Air conditioning device

Abstract

Provided is an air conditioning device capable of reducing the amount of refrigerant to be filled. An air conditioning device (1) is provided with: an indoor heat exchanger (31); an outdoor heat exchanger (40); and a four-way reversing valve (22) that switches between a heating operation in which the indoor heat exchanger (31) functions as a condenser for the refrigerant and the outdoor heat exchanger (40) functions as an evaporator for the refrigerant, and a cooling operation in which the outdoor heat exchanger (40) functions as an evaporator for the refrigerant. In the cooling operation, the indoor heat exchanger (31) acts as an evaporator for a refrigerant and the outdoor heat exchanger (40) acts as a condenser for the refrigerant, and the inner volume of the indoor heat exchanger (31) is smaller than the inner volume of the outdoor heat exchanger (40). The inner volume of a region through which the refrigerant flows in the outdoor heat exchanger (40) during the cooling operation is smaller than the inner volume of a region through which the refrigerant flows in the outdoor heat exchanger (40) during the heating operation.

Description

Technical Field

[0001] The present disclosure relates to an air conditioning device. Background Art

[0002] In recent years, from the viewpoint of protecting the global environment, the introduction of air-conditioning devices that perform heating operation using air as a heat source has been promoted also in cold regions.

[0003] As an air-conditioning device used in such cold regions, for example, an air-conditioning device described in Patent Document 1 (International Publication No. 2020 / 208776) has been proposed that adjusts the heating capacity according to the indoor heating load. Summary of the invention Technical problem to be solved by the invention

[0004] In order to ensure sufficient heating performance even in cold regions where the outside air temperature is low, an air conditioner with a large outdoor heat exchanger acting as an evaporator is sometimes used. When such an air conditioner is used for cooling operation, the outdoor heat exchanger acts as a condenser of the refrigerant, but a large amount of liquid refrigerant exists in the large outdoor heat exchanger, and the amount of refrigerant filled in the refrigerant circuit is likely to increase. Technical solutions adopted to solve technical problems

[0005] The air conditioning device of the first viewpoint includes a first heat exchanger, a second heat exchanger and a switching unit. The switching unit switches between a first operation and a second operation. The first operation causes the first heat exchanger to function as a condenser of the refrigerant and causes the second heat exchanger to function as an evaporator of the refrigerant. The second operation causes the first heat exchanger to function as an evaporator of the refrigerant and causes the second heat exchanger to function as a condenser of the refrigerant. The internal volume of the first heat exchanger is smaller than the internal volume of the second heat exchanger. The internal volume of the area through which the refrigerant flows in the second heat exchanger during the second operation is smaller than the internal volume of the area through which the refrigerant flows in the second heat exchanger during the first operation.

[0006] In the first operation, the air conditioner makes the second heat exchanger having a larger internal volume than the first heat exchanger function as an evaporator of the refrigerant, so that it is easy to ensure the capacity in the first operation. In addition, in the air conditioner, the internal volume of the area through which the refrigerant flows in the second heat exchanger in the second operation in which the second heat exchanger functions as a condenser of the refrigerant is smaller than the internal volume of the area through which the refrigerant flows in the second heat exchanger in the first operation. Therefore, the amount of liquid refrigerant retained in the second heat exchanger in the second operation can be suppressed to a small amount. Therefore, the amount of refrigerant filled in the air conditioner can be reduced.

[0007] The air conditioning apparatus according to a second aspect is the air conditioning apparatus according to the first aspect, wherein the second heat exchanger is an air heat exchanger that exchanges heat between the refrigerant flowing inside and the air flowing outside.

[0008] In this air conditioning device, since the internal volume of the second heat exchanger is larger than that of the first heat exchanger, it is easy to ensure capacity even when the refrigerant flowing through the second heat exchanger functioning as an evaporator exchanges heat with the low-temperature outside air in a cold area during the first operation.

[0009] The air conditioner according to the third aspect is the air conditioner according to the second aspect, further comprising an air supply unit capable of supplying air flow to the entire second heat exchanger.

[0010] In this air conditioning device, since the air flow is supplied to the entire second heat exchanger, it is easy to ensure the heat exchange amount.

[0011] An air conditioning apparatus according to a fourth aspect is the air conditioning apparatus according to the third aspect, wherein in the second operation, flow paths through which the refrigerant flows through the second heat exchanger do not overlap when viewed from the direction of the air flow formed by the air supply unit.

[0012] Even when the internal volume of the refrigerant passing region of the second heat exchanger during the second operation is smaller than the internal volume of the refrigerant passing region of the second heat exchanger during the first operation, the air conditioning apparatus can perform heat exchange efficiently.

[0013] The air conditioning apparatus according to a fifth aspect is the air conditioning apparatus according to any one of the first to fourth aspects, wherein during the first operation, the refrigerant flows through the entire internal volume of the second heat exchanger.

[0014] This air conditioning apparatus can easily ensure the capacity of the second heat exchanger functioning as an evaporator during the first operation.

[0015] An air conditioning apparatus according to a sixth aspect is the air conditioning apparatus according to any one of the first to fourth aspects, wherein during the first operation, the second heat exchanger has two or more flow paths through which the refrigerant flows.

[0016] This air conditioning apparatus can reduce the pressure loss in the second heat exchanger functioning as an evaporator during the first operation.

[0017] The air conditioner of a seventh aspect is the air conditioner of any one of the first to sixth aspects, wherein the second heat exchanger has a plurality of heat transfer tubes. During the second operation, the second heat exchanger has one or more heat transfer tubes through which no refrigerant flows.

