Heat exchanger and refrigeration cycle device

Abstract

A first header (21) of a heat exchanger (1) has: a first flow path (57) through which a refrigerant flows from one end (41) to the other end (42) in the longitudinal direction (25); a second flow path (58) through which the refrigerant flows from the other end (42) to said one end (41); a first return flow path (51) through which the refrigerant flows from the first flow path (57) to the second flow path (58) at the other end (42); a second return flow path (52) through which the refrigerant flows from the second flow path (58) to the first flow path (57) at said one end (41); and an inlet (61) through which the refrigerant flows from an inflow space (43) to said one end (41) of the first flow path (57). The first flow path (57) is connected to a second header (22) through a plurality of heat transfer pipes (23). The first flow path (57) is formed such that, when the heat exchanger (1) functions as an evaporator, the degree of superheating of the refrigerant flowing into the second header (22) from the heat transfer pipe located farthest from the inflow space (43) among the plurality of heat transfer pipes (23) is zero degrees.

Description

Heat exchanger and refrigeration cycle device

[0001] The technology of the present disclosure relates to a heat exchanger and a refrigeration cycle device.

[0002] A known heat exchanger for exchanging heat between air and a refrigerant includes a header that divides a gas-liquid two-phase refrigerant into multiple heat transfer tubes (see Patent Document 1). Inside the header, a circulation flow path is connected to multiple insertion spaces, each of which accommodates one end of the heat transfer tubes. The circulation flow path includes a first flow path, a second flow path, a first return flow path that connects the upper end of the first flow path to the upper end of the second flow path, and a second return flow path that connects the lower end of the second flow path to the lower end of the first flow path. The gas-liquid two-phase refrigerant that enters the header circulates through the circulation flow path, ascending through the first flow path, flowing from the upper end of the first flow path to the upper end of the second flow path via the first return flow path, descending through the second flow path, and flowing from the lower end of the second flow path to the lower end of the first flow path via the second return flow path. Such a heat exchanger can prevent the refrigerant from stagnating in the upper part of the first flow path by circulating the gas-liquid two-phase refrigerant that has flowed into the header through the circulation flow path, and can appropriately divide the gas-liquid two-phase refrigerant into multiple heat transfer tubes so that the flow rates of the refrigerant flowing through each of the multiple heat transfer tubes are equal to each other.

[0003] Japanese Patent Application Laid-Open No. 2019-056544

[0004] However, in such a heat exchanger, when the flow rate of the gas-liquid two-phase refrigerant circulating through the circulation flow path is low, the liquid refrigerant cannot rise up the first flow path, and the proportion of liquid refrigerant flowing into the upper heat transfer tubes among the plurality of heat transfer tubes may decrease. When the amount of liquid refrigerant flowing into the plurality of heat transfer tubes varies, the upper heat transfer tubes with less liquid refrigerant flowing therethrough may lose all of the liquid refrigerant as it flows through them. On the other hand, the lower heat transfer tubes with more liquid refrigerant flowing therethrough may not fully evaporate as they flow through them, and some liquid refrigerant may flow out of them. In this way, when there are heat transfer tubes where all of the liquid refrigerant evaporates and heat transfer tubes where incomplete liquid refrigerant flows out, there is a problem of reduced evaporation performance when the heat exchanger functions as an evaporator.

[0005] The disclosed technology has been made in consideration of the above points, and aims to provide a heat exchanger and a refrigeration cycle device that improve the evaporation performance of a heat exchanger that functions as an evaporator.

[0006] A heat exchanger according to one aspect of the present disclosure comprises a plurality of heat transfer tubes, a first header, and a second header, wherein the first header has a first flow path that allows refrigerant to flow from one end side to the other end side in the longitudinal direction of the first header, a second flow path that allows refrigerant to flow from the other end side to the one end side, a first return flow path that allows refrigerant to flow from the first flow path to the second flow path at the other end side, a second return flow path that allows refrigerant to flow from the second flow path to the first flow path at the one end side, an inlet space into which the refrigerant flows, and an inlet port that allows refrigerant to flow from the inlet space to the end of the first flow path on the one end side, wherein the first flow path is connected to the second header via the plurality of heat transfer tubes, and the first flow path is formed so that the superheat of the refrigerant flowing into the second header from the heat transfer tube that is farthest from the inlet space among the plurality of heat transfer tubes when the heat exchanger functions as an evaporator is 0 degrees.

[0007] The disclosed heat exchanger and refrigeration cycle device can improve the evaporation performance of the heat exchanger functioning as an evaporator.

[0008] Fig. 1 is a refrigerant circuit diagram showing an air conditioner provided with a heat exchanger of the embodiment. Fig. 2 is a front view showing the heat exchanger of the embodiment. Fig. 3 is a top view showing the heat exchanger of the embodiment. Fig. 4 is a cross-sectional view showing a heat transfer tube of the heat exchanger of the embodiment. Fig. 5 is an exploded perspective view showing the internal structure of an expansion valve side header of the heat exchanger of the embodiment.

[0009] Hereinafter, a heat exchanger and a refrigeration cycle apparatus according to embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the following description does not limit the technology of the present disclosure. In addition, in the following description, the same components are given the same reference numerals, and duplicated descriptions will be omitted.

[0010] As shown in Fig. 1, the heat exchanger of the embodiment is an outdoor heat exchanger 1 provided in an air conditioner 10. Fig. 1 is a refrigerant circuit diagram of the air conditioner 10 provided with the outdoor heat exchanger 1 of the embodiment. The air conditioner 10 includes an outdoor unit 2 and an indoor unit 3. The outdoor unit 2 is installed outdoors. The indoor unit 3 is installed inside an indoor room.

[0011] The air conditioner 10 includes a refrigerant circuit 4 (refrigeration cycle device). The refrigerant circuit 4 includes a compressor 5, a four-way valve 6, an indoor heat exchanger 7, an expansion valve 8, and an outdoor heat exchanger 1. The compressor 5 is disposed inside the outdoor unit 2. A suction pipe 11 and a discharge pipe 12 are connected to the compressor 5. The compressor 5 compresses the refrigerant supplied to the suction pipe 11 and discharges the refrigerant to the discharge pipe 12 at a flow rate corresponding to the compressor rotation speed. The flow rate of the refrigerant discharged by the compressor 5 to the discharge pipe 12 per unit time increases as the compressor rotation speed increases.

