JP7448848B2 - air conditioner - Google Patents

Description

The present disclosure relates to an air conditioner.

In recent years, from the perspective of protecting the global environment, air conditioners that perform heating operations using air as a heat source have been introduced even in cold regions.

As an air conditioner used in such a cold region, for example, like the air conditioner described in Patent Document 1 (International Publication No. 2020/208776), the heating capacity is adjusted according to the indoor heating load. something is proposed.

In order to ensure sufficient capacity during heating operation even when the outside air temperature is low, such as in a cold region, an air conditioner is sometimes used in which the outdoor heat exchanger that functions as an evaporator has a large capacity. When performing cooling operation using this air conditioner, the outdoor heat exchanger will function as a refrigerant condenser, but a large amount of liquid refrigerant will be present in the outdoor heat exchanger, which has a large capacity. , the amount of refrigerant charged into the refrigerant circuit tends to increase.

The air conditioner according to the first aspect includes a first heat exchanger, a second heat exchanger, and a switching section. The switching unit switches between the first operation and the second operation. In the first operation, the first heat exchanger functions as a refrigerant condenser, and the second heat exchanger functions as a refrigerant evaporator. In the second operation, the first heat exchanger functions as a refrigerant evaporator, and the second heat exchanger functions as a refrigerant condenser. 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.

In this air conditioner, in the first operation, the second heat exchanger, which has a larger internal volume than the first heat exchanger, functions as a refrigerant evaporator, so that the capacity during the first operation can be easily ensured. Further, in the air conditioner, during the second operation in which the second heat exchanger functions as a refrigerant condenser, the internal volume of the region through which the refrigerant flows in the second heat exchanger is the same as that in the second heat exchanger during the first operation. It is small compared to the internal volume of the area through which the refrigerant flows. Therefore, the amount of liquid refrigerant held in the second heat exchanger during the second operation can be kept small. Therefore, it becomes possible to reduce the amount of refrigerant filled into the air conditioner.

The air conditioner according to the second aspect is the air conditioner according to the first aspect, and the second heat exchanger is an air heat exchanger that performs heat exchange between the refrigerant flowing inside and the air flowing outside. It is.

In this air conditioner, even if the refrigerant flowing through the second heat exchanger that functions as an evaporator during the first operation exchanges heat with low-temperature outside air in a cold region, the first heat exchanger It has a larger internal volume than an exchanger, so it is easier to secure capacity.

The air conditioner according to the third aspect is the air conditioner according to the second aspect, and further includes an air blower. The blower is capable of providing air flow throughout the second heat exchanger.

In this air conditioner, since the air flow is supplied to the entire second heat exchanger, it is easy to ensure the amount of heat exchange.

The air conditioner according to the fourth aspect is the air conditioner according to the third aspect, in which during the second operation, the flow path through which the refrigerant flows through the second heat exchanger is viewed from the direction of the air flow formed by the blowing section. do not overlap each other.

In this air conditioner, even if the internal volume of the refrigerant passage area of the second heat exchanger during the second operation is smaller than that during the first operation, it is possible to efficiently exchange heat.

The air conditioner according to the fifth aspect is the air conditioner according to any one of the first to fourth aspects, and during the first operation, the refrigerant flows through the entire internal volume of the second heat exchanger.

In this air conditioner, capacity is easily ensured in the second heat exchanger that functions as an evaporator when performing the first operation.

The air conditioner according to the sixth aspect is the air conditioner according to any one of the first to fourth aspects, and in the first operation, the second heat exchanger has two or more channels through which the refrigerant flows. are doing.

This air conditioner can reduce pressure loss in the second heat exchanger that functions as an evaporator during the first operation.

The air conditioner according to the seventh aspect is the air conditioner according to any one of the first to sixth aspects, and the second heat exchanger has a plurality of heat exchanger tubes. During the second operation, the second heat exchanger has one or more heat transfer tubes through which refrigerant does not flow.

This air conditioner can reduce the amount of liquid refrigerant held in the second heat exchanger during the second operation in which the second heat exchanger functions as a refrigerant condenser.

The air conditioner according to the eighth aspect is the air conditioner according to any one of the first to seventh aspects, wherein the internal volume of the first heat exchanger is 2/3 of the internal volume of the second heat exchanger. It is as follows.

