air conditioning equipment

Abstract

This air conditioning device is provided with a control device which controls the opening degrees of a first throttle device and a second throttle device on the basis of a temperature measured by a first temperature measurement unit during a defrost operation, a pressure measured by a first pressure measurement unit, a temperature measured by a second temperature measurement unit, and a pressure measured by a second pressure measurement unit.

Description

[Technical Field]

[0001] The present disclosure relates to an air conditioner capable of defrosting operation. [Background technology]

[0002] In a defrosting operation to melt frost formed on an outdoor heat exchanger, there is a technique for controlling the flow rate of refrigerant flowing through a plurality of outdoor heat exchangers to shorten the defrosting time and thereby shorten the heating stop time (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-109463 Summary of the Invention [Problem to be solved by the invention]

[0004] During defrosting operation, to avoid reducing comfort by supplying cool air to the room, defrosting is performed by stopping the airflow from the indoor unit. However, stopping the airflow from the indoor unit significantly reduces the evaporation capacity of the indoor heat exchanger installed in the indoor unit. This prevents the refrigerant that condenses through heat exchange with frost in the outdoor unit from evaporating, resulting in excessive liquid refrigerant being supplied to the compressor, which can cause malfunction. To solve this problem, methods include reducing the compressor frequency to limit the amount of circulation and increasing the size of the refrigerant tank to store the liquid refrigerant, but these methods result in reduced defrosting performance and reduced space in the outdoor unit.

[0005] The present disclosure has been made in consideration of the above-described circumstances, and aims to provide an air conditioner that can improve both defrosting performance and space efficiency of the outdoor unit. [Means for solving the problem]

[0006] The air conditioner according to the present disclosure includes a main circuit in which a compressor, an outdoor heat exchanger, a first throttling device, an indoor heat exchanger, and a refrigerant tank are connected, and in which refrigerant circulates through the compressor, the outdoor heat exchanger, the first throttling device, and the indoor heat exchanger in this order during defrosting operation; an inter-refrigerant heat exchanger provided between the outdoor heat exchanger and the first throttling device, and performing heat exchange between a high-pressure refrigerant flowing out of the outdoor heat exchanger during defrosting operation and a low-pressure refrigerant obtained by reducing the pressure of the high-pressure refrigerant; and a heat exchanger between the first throttling device and the inter-refrigerant heat exchanger. Cold Branched from the first branch in the medium pipe Cold and a second throttling device provided in the refrigerant piping and reducing the pressure of the high-pressure refrigerant flowing through the branched refrigerant piping to the low-pressure refrigerant, the refrigerant-to-refrigerant heat exchanger comprising: a high-temperature side flow passage inlet into which the high-pressure refrigerant flowing out of the outdoor heat exchanger flows; a high-temperature side flow passage outlet connected to the first throttling device and the second throttling device and from which the high-pressure refrigerant flowing into the high-temperature side flow passage inlet flows out; a low-temperature side flow passage inlet connected to the second throttling device and into which the low-pressure refrigerant flowing out of the second throttling device flows in; and a low-temperature side flow passage outlet connected to a second branch provided in the refrigerant piping connecting the indoor heat exchanger and the refrigerant tank during the defrosting operation and from which the low-pressure refrigerant flowing into the low-temperature side flow passage inlet flows out; a first temperature measurement unit that measures the temperature of the refrigerant flowing through the first refrigerant pipe; a first pressure measurement unit that is provided in the first refrigerant pipe and that measures the pressure of the refrigerant flowing through the first refrigerant pipe; a second temperature measurement unit that is provided in a second refrigerant pipe between the low-temperature side flow path outlet and the second branch and that measures the temperature of the refrigerant flowing through the second refrigerant pipe; a second pressure measurement unit that is provided in the second refrigerant pipe and that measures the pressure of the refrigerant flowing through the second refrigerant pipe; and a control device that controls opening degrees of the first and second throttle devices based on the temperature measured by the first temperature measurement unit, the pressure measured by the first pressure measurement unit, the temperature measured by the second temperature measurement unit, and the pressure measured by the second pressure measurement unit during the defrost operation. When the absolute value of the difference between the temperature measured by the first temperature measuring unit and the saturation temperature of the pressure measured by the first pressure measuring unit is SC, and the absolute value of the difference between the temperature measured by the second temperature measuring unit and the saturation temperature of the pressure measured by the second pressure measuring unit is SH, the control device controls the opening degree of the first throttle device and the opening degree of the second throttle device so that 3≦(SC)*(SH)≦80 holds during the defrosting operation. do. [Effects of the Invention]

[0007] According to the present disclosure, during defrosting operation, two-phase gas-liquid or liquid refrigerant can be retained in the path from the high-temperature side outlet through the first throttling device and indoor heat exchanger to the second branch, and gas refrigerant can be flowed from the low-temperature side outlet to the second branch. This reduces the amount of liquid refrigerant flowing into the compressor, enabling the air conditioner to perform defrosting operation while suppressing excessive liquid refrigerant flow into the compressor, improving defrosting performance. Furthermore, because the amount of liquid refrigerant flowing into the refrigerant tank is reduced, the outdoor unit in which the refrigerant tank is installed can be made more spacious without increasing the size of the refrigerant tank. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a refrigerant circuit of an air conditioner according to a first embodiment. [Figure 2] 2 is a diagram showing the flow of refrigerant during defrosting operation of the air conditioner according to the first embodiment shown in FIG. [Figure 3] 4 is a flowchart for explaining the control of the opening degree of the first throttle device and the opening degree of the second throttle device by the control device according to the first embodiment. [Figure 4] FIG. 10 is a refrigerant circuit diagram showing a refrigerant flow path of a conventional air conditioner. [Figure 5] FIG. 10 is a schematic diagram showing the distribution of gas and liquid refrigerant during defrosting operation of a conventional air conditioner. [Figure 6] 4 is a diagram showing the dependency of the refrigerant dryness fraction at the compressor inlet of the compressor on the tank size ratio of the refrigerant tank of the air conditioner according to the first embodiment. FIG. [Figure 7] 3 is a schematic diagram showing the distribution of gas and liquid refrigerant during defrosting operation of the air conditioner according to the first embodiment. FIG. [Figure 8] FIG. 3 is a configuration diagram of a first modified example of the air conditioner according to the first embodiment. [Figure 9] FIG. 4 is a configuration diagram of a second modified example of the air conditioner according to the first embodiment. [Figure 10] 10 is a diagram showing an equal liquid refrigerant inflow amount curve for SC and SH of liquid refrigerant flowing into a compressor of an air conditioner according to a second embodiment. [Figure 11]FIG. 11 is a constant liquid refrigerant inflow amount diagram showing the relationship between the opening degree of the first throttling device and the opening degree of the second throttling device of the air conditioner according to the second embodiment. [Figure 12] FIG. 10 is a perspective view showing a first example of an intermediate refrigerant heat exchanger and refrigerant piping around the intermediate refrigerant heat exchanger in an air conditioner according to a third embodiment. [Figure 13] 10 is a perspective view showing a second example of an intermediate refrigerant heat exchanger and refrigerant piping around the intermediate refrigerant heat exchanger 2 in an air conditioner according to Embodiment 3. FIG. [Figure 14] FIG. 10 is a diagram showing an example of a first branch in an air conditioning apparatus according to a third embodiment. [Figure 15] FIG. 10 is a perspective view showing a fourth example of an intermediate refrigerant heat exchanger and refrigerant piping around the intermediate refrigerant heat exchanger in an air conditioner according to the third embodiment. [Figure 16] FIG. 10 is a perspective view illustrating the size of a refrigerant heat exchanger in an air conditioner according to a third embodiment. [Figure 17] FIG. 10 is a diagram showing the sensitivity of the quality of the refrigerant flowing into the compressor to the size of the refrigerant heat exchanger in the air conditioner according to the third embodiment. [Figure 18] FIG. 10 is a diagram showing a refrigerant circuit of an air conditioner according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an air conditioning apparatus according to an embodiment will be described with reference to the drawings. Note that in the drawings, identical components are denoted by the same reference numerals, and duplicate descriptions will be provided only when necessary. The present disclosure may include any combination of possible configurations among the configurations described in the following embodiments. Furthermore, the dimensional relationships between the components in the drawings may differ from the actual relationships. Furthermore, the configurations of the components shown in the entire specification are merely examples and are not limited to the configurations described in the specification. In particular, the combinations of the components are not limited to the combinations in each embodiment, and components described in other embodiments may be applied to other embodiments.

[0010] Embodiment 1. Fig. 1 is a diagram showing a refrigerant circuit of an air conditioner 200 according to embodiment 1. In Fig. 1, black arrows indicate the direction of refrigerant flow during cooling operation and defrosting operation, while dashed arrows indicate the direction of refrigerant flow during heating operation.

[0011] Fig. 2 is a diagram showing the flow of refrigerant during defrost operation of the air conditioner 200 according to embodiment 1 shown in Fig. 1. In Fig. 2, in order to clarify the flow of refrigerant during defrost operation, the flow path switching device 15 and the third throttle device 23, which does not substantially function during defrost operation, are omitted.

[0012] The air conditioner 200 is an apparatus that heats or cools air to be conditioned by utilizing a refrigeration cycle. Refrigeration cycle apparatuses are used for refrigeration or air conditioning purposes, such as refrigerators, freezers, vending machines, refrigeration systems, and water heaters.

[0013] 1, the air conditioner 200 includes an outdoor unit 201 and an indoor unit 202. The air conditioner 200 is connected to a compressor 14, a flow switching device 15, an outdoor heat exchanger 11, a first throttle device 21, an indoor heat exchanger 16, and a refrigerant tank 6. The air conditioner 200 has a main circuit A in which the refrigerant circulates through the compressor 14, the outdoor heat exchanger 11, the first throttle device 21, and the indoor heat exchanger 16 in this order during defrost operation.

[0014] The outdoor unit 201 includes a compressor 14, a flow switching device 15, an outdoor heat exchanger 11, a third throttling device 23, a refrigerant heat exchanger 2, a second throttling device 22, an outdoor fan 13, and a refrigerant tank 6.

[0015] The discharge side of the compressor 14 is connected to the flow path switching device 15 via refrigerant piping 3, and the suction side is connected to the refrigerant tank 6 via refrigerant piping 3. The compressor 14 draws in refrigerant, compresses it into a high-temperature, high-pressure state, and discharges it. The refrigerant compressed by the compressor 14 is discharged and sent to the flow path switching device 15. The compressor 14 is configured, for example, as a rotary compressor, a scroll compressor, a screw compressor, a reciprocating compressor, or the like.

