Air Conditioning System

Abstract

To enable heat recovery by using an auxiliary heat exchanger during a defrosting operation in an air conditioning system including the heat recovery auxiliary heat exchanger.SOLUTION: An air conditioning system 100 includes: an outdoor unit 110 having a heat source side refrigerant circuit RC1; a plurality of indoor units 120 each having an indoor heat exchanger 52; switching units 70 each having an intermediate refrigerant circuit RC3; and a heat recovery unit 130 having an auxiliary refrigerant circuit RC2 including an air supply side auxiliary heat exchanger 131 and an air exhaust side auxiliary heat exchanger 132. The heat source side refrigerant circuit RC1 and the intermediate refrigerant circuit RC3 are connected by a first communication pipe 11 in which a liquid refrigerant flows, a second communication pipe 12 in which a high-pressure gas refrigerant flows and a third communication pipe 13 in which a low-pressure gas refrigerant flows. The auxiliary refrigerant circuit RC2 is connected to the first communication pipe 11 and the second communication pipe 12 between the heat source side refrigerant circuit RC1 and the intermediate refrigerant circuit RC3, and includes a bypass pipe 16 connecting auxiliary refrigerant piping 135 and the first communication pipe 11.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to air conditioning systems. [Background technology]

[0002] Conventionally, there has been known an air conditioning system in which a heat source unit, a plurality of user units, an air supply unit having an auxiliary heat exchanger, and an exhaust unit having an auxiliary heat exchanger are connected by piping, and which allows the user unit performing cooling operation and the user unit performing heating operation to be used simultaneously (a so-called free cooling and heating system) (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 3-20573 Summary of the Invention [Problem to be solved by the invention]

[0004] The conventional air conditioning system can recover heat from the intake air and the exhaust air by using one of the auxiliary heat exchangers as an evaporator and the other as a condenser. The air conditioning system of Patent Document 1 does not disclose any technology for recovering heat by the auxiliary heat exchanger when the air conditioning system is in defrost operation during heating operation.

[0005] An object of the present disclosure is to enable heat recovery by the auxiliary heat exchanger during defrost operation in an air conditioning system equipped with an auxiliary heat exchanger for heat recovery. [Means for solving the problem]

[0006] (1) The air conditioning system of the present disclosure comprises: a first unit having a first refrigerant circuit including a compressor and a first heat exchanger; a second unit disposed in the first space and having a second heat exchanger; a third unit having a third heat exchanger; an intermediate unit having an intermediate refrigerant circuit for allowing the second heat exchanger and the third heat exchanger to function individually as an evaporator or a condenser; a heat recovery unit including an auxiliary refrigerant circuit including a first auxiliary heat exchanger and a second auxiliary heat exchanger connected in series to the first auxiliary heat exchanger by a first refrigerant pipe, an air supply fan that supplies outside air that has passed through the first auxiliary heat exchanger to the first space, and an exhaust fan that discharges the air of the first space that has passed through the second auxiliary heat exchanger to the outside; A control unit for controlling the operation of the heat recovery unit; Equipped with The first refrigerant circuit and the intermediate refrigerant circuit are connected by a first communication pipe through which a liquid refrigerant flows, a second communication pipe through which a high-pressure gas refrigerant flows, and a third communication pipe through which a low-pressure gas refrigerant flows, the auxiliary refrigerant circuit is connected to the second connecting pipe and the third connecting pipe between the first refrigerant circuit and the intermediate refrigerant circuit, A bypass pipe is provided that connects the first refrigerant pipe and the first connection pipe.

[0007] In an air conditioning system constituting a free heating and cooling system, during defrosting operation of the first heat exchanger, gas refrigerant of approximately the same pressure flows through the second and third connecting pipes, and the pressure difference between the second and third connecting pipes disappears, so that refrigerant does not flow through the first and second auxiliary heat exchangers. In the air conditioning system of the present disclosure, by providing a bypass pipe connecting the first connecting pipe and the first refrigerant piping, liquid refrigerant can be returned from the bypass pipe through the second auxiliary heat exchanger to the third connecting pipe. This makes it possible to recover heat from exhaust gas using the second auxiliary heat exchanger during defrosting operation of the first heat exchanger.

[0008] (2) Preferably, the cooling system further includes an electric valve provided on the first refrigerant pipe on the first auxiliary heat exchanger side relative to a connection position between the first refrigerant pipe and the bypass pipe, During a first operation for defrosting the first heat exchanger, the second connecting pipe and the first auxiliary heat exchanger are connected, and the third connecting pipe and the second auxiliary heat exchanger are connected, The control unit closes the motor-operated valve. According to this configuration, during the first operation for defrosting the first heat exchanger, the liquid refrigerant can be prevented from flowing toward the first auxiliary heat exchanger. As a result, during the first operation, the liquid refrigerant can be reliably returned from the bypass pipe to the third connecting pipe through the second auxiliary heat exchanger on the exhaust side. In this case, it is possible to prevent the cold air that has been heat exchanged by the first auxiliary heat exchanger on the supply side from being supplied to the first space by the supply air fan. Also, in this case, the time from the start to the completion of the first operation can be shortened.

[0009] (3) Preferably, the system further includes a first shutoff valve provided on a pipe connecting the second connecting pipe and the first auxiliary heat exchanger, During a first operation for defrosting the first heat exchanger, the third connecting pipe and the second auxiliary heat exchanger are connected, and the second connecting pipe and the first auxiliary heat exchanger are connected, The control unit closes the first shutoff valve. According to this configuration, during the first operation, it is possible to reliably suppress the liquid refrigerant from flowing toward the first auxiliary heat exchanger.

[0010] (4) Preferably, during a first operation for defrosting the first heat exchanger, the third connecting pipe and the second auxiliary heat exchanger are connected, and the second connecting pipe and the first auxiliary heat exchanger are connected, The control unit operates the exhaust fan and stops the supply air fan. According to this configuration, the second auxiliary heat exchanger can recover heat from the exhaust gas in the first space during the first operation.

[0011] (5) Preferably, the refrigerant is a flammable refrigerant, The heat exchanger further includes a second shutoff valve provided on a pipe connecting the second communication pipe and the second auxiliary heat exchanger, and a third shutoff valve provided on the bypass pipe. According to this configuration, the first refrigerant circuit and the auxiliary refrigerant circuit can be completely separated by closing the first to third shutoff valves, so that in the event that refrigerant leaks from the heat recovery unit, the amount of refrigerant leaking from the heat recovery unit can be reduced. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram of an air conditioning system according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a refrigerant circuit diagram of the air conditioning system. [Diagram 3] FIG. 2 is a schematic diagram of a heat recovery unit. [Figure 4] FIG. [Diagram 5] FIG. 4 is a schematic cross-sectional view taken along line XX in FIG. [Figure 6] FIG. 4 is a schematic cross-sectional explanatory view taken along line YY in FIG. [Figure 7] FIG. 2 is a control block diagram of the air conditioning system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the air conditioning system of the present disclosure will be described in detail with reference to the accompanying drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0014] FIG. 1 shows the overall configuration of an air conditioning system according to an embodiment of the present disclosure. The air conditioning system 100 of the present disclosure is installed in a building, a factory, or the like, and realizes air conditioning of the space to be air-conditioned. The air conditioning system 100 includes an air conditioner 101 and a refrigerant flow path switching device 140. The air conditioner 101 cools and heats the space to be air-conditioned by performing a vapor compression refrigeration cycle operation. The air conditioner 101 shown in this embodiment uses R32 as the refrigerant. Note that R32 is a refrigerant that has slight flammability. The air conditioner of the present disclosure may be configured to use a refrigerant other than R32.

[0015] In the air conditioning system 100, an indoor space S1 formed inside a building B is set as a space to be air-conditioned. A plurality of indoor spaces S1 are provided inside the building B. In the following description, a first indoor space S1 is referred to as a first space S11, a second indoor space S1 different from the first space S11 is referred to as a second space S12, and a space outside the building B is referred to as an outdoor space S2. The outdoor space S2 in the present disclosure is an outdoor space.

[0016] The air conditioner 101 has an outdoor unit 110 as a heat source unit and an indoor unit 120 and a heat recovery unit 130 as user units. In the air conditioner 101 of this embodiment, two or more indoor units 120 and one heat recovery unit 130 are connected to one outdoor unit 110. The indoor units 120 are connected to the outdoor unit 110 via a refrigerant flow path switching device 140. The air conditioner 101 can freely select cooling operation or heating operation for each indoor unit 120 by the refrigerant flow path switching device 140 to condition the target space.

[0017] In the air conditioning system 100, the first space S11 can be air-conditioned by the indoor unit 120 provided for the first space S11, and the first space S11 can be ventilated by the heat recovery unit 130. In the air conditioning system 100, the second space S12 can be air-conditioned by the indoor unit 120 provided for the second space S12. The outdoor unit 110 is installed in the outdoor space S2. The heat recovery unit 130 is installed outside the indoor space S1 inside the building B.