[0018] This air conditioning apparatus can suppress the amount of liquid refrigerant held in the second heat exchanger to be low during the second operation in which the second heat exchanger functions as a condenser of the refrigerant.

[0019] An air conditioning apparatus according to an eighth aspect is the air conditioning apparatus according to any one of the first to seventh aspects, wherein the internal volume of the first heat exchanger is not more than 2 / 3 of the internal volume of the second heat exchanger.

[0020] This air conditioning apparatus can suppress the amount of refrigerant to be filled to a small level even when the internal volume of the second heat exchanger is large.

[0021] An air conditioning apparatus according to a ninth aspect is the air conditioning apparatus according to any one of the first to eighth aspects, wherein the second heat exchanger is a heat source side heat exchanger, and the first heat exchanger is a utilization side heat exchanger.

[0022] In this air conditioning device, a large amount of heat can be obtained in the second heat exchanger having a larger internal volume than the first heat exchanger during the first operation.

[0023] An air conditioning apparatus according to a tenth aspect is the air conditioning apparatus according to any one of the first to ninth aspects, wherein the refrigerant is a flammable refrigerant.

[0024] This air conditioning apparatus can reduce the filling amount of a flammable refrigerant even when using the refrigerant.

[0025] An air-conditioning apparatus according to an eleventh aspect is the air-conditioning apparatus according to the tenth aspect, wherein the combustible refrigerant contains one or two or more selected from the group consisting of R290, R600, and R600a.

[0026] The air conditioning device can reduce the risk of fire even when using a flammable refrigerant. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the refrigerant circuit. Figure 2 This is a schematic control structure block diagram of an air conditioning device. Figure 3 This is a schematic external configuration diagram of an outdoor heat exchanger according to another embodiment A. Figure 4 1 is a diagram showing the flow of refrigerant during heating operation of the outdoor heat exchanger according to another embodiment A. FIG. DETAILED DESCRIPTION

[0028] Referring to the schematic diagram of the refrigerant circuit below, Figure 1 and as a schematic control structure diagram Figure 2 , the air conditioning device 1 is described.

[0029] The air conditioner 1 is a refrigeration cycle device that performs a vapor compression refrigeration cycle to condition the air of a target space. The air conditioner 1 of this embodiment can be used in cold regions where the heating load is greater than the cooling load throughout the year.

[0030] The air conditioning device 1 mainly includes an outdoor unit 20, an indoor unit 30, a liquid side refrigerant connecting pipe 6 and a gas side refrigerant connecting pipe 5 connecting the outdoor unit 20 and the indoor unit 30, a heat load circuit 50, a remote controller not shown as an input device and an output device, and a controller 7 for controlling the operation of the air conditioning device 1.

[0031] In the air-conditioning device 1, the refrigerant sealed in the refrigerant circuit 10 is compressed, cooled or condensed, decompressed, heated or evaporated, and then compressed again in a refrigeration cycle. In the present embodiment, the refrigerant circuit 10 is filled with a refrigerant for performing a vapor compression refrigeration cycle. The refrigerant is a flammable refrigerant. As a flammable refrigerant, for example, highly flammable refrigerants of grades A3 and B3 in the ASHRAE Safety Group (ASHRAE Safety Group), flammable refrigerants of grades A2 and B2, and slightly flammable refrigerants of grades A2L and B2L can be listed. More specifically, the refrigerant can be one or more selected from the group consisting of R290, R600 and R600a. In addition, in the present embodiment, the refrigerant circuit 10 is filled with a refrigerant having a specific gravity greater than that of air. In addition, refrigerator oil is filled in the refrigerant circuit 10 together with the mixed refrigerant.

[0032] (1) Outdoor unit 20 The outdoor unit 20 is connected to the indoor unit 30 through the liquid-side refrigerant communication pipe 6 and the gas-side refrigerant communication pipe 5, and constitutes a part of the refrigerant circuit 10. The outdoor unit 20 mainly includes a compressor 21, a four-way reversing valve 22, an outdoor heat exchanger 40, a first opening and closing valve 43, a second opening and closing valve 44, an outdoor expansion valve 24, an outdoor fan 25, a storage tank 49, a liquid-side stop valve 29, and a gas-side stop valve 28. In the present embodiment, the outdoor unit 20 is arranged outdoors.

[0033] The compressor 21 is a device that compresses the low-pressure refrigerant in the refrigeration cycle to a high pressure. Here, as the compressor 21, a closed-type compressor in which a positive displacement compression element (not shown) such as a rotary type or a scroll type is driven to rotate by a compressor motor is used. The compressor motor is used to change the capacity, and the operating frequency can be controlled by an inverter.

[0034] The four-way reversing valve 22 switches the cooling operation connection state and the heating operation connection state by switching the connection state. In the cooling operation connection state, the four-way reversing valve 22 connects the discharge side of the compressor 21 to the outdoor heat exchanger 40, and connects the suction side of the compressor 21 to the gas side stop valve 28. More specifically, in the cooling operation connection state, the discharge side of the compressor 21 is connected to a branching point A described later. In addition, the four-way reversing valve 22 connects the discharge side of the compressor 21 to the gas side stop valve 28, and connects the suction side of the compressor 21 to the outdoor heat exchanger 40 in the heating operation connection state. More specifically, in the heating operation connection state, the suction side of the compressor 21 is connected to a branching point A described later.