[0016] The flow path switching device 15 is, for example, a four-way valve, or a combination of a two-way valve and a three-way valve. The flow path switching device 15 switches the refrigerant flow direction in the air conditioner 200 between heating operation and cooling operation and defrost operation. During cooling operation and defrost operation, the flow path switching device 15 connects the discharge port of the compressor 14 to the outdoor heat exchanger 11 and switches the refrigerant flow to connect the suction port of the compressor 14 to the indoor heat exchanger 16. During heating operation, the flow path switching device 15 connects the discharge port of the compressor 14 to the indoor heat exchanger 16 and switches the refrigerant flow to connect the suction port of the compressor 14 to the outdoor heat exchanger 11.

[0017] The outdoor heat exchanger 11 functions as an evaporator during heating operation, exchanging heat between the refrigerant that flows into the interior and the outdoor air to evaporate and vaporize the refrigerant. During cooling and defrosting operation, the outdoor heat exchanger 11 functions as a condenser, exchanging heat between the refrigerant that flows into the interior and the outdoor air to condense and liquefy the refrigerant.

[0018] An outdoor fan 13 is disposed adjacent to the outdoor heat exchanger 11 to increase the efficiency of heat exchange between the refrigerant in the outdoor heat exchanger 11 and the outdoor air. The outdoor fan 13 supplies a heat exchange fluid such as air to the outdoor heat exchanger 11.

[0019] The third throttling device 23 is provided between the outdoor heat exchanger 11 and the refrigerant-to-refrigerant heat exchanger 2. The control device 210 may control the dryness of the refrigerant flowing to the outdoor heat exchanger 11 by adjusting the opening ratio of the second throttling device 22 and the third throttling device 23 to flow a portion of the refrigerant from the first branch 31 to the second branch 32 via the low-pressure flow path of the refrigerant-to-refrigerant heat exchanger 2.

[0020] The refrigerant-to-refrigerant heat exchanger 2 is provided between the outdoor heat exchanger 11 and the first throttling device 21, and exchanges heat between the high-pressure refrigerant flowing out from the outdoor heat exchanger 11 during defrosting operation and the low-pressure refrigerant that has been reduced in pressure from the high-pressure refrigerant.

[0021] The refrigerant-to-refrigerant heat exchanger 2 has a high-temperature side passage inlet 51, a high-temperature side passage outlet 52, a low-temperature side passage inlet 53, and a low-temperature side passage outlet .

[0022] The high-temperature side flow passage inlet 51 is connected to the high-temperature side flow passage outlet 52 by a high-temperature side flow passage piping. In the following description, the refrigerant flow passage between the high-temperature side flow passage inlet 51 and the high-temperature side flow passage outlet 52 of the refrigerant-to-refrigerant heat exchanger 2 will be referred to as the high-temperature side flow passage or the high-pressure flow passage. The high-temperature side flow passage inlet 51 is connected to the third throttling device 23, which is provided upstream of the refrigerant during cooling operation and defrosting operation. During cooling operation and defrosting operation, the high-temperature high-pressure refrigerant that has flowed out from the exterior heat exchanger 11 flows into the high-temperature side flow passage inlet 51 via the third throttling device 23.

[0023] The high-temperature side flow passage outlet 52 is connected to the first throttling device 21 and the second throttling device 22 via the first branch 31, and high-pressure refrigerant that has flowed into the high-temperature side flow passage inlet 51 flows out. The first branch 31 is provided in the refrigerant pipe 3 that connects the refrigerant-to-refrigerant heat exchanger 2 and the first throttling device 21. The first branch 31 branches the refrigerant pipe 3 that connects the high-temperature side flow passage outlet 52 and the first throttling device 21 into the refrigerant pipe 3 that connects the low-temperature side flow passage outlet 54 and the second throttling device 22.

[0024] The low-temperature side flow path inlet 53 is connected to the low-temperature side flow path outlet 54 by a low-temperature side flow path piping. In the following description, the refrigerant flow path between the low-temperature side flow path inlet 53 and the low-temperature side flow path outlet 54 of the refrigerant inter-refrigerant heat exchanger 2 will be referred to as the low-temperature side flow path or the low-pressure flow path. The low-temperature side flow path inlet 53 is connected to the second throttling device 22 provided upstream of the refrigerant during cooling operation and defrost operation, and the low-pressure refrigerant flowing out from the second throttling device 22 flows into the low-temperature side flow path inlet 53. The low-temperature side flow path inlet 53 is provided in the refrigerant piping 3 branching from the first branch 31.

[0025] The low-temperature side flow path outlet 54 is connected to a second branch 32 provided on the refrigerant piping 3 connecting the flow path switching device 15 and the refrigerant tank 6, and the low-pressure refrigerant that flows into the low-temperature side flow path inlet 53 flows out.

[0026] The second branch 32 connects the refrigerant pipe 3 connected to the low-temperature side flow path outlet 54 to the refrigerant pipe 3 connecting the flow path switching device 15 and the refrigerant tank 6.

[0027] The refrigerant-to-refrigerant heat exchanger 2 exchanges heat between the refrigerant flowing through the high-temperature side flow path and the refrigerant flowing through the low-temperature side flow path.

[0028] The second throttling device 22 is provided in the refrigerant piping 3 branched from the first branch 31 provided in the refrigerant piping 3 between the first throttling device 21 and the refrigerant-to-refrigerant heat exchanger 2, and reduces the pressure of the high-pressure refrigerant flowing through the branched refrigerant piping 3 to low-pressure refrigerant.

[0029] The second throttling device 22 functions as a pressure reducing valve or an expansion valve, and reduces the pressure of the refrigerant by expanding it. The second throttling device 22 is configured, for example, by an electric expansion valve that can adjust the flow rate of the refrigerant. Note that the second throttling device 22 is not limited to an electric expansion valve, and may be configured as a mechanical expansion valve that uses a diaphragm in the pressure receiving part, a capillary tube, or the like.

[0030] The refrigerant tank 6 is a positive displacement tank that is provided between the flow path switching device 15 and the compressor 14 and that retains liquid refrigerant. The refrigerant tank 6 is a tank that has an inner diameter larger than the diameter of the refrigerant pipe 3.

[0031] The refrigerant tank 6 separates the gas-liquid two-phase refrigerant that flows into the inside of the refrigerant tank 6 from the outside and discharges the gas-main refrigerant. The refrigerant tank 6 has a refrigerant storage function that stores excess refrigerant, and a gas-liquid separation function that separates and retains liquid refrigerant that is temporarily generated when the operating state changes from gas refrigerant. The gas-liquid separation function of the refrigerant tank 6 prevents the air conditioning apparatus 200 from malfunctioning due to liquid compression performed by the compressor 14.

[0032] The first temperature measurement unit 71 is provided in the refrigerant pipe 3, which is the first refrigerant pipe between the high-temperature-side flow path outlet 52 and the first throttle device 21, and measures the temperature of the refrigerant flowing through the first refrigerant pipe.

[0033] The first pressure measuring unit 81 is provided in the first refrigerant pipe and measures the pressure of the refrigerant flowing through the first refrigerant pipe.

[0034] The second temperature measurement unit 72 is provided in the refrigerant pipe 3, which is the second refrigerant pipe between the low-temperature side flow path outlet 54 of the refrigerant-to-refrigerant heat exchanger 2 and the second branch 32, and measures the temperature of the refrigerant flowing through the second refrigerant pipe.

[0035] The second pressure measuring unit 82 is provided in the second refrigerant piping and measures the pressure of the refrigerant flowing through the refrigerant piping 3, which is the second refrigerant piping between the low-temperature side flow path outlet 54 of the refrigerant-to-refrigerant heat exchanger 2 and the second branch 32.

[0036] The control device 210 controls the overall operating state of the air conditioning device 200, such as cooling operation or heating operation. The control device 210 may control the flow path switching device 15, and switch the flow direction of the refrigerant in the refrigerant pipe 3. The control device 210 may also control the compressor 14, and may control the discharge rate of the compressed refrigerant, for example. The control device 210 may also control the rotation rate of the outdoor fan 13. The control device 210 may also adjust the opening degrees of the first throttling device 21, the second throttling device 22, and the third throttling device 23. The control device 210 also performs control processing according to an embodiment described later.

[0037] The control device 210 controls the opening degree of the first throttling device 21 during defrosting operation so that the degree of supercooling based on the temperature measured by the first temperature measuring unit 71 and the pressure measured by the first pressure measuring unit 81 becomes 0°C or higher. When the degree of supercooling is less than 0, the control device 210 reduces the opening degree of the first throttling device 21. When the degree of supercooling is less than 0, the control device 210 controls the opening degree of the second throttling device 22 during defrosting operation so that the degree of superheating based on the temperature measured by the second temperature measuring unit 72 and the pressure measured by the second pressure measuring unit 82 becomes 0°C or higher. When the degree of superheating is less than 0, the control device 210 reduces the opening degree of the second throttling device 22.

[0038] That is, the control device 210 controls the opening degree of the first throttling device 21 so that the temperature measured by the first temperature measuring unit 71 is lower than the saturation temperature of the pressure measured by the first pressure measuring unit 81. The control device 210 controls the opening degree of the second throttling device 22 so that the temperature measured by the second temperature measuring unit 72 is higher than the saturation temperature of the pressure measured by the second pressure measuring unit 82.

[0039] When the processing circuit of the control device 210 is dedicated hardware, the processing circuit may be, for example, a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination of these. Each functional unit realized by the processing circuit may be realized by separate hardware, or each functional unit may be realized by a single piece of hardware. When the processing circuit of the control device 210 is a CPU, each function executed by the processing circuit is realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in a memory unit. The CPU realizes each function of the processing circuit by reading and executing the programs stored in the memory unit. Note that some of the functions of the processing circuit may be realized by dedicated hardware, and some may be realized by software or firmware.

[0040] The indoor unit 202 includes a first throttle device 21 and an indoor heat exchanger 16.

[0041] The first throttling device 21 is provided in the refrigerant pipe 3 and connected to the first branch 31. The first throttling device 21 functions as a pressure reducing valve or an expansion valve, and reduces the pressure of the refrigerant by expanding it. The first throttling device 21 controls the pressure of the refrigerant flowing into the indoor heat exchanger 16 during defrosting operation. The first throttling device 21 is configured, for example, by an electric expansion valve that can adjust the flow rate of the refrigerant. Note that the first throttling device 21 is not limited to an electric expansion valve, and may be configured by a mechanical expansion valve that uses a diaphragm in the pressure receiving section, a capillary tube, or the like.

