Heat exchanger and refrigeration cycle device equipped with heat exchanger

Abstract

To provide a heat exchanger capable of suppressing frost formation on a lowermost flat porous tube, and a refrigeration cycle device including the heat exchanger.SOLUTION: A first heat exchanger 11 includes: a plurality of flat porous tubes 110 arranged side by side in a vertical direction; and a flow divider 170 as a pressure loss portion. The plurality of flat porous tubes include: flat porous tubes of a first tube group 114; and flat porous tubes of a second tube group 116 excluding the flat porous tubes of the first tube group. The first tube group forms a first path P1. The first path is a flow passage of a refrigerant including a flat porous tube 110L disposed on the lowermost first heat exchanger. The second tube group forms a second path P2 as a flow passage of the refrigerant. When the first heat exchanger is functioned as an evaporator, at least a part of the refrigerant supplied to the first heat exchanger flows into the pressure loss portion after flowing in the first path and flows out from the pressure loss portion to flow into the second path.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a heat exchanger using a flat multi-hole tube and a refrigeration cycle apparatus including the heat exchanger. [Background technology]

[0002] When a heat exchanger using flat multi-hole tubes is used as an evaporator to exchange heat between low-temperature air and a refrigerant, frost formation on the flat multi-hole tubes at the bottom of the heat exchanger is likely to become a problem.

[0003] In order to suppress frost formation on the flat multi-hole tubes in the lowest stage of a heat exchanger, Patent Document 1 (JP 2019-60596 A) aims to suppress frost formation of the refrigerant on the flat multi-hole tubes in the lowest stage by making the path length of the refrigerant path including the flat multi-hole tube in the lowest stage longer than the path lengths of the other refrigerant paths. Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the heat exchanger of Patent Document 1 (JP 2019-60596 A), frost formation on the lowest flat multi-hole tube may not be sufficiently suppressed, and there is room for improvement in terms of suppressing frost formation on the lowest flat multi-hole tube. [Means for solving the problem]

[0005] A heat exchanger according to a first aspect includes a plurality of flat multi-hole tubes and a pressure loss section through which a refrigerant flows. The plurality of flat multi-hole tubes are arranged side by side in the vertical direction. The plurality of flat multi-hole tubes include flat multi-hole tubes of a first tube group including a flat multi-hole tube arranged in the lowest stage of the heat exchanger, and flat multi-hole tubes of a second tube group other than the flat multi-hole tubes of the first tube group. The flat multi-hole tubes of the first tube group form a first path, which is a flow path of the refrigerant. The second tube group forms a second path, which is a flow path of the refrigerant. When the heat exchanger functions as an evaporator, at least a portion of the refrigerant supplied to the heat exchanger flows through the first path, then flows into the pressure loss section, flows out of the pressure loss section, and flows into the second path.

[0006] In the heat exchanger of the first aspect, a pressure loss section is provided downstream of the first pass in the flow direction of the refrigerant when used as an evaporator. Therefore, in the heat exchanger of the first aspect, a large pressure difference between when the refrigerant enters the first pass and when it enters the second pass, in other words, a large temperature difference between when the refrigerant enters the first pass and when it enters the second pass, can be ensured. Therefore, in the heat exchanger of the first aspect, the amount of heat dissipated from the first pass when the heat exchanger functions as an evaporator can be ensured, and frost formation on the first pass can be suppressed.

[0007] A heat exchanger according to a second aspect is the heat exchanger according to the first aspect, wherein when the heat exchanger functions as an evaporator, all of the refrigerant supplied to the heat exchanger flows through the first path and then into the pressure loss section, and then flows through the pressure loss section and then into the second path.

[0008] In the heat exchanger of the second aspect, when the heat exchanger functions as an evaporator, the entire amount of refrigerant flowing into the heat exchanger flows through the first path, so that a large amount of heat can be dissipated from the first path when the heat exchanger functions as an evaporator.

[0009] A heat exchanger according to a third aspect is the heat exchanger according to the first or second aspect, wherein the first tube group includes a plurality of flat multi-hole tubes arranged in parallel.

[0010] In the heat exchanger according to the third aspect, excessive pressure loss in the first pass can be suppressed.

[0011] A heat exchanger according to a fourth aspect is the heat exchanger according to the first or second aspect, wherein the flow path area of each of the flat multi-hole tubes of the first tube group is larger than the flow path area of each of the flat multi-hole tubes of the second tube group.

[0012] In the heat exchanger according to the fourth aspect, excessive pressure loss in the first pass can be suppressed.

[0013] A heat exchanger according to a fifth aspect is the heat exchanger according to any one of the first aspect to the fourth aspect, wherein the number of flat multi-hole tubes included in the first tube group is smaller than the number of flat multi-hole tubes included in the second tube group.

[0014] In the heat exchanger of the fifth aspect, the refrigerant flow rate through each flat multi-hole tube in the first pass can be increased, and the amount of heat dissipated from each flat multi-hole tube in the first pass when the heat exchanger functions as an evaporator can be increased.

[0015] A heat exchanger according to a sixth aspect is the heat exchanger according to any one of the first aspect to the fifth aspect, wherein the pressure loss portion is an orifice arranged in the refrigerant flow path between the first path and the second path.

[0016] In the heat exchanger of the sixth aspect, by providing an orifice at a stage subsequent to the first pass, it is possible to ensure a large pressure difference from when the heat enters the first pass to when it enters the second pass, in other words, a large temperature difference from when the heat enters the first pass to when it enters the second pass. Therefore, in the heat exchanger of the sixth aspect, it is possible to obtain a large amount of heat dissipation from the first pass when the heat exchanger functions as an evaporator, and it is possible to suppress frost formation on the first pass.

[0017] A heat exchanger according to a seventh aspect is the heat exchanger according to any one of the first aspect to the fifth aspect, wherein the pressure loss portion is a flow divider arranged in the refrigerant flow path between the first path and the second path.

[0018] In the heat exchanger of the seventh aspect, a flow divider is used that divides the refrigerant into the flat multi-hole tubes of the second tube bank after passing through the first pass, thereby ensuring a large pressure difference from when the refrigerant enters the first pass to when it enters the second pass, in other words, a large temperature difference from when the refrigerant enters the first pass to when it enters the second pass. Therefore, in the heat exchanger of the first aspect, a large amount of heat can be dissipated from the first pass when the heat exchanger functions as an evaporator, and frost formation on the first pass can be suppressed.

[0019] A heat exchanger according to an eighth aspect is the heat exchanger according to any one of the first to fifth aspects, further comprising a header disposed in a refrigerant flow path between the first path and the second path, and the pressure loss portion is a nozzle disposed inside the header.

[0020] In the heat exchanger of the eighth aspect, by using a nozzle disposed in the header, it is possible to ensure a large pressure difference from when the heat enters the first pass to when it enters the second pass, in other words, a large temperature difference from when the heat enters the first pass to when it enters the second pass. Therefore, in the heat exchanger of the first aspect, it is possible to obtain a large amount of heat dissipation from the first pass when the heat exchanger functions as an evaporator, and it is possible to suppress frost formation on the first pass.

[0021] A heat exchanger according to a ninth aspect is the heat exchanger according to the first aspect, further comprising a bypass passage that guides the refrigerant to the second path without flowing through the first path.

[0022] In the heat exchanger of the ninth aspect, when an extremely large amount of refrigerant is supplied to the heat exchanger, the entire amount of refrigerant flows through the first path, causing excessive pressure loss and reducing the efficiency of the refrigeration cycle device using the heat exchanger.

[0023] A heat exchanger according to a tenth aspect is the heat exchanger according to any one of the first to ninth aspects, wherein the flat multi-hole tubes are arranged in a plurality of rows in the direction of an airflow generated by a blower that sends air to the heat exchanger, and the first path is arranged only on the upwind side in the direction of the airflow.

[0024] In the heat exchanger of the tenth aspect, it is easy to suppress frost formation on the flat multi-hole tubes on the windward side and lower part of the heat exchanger, where frost or ice adhesion is likely to be a problem.

[0025] A refrigeration cycle apparatus according to an eleventh aspect includes a refrigerant circuit and a blower. The refrigerant circuit includes the heat exchanger according to any one of the first to tenth aspects as a heat source heat exchanger, and a compressor that compresses the refrigerant. The blower sends air to the heat exchanger.