In this air conditioner, even when the internal volume of the second heat exchanger is large, the amount of refrigerant to be filled can be kept small.

The air conditioner according to the ninth aspect is the air conditioner according to any of the first to eighth aspects, and the second heat exchanger is a heat source side heat exchanger. The first heat exchanger is a user-side heat exchanger.

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

The air conditioner according to the tenth aspect is the air conditioner according to any one of the first to ninth aspects, and the refrigerant is a combustible refrigerant.

In this air conditioner, even when using a combustible refrigerant, the amount of refrigerant to be charged can be reduced.

The air conditioner according to the eleventh aspect is the air conditioner according to the tenth aspect, in which the combustible refrigerant includes one or more selected from the group consisting of R290, R600, and R600a. included.

This air conditioner can reduce the risk of ignition even when using a refrigerant that easily burns.

FIG. 2 is a schematic configuration diagram of a refrigerant circuit. It is a schematic control block block diagram of an air conditioner. FIG. 3 is a schematic external configuration diagram of an outdoor heat exchanger according to another embodiment A. 7 is a diagram showing a refrigerant flow during heating operation of an outdoor heat exchanger according to another embodiment A. FIG.

The air conditioner 1 will be described below with reference to FIG. 1, which is a schematic diagram of a refrigerant circuit, and FIG. 2, which is a schematic control block diagram.

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

The air conditioner 1 mainly includes an outdoor unit 20, an indoor unit 30, a liquid side refrigerant connection pipe 6 and a gas side refrigerant connection pipe 5 that connect the outdoor unit 20 and the indoor unit 30, a heat load circuit 50, and an input circuit. It has a remote controller (not shown) as a device and an output device, and a controller 7 that controls the operation of the air conditioner 1.

In the air conditioner 1, a refrigeration cycle is performed in which the refrigerant sealed in the refrigerant circuit 10 is compressed, cooled or condensed, depressurized, heated or evaporated, and then compressed again. In this embodiment, the refrigerant circuit 10 is filled with refrigerant for performing a vapor compression type refrigeration cycle. The refrigerant is a combustible refrigerant. Examples of flammable refrigerants include highly flammable refrigerants of classes A3 and B3, flammable refrigerants of classes A2 and B2, and slightly flammable refrigerants of classes A2L and B2L in the ASHRAE Safety Group. More specifically, the refrigerant may be one or more selected from the group consisting of R290, R600, and R600a. Note that in this embodiment, the refrigerant circuit 10 is filled with a refrigerant having a higher specific gravity than air. Further, the refrigerant circuit 10 is filled with refrigerating machine oil together with the mixed refrigerant.

(1) Outdoor unit 20
The outdoor unit 20 is connected to the indoor unit 30 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. The outdoor unit 20 mainly includes a compressor 21, a four-way switching valve 22, an outdoor heat exchanger 40, a first on-off valve 43, a second on-off valve 44, an outdoor expansion valve 24, and an outdoor fan 25. , an accumulator 49, a liquid side closing valve 29, and a gas side closing valve 28. In this embodiment, the outdoor unit 20 is placed outdoors.

The compressor 21 is a device that compresses low-pressure refrigerant in the refrigeration cycle to high pressure. Here, as the compressor 21, a hermetic structure compressor in which a positive displacement compression element (not shown), such as a rotary type or a scroll type, is rotationally driven 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.

The four-way switching valve 22 switches between a cooling operation connection state and a heating operation connection state by switching the connection state. In the cooling operation connected state, the four-way switching valve 22 connects the discharge side of the compressor 21 and the outdoor heat exchanger 40, and connects the suction side of the compressor 21 to the gas side closing valve 28. More specifically, in the cooling operation connected state, the discharge side of the compressor 21 is connected to a branch point A, which will be described later. Furthermore, in the heating operation connected state, the four-way switching valve 22 connects the discharge side of the compressor 21 to the gas side closing valve 28 and connects the suction side of the compressor 21 to the outdoor heat exchanger 40 . More specifically, in the heating operation connected state, the suction side of the compressor 21 is connected to a branch point A, which will be described later.

The accumulator 49 is provided between the four-way switching valve 22 and the suction side of the compressor 21. This prevents the compressor 21 from sucking in liquid refrigerant.