[0042] The indoor heat exchanger 16 is connected to the first throttling device 21 on the upstream side of the refrigerant flow during cooling operation and defrost operation, and is connected to the flow path switching device 15 on the downstream side of the refrigerant flow during cooling operation and defrost operation.

[0043] The indoor heat exchanger 16 functions as a condenser during heating operation, exchanging heat between the refrigerant that flows into the interior and the indoor air, condensing and liquefying the refrigerant. During cooling operation, the indoor heat exchanger 16 functions as an evaporator, exchanging heat between the refrigerant that flows into the interior and the indoor air, evaporating and vaporizing the refrigerant.

[0044] The downstream side of the refrigerant flow in the indoor heat exchanger 16 during cooling operation and defrosting operation is connected by the refrigerant piping 3 to the low-temperature side flow path outlet 54 and the refrigerant tank 6 via the flow path switching device 15 and the second branch 32. In other words, during cooling operation and defrosting operation, the first branch 31 is connected to the second branch 32 via the second throttling device 22 and the refrigerant-to-refrigerant heat exchanger 2.

[0045] An indoor fan (not shown) is disposed adjacent to the indoor heat exchanger 16 to increase the efficiency of heat exchange between the refrigerant in the indoor heat exchanger 16 and the outdoor air.

[0046] The outdoor heat exchanger 11 and the indoor heat exchanger 16 function as heat exchangers that transfer heat between the refrigerant flowing through the refrigerant pipe 3 and a heat transport medium such as air flowing outside the pipe. The outdoor heat exchanger 11 and the indoor heat exchanger 16 are configured as, for example, a fin-and-tube heat exchanger, a microchannel heat exchanger, a shell-and-tube heat exchanger, a heat pipe heat exchanger, a double-pipe heat exchanger, or a plate heat exchanger.

[0047] The indoor fan (not shown) supplies a heat exchange fluid such as air to the indoor heat exchanger 16. The outdoor fan 13 and the indoor fan are configured as a propeller fan, a line flow fan (registered trademark), a multi-blade centrifugal fan, a water pump, or the like, depending on the working fluid and operating conditions such as flow rate or static pressure.

[0048] <Operation> Next, we will explain the operation of the air conditioner 200. First, we will explain the operation of the air conditioner 200 during heating operation.

[0049] [Operation during heating operation] The high-temperature, high-pressure gas refrigerant compressed by the compressor 14 passes through the flow switching device 15 and flows into the indoor heat exchanger 16, which functions as a condenser. The high-temperature, high-pressure gas refrigerant that flows into the indoor heat exchanger 16 is cooled while supplying heat to the indoor air, and becomes a low-temperature liquid refrigerant, which flows out of the indoor heat exchanger 16. The liquid refrigerant that flows out of the indoor heat exchanger 16 is decompressed by the first throttle device 21, becoming a low-temperature, low-pressure gas-liquid two-phase refrigerant, which flows into the outdoor heat exchanger 11, which functions as an evaporator.

[0050] During this process, the refrigerant flows through the refrigerant-to-refrigerant heat exchanger 2, but at this time, the second throttling device 22 may be closed to allow all of the refrigerant to flow to the outdoor heat exchanger 11. Alternatively, the dryness of the refrigerant flowing to the outdoor heat exchanger 11 may be controlled by adjusting the opening ratio of the second throttling device 22 and the third throttling device 23 to allow part of the refrigerant to flow from the first branch 31 to the second branch 32 via the low-pressure flow path of the refrigerant-to-refrigerant heat exchanger 2.

[0051] The low-temperature, low-pressure, gas-liquid two-phase refrigerant that flows into the outdoor heat exchanger 11 exchanges heat with the air supplied by the outdoor fan 13, and absorbs heat from the outside air, causing the liquid refrigerant in the two-phase state to evaporate and become a low-pressure, single-phase gas refrigerant.

[0052] The low-pressure gas refrigerant that flows out of the outdoor heat exchanger 11 passes through the flow switching device 15 and then flows into the compressor 14, where it is compressed again into high-temperature, high-pressure gas refrigerant.

[0053] During the heating operation described above, if the temperature of the refrigerant flowing through the outdoor heat exchanger 11 is below 0°C, condensed water droplets may form frost on the outside of the pipes of the outdoor heat exchanger 11. If the frost formation progresses, ventilation to the outdoor heat exchanger 11 is obstructed, making it impossible to continue the heating operation. In this case, the frost on the outdoor heat exchanger 11 is melted by the following defrosting operation.

[0054] [Defrost operation] Next, the operation of the air conditioner 200 during defrosting operation will be described.

[0055] The high-temperature, high-pressure gas refrigerant compressed by the compressor 14 passes through the flow switching device 15 and flows into the outdoor heat exchanger 11. The high-temperature, high-pressure gas refrigerant that flows into the outdoor heat exchanger 11 is cooled and condensed by heat dissipation to the frost, and flows out as a low-temperature gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant that flows out of the outdoor heat exchanger 11 exchanges heat with a low-pressure refrigerant in the refrigerant-to-refrigerant heat exchanger 2 to become a single-phase liquid refrigerant, which flows out of the refrigerant-to-refrigerant heat exchanger 2.

[0056] A part of the refrigerant flowing out from the high-temperature side flow path of the refrigerant-to-refrigerant heat exchanger 2 flows to the first throttling device 21 via the first branch 31, and the rest flows into the second throttling device 22.

[0057] The two-phase refrigerant, consisting of low-pressure gas refrigerant and liquid refrigerant, which has been decompressed through the first throttle device 21, flows into the indoor heat exchanger 16. In the indoor heat exchanger 16, an indoor fan (not shown) is stopped to prevent a decrease in the temperature of the indoor space. Although the liquid refrigerant in the two-phase refrigerant that has flowed into the indoor heat exchanger 16 partially evaporates due to heat dissipation through natural convection, the refrigerant flows out as a gas-liquid two-phase refrigerant and flows to the second branch 32 via the flow switching device 15.

[0058] On the other hand, the medium-pressure gas-liquid two-phase refrigerant, mainly liquid, whose pressure has been reduced through the second expansion device 22 flows into the low-temperature side passage inlet 53 of the inter-refrigerant heat exchanger 2, and flows through the low-temperature side passage of the inter-refrigerant heat exchanger 2. The refrigerant flowing through the low-temperature side passage of the inter-refrigerant heat exchanger 2 exchanges heat with the refrigerant flowing through the high-temperature side passage of the inter-refrigerant heat exchanger 2, becoming a low-pressure gas refrigerant, and flows out from the low-temperature side passage outlet 54 of the inter-refrigerant heat exchanger 2.

[0059] The low-pressure gas refrigerant that flows out from the low-temperature side flow passage outlet 54 of the refrigerant-to-refrigerant heat exchanger 2 flows to the second branch 32.

[0060] The low-pressure gas-liquid two-phase refrigerant flowing out of the indoor heat exchanger 16 merges with the gas refrigerant at the second branch 32, becomes a gas-based refrigerant, flows into the compressor 14, is compressed again by the compressor 14, and is discharged. This cycle is then repeated in the air conditioning apparatus 200.

[0061] Next, a description will be given of the control of the opening degree of the first throttling device 21 and the opening degree of the second throttling device 22 by the control device 210 during defrost operation. Fig. 3 is a flowchart for explaining the control of the opening degree of the first throttling device 21 and the opening degree of the second throttling device 22 by the control device 210 according to the first embodiment.

[0062] The control device 210 calculates the degree of subcooling based on the temperature measured by the first temperature measuring unit 71 and the pressure measured by the first pressure measuring unit 81 during the defrosting operation (step S1).

[0063] Next, the control device 210 determines whether the degree of subcooling calculated in step S1 is equal to or greater than 0 (step S2). If it is determined in step S2 that the degree of subcooling is not equal to or greater than 0 (NO in step S2), the control device 210 controls the opening degree of the first expansion device 21 to be smaller than the current opening degree (step S3).

[0064] If it is determined in step S2 that the degree of supercooling is greater than or equal to 0 (YES in step S2) or after processing step S3, the control device 210 calculates the degree of superheat based on the temperature measured by the second temperature measuring unit 72 during defrost operation and the pressure measured by the second pressure measuring unit 82 (step S4).

[0065] Next, the control device 210 determines whether the degree of superheat calculated in step S4 is equal to or greater than 0 (step S5). If it is determined in step S5 that the degree of superheat is not equal to or greater than 0 (NO in step S5), the control device 210 controls the opening degree of the second expansion device 22 to be smaller than the current opening degree (step S6).

[0066] If it is determined in step S5 that the degree of superheat is equal to or greater than 0 (YES in step S5) or after the processing of step S6, the control device 210 returns to the processing of step S1.

[0067] <Effects> Next, we will explain the performance and quality improvement effect of the defrost operation of the air conditioning apparatus 200 according to Embodiment 1. First, we will explain a conventional air conditioning apparatus 200, which is a comparison target for the air conditioning apparatus 200 according to Embodiment 1, using Fig. 4 and Fig. 5.

[0068] Fig. 4 is a refrigerant circuit diagram showing the refrigerant flow path of a conventional air conditioner 200. Fig. 5 is a schematic diagram showing the gas-liquid refrigerant distribution during defrost operation of the conventional air conditioner 200.

[0069] In the configuration of the conventional air conditioner 200 shown in FIG. 4, as shown in FIG. 5, during defrost operation, the gas refrigerant discharged from the compressor 14 dissipates heat to frost in the outdoor heat exchanger 11 and becomes refrigerant 63 in a gas-liquid two-phase or liquid phase state.

[0070] The refrigerant 63 in a gas-liquid two-phase or liquid phase state flows out as a gas-liquid two-phase refrigerant from the indoor heat exchanger 16 in the indoor unit 202 where air flow has stopped, undergoes gas-liquid separation in the refrigerant tank 6, becomes gas-mainly refrigerant 62, and returns to the compressor 14.

[0071] In this case, the refrigerant tank 6 needs to be enlarged in accordance with the number of indoor units 202 and the length of the refrigerant piping 3 connecting the outdoor unit 201 and the indoor unit 202, which puts pressure on the housing space of the outdoor unit 201.