[0026] In the refrigeration cycle apparatus of the eleventh aspect, since frost formation on the flat multi-hole tubes of the first tube group of the heat exchanger can be suppressed, the time during which the operation of the heat exchanger functioning as an evaporator is interrupted can be shortened. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a schematic configuration diagram of an air conditioning apparatus according to an embodiment of a refrigeration cycle device of the present disclosure. [Figure 2] 2 is a schematic plan view of the interior of the heat source unit of the air conditioner of FIG. 1, for illustrating the arrangement of a first heat exchanger in the heat source unit. FIG. [Figure 3] 3 is a schematic perspective view of a heat exchanger according to a first embodiment of the present disclosure, which is used in the air conditioning apparatus of FIG. 2. FIG. [Figure 4] FIG. 4 is a partially enlarged perspective view of a local portion of the first heat exchanger of FIG. 3. [Figure 5] FIG. 4 is a diagram schematically illustrating the structure of the first heat exchanger of FIG. 3 and the flow of refrigerant in the first heat exchanger when it functions as an evaporator. [Figure 6] 4 is a diagram schematically showing the flow of refrigerant in a first pass of the first heat exchanger of FIG. 3 when the first heat exchanger functions as an evaporator. FIG. [Figure 7] FIG. 10 is a diagram schematically illustrating the structure of a first heat exchanger according to another example, and also schematically illustrating the flow of refrigerant in the first heat exchanger when it functions as an evaporator. [Figure 8A] FIG. 1 is a diagram for explaining the difference between the flow of refrigerant in the heat exchanger of the present disclosure and the flow of refrigerant in a conventional heat exchanger, and is a diagram conceptually showing the flow of refrigerant in the heat exchanger of the present disclosure. [Figure 8B] FIG. 1 is a diagram for explaining the difference between the flow of refrigerant in the heat exchanger of the present disclosure and the flow of refrigerant in a conventional heat exchanger, and is a diagram conceptually showing the flow of refrigerant in a conventional heat exchanger. [Figure 9] 1 is a diagram schematically illustrating a Mollier diagram when an air conditioning apparatus according to an embodiment of the refrigeration cycle device of the present disclosure performs heating operation. FIG. [Figure 10] 10 is a diagram conceptually showing the flow of refrigerant in a first path of a heat exchange section of a first heat exchanger according to Modification A. FIG. [Figure 11] 10 is a schematic cross-sectional view of a first heat exchanger according to Modification C, taken along an imaginary plane perpendicular to the direction in which the flat multi-hole tubes extend. FIG. [Figure 12]10 is a diagram illustrating the internal structure of a part of the first header of the first heat exchanger according to Modification D. FIG. [Figure 13] 10 is a diagram conceptually showing the flow of refrigerant in a heat exchanger according to Modification E. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A heat exchanger according to an embodiment of the present disclosure and a refrigeration cycle apparatus having the heat exchanger will be described with reference to the drawings.

[0029] (1) Overall structure An overview of the refrigeration cycle device of the present disclosure will be described with reference to Fig. 1. Fig. 1 is a schematic configuration diagram of an air conditioner 1 according to one embodiment of the refrigeration cycle device of the present disclosure.

[0030] The air conditioner 1 is an apparatus that can cool and heat a space to be air-conditioned by performing a vapor compression refrigeration cycle. Note that the type of refrigeration cycle apparatus of the present disclosure is not limited to an air conditioner, and may be, for example, a water heater or the like.

[0031] 1, the air conditioner 1 mainly comprises a heat source unit 2, utilization units 3a and 3b, a liquid refrigerant connection pipe 4, a gas refrigerant connection pipe 5, and a control unit 23. The control unit 23 controls the operation of the components of the heat source unit 2 and utilization units 3a and 3b.

[0032] The liquid refrigerant communication pipe 4 and the gas refrigerant communication pipe 5 connect the heat source unit 2 and the utilization units 3a, 3b. In the air conditioner 1, the heat source unit 2 and the utilization units 3a, 3b are connected via the refrigerant communication pipes 4, 5 to form a refrigerant circuit 6 (see FIG. 1). In the refrigerant circuit 6, a compressor 8, a flow direction switching mechanism 10, a first heat exchanger 11, a first expansion mechanism 12, a first shut-off valve 13, a second shut-off valve 14, second expansion mechanisms 31a, 31b, and second heat exchangers 32a, 32a (described later) are connected by refrigerant piping as shown in FIG. 1.

[0033] For example, R32, an HFC refrigerant, is enclosed as a refrigerant in the refrigerant circuit 6. However, the type of refrigerant is not limited to R32, and the refrigerant may be, for example, R410A, R1234yf, R1234ze(E), R290, CO2, etc.

[0034] 1, the air conditioning apparatus 1 has one heat source unit 2 and two utilization units 3a and 3b, but this number is merely an example. The air conditioning apparatus 1 may have multiple heat source units, or one or three or more utilization units.

[0035] (2) Detailed configuration The heat source unit 2, utilization units 3a and 3b, liquid refrigerant communication pipe 4 and gas refrigerant communication pipe 5, and control unit 23 of the air conditioner 1 will be described below.

[0036] (2-1) Heat source unit The heat source unit 2 is installed outdoors, for example, on the roof of the building in which the air conditioner 1 is installed, or around the exterior wall of the building, although this is not a limitation.

[0037] The heat source unit 2 of this embodiment is a side-blowing type unit (see FIG. 2) that takes in air to be heat exchanged with the refrigerant from the side (rear and left side) of a housing 2a (see FIG. 2) that houses various devices of the heat source unit 2, and blows out the air that has exchanged heat with the refrigerant from the side (front) of the housing 2a. However, the type of heat source unit 2 is not limited to the side-blowing type, and it may be an up-blowing type unit that takes in air to be heat exchanged with the refrigerant from the side of the housing 2a and blows out the air that has exchanged heat with the refrigerant upward from the top of the housing 2a.

[0038] The heat source unit 2 mainly has an accumulator 7, a compressor 8, a flow direction switching mechanism 10, a first heat exchanger 11, a first expansion mechanism 12, a first shut-off valve 13, a second shut-off valve 14, and a first fan 15 (see Figure 1).

[0039] The heat source unit 2 also has a suction pipe 17, a discharge pipe 18, a first gas refrigerant pipe 19, a liquid refrigerant pipe 20, and a second gas refrigerant pipe 21 (see FIG. 1). The suction pipe 17 connects the flow direction switching mechanism 10 and the suction side of the compressor 8. The accumulator 7 is provided on the suction pipe 17. The discharge pipe 18 connects the discharge side of the compressor 8 and the flow direction switching mechanism 10. The first gas refrigerant pipe 19 connects the flow direction switching mechanism 10 and the gas end of the first heat exchanger 11. The liquid refrigerant pipe 20 connects the liquid end of the first heat exchanger 11 and the first shut-off valve 13. The first expansion mechanism 12 is provided on the liquid refrigerant pipe 20. The second gas refrigerant pipe 21 connects the flow direction switching mechanism 10 and the second shut-off valve 14.

[0040] (2-1-1) Compressor Compressor 8 is a device that draws in low-pressure refrigerant in the refrigeration cycle that flows in through suction pipe 17, compresses it to raise the pressure to the high pressure in the refrigeration cycle, and discharges the high-pressure refrigerant in the refrigeration cycle to discharge pipe 18. Compressor 8 has a motor (not shown) that is inverter-controlled. The rotation speed of the motor of compressor 8 is adjusted by control unit 23 depending on the operating conditions. Note that compressor 8 may also be a compressor with a constant motor rotation speed.

[0041] (2-1-2) Flow direction switching mechanism The flow direction switching mechanism 10 switches the flow direction of the refrigerant in the refrigerant circuit 6 depending on the instructed operation mode or at the timing of defrosting during heating operation. In this embodiment, the flow direction switching mechanism 10 is a four-way switching valve.

[0042] During cooling operation (including dehumidification operation) and defrost operation, the flow direction switching mechanism 10 connects the suction pipe 17 with the second gas refrigerant pipe 21 and the discharge pipe 18 with the first gas refrigerant pipe 19 (this piping connection state by the flow direction switching mechanism 10 is called the first state), thereby switching the flow direction of the refrigerant in the refrigerant circuit 6 so that the refrigerant discharged from the compressor 8 is sent to the first heat exchanger 11 (see solid line in Figure 1).

[0043] During heating operation, the flow direction switching mechanism 10 connects the suction pipe 17 to the first gas refrigerant pipe 19 and the discharge pipe 18 to the second gas refrigerant pipe 21 (this piping connection state by the flow direction switching mechanism 10 is called the second state), thereby switching the flow direction of the refrigerant in the refrigerant circuit 6 so that the refrigerant discharged from the compressor 8 is sent to the second heat exchangers 32a, 32b (see dashed lines in Figure 1).

[0044] The flow direction switching mechanism 10 is not limited to a four-way switching valve, but may be configured to combine a plurality of electromagnetic valves and refrigerant pipes to achieve the switching of the refrigerant flow direction as described above.

[0045] (2-1-3) 1st heat exchanger The first heat exchanger 11 is a heat exchanger that functions as a radiator (condenser) during cooling / defrosting operation and as an evaporator (heat absorber) during heating operation. The first heat exchanger 11 is an example of a heat exchanger defined in the claims.

[0046] The structure of the first heat exchanger 11 and the flow of the refrigerant in the first heat exchanger 11 will be described later.

[0047] (2-1-4) First expansion mechanism The first expansion mechanism 12 is a mechanism for expanding the refrigerant flowing between the second heat exchangers 32a, 32b of the utilization units 3a, 3b and the first heat exchanger 11 in the refrigerant circuit 6. The first expansion mechanism 12 is, for example, an electronic expansion valve with an adjustable opening. The opening of the first expansion mechanism 12 is adjusted by the control unit 23 depending on the operating conditions.

[0048] (2-1-5) First Fan The first fan 15 generates an airflow and supplies the air to the first heat exchanger 11. The first fan 15 generates a flow of air that flows from outside the housing 2a into the heat source unit 2, passes through the first heat exchanger 11, and flows out of the housing 2a. The first fan 15 is, for example, a propeller fan. However, the type of the first fan 15 is not limited to a propeller fan, and other types of fans may be used.

[0049] (2-2) Usage unit The utilization units 3a and 3b are installed in the space to be air-conditioned or in the vicinity of the space to be air-conditioned (for example, in the attic space of the space to be air-conditioned).

[0050] The utilization unit 3a mainly includes a second expansion mechanism 31a, a second heat exchanger 32a, and a second fan 33a (see FIG. 1). The utilization unit 3b mainly includes a second expansion mechanism 31b, a second heat exchanger 32b, and a second fan 33b (see FIG. 1).

[0051] (2-2-1) Second expansion mechanism The second expansion mechanisms 31a, 31b are mechanisms for expanding the refrigerant flowing between the second heat exchangers 32a, 32b of the utilization units 3a, 3b and the first heat exchanger 11 in the refrigerant circuit 6. The second expansion mechanisms 31a, 31b are, for example, electronic expansion valves with adjustable opening. The openings of the second expansion mechanisms 31a, 31b are adjusted by the control unit 23 depending on the operating conditions.