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

In this embodiment, during the cooling operation, the first outdoor heat exchanger 41 functions as a high-pressure refrigerant condenser in the refrigeration cycle, and during the heating operation, the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42 function as a condenser. Both serve as low-pressure refrigerant evaporators in the refrigeration cycle. The first outdoor heat exchanger 41 is provided between the four-way switching valve 22 and the outdoor expansion valve 24. A branch point A is provided between the four-way switching valve 22 and the gas refrigerant side end of the first outdoor heat exchanger 41 to branch the refrigerant flow path. A branch point B is provided between the liquid refrigerant side end of the first outdoor heat exchanger 41 and the outdoor expansion valve 24 to branch the refrigerant flow path. In the second outdoor heat exchanger 42, the gas refrigerant side end of the second outdoor heat exchanger 42 is connected to the branch point A, and the liquid refrigerant side end of the second outdoor heat exchanger 42 is connected to the branch point B. By being connected, the first outdoor heat exchanger 41 and the first outdoor heat exchanger 41 are connected in parallel. A first on-off valve 43 that can be opened and closed 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 that can be opened and closed is provided between the liquid refrigerant side of the second outdoor heat exchanger 42 and the branch point B.

The outdoor fan 25 draws outdoor air into the outdoor unit 20, exchanges heat with a refrigerant in the outdoor heat exchanger 40, and then generates an air flow for discharging the air to the outside. The outdoor fan 25 is rotationally driven by an outdoor fan motor. In this embodiment, the outdoor fan 25 includes a plurality of fans. The outdoor fan 25 including the plurality of fans supplies an air flow formed by driving 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 also to the entire second outdoor heat exchanger 42 . In this embodiment, the first outdoor heat exchanger 41 is arranged on the windward side of the second outdoor heat exchanger 42 in the air flow direction formed by the outdoor fan 25.

The outdoor expansion valve 24 is provided between the liquid side end of the outdoor heat exchanger 40 and the liquid side closing valve 29. The outdoor expansion valve 24 may be a mechanical expansion valve used with a capillary tube or a temperature-sensitive tube, but is preferably an electric expansion valve whose opening degree can be controlled.

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

The gas side shutoff valve 28 is a manual valve disposed at a connection portion between the outdoor unit 20 and the gas side refrigerant communication pipe 5.

The outdoor unit 20 has an outdoor unit control section 27 that controls the operation of each part that constitutes the outdoor unit 20. The outdoor unit control section 27 includes a microcomputer including a processor such as a CPU (Central Processing Unit), and a memory such as a ROM and a RAM. The outdoor unit control section 27 is connected to the indoor unit control section 34 of each indoor unit 30 via a communication line, and sends and receives control signals and the like.

The outdoor unit 20 includes a discharge pressure sensor 61, a discharge temperature sensor 62, a suction pressure sensor 63, a suction temperature sensor 64, a first outdoor heat exchanger temperature sensor 65, a second outdoor heat exchanger temperature sensor 66, an outside air temperature sensor 67, etc. It is provided. Each of these sensors is electrically connected to the outdoor unit control section 27 and transmits a detection signal to the outdoor unit control section 27. The discharge pressure sensor 61 detects the pressure of refrigerant flowing through a discharge pipe connecting the discharge side of the compressor 21 and one of the connection ports of the four-way switching valve 22. The discharge temperature sensor 62 detects the temperature of the refrigerant flowing through the discharge pipe. The suction pressure sensor 63 detects the pressure of refrigerant flowing through the suction pipe connecting the suction side of the compressor 21 and one of the connection ports of the four-way switching valve 22. The suction temperature sensor 64 detects the temperature of the refrigerant flowing through the suction pipe. The first outdoor heat exchanger 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 branch point B. The second outdoor heat exchanger 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 outdoor air temperature before passing through the outdoor heat exchanger 40.

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

The heat load circuit 50 includes a heat load section 51 and a pump 52.

The heat load section 51 is a section that processes the cooling load during the cooling operation, and a section that processes the heating load during the heating operation. Examples of the heat load section 51 include a floor heating panel during heating operation, a coil portion of a fan coil unit for supplying cold air using a blower fan during cooling operation, and the like.

The pump 52 circulates the heat medium in the heat load circuit 50, and is capable of controlling the flow rate.