[0072] Therefore, if the size of the outdoor unit 201 is restricted, liquid refrigerant will flow out of the refrigerant tank 6, causing compressor failure due to excessive liquid refrigerant flowing into the compressor 14. Also, the frequency of the compressor 14 is lowered to suppress the amount of liquid refrigerant flowing into the compressor 14. This reduces the amount of refrigerant circulating, degrades defrosting performance, increases the defrosting time during which heating is stopped, and reduces the heating capacity per hour on average, creating a problem in balancing space efficiency and defrosting performance.

[0073] Furthermore, in a conventional air conditioner 200 equipped with a refrigerant-to-refrigerant heat exchanger 2, the second throttling device 22 is fully closed during defrosting operation to supply refrigerant to the indoor unit 202 as in the conventional configuration shown in Fig. 4. Alternatively, when refrigerant pressure loss in the flow path of the refrigerant piping 3 connecting the outdoor unit 201 and the indoor unit 202 becomes large, the second throttling device 22 is controlled to be fully open. Therefore, the effect of retaining liquid refrigerant in the refrigerant piping 3 from the refrigerant-to-refrigerant heat exchanger 2 to the first throttling device 21 is small.

[0074] Furthermore, because the airflow from the indoor unit 202 is stopped, the circulating refrigerant evaporates only through heat dissipation due to natural convection in the indoor heat exchanger 16 and the refrigerant piping 3. Immediately after the start of defrosting, the refrigerant from the high-temperature side flow path outlet 52 of the refrigerant-to-refrigerant heat exchanger 2 to the first throttle device 21 temporarily becomes liquid depending on the amount of heat retained in the indoor heat exchanger 16 and the refrigerant piping 3 during heating operation. As heat is dissipated as the defrosting operation progresses, the refrigerant becomes a gas-liquid two-phase state, which requires less heat to reach the gas phase. As a result, the amount of liquid refrigerant flowing into the compressor 14 increases.

[0075] Next, a description will be given of the effects of embodiment 1. Fig. 6 is a diagram showing the dependency of the refrigerant dryness fraction at the compressor inlet of the compressor 14 on the tank size ratio of the refrigerant tank 6 of the air conditioner 200 according to embodiment 1.

[0076] In Fig. 6, black squares indicate the refrigerant dryness fraction at the compressor inlet of the air conditioner 200 in embodiment 1, and white circles indicate the refrigerant dryness fraction in the conventional air conditioner 200 shown in Fig. 4. In Fig. 6, the conventional tank size is set to 100%.

[0077] 6, when the tank size ratio is 0% to 25%, the refrigerant quality fraction at the compressor inlet in embodiment 1 exceeds the refrigerant quality fraction in the conventional air conditioner 200. This shows that there is an effect of suppressing the inflow of liquid refrigerant into the refrigerant tank 6. Furthermore, when the tank size ratio is 20%, the refrigerant quality fraction at the compressor inlet becomes 1, which shows that there is an effect of reducing the size of the refrigerant tank 6.

[0078] FIG. 7 is a schematic diagram showing the gas-liquid refrigerant distribution during defrosting operation of the air conditioner 200 according to the first embodiment.

[0079] Refrigerant 63 in a gas-liquid two-phase or liquid phase state flows in the refrigerant pipe 3 between the refrigerant-to-refrigerant heat exchanger 2 and the indoor heat exchanger 16. Liquid-main refrigerant 61 flows in the indoor heat exchanger 16. Therefore, refrigerant 63 in a gas-liquid two-phase or liquid phase state, which flows at a slower rate than gas-phase refrigerant, is held in the refrigerant pipe 3 between the refrigerant-to-refrigerant heat exchanger 2 and the indoor heat exchanger 16. In the indoor heat exchanger 16, liquid-main refrigerant 61, which flows at a slower rate than gas-phase refrigerant, is held in the liquid-main refrigerant pipe 3. This makes it possible to suppress the flow of liquid refrigerant into the compressor 14 per volume of the refrigerant tank 6 and to reduce the volume of the refrigerant tank 6 per quality fraction flowing into the compressor 14, thereby achieving both improved defrosting performance and space efficiency.

[0080] By setting the degree of subcooling to 0°C or higher, the refrigerant pipe 3 between the refrigerant-to-refrigerant heat exchanger 2 and the indoor heat exchanger 16 can be made liquid, but as the degree of subcooling increases, the change in the refrigerant density is small, and therefore the change in the amount of liquid refrigerant retained is also small. On the other hand, because the refrigerant enthalpy at the outlet of the first throttling device 21 decreases, the enthalpy of the refrigerant joining at the second branch 32 decreases, and the amount of liquid refrigerant flowing into the compressor 14 may increase.

[0081] Furthermore, for example, in cooling operation in which the indoor unit 202 blows air, a portion of the refrigerant is made to flow from the first branch 31 to the refrigerant-to-refrigerant heat exchanger 2 via the second throttling device 22, mainly for the purpose of reducing refrigerant pressure loss from the indoor heat exchanger 16 to the second branch 32. This provides a means for increasing the degree of subcooling of the refrigerant at the high-temperature side flow path outlet 52 of the refrigerant-to-refrigerant heat exchanger 2 and reducing the refrigerant flow rate. However, if similar control is performed in defrost operation in which the indoor unit 202 does not blow air, the liquid refrigerant cannot evaporate, increasing the amount of liquid inflow into the compressor 14 and causing a deterioration in quality.

[0082] Therefore, particularly in an air conditioner 200 in which the refrigerant piping 3 connecting the outdoor unit 201 and the indoor unit 202 is approximately 40 m or less, the control device 210 controls the opening degree of the first throttling device 21 so that the degree of subcooling is between 0°C and 10°C during defrosting operation. This has a significant effect in suppressing the inflow of liquid refrigerant into the compressor 14, enabling improved defrosting performance and increased comfort.

[0083] <First Modification> FIG. 8 is a configuration diagram of a first modified example of the air conditioner 200 according to the first embodiment. Note that in FIG. 8, the flow path switching device 15 is omitted to clarify the flow of refrigerant during defrosting operation. The difference from FIG. 2 is the positions of the first pressure measurement unit 81 and the second pressure measurement unit 82. As shown in FIG. 8, the first pressure measurement unit 81 is provided in the outdoor heat exchanger 11. The second pressure measurement unit 82 is provided in the refrigerant pipe 3 between the second throttle device 22 and the low-temperature side flow path inlet 53. In FIG. 8, the first pressure measurement unit 81 and the second pressure measurement unit 82 measure the pressure of the refrigerant by measuring the temperature in the gas-liquid two-phase region.

[0084] <Second Modification> Fig. 9 is a configuration diagram of a second modified example of the air conditioning apparatus 200 according to the first embodiment. Note that in Fig. 8, the flow path switching device 15 is omitted to clarify the refrigerant flow during defrosting operation. The difference from Fig. 8 is the location of the first temperature measurement unit 71. As shown in Fig. 9, the first temperature measurement unit 71 is not provided in the outdoor unit 201, but in the refrigerant piping 3, which is the third refrigerant piping between the indoor unit 202 closer to the indoor unit 202 and the outdoor unit 201.

[0085] Specifically, as shown by the bisector W in Figure 9, when the length of the path of the refrigerant piping 3, which is the third refrigerant piping connecting the refrigerant-to-refrigerant heat exchanger 2 and the first throttling device 21, is virtually divided into two equal parts, the first temperature measuring unit 71 is provided on the third refrigerant piping closer to the first throttling device 21.

[0086] If the refrigerant piping 3 connecting the outdoor unit 201 and the indoor unit 202 becomes long, pressure loss due to flow resistance in the piping causes the refrigerant to become a gas-liquid two-phase state in which the density is lower than that of liquid refrigerant in the flow path up to the first throttling device 21. This may reduce the amount of refrigerant held in the refrigerant piping 3 between the refrigerant-to-refrigerant heat exchanger 2 and the indoor heat exchanger 16, and increase the amount of liquid refrigerant flowing into the compressor 14.

[0087] Therefore, the first temperature measurement unit 71 is provided in a position on the refrigerant piping 3 path connecting the refrigerant-to-refrigerant heat exchanger 2 and the first throttling device 21, close to the first throttling device 21 when the piping length is virtually divided into two equal parts. This maintains a supercooled state of the refrigerant, suppresses gas-liquid two-phase formation due to flow resistance, and improves the effect of suppressing the inflow of liquid refrigerant into the compressor 14, thereby enabling improved defrosting performance.

[0088] 9, the first temperature measuring unit 71 is shown outside the outdoor unit 201, but it may be provided inside the indoor unit 202. Furthermore, as long as the first temperature measuring unit 71 is provided at a position closer to the refrigerant piping 3 than at least one indoor unit 202 with respect to the outdoor unit 201, there is no impediment to the effectiveness of the first temperature measuring unit 71 even if a branch unit or the like that supplies refrigerant to multiple indoor units 202 is provided.

[0089] In a configuration in which the first branch 31 is provided between the outdoor heat exchanger 11 and the refrigerant-to-refrigerant heat exchanger 2, controllability is reduced due to uneven distribution of the gas-liquid two-phase refrigerant in the first branch 31 and the flow of the gas-liquid two-phase refrigerant into the second throttling device 22. If the flow rate of gas refrigerant flowing into the second branch 32 is unstable and a large amount of refrigerant flows into the main circuit A, the flow rate of gas-liquid two-phase refrigerant on the main circuit A side merging into the second branch 32 increases. If a large amount of refrigerant flows into the second branch 32, the refrigerant phase state merging into the second branch 32 changes from gas to two-phase, which reduces the refrigerant quality at the merging portion of the second branch 32 and causes an excessive amount of liquid refrigerant to flow into the compressor 14, resulting in compressor failure and reduced defrosting performance.

[0090] The air conditioning apparatus 200 described above is an example of the air conditioning apparatus 200 according to embodiment 1. For example, the number of outdoor units 201 and indoor units 202 is not limited to one, and the air conditioning apparatus 200 may be provided with a plurality of units.

[0091] Furthermore, there are no particular limitations on the type of refrigerant circulating through the air conditioner 200. The refrigerant may be R32 refrigerant, R410A, or a refrigerant containing at least an olefin-based refrigerant, propane, or DME (dimethyl ether) with a lower gas density than R32 refrigerant. With such a refrigerant, the reduction in the amount of refrigerant circulating due to the lower pressure of the refrigerant drawn into the compressor 14 can be suppressed, resulting in a greater improvement in defrosting performance.

