Heat exchanger

Abstract

To improve an amount of heat exchange between a refrigerant and air.SOLUTION: An outdoor heat exchanger 1 includes a plurality of heat transfer pipes 23 and an expansion valve side header 21 that branches a refrigerant to the plurality of heat transfer pipes 23. The plurality of heat transfer pipes 23 are arranged aligned in a header longitudinal direction 25. The expansion valve side header 21 includes therein a first flow path 57 through which the refrigerant flows from the lower side to the upper side, a second flow path 58 through which the refrigerant flows from the upper side to the lower side, a first return flow path 51 through which the refrigerant flows from the upper end of the first flow path 57 to the upper end of the second flow path 58, a second return flow path 52 through which the refrigerant flows from the lower end of the second flow path 58 to the lower end of the first flow path 57, and a plurality of insertion spaces 46 in which one ends of the plurality of heat transfer pipes 23 are disposed respectively. The plurality of insertion spaces 46 guide the refrigerant guided from the first flow path 57 to the plurality of heat transfer pipes 23. The first flow path 57 and the second flow path 58 are disposed between the plurality of insertion spaces 46, and the first return flow path 51 and the second return flow path 52.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The technology of the present disclosure relates to a heat exchanger. [Background technology]

[0002] A heat exchanger is known that includes a plurality of heat transfer tubes and a header that distributes a refrigerant among the heat transfer tubes. For example, Patent Document 1 discloses a header that includes a circulation flow path and a plurality of inlet holes that connect the circulation flow path to the heat transfer tubes. The circulation flow path includes a first flow path that allows the refrigerant to flow from one longitudinal end of the header to the other longitudinal end, a second flow path that allows the refrigerant to flow from the other longitudinal end to the one longitudinal end, a first return flow path that allows the refrigerant to flow from the first flow path to the second flow path at the other longitudinal end, and a second return flow path that allows the refrigerant to flow from the second flow path to the first flow path at the one longitudinal end. In this heat exchanger, the refrigerant that flows into the header is circulated through the circulation flow path while being distributed among the heat transfer tubes. This prevents the refrigerant from flowing unevenly among some of the heat transfer tubes, thereby preventing a decrease in the heat exchange rate between the refrigerant and air. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-8974 Summary of the Invention [Problem to be solved by the invention]

[0004] In the heat exchanger of Patent Document 1, the direction in which the refrigerant flows from the first flow path to the first turn flow path is the same as the direction in which the refrigerant flows from the inlet hole to the heat transfer tube. In this case, if a heat transfer tube is provided at a location in the longitudinal direction of the header corresponding to the first turn flow path, much of the refrigerant flowing from the first flow path to the first turn flow path may flow into the heat transfer tube, which may impair the flow distribution to each heat transfer tube and reduce the heat exchange rate. To prevent this deterioration in flow distribution, the heat exchanger of Patent Document 1 does not provide a heat transfer tube at a location corresponding to the first turn flow path. However, this reduces the number of heat transfer tubes provided in the heat exchanger, resulting in a problem of reduced heat exchange rate.

[0005] The disclosed technology has been made in consideration of the above points, and proposes a heat exchanger that improves the amount of heat exchanged between a refrigerant and air. [Means for solving the problem]

[0006] A heat exchanger according to one aspect of the present disclosure includes a plurality of heat transfer tubes and a header that distributes a refrigerant to the plurality of heat transfer tubes, the plurality of heat transfer tubes being arranged side by side in a longitudinal direction of the header, the header having therein a first flow path that distributes the refrigerant from one end side to the other end side in the longitudinal direction of the header, a second flow path that distributes the refrigerant from the other end side to the one end side, a first return flow path that distributes the refrigerant from the first flow path to the second flow path at the other end side, and a second return flow path that distributes the refrigerant from the second flow path at the one end side. The heat transfer tubes have a second return flow path that flows the refrigerant from the first flow path to the first flow path, and a plurality of insertion spaces in which one end of each of the plurality of heat transfer tubes is disposed, and the plurality of insertion spaces guide the refrigerant introduced from at least one of the first flow path and the second flow path to the plurality of heat transfer tubes, and the first flow path and the second flow path are disposed between the plurality of insertion spaces and the first return flow path and the second return flow path in an introduction direction in which the refrigerant is introduced from one of the flow paths to the plurality of heat transfer tubes. [Effects of the Invention]