[0035] The accumulator 49 is provided between the four-way switching valve 22 and the suction side of the compressor 21. Thus, the compressor 21 is prevented from sucking in the refrigerant in a liquid state.

[0036] The outdoor heat exchanger 40 is a heat source side heat exchanger that partially functions as a condenser of high-pressure refrigerant in the refrigeration cycle during cooling operation, and functions as an evaporator of low-pressure refrigerant in the refrigeration cycle as a whole during heating operation. The outdoor heat exchanger 40 includes a first outdoor heat exchanger 41 and a second outdoor heat exchanger 42 connected in parallel to each other in the refrigerant circuit 10. The first outdoor heat exchanger 41 and the second outdoor heat exchanger 42 in the outdoor heat exchanger 40 are both air heat exchangers that perform heat exchange between the refrigerant flowing inside and the air passing outside. The first outdoor heat exchanger 41 and the second outdoor heat exchanger 42 in the outdoor heat exchanger 40 each include a plurality of heat transfer tubes connected to a header and a plurality of fins fixed to the plurality of heat transfer tubes. The internal volume of the outdoor heat exchanger 40 is larger than the internal volume of the indoor heat exchanger 31, and may be 1.5 times or more of the internal volume of the indoor heat exchanger 31, and preferably 2.0 times or more of the internal volume of the indoor heat exchanger 31. The internal volume of the outdoor heat exchanger 40 may be, for example, 3 L or more and 10 L or more, or 4 L or more and 7 L or less. The internal volume of the outdoor heat exchanger 40 is the sum of the internal volume of the first outdoor heat exchanger 41 and the internal volume of the second outdoor heat exchanger 42. The internal volume of the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42 refers to the volume of the fluid when the fluid is filled in the header and the heat transfer tube.

[0037] In the present embodiment, during cooling operation, the first outdoor heat exchanger 41 functions as a condenser of high-pressure refrigerant in the refrigeration cycle, and during heating operation, both the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42 function as evaporators of low-pressure refrigerant in the refrigeration cycle. The first outdoor heat exchanger 41 is disposed between the four-way reversing valve 22 and the outdoor expansion valve 24. A branching point A for branching the refrigerant flow path is disposed between the four-way reversing valve 22 and the end of the first outdoor heat exchanger 41 on the gas refrigerant side. A branching point B for branching the refrigerant flow path is disposed between the end of the first outdoor heat exchanger 41 on the liquid refrigerant side and the outdoor expansion valve 24. The end of the second outdoor heat exchanger 42 on the gas refrigerant side is connected to the branching point A, and the end of the second outdoor heat exchanger 42 on the liquid refrigerant side is connected to the branching point B, so that the second outdoor heat exchanger 42 is connected in parallel with the first outdoor heat exchanger 41. A first on-off valve 43 is provided between the gas refrigerant side end of the second outdoor heat exchanger 42 and the branch point A. A second on-off valve 44 is provided between the liquid refrigerant side of the second outdoor heat exchanger 42 and the branch point B.

[0038] The outdoor fan 25 generates an air flow for sucking outdoor air into the outdoor unit 20 and discharging it to the outside after heat exchange with the refrigerant in the outdoor heat exchanger 40. The outdoor fan 25 is driven to rotate by an outdoor fan motor. In the present embodiment, the outdoor fan 25 is configured to have a plurality of fans. The outdoor fan 25 including the plurality of fans supplies the air flow formed by the drive to the entire outdoor heat exchanger 40. More specifically, the air flow formed by the outdoor fan 25 is supplied to the entire first outdoor heat exchanger 41 and is also supplied to the entire second outdoor heat exchanger 42. In addition, in the present embodiment, the first outdoor heat exchanger 41 is arranged on the upwind side of the second outdoor heat exchanger 42 in the direction of the air flow formed by the outdoor fan 25.

[0039] The outdoor expansion valve 24 is provided between the liquid side end of the outdoor heat exchanger 40 and the liquid side stop valve 29. The outdoor expansion valve 24 may be a mechanical expansion valve used with a capillary tube or a temperature sensing tube, but is preferably an electric expansion valve capable of adjusting the valve opening by control.

[0040] The liquid-side stop valve 29 is a manual valve disposed at a connection portion of the outdoor unit 20 with the liquid-side refrigerant communication pipe 6 .

[0041] The gas-side stop valve 28 is a manual valve disposed at a connection portion of the outdoor unit 20 with the gas-side refrigerant communication pipe 5 .

[0042] The outdoor unit 20 has an outdoor unit control unit 27 that controls the operation of each part constituting the outdoor unit 20. The outdoor unit control unit 27 has a microcomputer including a processor such as a CPU (central processing unit) and a memory such as a ROM and a RAM, etc. The outdoor unit control unit 27 is connected to the indoor unit control unit 34 of each indoor unit 30 via a communication line, and transmits / receives control signals, etc.

[0043] The outdoor unit 20 is provided with a discharge pressure sensor 61, a discharge temperature sensor 62, a suction pressure sensor 63, a suction temperature sensor 64, a first outdoor heat exchange temperature sensor 65, a second outdoor heat exchange temperature sensor 66, and an external air temperature sensor 67. Each of the above sensors is electrically connected to the outdoor unit control unit 27 and sends a detection signal to the outdoor unit control unit 27. The discharge pressure sensor 61 detects the pressure of the refrigerant flowing in the discharge piping connecting the discharge side of the compressor 21 to one of the connection ports of the four-way reversing valve 22. The discharge temperature sensor 62 detects the temperature of the refrigerant flowing in the discharge piping. The suction pressure sensor 63 detects the pressure of the refrigerant flowing in the suction piping connecting the suction side of the compressor 21 to one of the connection ports of the four-way reversing valve 22. The suction temperature sensor 64 detects the temperature of the refrigerant flowing in the suction piping. The first outdoor heat exchange temperature sensor 65 detects the temperature of the refrigerant flowing between the liquid refrigerant side end of the first outdoor heat exchanger 41 and the branching point B. The second outdoor heat exchange temperature sensor 66 detects the temperature of the refrigerant flowing between the liquid refrigerant side end of the second outdoor heat exchanger 42 and the branch point B. The outside air temperature sensor 67 detects the temperature of the outdoor air before passing through the outdoor heat exchanger 40 .