[0012] The four-way valve 6 is disposed inside the outdoor unit 2. The four-way valve 6 is connected to a suction pipe 11 and a discharge pipe 12, is connected to the outdoor heat exchanger 1 via a refrigerant pipe 14, and is connected to the indoor heat exchanger 7 via a refrigerant pipe 15. The four-way valve 6 switches the refrigerant circuit 4 between a heating cycle and a cooling cycle. When the refrigerant circuit 4 is switched to the heating cycle, the discharge pipe 12 is connected to the indoor heat exchanger 7 via the four-way valve 6, and the suction pipe 11 is connected to the outdoor heat exchanger 1 via the four-way valve 6. When the refrigerant circuit 4 is switched to the cooling cycle, the discharge pipe 12 is connected to the outdoor heat exchanger 1 via the four-way valve 6, and the suction pipe 11 is connected to the indoor heat exchanger 7 via the four-way valve 6.

[0013] The indoor heat exchanger 7 is disposed inside the indoor unit 3. One refrigerant inlet / outlet of the indoor heat exchanger 7 is connected to the expansion valve 8 via refrigerant piping 16, and the other refrigerant inlet / outlet is connected to the four-way valve 6 via refrigerant piping 15 as described above. The indoor unit 3 rotates a fan (not shown) to pass air from the room in which the indoor unit 3 is installed through the indoor heat exchanger 7 to exchange heat with the refrigerant, and then blows the air that has exchanged heat with the refrigerant into the room. The expansion valve 8 is disposed inside the outdoor unit 2. The expansion valve 8 is connected to the outdoor heat exchanger 1 via refrigerant piping 17. The air conditioner 10 adjusts the opening degree of the expansion valve 8 to adjust the amount of refrigerant flowing through the indoor heat exchanger 7 according to the air-conditioning capacity required by the indoor unit 3.

[0014] The outdoor unit 2 is equipped with an outdoor fan 18. The outdoor fan 18 is disposed inside the outdoor unit 2. The outdoor fan 18 blows outdoor air so that the air flows into a ventilation space 19 inside the outdoor unit 2. A ventilation direction 20 in which the air flows due to the outdoor fan 18 is generally horizontal when the outdoor unit 2 is properly installed. The outdoor heat exchanger 1 is disposed inside the outdoor unit 2 and fixed to the outdoor unit 2 so that the air flowing through the ventilation space 19 passes through the outdoor heat exchanger 1. The outdoor heat exchanger 1 exchanges heat between the refrigerant flowing through the outdoor heat exchanger 1 and the air flowing through the ventilation space 19.

[0015] 2 is a front view showing the outdoor heat exchanger 1 of the embodiment. The outdoor heat exchanger 1 includes an expansion valve side header 21 (first header), a compressor side header 22 (second header), a plurality of heat transfer tubes 23, and a plurality of fins 24. The expansion valve side header 21 is formed in a columnar shape and is disposed so that a header longitudinal direction 25 (longitudinal direction) that is the extension direction of the expansion valve side header 21 is perpendicular to the bottom surface of the outdoor unit 2 (not shown), and is fixed to the outdoor unit 2. A refrigerant pipe 17 is connected to the expansion valve side header 21, and an expansion valve 8 is connected via the refrigerant pipe 17.

[0016] The compressor side header 22 is formed in a columnar shape, is disposed so that the extension direction of the compressor side header 22 is parallel to the header longitudinal direction 25, and is fixed to the outdoor unit 2. A flow dividing space is formed inside the compressor side header 22. The refrigerant piping 14 is connected to the compressor side header 22 so that the four-way valve 6 is connected to the flow dividing space via the refrigerant piping 14.

[0017] 2 and 3 , the plurality of heat transfer tubes 23 are arranged so that a heat transfer tube longitudinal direction 26, which is the extension direction of the heat transfer tubes, is perpendicular to the header longitudinal direction 25, and are lined up at equal intervals in the header longitudinal direction 25. One end of each of the plurality of heat transfer tubes 23 is connected to the expansion valve side header 21. The other end of each of the plurality of heat transfer tubes 23 is connected to the compressor side header 22. The plurality of heat transfer tubes 23 are fixed to the expansion valve side header 21 and the compressor side header 22 by connecting both ends of the plurality of heat transfer tubes 23 to the expansion valve side header 21 and the compressor side header 22, respectively, and the outdoor heat exchanger 1 is fixed to the outdoor unit 2 by the expansion valve side header 21 and the compressor side header 22.

[0018] Each of the fins 24 is formed in a flat plate shape. Fig. 3 is a top view showing the outdoor heat exchanger 1 of the embodiment. The fins 24 are arranged perpendicular to the heat transfer tube longitudinal direction 26 (parallel to the ventilation direction 20) and are aligned at equal intervals in the heat transfer tube longitudinal direction 26. The fins 24 are fixed to the heat transfer tubes 23 so as to be thermally connected to them.

[0019] Each of the plurality of heat transfer tubes 23 is formed in a flat shape, as shown in Fig. 4. Fig. 4 is a cross-sectional view of the heat transfer tube 23 of the outdoor heat exchanger 1 of the embodiment. A plurality of flow paths 33 are formed inside the heat transfer tube 23 and aligned in the ventilation direction 20. The other ends of the plurality of heat transfer tubes 23 are connected to the compressor-side header 22, so that the plurality of flow paths 33 are connected to the flow branch space of the compressor-side header 22.

[0020] 5 is an exploded perspective view showing the internal structure of the expansion valve-side header 21 of the outdoor heat exchanger 1 of the embodiment. The expansion valve-side header 21 includes a plurality of plate-like members 71 to 76 that are all rectangular in shape. The plurality of plate-like members 71 to 76 are stacked and joined to one another, with the stacking direction being generally parallel to the heat transfer tube longitudinal direction 26. The plurality of plate-like members 71 to 76 include a refrigerant piping-side plate-like member 71, a heat transfer tube-side plate-like member 72, a plurality of circulation flow path plate-like members 73, a plurality of return flow path plate-like members 74, a plurality of insertion space plate-like members 75, and an introduction hole plate-like member 76. 5 , the plate-like members are stacked in the following order from upstream to downstream in an introduction direction 48 (the direction in which refrigerant flows in the outdoor heat exchanger 1 when the outdoor heat exchanger 1 functions as an evaporator): a refrigerant piping-side plate-like member 71, multiple return flow path plate-like members 74, multiple circulation flow path plate-like members 73, an introduction hole plate-like member 76, multiple insertion space plate-like members 75, and a heat transfer tube-side plate-like member 72. In the following description, when referring to the multiple return flow path plate-like members 74, the multiple circulation flow path plate-like members 73, and the multiple insertion space plate-like members 75 formed by the multiple plate-like members 71 to 76, the word "multiple" may be omitted when referring to a structure in which the multiple plate-like members 71 to 76 are joined together.