[0007] The disclosed heat exchanger can improve the amount of heat exchange between the refrigerant and the air. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a refrigerant circuit diagram showing an air conditioner provided with a heat exchanger according to an embodiment. [Figure 2] FIG. 2 is a front view showing the heat exchanger of the embodiment. [Figure 3] FIG. 3 is a top view showing the heat exchanger of the embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing a heat transfer tube of a heat exchanger according to an embodiment. [Figure 5] FIG. 5 is an exploded perspective view showing an expansion valve side header of the heat exchanger of the embodiment. [Figure 6] FIG. 6 is an exploded perspective view showing the expansion valve side header of the heat exchanger of Comparative Example 1. As shown in FIG. [Figure 7] FIG. 7 is an exploded perspective view showing the first return flow path of the heat exchanger of Comparative Example 2. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a heat exchanger according to an embodiment 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. [Example]

[0010] The heat exchanger of the embodiment is an outdoor heat exchanger 1 provided in an air conditioner 10, as shown in Fig. 1. 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. 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 sucked through the suction pipe 11 and discharges the compressed refrigerant to the discharge pipe 12.

[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 and outlet of the indoor heat exchanger 7 is connected to the expansion valve 8 via refrigerant piping 16, and the other refrigerant inlet and outlet is connected to the four-way valve 6 via refrigerant piping 15 as described above. By rotating a fan (not shown), the indoor unit 3 passes 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 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 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 approximately 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 (header), a compressor side header 22, a plurality of heat transfer tubes 23, and a plurality of fins 24. The expansion valve side header 21 is formed in a cylindrical shape, and is disposed so that a header longitudinal direction 25 (longitudinal direction) which 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 arranged 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] The heat transfer tubes 23 are arranged at equal intervals in the header longitudinal direction 25 as shown in FIG. 2 . One end of each of the heat transfer tubes 23 is connected to the expansion valve side header 21. The other end of each of the heat transfer tubes 23 is connected to the compressor side header 22. The 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 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. In the following description, the extension direction of the heat transfer tubes 23 as shown in FIG. 2 is defined as a heat transfer tube longitudinal direction 26. This heat transfer tube longitudinal direction 26 is a direction perpendicular to the header longitudinal direction 25.

[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 approximately 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 the 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): refrigerant piping side plate-like member 71, multiple return flow path plate-like members 74, multiple circulation flow path plate-like members 73, introduction hole plate-like member 76, multiple insertion space plate-like members 75, and 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 combination of the multiple plate-like members 71 to 76 joined together.

[0021] The circulation flow path plate-shaped members 73 are formed to have the same shape (in this embodiment, the three circulation flow path plate-shaped members 73 shown in FIG. 5 have the same shape). The return flow path plate-shaped member 74 is disposed between the circulation flow path plate-shaped member 73 and the refrigerant pipe side plate-shaped member 71. The insertion space plate-shaped members 75 are formed to have the same shape (in this embodiment, the three insertion space plate-shaped members 75 shown in FIG. 5 have the same shape). The insertion space plate-shaped member 75 is disposed between the introduction hole plate-shaped member 76 and the heat transfer tube side plate-shaped member 72. The introduction hole plate-shaped member 76 is disposed between the circulation flow path plate-shaped member 73 and the insertion space plate-shaped 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 of refrigerant pipe-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 from upstream to downstream in the introduction direction 48, thereby forming an inflow space 43, a refrigerant pipe 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 inside 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 on the upstream side of the inflow space 43 in the introducing 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 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 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-shaped 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-shaped 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 width dimension of the first turning flow path 51 in the ventilation direction 20 is equal to the width of the second turning flow path 52 in the ventilation direction 20. On the other hand, the width dimension of the first turning flow path 51 in the header longitudinal direction 25 is larger than the width of the second turning flow path 52 in the ventilation direction 20. Therefore, the flow path cross-sectional area of ​​the first turning flow path 51 when viewed from the introduction direction 48 is larger than the flow path cross-sectional area of ​​the second turning flow path 52 when viewed from the introduction direction 48.