[0044] (2) Heat load circuit 50 The heat load circuit 50 is a circuit in which a heat medium as a fluid circulates. The heat medium is not particularly limited, and examples thereof include fluids such as water and salt water.

[0045] The heat load circuit 50 includes a heat load unit 51 and a pump 52 .

[0046] The heat load unit 51 is a part that handles the cooling load during cooling operation and a part that handles the heating load during heating operation. The heat load unit 51 may include, for example, a floor heating panel during heating operation and a coil portion of a fan coil unit for providing cold air using a blower fan during cooling operation.

[0047] The pump 52 circulates the heat medium in the heat load circuit 50 and can control the flow rate.

[0048] During cooling operation, in the heat load circuit 50, the heat medium cooled by exchanging heat with the refrigerant in the indoor heat exchanger 31 is supplied to the heat load unit 51. The heat medium heated by handling the cooling load in the heat load unit 51 is supplied to the indoor heat exchanger 31 again.

[0049] During heating operation, in the heat load circuit 50, the heat medium heated by exchanging heat with the refrigerant in the indoor heat exchanger 31 is supplied to the heat load unit 51. The heat medium cooled by handling the heating load in the heat load unit 51 is supplied to the indoor heat exchanger 31 again.

[0050] (3) Indoor unit 30 The indoor unit 30 is installed near the air-conditioned space and is connected to the outdoor unit 20 via the liquid-side refrigerant communication pipe 6 and the gas-side refrigerant communication pipe 5, and constitutes a part of the refrigerant circuit 10. In the present embodiment, the indoor unit 30 is arranged indoors.

[0051] The indoor unit 30 includes an indoor heat exchanger 31 .

[0052] The liquid side of the indoor heat exchanger 31 is connected to the liquid side refrigerant communication pipe 6, and the gas side end thereof is connected to the gas side refrigerant communication pipe 5. The indoor heat exchanger 31 is a heat exchanger that functions as an evaporator of low-pressure refrigerant in the refrigeration cycle during cooling operation and functions as a condenser of high-pressure refrigerant in the refrigeration cycle during heating operation.

[0053] The indoor heat exchanger 31 is a heat exchanger that exchanges heat between the refrigerant flowing therein and the heat medium flowing in the heat load circuit 50. The indoor heat exchanger 31 of the present embodiment is a plate-type heat exchanger in which a plurality of plate-like members are stacked so that the area for the refrigerant to flow and the area for the heat medium to flow are alternately arranged. The internal volume of the indoor heat exchanger 31 is smaller than the internal volume of the outdoor heat exchanger 40, and may be less than 2 / 3 of the internal volume of the outdoor heat exchanger 40, and preferably less than half of the internal volume of the outdoor heat exchanger 40. The internal volume of the indoor heat exchanger 31 may be, for example, more than 1L and less than 4L, or more than 1.5L and less than 2.5L. In addition, the internal volume of the indoor heat exchanger 31 refers to the volume of the space in the indoor heat exchanger 31 excluding the space for the heat medium to flow, that is, the volume of the space for the refrigerant to flow. Specifically, the internal volume of the indoor heat exchanger 31 refers to the volume of the fluid when the fluid is filled in the space for the refrigerant to flow in the indoor heat exchanger 31.

[0054] In addition, the indoor unit 30 has an indoor unit control unit 34, which controls the operation of each part constituting the indoor unit 30 and each part constituting the heat load circuit 50. The indoor unit control unit 34 has a microcomputer, which includes a processor such as a CPU (central processing unit) and a memory such as a ROM and a RAM. The indoor unit control unit 34 is connected to the outdoor unit control unit 27 via a communication line and transmits / receives control signals and the like.

[0055] The indoor unit 30 is provided with an indoor liquid side heat exchange temperature sensor 71, an indoor air side heat exchange temperature sensor 73, a heat medium temperature sensor 53, etc. The above sensors are electrically connected to the indoor unit control unit 34 and send detection signals to the indoor unit control unit 34. The indoor liquid side heat exchange temperature sensor 71 detects the temperature of the refrigerant flowing in the outlet on the side opposite to the side connected to the four-way reversing valve 22 in the indoor heat exchanger 31, that is, the liquid refrigerant side. The indoor gas side heat exchange temperature sensor 73 detects the temperature of the refrigerant flowing in the outlet on the side connected to the four-way reversing valve 22 in the indoor heat exchanger 31, that is, the gas refrigerant side. The heat medium temperature sensor 53 detects the temperature of the heat medium flowing through the outlet of the indoor heat exchanger 31.

[0056] (4) Details of the controller 7 In the air-conditioning apparatus 1 , the outdoor unit control section 27 and the indoor unit control section 34 are connected via a communication line, thereby constituting a controller 7 that controls the operation of the air-conditioning apparatus 1 .