[0052] (2-2-2)Second heat exchanger The second heat exchangers 32a and 32b are heat exchangers that function as heat absorbers (evaporators) during cooling operation to cool the indoor air, and function as refrigerant radiators (condensers) to heat the indoor air during heating operation.

[0053] The liquid sides of the second heat exchangers 32a, 32b are connected via refrigerant piping to a liquid refrigerant connection pipe 4, and the gas sides of the second heat exchangers 32a, 32b are connected via refrigerant piping to a gas refrigerant connection pipe 5. The second heat exchangers 32a, 32b are, for example, cross-fin fin-and-tube heat exchangers having a plurality of heat transfer tubes (not shown) and a plurality of fins (not shown).

[0054] (2-2-3) Second Fan The second fans 33a, 33b generate a flow of air that flows from the outside (space to be air-conditioned) of a housing (not shown) that houses various devices of the utilization units 3a, 3b inside, into the utilization units 3a, 3b, passes through the second heat exchangers 32a, 32b, and flows out of the housing (space to be air-conditioned). The second fans 33a, 33b are, for example, centrifugal fans.

[0055] (2-3) Refrigerant connection pipe The refrigerant connection pipes 4, 5 are refrigerant piping that is installed on-site when installing the air conditioner 1. One end of the liquid refrigerant connection pipe 4 is connected to the first shut-off valve 13 of the heat source unit 2, and the other end of the liquid refrigerant connection pipe 4 is connected to refrigerant piping that is connected to the liquid sides of the second heat exchangers 32a, 32b of the utilization units 3a, 3b (see Figure 1). One end of the gas refrigerant connection pipe 5 is connected to the second shut-off valve 14 of the heat source unit 2, and the other end of the gas refrigerant connection pipe 5 is connected to refrigerant piping that is connected to the gas sides of the second heat exchangers 32a, 32b of the utilization units 3a, 3b (see Figure 1).

[0056] (2-4) Control unit The control unit 23 is configured by communicatively connecting a control board (not shown) having a CPU, ROM, RAM, etc., which is provided in the heat source unit 2 and the utilization units 3a and 3b. For convenience, the control unit 23 is shown in Fig. 1 as being located apart from the heat source unit 2 and the utilization units 3a and 3b.

[0057] 1, the control unit 23 is electrically connected to the components of the air conditioner 1. Specifically, the control unit 23 is electrically connected to, for example, the compressor 8, the flow direction switching mechanism 10, the first expansion mechanism 12, the first fan 15, the second expansion mechanisms 31a and 31b, and the second fans 33a and 33b. The control unit 23 is also electrically connected to various sensors (not shown) that are provided in the heat source unit 2 and the utilization units 3a and 3b.

[0058] The control unit 23 controls the equipment that makes up the air conditioning unit 1 by executing a program for controlling the air conditioning unit 1 (the CPU executes a program stored in the ROM) based on operations from a remote control (not shown) and measurement values of various sensors (not shown).

[0059] The control unit 23 controls the components of the air conditioner 1 to cause the air conditioner 1 to perform cooling operation (including dehumidification operation) or heating operation. Furthermore, when a predetermined condition is met during heating operation of the air conditioner 1, the control unit 23 switches the operation of the air conditioner 1 to defrost operation. The behavior of the air conditioner 1 during each operation is described below.

[0060] (3) Operation of air conditioning equipment We will now explain the cooling operation (including dehumidification operation), heating operation, and defrost operation of the air conditioner 1. The defrost operation is an operation that is performed by temporarily interrupting the heating operation during heating operation, in order to melt frost and ice that has adhered to the first heat exchanger 11.

[0061] During cooling operation, the refrigerant circulates through the refrigerant circuit 6 via the compressor 8, the first heat exchanger 11, the first expansion mechanism 12, the second expansion mechanisms 31a and 31b, the second heat exchangers 32a and 32b, and the accumulator 7 in this order.

[0062] During heating operation, the refrigerant circulates through the refrigerant circuit 6 in the order of the compressor 8, the second heat exchangers 32a and 32b, the second expansion mechanisms 31a and 31b, the first expansion mechanism 12, the first heat exchanger 11, and the accumulator 7.

[0063] During defrosting operation, similar to cooling operation, the refrigerant circulates through the refrigerant circuit 6 in the following order: compressor 8, first heat exchanger 11, first expansion mechanism 12, second expansion mechanisms 31a and 31b, second heat exchangers 32a and 32b, and accumulator 7. In other words, in the air conditioning apparatus 1 of this embodiment, the refrigerant is caused to flow through the refrigerant circuit 6 in the opposite direction to that during heating operation, thereby melting frost and ice that has adhered to the first heat exchanger 11.

[0064] The operation of the air conditioner 1 during cooling operation will be described.

[0065] During cooling operation, the flow direction switching mechanism 10 switches the piping connection state to the first state described above. Then, low-pressure gas refrigerant in the refrigeration cycle (hereinafter simply referred to as low pressure) drawn into the compressor 8 from the suction pipe 17 is compressed by the compressor 8 to high-pressure gas refrigerant in the refrigeration cycle (hereinafter simply referred to as high pressure), and then discharged to the discharge pipe 18. The high-pressure gas refrigerant discharged to the discharge pipe 18 passes through the flow direction switching mechanism 10 and is sent to the first heat exchanger 11. The high-pressure gas refrigerant sent to the first heat exchanger 11 exchanges heat with air supplied by the first fan 15 in the first heat exchanger 11, which functions as a refrigerant radiator, to release heat and become high-pressure liquid refrigerant. The high-pressure liquid refrigerant that has released heat in the first heat exchanger 11 passes through the first expansion mechanism 12, the first shut-off valve 13, and the liquid refrigerant connection pipe 4 and is sent to the second expansion mechanisms 31a and 31b. The refrigerant sent to the second expansion mechanisms 31a, 31b is decompressed to low pressure by the second expansion mechanisms 31a, 31b, becoming a low-pressure, two-phase gas-liquid refrigerant. The low-pressure, two-phase gas-liquid refrigerant decompressed by the second expansion mechanisms 31a, 31b is sent to the second heat exchangers 32a, 32b. The low-pressure, two-phase gas-liquid refrigerant sent to the second heat exchangers 32a, 32b exchanges heat with air supplied by the second fans 33a, 33b in the second heat exchangers 32a, 32b, and evaporates. The air cooled in the second heat exchangers 32a, 32b is blown into the space to be air-conditioned. The low-pressure gas refrigerant evaporated in the second heat exchangers 32a, 32b passes through the gas refrigerant connecting pipe 5, the second shut-off valve 14, the flow direction switching mechanism 10, and the accumulator 7, and is again drawn into the compressor 8.

[0066] During cooling operation, the control unit 23 performs the following control, for example: Note that the control mode by the control unit 23 described here is an example, and is not limited to this.

[0067] The control unit 23 controls the aperture of an electronic expansion valve (an example of an electronic expansion mechanism) of each of the second expansion mechanisms 31 a and 31 b based on a measurement value of a sensor (not shown) so that the degree of superheat of the refrigerant at the outlet of each of the second heat exchangers 32 a and 32 b becomes a target degree of superheat. The control unit 23 also controls the operating capacity of the compressor 8 so that the evaporation temperature approaches the target evaporation temperature.

[0068] The operation of the air conditioner 1 during heating operation will be described.

[0069] During heating operation, the flow direction switching mechanism 10 switches the piping connection state to the second state described above. Low-pressure gas refrigerant sucked into the compressor 8 from the suction pipe 17 is compressed to high pressure in the compressor 8 and then discharged to the discharge pipe 18. The high-pressure gas refrigerant discharged to the discharge pipe 18 is sent to the second heat exchangers 32a, 32b through the flow direction switching mechanism 10, the second shut-off valve 14, and the gas refrigerant communication pipe 5. The high-pressure gas refrigerant sent to the second heat exchangers 32a, 32b exchanges heat with air supplied by the second fans 33a, 33b in the second heat exchangers 32a, 32b, dissipating heat and becoming high-pressure liquid refrigerant or gas-liquid two-phase refrigerant. The air heated by heat exchange with the refrigerant in the second heat exchangers 32a, 32b is blown into the space to be air-conditioned. The high-pressure refrigerant that has dissipated heat in the second heat exchangers 32a, 32b is sent to the first expansion mechanism 12 through the second expansion mechanisms 31a, 31b, the liquid refrigerant connection pipe 4, and the first shut-off valve 13. The refrigerant sent to the first expansion mechanism 12 is decompressed by the first expansion mechanism 12 to become a low-pressure two-phase gas-liquid refrigerant. The low-pressure two-phase gas-liquid refrigerant decompressed by the first expansion mechanism 12 is sent to the first heat exchanger 11. The low-pressure two-phase gas-liquid refrigerant sent to the first heat exchanger 11 exchanges heat with air supplied by the first fan 15 in the first heat exchanger 11, which functions as a refrigerant evaporator, and evaporates to become a low-pressure gas refrigerant. The low-pressure refrigerant evaporated in the first heat exchanger 11 passes through the flow direction switching mechanism 10 and the accumulator 7, and is again drawn into the compressor 8.

[0070] During heating operation, the control unit 23 performs the following control, for example: Note that the control mode by the control unit 23 described here is an example, and the present invention is not limited to this.

[0071] Based on the measurement value of a sensor (not shown), the control unit 23 controls the opening degree of an electronic expansion valve as an example of the first expansion mechanism 12 so that the degree of superheat of the refrigerant at the outlet of the first heat exchanger 11 becomes a target degree of superheat. The control unit 23 also controls the operating capacity of the compressor 8 so that the evaporation temperature approaches the target evaporation temperature.