[0018] [Outdoor unit configuration] Fig. 2 is a refrigerant circuit diagram of the air conditioning system 100. As shown in Fig. 1, the outdoor unit 110 is installed in an outdoor space S2, for example, outdoors, such as on the roof or on a balcony of a building B, or in a basement or the like. As shown in Fig. 2, various devices are disposed in the outdoor unit 110, and these devices are connected via refrigerant piping to form a heat source side refrigerant circuit RC1. The heat source side refrigerant circuit RC1 is connected to an auxiliary refrigerant circuit RC2 in the heat recovery unit 130 and an intermediate refrigerant circuit RC3 in the refrigerant flow path switching device 140 via a first connecting pipe 11, a second connecting pipe 12, and a third connecting pipe 13.

[0019] As shown in Fig. 2, the heat source side refrigerant circuit RC1 includes a liquid side shutoff valve 21, a gas side first shutoff valve 22, a gas side second shutoff valve 23, an accumulator 24, a compressor 25, a first flow path switching valve 26, a second flow path switching valve 27, a third flow path switching valve 28, an outdoor heat exchanger 30, a first outdoor expansion valve 34, and a second outdoor expansion valve 35. The heat source side refrigerant circuit RC1 is configured by connecting these devices via multiple refrigerant pipes. An outdoor fan 33, a control unit 115 (see Fig. 7), and the like are disposed in the outdoor unit 110.

[0020] The liquid side shutoff valve 21, the gas side first shutoff valve 22, and the gas side second shutoff valve 23 are manual valves that are opened and closed when charging the refrigerant, pumping down, etc. One end of the liquid side shutoff valve 21 is connected to the first connecting pipe 11. The other end of the liquid side shutoff valve 21 is connected to the refrigerant piping extending to the first outdoor expansion valve 34 and the second outdoor expansion valve 35. One end of the gas side first shutoff valve 22 is connected to the second connecting pipe 12. The other end of the gas side first shutoff valve 22 is connected to the refrigerant piping extending to the second flow path switching valve 27. One end of the gas side second shutoff valve 23 is connected to the third connecting pipe 13. The other end of the gas side second shutoff valve 23 is connected to the refrigerant piping 25c extending to the accumulator 24.

[0021] The accumulator 24 is a container for temporarily storing the low-pressure refrigerant sucked into the compressor 25 and separating the refrigerant into gas refrigerant and liquid refrigerant.

[0022] The compressor 25 has a sealed structure with a built-in compressor motor, and is, for example, a volumetric compressor such as a scroll type or rotary type. The compressor 25 compresses the low-pressure refrigerant sucked from the suction pipe 25b and then discharges it from the discharge pipe 25a. Refrigerating machine oil is contained inside the compressor 25. This refrigerating machine oil may circulate in the refrigerant circuit together with the refrigerant. The outdoor unit 110 of this embodiment includes one compressor 25. However, the outdoor unit 110 may include two or more compressors 25 connected in parallel.

[0023] The first flow path switching valve 26, the second flow path switching valve 27, and the third flow path switching valve 28 are four-way switching valves. The first flow path switching valve 26, the second flow path switching valve 27, and the third flow path switching valve 28 switch the flow of the refrigerant depending on the operating condition of the air conditioner 101. The discharge pipe 25a or a branch pipe extending from the discharge pipe 25a is connected to one of the refrigerant inlets of the first flow path switching valve 26, the second flow path switching valve 27, and the third flow path switching valve 28. The first flow path switching valve 26, the second flow path switching valve 27, and the third flow path switching valve 28 are connected to one of the refrigerant inlets of the first flow path switching valve 26, the second flow path switching valve 27, and the third flow path switching valve 28. The first flow path switching valve 26, the second flow path switching valve 27, and the third flow path switching valve 28 are configured to block the flow of refrigerant in one of the refrigerant flow paths during operation, and in effect function as a three-way valve.

[0024] The outdoor heat exchanger 30 is a cross-fin type or microchannel type heat exchanger. The outdoor heat exchanger 30 includes a first heat exchange section 31 and a second heat exchange section 32. The first heat exchange section 31 is provided in an upper portion of the outdoor heat exchanger 30, and the second heat exchange section 32 is provided below the first heat exchange section 31.

[0025] A gas side end of the first heat exchange section 31 is connected to a refrigerant pipe extending to the third flow path switching valve 28. A liquid side end of the first heat exchange section 31 is connected to a refrigerant pipe extending to the first outdoor expansion valve 34.

[0026] A gas side end of the second heat exchange section 32 is connected to a refrigerant pipe extending to the first flow path switching valve 26. A liquid side end of the second heat exchange section 32 is connected to a refrigerant pipe extending to the second outdoor expansion valve 35.

[0027] The refrigerant passing through the first heat exchange section 31 and the second heat exchange section 32 exchanges heat with an airflow generated by the outdoor fan 33. The outdoor fan 33 is, for example, a propeller fan, and is driven by an outdoor fan motor (not shown). The outdoor fan 33 generates an airflow that flows into the outdoor unit 110, passes through the outdoor heat exchanger 30, and flows out of the outdoor unit 110.

[0028] The first outdoor expansion valve 34 and the second outdoor expansion valve 35 are, for example, motor-operated valves whose opening degrees can be adjusted. One end of the first outdoor expansion valve 34 is connected to a refrigerant pipe extending from the first heat exchanger 31. The other end of the first outdoor expansion valve 34 is connected to a refrigerant pipe extending to the liquid side shutoff valve 21.

[0029] One end of the second outdoor expansion valve 35 is connected to a refrigerant pipe extending from the second heat exchange section 32. The other end of the second outdoor expansion valve 35 is connected to a refrigerant pipe extending to the liquid side stop valve 21. The opening degrees of the first outdoor expansion valve 34 and the second outdoor expansion valve 35 are adjusted according to the operating conditions, and the pressure of the refrigerant passing through the insides is reduced according to the opening degrees.

[0030] The operation of the compressor 25, the outdoor fan 33, the first outdoor expansion valve 34, the second outdoor expansion valve 35, the first flow path switching valve 26, the second flow path switching valve 27, and the third flow path switching valve 28 is controlled by a control unit 115 (see FIG. 7). The control unit 115 of the outdoor unit 110 transmits and receives signals to and from the indoor control unit 54 (see FIG. 7) of the indoor unit 120 and a control unit (not shown) of the refrigerant flow path switching device 140 via communication lines.

[0031] [Indoor unit configuration] The indoor unit 120 may be a ceiling embedded type, a ceiling suspended type, a floor standing type, or a wall mounted type. The air conditioning system 100 of this embodiment includes two or more indoor units 120.

[0032] A utilization-side refrigerant circuit RC4 is provided in the indoor unit 120. The utilization-side refrigerant circuit RC4 includes an indoor expansion valve 51 and an indoor heat exchanger 52. The utilization-side refrigerant circuit RC4 is configured by connecting the indoor expansion valve 51 and the indoor heat exchanger 52 by a refrigerant piping.

[0033] An indoor fan 53 and an indoor control unit 54 (see FIG. 7) are disposed in the indoor unit 120. The indoor expansion valve 51 is an electrically operated valve whose opening degree can be adjusted. One end of the indoor expansion valve 51 is connected to a liquid pipe LP. The other end of the indoor expansion valve 51 is connected to a refrigerant piping that extends to the indoor heat exchanger 52. The indoor expansion valve 51 reduces the pressure of the refrigerant passing through it according to its opening degree.

[0034] The indoor heat exchanger 52 is, for example, a cross-fin type or a microchannel type heat exchanger. A liquid side end of the indoor heat exchanger 52 is connected to a refrigerant piping extending from the indoor expansion valve 51. A gas side end of the indoor heat exchanger 52 is connected to a gas pipe GP. The refrigerant that flows into the indoor heat exchanger 52 exchanges heat with an airflow generated by the indoor fan 53, and is discharged from the indoor heat exchanger 52.

[0035] The indoor fan 53 is, for example, a cross-flow fan or a sirocco fan. The indoor fan 53 is driven by an indoor fan motor (not shown). The indoor fan 53 generates an airflow that flows from the indoor space S1 into the indoor unit 120, passes through the indoor heat exchanger 52, and then flows out into the indoor space S1.

[0036] The operation of the indoor expansion valve 51 and the indoor fan 53 is controlled by an indoor control unit 54 (see FIG. 7) of the indoor unit 120. A control unit 115 of the outdoor unit 110 and a remote controller (not shown) are connected to the indoor control unit 54. The indoor control unit 54 drives the indoor fan 53 and the indoor expansion valve 51 based on operating conditions such as the set temperature input to the remote controller.