[0021] The circulation flow path plate members 73 are formed to have the same shape (in this embodiment, the three circulation flow path plate members 73 shown in FIG. 5 have the same shape). The return flow path plate member 74 is disposed between the circulation flow path plate member 73 and the refrigerant pipe side plate member 71. The insertion space plate members 75 are formed to have the same shape (in this embodiment, the three insertion space plate members 75 shown in FIG. 5 have the same shape). The insertion space plate member 75 is disposed between the introduction hole plate member 76 and the heat transfer tube side plate member 72. The introduction hole plate member 76 is disposed between the circulation flow path plate member 73 and the insertion space plate member 75.

[0022] In the following description, the end face of the lower end of the expansion valve side header 21 in the header longitudinal direction 25 will be referred to as one end 41, and the end face of the upper end of the expansion valve side header 21 opposite the one end 41 will be referred to as the other end 42.

[0023] The expansion valve-side header 21 is formed by stacking the above-described plate-like members in the order from upstream to downstream in the introduction direction 48: refrigerant piping-side plate-like member 71, return flow path plate-like member 74, circulation flow path plate-like member 73, introduction hole plate-like member 76, insertion space plate-like member 75, and heat transfer tube-side plate-like member 72, thereby forming an inflow space 43, a refrigerant piping through-hole 44, a circulation flow path 45, an inlet 61, a plurality of insertion spaces 46, a plurality of heat transfer tube through-holes 47, and a plurality of introduction holes 62 inside the expansion valve-side header 21. The inflow space 43 is located in a region of the interior of the expansion valve-side header 21 close to the one end 41. The inflow space 43 is formed from inflow space holes 83 formed in each circulation flow path plate-like member 73.

[0024] The refrigerant piping through-hole 44 is formed by a refrigerant piping hole 77 formed in the refrigerant piping side plate-like member 71 and a refrigerant piping hole 78 formed in the return flow path plate-like member 74. Therefore, the refrigerant piping through-hole 44 is disposed upstream of the inflow space 43 in the introduction direction 48. The refrigerant piping 17 passes through the refrigerant piping through-hole 44, and the inflow space 43 is connected to the expansion valve 8 via the refrigerant piping 17.

[0025] The circulation flow path 45 is formed by a circulation flow path plate-shaped member 73 and a turn-back flow path plate-shaped member 74, and includes a first flow path 57, a second flow path 58, a first turn-back flow path 51, and a second turn-back flow path 52. The first flow path 57 is formed from first flow path holes 84 formed in a plurality of the circulation flow path plate-shaped members 73. The second flow path 58 is formed from second flow path holes 85 formed in a plurality of the circulation flow path plate-shaped members 73. Therefore, the first flow path 57 and the second flow path 58 are aligned with the inflow space 43 in the header longitudinal direction 25 and are located above the inflow space 43. The first flow path 57 is formed along a straight line parallel to the header longitudinal direction 25. The second flow path 58 is located upwind of the first flow path 57 in the ventilation direction 20 and is formed along another straight line parallel to the header longitudinal direction 25.

[0026] The first turn flow path 51 is formed by first turn flow path holes 81 formed in the plurality of turn flow path plate members 74, and turns the refrigerant flowing through the first flow path 57 back to the second flow path 58. That is, the direction in which the refrigerant flows through the first turn flow path 51 is perpendicular to the introduction direction 48 and parallel to the ventilation direction 20. The second turn flow path 52 is formed by second turn flow path holes 82 formed in the plurality of turn flow path plate members 74, and turns the refrigerant flowing through the second flow path 58 back to the first flow path 57. That is, the direction in which the refrigerant flows through the second turn flow path 52 is perpendicular to the introduction direction 48 and parallel to the ventilation direction 20. Therefore, the first turn flow path 51 and the second turn flow path 52 are aligned in the header longitudinal direction 25 and are disposed upstream of the first flow path 57 and the second flow path 58 in the introduction direction 48. The first turning flow path 51 is formed in a region close to the other end 42, and is connected to the upper end of the first flow path 57 and the upper end of the second flow path 58. The second turning flow path 52 is formed in a lower region close to the one end 41, and is connected to the lower end of the first flow path 57 and the lower end of the second flow path 58.

[0027] The inlet 61 is formed from an inlet hole 86 formed in the plurality of circulation flow path plate-shaped members 73. Therefore, the inlet 61 is disposed between the inflow space 43 and the first flow path 57, and the refrigerant that has flowed into the inlet 61 flows into the first flow path 57 via the inlet 61.

[0028] The multiple insertion spaces 46 are formed by communicating multiple insertion space holes 87 formed in the multiple insertion space plate-shaped members 75. Therefore, the multiple insertion spaces 46 are arranged downstream in the introduction direction 48 as seen from the region where the inflow space 43 and the circulation flow path 45 are arranged, and are aligned in the header longitudinal direction 25. The volumes of the multiple insertion spaces 46 are approximately equal to each other.

[0029] The multiple introduction holes 62 are formed in the introduction hole plate member 76. Therefore, the multiple introduction holes 62 are aligned in the header longitudinal direction 25 and are respectively disposed between the first flow passage 57 and the multiple insertion spaces 46. The multiple insertion spaces 46 and the first flow passage 57 are connected by the multiple introduction holes 62.

[0030] The plurality of heat transfer tube through holes 47 are formed in the heat transfer tube side plate member 72. Therefore, the plurality of heat transfer tube through holes 47 are arranged downstream in the introduction direction 48 as seen from the plurality of insertion spaces 46, and are aligned at equal intervals in the header longitudinal direction 25. The plurality of insertion spaces 46 are connected to each heat transfer tube 23 via the plurality of heat transfer tube through holes 47, respectively.

