flowing through the indoor heat exchanger 12 and the indoor air, and an indoor bridge circuit 15. Further, an indoor inlet header 18a and an indoor outlet header 18b are provided at both ends of the indoor heat exchanger 12, and the other end side of each header is connected to the indoor bridge circuit 15.

The indoor bridge circuit 15 has 3

check valves

16a, 16b, 16c and an indoor expansion valve 14. The indoor expansion valve 14 can be continuously adjusted in opening degree from the fully closed state to the fully open state, similarly to the outdoor expansion valve 9. The indoor bridge circuit 15 constitutes a refrigerant flow path in the following manner: in both the cooling operation in which the refrigerant flows in from the liquid pipe 4 and the heating operation in which the refrigerant flows in from the gas pipe 3, the refrigerant flows through the indoor heat exchanger 12 from the indoor inlet header 18a side.

Fig. 2 is a schematic diagram showing a relationship between the refrigerant flow path of the outdoor heat exchanger 7 and the flow direction of air. The outdoor heat exchanger 7 is composed of a plurality of heat transfer tubes 19 and a plurality of stacked fins 20. The heat transfer pipe 19 is a circular pipe made of copper, and in the present embodiment, is arranged in 6 layers in the vertical direction and is arranged in 4 rows in the air flow direction. The fins 20 are thin plates made of aluminum and having a thickness of about 0.1mm, and are stacked at intervals of 1 to 2 mm.

The refrigerant flowing into the outdoor heat exchanger 7 branches off at the outdoor inlet header 17a and flows into the outdoor heat exchanger 7 while traveling in the column direction while reciprocating in the stacking direction of the fins 20, and merges at the outdoor outlet header 17 b. On the other hand, since the flow of outdoor air generated by the outdoor fan 8, not shown, is directed from the right side to the left side of the paper surface, the air and the refrigerant exchange heat on the inlet side and the outlet side, respectively, and are so-called convection. In the indoor heat exchanger 12, the refrigerant inlet and the air outlet are in thermal contact with each other, and the refrigerant outlet and the air inlet are in thermal contact with each other. Next, refrigerant control during cooling operation and heating operation will be described.

< cooling operation >

In the cooling operation, the four-way valve 6 shown in fig. 1 sets the internal flow path to the solid line direction. The refrigerant discharged in the compressor 5 flows into the outdoor bridge circuit 10 via the four-way valve 6. The refrigerant flowing into the outdoor bridge circuit 10 flows from the inlet header 17a into the indoor heat exchanger 12 through the check valve 11 a. At this time, the outlet side of the check valve 11b is pressurized to a high pressure and closed. The refrigerant condensed and liquefied by heat radiation to the outdoor air in the indoor heat exchanger 12 flows into the outdoor bridge circuit 10 again through the outdoor outlet header 17b, and is decompressed by the outdoor expansion valve 9 to become a low-pressure two-phase refrigerant. The opening degree of the outdoor expansion valve is controlled, for example, so that the temperature of the discharge gas refrigerant of the compressor 5 becomes a target value.

The refrigerant in a low-pressure two-phase state flowing out of the outdoor unit 1 flows into the indoor unit 2 through the liquid pipe 4. In the indoor unit 2, the refrigerant flows into the indoor bridge circuit 15, and flows from the indoor inlet header 18a into the indoor heat exchanger 12 through the check valve 16 c. At this time, the indoor expansion valve 14 is closed so that the refrigerant does not circulate.

The refrigerant flowing into the indoor heat exchanger 12 is heated by the indoor air and evaporated to become low-pressure gas refrigerant, which flows out from the indoor outlet header 18 b. The refrigerant flowing out of the indoor heat exchanger 12 flows into the indoor bridge circuit 15 again, and flows out of the indoor unit 2 through the check valve 16 b.

The refrigerant flowing out of the indoor unit 2 flows through the gas pipe 3, returns to the outdoor unit 1 again, and is sucked into the compressor 5 through the four-way valve 6. In this way, the non-azeotropic refrigerant sealed in the refrigeration cycle apparatus 100 circulates in the refrigerant circuit to perform the cooling operation.