[0037] [Configuration of the refrigerant flow path switching device] 1 and 2, the refrigerant flow path switching device 140 is provided between the outdoor unit 110 and the multiple indoor units 120. The refrigerant flow path switching device 140 has a casing 141. The refrigerant flow path switching device 140 switches the flow of refrigerant flowing into the outdoor unit 110 and each indoor unit 120. As shown in Fig. 2, the casing 141 houses multiple header pipes 55, 56, 57, 58 and multiple switching units 70.

[0038] (Header pipe) 2, the multiple header pipes 55, 56, 57, 58 include a first header pipe 55, a second header pipe 56, a third header pipe 57, and a fourth header pipe 58. The first header pipe 55 is connected to the first connecting pipe 11. The second header pipe 56 is connected to the second connecting pipe 12. The third header pipe 57 is connected to the third connecting pipe 13.

[0039] (Switching unit) The refrigerant flow path switching device 140 includes a plurality of switching units 70. Each switching unit 70 forms an intermediate refrigerant circuit RC3 of the refrigerant flow path switching device 140. One indoor unit 120 is connected to each switching unit 70. However, it is not necessary for indoor units 120 to be connected to all switching units 70 of the refrigerant flow path switching device 140, and the refrigerant flow path switching device 140 may include a switching unit 70 to which no indoor unit 120 is connected.

[0040] (Intermediate refrigerant circuit) The multiple switching units 70 all have the same structure, and the intermediate refrigerant circuit RC3 of each switching unit 70 includes multiple valves EV1, EV2, EV3, and multiple refrigerant pipes.

[0041] In the switching unit 70, the multiple valves EV1, EV2, and EV3 include a first valve EV1, a second valve EV2, and a third valve EV3. These valves EV1, EV2, and EV3 are configured as motorized valves whose opening degree can be adjusted. The second valve EV2 and the third valve EV3 are controlled by a control unit (not shown) to take any one of a fully closed state, a fully open state, and an opening degree adjustment state. The first valve EV1 is controlled by a control unit (not shown) to take any one of a minimum opening state, a fully open state, a fully closed state, and an opening degree adjustment state.

[0042] The switching unit 70 includes a first refrigerant pipe P1 that connects the second header pipe 56 and the first valve EV1. A filter F1 is provided in the middle of the first refrigerant pipe P1. The switching unit 70 includes a second refrigerant pipe P2. One end of the second refrigerant pipe P2 is connected to the first valve EV1. The switching unit 70 includes a usage-side gas pipe 61. One end of the usage-side gas pipe 61 is connected to the gas pipe GP of the indoor unit 120. The other end of the usage-side gas pipe 61 is connected to the second valve EV2. The other end of the second refrigerant pipe P2 is connected to the usage-side gas pipe 61. The usage-side gas pipe 61 is provided with a filter F2.

[0043] The switching unit 70 includes a third refrigerant pipe P3. One end of the third refrigerant pipe P3 is connected to the second valve EV2. The other end of the third refrigerant pipe P3 is connected to the third header pipe 57. A filter F3 is provided in the middle of the third refrigerant pipe P3.

[0044] The switching unit 70 includes a utilization side liquid piping 62. One end of the utilization side liquid piping 62 is connected to the liquid pipe LP of the indoor unit 120. The other end of the utilization side liquid piping 62 is connected to a subcooling heat exchanger 59. A first heat transfer tube 59a and a second heat transfer tube 59b are provided inside the subcooling heat exchanger 59. The subcooling heat exchanger 59 exchanges heat between the refrigerant flowing through the first heat transfer tube 59a and the refrigerant flowing through the second heat transfer tube 59b. The other end of the utilization side liquid piping 62 is connected to one end of the first heat transfer tube 59a.

[0045] The switching unit 70 includes a fourth refrigerant pipe P4. One end of the fourth refrigerant pipe P4 is connected to the other end of the first heat transfer pipe 59a. The other end of the fourth refrigerant pipe P4 is connected to the first header pipe 55.

[0046] The switching unit 70 includes a fifth refrigerant pipe P5 that branches off from the fourth refrigerant pipe P4. One end of the fifth refrigerant pipe P5 is connected to one end of the third valve EV3. A filter F4 is provided in the fifth refrigerant pipe P5.

[0047] The switching unit 70 includes a sixth refrigerant pipe P6 and a seventh refrigerant pipe P7. One end of the sixth refrigerant pipe P6 is connected to the third valve EV3. The other end of the sixth refrigerant pipe P6 is connected to one end of the second heat transfer pipe 59b of the subcooling heat exchanger 59. One end of the seventh refrigerant pipe P7 is connected to the second heat transfer pipe 59b of the subcooling heat exchanger 59. The other end of the seventh refrigerant pipe P7 is connected to the fourth header pipe 58. The fourth header pipe 58 is connected to the third header pipe 57 via the connecting pipe 63.

[0048] The refrigerant flows into the fourth header pipe 58 from the first header pipe 55 through the fourth refrigerant pipe P4, the fifth refrigerant pipe P5, the third valve EV3, the sixth refrigerant pipe P6, the subcooling heat exchanger 59, and the seventh refrigerant pipe P7. The refrigerant that has flowed into the fourth header pipe 58 further flows into the third header pipe 57 through the connecting pipe 63.

[0049] [Heat recovery unit configuration] The heat recovery unit 130 is a device that can supply cooled and heated air (outdoor air) to the indoor space S1 and ventilate the indoor space S1 while recovering heat from the air (exhaust air) discharged from the indoor space S1, and is also called an outdoor air processing unit. The heat recovery unit 130 is disposed outside the indoor space S1 inside the building B. The heat recovery unit 130 is disposed in the space above the ceiling of the indoor space S1 and is connected to the indoor space S1 and the outdoor space S2 through a duct. Note that, although the present embodiment illustrates a case in which the heat recovery unit 130 is disposed in the space above the ceiling of the indoor space S1, the heat recovery unit of the present disclosure may be a ceiling-suspended type, a ceiling-embedded type, a floor-standing type, or a wall-mounted type, and may be disposed in a place other than the ceiling. As shown in Fig. 2 and Fig. 3, the heat recovery unit 130 includes an intake side auxiliary heat exchanger 131, an exhaust side auxiliary heat exchanger 132, an auxiliary heat exchanger switching valve 133, and a heat exchange section 134. An auxiliary refrigerant circuit RC2 is provided in the heat recovery unit 130. The auxiliary refrigerant circuit RC2 is configured by connecting the intake side auxiliary heat exchanger 131, the exhaust side auxiliary heat exchanger 132, and the auxiliary heat exchanger switching valve 133 by an auxiliary refrigerant piping 135. The auxiliary refrigerant piping 135 includes a first auxiliary refrigerant pipe 135a, a second auxiliary refrigerant pipe 135b, a third auxiliary refrigerant pipe 135c, a fourth auxiliary refrigerant pipe 135d, and a fifth auxiliary refrigerant pipe 135e.

[0050] The intake side auxiliary heat exchanger 131 and the exhaust side auxiliary heat exchanger 132 are, for example, cross-fin type or microchannel type heat exchangers. One side end of the intake side auxiliary heat exchanger 131 is connected to a first auxiliary refrigerant pipe 135c extending from the auxiliary heat exchanger switching valve 133. The other side end of the intake side auxiliary heat exchanger 131 is connected to one end of the second auxiliary refrigerant pipe 135b. The other end of the second auxiliary refrigerant pipe 135b is connected to one side end of the exhaust side auxiliary heat exchanger 132. An electric valve 136 is provided in the middle of the second auxiliary refrigerant pipe 135b. The electric valve 136 is an electric valve whose opening degree can be adjusted. The other side end of the exhaust side auxiliary heat exchanger 132 is connected to a third auxiliary refrigerant pipe 135a extending from the auxiliary heat exchanger switching valve 133.

[0051] The auxiliary heat exchanger switching valve 133 is a four-way switching valve having four ports, and a first auxiliary refrigerant pipe 135a, a second auxiliary refrigerant pipe 135b, a fourth auxiliary refrigerant pipe 135d, and a fifth auxiliary refrigerant pipe 135e are connected to the respective ports. The fourth auxiliary refrigerant pipe 135d is connected to the first branch pipe 14, and the fifth auxiliary refrigerant pipe 135e is connected to the second branch pipe 15. The auxiliary heat exchanger switching valve 133 switches the flow of refrigerant between the first auxiliary refrigerant pipe 135a, the second auxiliary refrigerant pipe 135b, the fourth auxiliary refrigerant pipe 135d, and the fifth auxiliary refrigerant pipe 135e.