[0031] The expansion valve side header 21 has an inflow space side insertion space 53, an inflow space side introduction passage 64, and an inflow space side through hole 54. The inflow space side insertion space 53 is formed from a lowest-stage insertion space hole formed in the lowest stage of each insertion space plate-like member 75 in the header longitudinal direction 25. Therefore, the inflow space side insertion space 53 is the lowest stage of the multiple insertion spaces 46 in the header longitudinal direction 25, and is located downstream of the inflow space 43 in the introduction direction 48. The inflow space side introduction passage 64 is formed at the lowest stage of the multiple introduction holes 62 in the header longitudinal direction 25, and is located between the inflow space 43 and the inflow space side insertion space 53 in the introduction direction 48. The inflow space side insertion space 53 and the inflow space 43 are in communication via the inflow space side introduction passage 64. The inflow space side through hole 54 is formed at the lowest of the multiple heat transfer tube through holes 47 in the header longitudinal direction 25, and is arranged downstream of the inflow space side insertion space 53 in the introduction direction 48. The inflow space side insertion space 53 communicates with the heat transfer tube 23 connected to the inflow space side through hole 54.

[0032] The surfaces of each of the multiple plate-like members 71-76 are coated with brazing material. The plate-like members are stacked and heated in a furnace, melting the brazing material and bonding them together to form the expansion valve side header 21. Because the expansion valve side header 21 is formed by stacking multiple plate-like members 71-76 with their outer peripheries aligned, the strength and durability of the expansion valve side header 21 can be improved compared to, for example, a box-shaped header formed by combining plate-like members and U-shaped members. Furthermore, because the expansion valve side header 21 is formed by stacking multiple plate-like members 71-76, changes to the refrigerant flow path in the expansion valve side header 21 or the number of heat transfer tubes 23 to be joined can be accommodated by simply changing one of the plate-like members. This improves the design flexibility of the outdoor heat exchanger 1, including the expansion valve side header 21, and reduces development and manufacturing costs.

[0033] The plurality of heat transfer tubes 23 pass through the plurality of heat transfer tube through holes 47 and the inflow space side through hole 54, respectively, and are joined to the expansion valve side header 21. Specifically, the inflow space side heat transfer tube arranged at the bottom of the plurality of heat transfer tubes 23 passes through the inflow space side through hole 54 and is joined to the expansion valve side header 21. The remaining heat transfer tubes of the plurality of heat transfer tubes 23, other than the inflow space side heat transfer tube, pass through the plurality of heat transfer tube through holes 47, respectively, and are joined to the expansion valve side header 21.

[0034] The air conditioner 10 can perform heating operation and cooling operation, which will be described below. [Heating Operation] The heating operation is performed, for example, when the air conditioner 10 is operated by a user to perform heating operation. When the air conditioner 10 performs heating operation, the four-way valve 6 switches the refrigerant circuit 4 to the heating cycle. The compressor 5 compresses the low-pressure gas-phase refrigerant that flows from the four-way valve 6 into the suction pipe 11. The low-pressure gas-phase refrigerant is compressed by the compressor 5 to become high-pressure gas-phase refrigerant. The compressor 5 discharges the high-pressure gas-phase refrigerant to the discharge pipe 12. Since the refrigerant circuit 4 has been switched to the heating cycle, the high-pressure gas-phase refrigerant discharged to the discharge pipe 12 flows into the indoor heat exchanger 7 via the four-way valve 6.

[0035] The indoor unit 3 passes air from the room in which the indoor unit 3 is installed through the indoor heat exchanger 7. The indoor heat exchanger 7 exchanges heat between the high-pressure gas-phase refrigerant that has flowed into the indoor heat exchanger 7 and the air passing through the indoor heat exchanger 7, cooling the high-pressure gas-phase refrigerant that has flowed into the indoor heat exchanger 7 and heating the air passing through the indoor heat exchanger 7. The indoor unit 3 blows the air heated by the indoor heat exchanger 7 into the room in which the indoor unit 3 is installed, heating the room. The high-pressure gas-phase refrigerant is cooled and condensed in the indoor heat exchanger 7, becoming a supercooled high-pressure liquid-phase refrigerant. In other words, the indoor heat exchanger 7 functions as a condenser when the air conditioner 10 performs heating operation. The high-pressure liquid-phase refrigerant flows out of the indoor heat exchanger 7 and flows into the expansion valve 8.

[0036] The expansion valve 8 reduces the pressure of the high-pressure liquid-phase refrigerant that has flowed into the expansion valve 8. The high-pressure liquid-phase refrigerant is reduced in pressure by the expansion valve 8 and becomes a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant flows out of the expansion valve 8 and flows into the refrigerant pipe 17. The outdoor fan 18 flows outdoor air into the ventilation space 19.

[0037] The low-pressure gas-liquid two-phase refrigerant flowing through the refrigerant pipe 17 flows into the inlet space 43 of the expansion valve-side header 21 through the refrigerant pipe through-hole 44. The low-pressure gas-liquid two-phase refrigerant that has flowed into the inlet space 43 further flows into the lower end region 59 of the first flow path 57 through the inlet 61. The low-pressure gas-liquid two-phase refrigerant that has flowed into the lower end region 59 through the inlet 61 flows through the first flow path 57 toward the other end 42 in the header longitudinal direction 25. At this time, the refrigerant is diverted from the first flow path 57 to each of the inlet holes 62. The remaining gas-liquid two-phase refrigerant that has flowed through the first flow path 57 and reached the upper end region 60 of the first flow path 57 (other than the diverted refrigerant that has flowed into each of the inlet holes 62) flows into the second flow path 58 through the first return flow path 51. The low-pressure gas-liquid two-phase refrigerant that has flowed into the second flow path 58 flows through the second flow path 58 toward the one end 41. The low-pressure gas-liquid two-phase refrigerant flowing through the second flow path 58 flows from the second flow path 58 through the second return flow path 52 into the lower end region 59 of the first flow path 57, and then flows through the first flow path 57 toward the other end 42. In this manner, the expansion valve side header 21 circulates the low-pressure gas-liquid two-phase refrigerant through the circulation flow path 45, from the first flow path 57 → the first return flow path 51 → the second flow path 58 → the second return flow path 52 → the first flow path 57, while dividing the refrigerant into each introduction hole 62.