[0072] When a condition for starting a defrost operation is met during heating operation, the control unit 23 switches the operation of the air conditioner 1 from heating operation to defrost operation. Although not limited to this, the condition for starting a defrost operation is, for example, that the temperature of the refrigerant flowing through the first heat exchanger 11 is lower than a predetermined temperature, or that the continuous time of heating operation exceeds a predetermined time.

[0073] In the defrosting operation, as in the cooling operation, the flow direction switching mechanism 10 switches the connection state of the piping to the first state described above, and the first heat exchanger 11 functions as a radiator of the refrigerant. Explanation of how the refrigerant flows through the air conditioner 1 during the defrosting operation will be omitted.

[0074] The control unit 23 carries out the defrost operation until a defrost operation termination condition is met (until a predetermined defrost time has elapsed or until it is determined that defrosting of the first heat exchanger 11 has been completed based on measurement values from various sensors provided in the air conditioner 1). Specifically, the control unit 23 determines that defrosting of the first heat exchanger 11 has been completed when, for example, a state in which a measurement value from a temperature sensor (not shown) provided in the first gas refrigerant pipe 19 remains higher than a predetermined temperature for a predetermined time. When the defrost operation termination condition is met, the control unit 23 ends the defrost operation and restarts the heating operation of the air conditioner 1.

[0075] (4)First heat exchanger The shape, structure, etc. of the first heat exchanger 11 will be described with further reference to FIGS.

[0076] FIG. 2 is a schematic plan view of the heat source unit 2 to explain the arrangement of the first heat exchanger 11 in the heat source unit 2. FIG. 3 is a schematic perspective view of the first heat exchanger 11. FIG. 4 is a locally enlarged perspective view of the first heat exchanger 11. FIG. 5 is a diagram showing the structure of the first heat exchanger 11 and also showing a schematic view of the flow of refrigerant in the first heat exchanger 11 when the first heat exchanger 11 functions as an evaporator. FIG. 6 is a diagram showing a schematic view of the flow of refrigerant in the first pass P1 of the first heat exchanger 11 when the first heat exchanger 11 functions as an evaporator. FIG. 6 is a diagram depicting an end face of a flat multi-hole tube 110 of a first tube group 114 of the first heat exchanger 11 described later, on the side of a first header 150 described later.

[0077] 5 is a diagram that schematically illustrates the structure of the first heat exchanger 11. For example, the first heat exchanger 11 has an L-shape as shown in FIG. 3, but is illustrated as a straight line (I-shape) in FIG. 5. Furthermore, for example, the number of flat multi-hole tubes 110 (shown by dashed lines) depicted in the first heat exchanger 11 does not represent the number of flat multi-hole tubes 110 that the first heat exchanger 11 actually has.

[0078] In the following description, for convenience, expressions such as "left," "right," "front," "rear," "front face," and "rear face" may be used to explain directions and positional relationships, but the directions indicated by these expressions follow the directions of the arrows shown in the drawings unless otherwise specified.

[0079] As described above, the heat source unit 2 has a housing 2a, which houses the accumulator 7, compressor 8, flow direction switching mechanism 10, first heat exchanger 11, first expansion mechanism 12, first shut-off valve 13, second shut-off valve 14, and first fan 15 inside. The interior of the housing 2a is partitioned into a machine room R1 in which the compressor 8, accumulator 7, flow direction switching mechanism 10, first expansion mechanism 12, first shut-off valve 13, and second shut-off valve 14 are mainly arranged, and a blower room R2 in which the first heat exchanger 11 and first fan 15 are mainly arranged (see FIG. 2). Note that in FIG. 2, the equipment arranged in the machine room R1 is not shown.

[0080] In this embodiment, the first heat exchanger 11 has a substantially L-shape as shown in Figures 2 and 3. In a plan view, as shown in Figure 2, the first heat exchanger 11 extends from the rear right side of the housing 2a (near the machine room R1) along the back surface of the housing 2a to near the rear left end of the housing 2a, changes direction near the rear left end of the housing 2a, and extends to near the front left end.

[0081] A first fan 15 is disposed in front of the first heat exchanger 11. When the first fan 15 is operated, air is sucked in from the rear and left side surface of the housing 2a and passes through the first heat exchanger 11 (see the arrows in FIG. 2). The air that has passed through the first heat exchanger 11 is finally blown out forward from the front surface of the housing 2a (see the arrows in FIG. 2).

[0082] As shown in FIGS. 3 and 5, the first heat exchanger 11 mainly includes a heat exchange section 100, a first header 150, a second header 160, a flow divider 170, a first pipe 180, and a second pipe 190.

[0083] Although not limited to, the heat exchange section 100, the first header 150, the second header 160, the flow divider 170, the first pipe 180, and the second pipe 190 of the first heat exchanger 11 are made of aluminum or an aluminum alloy. The heat exchange section 100, the first header 150, the second header 160, the flow divider 170, the first pipe 180, and the second pipe 190 are joined to each other by brazing or the like.

[0084] (4-1) Configuration of the first heat exchanger Various components of the first heat exchanger 11 will be described.

[0085] (4-1-1) Heat exchange section The heat exchange section 100 is a main part of the first heat exchanger 11. Heat exchange between the refrigerant and the air is mainly performed in the heat exchange section 100. The heat exchange section 100 has a plurality of flat multi-hole tubes 110 arranged in a vertical direction, and a plurality of fins 120 attached to the flat multi-hole tubes 110. In this embodiment, 73 flat multi-hole tubes 110 are arranged in a vertical direction in the heat exchange section 100. However, the number of flat multi-hole tubes 110 in the heat exchange section 100 is merely an example and may be changed as appropriate.

[0086] 4, in the first heat exchanger 11, two rows of heat exchange sections 100 are arranged in the direction of the airflow (airflow direction A) generated by the first fan 15. In other words, in the first heat exchanger 11 of this embodiment, a plurality of rows of flat multi-hole tubes 110 are arranged in the airflow direction A.

[0087] In the following, of the two rows of heat exchange sections 100, the heat exchange section 100 arranged on the upstream side may be referred to as heat exchange section 100u, and the heat exchange section 100 arranged on the downstream side may be referred to as heat exchange section 100d (see FIG. 4). However, when there is no particular need to distinguish between the two, such as when explaining content common to the heat exchange sections 100u and 100d, they may be simply referred to as heat exchange section 100.

[0088] The airflow direction A here refers to the direction of airflow passing through the heat exchanger 100 when the heat exchanger 100 is viewed along the vertical direction in which the flat multi-hole tubes 110 of the heat exchanger 100 are arranged. In other words, the airflow direction A here refers to the flow direction of air passing through the heat exchanger 100 when the heat exchanger 100 is viewed from above (in a plan view).

[0089] In the first heat exchanger 11 of this embodiment, two rows of heat exchange sections 100 are arranged in the airflow direction A, but the first heat exchanger 11 may have only one row of heat exchange sections 100. Also, the first heat exchanger 11 may have three or more rows of heat exchange sections 100 in the airflow direction A.

[0090] As shown in Fig. 6, the flat multi-hole tube 110 is a heat transfer tube having a flat shape (in the cross section of the heat transfer tube, the thickness (height in the vertical direction) is thin compared to the width). As shown in Figs. 4 and 6, each flat multi-hole tube 110 has a plurality of holes 112 formed therein that extend parallel to one another along the extension direction of the flat multi-hole tube 110. The holes 112 of each flat multi-hole tube 110 function as a flow path for the refrigerant.

[0091] Each flat multi-hole pipe 110 of each heat exchange section 100 has a substantially L-shape corresponding to the shape of the first heat exchanger 11. One end of each flat multi-hole pipe 110 is connected to the first header 150, and the other end of each flat multi-hole pipe 110 is connected to the second header 160. Specifically, in a plan view, each flat multi-hole pipe 110 extends from the first header 150, which is disposed near the machine room R1 on the rear right side of the housing 2a, along the back surface of the housing 2a to near the rear left end, changes direction near the rear left end of the housing 2a, and extends to the second header 160, which is disposed near the front left end of the housing 2a.

[0092] The shape of the flat multi-hole pipe 110 (in other words, the shape of the first heat exchanger 11) is not limited to an L-shape. Depending on the type of the heat source unit 2, the required performance, etc., the shape of the flat multi-hole pipe 110 may be a straight shape (I-shape), a U-shape, a rectangular shape, or any other shape other than an L-shape.

[0093] The flat multi-hole tubes 110 in each heat exchange section 100 are divided into two groups (a first tube group 114 and a second tube group 116). In other words, the plurality of flat multi-hole tubes 110 includes the flat multi-hole tubes 110 in the first tube group 114 and the flat multi-hole tubes 110 in the second tube group 116. In the heat exchange section 100, the flat multi-hole tubes 110 in the second tube group 116 mainly contribute to heat exchange between the refrigerant and the air.

[0094] The first tube group 114 includes one or more flat multi-hole tubes 110. The flat multi-hole tubes 110 of the first tube group 114 include a flat multi-hole tube 110 arranged at the lowest stage of the first heat exchanger 11 (arranged at the lowest stage of each heat exchange section 100). Here, the flat multi-hole tube 110 arranged at the lowest stage of the first heat exchanger 11 is denoted by the symbol "110L" (see FIGS. 5 and 6).