[0092] Embodiment 2. In the second embodiment, the configuration of the air conditioner 200 is the same as in the first embodiment, and the same parts as in FIG. 1 are denoted by the same reference numerals.

[0093] Fig. 10 is a diagram showing equal liquid refrigerant inflow rates for SC and SH of liquid refrigerant flowing into the compressor 14 of the air conditioner 200 according to embodiment 2. Fig. 11 is a diagram showing equal liquid refrigerant inflow rates in Fig. 10, illustrating the relationship between the opening degree of the first throttling device 21 and the opening degree of the second throttling device 22 of the air conditioner 200 according to embodiment 2.

[0094] The control device 210 of the air conditioner 200 according to the second embodiment controls the opening degree of the first throttle device 21 and the opening degree of the second throttle device 22 during defrost operation so that 3≦(SC)*(SH)≦80.

[0095] Here, SC is the absolute value of the difference between the temperature measured by the first temperature measuring unit 71 and the saturation temperature of the pressure measured by the first pressure measuring unit 81. SH is the absolute value of the difference between the temperature measured by the second temperature measuring unit 72 and the saturation temperature of the pressure measured by the second pressure measuring unit 82.

[0096] Regarding the saturation temperature of the pressure, a separate pressure measuring means may be provided and the saturation temperature may be measured by this pressure measuring means.

[0097] 10, when (SC)*(SH) becomes small, the amount of liquid refrigerant held in the refrigerant pipe 3 between the refrigerant-to-refrigerant heat exchanger 2 and the indoor heat exchanger 16 and the effect of improving the quality fraction in the second branch 32 decrease, and the amount of liquid flowing into the compressor 14 increases. As a result, the compressor 14 may break down and the size of the refrigerant tank 6 must be increased.

[0098] On the other hand, when (SC)*(SH) is large, the openings of the first and second throttling devices 21 and 22 are small, which increases the difference between the condensing pressure and the evaporating pressure, reducing the density of the refrigerant drawn into the compressor and decreasing the amount of refrigerant circulating. This reduces the defrosting performance and extends the heating stop time.

[0099] 11, when (SC)*(SH) is smaller than 3, the control device 210 reduces the opening degrees of the first throttling device 21 and the second throttling device 22 from the current opening degrees. When (SC)*(SH) is larger than 80, the control device 210 increases the opening degrees of the first throttling device 21 and the second throttling device 22 from the current opening degrees. There is no problem with the effectiveness regardless of the order in which the opening degrees of the first throttling device 21 and the second throttling device 22 are controlled.

[0100] If 3≦(SC)*(SH)≦80, the control device 210 does not change the current opening degrees of the first and second throttle devices 21 and 22.

[0101] When (SC)*(SH) is smaller than 3 and (SC) is small relative to (SH), the control device 210 reduces the opening degree of the second throttling device 22 from the current opening degree. When (SC)*(SH) is smaller than 3 and (SC) is large relative to (SH), the control device 210 reduces the opening degree of the second throttling device 22 from the current opening degree.

[0102] When (SC)*(SH) is smaller than 3, and (SC) is smaller than (SH), the control device 210 controls the opening of the first throttling device 21 to be smaller. In this case, the amount of liquid refrigerant held in the refrigerant pipe 3 between the refrigerant-to-refrigerant heat exchanger 2 and the indoor heat exchanger 16 is improved, which significantly reduces the amount of liquid flowing into the compressor 14.

[0103] When (SC)*(SH) is greater than 80 and (SC) is small relative to (SH), the control device 210 increases the opening degree of the second throttling device 22 from the current opening degree. When (SC)*(SH) is greater than 80 and (SC) is large relative to (SH), the control device 210 increases the opening degree of the first throttling device 21 from the current opening degree.

[0104] When (SC)*(SH) is greater than 80, and (SC) is greater than (SH), the control device 210 controls the opening of the first throttling device 21 to be greater than the current opening. In this case, the improvement in the amount of circulating mainstream refrigerant flowing through the refrigerant pipe 3 between the refrigerant-to-refrigerant heat exchanger 2 and the indoor heat exchanger 16 significantly improves defrosting performance, thereby improving comfort.

[0105] Embodiment 3. In the third embodiment, the configuration of the air conditioner 200 is the same as the configuration of the air conditioner 200 in either the first or second embodiment, and the same components will be described using the same reference numerals.

[0106] <Example 1> Fig. 12 is a perspective view showing a first example of an inter-refrigerant heat exchanger 2 and refrigerant piping 3 around the inter-refrigerant heat exchanger 2 in an air conditioning apparatus 200 according to embodiment 3. As shown in Fig. 12, the inter-refrigerant heat exchanger 2 is a plate-type heat exchanger having a plurality of plates 1 in which flow paths for high-pressure refrigerant and flow paths for low-pressure refrigerant are arranged alternately in the horizontal direction.

[0107] The high-temperature side channel inlet 51 and the low-temperature side channel outlet 54 are provided above the high-temperature side channel outlet 52 and the low-temperature side channel inlet 53 .

[0108] The high-temperature side flow passage inlet 51 is provided at the upper part of the side surface of the plate 1 on the first temperature measurement unit 71 side among the multiple plates 1 parallel to the gravity direction 100. The high-temperature side flow passage inlet 51 is provided at the same height as the low-temperature side flow passage outlet 54. During defrosting operation or cooling operation, high-pressure refrigerant flows into the high-temperature side flow passage inlet 51 from the outdoor heat exchanger 11.

[0109] The high-temperature-side passage outlet 52 is provided at the bottom of the side surface of the plate 1 on the first temperature measurement unit 71 side among the multiple plates 1 parallel to the gravity direction 100. The high-temperature-side passage outlet 52 is provided at the same height as the low-temperature-side passage inlet 53. During defrosting operation or cooling operation, the high-pressure refrigerant flowing in from the high-temperature-side passage inlet 51 exchanges heat with the low-temperature refrigerant flowing in from the low-temperature-side passage inlet 53 to become a low-temperature refrigerant. The low-temperature refrigerant after heat exchange flows out from the high-temperature-side passage outlet 52.

[0110] The low-temperature side flow passage inlet 53 is provided at the bottom of the side of the plate 1 on the first temperature measurement unit 71 side among the multiple plates 1 parallel to the gravity direction 100. During defrosting operation or cooling operation, the refrigerant that leaves the high-temperature side flow passage outlet 52, branches at the first branch 31, and flows through the U-shaped refrigerant pipe 3 in which the second throttle device 22 is provided flows into the low-temperature side flow passage inlet 53.

[0111] 1, the refrigerant pipe 3 extending beyond the first branch 31 along the straight refrigerant pipe 3 connecting the high-temperature-side flow path outlet 52 and the first branch 31 is connected to the first throttle device 21. A first pressure measuring unit 81 and a first temperature measuring unit 71 are provided on the other branched refrigerant pipe 3.

[0112] The low-temperature side flow passage outlet 54 is provided at the upper part of the side surface of the plate 1 on the first temperature measurement unit side among the multiple plates 1 parallel to the gravity direction 100. During defrosting operation or cooling operation, the low-temperature refrigerant that has undergone heat exchange from the low-temperature side flow passage inlet 53 flows into the low-temperature side flow passage outlet 54. The refrigerant pipe 3 connected to the low-temperature side flow passage outlet 54 is provided with a second temperature measurement unit 72 and a second pressure measurement unit 82. The refrigerant pipe 3 provided with the second temperature measurement unit 72 and the second pressure measurement unit 82 is connected to the second branch 32, as shown in FIG. 1 .

[0113] Of the gas-liquid two-phase refrigerant that flows out from the high-temperature side passage outlet 52, most of the gas refrigerant branches off at the first branch 31 and flows from the low-temperature side passage inlet 53 into the refrigerant-to-refrigerant heat exchanger 2, which is a plate-type heat exchanger. Of the gas-liquid two-phase refrigerant that flows out from the high-temperature side passage outlet 52, the liquid refrigerant flows straight through the first branch 31 toward the first throttling device 21. This increases the refrigerant density in the refrigerant piping 3 from the refrigerant-to-refrigerant heat exchanger 2 to the first throttling device 21.

[0114] Here, consider an example in which the plate-type refrigerant-to-refrigerant heat exchanger 2 has flow paths in the direction of gravity 100, but unlike the first example, the high-temperature-side flow path inlet 51 is located below the direction of gravity and the high-temperature-side flow path outlet 52 is located above the direction of gravity. In this case, during defrosting operation, the gas phase of the two-phase refrigerant flowing from the outdoor heat exchanger 11 is lighter than the liquid phase and therefore less likely to exchange heat due to buoyancy. Furthermore, the gas phase of this two-phase refrigerant flows out from the high-temperature-side flow path outlet 52. This reduces the refrigerant density in the refrigerant piping 3 from the refrigerant-to-refrigerant heat exchanger 2 to the first throttle device 21, thereby reducing the amount of refrigerant held. As a result, the amount of liquid flowing into the compressor 14 increases, which can lead to compressor failure and other quality degradation, and requires an increase in the size of the refrigerant tank 6 to avoid failure.

[0115] The plate-type refrigerant-to-refrigerant heat exchanger 2 shown in the first example of embodiment 3 has the high-temperature side flow path inlet 51 on the gravity side and the high-temperature side flow path outlet 52 on the gravity side during defrosting operation, thereby preventing the gas refrigerant from flowing out of the high-pressure refrigerant outlet without heat exchange, thereby improving defrosting performance.

[0116] <Example 2> Fig. 13 is a perspective view showing a second example of an inter-refrigerant heat exchanger 2 and refrigerant piping 3 around the inter-refrigerant heat exchanger 2 in an air conditioning apparatus 200 according to embodiment 3. As shown in Fig. 13, the inter-refrigerant heat exchanger 2 is a plate-type heat exchanger having a plurality of plates 1 in which flow paths for high-pressure refrigerant and flow paths for low-pressure refrigerant are alternately arranged in a direction horizontal to the direction of gravity 100.

[0117] The high temperature side channel outlet 52 and the low temperature side channel outlet 54 are provided above the high temperature side channel inlet 51 and the low temperature side channel inlet 53 .

[0118] The high-temperature side flow passage inlet 51 is provided at the upper part of the side surface of the plate 1 on the first temperature measurement unit 71 side among the multiple plates 1 parallel to the gravity direction 100. The high-temperature side flow passage inlet 51 is provided at the same height as the low-temperature side flow passage inlet 53. During defrosting operation or cooling operation, high-pressure refrigerant flows into the high-temperature side flow passage inlet 51 from the outdoor heat exchanger 11.