[0038] When the amount of refrigerant circulating through the refrigerant circuit 4 is small and the amount of gas-liquid two-phase refrigerant flowing into the expansion valve-side header 21 is small, the flow velocity of the gas-liquid two-phase refrigerant flowing through the first flow path 57 slows. In this case, liquid refrigerant, which has a higher specific gravity than gas refrigerant (and is therefore heavier than gas refrigerant), cannot reach the upper end region 60, or the amount of liquid refrigerant that reaches it is small. As a result, the amount of liquid refrigerant flowing through the upper heat transfer tubes 23 is less than the amount of liquid refrigerant flowing through the lower heat transfer tubes 23. When the amount of liquid refrigerant flowing through the multiple heat transfer tubes 23 varies, in the upper heat transfer tubes 23 where less liquid refrigerant flows, all of the liquid refrigerant evaporates midway through the heat transfer tube due to latent heat change. From this point onward, the gas refrigerant is heated up to the refrigerant outlet side of the heat transfer tube 23 (the connection with the compressor-side header 22) and becomes superheated gas due to sensible heat change. In other words, in the upper heat transfer tubes 23 where less liquid refrigerant flows, the liquid refrigerant can still evaporate in the region where the gas refrigerant is superheated, but the small amount of liquid refrigerant prevents effective use of the region. On the other hand, in the lower heat transfer tubes 23 where there is a large amount of liquid refrigerant flowing, the liquid refrigerant cannot all evaporate due to latent heat change while flowing through the heat transfer tube, and the liquid refrigerant flows out of the heat transfer tube. When the outdoor heat exchanger 1 functions as an evaporator, evaporation performance is fully exhibited when all the liquid refrigerant evaporates at the refrigerant outlet side of each heat transfer tube 23. However, in a state where all the liquid refrigerant evaporates along the way as described above in some heat transfer tubes 23 or where incompletely evaporated liquid refrigerant flows out of some heat transfer tubes 23, the evaporation performance of the outdoor heat exchanger 1 decreases.

[0039] In order to solve the above problems, in this embodiment, the shape of the first flow path 57 is adjusted so that, even when the amount of refrigerant circulating in the refrigerant circuit 4 is small, the liquid refrigerant of the low-pressure gas-liquid two-phase refrigerant that has flowed into the expansion valve side header 21 reaches the upper end region 60 of the first flow path 57. Specifically, the cross-sectional area of ​​the first flow path 57 is adjusted to shape the first flow path 57 so that the flow velocity of the liquid refrigerant flowing through the first flow path 57 is sufficient to reach the upper end region 60.

[0040] By adjusting the shape of the first flow passage 57 as described above, even when the amount of refrigerant circulating in the refrigerant circuit 4 is small, the flow velocity of the liquid refrigerant flowing through the first flow passage 57 can be ensured, allowing the liquid refrigerant to reach the upper end region 60. This suppresses a decrease in the flow rate of the liquid refrigerant in the upper heat transfer tubes 23. Note that, when there are a large number of heat transfer tubes 23, that is, when the height of the expansion valve side header 21 is large, adjusting the shape of the first flow passage 57 may not be able to ensure the flow velocity of the liquid refrigerant that allows the liquid refrigerant to reach the upper end region 60. In such cases, the diameter of the inlet 61 may be adjusted to increase the initial velocity of the liquid refrigerant in the lower end region 59 of the first flow passage 57. The increased initial velocity ensures the flow velocity of the liquid refrigerant flowing through the first flow passage 57, allowing the liquid refrigerant to reach the upper end region 60 of the first flow passage 57.

[0041] When a large amount of refrigerant circulating through the refrigerant circuit 4 results in a large amount of gas-liquid two-phase refrigerant flowing into the expansion valve side header 21, the amount of low-pressure gas-liquid two-phase refrigerant flowing through the first flow path 57 is greater than when a small amount of refrigerant circulates and flows into the expansion valve side header 21. At this time, the flow velocity of the low-pressure gas-liquid two-phase refrigerant flowing through the first flow path 57 is higher when a large amount of refrigerant circulates through the refrigerant circuit 4 than when a small amount of refrigerant circulates through the refrigerant circuit 4, due to the higher rotation speed of the compressor 5. Because the liquid refrigerant in the low-pressure gas-liquid two-phase refrigerant has a higher density and a larger mass per unit volume than the gas refrigerant, the flow velocity of the liquid refrigerant is slower than the flow velocity of the gas refrigerant, which has a lighter mass per unit volume. Therefore, the flow of the gas refrigerant pushes the liquid refrigerant toward the upper end region 60 of the first flow path 57, where it tends to stagnate. In this way, when liquid refrigerant stagnates in the upper end region 60 of the first flow path 57, the amount of liquid refrigerant flowing from the upper end region 60 of the first flow path 57 to the heat transfer tubes 23 becomes greater than the amount of liquid refrigerant flowing from below the upper end region 60 of the first flow path 57 to the heat transfer tubes 23, resulting in an imbalance in the flow rate of liquid refrigerant between the heat transfer tubes 23.

[0042] To solve the above problem, this embodiment provides a circulation flow path 45 that directs the gas-liquid two-phase refrigerant flowing upward along the first flow path 57 to the second flow path 58 and then returns it to the first flow path 57. By providing the circulation flow path 45, liquid refrigerant accumulating in the upper end region 60 of the first flow path 57 can be returned to the first flow path 57 via the second flow path 58. If liquid refrigerant accumulates in the upper end region 60, the flow rate of the liquid refrigerant in the upper heat transfer tubes 23 will be higher than that of the other heat transfer tubes 23. However, by circulating the liquid refrigerant accumulating in the upper end region 60 through the circulation flow path 45, the amount of liquid refrigerant accumulating in the upper end region 60 is reduced, and the reduced amount is diverted to each insertion space 46, thereby suppressing unevenness in the amount of liquid refrigerant in each heat transfer tube 23.

[0043] The low-pressure gas-liquid two-phase refrigerant that has flowed into the inlet space 43 flows into the first flow path 57 via the inlet 61 and into the inlet space side insertion space 53 adjacent to the inlet space 43 in the introduction direction 48 via the inlet space side introduction flow path 64. When the gas-liquid two-phase refrigerant flows from the inlet 61 to the first flow path 57, the flow direction turns at a right angle from horizontal to vertical in the inlet space 43, and after becoming vertical, flows upward against gravity. On the other hand, when the gas-liquid two-phase refrigerant flows from the inlet 61 to the inlet space side insertion space 53 via the inlet space side introduction flow path 64, the flow direction remains horizontal and does not flow against gravity. For the above reasons, the resistance experienced by the gas-liquid two-phase refrigerant flowing into the inlet space-side insertion space 53 (only the pressure loss in the inlet space 43, the inlet space-side introduction flow path 64, and the inlet space-side insertion space 53; hereinafter referred to as the first flow path resistance) is smaller than the resistance experienced by the gas-liquid two-phase refrigerant flowing into the first flow path 57 (the pressure loss in the inlet space 43, the inlet 61, and the first flow path 57, the pressure loss due to the bending of the flow path, and the influence of gravity; hereinafter referred to as the second flow path resistance). Thus, when the first flow path resistance is smaller than the second flow path resistance, most of the liquid refrigerant in the gas-liquid two-phase refrigerant that flows into the inlet space 43 flows into the inlet space-side insertion space 53, but the amount of liquid refrigerant flowing into the first flow path 57 is reduced. As a result, the amount of liquid refrigerant flowing into the heat transfer tube 23 connected to the inlet space-side insertion space 53 becomes larger than the amount of liquid refrigerant flowing into each of the other heat transfer tubes 23 (heat transfer tubes connected to the multiple insertion spaces 46 that communicate with the first flow path 57).