[0095] In this embodiment, the first tube group 114 includes the flat multi-hole tube 110L arranged in the lowest row of each of the heat exchange sections 100u, 100d and the flat multi-hole tube 110 arranged in the second row from the bottom. However, depending on the design, the first tube group 114 may include only the flat multi-hole tube 110L arranged in the lowest row of each of the heat exchange sections 100u, 100d, or may include flat multi-hole tubes 110 arranged in not only the lowest row and the second row from the bottom, but also the third row or higher from the bottom of each of the heat exchange sections 100u, 100d.

[0096] The second tube group 116 includes flat multi-hole tubes 110 other than the flat multi-hole tubes 110 of the first tube group 114. In particular, in the present embodiment, all of the flat multi-hole tubes 110 other than the flat multi-hole tubes 110 of the first tube group 114 belong to the second tube group 116. It is preferable that the number of flat multi-hole tubes 110 included in the first tube group 114 is smaller than the number of flat multi-hole tubes 110 included in the second tube group 116. For example, in this embodiment, the number of flat multi-hole tubes 110 included in the first tube group 114 is four (two tubes x two rows), and the number of flat multi-hole tubes 110 included in the second tube group 116 is 142 (71 tubes x two rows). Preferably, the number of flat multi-hole tubes 110 included in the first tube group 114 is 10% or less, more preferably 5% or less, of the total number of flat multi-hole tubes 110 included in the first heat exchanger 11.

[0097] The flat multi-hole tubes 110 of the first tube group 114 form a first path P1, which is a flow path for the refrigerant. The flat multi-hole tubes 110 of the second tube group 116 form a second path P2, which is a flow path for the refrigerant.

[0098] When the first heat exchanger 11 functions as a radiator and an evaporator, the refrigerant flows through the first heat exchanger 11 as follows.

[0099] When the first heat exchanger 11 functions as an evaporator, the refrigerant flows through the first path P1, then flows into the flow divider 170, which is an example of a pressure loss section, and then flows into the second path P2 after flowing through the flow divider 170. In particular, in this embodiment, when the first heat exchanger 11 functions as an evaporator, the entire amount of refrigerant supplied to the first heat exchanger 11 flows through the first path P1, then flows into the flow divider 170, and then flows into the second path P2 after flowing through the flow divider 170. Details of how the refrigerant flows through the first heat exchanger 11 when the first heat exchanger 11 functions as an evaporator will be described later.

[0100] When the first heat exchanger 11 functions as a radiator, the refrigerant flows through the first heat exchanger 11 in the opposite direction to when the first heat exchanger 11 functions as an evaporator. In other words, when the first heat exchanger 11 functions as a radiator, the refrigerant flows through the second path P2 and then flows into the flow divider 170, and then flows through the flow divider 170 and then flows into the first path P1. In particular, in this embodiment, when the first heat exchanger 11 functions as a radiator, the entire amount of refrigerant supplied to the first heat exchanger 11 flows through the second path P2 and then flows into the flow divider 170, and then flows through the flow divider 170 and then flows into the first path P1. Details of how the refrigerant flows through the first heat exchanger 11 when the first heat exchanger 11 functions as a radiator will be described later.

[0101] The fins 120 divide the space between adjacent flat multi-hole tubes 110 in the vertical direction (the direction in which the flat multi-hole tubes 110 are arranged) into multiple ventilation passages through which air flows. The fins 120 are formed with multiple horizontally elongated notches 122 so that multiple flat multi-hole tubes 110 can be inserted (see FIG. 4). The direction in which the notches 122 extend substantially coincides with the airflow direction A generated by the first fan 15. The notches 122 open on the downwind side so that the flat multi-hole tubes 110 can be inserted from the downwind side to the upwind side in the ventilation direction. The notches 122 of the fins 120 are formed at predetermined intervals in the vertical direction.

[0102] (4-1-2) First Header The first header 150 is a vertically long, hollow, cylindrical member whose upper and lower ends are closed. One first header 150 is provided for each of the two rows of heat exchange sections 100. However, the first header 150 may be a single cylindrical member shared by the two rows of heat exchange sections 100, and the interior may be divided into spaces corresponding to each of the two rows of heat exchange sections 100.

[0103] The two first headers 150 are installed in an upright position near the machine room R1 on the rear right side of the housing 2a (see FIG. 2). To each first header 150, one end of each of the flat multi-hole pipes 110 of the corresponding heat exchanger 100 is connected.

[0104] Although the internal structure is not limited to this, in the first heat exchanger 11 of this embodiment, the interior of each first header 150 is vertically partitioned into four independent spaces 152a to 152d. Inside the first header 150, spaces 152a, 152b, 152c, and 152d are arranged in this order from bottom to top.

[0105] As shown in Fig. 5, one end of a first pipe 180 is connected to the lowest space 152a, and the first pipe 180 is in communication with the first pipe 180. As shown in Fig. 5, a liquid refrigerant pipe 20 is connected to the other end of the first pipe 180 (the end opposite to the end connected to the space 152a of the first header 150). Also, as shown in Fig. 5, one end of the lowest flat multi-hole pipe 110L of the heat exchange section 100 corresponding to that first header 150 is connected to the space 152a of each first header 150, and the space 152a and the lowest flat multi-hole pipe 110L of the heat exchange section 100 are in communication with each other.

[0106] 5, the space 152b communicates with a pipe (main pipe) 174 of the flow divider 170, and communicates with a main body 172 of the flow divider 170 via the pipe 174. Furthermore, one end of the second-lowest flat multi-hole pipe 110 (the flat multi-hole pipe 110 of the first pipe group 114) of the heat exchange section 100 corresponding to that first header 150 is connected to the space 152b of each first header 150, and the space 152b and the second-lowest flat multi-hole pipe 110 of the heat exchange section 100 communicate with each other.

[0107] 5, the space 152c communicates with the pipe (capillary) 176 of the flow divider 170, and communicates with the main body 172 of the flow divider 170 via the pipe 176. Furthermore, to the space 152c of each first header 150, for example, one end of the flat multi-hole pipes 110 in the third to fourteenth rows from the bottom of the heat exchange section 100 corresponding to that first header 150 is connected, and the space 152c communicates with the flat multi-hole pipes 110 in the third to fourteenth rows from the bottom of the heat exchange section 100.

[0108] As shown in Fig. 5, one end of second piping 190 is connected to the uppermost space 152d, and the space 152d is in communication with the second piping 190. The other end of the second piping 190 (the end opposite to the end connected to the space 152d of the first header 150) is connected to the first gas refrigerant pipe 19, as shown in Fig. 5. Furthermore, the space 152d of each first header 150 is connected to one end of the flat multi-hole pipes 110 in the 15th to 73rd rows from the bottom of the heat exchange section 100 corresponding to that first header 150, for example, and the space 152d is in communication with the flat multi-hole pipes 110 in the 15th to 73rd rows from the bottom of the heat exchange section 100.

[0109] (4-1-3) Second Header The second header 160 is a vertically long, hollow, cylindrical member with closed upper and lower ends. One second header 160 is provided for each of the two rows of heat exchange sections 100. However, the second header 160 may be a single cylindrical member shared by the two rows of heat exchange sections 100, and the interior may be divided into spaces corresponding to each of the two rows of heat exchange sections 100.

[0110] The two second headers 160 are installed in an upright position at the front left end of the housing 2a of the heat source unit 2 (see FIG. 2). To each second header 160, one end (the end not connected to the first header 150) of each of the multiple flat multi-hole pipes 110 of the corresponding heat exchange section 100 is connected.

[0111] Although the internal structure is not limited thereto, in the first heat exchanger 11 of this embodiment, the interior of each second header 160 is partitioned into eight independent spaces 162a to 162h. Inside the first header 150, spaces 162a, 162b, 162c, 162d, 162e, 162f, 162g, and 162h are arranged in this order from bottom to top.

[0112] The space 162a is connected to one end of the flat multi-hole tubes 110 in the lowest and second lowest row of the heat exchange section 100 corresponding to the first header 150 (in other words, the flat multi-hole tubes 110 of the first tube group 114), and the space 162a and the flat multi-hole tubes 110 of the first tube group 114 are connected to each other.

[0113] The space 162b is connected to each of the spaces 162c to 162h by a plurality of pipes 164, and the space 162b communicates with all of the plurality of spaces 162c to 162h. Furthermore, one ends of the flat multi-hole pipes 110 in the third to fourteenth rows from the bottom of the heat exchange section 100 corresponding to that first header 150 are connected to the space 162b, and the space 162b communicates with the flat multi-hole pipes 110 in the third to fourteenth rows from the bottom of the heat exchange section 100.

[0114] The spaces 162c to 162h are similar, and will be described simply.

[0115] The space 162c is connected to the space 162b by a pipe 164, and one ends of the flat multi-hole pipes 110 in the 15th to 24th rows from the bottom of the heat exchange section 100 corresponding to the first header 150 are connected thereto.

[0116] The space 162d is connected to the space 162b by a pipe 164, and one ends of the flat multi-hole pipes 110 in the 25th to 34th rows from the bottom of the heat exchange section 100 corresponding to the first header 150 are connected thereto.

[0117] The space 162e is connected to the space 162b by a pipe 164, and one ends of the flat multi-hole pipes 110 in the 35th to 44th rows from the bottom of the heat exchange section 100 corresponding to the first header 150 are connected thereto.

[0118] The space 162f is connected to the space 162b by a pipe 164, and one ends of the flat multi-hole pipes 110 in the 45th to 54th rows from the bottom of the heat exchange section 100 corresponding to the first header 150 are connected thereto.

[0119] The space 162f is connected to the space 162b by a pipe 164, and one ends of the flat multi-hole pipes 110 in the 55th to 64th rows from the bottom of the heat exchange section 100 corresponding to the first header 150 are connected thereto.