As described above, in the cooling operation, the refrigerant condensed in the outdoor heat exchanger 7 is depressurized by the outdoor expansion valve 9, and therefore, the refrigerant flowing through the liquid pipe 4 is a low-pressure two-phase refrigerant. The low-pressure two-phase refrigerant has a relatively low temperature, and moisture in the air may be condensed when it contacts the outdoor air, so that it is necessary to sufficiently insulate the heat, while the low-pressure two-phase refrigerant has a lower density than the high-pressure liquid refrigerant condensed in the outdoor heat exchanger 7, so that the amount of refrigerant to be enclosed in the refrigerant circuit can be reduced.

Fig. 3 is a graph showing an example of a temperature change from the inflow of the refrigerant and the air to the outflow of the refrigerant and the air, and fig. 4 is a graph showing an example of a temperature change from the inflow of the refrigerant and the air to the outflow of the refrigerant and the air to the evaporator. In fig. 3 and 4, the vertical axis represents temperature, and the horizontal axis represents the relative position of each of the refrigerant and air on the path from the inlet to the outlet of the heat exchanger. The condenser and the evaporator shown in fig. 3 and 4 are configured by convection, and therefore, the refrigerant circulates from the left end a to the right end B of the horizontal axis, and the air circulates from the right end B to the left end a. The section C of the horizontal axis indicates that the refrigerant is in a gas-liquid two-phase state.

Fig. 3 shows temperature changes of the refrigerant and the air in the outdoor heat exchanger 7 that operates as a condenser during the cooling operation in this embodiment. The refrigerant flowing through the outdoor heat exchanger 7 flows in a high-temperature gas state at about 70 ℃, is cooled by air, and starts to liquefy at around 50 ℃. Since the refrigerant is a non-azeotropic refrigerant, the temperature is gradually reduced in the two-phase region C, and the temperature is further reduced after complete liquefaction. The refrigerant is cooled to a temperature close to 35 ℃ which is the air inlet temperature on the outlet side of the outdoor heat exchanger 7, and after the degree of supercooling is ensured, the refrigerant flows out of the outdoor heat exchanger 7. On the other hand, since the air does not undergo a phase change during heat exchange, the temperature of the air is monotonically increased by heating from the refrigerant after flowing into the outdoor heat exchanger 7 at 35 ℃.

In this way, in the condenser configured by convection, the air at a sufficiently high temperature on the air outlet side exchanges heat with the high-temperature gas refrigerant on the refrigerant inlet side, and the supercooled liquid refrigerant on the refrigerant outlet side exchanges heat with the outdoor air on the air inlet side, so that even after the refrigerant is in a liquid single-phase state from a gas-liquid two-phase state, a temperature difference with the air is sufficiently ensured, and heat exchange can be performed efficiently.

Fig. 4 shows a temperature change of the indoor heat exchanger 12 serving as an evaporator in the cooling operation in this embodiment. The refrigerant flowing into the indoor heat exchanger 12 is in a low-pressure two-phase state at about 10 ℃ at the refrigerant inlet a, and undergoes heat exchange with indoor air, and at the same time, gradually increases in temperature, and flows out of a section C indicating the two-phase state. Then, the air is further heat-exchanged with the indoor air, and flows out through the refrigerant outlet B in a low-pressure gas state having a predetermined degree of superheat.

On the other hand, the air is cooled by the refrigerant at a temperature of about 27 ℃ which is room temperature at the air inlet B, and is low-temperature air at about 15 ℃ at the air outlet a. The low-temperature air is sent out into the room to perform cooling operation.

In this way, in the evaporator configured by convection, heat exchange is performed between the lowest temperature refrigerant inlet and the air outlet in terms of the characteristics of the zeotropic refrigerant mixture, and therefore, air can be cooled efficiently, and heat exchange is performed between indoor air still at a high temperature on the side of the refrigerant outlet and the refrigerant, and therefore, a sufficient degree of superheat is obtained.