[0044] To solve the above problem, in this embodiment, the shape of the inflow-space-side insertion space 53 is adjusted to adjust the first flow path resistance, thereby reducing the amount of liquid refrigerant flowing through the heat transfer tubes 23 connected to the inflow-space-side insertion space 53 and suppressing variations in the flow rate of the liquid refrigerant in the other heat transfer tubes 23. Specifically, the shape (size and cross-sectional area) of the inflow-space-side insertion space 53 is adjusted so that the first flow path resistance multiplied by the number of heat transfer tubes 23 to which the liquid refrigerant is diverted from the first flow path 57 is equal to the second flow path resistance. For example, if there is one heat transfer tube 23 connected to the inflow-space-side insertion space 53 and eight heat transfer tubes 23 to which the liquid refrigerant is diverted from the first flow path 57, and it is desired to flow an equal amount A of liquid refrigerant through all of the heat transfer tubes 23, the shape of the inflow-space-side insertion space 53 is adjusted so that the first flow path resistance multiplied by the number of heat transfer tubes 23 to which the liquid refrigerant is diverted from the first flow path 57 (eight) is equal to the second flow path resistance. As a result, the flow resistance of each heat transfer tube 23 becomes equal, so that the unevenness in the amount of liquid refrigerant flowing through each heat transfer tube 23 can be corrected.

[0045] Note that there are limitations to adjusting the shape of the inflow-space-side insertion space 53 due to the need to connect the heat transfer tubes 23. For example, the dimension of the inflow-space-side insertion space 53 in the airflow direction 20 must correspond to the dimension of the inserted heat transfer tubes 23 in the airflow direction 20. For example, it cannot be smaller than the dimension of the heat transfer tubes 23 in the airflow direction 20. Furthermore, the dimension of the inflow-space-side insertion space 53 in the introduction direction 48 requires a certain distance between the tip of the inflow-space-side insertion space 53 and the inflow-space-side introduction flow path 64 (if the tip of the inflow-space-side insertion space 53 and the inflow-space-side introduction flow path 64 are too close, more refrigerant will flow into the flow paths 33 closer to the inflow-space-side introduction flow path 64). Even if the shape is adjusted while satisfying these constraints, it may not be possible to obtain a first flow path resistance such that the value obtained by multiplying the first flow path resistance by the number of heat transfer tubes 23 to which liquid refrigerant is diverted from the first flow path 57 is equal to the second flow path resistance.

[0046] When the first flow path resistance cannot be adjusted by simply adjusting the shape of the inflow space-side insertion space 53 as described above, the first flow path resistance may be adjusted by adjusting the diameter of the inflow space-side introduction flow path 64. Alternatively, the first flow path resistance may be adjusted by disposing a structure that obstructs the flow of refrigerant, such as a triangular prism or a square prism, between the tip of the refrigerant pipe 17 inserted into the refrigerant pipe through-hole 44 in the inflow space 43 and the inflow space-side introduction flow path 64. The inflow space-side introduction flow path 64 and the structure that obstructs the flow of refrigerant correspond to the resistance adjuster of the technology of the present disclosure.

[0047] The low-pressure gas-liquid two-phase refrigerant that has flowed into the multiple insertion spaces 46 and the inlet-space-side insertion space 53 flows into the multiple flow paths 33 formed inside the multiple heat transfer tubes 23 and toward the compressor-side header 22. At this time, by adjusting the shape of the first flow path 57 and the inlet-space-side insertion space 53 as described above, unevenness in the flow rate of the liquid refrigerant flowing through the multiple flow paths 33 is suppressed, that is, the distribution of the liquid refrigerant to the multiple heat transfer tubes 23 is improved. The liquid refrigerant flowing through the multiple heat transfer tubes 23 exchanges heat with the air flowing through the ventilation space 19 and evaporates, becoming low-pressure gas-phase (gas) refrigerant, and flows out of the multiple heat transfer tubes 23 into the compressor-side header 22.

[0048] As described above, since uneven flow of the liquid refrigerant in each heat transfer tube 23 is suppressed, just the right amount of liquid refrigerant flows through the multiple heat transfer tubes 23. At this time, the refrigerant state at the refrigerant outlet side of each heat transfer tube 23, i.e., at the location where each heat transfer tube 23 is connected to the compressor-side header 22, is such that the liquid refrigerant has completely evaporated to become gas refrigerant at that location, or the gas refrigerant is mixed with some liquid refrigerant that has not completely evaporated, thereby fully demonstrating the heat exchange performance of the outdoor heat exchanger 1. Note that if the liquid refrigerant has completely evaporated to become gas refrigerant at the refrigerant outlet side of each heat transfer tube 23, or the gas refrigerant is mixed with some liquid refrigerant that has not completely evaporated, the refrigerant superheat at that location is 0 degrees. Therefore, when verifying the effects of the technology disclosed herein, it is sufficient to detect and confirm the refrigerant superheat at the refrigerant outlet side of each heat transfer tube 23. For example, when the amount of refrigerant circulating in the refrigerant circuit 4 is at its minimum, if the degree of refrigerant superheat at the refrigerant outlet side of the uppermost heat transfer tube 23 is checked and this value is 0 degrees, it can be confirmed that a sufficient amount of liquid refrigerant is flowing in the uppermost heat transfer tube 23, which is the most difficult for liquid refrigerant to flow through when the amount of refrigerant circulating is at its minimum, and it is considered that at least the same amount of refrigerant as the liquid refrigerant flowing in the uppermost heat transfer tube 23 is flowing in the other heat transfer tubes 23, and therefore it can be considered that liquid refrigerant is flowing in all heat transfer tubes 23 in the right amount, and the heat exchange performance of the outdoor heat exchanger 1 is being fully demonstrated.