[0119] The high-temperature-side passage outlet 52 is provided at the upper part of the side surface of the plate 1 on the first temperature measurement unit 71 side among the multiple plates 1 parallel to the gravity direction 100. The high-temperature-side passage outlet 52 is provided at the same height as the low-temperature-side passage outlet 54. During defrosting operation or cooling operation, the high-pressure refrigerant flowing in from the high-temperature-side passage inlet 51 exchanges heat with the low-temperature refrigerant flowing in from the low-temperature-side passage inlet 53 to become a low-temperature refrigerant. The low-temperature refrigerant after heat exchange flows out from the high-temperature-side passage outlet 52.

[0120] The low-temperature side flow passage inlet 53 is provided at the bottom of the side of the plate 1 on the first temperature measurement unit 71 side among the multiple plates 1 parallel to the gravity direction 100. During defrosting operation or cooling operation, a portion of the low-temperature refrigerant output from the high-temperature side flow passage outlet 52 branches off at the first branch 31, and the refrigerant flows into the low-temperature side flow passage inlet 53 after flowing through the U-shaped refrigerant pipe 3 in which the second throttle device 22 is provided.

[0121] The refrigerant pipe 3 connecting the high-temperature-side flow passage outlet 52 and the low-temperature-side flow passage inlet 53 extends upward from the high-temperature-side flow passage outlet 52, goes straight past the first branch 31, bends in a U-shape above the first branch 31, and extends downward. The other refrigerant pipe 3 branched off at the first branch 31 extends generally horizontally and is connected to the first throttle device 21 as shown in FIG. 1. A first pressure measuring unit 81 and a first temperature measuring unit 71 are provided on the other branched refrigerant pipe 3.

[0122] The low-temperature side flow passage outlet 54 is provided at the upper part of the side surface of the plate 1 on the first temperature measurement unit 71 side of the multiple plates 1 parallel to the gravity direction 100. During defrosting operation or cooling operation, the low-temperature refrigerant that has undergone heat exchange from the low-temperature side flow passage inlet 53 flows into the low-temperature side flow passage outlet 54. The refrigerant pipe 3 connected to the low-temperature side flow passage outlet 54 is provided with the second temperature measurement unit 72 and the second pressure measurement unit 82. The refrigerant pipe 3 provided with the second temperature measurement unit 72 and the second pressure measurement unit 82 is connected to the second branch 32, as shown in FIG. 1 .

[0123] Of the gas-liquid two-phase refrigerant that flows out from the high-temperature side passage outlet 52, most of the gas refrigerant flows straight through the first branch 31 and flows into the inter-refrigerant heat exchanger 2, which is a plate-type heat exchanger, from the low-temperature side passage inlet 53 provided downward. Of the gas-liquid two-phase refrigerant that flows out from the high-temperature side passage outlet 52, the liquid refrigerant branches off at the first branch 31 and flows toward the first throttling device 21. This increases the refrigerant density in the refrigerant piping 3 from the inter-refrigerant heat exchanger 2 to the first throttling device 21.

[0124] In the second example of the refrigerant heat exchanger 2, the main driving source for the gas-liquid branch in the first branch 31 is the gravitational difference due to the difference in gas-liquid density between the gas refrigerant (light) and the liquid refrigerant (heavy).

[0125] <Example 3> Fig. 14 is a diagram showing an example of the first branch 31 in the air conditioning apparatus 200 according to embodiment 3. Fig. 14 shows an example of the first branch 31 in the air conditioning apparatus 200 according to embodiment 3 shown in Fig. 13.

[0126] 14, the refrigerant pipe 3 provided with the first branch 31 has an inlet 31a, a first outlet 31b, and a second outlet 31c. Refrigerant flows into the inlet 31a during defrosting operation. The refrigerant that flows into the inlet 31a flows out through the first outlet 31b to the second throttling device 22. The refrigerant that flows into the inlet 31a flows out through the second outlet 31c to the first throttling device 21.

[0127] The intersection of a line segment connecting the centers of the inlet 31a, a line segment connecting the centers of the first outlet 31b, and a line segment connecting the centers of the second outlet 31c is defined as an intersection center 31o.

[0128] The first unit vector 91 is the unit vector of the line segment connecting the intersection center 31o to the center of the inlet 31a. The second unit vector 92 is the unit vector of the line segment connecting the intersection center 31o to the center of the first outlet 31b. The third unit vector 93 is the unit vector of the line segment connecting the intersection center 31o to the center of the second outlet 31c.

[0129] In FIG. 13, the component of the second unit vector 92 in the direction of gravity 100 (negative direction) is smaller than the component of the third unit vector 93 in the direction of gravity 100 (positive direction).

[0130] The inlet 31a, the first outlet 31b, and the second outlet 31c each have a maximum flow path diameter of d, and are located within 5d from the center 31o of the branch intersection.

[0131] The dot product of the unit vectors is smallest (-1) when the inlet 31a and the first outlet 31b are positioned opposite each other as viewed from the intersection center 31o of the branch flow paths, and is largest (1) when the inlet 31a and the first outlet 31b are positioned in the same place. The dot product of the unit vectors is smallest (-1) when the inlet 31a and the second outlet 31c are positioned opposite each other as viewed from the intersection center 31o of the branch flow paths, and is largest (1) when the inlet 31a and the second outlet 31c are positioned in the same place.

[0132] 14, the shape of the first branch 31 is illustrated as a Y-shape, but it may be a T-shape or the like as long as the dot product of the first unit vector 91 and the second unit vector 92 is smaller than the dot product of the first unit vector 91 and the third unit vector 93. In addition, another branch may be connected to the first branch 31.

[0133] 14, the first branch 31 has a straight pipe extending from the inlet 31a to the first outlet 31b, and the second outlet 31c is connected to the straight pipe. When the angle formed by the line segment connecting the centers of the inlet 31a and the line segment connecting the centers of the first outlet 31b is 90°, the refrigerant-to-refrigerant heat exchanger 2 has the configurations shown in FIGS. 12, 13, and 15.

[0134] In the refrigerant-to-refrigerant heat exchanger 2 of the third example of the third embodiment, the flow of gas refrigerant flowing out from the high-temperature-side passage outlet 52 into the low-temperature-side passage inlet 53 is improved by buoyancy due to the difference in gas-liquid density in the first branch 31. As a result, the refrigerant density increases in the refrigerant piping 3 from the refrigerant-to-refrigerant heat exchanger 2, where the amount of liquid refrigerant inflow increases, to the first throttle device 21, improving the amount of refrigerant held, suppressing the amount of liquid inflow into the compressor 14 and suppressing quality degradation.

[0135] Furthermore, by providing the refrigerant-to-refrigerant heat exchanger 2 as in the second example, the inertial force of the gas refrigerant, which has a higher flow velocity than the liquid refrigerant in the first branch 31, improves the flow of the gas refrigerant flowing out from the high-temperature-side passage outlet 52 into the low-temperature-side passage inlet 53. This increases the refrigerant density in the refrigerant piping 3 from the refrigerant-to-refrigerant heat exchanger 2, where the amount of liquid refrigerant inflow increases, to the first throttle device 21, thereby improving the amount of refrigerant held. This reduces the amount of liquid refrigerant flowing into the compressor 14, thereby suppressing quality degradation.

[0136] <Example 4> Fig. 15 is a perspective view showing a fourth example of an inter-refrigerant heat exchanger 2 and refrigerant piping 3 around the inter-refrigerant heat exchanger 2 in an air conditioning apparatus 200 according to embodiment 3. As shown in Fig. 15, the inter-refrigerant heat exchanger 2 is a plate-type heat exchanger having a plurality of plates 1 in which flow paths for high-pressure refrigerant and flow paths for low-pressure refrigerant are alternately arranged in a direction parallel to the direction of gravity 100.

[0137] The high temperature side channel outlet 52 and the low temperature side channel outlet 54 are provided above the high temperature side channel inlet 51 and the low temperature side channel inlet 53 .

[0138] The high-temperature side flow passage inlet 51 is provided at the bottom of the side of the plate 1 on the first temperature measurement unit 71 side among the multiple plates 1 parallel to the gravity direction 100. The high-temperature side flow passage inlet 51 is provided at the same height as the low-temperature side flow passage inlet 53. During defrosting operation or cooling operation, high-pressure refrigerant flows into the high-temperature side flow passage inlet 51 from the outdoor heat exchanger 11.

[0139] The high-temperature-side passage outlet 52 is provided at the upper part of the side surface of the plate 1 on the first temperature measurement unit 71 side among the multiple plates 1 parallel to the gravity direction 100. The high-temperature-side passage outlet 52 is provided at the same height as the low-temperature-side passage outlet 54. During defrosting operation or cooling operation, the high-pressure refrigerant flowing in from the high-temperature-side passage inlet 51 exchanges heat with the low-temperature refrigerant flowing in from the low-temperature-side passage inlet 53 to become a low-temperature refrigerant. The low-temperature refrigerant after heat exchange flows out from the high-temperature-side passage outlet 52.

[0140] The low-temperature side flow passage inlet 53 is provided at the bottom of the side of the plate 1 on the first temperature measurement unit 71 side among the multiple plates 1 parallel to the gravity direction 100. During defrosting operation or cooling operation, a portion of the low-temperature refrigerant output from the high-temperature side flow passage outlet 52 branches off at the first branch 31, and the refrigerant flows into the low-temperature side flow passage inlet 53 after flowing through the U-shaped refrigerant pipe 3 in which the second throttle device 22 is provided.

[0141] The refrigerant pipe 3 connecting the high-temperature-side passage outlet 52 and the low-temperature-side passage inlet 53 has a U-shape that extends horizontally from the high-temperature-side passage outlet 52, curves downward, and then extends horizontally in a folded manner to reach the low-temperature-side passage inlet 53. Of the two straight portions that extend horizontally in this U-shape, a first branch 31 is provided on the lower straight portion. The other refrigerant pipe 3 branched off at the first branch 31 is connected to the first throttle device 21 as shown in FIG. 1. A first pressure measurement unit 81 and a first temperature measurement unit 71 are provided on the other branched refrigerant pipe 3. The refrigerant pipe 3 provided with the first pressure measurement unit 81 and the first temperature measurement unit 71 intersects the lower straight portion that extends horizontally of the U-shape.