< heating operation >

In the heating operation, the four-way valve 6 shown in fig. 1 sets the internal flow path to the direction of the broken line. The refrigerant discharged from the compressor 5 flows out of the outdoor unit 1 through the four-way valve 6. The refrigerant flowing out of the outdoor unit 1 flows into the indoor unit 2 via the gas pipe 3, and first flows into the indoor bridge circuit 15. In the indoor bridge circuit 15, the refrigerant flows out of the indoor bridge circuit through the check valve 16a and into the indoor heat exchanger 12 from the indoor inlet header 18 a. At this time, the outlet side of the check valve 16b is pressurized to a high pressure and is closed.

In the indoor heat exchanger 12, the refrigerant radiates heat to the indoor air, condenses and liquefies, and flows out of the indoor heat exchanger 12 from the indoor outlet header 18 b. The refrigerant flowing out of the indoor heat exchanger 12 flows into the indoor bridge circuit 15 again, is depressurized by the indoor expansion valve 14, and is brought into a low-pressure two-phase state.

The refrigerant in the low-pressure two-phase state flows out of the indoor unit 2 and flows into the outdoor unit 1 through the liquid pipe 4. In the outdoor unit 1, the refrigerant flows from the outdoor inlet header 17a into the outdoor heat exchanger 7 through the check valve 11c provided in the outdoor bridge circuit 10.

In the outdoor heat exchanger 7, the refrigerant is heated by the outdoor air to be in a low-pressure gas state, and flows into the outdoor bridge circuit 10 again through the outdoor outlet header 17 b. At this time, the outdoor expansion valve 9 is closed, and the refrigerant flows out of the outdoor bridge circuit 10 through the check valve 11 b. The refrigerant is then sucked again into the compressor 5 via the four-way valve 6.

As described above, according to the refrigeration cycle apparatus 100 of embodiment 1, the refrigerant flowing through the outdoor heat exchanger 7 and the indoor heat exchanger 12 is caused to flow in convection with air both in the case of the cooling operation and in the case of the heating operation. This ensures a sufficient temperature difference between the air and the refrigerant from the inlet to the outlet of the heat exchanger, thereby enabling efficient heat exchange and improving the performance of the refrigeration cycle apparatus. This effect is remarkably exhibited when a non-azeotropic refrigerant mixture is used.

In this embodiment, the bridge circuit is housed in both the outdoor unit 1 and the indoor unit 2, but when the heat exchanger is provided in either one of them, the heat exchange efficiency on the side having the bridge circuit is improved, and the performance improvement effect of the refrigeration cycle apparatus is obtained.

Further, according to the refrigeration cycle apparatus of this embodiment, the refrigerant flowing through the liquid pipe 4 is in the low-pressure two-phase state in both the cooling operation and the heating operation, and there is no operating state in which the liquid pipe 4 is filled with the liquid refrigerant, so that the amount of refrigerant enclosed in the refrigerant circuit can be reduced.

Embodiment 2

Fig. 5 is a refrigerant circuit configuration diagram of a refrigeration cycle apparatus 101 according to embodiment 2 of the present invention. In the refrigeration cycle apparatus 100 according to embodiment 1, the refrigeration cycle apparatus 101 is provided with a check valve 11d in a flow path of the outdoor bridge circuit 110 in which the outdoor expansion valve 9 is disposed. The check valve 16d is provided in the flow path of the indoor bridge circuit 115 where the indoor expansion valve 14 is disposed, and the rectifier 20 is provided upstream of the indoor expansion valve 14.

In the outdoor bridge circuit 110, the check valve 11d mechanically blocks the flow path including the outdoor expansion valve 9 so that the refrigerant flowing from the liquid pipe 4 into the outdoor unit 1 does not flow to the outlet side of the indoor heat exchanger 12 during the heating operation. Thus, the outdoor expansion valve 9 is not completely closed during the heating operation, and a refrigerant circuit during the heating operation is formed.

In many cases, the complete closing operation of the expansion valve is accompanied by a plurality of collisions between the valve body and the valve seat, and therefore, particularly under operating conditions in which cooling and heating are alternately repeated, wear of the expansion valve is promoted. According to this embodiment, the number of times of opening degree control of the outdoor expansion valve 9 is reduced, and aged deterioration of the outdoor expansion valve 9 can be suppressed.