[0052] The auxiliary refrigerant circuit RC2 is connected to the second connection pipe 12 via the first branch pipe 14, and is connected to the third connection pipe 13 via the second branch pipe 15. In other words, the auxiliary refrigerant circuit RC2 of the heat recovery unit 130 is connected to the heat source side refrigerant circuit RC1 of the outdoor unit 110 without going through the refrigerant flow switching device 140.

[0053] (Bypass pipe) 1 and 2, the air conditioning system 100 further includes a bypass pipe 16 that connects the first connecting pipe 11 and the heat recovery unit 130. The bypass pipe 16 is a pipe for passing liquid refrigerant when the air conditioning system 100 performs a defrost operation, and is not used during normal cooling or heating. One end of the bypass pipe 16 is connected to the first connecting pipe 11, and the other end is connected to an auxiliary refrigerant pipe 135 that constitutes the auxiliary refrigerant circuit RC2. The connection position between the bypass pipe 16 and the auxiliary refrigerant pipe 135 is referred to as a connection position P.

[0054] 3, the bypass pipe 16 is connected to the second auxiliary refrigerant pipe 135b of the auxiliary refrigerant pipe 135. Therefore, a connection position P between the bypass pipe 16 and the auxiliary refrigerant pipe 135 is located between the exhaust side auxiliary heat exchanger 132 and the intake side auxiliary heat exchanger 131. The motor-operated valve 136 is disposed on the second auxiliary refrigerant pipe 135b, closer to the intake side auxiliary heat exchanger 131 than the connection position P.

[0055] 1 and 2, a third shutoff valve 163 is disposed in the bypass pipe 16. The third shutoff valve 163 is a valve that can shut off the flow of refrigerant in the bypass pipe 16 by closing it. The third shutoff valve 163 is kept closed while the air conditioning system 100 is in operation except during the defrost operation.

[0056] (Intake and exhaust fans) As shown in FIG. 3, an intake fan 137 and an exhaust fan 138 are disposed in the heat recovery unit 130. The intake fan 137 and the exhaust fan 138 are, for example, sirocco fans. The intake fan 137 is driven by an intake fan motor (not shown). The intake fan 137 generates an air flow that flows from the outdoor space S2 (see FIG. 1) into the heat recovery unit 130, passes through the intake side auxiliary heat exchanger 131, and then flows out to the indoor space S1 (see FIG. 1). The exhaust fan 138 is driven by an exhaust fan motor (not shown). The exhaust fan 138 generates an air flow that flows from the indoor space S1 (see FIG. 1) into the heat recovery unit 130, passes through the exhaust side auxiliary heat exchanger 132, and then flows out to the outdoor space S2 (see FIG. 1).

[0057] (Configuration of the intake and exhaust passages) As shown in FIG. 3, the return air intake 157 is used to take in air (return air RA) from the indoor space S1 (see FIG. 1) into the casing 150. The return air intake 157 is connected to the indoor space S1 via a duct or the like (not shown). The exhaust air outlet 155 is used to exhaust the return air RA taken into the casing 150 to the outdoor space S2 (see FIG. 1) as exhaust air EA. The exhaust air outlet 155 is connected to the outdoor space S2 via a duct or the like (not shown). The outdoor air intake 158 is used to take in air (outdoor air OA) from the outdoor space S2 into the casing 150. The outdoor air intake 158 is connected to the outdoor space S2 via a duct or the like (not shown). The supply air outlet 156 is used to supply the outdoor air OA taken into the casing 150 to the indoor space S1 as supply air SA. The supply air outlet 156 is connected to the indoor space S1 via a duct or the like (not shown).

[0058] (Heat exchange part) Fig. 4 is a perspective view of the heat exchanger. As shown in Fig. 4, the heat exchanger 134 in this embodiment is an orthogonal total heat exchanger configured such that the first air flow A1 and the second air flow A2 are substantially orthogonal to each other. This heat exchanger 134 has a partition plate 134a and a partition plate 134b. The partition plates 134a and the partition plates 134b are alternately laminated with an appropriate adhesive. The heat exchanger 134 is formed into a substantially rectangular prism shape as a whole.

[0059] The partition plate 134a is formed in a flat plate shape having thermal conductivity and moisture permeability. The partition plate 134b is formed in a corrugated plate shape with a substantially triangular cross section formed continuously. The partition plate 134b forms an air passage between two adjacent partition plates 134a. The partition plates 134b are stacked at an angle of 90 degrees each in the stacking direction (vertical direction in FIG. 4) of the partition plate 134a and the partition plate 134b. As a result, an air supply side passage 134d for passing the first air flow A1 and an exhaust side passage 134c for passing the second air flow A2 are formed on both sides of one partition plate 134a, perpendicular to each other. The air flowing through the exhaust side passage 134c and the air flowing through the air supply side passage 134d exchange sensible heat and latent heat (total heat exchange) through the partition plate 134a having thermal conductivity and moisture permeability. In the air conditioning system 100, the heat recovery unit 130 recovers heat using the refrigerant flowing through the first auxiliary refrigerant circuit RC2, and the heat exchange section 134 further recovers heat between the air flowing through the casing 150 (between the return air RA and the outdoor air OA), thereby further improving the operating efficiency of the air conditioner 101.

[0060] FIG. 5 is a schematic cross-sectional view taken along line XX in FIG. 3. FIG. 6 is a schematic cross-sectional view taken along line YY in FIG. 3. As shown in FIGS. 3, 5, and 6, the heat recovery unit 130 has a casing 150. The inside of the casing 150 is divided into two regions, an indoor space S1 side and an outdoor space S2 side (see FIG. 1), by the heat exchanger 134. As shown in FIG. 5, an upstream air supply passage 151a is formed in the casing 150 on the upstream side of the first air flow A1 from the heat exchanger 134, and a downstream air supply passage 151b is formed on the downstream side of the first air flow A1 from the heat exchanger 134. The upstream air supply passage 151a and the downstream air supply passage 151b constitute an air supply passage 151 that communicates the indoor space S1 and the outdoor space S2 via the heat exchanger 134.

[0061] 6, an upstream exhaust passage 152a is formed in the casing 150 upstream of the heat exchange section 134 in the second air flow A2, and a downstream exhaust passage 152b is formed downstream of the heat exchange section 134 in the second air flow A2. The upstream exhaust passage 152a and the downstream exhaust passage 152b form an exhaust passage 152 that communicates between the indoor space S1 and the outdoor space S2 via the heat exchange section 134.

[0062] 5 and 6, a partition wall 153 is provided between the downstream air supply passage 151b and the upstream exhaust passage 152a. A partition wall 154 is provided between the upstream air supply passage 151a and the downstream exhaust passage 152b.

[0063] 5, in the downstream supply air passage 151b, a supply air fan 137 and a supply air side auxiliary heat exchanger 131 are disposed near the supply air outlet 156. When the supply air fan 137 is operated, a first air flow A1 is generated, and outside air OA in the outdoor space S2 passes through the supply air passage 151, is heat exchanged by the supply air side auxiliary heat exchanger 131, and is supplied to the indoor space S1 as supply air SA. The supply air side auxiliary heat exchanger 131 exchanges heat (recovers heat) between the refrigerant flowing through the auxiliary refrigerant circuit RC2 and the air (outdoor air OA) passing through the supply air passage 151.

[0064] 6, in the downstream exhaust passage 152b, an exhaust fan 138 and an exhaust-side auxiliary heat exchanger 132 are disposed near the exhaust air outlet 155. When the exhaust fan 138 is operated, a second airflow A2 is generated, and the return air RA from the indoor space S1 passes through the exhaust passage 152, is heat exchanged by the exhaust-side auxiliary heat exchanger 132, and is discharged to the outdoor space S2 as exhaust air EA. The exhaust-side auxiliary heat exchanger 132 exchanges heat (recovers heat) between the refrigerant flowing through the auxiliary refrigerant circuit RC2 and the air (exhaust air EA) passing through the exhaust passage 152.

[0065] [About the control unit] FIG. 7 is a control block diagram of the air conditioning system 100. As shown in FIG. 7, the air conditioning system 100 includes a control unit 115. The control unit 115 is a device that controls the operation of the air conditioner 101, and is configured, for example, by a microcomputer equipped with a processor such as a CPU, and memories such as a RAM and a ROM. The control unit 115 may be realized as hardware using an LSI, an ASIC, an FPGA, or the like. The control unit 115 exerts a predetermined function by the processor executing a program installed in the memory. The control unit 115 may be provided integrally with the air conditioner 101 as a part of the air conditioner 101, or may be provided separately as a device separate from the air conditioner 101.