[0028] 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.

[0029] The multiple insertion spaces 46 are formed by communication between 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 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. In this embodiment, seven of the multiple insertion spaces 46 from the top are upper insertion spaces 68, and the remaining one is the bottommost insertion space 53. The bottommost insertion space 53 is arranged below the multiple upper insertion spaces 68 and is the lowest of the multiple insertion spaces 46. The volume of the bottommost insertion space 53 is larger than the volume of each of the multiple upper insertion spaces 68 and is the largest of the multiple insertion spaces 46. The volumes of the multiple upper insertion spaces 68 are generally equal to each other.

[0030] The heat transfer tube through holes 47 are formed in the heat transfer tube side plate member 72. Therefore, the heat transfer tube through holes 47 are arranged downstream in the introduction direction 48 as seen from the insertion spaces 46, and are aligned at equal intervals in the header longitudinal direction 25. In this embodiment, of the heat transfer tube through holes 47, seven heat transfer tube through holes 47 counting from the top are defined as upper heat transfer tube through holes 67, and the remaining two heat transfer tube through holes 47 are defined as bottom-most heat transfer tube through holes 54. The two bottom-most heat transfer tube through holes 54 are positioned below the upper heat transfer tube through holes 67, i.e., they are positioned at the lowest of the heat transfer tube through holes 47 and are positioned downstream in the introduction direction 48 as seen from the inflow space 43.

[0031] Burrings (not shown) are formed on the heat transfer tube side plate-like member 72. When the heat transfer tube through-holes 47 are formed in the heat transfer tube side plate-like member 72, the burrings are formed so as to protrude upstream in the introduction direction 48 from the edges of the heat transfer tube holes. As a result, when the plurality of plate-like members 71 to 76 are appropriately stacked, the burrings are disposed in the plurality of insertion spaces 46. Each heat transfer tube 23 is inserted into each heat transfer tube through-hole 47 and welded to the burring of each heat transfer tube through-hole 47 (for example, by melting a layer of brazing material previously provided on the surface of the heat transfer tube 23 with heat), thereby firmly fixing the plurality of heat transfer tubes 23 to the expansion valve side header 21.

[0032] One end of a heat transfer tube 23 connected to a corresponding upper heat transfer tube through-hole 67 is disposed in each upper insertion space 68. Meanwhile, one end of each of two heat transfer tubes 23 connected to the two lowest heat transfer tube through-holes 54 is disposed in the lowest insertion space 53. By disposing the ends of the heat transfer tubes 23 in the insertion spaces 46, the insertion spaces 46 communicate with the flow paths 33 formed inside each heat transfer tube 23.

[0033] 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 passages 57 and the multiple insertion spaces 46. The multiple insertion spaces 46 and the first flow passages 57 are connected by the multiple introduction holes 62.

[0034] In this embodiment, the seven introduction holes 62 from the top are upper introduction holes 65, and the remaining one is a bottom-most introduction hole 64 (first introduction flow path). The bottom-most introduction hole 64 is disposed below the multiple upper introduction holes 65. The lower end region 59 of the first flow path 57 and the bottom-most insertion space 53 are connected by the bottom-most introduction hole 64. The first flow path 57 and the multiple upper insertion spaces 68 are connected by the multiple upper introduction holes 65.

[0035] The cross-sectional flow path area of ​​the plurality of upper inlet holes 65 increases as the inlet hole is positioned higher. The cross-sectional flow path area of ​​the lowest inlet hole 64 is smaller than the cross-sectional flow path area of ​​the second inlet hole 66 (second inlet flow path) that is positioned lowest among the plurality of upper inlet holes 65.

[0036] The surfaces of each of the multiple plate-like members 71-76 are coated with brazing material, and the plate-like members are stacked and heated in a furnace, melting the brazing material and joining them together to form the expansion valve side header 21. In this case, when it is desired to change the cross-sectional area of ​​a portion of the refrigerant flow path of the expansion valve side header 21 in accordance with a change in the type of refrigerant used, this can be accommodated by simply changing the plate-like member that covers that portion. This improves the design flexibility of the outdoor heat exchanger 1, including the expansion valve side header 21, and reduces development and manufacturing costs.