[0120] The space 162h is connected to the space 162b by a pipe 164, and one ends of the flat multi-hole pipes 110 in the 65th to 73rd rows from the bottom of the heat exchange section 100 corresponding to the first header 150 are connected thereto.

[0121] (4-1-4) Flow divider The flow divider 170 is a device that divides the refrigerant flowing in from the first path P1 into the spaces 152c of the two first headers 150, respectively, when the first heat exchanger 11 functions as an evaporator.

[0122] The flow distributor 170 has a flow distributor body 172, a pipe (main pipe) 174, and multiple pipes (capillaries) 176. The pipe 174 connects the flow distributor body 172 to the spaces 152b of each of the two first headers 150. The pipe 176 connects the flow distributor body 172 to the spaces 152c of each of the two first headers 150.

[0123] The flow divider main body 172 is a mechanism that divides the refrigerant flowing in from the pipe 174 into multiple pipes 176. Note that the flow divider 170 here divides the refrigerant that has flowed into the flow divider main body 172 into two pipes 176, but the number of flow paths into which the flow divider 170 divides the refrigerant may be determined appropriately depending on the path arrangement of the first heat exchanger 11, etc.

[0124] Here, the flow divider 170 is an example of a pressure loss section of the present disclosure.

[0125] When the first heat exchanger 11 is used as an evaporator, if a predetermined amount of refrigerant (for example, a specified maximum flow rate in normal operation) flows through the flow divider 170, which functions as a pressure loss section, and then through the second path P2, the total pressure loss in the pressure loss section becomes larger than the total pressure loss in the second path P2. In other words, the pressure loss section here is defined as a section where the total pressure loss is larger than the total pressure loss in the second path P2 when a predetermined amount of refrigerant (for example, a specified maximum flow rate in normal operation) flows through the first heat exchanger 11 as an evaporator.

[0126] Preferably, the minimum cross-sectional area of the flow path of the flow divider 170 or other form of pressure loss section is smaller than the sum of the cross-sectional areas of the flow path of the lowest flat multi-hole pipe 110 included in the first path P1. Note that, for example, as in Modification A described below, when a flat multi-hole pipe 110 other than the lowest one is connected in parallel to the lowest flat multi-hole pipe 110 in the first path P1, the minimum cross-sectional area of the flow path of the pressure loss section is smaller than the sum of the cross-sectional areas of the lowest flat multi-hole pipe 110 included in the first path P1 and the flat multi-hole pipe 110 connected in parallel to the lowest flat multi-hole pipe 110.

[0127] With this configuration, it is easy to compensate for the drop in pressure that is insufficient when the pressure is only flowed through the first path P1, using the pressure loss section.

[0128] To explain this with a specific example, in this embodiment, the first pass P1 includes the flat multi-hole tubes 110 of two rows of the heat exchange section 100 connected in parallel, and therefore the sum of the flow path cross-sectional areas of the lowermost flat multi-hole tubes 110 included in the first pass P1 means the sum of the flow path cross-sectional areas of the holes 112 of the two flat multi-hole tubes 110. The minimum flow path cross-sectional area of the flow divider 170 or other form of pressure loss section is preferably formed to be smaller than the sum of the flow path cross-sectional areas of the holes 112 of the two flat multi-hole tubes 110.

[0129] As a means for increasing the pressure loss of the flow divider 170, it is conceivable to provide an orifice 173 in the refrigerant flow path in the flow divider body 172, thereby making the pressure loss in the flow divider 170 a desired value.

[0130] Another possible means for increasing the pressure loss in the flow divider 170 is to appropriately select the pipe diameters of the pipes 174 and 176 for the predetermined amount of the above-mentioned refrigerant flowing into the first heat exchanger 11, in addition to or instead of providing an orifice 173 in the flow divider main body 172.

[0131] As another means for increasing the pressure loss in the flow divider 170, in addition to or instead of any of the above means, it is possible to provide an orifice 174a in the pipe 174 or an orifice 176a in the pipe 176.

[0132] Although FIG. 5 illustrates all of the orifice 173, orifice 174a, and orifice 176a, this does not mean that all of the orifice 173, orifice 174a, and orifice 176a need to be provided.

[0133] Although an example in which the flow divider 170 functions as a pressure loss section has been described here, a section other than a pressure loss section may also be used as the pressure loss section. For example, if flow division is not necessary after the flow exits the first path P1, the flow divider 170 may be omitted, and an orifice 171a may be provided in the pipe 171 connecting the space 152b and the space 152c of the first header 150, as shown in FIG.

[0134] (5) Refrigerant flow in the first heat exchanger (5-1) Characteristics and effects of the heat exchanger of the present disclosure First, with reference to FIGS. 8 and 9, the features of the heat exchanger of the present disclosure and the effects obtained by the heat exchanger of the present disclosure will be described.

[0135] FIG. 8A is a diagram for explaining the difference between the refrigerant flow in the heat exchanger of the present disclosure and the refrigerant flow in a conventional heat exchanger, and is a diagram conceptually showing the refrigerant flow in the heat exchanger HEX of the present disclosure when it functions as an evaporator.

[0136] FIG. 8B is a diagram for explaining the difference between the flow of refrigerant in the heat exchanger of the present disclosure and the flow of refrigerant in a conventional heat exchanger, and is a diagram conceptually showing the flow of refrigerant in the conventional heat exchanger HEX1 when it functions as an evaporator.

[0137] The heat exchanger HEX shown in Fig. 8A used in the description here is a simplified version of the heat exchanger of the present disclosure to facilitate understanding of the description, and has a different structure from the first heat exchanger 11 described above. For example, the heat exchanger HEX shown in Fig. 8A is not depicted as the refrigerant flowing through the flat multi-hole tubes 110 in the first pass P1. Furthermore, the heat exchanger HEX shown in Fig. 8A is not depicted as the refrigerant flowing through the flat multi-hole tubes 110 in the second pass P2.

[0138] 8B, the heat exchanger HEX1 is the same as the heat exchanger HEX of the present disclosure except for the way the refrigerant flows and the fact that the flow divider DIV is not intended to impart pressure loss. Like the heat exchanger HEX, the heat exchanger HEX1 is a heat exchanger in which multiple flat multi-hole tubes 110 are arranged in the vertical direction.

[0139] 9 is a diagram schematically showing a Mollier diagram of an air conditioner according to an embodiment of a refrigeration cycle apparatus having a heat exchanger HEX when the air conditioner is performing heating operation, for explaining the effects obtained by the heat exchanger HEX of the present disclosure. Note that FIG. 9 is a diagram for explanation purposes and does not represent an actual Mollier diagram of the air conditioner of the present disclosure.

[0140] In the conventional heat exchanger HEX1 shown in FIG. 8B, when the heat exchanger HEX1 is used as an evaporator, the entire amount of refrigerant flows into the flow divider DIV, is divided by the flow divider DIV, flows into each path of the heat exchange section of the heat exchanger HEX1, and then flows out of the heat exchanger HEX1. The heat exchanger HEX1 is configured such that the path length of the path including the lowest flat heat transfer tube in the heat exchange section (referred to as the lowest path) is longer than the path lengths of the other paths. For example, in the example of FIG. 8B, in paths other than the lowest path of the heat exchange section, the refrigerant flows out of the path without turning back (the path length is the length of one flat multi-hole tube), whereas in the lowest path of the heat exchange section, the refrigerant flows out after turning back twice and flowing through a length equivalent to three flat tubes. In the heat exchanger HEX1 of FIG. 8B, the pressure loss in the lowest pass of the heat exchange section is larger than in the other passes, so the amount of refrigerant flowing through the lowest pass of the heat exchange section is small and almost no heat exchange occurs, so frost is less likely to form on the flat heat transfer tubes in the lowest position of the heat exchange section.

[0141] However, in the conventional heat exchanger HEX1, the pressure loss in the lowest pass of the heat exchange section is not as large as in the heat exchanger HEX disclosed herein, and almost no refrigerant flows in the lowest pass of the heat exchange section, so when the outside air temperature drops, frost is likely to form on the flat multi-hole tubes in the lowest pass of the heat exchange section.

[0142] Furthermore, in heat exchanger HEX1, the pressure loss in the lowest path of the heat exchange section is greater than in the other paths, so even when heat exchanger HEX1 is used as a condenser during defrost operation, the amount of refrigerant flowing through the lowest path of the heat exchange section tends to be small. Therefore, once frost or ice forms on the lowest path of heat exchanger HEX1, it takes time to remove the frost or ice (until defrost operation is completed).

[0143] 8A , when the heat exchanger HEX of the present disclosure is used as an evaporator, the refrigerant passes through a first pass P1 of the heat exchange unit (a pass including the lowest flat multi-hole tube 110L) and flows into a flow divider 170 serving as a pressure loss unit, and then flows into a second pass P2 formed by the flat multi-hole tubes 110 (of the second tube group 116) other than the first tube group 114 that forms the first pass P1. In particular, in the first heat exchanger 11 described in the first embodiment, when the first heat exchanger 11 is used as an evaporator, the entire amount of refrigerant flowing into the first heat exchanger 11 passes through the first pass P1 of the heat exchange unit and flows into the flow divider 170 serving as a pressure loss unit, and then flows into the second pass P2 of the heat exchange unit formed by the flat multi-hole tubes 110 of the second tube group 116.