[0142] The low-temperature side flow passage outlet 54 is provided at the upper part of the side surface of the plate 1 on the first temperature measurement unit 71 side of the multiple plates 1 parallel to the gravity direction 100. During defrosting operation or cooling operation, the low-temperature refrigerant that has undergone heat exchange from the low-temperature side flow passage inlet 53 flows into the low-temperature side flow passage outlet 54. The refrigerant pipe 3 connected to the low-temperature side flow passage outlet 54 is provided with the second temperature measurement unit 72 and the second pressure measurement unit 82. The refrigerant pipe 3 provided with the second temperature measurement unit 72 and the second pressure measurement unit 82 is connected to the second branch 32, as shown in FIG. 1 .

[0143] Of the gas-liquid two-phase refrigerant that flows out from the high-temperature side passage outlet 52, most of the gas refrigerant flows straight through the first branch 31 and flows into the inter-refrigerant heat exchanger 2, which is a plate-type heat exchanger, from the low-temperature side passage inlet 53 provided downward. Of the gas-liquid two-phase refrigerant that flows out from the high-temperature side passage outlet 52, the liquid refrigerant branches off at the first branch 31 and flows toward the first throttling device 21. This increases the refrigerant density in the refrigerant piping 3 from the inter-refrigerant heat exchanger 2 to the first throttling device 21.

[0144] By providing the refrigerant-to-refrigerant heat exchanger 2 as in the fourth example, the flow of gas refrigerant flowing out from the high-temperature-side passage outlet 52 into the low-temperature-side passage inlet 53 is improved by the inertial force of the gas refrigerant, which has a higher flow velocity than the liquid refrigerant in the first branch 31. As a result, the refrigerant density increases in the refrigerant piping 3 from the refrigerant-to-refrigerant heat exchanger 2 to the first throttle device 21, where the amount of liquid refrigerant inflow increases, and the amount of refrigerant held is improved, suppressing the amount of liquid inflow into the compressor 14 and preventing quality degradation.

[0145] The refrigerant-to-refrigerant heat exchanger 2 of the fourth example has the high-temperature-side flow path outlet 52 in defrost operation above the direction of gravity 100 and the high-temperature-side flow path inlet 51 below the direction of gravity 100. In the example shown in Fig. 14, of the refrigerant outlets of the first branch 31, the first outlet 31b connected to the low-temperature-side flow path inlet 53 of the refrigerant-to-refrigerant heat exchanger 2 via the second throttling device 22 is provided above the direction of gravity 100 with respect to the second outlet 31c connected to the first throttling device 21.

[0146] In the fourth example of the refrigerant-to-refrigerant heat exchanger 2, the inner product of the first unit vector 91 and the second unit vector 92 is smaller than the inner product of the first unit vector 91 and the third unit vector 93.

[0147] In the fourth example of the refrigerant-to-refrigerant heat exchanger 2, the driving source for the gas-liquid branching in the first branch 31 is the gas flow velocity of the refrigerant, and the main driving source is the difference in inertial force from the high-temperature side flow path outlet 52 to the low-temperature side flow path inlet 53.

[0148] The gas refrigerant flowing out from the high-temperature side passage outlet 52 flows into the low-temperature side passage inlet 53 more efficiently in the first branch 31 due to the buoyancy caused by the difference in gas-liquid density and the inertial force from the refrigerant-to-refrigerant heat exchanger 2 to the first branch 31.

[0149] This increases the refrigerant density in the refrigerant piping 3 from the refrigerant-to-refrigerant heat exchanger 2, where the amount of liquid refrigerant flowing in increases, to the first throttle device 21, thereby improving the amount of refrigerant held in the refrigerant. This reduces the amount of liquid flowing into the compressor 14, improving defrosting performance and comfort.

[0150] <Example 5> FIG. 16 is a perspective view illustrating the size of the refrigerant-to-refrigerant heat exchanger 2 in the air conditioner 200 according to the third embodiment.

[0151] In defrost operation in the air conditioner 200 according to the third embodiment, the flow rate of the refrigerant flowing from the low-temperature side passage inlet 53 to the low-temperature side passage outlet 54 is greater than in the conventional refrigerant-to-refrigerant heat exchanger 2.

[0152] As shown in Figure 16, the refrigerant-to-refrigerant heat exchanger 2 is a plate-type heat exchanger having multiple plates 1 in which high-pressure refrigerant flow paths and low-pressure refrigerant flow paths are arranged alternately in a direction horizontal to the direction of gravity 100.

[0153] In the refrigerant heat exchanger 2 of the third embodiment, where X is the length in the flow path stacking direction perpendicular to gravity, Y is the length in the direction perpendicular to gravity and perpendicular to the flow path stacking direction, and Z is the height direction parallel to gravity, Z / (XY) is 0.01 or more and 0.1 or less.

[0154] When Z / (XY) increases, the flow rate of gas refrigerant flowing through the bypass passage from the low-temperature side passage outlet 54 to the second branch 32 decreases due to increased pressure loss, and the quality of the refrigerant flowing into the compressor 14 decreases. On the other hand, when Z / (XY) decreases, the two-phase distribution performance in the passage lamination direction and the passage surface direction at the low-temperature side passage inlet 53 of the refrigerant-to-refrigerant heat exchanger 2 decreases, and sufficient heat exchanger performance cannot be obtained, resulting in a decrease in the quality of the refrigerant flowing into the compressor 14. If the size of the refrigerant-to-refrigerant heat exchanger 2 is increased to improve performance, the space available for the equipment decreases.

[0155] In the figure, the high-temperature side flow path inlet 51, the high-temperature side flow path outlet 52, the low-temperature side flow path inlet 53, and the low-temperature side flow path outlet 54 are shown arranged so that the high-temperature side and low-temperature side flow paths intersect when viewed through the stacking direction of the plate 1, but they may also be arranged so that they are parallel.

[0156] Fig. 17 is a diagram showing the sensitivity of the quality of the refrigerant flowing into the compressor 14 in the air conditioner 200 according to the third embodiment to the size of the refrigerant-to-refrigerant heat exchanger 2. Fig. 17 shows the improvement rate of the intake quality compared to a conventional air conditioner configuration that does not have the refrigerant-to-refrigerant heat exchanger 2.

[0157] 17, the inventors' tests have confirmed that configuring the refrigerant-to-refrigerant heat exchanger 2 so that Z / (XY) is in the range of 0.01≦Z / (XY)≦0.1 improves the maximum improvement in intake dryness fraction by 50% or more compared to the conventional configuration. Therefore, the air conditioning apparatus 200 according to the third embodiment can achieve both defrosting performance and space efficiency.

[0158] Embodiment 4. Fig. 18 is a diagram showing a refrigerant circuit of an air conditioner 200 according to embodiment 4. Note that the same parts as those in Fig. 1 will be described with the same reference numerals unless otherwise specified.

[0159] As shown in FIG. 18, a first indoor unit 202_1 and a second indoor unit 202_2 are connected to an outdoor unit 201 via a branch unit 203.

[0160] The first indoor unit 202_1 has a first throttle device 21 and an indoor heat exchanger 16. The second indoor unit 202_2 has a first throttle device 21 and an indoor heat exchanger 16.

[0161] The flow dividing unit 203 divides the refrigerant from the outdoor unit 201 into the first indoor unit 202_1 and the second indoor unit 202_2. The flow dividing unit 203 has a fourth throttle device 24, a first on-off valve 40_1 and a second on-off valve 40_2.

[0162] The fourth throttling device 24 is provided on a third refrigerant piping between the first refrigerant piping and the second refrigerant piping. The first refrigerant piping is the refrigerant piping 3 between the first throttling device 21 of the first indoor unit unit 202_1 and the first branch 31 of the second indoor unit unit 202_2. The second refrigerant piping is the refrigerant piping 3 between the indoor heat exchanger 16 of the first indoor unit 202_1 and the indoor heat exchanger 16 of the second indoor unit unit 202_2 and the second branch 32.

[0163] The first on-off valve 40_1 is connected to the indoor heat exchanger 16 of the first indoor unit 202_1 and the third branch 33_1. The third branch 33_1 is provided in the refrigerant pipe 3 between the fourth throttle device 24 and the second branch 32.

[0164] The second on-off valve 40_2 is connected to the indoor heat exchanger 16 of the second indoor unit 202_2 and the third branch 33_2. The third branch 33_2 is provided in the refrigerant pipe 3 between the fourth throttle device 24 and the second branch 32.

[0165] During the defrosting operation, the control device 210 closes the first on-off valve 40_1 and the second on-off valve 40_2 and opens the fourth throttle device 24.

[0166] As a result of the control device 210 performing such control, during defrost operation, the refrigerant coming out of the refrigerant heat exchanger 2 returns to the refrigerant tank 6 and circulates without flowing through the refrigerant flow paths of the first indoor unit 202_1 and the second indoor unit 202_2.

[0167] Therefore, the indoor heat exchangers 16 of the first indoor unit 202_1 and the second indoor unit 202_2 can hold the refrigerant as a refrigerant container, thereby suppressing the inflow of liquid refrigerant into the compressor 14 and improving the quality.

[0168] Furthermore, by providing the first on-off valve 40_1 and the second on-off valve 40_2, the effect of suppressing the outflow of refrigerant from the first indoor unit 202_1 and the second indoor unit 202_2 to the outdoor unit 201 becomes even greater.

[0169] The embodiments are presented as examples and are not intended to limit the scope of the claims. The embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the embodiments. These embodiments and their modifications are included in the scope and spirit of the embodiments. [Explanation of symbols]

[0170] 1 plate, 2 refrigerant heat exchanger, 3 refrigerant piping, 6 refrigerant tank, 11 outdoor heat exchanger, 13 outdoor fan, 14 compressor, 15 flow path switching device, 16 indoor heat exchanger, 21 first throttling device, 22 second throttling device, 23 third throttling device, 24 fourth throttling device, 31 first branch, 31a inlet, 31b first outlet, 31c second outlet, 31o intersection center, 32 second branch, 33_1, 33_2 third branch, 40_1 first on-off valve, 40_2 second on-off valve, 51 high temperature side flow path inlet, 52 high temperature side flow path outlet, 53 low temperature side flow path inlet, 54 low temperature side flow path outlet, 61 liquid-based refrigerant, 62 gas-based refrigerant, 63 refrigerant in a gas-liquid two-phase or liquid phase state, 71 first temperature measurement unit, 72 second temperature measurement unit, 81 First pressure measurement unit, 82 second pressure measurement unit, 91 first unit vector, 92 second unit vector, 93 third unit vector, 100 direction of gravity, 200 air conditioning device, 201 outdoor unit, 202 indoor unit, 202_1 first indoor unit, 202_2 second indoor unit, 203 shunt unit, 210 control device, A main circuit, W bisector.