During cooling operation, the heat load circuit 50 supplies the heat medium cooled by exchanging heat with the refrigerant in the indoor heat exchanger 31 to the heat load section 51 . The heat medium warmed by processing the cooling load in the heat load section 51 is supplied to the indoor heat exchanger 31 again.

During heating operation, the heat load circuit 50 supplies the heat medium heated by exchanging heat with the refrigerant in the indoor heat exchanger 31 to the heat load section 51 . The heat medium cooled by processing the heating load in the heat load section 51 is supplied to the indoor heat exchanger 31 again.

(3) Indoor unit 30
The indoor unit 30 is provided near the air-conditioned space. The indoor unit 30 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 this embodiment, the indoor unit 30 is placed indoors.

The indoor unit 30 has an indoor heat exchanger 31.

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

The indoor heat exchanger 31 is a heat exchanger that exchanges heat between the refrigerant flowing therein and the heat medium flowing through the thermal load circuit 50 . The indoor heat exchanger 31 of this embodiment is a plate heat exchanger in which a plurality of plate-like members are stacked, and regions where a refrigerant flows and regions where a heat medium flows are arranged alternately. The internal volume of the indoor heat exchanger 31 is smaller than the internal volume of the outdoor heat exchanger 40, and may be 2/3 or less of the internal volume of the outdoor heat exchanger 40, and may be half of the internal volume of the outdoor heat exchanger 40. It is preferable that it is below. The internal volume of the indoor heat exchanger 31 may be, for example, 1 L or more and 4 L or less, or 1.5 L or more and 2.5 L or less. Note that the internal volume of the indoor heat exchanger 31 refers to the space in the indoor heat exchanger 31 excluding the space through which the heat medium flows, and refers to the volume of the space through which the refrigerant flows. Specifically, the internal volume of the indoor heat exchanger 31 refers to the volume of fluid when the space in the indoor heat exchanger 31 through which the refrigerant flows is filled with fluid.

In addition, the indoor unit 30 has an indoor unit control section 34 that controls the operation of each section configuring the indoor unit 30 and each section configuring the heat load circuit 50. The indoor unit control section 34 includes a microcomputer including a processor such as a CPU (Central Processing Unit), and a memory such as a ROM and a RAM. The indoor unit control section 34 is connected to the outdoor unit control section 27 via a communication line, and sends and receives control signals and the like.

The indoor unit 30 is provided with an indoor liquid side heat exchanger temperature sensor 71, an indoor gas side heat exchanger temperature sensor 73, a heat medium temperature sensor 53, and the like. Each of these sensors is electrically connected to the indoor unit control section 34 and transmits a detection signal to the indoor unit control section 34. The indoor liquid side heat exchanger temperature sensor 71 detects the temperature of the refrigerant flowing through the outlet of the liquid refrigerant side of the indoor heat exchanger 31, which is the side opposite to the side to which the four-way switching valve 22 is connected. The indoor gas side heat exchanger temperature sensor 73 detects the temperature of the refrigerant flowing through the outlet of the gas refrigerant side of the indoor heat exchanger 31, which is the side to which the four-way switching valve 22 is connected. The heat medium temperature sensor 53 detects the temperature of the heat medium flowing through the outlet of the indoor heat exchanger 31.

(4) Details of the controller 7 In the air conditioner 1, the controller 7 that controls the operation of the air conditioner 1 is configured by connecting the outdoor unit control section 27 and the indoor unit control section 34 via a communication line. ing.

The controller 7 mainly includes a processor such as a CPU (Central Processing Unit), and a memory such as a ROM or RAM. Note that various processes and controls by the controller 7 are realized by each part included in the outdoor unit control section 27 and/or the indoor unit control section 34 functioning in an integrated manner.

(5) Driving mode The driving mode will be explained below.

The operation modes include a cooling operation mode, a heating operation mode, and a defrost operation mode.

The controller 7 determines whether the mode is a cooling operation mode or a heating operation mode based on an instruction received from a remote controller or the like, and executes the mode. Further, the controller 7 executes the defrost operation mode when a predetermined defrost start condition is satisfied during the execution of the heating operation mode. Then, when a predetermined defrost termination condition is satisfied during execution of the defrost operation mode, the controller 7 terminates the defrost operation and restarts the heating operation mode. The defrost start condition is not particularly limited, and can be determined based on, for example, the continuous operation time of the heating operation or the outside air temperature. Further, the defrost termination condition is not particularly limited, and includes, for example, that a predetermined time has passed since the defrost operation mode was started, or that the temperature of the outdoor heat exchanger 40 has fallen below a predetermined value.