[0057] The controller 7 mainly includes a processor such as a CPU (central processing unit) and a memory such as a ROM and a RAM, etc. In addition, various processes and controls performed by the controller 7 are realized by the various parts included in the outdoor unit control section 27 and / or the indoor unit control section 34 functioning in an integrated manner.

[0058] (5) Operation mode The operation modes are described below.

[0059] The operation modes include a cooling operation mode, a heating operation mode, and a defrosting operation mode.

[0060] The controller 7 determines whether to be in cooling operation mode or heating operation mode based on instructions received from a remote controller or the like and executes the operation. Furthermore, when a prescribed defrost start condition is satisfied during the execution of the heating operation mode, the controller 7 executes the defrost operation mode. Furthermore, when a prescribed defrost end condition is satisfied during the execution of the defrost operation mode, the controller 7 ends the defrost operation and restarts the heating operation mode. The defrost start condition is not particularly limited and can be determined, for example, based on the continuous operation time of the heating operation and the outside air temperature. Furthermore, the defrost end condition is not particularly limited and can include a prescribed time having passed since the start of the defrost operation mode, the temperature of the outdoor heat exchanger 40 reaching below a prescribed value, etc.

[0061] (5-1) Cooling operation mode In the air conditioner 1, in the cooling operation mode, the connection state of the four-way reversing valve 22 is set to a cooling operation connection state in which the discharge side of the compressor 21 is connected to the first outdoor heat exchanger 41 in the outdoor heat exchanger 40 and the suction side of the compressor 21 is connected to the gas side stop valve 28, so that the refrigerant filled in the refrigerant circuit 10 circulates mainly in the order of the compressor 21, the first outdoor heat exchanger 41, the outdoor expansion valve 24, and the indoor heat exchanger 31. In addition, in the cooling operation, the first opening and closing valve 43 and the second opening and closing valve 44 are closed, and the refrigerant does not flow in the second outdoor heat exchanger 42. As the air conditioner 1 used in an environment where the cooling load is relatively small, the cooling load can be handled even if the entire area of ​​the outdoor heat exchanger 40 is not used as a condenser. In addition, in the cooling operation, only one of the first opening and closing valve 43 and the second opening and closing valve 44 may be closed. In addition, the outdoor fan 25 is controlled to be in a driven state. The pump 52 of the heat load circuit 50 controls the flow rate based on, for example, the temperature of the heat medium detected by the heat medium temperature sensor 53 and the set temperature in the heat load unit 51 .

[0062] When the cooling operation mode starts, in the refrigerant circuit 10 , the refrigerant is sucked into the compressor 21 , compressed, and then discharged.

[0063] The compressor 21 controls its operating frequency by performing capacity control corresponding to the cooling load required in the indoor unit 30 .

[0064] The gas refrigerant discharged from the compressor 21 passes through the four-way reversing valve 22 and flows into the gas side end of the first outdoor heat exchanger 41 .

[0065] The gas refrigerant flowing into the gas side end of the first outdoor heat exchanger 41 exchanges heat with the outdoor air supplied by the outdoor fan 25 in the first outdoor heat exchanger 41 and is condensed into liquid refrigerant, and flows out from the liquid side end of the first outdoor heat exchanger 41 .

[0066] The refrigerant flowing out of the liquid side end of the first outdoor heat exchanger 41 is decompressed when passing through the outdoor expansion valve 24. In addition, the outdoor expansion valve 24 is controlled, for example, so that the superheat of the refrigerant sucked into the compressor 21 reaches a predetermined superheat target value. Here, the superheat of the refrigerant sucked into the compressor 21 can be obtained by, for example, subtracting the suction temperature (the detection temperature of the suction temperature sensor 64) from the saturation temperature corresponding to the suction pressure (the detection pressure of the suction pressure sensor 63).

[0067] The refrigerant decompressed in the outdoor expansion valve 24 passes through the liquid-side stop valve 29 and the liquid-side refrigerant communication pipe 6 , and flows into the indoor unit 30 .

[0068] The refrigerant flowing into the indoor unit 30 flows into the indoor heat exchanger 31, exchanges heat with the heat medium circulating in the heat load circuit 50 in the indoor heat exchanger 31, evaporates into gas refrigerant, and flows out from the gas side end of the indoor heat exchanger 31. The gas refrigerant flowing out from the gas side end of the indoor heat exchanger 31 flows to the gas side refrigerant communication pipe 5.

[0069] The refrigerant flowing through the gas-side refrigerant communication pipe 5 passes through the gas-side stop valve 28 , the four-way switching valve 22 , and the accumulator 49 , and is sucked into the compressor 21 again.

[0070] (5-2) Heating operation mode In the air conditioner 1, in the heating operation mode, the connection state of the four-way reversing valve 22 is set to a heating operation connection state in which the discharge side of the compressor 21 is connected to the gas side stop valve 28 and the suction side of the compressor 21 is connected to the outdoor heat exchanger 40, so that the refrigerant filled in the refrigerant circuit 10 circulates mainly in the order of the compressor 21, the indoor heat exchanger 31, the outdoor expansion valve 24, and the outdoor heat exchanger 40. Here, in the heating operation mode, in order to make the refrigerant flow through the entire outdoor heat exchanger 40, more specifically, in order to make the refrigerant flow through both the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42, both the first on-off valve 43 and the second on-off valve 43 are controlled to be in an open state. Although the air conditioner 1 is used in an environment with a relatively large heating load, the large heating load can be handled by using the entire area of ​​the outdoor heat exchanger 40 as an evaporator. In addition, the outdoor fan 25 is controlled to be in a driven state. The pump 52 of the heat load circuit 50 controls the flow rate based on, for example, the temperature of the heat medium detected by the heat medium temperature sensor 53 and the set temperature in the heat load unit 51 .