In the same manner, the indoor bridge circuit 115 also mechanically blocks the flow of refrigerant from the liquid pipe 4 toward the outlet side of the indoor heat exchanger 12 during the cooling operation, and thus, the outdoor expansion valve 14 does not need to be completely closed during the cooling operation. This reduces the number of times of opening control of the indoor expansion valve 14, and can suppress the aged deterioration of the indoor expansion valve 14.

Fig. 6 is a cross-sectional view showing a flow path structure having the indoor expansion valve 14 in the indoor bridge circuit 115. The rectifier 20 has a rectifier portion 21 formed of a metal mesh or foamed metal inside. Even when bubbles discontinuously flow through the inlet of the expansion valve 14, such as in the case where the refrigerant distribution is unstable immediately after the start of the heating operation in the refrigeration cycle apparatus 100, the flow rectifier 20 is converted into a uniform bubble flow by the flow rectifier 21. Thus, irregular vibration or refrigerant flow sound is not generated in the indoor expansion valve 14, and comfort of the indoor environment is not impaired by noise from the refrigeration cycle apparatus.

As described above, according to the refrigeration cycle apparatus 101 of embodiment 2, the same effects as those of the refrigeration cycle apparatus 100 of embodiment 1 can be exhibited. Further, since the check valve 11d and the check valve 16d are provided, the number of times of opening degree control of the outdoor expansion valve 9 and the indoor expansion valve 14 is reduced, and the aged deterioration of the expansion valves can be suppressed. Further, since the rectifier 20 is provided, refrigerant flowing noise and irregular vibration are not generated in the room, and a comfortable air conditioning environment can be provided.

Embodiment 3

Fig. 7 is a refrigerant circuit configuration diagram of the refrigeration cycle apparatus 102 according to embodiment 3 of the present invention. In contrast to the refrigeration cycle apparatus 100 according to embodiment 1, in the refrigeration cycle apparatus 102, the indoor bridge circuit 215 is not built in the indoor unit 2, but is provided separately. The

indoor units

2a, 2b, 2c are connected in parallel to the indoor bridge circuit 215, respectively, and have on-off valves 22a, 22b, 22c capable of shutting off the flow of refrigerant on the refrigerant inlet sides of the indoor heat exchangers 12a, 12b, 12 c.

The refrigeration cycle apparatus 102 is a multi-room air conditioner, and the

indoor units

2a, 2b, and 2c perform air temperature control of the respective rooms in which the air conditioner is installed. At this time, as in embodiment 1 or embodiment 2, when each of the

indoor units

2a, 2b, and 2c has the indoor bridge circuit 15, the air conditioning capacity cannot be adjusted for each room during the cooling operation. Therefore, in the case where there is an imbalance in the air conditioning load between rooms, an excessive/insufficient air conditioning capacity is generated.

Since the refrigeration cycle apparatus 102 includes the on-off valves 22a, 22b, and 22c for each indoor unit, when the air conditioning capacity of a specific room is excessive during the cooling operation or the heating operation, the on-off valves are temporarily closed, so that the air conditioning capacity of the room can be prevented from being exhibited. Thus, even when a plurality of indoor units are connected, the air conditioning capacity control can be performed independently for each indoor unit, and a comfortable air conditioning environment can be provided.

Further, since the refrigeration cycle apparatus 102 is configured such that a plurality of indoor units are connected to the 1-indoor bridge circuit 215, the number of components such as check valves constituting the bridge circuit is reduced, and the manufacturing cost is reduced.

As described above, according to the refrigeration cycle apparatus 102 of embodiment 3, even when a plurality of indoor units are connected as a multi-room air conditioner, the same effects as those of the refrigeration cycle apparatus 100 of embodiment 1 can be exhibited. That is, the outdoor heat exchanger 7 and the indoor heat exchangers 12a, 12b, and 12c can be made to be convection-type during both cooling and heating, and the refrigerant flowing through the liquid pipe 4 can be made to be a two-phase refrigerant having a low density during both cooling and heating. Further, since the air conditioning capacity can be adjusted for each indoor unit, a comfortable air conditioning environment can be provided even when there is an imbalance in the air conditioning load between rooms.

Further, since the refrigerant circuit is configured by using 1 indoor bridge circuit 215 with respect to the plurality of

indoor units

2a, 2b, and 2c, the number of components such as check valves that configure the refrigerant circuit is reduced, and the manufacturing cost can be reduced.