(5-1) Cooling Operation Mode In the air conditioner 1, in the cooling operation mode, the connection state of the four-way switching valve 22 is changed between the discharge side of the compressor 21 and the first outdoor heat exchanger 41 of the outdoor heat exchangers 40. A cooling operation connection state is established in which the suction side of the compressor 21 is connected to the gas side closing valve 28 while the suction side of the compressor 21 is connected to the 41, the outdoor expansion valve 24, and the indoor heat exchanger 31 in this order. Note that during cooling operation, the first on-off valve 43 and the second on-off valve 44 are closed, and no refrigerant flows into the second outdoor heat exchanger 42. As the air conditioner 1 used in an environment where the cooling load is relatively small, it is possible to handle the cooling load without using the entire area of the outdoor heat exchanger 40 as a condenser. Note that during cooling operation, only one of the first on-off valve 43 and the second on-off valve 44 may be closed. Moreover, the outdoor fan 25 is controlled to be in a driving state. The flow rate of the pump 52 of the heat load circuit 50 is controlled 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 section 51 .

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

The operating frequency of the compressor 21 is controlled by performing capacity control according to the cooling load required by the indoor unit 30.

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

The gas refrigerant that has flowed 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, condenses, and becomes a liquid refrigerant. and flows out from the liquid side end of the first outdoor heat exchanger 41.

The refrigerant flowing out from the liquid side end of the first outdoor heat exchanger 41 is depressurized when passing through the outdoor expansion valve 24 . Note that the outdoor expansion valve 24 is controlled, for example, so that the degree of superheat of the refrigerant sucked into the compressor 21 becomes a predetermined target value of the degree of superheat. Here, the degree of superheat of the refrigerant sucked into the compressor 21 is determined, for example, by subtracting the saturation temperature corresponding to the suction pressure (the pressure detected by the suction pressure sensor 63) from the suction temperature (the temperature detected by the suction temperature sensor 64). be able to.

The refrigerant whose pressure has been reduced by the outdoor expansion valve 24 flows into the indoor unit 30 via the liquid side closing valve 29 and the liquid side refrigerant communication pipe 6.

The refrigerant that has flowed into the indoor unit 30 flows into the indoor heat exchanger 31, where it exchanges heat with the heat medium circulating in the thermal load circuit 50, evaporates, and becomes a gas refrigerant that generates indoor heat. It flows out from the gas side end of the exchanger 31. The gas refrigerant flowing out from the gas side end of the indoor heat exchanger 31 flows into the gas side refrigerant communication pipe 5.

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

(5-2) Heating operation mode In the air conditioner 1, in the heating operation mode, the four-way switching valve 22 is connected to the discharge side of the compressor 21 and the gas side closing valve 28, while the suction of the compressor 21 is connected. A heating operation connection state is established in which the side and the outdoor heat exchanger 40 are connected, and the refrigerant filled in the refrigerant circuit 10 is mainly transferred to the compressor 21, the indoor heat exchanger 31, the outdoor expansion valve 24, and the outdoor heat exchanger 40. Circulate in this order. Here, in the heating operation mode, in order to flow the refrigerant throughout the outdoor heat exchanger 40, more specifically, to flow the refrigerant through both the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42. At this time, both the first on-off valve 43 and the second on-off valve 44 are controlled to be in the open state. Although the air conditioner 1 is used in an environment with a relatively large heating load, by using the entire area of the outdoor heat exchanger 40 as an evaporator, it becomes possible to handle the large heating load. Moreover, the outdoor fan 25 is controlled to be in a driving state. The flow rate of the pump 52 of the heat load circuit 50 is controlled 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 section 51.

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

The capacity of the compressor 21 is controlled according to the heating load required by the indoor unit 30, and the operating frequency is controlled.

The gas refrigerant discharged from the compressor 21 flows through the four-way switching valve 22 and the gas-side refrigerant communication pipe 5, and then flows into the indoor unit 30.