[0071] When the heating operation mode starts, in the refrigerant circuit 10 , the refrigerant is sucked into the compressor 21 , compressed, and then discharged.

[0072] The compressor 21 controls its operating frequency by performing capacity control corresponding to the heating load required in the indoor unit 30 .

[0073] The gas refrigerant discharged from the compressor 21 flows into the indoor unit 30 after passing through the four-way switching valve 22 and the gas-side refrigerant communication pipe 5 .

[0074] The refrigerant flowing into the indoor unit 30 flows into the gas side end of the indoor heat exchanger 31, exchanges heat with the heat medium circulating in the heat load circuit 50 in the indoor heat exchanger 31, and condenses into a gas-liquid two-phase refrigerant or a liquid refrigerant, and flows out from the liquid side end of the indoor heat exchanger 31. The refrigerant flowing out from the liquid side end of the indoor heat exchanger 31 flows to the liquid side refrigerant communication pipe 6.

[0075] The refrigerant flowing through the liquid-side refrigerant communication pipe 6 flows into the outdoor unit 20, passes through the liquid-side stop valve 29, and is decompressed to a low pressure in the refrigeration cycle in the outdoor expansion valve 24. In addition, the outdoor expansion valve 24 is controlled, for example, so that the superheat of the refrigerant sucked into the compressor 21 reaches a predetermined superheat target value.

[0076] The refrigerant decompressed in the outdoor expansion valve 24 flows into the liquid side ends of the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42 separately.

[0077] The refrigerant flowing in from the liquid side end of the first outdoor heat exchanger 41 exchanges heat with the outdoor air supplied by the outdoor fan 25 in the first outdoor heat exchanger 41, evaporates into a gas refrigerant, and flows out from the gas side end of the first outdoor heat exchanger 41. Similarly, the refrigerant flowing in from the liquid side end of the second outdoor heat exchanger 42 exchanges heat with the outdoor air supplied by the outdoor fan 25 in the second outdoor heat exchanger 42, evaporates into a gas refrigerant, and flows out from the gas side end of the second outdoor heat exchanger 42.

[0078] The refrigerant flowing out from the gas refrigerant side end of the first outdoor heat exchanger 41 and the refrigerant flowing out from the gas refrigerant side end of the second outdoor heat exchanger 42 merge, pass through the four-way reversing valve 22 and the storage tank 49, and are sucked into the compressor 21 again.

[0079] (5-3) Defrost operation mode In the air conditioner 1, in the defrost operation mode, the connection state of the four-way reversing valve 22 is set to a cooling operation connection state in which the discharge side of the compressor 21 is connected to both the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42, and the suction side of the compressor 21 is connected to the gas side stop valve 28, so that the refrigerant filled in the refrigerant circuit 10 circulates mainly in the order of the compressor 21, the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42, the outdoor expansion valve 24, and the indoor heat exchanger 31. In addition, in the defrost operation, unlike the cooling operation, in order to remove frost attached to the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42, the first on-off valve 43 and the second on-off valve 44 are opened, and the refrigerant is supplied to both the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42. In addition, in the defrost operation, the outdoor fan 25 is stopped. In addition, in the defrost operation, the pump 52 of the heat load circuit 50 is stopped.

[0080] When the defrosting operation mode starts, in the refrigerant circuit 10, the refrigerant is sucked into the compressor 21, compressed, and then discharged. In order to melt the frost as soon as possible, the compressor 21 is controlled to reach a predetermined maximum frequency, for example.

[0081] The gas refrigerant discharged from the compressor 21 passes through the four-way reversing valve 22 and flows into the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42, respectively. The gas refrigerant flowing into the gas side end of the first outdoor heat exchanger 41 condenses into liquid refrigerant or refrigerant in a gas-liquid two-phase state due to the melting of frost attached to the first outdoor heat exchanger 41, and flows out from the liquid side end of the first outdoor heat exchanger 41. The gas refrigerant flowing into the gas side end of the second outdoor heat exchanger 42 condenses into liquid refrigerant or refrigerant in a gas-liquid two-phase state due to the melting of frost attached to the second outdoor heat exchanger 42, and flows out from the liquid side end of the second outdoor heat exchanger 42.

[0082] The refrigerant flowing out of the liquid side end of the first outdoor heat exchanger 41 merges with the refrigerant flowing out of the liquid side end of the second outdoor heat exchanger 42, and is then decompressed when passing through the outdoor expansion valve 24. The refrigerant decompressed in the outdoor expansion valve 24 passes through the liquid side stop valve 29 and the liquid side refrigerant communication pipe 6, and flows into the indoor unit 30.

[0083] The refrigerant flowing into the indoor unit 30 flows into the indoor heat exchanger 31, exchanges heat with the heat medium of the heat load circuit 50 in the indoor heat exchanger 31, evaporates into gas refrigerant, and flows out from the gas side end of the indoor heat exchanger 31. The gas refrigerant flowing out from the gas side end of the indoor heat exchanger 31 flows to the gas side refrigerant communication pipe 5.

[0084] The refrigerant flowing through the gas-side refrigerant communication pipe 5 passes through the gas-side stop valve 28 , the four-way switching valve 22 , and the accumulator 49 , and is sucked into the compressor 21 again.