Embodiment 4

Fig. 8 is a refrigerant circuit configuration diagram of the refrigeration cycle apparatus 103 according to embodiment 4 of the present invention. In the refrigeration cycle apparatus 103, the expansion means incorporated in the indoor bridge circuit 315 is a mechanically fixed throttle 31 such as a capillary tube, with respect to the refrigeration cycle apparatus 100 of embodiment 1. The outdoor expansion valve 9 is not built in the outdoor bridge circuit 10, but is disposed between one end of the outdoor bridge circuit 10 and the liquid pipe 4.

In the indoor bridge circuit 315, the fixed throttle 31 disposed in series with the flow path of the check valve 16d is designed to reduce the flow resistance of the high-pressure liquid refrigerant flowing out of the indoor heat exchanger 12 to a level of two phases of gas and liquid at the time of heating operation. During the heating operation, the refrigerant in the gas-liquid two-phase state by the fixed throttle 31 flows into the outdoor unit 1 through the liquid pipe 4.

The refrigerant flowing into the outdoor unit 1 is further depressurized by the outdoor expansion valve 9 and then flows into the outdoor bridge circuit 310. At this time, the opening degree of the outdoor expansion valve 9 is controlled so that the discharge gas temperature of the compressor 5 becomes a target value, for example. That is, in the refrigeration cycle apparatus 103 according to embodiment 4, the refrigerant flowing through the liquid pipe 4 is first depressurized to a two-phase state by the fixed throttle 31 disposed in the outdoor bridge circuit 315, and then depressurized to an appropriate pressure by the outdoor expansion valve 9.

The indoor bridge circuit 315 is constituted only by the

check valves

16a, 16b, 16c, 16d and the fixed throttle 31, and therefore, does not require a power supply and a signal for opening degree control. Therefore, it is not necessary to connect the electric wiring to the indoor bridge circuit 315, and therefore, restrictions on installation sites are reduced, and installation work is simplified.

Further, since the opening degree control is performed by the outdoor expansion valve 9 in both the cooling operation and the heating operation, the refrigerant flow rate can be controlled only by the control device of the expansion valve provided in the outdoor unit 1, and the component cost of the circuit and the like can be reduced.

As described above, the refrigeration cycle apparatus 103 according to embodiment 4 can exhibit the same effects as those of the refrigeration cycle apparatus 100 according to embodiment 1. That is, the outdoor heat exchanger 7 and the indoor heat exchanger 12 can be made to be both convection-type during cooling and heating, and the refrigerant flowing through the liquid pipe 4 can be made to be a two-phase refrigerant having a low density during cooling and heating.

Further, since the indoor bridge circuit 315 is formed only by mechanical components, no electric wiring is required, and installation and construction costs can be reduced.

In addition, since the refrigerant flow rate is adjusted by controlling the opening degree of the outdoor expansion valve 9 in both the cooling operation and the heating operation, it is not necessary to provide an expansion valve driving circuit on the indoor side, and the cost of electric components can be reduced.

The configuration shown in the above embodiment shows an example of the present invention, and can be combined with other known techniques, and a part of the configuration can be omitted or changed without departing from the scope of the present invention.

Description of the reference numerals

1: an outdoor unit; 2. 2a, 2b, 2c: an indoor unit; 3: an air pipe; 4: a liquid pipe; 5: a compressor; 6: a four-way valve; 7: an outdoor heat exchanger; 8: an outdoor blower; 9: an outdoor expansion valve; 10. 110, 310: an outdoor bridging loop; 11a, 11b, 11c, 11d: an outdoor check valve; 12. 12a, 12b, 12c: an indoor heat exchanger; 13. 13a, 13b, 13c: an indoor blower; 14: an indoor expansion valve; 15. 115, 215, 315: an indoor bridging loop; 16a, 16b, 16c, 16d: an indoor check valve; 17a: an outdoor inlet header; 17b: an outdoor outlet header; 18a: an indoor inlet header; 18b: an indoor outlet header; 20: a rectifier; 21: a rectifying unit; 22a, 22b, 22c: an opening/closing valve; 31: a fixed throttle; 100. 101, 102, 103: a refrigeration cycle device.