[0144] In the heat exchanger HEX of the present disclosure, the flow divider 170, which is an example of a pressure loss section, allows for a large pressure loss. Therefore, when an air conditioner according to an embodiment of the refrigeration cycle apparatus of the present disclosure is operated in a heating mode, the Mollier diagram shown in FIG. 9 shows a large temperature difference (Ta - Tb) between the inlet and outlet of the first path P1. Furthermore, when the entire amount of refrigerant flowing into the heat exchanger HEX is passed through the first path P1, as in the first heat exchanger 11 of the first embodiment, a larger amount of refrigerant can be passed through the first path P1 than in the lowest path of a conventional heat exchanger HEX1. As a result, heat dissipation in the first path P1 of the heat exchanger HEX is proportional to the product of the amount of refrigerant flowing through and the temperature difference (Ta - Tb). Therefore, frost formation in the first path P1 of the heat exchanger HEX is easily suppressed even when the temperature of the air being heat exchanged is low.

[0145] Furthermore, when the heat exchanger HEX is used as a condenser during defrosting operation, all refrigerant flowing into the heat exchanger HEX flows into the first path P1 after passing through the second path P2 and the flow divider 170. Therefore, even if frost adheres to the first path P1 or ice adheres to the flat multi-hole tubes 110L of the first path P1, the time required to remove these (defrosting operation time) can be shortened.

[0146] When the heat exchangers HEX and HEX1 function as radiators, the refrigerant flow direction is simply opposite to when the heat exchangers HEX and HEX1 function as evaporators, so detailed explanations will be omitted here.

[0147] (5-2) Refrigerant flow in the first heat exchanger Next, the flow of refrigerant in the first heat exchanger 11 when the first heat exchanger 11 described in the above embodiment functions as an evaporator will be described with reference to Figures 5 and 6. Note that the flow of refrigerant when the first heat exchanger 11 functions as a radiator is simply opposite to the flow direction of the refrigerant when the first heat exchanger 11 functions as an evaporator, and therefore a detailed description thereof will be omitted here.

[0148] When the first heat exchanger 11 functions as an evaporator, the refrigerant flows from the liquid refrigerant pipe 20 into the first piping 180, and then flows into the spaces 152a of the two first headers 150. As shown in Figures 5 and 6, the refrigerant that has flowed into the space 152a flows through the flat multi-hole pipe 110L (first path P1) of the heat exchange section 100 that is connected to that space 152a, turns back at the space 162a of the second header 160 that is connected to the flat multi-hole pipe 110L, and flows through the second-lowest flat multi-hole pipe 110 (first path P1) of the heat exchange section 100 that is connected to the space 162a, to the space 152b of the first header 150 that is connected to that flat multi-hole pipe 110. The refrigerant that has flowed into space 152b passes through the flow divider 170, via pipe 174, flow divider body 172, and pipe 176 in that order, and is divided into two flows that flow into spaces 152c of the two first headers 150. The refrigerant that has flowed into the spaces 152c of each first header 150 flows through the flat multi-hole pipes 110 (second path P2) of the heat exchange section 100 that are in communication with the spaces 152c, to the spaces 162b of the second header 160. The refrigerant that has flowed into the spaces 162b of each second header 160 is divided into multiple pipes 164, flows into spaces 162c to 162h of the second header 160, and flows through the flat multi-hole pipes 110 (second path P2) that are in communication with the spaces 162c to 162h of the second header 160, to the spaces 152d of the first header 150. The refrigerant that has flowed into the spaces 152d of the two first headers 150 passes through the second piping 190 and flows into the first gas refrigerant pipe 19.

[0149] In this embodiment, the first tube group 114 has two heat exchange sections 100 and includes a plurality of flat multi-hole tubes 110 arranged in parallel (connected in parallel). By including a plurality of flat multi-hole tubes 110 arranged in parallel in this manner, even when the entire amount of refrigerant flowing into the first heat exchanger 11 flows through the first path P1, it is possible to prevent excessive pressure loss in the flat multi-hole tubes 110 of the first path P1. In other words, if the entire amount of refrigerant supplied to the first heat exchanger 11 is flowed through a single flat multi-hole tube 110, there is a possibility that the pressure loss will be too excessive. In contrast, the first heat exchanger 11 of this embodiment includes a plurality of flat multi-hole tubes 110 arranged in parallel (connected in parallel), and therefore the occurrence of such excessive pressure loss can be prevented.

[0150] In the present embodiment, the refrigerant flows through the flat multi-hole tubes 110L in the first path P1 and then flows through the second-lowest flat multi-hole tube 110, but this configuration is merely an example. For example, the first path P1 may be configured only with the flat multi-hole tubes 110L, and the refrigerant that has flowed through the flat multi-hole tubes 110L of the two rows of heat exchange sections 100 may immediately flow into the flow diverter 170. However, if such a configuration is adopted, it may be necessary to connect the first pipe 180 to the second header 160 side of the first heat exchanger 11. However, from the viewpoint of ease of manufacturing the first heat exchanger 11, it is preferable that the first pipe 180 and the second pipe 190 be connected to the same header (particularly, the first header 150 in this embodiment).

[0151] (6) Features (6-1) The first heat exchanger 11 includes a plurality of flat multi-hole tubes 110 and a pressure loss section through which the refrigerant flows.

[0152] The pressure loss section is, for example, a flow divider 170. The pressure loss section is, for example, orifices 173, 174a, and 176a installed in the flow divider 170. Alternatively, the pressure loss section may be an orifice 171a installed in the pipe 171.

[0153] The plurality of flat multi-hole tubes 110 are arranged in a vertical direction. The plurality of flat multi-hole tubes 110 include flat multi-hole tubes 110 of a first tube group 114 including a flat multi-hole tube 110 (110L) arranged in the lowest stage of the first heat exchanger 11, and flat multi-hole tubes 110 of a second tube group 116 other than the flat multi-hole tubes 110 of the first tube group 114. The flat multi-hole tubes 110 of the first tube group 114 form a first path P1, which is a flow path of the refrigerant. The flat multi-hole tubes 110 of the second tube group 116 form a second path P2, which is a flow path of the refrigerant. When the first heat exchanger 11 functions as an evaporator, at least a portion of the refrigerant supplied to the first heat exchanger 11 flows through the first path P1, then flows into the pressure loss section, flows out of the pressure loss section, and flows into the second path P2.

[0154] In the first heat exchanger 11, a pressure loss section is provided downstream of the first path P1 in terms of the flow direction of the refrigerant when used as an evaporator. Therefore, in the first heat exchanger 11, a large pressure difference can be ensured from when the refrigerant enters the first path P1 to when it enters the second path P2, in other words, a large temperature difference can be ensured from when the refrigerant enters the first path P1 to when it enters the second path P2. Therefore, in the first heat exchanger 11, the amount of heat dissipated from the first path P1 when the first heat exchanger 11 functions as an evaporator can be ensured, and frost formation on the first path P1 can be suppressed.

[0155] (6-2) In the first heat exchanger 11, when the first heat exchanger 11 functions as an evaporator, the entire amount of refrigerant supplied to the first heat exchanger 11 flows through the first path P1 and then into the pressure loss section, and then flows through the pressure loss section and then into the second path P2.

[0156] In the first heat exchanger 11 of the second aspect, when the first heat exchanger 11 functions as an evaporator, the entire amount of refrigerant flowing into the first heat exchanger 11 flows through the first path P1, so that a large amount of heat can be dissipated from the first path P1 when the first heat exchanger 11 functions as an evaporator. Therefore, in the first heat exchanger 11, frost is unlikely to form on the lowest flat multi-hole tube 110 (110L).

[0157] Furthermore, when the first heat exchanger 11 functions as a radiator, all of the refrigerant that flows in passes through the second path P2 and then flows into the first path P1. By having all of the refrigerant flow through the first path P1, frost and ice that have adhered to the flat multi-hole tubes 110 of the first tube group 114 can be melted and removed in a relatively short time during reverse cycle defrosting in which the first heat exchanger 11 is used as a radiator.

[0158] For example, even if the water generated during defrosting freezes around the flat multi-hole tube 110L at the lowest stage of the first heat exchanger 11, the reverse cycle defrosting operation can melt the ice adhering to the flat multi-hole tube 110L and remove the ice in a relatively short time.

[0159] (6-3) In the first heat exchanger 11, the first tube group 114 includes a plurality of flat multi-hole tubes 110 arranged in parallel.

[0160] Specifically, in the above embodiment, when the first heat exchanger 11 functions as an evaporator, in the first path P1, the refrigerant flows in parallel through the lowest flat multi-hole tubes 110L of the two heat exchange sections 100, and then flows in parallel through the second-lowest flat multi-hole tubes 110 of the two heat exchange sections 100. Also, in the above embodiment, when the first heat exchanger 11 functions as a radiator, in the first path P1, the refrigerant flows in parallel through the second-lowest flat multi-hole tubes 110 of the two heat exchange sections 100, and then flows in parallel through the lowest flat multi-hole tubes 110L of the two heat exchange sections 100.

[0161] In the first heat exchanger 11, the occurrence of excessive pressure loss in the first path P1 can be suppressed.

[0162] (6-4) In the first heat exchanger 11, the number of flat multi-hole tubes 110 included in the first tube group 114 is smaller than the number of flat multi-hole tubes 110 included in the second tube group .

[0163] In the first heat exchanger 11, the refrigerant flow rate per each flat multi-hole tube 110 in the first path P1 can be made large, and the amount of heat dissipated from each flat multi-hole tube 110 in the first path P1 can be made large when the first heat exchanger 11 functions as an evaporator / heat radiator.

[0164] (6-5) The air conditioner 1 includes a refrigerant circuit 6 and a first fan 15 as an example of a blower. The refrigerant circuit 6 has a first heat exchanger 11 as a heat source heat exchanger, and a compressor 8 that compresses the refrigerant. The first fan 15 sends air to the first heat exchanger 11.

[0165] In the air conditioner 1, frost formation on the flat multi-hole tubes 110 of the first tube group 114 of the first heat exchanger 11 can be suppressed, and therefore the time during which the operation of the first heat exchanger 11 functioning as an evaporator is interrupted can be shortened.