[0066] The control unit 115 of this embodiment is provided in the outdoor unit 110. The control unit 115 is connected to the compressor 25, the first flow path switching valve 26, the second flow path switching valve 27, the third flow path switching valve 28, the outdoor fan 33, the first outdoor expansion valve 34, and the second outdoor expansion valve 35 built in the outdoor unit 110. The control unit 115 is connected to the indoor expansion valve 51 and the indoor fan 53 via the indoor control unit 54 of the indoor unit 120. The control unit 115 is connected to the auxiliary heat exchanger switching valve 133, the motor-operated valve 136, the supply air fan 137, and the exhaust fan 138 of the heat recovery unit 130. The control unit 115 may be connected to the auxiliary heat exchanger switching valve 133, the motor-operated valve 136, the supply air fan 137, and the exhaust fan 138 via a control unit (not shown) of the heat recovery unit 130. The first valve EV1, the second valve EV2, and the third valve EV3 are connected to the control unit 115 via a control unit (not shown) of the refrigerant flow path switching device 140 (switching unit 70). The first shutoff valve 161 and the second shutoff valve 162 are connected to the control unit 115. The control unit 115 controls the operation of each of the above-mentioned connected parts according to the operating status of the air conditioning system 100.

[0067] [Shut-off valve] 1 and 2, the air conditioning system 100 has a first shutoff valve 161 and a second shutoff valve 162. The first shutoff valve 161 and the second shutoff valve 162 are motor-operated valves, with the first shutoff valve 161 disposed in the first branch pipe 14 and the second shutoff valve 162 disposed in the second branch pipe 15. The operations of the first shutoff valve 161 and the second shutoff valve 162 are controlled by a control unit 115. A refrigerant sensor 180 (see FIG. 7) is connected to the control unit 115.

[0068] In the air conditioning system 100, the refrigerant sensor 180 (see FIG. 7) is disposed at a position where it can detect refrigerant leaking from the heat recovery unit 130. When the refrigerant sensor 180 detects refrigerant, the control unit 115 operates the first to third shutoff valves 161, 162, and 163. In the air conditioning system 100, when the first to third shutoff valves 161, 162, and 163 are operated, the auxiliary refrigerant circuit RC2 of the heat recovery unit 130 is completely separated from the other refrigerant circuits RC1, RC3, and RC4 in the air conditioning system 100. Therefore, in the air conditioning system 100, even if a flammable refrigerant (R32 in this embodiment) leaks from the heat recovery unit 130, it is possible to prevent the refrigerant from leaking from the heat recovery unit 130 in excess of the amount of refrigerant stored in the auxiliary refrigerant circuit RC2 at that time. It should be noted that in the air conditioning system of the present disclosure, when a non-flammable refrigerant is used, the first and second shutoff valves and the refrigerant sensor do not need to be provided.

[0069] [Air conditioning system operation] Below, with reference to FIG. 2, we will explain the cases where the air conditioning system 100 has all of the operating indoor units 120 performing cooling (hereinafter also referred to as "all cooling operation"), where all of the operating indoor units 120 performing heating (hereinafter also referred to as "all heating operation"), and where some of the operating indoor units 120 perform cooling and others perform heating (hereinafter also referred to as "mixed cooling / heating operation").

[0070] (Fully cooling operation) In the full cooling operation, the control unit 115 adjusts each valve as follows. The first valve EV1 of the switching unit 70 is fully closed, the second valve EV2 is fully opened, the third valve EV3 has its opening adjusted, the indoor expansion valve 51 has its opening adjusted, the first and second outdoor expansion valves 34, 35 are fully opened, the first and second shutoff valves 161, 162 are fully opened, and the third shutoff valve 163 is fully closed. The first flow path switching valve 26 of the outdoor unit 110 is switched to connect the discharge pipe 25a of the compressor 25 to the gas side end of the second heat exchange section 32. The second flow path switching valve 27 is switched to connect the discharge pipe 25a to the second connection pipe 12. The third flow path switching valve 28 is switched to connect the discharge pipe 25a to the gas side end of the first heat exchange section 31.

[0071] In the indoor unit 120 that is stopped, the control unit 115 fully closes the indoor expansion valve 51 regardless of whether full cooling operation, full heating operation, or mixed cooling and heating operation is being performed, the first valve EV1 corresponding to this indoor unit 120 is opened to the minimum degree, and the second valve EV2 and third valve EV3 are fully closed.

[0072] When the compressor 25 is driven, the high-pressure gas refrigerant compressed by the compressor 25 passes through the discharge pipe 25a, the first flow path switching valve 26, the third flow path switching valve 28, etc., and flows into the outdoor heat exchanger 30, where it is condensed. The refrigerant condensed in the outdoor heat exchanger 30 passes through the first and second outdoor expansion valves 34, 35, the liquid side stop valve 21, etc., and flows into the first connecting pipe 11.

[0073] The refrigerant that has flowed into the first connection pipe 11 flows through the first header pipe 55 of the refrigerant flow path switching device 140, and flows into the fourth refrigerant pipe P4 of each switching unit 70. The refrigerant that has flowed into the fourth refrigerant pipe P4 flows into the first heat transfer pipe 59a of the subcooling heat exchanger 59, and further flows into the indoor unit 120 via the utilization side liquid piping 62.

[0074] The refrigerant that has flowed into the fourth refrigerant pipe P4 also branches off to flow into the fifth refrigerant pipe P5, where it is decompressed according to the opening degree of the third valve EV3, and flows into the second heat transfer pipe 59b of the subcooling heat exchanger 59. In this subcooling heat exchanger 59, heat is exchanged between the refrigerant flowing through the first heat transfer pipe 59a and the refrigerant flowing through the second heat transfer pipe 59b, and the refrigerant flowing through the first heat transfer pipe 59a is subcooled and flows into the indoor unit 120.

[0075] The refrigerant flowing through the second heat transfer pipe 59b of the subcooling heat exchanger 59 flows from the seventh refrigerant pipe P7 into the fourth header pipe 58, passes through the connecting pipe 63, and flows into the third header pipe 57. The refrigerant that has flowed into the indoor unit 120 is reduced in pressure by the indoor expansion valve 51, and then evaporates in the indoor heat exchanger 52.

[0076] In the indoor unit 120, the refrigerant evaporated in the indoor heat exchanger 52 flows from the gas pipe GP into the utilization side gas piping 61, passes mainly through the second valve EV2, and flows into the third header pipe 57. The refrigerant that has flowed into the third header pipe 57 passes through the third connection pipe 13 and the gas side second shutoff valve 23, flows into the accumulator 24, and is sucked into the compressor 25.

[0077] (About the heat recovery unit during cooling operation) When the air conditioning system 100 is in cooling operation, the control unit 115 switches the auxiliary heat exchanger switching valve 133 to connect the first auxiliary refrigerant pipe 135a and the fourth auxiliary refrigerant pipe 135d, and also connect the third auxiliary refrigerant pipe 135c and the fifth auxiliary refrigerant pipe 135e (see FIG. 3). High-pressure gas refrigerant is supplied from the second connection pipe 12 and the first branch pipe 14 to the exhaust side auxiliary heat exchanger 132 of the heat recovery unit 130, and the gas refrigerant flows from the first auxiliary refrigerant pipe 135a into the exhaust side auxiliary heat exchanger 132. At this time, the control unit 115 adjusts the opening of the motor-operated valve 136 to adjust the amount of refrigerant flowing into the exhaust side auxiliary heat exchanger 132 and reduce the pressure of the refrigerant. The gas refrigerant exchanges heat with air (exhaust EA) in the exhaust side auxiliary heat exchanger 132 and is condensed to become a liquid refrigerant. This liquid refrigerant is supplied to the air supply side auxiliary heat exchanger 131 via the second auxiliary refrigerant pipe 135b. The liquid refrigerant exchanges heat with air (outdoor air OA) in the air supply side auxiliary heat exchanger 131 and evaporates to become low-pressure gas refrigerant. This low-pressure gas refrigerant is returned to the third connecting pipe 13 via the second branch pipe 15. In this way, during cooling operation, the heat recovery unit 130 cools the outdoor air OA and supplies it to the indoor space S1. The high-pressure gas refrigerant flowing to the second connecting pipe 12 via the second flow path switching valve 27 does not flow to the indoor unit 120 because the first valve EV1 is fully closed.

[0078] (About full heating operation) In the full heating operation, the control unit 115 adjusts each valve as follows. The first valve EV1 of the switching unit 70 is fully opened, the second valve EV2 is fully closed, the third valve EV3 is fully closed, the indoor expansion valve 51 is fully opened, the first and second outdoor expansion valves 34, 35 have their openings adjusted, the first and second shutoff valves 161, 162 are fully opened, and the third shutoff valve 163 is fully closed. The first flow path switching valve 26 of the outdoor unit 110 is switched to connect the refrigerant pipe 25c to the gas side end of the second heat exchange section 32. The second flow path switching valve 27 is switched to connect the discharge pipe 25a to the second connection pipe 12. The third flow path switching valve 28 is switched to connect the refrigerant pipe 25c to the gas side end of the first heat exchange section 31.