Claims

1. a main circuit to which a compressor, an outdoor heat exchanger, a first throttling device, an indoor heat exchanger, and a refrigerant tank are connected, and in which, during a defrosting operation, a refrigerant circulates through the compressor, the outdoor heat exchanger, the first throttling device, and the indoor heat exchanger in this order; an intermediate refrigerant heat exchanger provided between the outdoor heat exchanger and the first throttle device, for exchanging heat between a high-pressure refrigerant flowing out of the outdoor heat exchanger during the defrosting operation and a low-pressure refrigerant obtained by reducing the pressure of the high-pressure refrigerant; a second throttle device provided in a refrigerant pipe branched from a first branch provided in a refrigerant pipe between the first throttle device and the refrigerant-to-refrigerant heat exchanger, the second throttle device reducing the pressure of the high-pressure refrigerant flowing through the branched refrigerant pipe to the low-pressure refrigerant; Equipped with The refrigerant heat exchanger includes: a high-temperature side flow path inlet into which the high-pressure refrigerant flowing out from the outdoor heat exchanger flows; a high-temperature side flow passage outlet connected to the first and second throttle devices, through which the high-pressure refrigerant that has flowed into the high-temperature side flow passage inlet flows out; a low-temperature side flow path inlet connected to the second throttle device and into which the low-pressure refrigerant flowing out of the second throttle device flows; a low-temperature side flow path outlet connected to a second branch provided in a refrigerant pipe connecting the indoor heat exchanger and the refrigerant tank during the defrosting operation, through which the low-pressure refrigerant that has flowed into the low-temperature side flow path inlet flows out; Equipped with a first temperature measuring unit provided in a first refrigerant pipe between the high-temperature side flow path outlet and the first throttle device, the first temperature measuring unit measuring a temperature of the refrigerant flowing through the first refrigerant pipe; a first pressure measuring unit provided in the first refrigerant pipe and configured to measure a pressure of the refrigerant flowing through the first refrigerant pipe; a second temperature measurement unit provided in a second refrigerant pipe between the low-temperature side flow path outlet and the second branch, the second temperature measurement unit measuring a temperature of the refrigerant flowing through the second refrigerant pipe; a second pressure measuring unit provided in the second refrigerant pipe and configured to measure the pressure of the refrigerant flowing through the second refrigerant pipe; a control device that controls the opening degrees of the first and second throttle devices based on the temperature measured by the first temperature measuring unit, the pressure measured by the first pressure measuring unit, the temperature measured by the second temperature measuring unit, and the pressure measured by the second pressure measuring unit during the defrosting operation; and Equipped with the absolute value of the difference between the temperature measured by the first temperature measuring unit and the saturation temperature of the pressure measured by the first pressure measuring unit is denoted by SC; The absolute value of the difference between the temperature measured by the second temperature measuring unit and the saturation temperature of the pressure measured by the second pressure measuring unit is SH In this case, The control device The air conditioning apparatus controls the opening degrees of the first and second throttle devices so that 3≦(SC)*(SH)≦80 during the defrosting operation.

2. a main circuit to which a compressor, an outdoor heat exchanger, a plurality of first throttling devices, a plurality of indoor heat exchangers, and a refrigerant tank are connected, and in which, during a defrosting operation, a refrigerant circulates through the compressor, the outdoor heat exchanger, the plurality of first throttling devices, and the plurality of indoor heat exchangers in this order; an intermediate refrigerant heat exchanger provided between the outdoor heat exchanger and the plurality of first throttle devices, for exchanging heat between a high-pressure refrigerant flowing out of the outdoor heat exchanger during the defrosting operation and a low-pressure refrigerant obtained by reducing the pressure of the high-pressure refrigerant; a second throttle device provided in a refrigerant pipe branched from a first branch provided in a refrigerant pipe between the plurality of first throttle devices and the refrigerant-to-refrigerant heat exchanger, the second throttle device reducing the pressure of the high-pressure refrigerant flowing through the branched refrigerant pipe to the low-pressure refrigerant; Equipped with the plurality of indoor heat exchangers include a first indoor heat exchanger and a second indoor heat exchanger; The refrigerant heat exchanger includes: a high-temperature side flow path inlet into which the high-pressure refrigerant flowing out from the outdoor heat exchanger flows; a high-temperature side flow passage outlet connected to the plurality of first throttle devices and the plurality of second throttle devices, through which the high-pressure refrigerant that has flowed into the high-temperature side flow passage inlet flows out; a low-temperature side flow path inlet connected to the second throttle device and into which the low-pressure refrigerant flowing out of the second throttle device flows; a low-temperature side flow path outlet connected to a second branch provided in a refrigerant pipe connecting the plurality of indoor heat exchangers and the refrigerant tank during the defrosting operation, through which the low-pressure refrigerant that has flowed into the low-temperature side flow path inlet flows out; Equipped with a first temperature measurement unit provided in a first refrigerant pipe between the high-temperature side flow path outlet and the plurality of first throttle devices, the first temperature measurement unit measuring a temperature of the refrigerant flowing through the first refrigerant pipe; a first pressure measuring unit provided in the first refrigerant pipe and configured to measure a pressure of the refrigerant flowing through the first refrigerant pipe; a second temperature measurement unit provided in a second refrigerant pipe between the low-temperature side flow path outlet and the second branch, the second temperature measurement unit measuring a temperature of the refrigerant flowing through the second refrigerant pipe; a second pressure measuring unit provided in the second refrigerant pipe and configured to measure the pressure of the refrigerant flowing through the second refrigerant pipe; a control device that controls the opening degrees of the plurality of first throttle devices and the second throttle devices based on the temperature measured by the first temperature measuring unit, the pressure measured by the first pressure measuring unit, the temperature measured by the second temperature measuring unit, and the pressure measured by the second pressure measuring unit during the defrosting operation; an outdoor unit including the compressor, the outdoor heat exchanger, the refrigerant-to-refrigerant heat exchanger, and the second throttling device; a first indoor unit having one of the plurality of first expansion devices and the first indoor heat exchanger connected to the one of the first expansion devices; a second indoor unit having the other of the plurality of first throttling devices and the second indoor heat exchanger connected to the other of the first throttling devices; a flow dividing unit that divides the refrigerant from the outdoor unit into the first indoor unit and the second indoor unit; Equipped with The flow dividing unit comprises: a fourth throttling device provided in the refrigerant piping between the one first throttling device of the first indoor unit and the other first throttling device of the second indoor unit and the first branch, and a fourth throttling device provided in the refrigerant piping between the first indoor heat exchanger of the first indoor unit and the second indoor heat exchanger of the second indoor unit and the second refrigerant piping between the second branch and the first branch; a first on-off valve connected to the first indoor heat exchanger of the first indoor unit and to a third branch provided in the refrigerant piping between the fourth expansion device and the second branch; a second on-off valve connected to the second indoor heat exchanger of the second indoor unit and the third branch provided in the refrigerant piping between the fourth expansion device and the second branch; Equipped with The control device The air conditioner wherein, during the defrosting operation, the first opening / closing valve and the second opening / closing valve are closed and the fourth throttle device is opened.

3. The control device controlling the opening degree of the first throttle device so that the temperature measured by the first temperature measuring unit becomes lower than a saturation temperature of the pressure measured by the first pressure measuring unit; The opening degree of the second throttle device is controlled so that the temperature measured by the second temperature measuring unit becomes higher than the saturation temperature of the pressure measured by the second pressure measuring unit. The air conditioning apparatus according to claim 1 or 2.

4. The control device During the defrosting operation, the opening degree of the first throttle device is controlled so that the degree of subcooling based on the temperature measured by the first temperature measuring unit and the pressure measured by the first pressure measuring unit is 0°C or more and 10°C or less. The air conditioning apparatus according to claim 1 or 2.

5. When a length of a third refrigerant pipe connecting the refrigerant-to-refrigerant heat exchanger and the first throttling device is virtually divided into two equal parts, the first temperature measuring unit is provided on the third refrigerant pipe closer to the first throttling device. The air conditioning apparatus according to claim 1 or 2.

6. The refrigerant heat exchanger includes: a plate-type heat exchanger having a plurality of plates in which the high-pressure refrigerant flow paths and the low-pressure refrigerant flow paths are alternately arranged in a direction horizontal to the direction of gravity, The high-temperature side flow passage inlet and the low-temperature side flow passage outlet are provided above the high-temperature side flow passage outlet and the low-temperature side flow passage inlet. The air conditioning apparatus according to claim 1 or 2.

7. The refrigerant heat exchanger includes: a plate-type heat exchanger having a plurality of plates in which high-pressure refrigerant flow paths and low-pressure refrigerant flow paths are alternately arranged in a direction parallel to the direction of gravity; The high-temperature side flow passage outlet and the low-temperature side flow passage outlet are provided above the high-temperature side flow passage inlet and the low-temperature side flow passage inlet. The air conditioning apparatus according to claim 1 or 2.

8. During the defrosting operation, the refrigerant pipe provided with the first branch an inlet through which the refrigerant flows; a first outlet through which the refrigerant that has flowed into the inlet flows out to the second throttle device; a second outlet through which the refrigerant that has flowed into the inlet flows out to the first throttle device; Equipped with When an intersection of a line segment connecting the centers of the inlets, a line segment connecting the centers of the first outlets, and a line segment connecting the centers of the second outlets is defined as an intersection center, A unit vector of a line segment connecting the center of the intersection point to the center of the inlet is a first unit vector, a unit vector of a line segment connecting the center of the intersection point to the center of the first outlet is defined as a second unit vector; a unit vector of a line segment connecting the center of the intersection point to the center of the second outlet is defined as a third unit vector; The dot product of the first unit vector and the second unit vector is smaller than the dot product of the first unit vector and the third unit vector. The air conditioning apparatus according to claim 1 or 2.

9. The plate type heat exchanger comprises: The length of the flow path stacking direction perpendicular to gravity is defined as X, the length of the flow path stacking direction perpendicular to gravity is defined as Y, and the height direction parallel to gravity is defined as Z, where Z / (XY) is 0.01 or more and 0.1 or less. The air conditioning apparatus according to claim 6.

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