[0049] The low-pressure gas-phase refrigerant flowing out from the heat transfer tubes 23 join together in the compressor-side header 22 and flows out from the compressor-side header 22. The low-pressure gas-phase refrigerant flowing out from the compressor-side header 22 flows into the four-way valve 6 via the refrigerant piping 14, and because the refrigerant circuit 4 is switched to the heating cycle, flows into the suction pipe 11 of the compressor 5 via the four-way valve 6.

[0050] [Cooling Operation] When the user operates the air conditioner 10 to perform cooling operation, the four-way valve 6 is switched so that the refrigerant circuit 4 is in the cooling cycle. The compressor 5 compresses the low-pressure gas-phase refrigerant drawn in from the four-way valve 6 through the suction pipe 11. The low-pressure gas-phase refrigerant is compressed by the compressor 5 to become high-pressure gas-phase refrigerant, which is then discharged to the discharge pipe 12. Because the refrigerant circuit 4 has been switched to the cooling cycle, the high-pressure gas-phase refrigerant discharged to the discharge pipe 12 flows into the outdoor heat exchanger 1 via the four-way valve 6 and the refrigerant piping 14.

[0051] The high-pressure gas-phase refrigerant that flows into the outdoor heat exchanger 1 flows into the compressor-side header 22 and is diverted to the multiple heat transfer tubes 23. The high-pressure gas-phase refrigerant diverted to the multiple heat transfer tubes 23 exchanges heat with air flowing through the ventilation space 19 due to the rotation of the outdoor fan 18, condensing and becoming a supercooled high-pressure liquid-phase refrigerant. In other words, the outdoor heat exchanger 1 functions as a condenser when the air conditioner 10 performs cooling operation. The high-pressure liquid-phase refrigerant flows out of the multiple heat transfer tubes 23 and into the multiple insertion spaces 46 and the inlet-space-side insertion space 53 of the expansion valve-side header 21. The high-pressure liquid-phase refrigerant that flows into the multiple insertion spaces 46 flows into the first flow path 57 of the circulation flow path 45 through the multiple introduction holes 62 and merges there. The high-pressure liquid-phase refrigerant that merged in the first flow path 57 flows into the inlet space 43 through the inlet 61. The high-pressure liquid-phase refrigerant that has flowed into the inlet-space-side insertion space 53 flows into the first flow path 57 of the circulation flow path 45 through the multiple introduction holes 62, and merges in the inlet space 43 with the high-pressure liquid-phase refrigerant that has flowed into the inlet space 43 through the inlet 61. The high-pressure liquid-phase refrigerant that has merged in the inlet space 43 flows into the refrigerant pipe 17 through the refrigerant pipe through-hole 44, and flows through the refrigerant pipe 17 and into the expansion valve 8.

[0052] The high-pressure liquid-phase refrigerant that flows into the expansion valve 8 is decompressed to become a low-pressure gas-liquid two-phase refrigerant, which then flows out of the expansion valve 8, flows through the refrigerant pipe 16, and flows into the indoor heat exchanger 7. The low-pressure gas-liquid two-phase refrigerant that flows into the indoor heat exchanger 7 exchanges heat with room air drawn into the indoor unit 3 by the rotation of an indoor fan (not shown). As a result, the low-pressure gas-liquid two-phase refrigerant that flows into the indoor heat exchanger 7 cools the air passing through the indoor heat exchanger 7, and the cooled air is blown into the room where the indoor unit 3 is installed, thereby cooling the room. Meanwhile, the low-pressure gas-liquid two-phase refrigerant that flows into the indoor heat exchanger 7 is heated and evaporated in the indoor heat exchanger 7 to become a low-pressure gas-phase refrigerant. In other words, the indoor heat exchanger 7 functions as an evaporator when the air conditioner 10 performs cooling operation. The low-pressure gas-phase refrigerant that flows out of the indoor heat exchanger 7 flows sequentially through the refrigerant pipe 15, the four-way valve 6, and the suction pipe 11, and is drawn into the compressor 5 where it is compressed again.

[0053] [Effects of the Heat Exchanger of the Embodiment] The heat exchanger of the embodiment includes a plurality of heat transfer tubes 23, an expansion valve side header 21, and a compressor side header 22. The expansion valve side header 21 has a first flow path 57, a second flow path 58, a first return flow path 51, a second return flow path 52, an inflow space 43, and an inlet 61. The first flow path 57 allows refrigerant to flow from the one end 41 side to the other end 42 side of the expansion valve side header 21 in the header longitudinal direction 25. The second flow path 58 allows refrigerant to flow from the other end 42 side to the one end 41 side. The first return flow path 51 allows refrigerant to flow from the first flow path 57 to the second flow path 58 at the other end 42 side. The second return flow path 52 allows refrigerant to flow from the second flow path 58 to the first flow path 57 at the one end 41 side. The refrigerant flows into the inflow space 43. The inlet 61 allows the refrigerant to flow from the inflow space 43 into the end of the first flow path 57 on the side of the one end 41. The first flow path 57 communicates with the compressor-side header 22 via a plurality of heat transfer tubes 23. The first flow path 57 is formed so that, when the heat exchanger of the embodiment functions as an evaporator, the degree of superheat of the refrigerant flowing from the uppermost heat transfer tube, which is located farthest from the inflow space 43 among the plurality of heat transfer tubes 23, into the compressor-side header 22 is 0 degrees.

[0054] That is, in the heat exchanger of the embodiment, even when the liquid refrigerant is least likely to flow through the uppermost heat transfer tube 23, the shape of the first flow path 57 can be adjusted so that the degree of refrigerant superheat at the refrigerant outlet side of the heat transfer tube 23 is 0°, that is, the liquid refrigerant flows to such an extent that it reaches the refrigerant outlet side. Therefore, the heat exchanger of the embodiment can suppress uneven flow of the liquid refrigerant to the plurality of heat transfer tubes 23, thereby improving evaporation performance when functioning as an evaporator.