[0085] (6) Features In the air conditioner 1 of the present embodiment, the outdoor heat exchanger 40 having a larger internal volume than the indoor heat exchanger 31 is made to function as an evaporator of the refrigerant as a whole during the heating operation, so that it is easy to ensure the capacity during the heating operation. Therefore, even when the air conditioner is used in an environment with a large heating load such as a cold region, it is easy to handle the heating load. In addition, in the cooling operation, the air conditioner 1 only makes the first outdoor heat exchanger 41 of the outdoor heat exchanger 40 function as a condenser of the refrigerant, and does not make the second outdoor heat exchanger 42 function as a condenser of the refrigerant. Thus, in the cooling operation, the amount of liquid refrigerant in the outdoor heat exchanger 40 can be suppressed to be small, thereby reducing the amount of refrigerant filled in the air conditioner 1. In addition, when the air conditioner 1 is used in an environment where the cooling load is smaller than the heating load such as a cold region, it is easy to handle the cooling load even when only the first outdoor heat exchanger 41 of the outdoor heat exchanger 40 is used.

[0086] In this way, the heat load of the heating load and the cooling load can be easily handled and the amount of refrigerant filled in the air-conditioning device 1 can be suppressed to a small amount. In particular, when a flammable refrigerant is used as the refrigerant, even if the refrigerant leaks, the amount of leakage can be suppressed to a small amount. As a result, the concentration of the leaked refrigerant can be suppressed from increasing when the refrigerant leaks, thereby reducing the risk of fire.

[0087] In addition, the amount of residual refrigerant in the air-conditioning device 1 can be suppressed to a small amount, so there is no need to set up a receiver for storing liquid refrigerant at the location in the refrigerant circuit 10 where liquid refrigerant or refrigerant in a gas-liquid two-phase state flows, or even if the receiver is set up, its internal volume can be suppressed to a small size.

[0088] Furthermore, in the air conditioning apparatus 1, the outdoor heat exchanger 40 is an air heat exchanger having a larger internal volume than the indoor heat exchanger 31, and therefore, it is easy to secure a heat source even during heating operation in a cold region.

[0089] Furthermore, in the air conditioning device 1, the air flow formed by the outdoor fan 25 is supplied to the entire first outdoor heat exchanger 41 and also to the entire second outdoor heat exchanger 42. Therefore, whether the refrigerant is caused to flow through both the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42 or the refrigerant is caused to flow through only the first outdoor heat exchanger 41, the air flow generated by the outdoor fan 25 can be used to perform heat exchange in the entire first outdoor heat exchanger 41 and heat exchange in the entire second outdoor heat exchanger 42, or to perform heat exchange in the entire first outdoor heat exchanger 41.

[0090] Furthermore, in the air conditioning device 1, during the heating operation, multiple refrigerant flow paths are generated as the refrigerant flow path passing through the outdoor heat exchanger 40, such as the refrigerant flow path passing through the first outdoor heat exchanger 41 and the refrigerant flow path passing through the second outdoor heat exchanger 42. Thus, compared with the case where the outdoor heat exchanger 40 is configured as only one refrigerant flow path, the pressure loss when the refrigerant passes through can be reduced.

[0091] (7) Other Implementation Methods (7-1) Other Implementation Methods A In the above embodiment, the following air conditioning device 1 is used as an example: the outdoor heat exchanger 40 has a first outdoor heat exchanger 41 and a second outdoor heat exchanger 42, and the first outdoor heat exchanger 41 is arranged on the upwind side of the second outdoor heat exchanger 42 in the direction of the air flow formed by the outdoor fan 25.

[0092] On the other hand, the outdoor heat exchanger may be configured to be divided into a plurality of heat exchangers greater than two. Specifically, the outdoor heat exchanger may be configured to have greater than two refrigerant flow paths.

[0093] In addition, the arrangement of the plurality of heat exchangers included in the outdoor heat exchanger is not limited to being arranged side by side along the air flow direction of the outdoor fan 25 .

[0094] As an outdoor heat exchanger, for example Figure 3 The outdoor heat exchanger 140 shown in the figure may be a heat exchanger arranged in three rows along the air flow direction, with the plurality of heat transfer tube groups arranged in the longitudinal direction. In addition, the outdoor heat exchanger may include a first outdoor heat exchanger 40a, a second outdoor heat exchanger 40b, and a third outdoor heat exchanger 40c, as in the outdoor heat exchanger 140. It is preferred that the heat transfer tubes arranged in rows adjacent to each other in the air flow direction are arranged at staggered positions so as not to overlap each other when viewed from the air flow direction.

[0095] like Figure 4As shown, the outdoor heat exchanger 140 is divided into three flow paths for the refrigerant to flow during heating operation. Specifically, in the first outdoor heat exchanger 141, the refrigerant flows in from the position of the middle layer on the leeward side and flows through the heat transfer tube, then moves to the upper layer and flows through the heat transfer tube on the upper layer when turning back at the end, and turns back again to flow through the heat transfer tube on the upper layer on the upwind side. In addition, in the second outdoor heat exchanger 142, the refrigerant flows in from the position of the lower layer on the leeward side and flows through the heat transfer tube, then turns back at the end and flows through the heat transfer tube on the lower layer, and moves to the middle layer on the upwind side and flows through the heat transfer tube when turning back again. In addition, in the third outdoor heat exchanger 143, the refrigerant flows in from the position of the upper layer on the leeward side and flows through the heat transfer tube, then moves to the middle layer and flows through the heat transfer tube when turning back at the end, and moves to the lower layer on the upwind side and flows through the heat transfer tube when turning back again. Furthermore, during cooling operation, the refrigerant does not flow through the first outdoor heat exchanger 141 and the second outdoor heat exchanger 142, and the refrigerant flows only through the third outdoor heat exchanger 143. Thus, even when the refrigerant flows only through a portion of the outdoor heat exchanger 140 during cooling operation, the air flow supplied from the outdoor fan 25 can be fully utilized for heat exchange by allowing the refrigerant to flow through the third outdoor heat exchanger 143.