Claims

1. A refrigeration cycle apparatus, comprising:

an outdoor unit having a compressor, a four-way valve for switching between a cooling operation and a heating operation, an outdoor heat exchanger, and an outdoor expansion valve;

an indoor unit having an indoor heat exchanger and an indoor expansion valve; and

a gas pipe and a liquid pipe that connect the outdoor unit and the indoor unit to each other, thereby forming a refrigerant circuit in which a refrigerant is enclosed,

wherein, the liquid crystal display device comprises a liquid crystal display device,

the refrigeration cycle apparatus includes at least one of a 1 st bridge circuit and a 2 nd bridge circuit, wherein the 1 st bridge circuit is housed in the outdoor unit, and is configured such that a plurality of flow path opening/closing means are used to make the flow of the refrigerant flowing through the outdoor heat exchanger in the same direction in both the cooling operation and the heating operation, the flow path opening/closing means provided in a flow path connecting the outlet side of the outdoor heat exchanger and the liquid pipe is the outdoor expansion valve, and the 2 nd bridge circuit is configured such that a plurality of flow path opening/closing means are used to make the flow of the refrigerant flowing through the indoor heat exchanger in the same direction in both the cooling operation and the heating operation, and the flow path opening/closing means provided in a flow path connecting the outlet side of the indoor heat exchanger and the liquid pipe is the indoor expansion valve.

2. The refrigeration cycle apparatus according to claim 1, wherein,

the 1 st bridge circuit has a 1 st check valve, and the 1 st check valve is disposed in series with the outdoor expansion valve, and prevents the refrigerant from flowing during the heating operation.

3. The refrigeration cycle apparatus according to claim 1, wherein,

the 2 nd bridge circuit has a 2 nd check valve, and the 2 nd check valve is disposed in series with the indoor expansion valve, and prevents the flow of the refrigerant during the cooling operation.

4. A refrigeration cycle apparatus according to claim 1 to 3, wherein,

the 2 nd bridge circuit has a rectifying unit on an upstream side of the indoor expansion valve to make a flow state of the refrigerant uniform.

5. A refrigeration cycle apparatus, comprising:

a plurality of indoor units having an indoor heat exchanger and an electromagnetic valve;

a 1 st bridge circuit which is housed in the outdoor unit and is configured such that a plurality of flow path opening/closing means are used to make the flow of the refrigerant flowing through the outdoor heat exchanger in the same direction in both the cooling operation and the heating operation, and the flow path opening/closing means provided in a flow path connecting the outlet side of the outdoor heat exchanger and the liquid pipe is the outdoor expansion valve;

a 2 nd bridge circuit connected in parallel with the plurality of indoor units, the bridge circuit being configured to use a plurality of flow path opening/closing means to make the flow of the refrigerant flowing through the plurality of indoor units in the same direction in both the cooling operation and the heating operation, and to have an indoor expansion valve in a flow path connecting an outlet side of the plurality of indoor units and the liquid pipe; and

and a gas pipe and a liquid pipe that connect the outdoor unit and the 2 nd bridge circuit, thereby forming a refrigerant circuit in which a refrigerant is enclosed.

6. A refrigeration cycle apparatus, comprising:

an indoor unit having an indoor heat exchanger; and

the refrigeration cycle device comprises:

a 1 st bridge circuit which is housed in the outdoor unit and is configured to make the flow of the refrigerant flowing through the outdoor heat exchanger in the same direction in both the cooling operation and the heating operation by using a plurality of flow path opening/closing means; and

and a 2 nd bridge circuit configured to make the flow of the refrigerant flowing through the indoor unit in the same direction in both the cooling operation and the heating operation by using a plurality of flow path opening/closing means, the bridge circuit having a fixed throttle portion connected in series with the flow path opening/closing means provided in a flow path connecting the outlet side of the indoor unit and the liquid pipe.

7. A refrigeration cycle apparatus according to claim 1 to 6, wherein,

the refrigerant is a non-azeotropic refrigerant mixture composed of 2 or more kinds of refrigerants having different boiling points.