[0079] When the compressor 25 is driven, the high-pressure gas refrigerant compressed by the compressor 25 passes through the discharge pipe 25a, the second flow path switching valve 27, etc., and flows into the second communication pipe 12. The refrigerant that has flowed into the second communication pipe 12 passes through the second header pipe 56 of the refrigerant flow path switching device 140 and the first refrigerant pipe P1 of the switching unit 70, passes through the first valve EV1, and flows from the utilization side gas pipe 61 into the gas pipe GP of the indoor unit 120.

[0080] The refrigerant that has flowed into the gas pipe GP flows into the indoor heat exchanger 52 of the indoor unit 120 and is condensed. The condensed refrigerant passes through the indoor expansion valve 51 and flows through the liquid pipe LP, and flows into the utilization-side liquid piping 62 of the switching unit 70. The refrigerant that has flowed into the utilization-side liquid piping 62 flows into the first header pipe 55 via the subcooling heat exchanger 59 and the fourth refrigerant pipe P4.

[0081] The refrigerant that has flowed into the first header pipe 55 flows through the first connecting pipe 11 and into the outdoor unit 110, and is depressurized in the first and second outdoor expansion valves 34, 35. The depressurized refrigerant evaporates when passing through the outdoor heat exchanger 30, passes through the first flow path switching valve 26, the third flow path switching valve 28, etc., flows into the accumulator 24, and is sucked into the compressor 25.

[0082] (About the heat recovery unit during heating operation) When the air conditioning system 100 is in heating operation, the control unit 115 switches the auxiliary heat exchanger switching valve 133 to connect the third auxiliary refrigerant pipe 135c and the fourth auxiliary refrigerant pipe 135d, and also connect the first auxiliary refrigerant pipe 135a and the fifth auxiliary refrigerant pipe 135e (see FIG. 3). A high-pressure gas refrigerant is supplied from the second connection pipe 12 and the first branch pipe 14 to the air supply side auxiliary heat exchanger 131 of the heat recovery unit 130, and the gas refrigerant flows into the air supply side auxiliary heat exchanger 131 from the fourth auxiliary refrigerant pipe 135d and the third auxiliary refrigerant pipe 135c. At this time, the control unit 115 adjusts the opening of the motor valve 136 to adjust the amount of refrigerant flowing into the air supply side auxiliary heat exchanger 131 and reduce the pressure of the refrigerant. The gas refrigerant exchanges heat with air (outdoor air OA) in the air supply side auxiliary heat exchanger 131 and is condensed to become a liquid refrigerant. The liquid refrigerant is supplied to the exhaust side auxiliary heat exchanger 132 via the second auxiliary refrigerant pipe 135b, and exchanges heat with the air (exhaust air EA) in the exhaust side auxiliary heat exchanger 132 to evaporate and become a low-pressure gas refrigerant. This low-pressure gas refrigerant is returned to the third connection pipe 13 via the first auxiliary refrigerant pipe 135a, the fifth auxiliary refrigerant pipe 135e, and the second branch pipe 15. In this way, the heat recovery unit 130 heats the outdoor air OA and supplies it to the indoor space S1 during heating operation.

[0083] (mixed heating and cooling operation) In the cooling / heating mixed operation, the control unit 115 adjusts each valve as follows. In the switching unit 70 (hereinafter also referred to as the "cooling-side switching unit 70") corresponding to the indoor unit 120 performing the cooling operation (hereinafter also referred to as the "cooling-side indoor unit 120") among the indoor units 120 in operation, the first valve EV1 is set to the minimum opening degree, the second valve EV2 is fully opened, the third valve EV3 has its opening degree adjusted, the indoor expansion valve 51 of the cooling-side indoor unit 120 has its opening degree adjusted, the first and second shutoff valves 161, 162 are fully opened, and the third shutoff valve 163 is fully closed. The first flow path switching valve 26 of the outdoor unit 110 is switched so as to connect the refrigerant pipe 25c and the gas side end of the second heat exchanger 32. The second flow path switching valve 27 is switched so as to connect the discharge pipe 25a and the second connecting pipe 12. The third flow path switching valve 28 is switched so as to connect the discharge pipe 25a and the gas side end of the first heat exchange section 31.

[0084] In the switching unit 70 (hereinafter also referred to as "heating-side switching unit 70") corresponding to the indoor unit 120 performing heating operation (hereinafter also referred to as "heating-side indoor unit 120") among the indoor units 120 in operation, the first valve EV1 is fully opened, the second valve EV2 is fully closed, the third valve EV3 is fully closed, the indoor expansion valve 51 of the heating-side indoor unit 120 is fully opened, and the opening degrees of the first outdoor expansion valve 34 and the second outdoor expansion valve 35 are adjusted. In this embodiment, the indoor unit 120 in the first space S11 (cooling-side indoor unit 120) is in cooling operation, and the indoor unit 120 in the second space S12 (heating-side indoor unit 120) is in heating operation. In this case, in the heat recovery unit 130 provided for the first space S11, the supply side auxiliary heat exchanger 131 functions as an evaporator in accordance with the cooling side indoor unit 120 of the first space S11, and the exhaust side auxiliary heat exchanger 132 functions as a condenser.

[0085] When the compressor 25 is driven, a part of the high-pressure gas refrigerant compressed by the compressor 25 flows into the second connecting pipe 12 through the discharge pipe 25a and the second flow path switching valve 27. Another part of the high-pressure gas refrigerant compressed by the compressor 25 flows through the discharge pipe 25a and the third flow path switching valve 28 and is condensed in the first heat exchange section 31 of the outdoor heat exchanger 30, a part of it flows into the first connecting pipe 11 through the first outdoor expansion valve 34, and the rest flows into the second outdoor expansion valve 35. The refrigerant condensed in the first heat exchange section 31 passes through the second outdoor expansion valve 35 and evaporates in the second heat exchange section 32, and is sucked into the compressor 25 through the first flow path switching valve 26. In the cooling and heating mixed operation, the usage of the second heat exchange section 32 is changed according to the balance between the condensation amount and evaporation amount of the refrigerant in the indoor unit 120 and the heat recovery unit 130. In the mixed cooling and heating operation, depending on the balance between the condensation amount and evaporation amount of the refrigerant in the indoor unit 120 and the heat recovery unit 130, both the first heat exchange section 31 and the second heat exchange section 32 function as a condenser or an evaporator.

[0086] The refrigerant that flows into the second connecting pipe 12 flows into the second header pipe 56 of the refrigerant flow path switching device 140, flows through the first refrigerant pipe P1 of the heating side switching unit 70, the first valve EV1, and the usage side gas piping 61, and flows into the gas pipe GP.

[0087] The refrigerant that has flowed into the gas pipe GP is condensed in the indoor heat exchanger 52 of the heating-side indoor unit 120. The condensed refrigerant flows from the liquid pipe LP into the utilization-side liquid piping 62 of the heating-side switching unit 70, and flows through the subcooling heat exchanger 59 and the fourth refrigerant pipe P4, before flowing into the first header pipe 55.

[0088] The refrigerant that flows from the outdoor unit 110 into the first connecting pipe 11 also flows into the first header pipe 55. The refrigerant that flows into the first header pipe 55 flows through the fourth refrigerant pipe P4 of the cooling-side switching unit 70, the subcooling heat exchanger 59, the utilization-side liquid piping 62, and the liquid pipe LP, and then flows into the cooling-side indoor unit 120. At this time, the refrigerant that has passed through the subcooling heat exchanger 59 branches off from the fourth refrigerant pipe P4, flows through the fifth refrigerant pipe P5, and is subcooled by the refrigerant decompressed by the third valve EV3.

[0089] The refrigerant that flows into the cooling-side indoor unit 120 is decompressed in the indoor expansion valve 51 and evaporates in the indoor heat exchanger 52, cooling the room. The evaporated refrigerant flows through the gas pipe GP and flows into the usage-side gas piping 61 of the cooling-side switching unit 70, passes through the second valve EV2, flows into the third refrigerant pipe P3 and the third header pipe 57, flows through the third connection pipe 13, flows into the accumulator 24, and is sucked into the compressor 25.

[0090] In the heat recovery unit 130, the supply air side auxiliary heat exchanger 131 functions as an evaporator in accordance with the cooling side indoor unit 120 in the first space S11, cools the outdoor air OA, and supplies the supply air SA to the indoor space S11. In the heat recovery unit 130, the exhaust air side auxiliary heat exchanger 132 functions as a condenser, recovers heat from the return air RA to evaporate the gas refrigerant, and releases the heated return air RA to the outdoor space S2 as exhaust air EA.