The refrigerant that has flowed into the indoor unit 30 flows into the gas side end of the indoor heat exchanger 31, where it exchanges heat with the heat medium circulating through the heat load circuit 50 and condenses, forming a gas-liquid two. The refrigerant becomes a 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 into the liquid side refrigerant communication pipe 6.

The refrigerant flowing through the liquid-side refrigerant communication pipe 6 flows into the outdoor unit 20, passes through the liquid-side closing valve 29, and is depressurized at the outdoor expansion valve 24 until it reaches a low pressure in the refrigeration cycle. Note that the outdoor expansion valve 24 is controlled, for example, so that the degree of superheat of the refrigerant sucked into the compressor 21 becomes a predetermined target value of the degree of superheat.

The refrigerant whose pressure has been reduced by 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, respectively.

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

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, and then the four-way switching valve 22 and the accumulator 49 After that, it is sucked into the compressor 21 again.

(5-3) Defrost operation mode In the air conditioner 1, in the defrost operation mode, the four-way switching valve 22 is connected to the discharge side of the compressor 21, the first outdoor heat exchanger 41, and the second outdoor heat exchanger 42. A cooling operation connection state is established in which the suction side of the compressor 21 and the gas side closing valve 28 are connected while both are connected to the compressor 21 and the gas side shutoff valve 28. The heat exchanger 41, the second outdoor heat exchanger 42, the outdoor expansion valve 24, and the indoor heat exchanger 31 are circulated in this order. Note that during the defrost operation, unlike during the cooling operation, the first on-off valve 43 and the second on-off valve 44 are operated in order to remove frost attached to the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42. The refrigerant is supplied to both the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42 . Furthermore, during the defrost operation, the outdoor fan 25 is stopped. Further, during the defrost operation, the pump 52 of the heat load circuit 50 is stopped.

When the defrost operation mode is started, refrigerant is sucked into the compressor 21 in the refrigerant circuit 10, compressed, and then discharged. The compressor 21 is controlled to have a predetermined maximum frequency, for example, in order to melt the frost early.

The gas refrigerant discharged from the compressor 21 passes through the four-way switching valve 22 and flows into the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42, respectively. The gas refrigerant that has flowed into the gas side end of the first outdoor heat exchanger 41 is condensed by melting the frost attached to the first outdoor heat exchanger 41, and becomes a liquid refrigerant or a gas-liquid two-layer refrigerant. It flows out from the liquid side end of the first outdoor heat exchanger 41. The gas refrigerant that has flowed into the gas side end of the second outdoor heat exchanger 42 is condensed by melting the frost attached to the second outdoor heat exchanger 42, and becomes a liquid refrigerant or a gas-liquid two-layer refrigerant. It flows out from the liquid side end of the second outdoor heat exchanger 42.

The refrigerant flowing out from the liquid side end of the first outdoor heat exchanger 41 and the refrigerant flowing out from the liquid side end of the second outdoor heat exchanger 42 are depressurized when passing through the outdoor expansion valve 24 after merging. The refrigerant whose pressure has been reduced by the outdoor expansion valve 24 flows into the indoor unit 30 via the liquid side closing valve 29 and the liquid side refrigerant communication pipe 6.

The refrigerant that has flowed into the indoor unit 30 flows into the indoor heat exchanger 31, where it exchanges heat with the heat medium of the thermal load circuit 50, evaporates, and becomes a gas refrigerant that is transferred to the indoor heat exchanger. It flows out from the gas side end of 31. The gas refrigerant flowing out from the gas side end of the indoor heat exchanger 31 flows into the gas side refrigerant communication pipe 5.

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

(6) Features In the air conditioner 1 of the present embodiment, the entire outdoor heat exchanger 40, which has a larger internal volume than the indoor heat exchanger 31, functions as a refrigerant evaporator during heating operation, so the capacity during heating operation is is easy to secure. Therefore, even when the device is used in an environment with a large heating load, such as in a cold region, the heating load can be easily handled. Further, during cooling operation, the air conditioner 1 causes only the first outdoor heat exchanger 41 of the outdoor heat exchangers 40 to function as a refrigerant condenser, and the second outdoor heat exchanger 42 functions as a refrigerant condenser. Don't make it work. Thereby, during cooling operation, the amount of liquid refrigerant contained in the outdoor heat exchanger 40 can be kept small, and the amount of refrigerant filled into the air conditioner 1 can be reduced. Furthermore, when the air conditioner 1 is used in an environment where the cooling load is smaller than the heating load, such as in a cold region, even if only the first outdoor heat exchanger 41 of the outdoor heat exchangers 40 is used. , it is easy to handle the cooling load.