[0166] Furthermore, in the air conditioning device 1, as described above, defrosting of the flat multi-hole tubes 110 of the first tube group 114 of the first heat exchanger 11 can be completed in a short time, so that defrosting operation, which is performed by interrupting operation of the first heat exchanger 11 to function as an evaporator, can be completed in a short time.

[0167] (7) Variations The above embodiment can be modified as appropriate, for example, as shown in the following modified examples. Note that each modified example may be applied in appropriate combination with other modified examples as long as they are not mutually contradictory.

[0168] (7-1) Variation A In the above embodiment, in the first path P1, the refrigerant flows through the lowest flat multi-hole tube 110L arranged in parallel between the two heat exchange sections 100, and then flows through the second-lowest flat multi-hole tube 110 arranged in parallel between the two heat exchange sections 100.

[0169] However, in the first path P1, the configuration in which the refrigerant flows through the plurality of flat multi-hole tubes 110 arranged in parallel (connected in parallel) is not limited to the above configuration. For example, in the first path P1, the refrigerant may flow through the flat multi-hole tubes 110 arranged in parallel at the bottom and second row from the bottom in one heat exchange section 100, and then flow through the flat multi-hole tubes 110 arranged in parallel at the third and fourth row from the bottom in that heat exchange section 100, as shown in Fig. 10 .

[0170] The configuration of the modified example A can be applied not only to the case where a plurality of rows of the heat exchange section 100 are present, but also to the case where there is only one row of the heat exchange section 100, for example.

[0171] (7-2) Variation B The first path P1 described in the above embodiment may be arranged only on the upwind side in the airflow direction A, where frost and ice are particularly likely to be a problem. For example, in the above embodiment, the first path P1 may be arranged only in the heat exchange unit 100u.

[0172] In this way, when the first path P1 is arranged only in the heat exchange section 100u, for example, the configuration of the heat exchange section 100 described in Modification A can be applied.

[0173] In addition, when the first path P1 is arranged only in the heat exchange section 100u, the first heat exchanger 11 can be designed so that the refrigerant flows through the first path P1, then through the flow divider 170, and then through the second path P2 which includes all the flat multi-hole tubes 110 in the heat exchange section 100d and the flat multi-hole tubes 110 other than the first tube group 114 in the heat exchange section 100u.

[0174] (7-3) Variation C In the above embodiment, in order to suppress excessive pressure loss, the refrigerant is made to flow through a plurality of flat multi-hole tubes 110 arranged in parallel in the first path P1.

[0175] However, the configuration of the first pass P1 for suppressing excessive pressure loss is not limited to this configuration. For example, to suppress excessive pressure loss in the first pass P1, the flow path area of each of the flat multi-hole tubes 110 in the first tube group 114 may be larger than the flow path area of each of the flat multi-hole tubes 110 in the second tube group 116. Specifically, the flat multi-hole tubes constituting the first pass P1 may be flat multi-hole tubes having larger-sized holes 112 and a larger number of holes 112 than the other flat multi-hole tubes 110, such as the flat multi-hole tube 110a in the heat exchange unit 100u in FIG. 11 . Alternatively, the flat multi-hole tube 110a may have only one of the following configurations: the holes 112 are larger in size than the other flat multi-hole tubes 110; or the holes 112 are larger in number than the other flat multi-hole tubes 110.

[0176] FIG. 10 illustrates an example in which the first path P1 is arranged only in the heat exchange section 100u.

[0177] (7-4) Variation D In the above embodiment, the pressure loss portion is the flow divider 170 or the orifice 171a installed in the pipe 171, but the pressure loss portion may also be a nozzle disposed inside the header. Specifically, the pressure loss portion may also be a nozzle 154 disposed in the space 152c of the first header 150.

[0178] 12, a structure may be provided in space 152c of first header 150 such that, when first heat exchanger 11 functions as an evaporator, refrigerant flowing in from pipe 176 is blown upward by nozzle 154, and the refrigerant is circulated in the upper space as shown by the arrows, while being diverted to flat multi-hole pipe 110 communicating with space 152c. Then, first heat exchanger 11 may be designed so that a desired pressure loss is generated by this nozzle 154.

[0179] (7-5) Variation E In the above embodiment, the entire amount of refrigerant flowing into the first heat exchanger 11 flows through the first path P1.

[0180] However, when the refrigeration cycle apparatus in which the heat exchanger is used is enlarged, the amount of refrigerant flowing into the heat exchanger becomes extremely large, and if all of the refrigerant is flowed through the first path P1, the pressure loss occurring in the first path P1 may become excessive. Increasing the number of flat multi-hole tubes 110 in the first tube group 114 and flowing the refrigerant through a large number of flat multi-hole tubes 110 connected in parallel can suppress the pressure loss occurring in the first path P1, but this configuration reduces the number of flat multi-hole tubes 110 belonging to the second path P2, which mainly contributes to heat exchange, and this may reduce the efficiency of the refrigeration cycle apparatus.

[0181] Therefore, the heat exchanger HEX of the present disclosure may be provided with a bypass path that guides the refrigerant to the second path P2 without flowing through the first path P1, as shown in Fig. 13. In Fig. 13, the path through which the refrigerant flows through the first path P1 and then through the flow divider 170 to the second path P2 is called the main path M, and the path through which the refrigerant flows through the flow divider 170 to the second path P2 without flowing through the first path P1 is called the bypass path B.

[0182] In order to reduce pressure loss in the first path P1, it is preferable to reduce the amount of refrigerant flowing through the first path P1. However, from the perspective of preventing frost formation, it is preferable to have a larger amount of refrigerant flowing through the first path P1. Therefore, it is preferable that at least 50% of the amount of refrigerant supplied to the heat exchanger HEX flows through the first path P1. It is even more preferable that at least 70% of the amount of refrigerant supplied to the heat exchanger HEX flows through the first path P1.

[0183] In this heat exchanger HEX, when an extremely large amount of refrigerant is supplied to the heat exchanger HEX, the entire amount of refrigerant flows through the first path P1, causing excessive pressure loss, which prevents the occurrence of a problem in which the efficiency of the air conditioning device 1 using the heat exchanger HEX decreases.

[0184] <Additional Notes> Although the embodiments and modifications of the present disclosure have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the present disclosure as defined in the claims. [Explanation of symbols]

[0185] 1. Air conditioning equipment (refrigeration cycle equipment) 6 Refrigerant circuit 8 Compressor 11 1st heat exchanger (heat exchanger) 15 First fan (blower) 110 Flat multi-hole pipe 110a Flat multi-hole pipe (first group of flat multi-hole pipes) 110L Flat multi-hole pipe placed at the bottom 114 1st Tube Group 116 2nd Tube Group 150 First Header (Header) 154 Nozzle (pressure loss section) 170 Flow divider (pressure loss section) 171a Orifice (pressure loss part) 173 Orifice (pressure loss part) 174a Orifice (pressure loss part) 176a Orifice (pressure loss part) A Airflow direction B. Bypass route P1 First pass P2 2nd pass [Prior art documents] [Patent documents]

[0186] [Patent Document 1] Japanese Patent Application Publication No. 2019-60596

Claims

1. A plurality of flat multi-hole pipes (110) arranged in a vertical direction; a pressure loss portion (154, 170, 171a, 173, 174a, 176a) through which a refrigerant flows; A heat exchanger comprising: The plurality of flat multi-hole tubes include the flat multi-hole tubes of a first tube group (114) including only the flat multi-hole tubes arranged in the lowest stage of the heat exchanger or only the flat multi-hole tubes arranged in the lowest and second stages of the heat exchanger, and the flat multi-hole tubes of a second tube group (116) other than the flat multi-hole tubes of the first tube group, The flat multi-hole tubes of the first tube group form a first path (P1) that is a flow path for the refrigerant and suppresses frost formation on the flat multi-hole tubes in the lowest stage, The flat multi-hole tubes of the second tube group form a second path (P2) that is a flow path of the refrigerant, When the heat exchanger functions as an evaporator, all of the refrigerant supplied to the heat exchanger flows through the first path and then into the pressure loss section, and then flows through the pressure loss section and then into the second path. Heat exchanger (11).

2. The first tube group includes a plurality of the flat multi-hole tubes arranged in parallel. The heat exchanger of claim 1 .

3. The flow path area of each of the flat multi-hole pipes (110a) of the first pipe group is larger than the flow path area of each of the flat multi-hole pipes (110) of the second pipe group. The heat exchanger of claim 1 .

4. the number of the flat multi-hole tubes included in the first tube group is smaller than the number of the flat multi-hole tubes included in the second tube group; The heat exchanger of claim 1 .

5. The pressure loss portion is an orifice (171a, 173, 174a, 176a) disposed in the refrigerant flow path between the first path and the second path. The heat exchanger of claim 1 .

6. The pressure loss portion is a flow divider (170) disposed in the flow path of the refrigerant between the first path and the second path. The heat exchanger of claim 1 .

7. a header (150) disposed in the refrigerant flow path between the first path and the second path; The pressure loss portion is a nozzle (154) disposed inside the header. The heat exchanger of claim 1 .

8. The flat multi-hole tubes are arranged in a plurality of rows in a direction (A) of an airflow generated by a blower that sends air to the heat exchanger, The first path is arranged only on the upwind side in the direction of the airflow. The heat exchanger of claim 1 .

9. a refrigerant circuit (6) having the heat exchanger according to claim 1 as a heat source heat exchanger and a compressor (8) for compressing the refrigerant; a blower (15) for blowing air into the heat exchanger; A refrigeration cycle device (1) comprising:

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