[0055] Furthermore, the shape of the first flow path 57 of the heat exchanger of the embodiment is formed based on the minimum value of the flow rate of refrigerant flowing per unit time from the inflow space 43 into the first flow path 57 when the heat exchanger of the embodiment functions as an evaporator. When the amount of refrigerant circulating in the refrigerant circuit 4 is at a minimum, the amount of refrigerant flowing into the first flow path 57 is at a minimum, as described above. However, since the shape of the first flow path 57 is adjusted in anticipation of such a case, it is possible to suppress uneven flow of liquid refrigerant into the plurality of heat transfer tubes 23 even when the amount of refrigerant circulating in the refrigerant circuit 4 is at a minimum, and it is possible to improve evaporation performance when the heat exchanger functions as an evaporator.

[0056] Furthermore, the shape of the inflow space-side insertion space 53 of the heat transfer tubes 23 of the heat exchanger of the embodiment is adjusted so that the first flow path resistance multiplied by the number of the other heat transfer tubes 23 is equal to the second flow path resistance, thereby preventing the amount of liquid refrigerant flowing through the heat transfer tube 23 connected to the inflow space-side insertion space 53 from being larger than the amount of liquid refrigerant flowing through the other heat transfer tubes 23. This makes it possible to suppress uneven flow of liquid refrigerant to each heat transfer tube 23, and improves evaporation performance when functioning as an evaporator.

[0057] In the heat exchanger of the above-described embodiment, the inlet-space-side insertion space 53 has a limited shape due to the need to connect the heat transfer tubes 23. Even when the shape is adjusted to the maximum extent possible, the first flow resistance multiplied by the number of other heat transfer tubes 23 may not equal the second flow resistance (for example, when the number of other heat transfer tubes 23 is large, resulting in a large second flow resistance). In such cases, a resistance adjuster for adjusting the first flow resistance may be further provided in the expansion valve-side header 21. For example, the first flow resistance may be adjusted by adjusting the diameter of the inlet-space-side introduction flow path 64. Alternatively, the first flow resistance may be adjusted by disposing a structure, such as a triangular prism or a square prism, that obstructs the flow of refrigerant between the tip of the refrigerant pipe 17 inserted in the refrigerant pipe through-hole 44 in the inlet space 43 and the inlet-space-side introduction flow path 64.

[0058] Although the embodiments have been described above, the embodiments are not limited to the above content. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the scope of so-called equivalents. Furthermore, the above-described components can be combined as appropriate. Furthermore, at least one of various omissions, substitutions, and modifications of the components can be made within the scope that does not deviate from the gist of the embodiments.

[0059] DESCRIPTION OF SYMBOLS 1: Outdoor heat exchanger (heat exchanger) 4: Refrigerant circuit (refrigeration cycle device) 5: Compressor 21: Expansion valve side header (first header) 22: Compressor side header (second header) 23: Multiple heat transfer tubes 25: Header longitudinal direction (longitudinal direction) 41: One end 42: Other end 43: Inflow space 44: Refrigerant piping through hole 46: Insertion space 47: Multiple heat transfer tube through holes 48: Introduction direction 51: First turned flow path 52: Second turned flow path 53: Inflow space side insertion space 54: Inflow space side through hole 57: First flow path 58: Second flow path 61: Inlet 62: Introduction hole 64: Inflow space side introduction flow path

Claims

1. A heat exchanger comprising: a plurality of heat transfer tubes; a first header; and a second header, wherein the first header has: a first flow path for causing a refrigerant to flow from one end side to the other end side in the longitudinal direction of the first header; a second flow path for causing a refrigerant to flow from the other end side to the one end side; a first return flow path for causing a refrigerant to flow from the first flow path to the second flow path at the other end side; a second return flow path for causing a refrigerant to flow from the second flow path to the first flow path at the one end side; an inflow space into which the refrigerant flows; and an inflow port for causing the refrigerant to flow from the inflow space to the end of the first flow path on the one end side, wherein the first flow path is in communication with the second header via the plurality of heat transfer tubes, and the first flow path is formed such that the superheat of the refrigerant flowing into the second header from the heat transfer tube among the plurality of heat transfer tubes that is located farthest from the inflow space is 0 degrees when the heat exchanger functions as an evaporator.

2. A heat exchanger as described in claim 1, wherein the cross-sectional area of ​​the first flow path is determined based on the minimum flow rate of refrigerant flowing from the inflow space into the first flow path per unit time when the heat exchanger functions as an evaporator.

3. A heat exchanger according to claim 1, further comprising an inlet space side heat transfer tube located closer to the inlet space than the plurality of heat transfer tubes, wherein the first header further has an inlet space side insertion space in which one end of the inlet space side heat transfer tube is arranged, and an inlet space side introduction flow path connecting the inlet space to the inlet space side insertion space, wherein refrigerant that flows from the inlet space into the inlet space side insertion space via the inlet space side introduction flow path flows to the second header via the inlet space side heat transfer tube, and the inlet space side insertion space is formed so that a second flow path resistance that the refrigerant flowing through the first flow path receives from the first flow path is equal to a target resistance calculated by multiplying a first flow path resistance that the refrigerant flowing through the inlet space side insertion space receives from the inlet space side insertion space by the number of the plurality of heat transfer tubes.

4. The heat exchanger according to claim 3, further comprising a resistance adjusting section that adjusts the first flow path resistance.

5. A refrigeration cycle device in which a compressor compresses a refrigerant that has undergone heat exchange in a heat exchanger, thereby circulating the refrigerant in a refrigerant circuit, the heat exchanger comprising a plurality of heat transfer tubes, a first header, and a second header, the first header having: a first flow path for causing the refrigerant to flow from one end side to the other end side in the longitudinal direction of the first header; a second flow path for causing the refrigerant to flow from the other end side to the one end side; a first return flow path for causing the refrigerant to flow from the first flow path to the second flow path on the other end side; a second return flow path for causing the refrigerant to flow from the second flow path to the first flow path on the one end side; an inflow space into which the refrigerant flows; and an inflow port for causing the refrigerant to flow from the inflow space into the end of the first flow path on the one end side. the first flow path is formed such that, when the heat exchanger functions as an evaporator and the amount of refrigerant flowing through the refrigerant circuit is at a minimum, the degree of superheat of the refrigerant flowing into the second header from one of the plurality of heat transfer tubes that is located farthest from the inflow space is 0 degrees.

6. The refrigeration cycle device according to claim 5, wherein the compressor circulates refrigerant through the refrigerant circuit at a flow rate corresponding to a compressor rotation speed, and the first flow path is formed so that the degree of superheat is 0 degrees when the compressor rotation speed is a minimum rotation speed.

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