In this way, the amount of refrigerant charged into the air conditioner 1 can be kept small while making it easier to handle the heat loads of the heating load and the cooling load. In particular, when a combustible refrigerant is used as the refrigerant, even if refrigerant leakage occurs, the amount of leakage can be kept small. Thereby, it is possible to suppress the concentration of the leaked refrigerant from increasing when the refrigerant leaks, and it is possible to reduce the risk of ignition.

Since the amount of surplus refrigerant in the air conditioner 1 can be kept small, it is not necessary to provide a receiver for storing liquid refrigerant in the refrigerant circuit 10 where the liquid refrigerant or gas-liquid two-phase refrigerant flows. It is possible to eliminate the receiver, or even if the receiver is provided, the internal volume can be kept small.

Further, in the air conditioner 1, the outdoor heat exchanger 40 is an air heat exchanger having a larger internal volume than the indoor heat exchanger 31, so it is easy to secure a heat source even during heating operation in a cold region.

Further, in the air conditioner 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 allowed to flow through both the first outdoor heat exchanger 41 and the second outdoor heat exchanger 42 or only the first outdoor heat exchanger 41, in either case, the outdoor fan 25 The air flow is 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. It becomes possible to perform heat exchange.

In the air conditioner 1, during heating operation, the refrigerant flow path that passes through the outdoor heat exchanger 40 includes a refrigerant flow path that passes through the first outdoor heat exchanger 41 and a second outdoor heat exchanger 42. Multiple flow paths with refrigerant flow paths result. This makes it possible to reduce pressure loss when the refrigerant passes, compared to a case where the outdoor heat exchanger 40 is configured to have one refrigerant flow path.

(7) Other embodiments (7-1) Other embodiments A
In the embodiment described above, the outdoor heat exchanger 40 includes a first outdoor heat exchanger 41 and a second outdoor heat exchanger 42, and the first outdoor heat exchanger 41 has an air flow formed by the outdoor fan 25. The explanation has been given by taking as an example the air conditioner 1 disposed on the windward side of the second outdoor heat exchanger 42 in the direction.

On the other hand, the outdoor heat exchanger may be divided into more than two heat exchangers. Specifically, the outdoor heat exchanger may be configured to have more than two refrigerant flow paths.

Further, the arrangement of the plurality of heat exchangers included in the outdoor heat exchanger is not limited to the arrangement arranged in a line in the air flow direction of the outdoor fan 25.

Examples of the outdoor heat exchanger include an outdoor heat exchanger 140 shown in FIG. 3, in which a plurality of heat transfer tube groups arranged vertically are arranged in three rows in the air flow direction. It may be. Further, 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, like this outdoor heat exchanger 140. . Here, it is preferable that the heat exchanger tubes arranged in rows adjacent to each other in the air flow direction are shifted in position so as not to overlap each other when viewed from the air flow direction.

For example, during heating operation, the outdoor heat exchanger 140 is divided into three flow paths through which the refrigerant flows, as shown in FIG. 4 . Specifically, in the first outdoor heat exchanger 141, after flowing from the middle stage position on the leeward side and flowing through the heat exchanger tubes, when turning back at the end, it moves to the upper stage and flows through the upper stage heat exchanger tubes, and then turns back and flows through the heat exchanger tubes. and flows through the upper heat transfer tube on the windward side. In the second outdoor heat exchanger 142, the water flows from the lower stage on the leeward side, flows through the heat exchanger tubes, turns back at the end, flows through the lower heat exchanger tubes, and then moves to the middle stage on the windward side when turning back. Flows through heat transfer tubes. In addition, in the third outdoor heat exchanger 143, after flowing from the upper stage on the leeward side and flowing through the heat exchanger tubes, when turning back at the end, it moves to the middle stage and flowing through the heat exchanger tubes, and when turning back again, it flows through the lower stage on the windward side. and flows through the heat transfer tube. During the cooling operation, the refrigerant does not flow through the first outdoor heat exchanger 141 and the second outdoor heat exchanger 142, but flows only through the third outdoor heat exchanger 143. As a result, even if the refrigerant flows only in a part of the outdoor heat exchanger 140 during cooling operation, by flowing the refrigerant to the third outdoor heat exchanger 143, the entire air flow supplied from the outdoor fan 25 is heated. It can be used for exchange.