[0091] [About defrost operation] In the air conditioning system 100, when the above-mentioned heating only operation is performed, frost may form on the surface of the outdoor heat exchanger 30, which serves as an evaporator. The air conditioning system 100 is configured to be able to perform a defrost operation that defrosts the outdoor heat exchanger 30. In the defrost operation, a refrigeration cycle (defrost cycle) is performed in which the refrigerant releases heat and condenses in the outdoor heat exchanger 30 of the outdoor unit 110, and evaporates in the indoor heat exchanger 52 of each indoor unit 120. In addition, before switching from the heating only operation to the defrost operation, a preparation operation is performed.

[0092] (Preparatory run) When the control unit determines that a condition indicating that frost has formed on the surface of the outdoor heat exchanger 30 has been met during heating operation, the control unit starts a preparatory operation for transitioning from full heating operation to defrost operation in the air conditioning system 100. The condition indicating that frost has formed on the surface of the outdoor heat exchanger 30 is determined based on, for example, the temperature and pressure of the refrigerant flowing through the outdoor heat exchanger 30, the temperature of air passing through the outdoor heat exchanger 30, the duration of heating operation, etc. The preparatory operation is performed for a predetermined time, and then the operation transitions to defrost operation.

[0093] In preparatory operation, the air conditioning system 100 gradually reduces the rotation speed of the compressor 25 and then stops it. In preparatory operation, the air conditioning system 100 reduces the opening of the indoor expansion valve 51 as the rotation speed of the compressor 25 decreases. In preparatory operation, the air conditioning system 100 maintains the states of the flow path switching valves 26, 27, and 28 during heating only operation. The air conditioning system 100 maintains the basic refrigerant flow in preparatory operation as in heating only operation.

[0094] (Defrost operation) The air conditioning system 100 executes a defrost operation when a predetermined time has elapsed after the start of the preparation operation. When the defrost operation starts, each of the flow path switching valves 26, 27, 28 is switched by the control unit. When the defrost operation starts, the indoor fan 53 of the indoor unit 120 is turned off. The first flow path switching valve 26 of the outdoor unit 110 connects the discharge pipe 25a to the gas side end of the second heat exchange section 32. The second flow path switching valve 27 connects the refrigerant pipe 25c to the second connection pipe 12. The third flow path switching valve 28 connects the discharge pipe 25a to the gas side end of the first heat exchange section 31.

[0095] In defrost operation, the openings of the first valve EV1 and the second valve EV2 of the switching unit 70 are adjusted. The third valve EV3 is fully closed. The openings of the indoor expansion valve 51 are adjusted. The openings of the first and second outdoor expansion valves 34, 35 are adjusted. The first shutoff valve 161 is fully closed. The second and third shutoff valves 162, 163 are fully open.

[0096] During the defrost operation, the following refrigeration cycle (defrost cycle) is performed. When the defrost operation starts, the rotation speed of the compressor 25 gradually increases to the target rotation speed. Immediately after the start of the defrost operation, the indoor expansion valve 51 is opened at a predetermined opening degree.

[0097] When the compressor 25 is driven, the high-pressure gas refrigerant compressed by the compressor 25 flows into the outdoor heat exchanger 30 (first heat exchange section 31 and second heat exchange section 32) via the discharge pipe 25a, the first flow path switching valve 26, and the third flow path switching valve 28. In the outdoor heat exchanger 30, the refrigerant dissipates heat to the frost adhering to the surface of the outdoor heat exchanger 30. This causes the frost on the surface of the outdoor heat exchanger 30 to melt. The refrigerant that has flowed into the outdoor heat exchanger 30 and dissipated heat and condensed flows into the first connecting pipe 11 and the first header pipe 55 via the first outdoor expansion valve 34 and the second outdoor expansion valve 35.

[0098] In defrost operation, the indoor expansion valve 51 is opened at a predetermined opening degree, so that the refrigerant flows from the first connecting pipe 11, the first header pipe 55, the fourth refrigerant pipe P4, the first heat transfer pipe 59a, the utilization side liquid piping 62, and the liquid pipe LP through the indoor expansion valve 51 to the indoor unit 120. The refrigerant is decompressed by the indoor expansion valve 51, and then evaporates in the indoor heat exchanger 52. Since the indoor heat exchanger 52 is inside the indoor unit 120, the evaporation of the refrigerant does not have much effect on the temperature of the indoor space. In this embodiment, since the indoor fan 53 is stopped during defrost operation, this effect is smaller.

[0099] The gas refrigerant evaporated in the indoor heat exchanger 52 flows through the gas pipe GP, the utilization side gas piping 61, the second valve EV2, the third refrigerant pipe P3, the third header pipe 57, and the third connecting pipe 13, and also flows through the gas pipe GP, the utilization side gas piping 61, the second refrigerant pipe P2, the first valve EV1, the first refrigerant pipe P1, the second header pipe 56, and the second connecting pipe 12, flows into the outdoor unit 110, and is sucked into the compressor 25 via the accumulator 24.

[0100] During the defrost operation, if the control unit 115 determines that the conditions for completing the defrosting of the outdoor heat exchanger 30 are met, the air conditioning system 100 ends the defrost operation and resumes normal operation (full heating operation). The conditions for completing the defrosting of the outdoor heat exchanger 30 are determined based on, for example, the temperature and pressure of the refrigerant flowing through the outdoor heat exchanger 30, the temperature of the air passing through the outdoor heat exchanger 30, the duration of the defrost operation, etc.

[0101] (Processing by the heat recovery unit during defrost operation) In air conditioning system 100, during defrost operation, control unit 115 (see FIG. 7) fully closes first shut-off valve 161, fully opens second shut-off valve 162, and fully opens third shut-off valve 163, stops supply air fan 137, and operates exhaust fan 138.

[0102] For this reason, in the air conditioning system 100, during defrost operation, the liquid refrigerant flowing through the first connecting pipe 11 can be made to flow into the auxiliary refrigerant circuit RC2 via the bypass pipe 16. The liquid refrigerant that flows from the bypass pipe 16 to the second auxiliary refrigerant pipe 135b flows into the exhaust side auxiliary heat exchanger 132. The liquid refrigerant exchanges heat with the exhaust air EA in the exhaust side auxiliary heat exchanger 132 and evaporates. The evaporated gas refrigerant flows through the first auxiliary refrigerant pipe 135a, the auxiliary heat exchanger switching valve 133, and the second branch pipe 15, flows into the outdoor unit 110, and is sucked into the compressor 25 via the accumulator 24.

[0103] In the air conditioning system 100, heat can be recovered from the exhaust air EA during defrost operation, and therefore the efficiency of operation during defrost operation can be improved. In the air conditioning system 100, the amount of refrigerant flowing through the heat source side refrigerant circuit RC1 during defrost operation can be increased, and therefore the frost adhering to the outdoor heat exchanger 30 can be removed in a shorter time. This shortens the time required for the defrost operation, and by shortening the period during which air conditioning is not performed in the first space S11, the comfort level of the user in the first space S11 can be improved.

[0104] In the air conditioning system 100, the supply air fan 137 can be stopped during the defrost operation. Therefore, in the air conditioning system 100, it is possible to prevent low-temperature outside air OA from being supplied to the first space S11 during the defrost operation.

[0105] In the air conditioning system 100, the motor-operated valve 136 is closed by the control unit 115 (see FIG. 7) during defrost operation. This makes it possible to block the supply of liquid refrigerant flowing from the bypass pipe 16 into the auxiliary refrigerant piping 135 to the air supply side auxiliary heat exchanger 131 side. Therefore, in the air conditioning system 100, the outside air OA is cooled by heat exchange in the air supply side auxiliary heat exchanger 131 during defrost operation, and it is possible to reliably prevent the cooled outside air OA from flowing into the first space S11.

[0106] In the air conditioning system 100, the first shutoff valve 161 is closed by the control unit 115 (see FIG. 7) during defrost operation. This makes it possible to more reliably shut off the supply of liquid refrigerant flowing from the bypass pipe 16 into the auxiliary refrigerant piping 135 to the air supply side auxiliary heat exchanger 131 side. Therefore, in the air conditioning system 100, the outside air OA is cooled by heat exchange in the air supply side auxiliary heat exchanger 131 during defrost operation, and it is possible to more reliably prevent the cooled outside air OA from flowing into the first space S11.