[0096] In the above embodiment, when using the outdoor heat exchanger 140, for example, a third outdoor heat exchanger 143 can be set between the branch point A and the branch point B, and the first outdoor heat exchanger 141 and the second outdoor heat exchanger 142 can be connected in parallel between the first opening and closing valve 43 and the second opening and closing valve 44.

[0097] (7-2) Other Implementation Methods B In the above embodiment, the case of a heat exchanger in which the refrigerant flowing through the indoor heat exchanger 31 exchanges heat with the heat medium circulating in the heat load circuit 50 is described as an example.

[0098] On the other hand, the indoor heat exchanger 31 may be an air heat exchanger. Specifically, the indoor heat exchanger 31 may perform heat exchange with air supplied from an indoor fan in order to adjust the air temperature of the space where the indoor heat exchanger 31 is arranged.

[0099] (7-3) Other Implementation Methods C In the above-described embodiment, the air conditioning apparatus 1 in which only one indoor unit 30 is provided is described as an example.

[0100] On the other hand, the air-conditioning apparatus 1 may be an air-conditioning apparatus in which a plurality of indoor units 30 are connected in parallel with respect to the outdoor unit 20 , for example.

[0101] (Note) As mentioned above, although embodiment of this disclosure is described, it should be understood that various changes in form and details can be made without departing from the spirit and scope of this disclosure described in the claims. Explanation of symbols

[0102] 1. Air conditioning unit; 7. Controller (control unit); 10, 10a, 10b, 10c refrigerant circuit; 20 outdoor units; 21 compressor; 22 four-way reversing valve (switching part); 24 outdoor expansion valve; 25 outdoor fan (air supply unit); 27 outdoor unit control unit; 30 indoor units; 31 indoor heat exchanger (first heat exchanger); 34 indoor unit control unit; 40 outdoor heat exchanger (second heat exchanger); 41 a first outdoor heat exchanger; 42 second outdoor heat exchanger; 43 first opening and closing valve; 44 second on-off valve; 49 storage tanks; 50 heat load circuit; 51 heat load unit; 52 pumps; 61 discharge pressure sensor; 62 discharge temperature sensor; 63 suction pressure sensor; 64 suction temperature sensor; 65 first outdoor heat exchange temperature sensor; 66 second outdoor heat exchange temperature sensor; 67 outside air temperature sensor; 71 Indoor liquid side heat exchange temperature sensor; 73 Indoor gas side heat exchange temperature sensor. Prior art literature Patent Literature

[0103] Patent Document 1: International Publication No. 2020 / 208776

Claims

1. An air conditioning device (1), characterized in that: include: A first heat exchanger (31); a second heat exchanger (40); as well as a switching unit (22) for switching between a first operation in which the first heat exchanger functions as a condenser of the refrigerant and the second heat exchanger functions as an evaporator of the refrigerant and a second operation in which the first heat exchanger functions as an evaporator of the refrigerant and the second heat exchanger functions as a condenser of the refrigerant, The internal volume of the first heat exchanger is smaller than the internal volume of the second heat exchanger. The internal volume of the region through which the refrigerant flows in the second heat exchanger during the second operation is smaller than the internal volume of the region through which the refrigerant flows in the second heat exchanger during the first operation.

2. The air conditioning device according to claim 1, characterized in that: The second heat exchanger is an air heat exchanger that performs heat exchange between the refrigerant flowing inside and the air flowing outside.

3. The air conditioning device according to claim 2, characterized in that: The air conditioning device further includes an air supply unit (25) capable of supplying air flow to the entire second heat exchanger.

4. The air conditioning device according to claim 3, characterized in that: During the second operation, flow paths through which the refrigerant flows through the second heat exchanger do not overlap with each other when viewed from the direction of the air flow formed by the air supply unit.

5. The air conditioning device according to any one of claims 1 to 4, characterized in that: During the first operation, the refrigerant flows through the entire internal volume of the second heat exchanger.

6. The air conditioning device according to any one of claims 1 to 4, characterized in that: During the first operation, the second heat exchanger has two or more flow paths through which the refrigerant flows.

7. The air conditioning device according to any one of claims 1 to 6, characterized in that: The second heat exchanger has a plurality of heat transfer tubes. During the second operation, the second heat exchanger has one or more heat transfer tubes through which the refrigerant does not flow.

8. The air conditioning device according to any one of claims 1 to 7, characterized in that: The internal volume of the first heat exchanger is less than or equal to 2 / 3 of the internal volume of the second heat exchanger.

9. The air conditioning device according to any one of claims 1 to 8, characterized in that: The second heat exchanger is a heat source side heat exchanger, The first heat exchanger is a utilization-side heat exchanger.

10. The air conditioning device according to any one of claims 1 to 9, characterized in that: The refrigerant is a flammable refrigerant.

11. The air conditioning device according to claim 10, characterized in that: The flammable refrigerant includes one or more selected from the group consisting of R290, R600 and R600a.

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