When using the outdoor heat exchanger 140 in the above embodiment, for example, the third outdoor heat exchanger 143 is provided between the branch point A and the branch point B, and the first on-off valve 43 and the second on-off valve 44 are connected to each other. In between, the first outdoor heat exchanger 141 and the second outdoor heat exchanger 142 can be connected in parallel.

(7-2) Other embodiment B
In the above embodiment, the case where the refrigerant flowing through the indoor heat exchanger 31 exchanges heat with the heat medium circulating through the thermal load circuit 50 has been described as an example.

On the other hand, the indoor heat exchanger 31 may be an air heat exchanger. Specifically, the indoor heat exchanger 31 may exchange heat with air supplied from an indoor fan in order to adjust the air temperature of the space in which the indoor heat exchanger 31 is placed. .

(7-3) Other embodiment C
In the above embodiment, the air conditioner 1 in which only one indoor unit 30 is provided has been described as an example.

On the other hand, the air conditioner 1 may be, for example, one in which a plurality of indoor units 30 are connected to the outdoor unit 20 in parallel.

(Additional note)
Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as described in the claims. .

1 Air conditioner 7 Controller (control unit)
10, 10a, 10b, 10c refrigerant circuit 20 outdoor unit 21 compressor 22 four-way switching valve (switching part)
24 Outdoor expansion valve 25 Outdoor fan (ventilation section)
27 Outdoor unit control section 30 Indoor unit 31 Indoor heat exchanger 34 Indoor unit control section 40 Outdoor heat exchanger 41 First outdoor heat exchanger 42 Second outdoor heat exchanger 43 First on-off valve 44 Second on-off valve 49 Accumulator 50 Heat load circuit 51 Heat load section 52 Pump 61 Discharge pressure sensor 62 Discharge temperature sensor 63 Suction pressure sensor 64 Suction temperature sensor 65 First outdoor heat exchanger temperature sensor 66 Second outdoor heat exchanger temperature sensor 67 Outside air temperature sensor 71 Indoor liquid side heat Exchanger temperature sensor 73 Indoor gas side heat exchanger temperature sensor

International Publication No. 2020/208776

Claims (11)

a first heat exchanger (31);
a second heat exchanger (40);
a first operation in which the first heat exchanger functions as a refrigerant condenser and the second heat exchanger functions as a refrigerant evaporator; and a first operation in which the first heat exchanger functions as a refrigerant evaporator; a switching unit (22) for switching between a second operation in which the second heat exchanger functions as a refrigerant condenser;
Equipped with
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.
Air conditioner (1). The second heat exchanger is an air heat exchanger that performs heat exchange between the refrigerant flowing inside and the air flowing outside.
The air conditioner according to claim 1. further comprising an air blower (25) capable of supplying air flow to the entire second heat exchanger;
The air conditioner according to claim 2. During the second operation, the channels through which the refrigerant flows through the second heat exchanger do not overlap each other when viewed from the direction of the air flow formed by the blowing section.
The air conditioner according to claim 3. During the first operation, the refrigerant flows through the entire internal volume of the second heat exchanger.
The air conditioner according to any one of claims 1 to 4. During the first operation, the second heat exchanger has two or more channels through which the refrigerant flows.
The air conditioner according to any one of claims 1 to 4. The second heat exchanger has a plurality of heat exchanger tubes,
During the second operation, the second heat exchanger has one or more heat transfer tubes through which the refrigerant does not flow.
The air conditioner according to any one of claims 1 to 4. The internal volume of the first heat exchanger is 2/3 or less of the internal volume of the second heat exchanger,
The air conditioner according to any one of claims 1 to 4. The second heat exchanger is a heat source side heat exchanger,
The first heat exchanger is a user-side heat exchanger,
The air conditioner according to any one of claims 1 to 4. The refrigerant is a combustible refrigerant,
The air conditioner according to any one of claims 1 to 4. The combustible refrigerant includes one or more selected from the group consisting of R290, R600, and R600a.
The air conditioner according to claim 10.