[0107] [Effects of the embodiment] The air conditioning system 100 in the above-described embodiment includes an outdoor unit 110 having a heat source side refrigerant circuit RC1 including a compressor 25 and an outdoor heat exchanger 30, an indoor unit 120 arranged in the first space S11 and having an indoor heat exchanger 52, a switching unit 70 having an intermediate refrigerant circuit RC3 for causing each indoor heat exchanger 52 to function individually as an evaporator or a condenser, an auxiliary refrigerant circuit RC2 including a supply air side auxiliary heat exchanger 131 and an exhaust air side auxiliary heat exchanger 132 connected in series to the supply air side auxiliary heat exchanger 131 by an auxiliary refrigerant piping 135, and a refrigerant circuit RC3 for supplying outdoor air that has passed through the supply air side auxiliary heat exchanger 131 to the first space S11. the heat source side refrigerant circuit RC1 and the intermediate refrigerant circuit RC3 are connected by a first connecting pipe 11 through which liquid refrigerant flows, a second connecting pipe 12 through which high-pressure gas refrigerant flows, and a third connecting pipe 13 through which low-pressure gas refrigerant flows, and the auxiliary refrigerant circuit RC2 is connected to the first connecting pipe 11 and the second connecting pipe 12 between the heat source side refrigerant circuit RC1 and the intermediate refrigerant circuit RC3, and is provided with a bypass pipe 16 connecting the auxiliary refrigerant piping 135 and the first connecting pipe 11.

[0108] In the above-described configuration, by providing the bypass pipe 16 that connects the first connecting pipe 11 and the auxiliary refrigerant pipe 135, the liquid refrigerant can be returned from the bypass pipe 16 to the third connecting pipe 13 through the exhaust side auxiliary heat exchanger 132. This makes it possible to recover heat from the exhaust air EA by utilizing the exhaust side auxiliary heat exchanger 132 during the defrosting operation of the outdoor heat exchanger 30.

[0109] The air conditioning system 100 in the present embodiment described above further includes an electric valve 136 provided on the auxiliary refrigerant piping 135 closer to the air supply side auxiliary heat exchanger 131 than the connection position P of the auxiliary refrigerant piping 135 and the bypass pipe 16. During defrost operation for defrosting the outdoor heat exchanger 30, the air conditioning system 100 has the second connecting pipe 12 connected to the air supply side auxiliary heat exchanger 131 and the third connecting pipe 13 connected to the exhaust side auxiliary heat exchanger 132, and the control unit 115 closes the electric valve 136. According to this configuration, during the defrost operation for defrosting the outdoor heat exchanger 30, it is possible to prevent the liquid refrigerant from flowing toward the air supply side auxiliary heat exchanger 131. As a result, during the defrost operation, the liquid refrigerant can be reliably returned from the bypass pipe 16 to the third connecting pipe 13 through the exhaust side auxiliary heat exchanger 132. In this case, it is possible to prevent the cold air that has been heat exchanged by the air supply side auxiliary heat exchanger 131 from being supplied to the first space S11 by the air supply fan 137. Also in this case, it is possible to shorten the time from the start to the completion of the defrost operation.

[0110] The air conditioning system 100 in the present embodiment described above further includes a first shutoff valve 161 provided on the first branch pipe 14 connecting the second connecting pipe 12 and the intake side auxiliary heat exchanger 131. During defrost operation for defrosting the outdoor heat exchanger 30, the air conditioning system 100 has the second connecting pipe 12 and the intake side auxiliary heat exchanger 131 connected and the third connecting pipe 13 and the exhaust side auxiliary heat exchanger 132 connected, and the control unit 115 closes the first shutoff valve 161. According to this configuration, it is possible to reliably prevent the liquid refrigerant from flowing toward the intake air side auxiliary heat exchanger 131 during the defrost operation.

[0111] In the air conditioning system 100 of the above-described embodiment, during defrost operation to defrost the outdoor heat exchanger 30, the second connecting pipe 12 is connected to the supply side auxiliary heat exchanger 131 and the third connecting pipe 13 is connected to the exhaust side auxiliary heat exchanger 132, and the control unit 115 operates the exhaust fan 138 and stops the supply fan 137. According to this configuration, the exhaust side auxiliary heat exchanger 132 can recover heat from the exhaust air EA in the first space S11 during the defrost operation.

[0112] The air conditioning system 100 in the present embodiment described above uses R32, which is a flammable refrigerant, as the refrigerant. The air conditioning system 100 further includes a second shutoff valve 162 provided on the second branch pipe 15 that connects the third connection pipe 13 and the exhaust side auxiliary heat exchanger 132, and a third shutoff valve 163 provided on the bypass pipe 16. According to this configuration, the heat source side refrigerant circuit RC1 and the auxiliary refrigerant circuit RC2 can be completely separated by closing the first to third shutoff valves 161, 162, and 163. As a result, in the event that refrigerant leaks from the heat recovery unit 130, the amount of refrigerant leaking from the heat recovery unit 130 can be suppressed. [Explanation of symbols]

[0113] 11: First connecting pipe 12: Second connecting pipe 13: 3rd Interconnect Pipe 16: Bypass pipe 25: Compressor 30: Outdoor heat exchanger (1st heat exchanger) 52: Indoor heat exchanger (second heat exchanger, third heat exchanger) 70: Intermediate unit RC1: Heat source side refrigerant circuit (first refrigerant circuit) RC2: Auxiliary refrigerant circuit RC3: Intermediate refrigerant circuit 100: Air conditioning systems 110: Outdoor unit (first unit) 115: Control unit 120: Indoor unit (second unit) 130: Heat recovery unit 131: Supply side auxiliary heat exchanger (1st auxiliary heat exchanger) 132: Exhaust side auxiliary heat exchanger (second auxiliary heat exchanger) 135: Auxiliary refrigerant piping (first refrigerant piping) 136: Motor-operated valve 137: Supply fan 138: Exhaust fan 151: Air supply passage 152: Exhaust passage 161: First shutoff valve 162: Second shutoff valve 163: 3rd shutoff valve S11: 1st space P: Connection position

Claims

1. A first unit (110) having a first refrigerant circuit (RC1) including a compressor (25) and a first heat exchanger (30); a second unit (120) disposed in the first space (S11) and having a second heat exchanger (52); a third unit (120) having a third heat exchanger (52); an intermediate unit (70) having an intermediate refrigerant circuit (RC3) for allowing the second heat exchanger (52) and the third heat exchanger (52) to function individually as an evaporator or a condenser; a heat recovery unit (130) including an auxiliary refrigerant circuit (RC2) including a first auxiliary heat exchanger (131) and a second auxiliary heat exchanger (132) connected in series to the first auxiliary heat exchanger (131) by a first refrigerant pipe (135), an air supply fan (137) that supplies outside air that has passed through the first auxiliary heat exchanger (131) to the first space (S11), and an exhaust fan (138) that discharges the air of the first space (S11) that has passed through the second auxiliary heat exchanger (132) to the outside; A control unit (115) for controlling the operation of the heat recovery unit (130); Equipped with the first refrigerant circuit (RC1) and the intermediate refrigerant circuit (RC3) are connected by a first communication pipe (11) through which a liquid refrigerant flows, a second communication pipe (12) through which a high-pressure gas refrigerant flows, and a third communication pipe (13) through which a low-pressure gas refrigerant flows, the auxiliary refrigerant circuit (RC2) is connected to the second communication pipe (12) and the third communication pipe (13) between the first refrigerant circuit (RC1) and the intermediate refrigerant circuit (RC3), The air conditioning system (100) comprises a bypass pipe (16) that connects the first refrigerant piping (135) and the first connecting pipe (11) and through which liquid refrigerant flows when a defrost operation is performed.

2. a motor-operated valve (136) provided on the first refrigerant pipe (135) on the first auxiliary heat exchanger (131) side relative to a connection position (P) between the first refrigerant pipe (135) and the bypass pipe (16), During a first operation for defrosting the first heat exchanger (30), the second connecting pipe (12) and the first auxiliary heat exchanger (131) are connected, and the third connecting pipe (13) and the second auxiliary heat exchanger (132) are connected, The air conditioning system (100) of claim 1, wherein the control (115) causes the motorized valve (136) to close.

3. The system further includes a first shutoff valve (161) provided on a pipe (14) connecting the second connecting pipe (12) and the first auxiliary heat exchanger (131), During a first operation for defrosting the first heat exchanger (30), the second connecting pipe (12) and the first auxiliary heat exchanger (131) are connected, and the third connecting pipe (13) and the second auxiliary heat exchanger (132) are connected, The air conditioning system according to claim 1 or 2, wherein the control unit (115) closes the first shutoff valve (161).

4. During a first operation for defrosting the first heat exchanger (30), the third connecting pipe (13) and the second auxiliary heat exchanger (132) are connected, and the second connecting pipe (12) and the first auxiliary heat exchanger (131) are connected, The air conditioning system (100) according to any one of claims 1 to 3, wherein the control unit (115) operates the exhaust fan (138) and stops the supply fan (137).

5. The refrigerant is a flammable refrigerant, The air conditioning system (100) according to any one of claims 1 to 4, further comprising: a second shutoff valve (162) provided on a pipe (15) connecting the second connecting pipe (12) and the second auxiliary heat exchanger (132); and a third shutoff valve (163) provided on the bypass pipe (16).

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