[0037] For example, the outdoor heat exchanger 1 can easily adjust the volumes of the first turn-back flow path 51 and the second turn-back flow path 52 by changing the number of the plurality of turn-back flow path plate-shaped members 74, without changing the shapes of the first turn-back flow path holes 81 and the second turn-back flow path holes 82 of the plurality of turn-back flow path plate-shaped members 74. The outdoor heat exchanger 1 can easily adjust the volumes of the first flow path 57 and the second flow path 58 by changing the number of the plurality of circulation flow path plate-shaped members 73, without changing the shapes of the first flow path holes 84 and the second flow path holes 85 of the plurality of circulation flow path plate-shaped members 73. The outdoor heat exchanger 1 can easily adjust the volumes of the plurality of insertion spaces 46 by changing the number of the plurality of insertion space plate-shaped members 75, without changing the shapes of the plurality of insertion space holes 87 of the plurality of insertion space plate-shaped members 75.

[0038] The air conditioner 10 can perform heating and cooling operations as described below. [Heating operation] The heating operation is performed, for example, when the air conditioner 10 is operated by a user to perform the heating operation. When the air conditioner 10 performs the 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 into the discharge pipe 12. The high-pressure gas-phase refrigerant discharged into the discharge pipe 12 flows into the indoor heat exchanger 7 via the four-way valve 6 because the refrigerant circuit 4 has been switched to the heating cycle.

[0039] 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.

[0040] Expansion valve 8 reduces the pressure of the high-pressure liquid-phase refrigerant that has flowed into expansion valve 8. The high-pressure liquid-phase refrigerant is reduced in pressure by expansion valve 8 and becomes a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant flows out of expansion valve 8 and flows into refrigerant piping 17. Outdoor fan 18 flows outdoor air into ventilation space 19.

[0041] 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 passage 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 toward the other end 42 in the header longitudinal direction 25 and rises along the first flow passage 57. At this time, the refrigerant is diverted from the first flow passage 57 to each of the introduction holes 62. The remaining gas-liquid two-phase refrigerant that has flowed through the first flow passage 57 and reached the upper end region 60 of the first flow passage 57 (other than the diverted refrigerant that has flowed into each of the introduction holes 62) flows into the second flow passage 58 through the first return flow passage 51. The low-pressure gas-liquid two-phase refrigerant that has flowed into the second flow passage 58 descends along the second flow passage 58.

[0042] The liquid refrigerant of the low-pressure gas-liquid two-phase refrigerant that has descended along the second flow path 58 flows from the second flow path 58 into the lower end region 59 of the first flow path 57 via the second turning flow path 52. The liquid refrigerant that has flowed into the lower end region 59 via the second turning flow path 52 rises along the first flow path 57 together with the low-pressure gas-liquid two-phase refrigerant that has flowed into the lower end region 59 via the inlet 61. That is, during heating operation, the low-pressure gas-liquid two-phase refrigerant that has flowed into the circulation flow path 45 circulates through the circulation flow path 45. Circulating the low-pressure gas-liquid two-phase refrigerant through the circulation flow path 45 suppresses imbalance of the liquid refrigerant of the low-pressure gas-liquid two-phase refrigerant in the circulation flow path 45.

[0043] The low-pressure gas-liquid two-phase refrigerant flowing upward along the first flow path 57 flows into each of the insertion spaces 46 via the multiple introduction holes 62. At this time, the liquid refrigerant of the low-pressure gas-liquid two-phase refrigerant rising along the first flow path 57 is pushed toward the four corners of the first flow path 57 by gas refrigerant, which has a lower specific gravity than the liquid refrigerant, flowing through the center of the first flow path 57, and then flows through these four corners and rises up the first flow path 57. As a result, some of the liquid refrigerant flows into and stagnates in an upper end region 60 of the first flow path 57 without being diverted to the multiple insertion spaces 46. When the low-pressure gas-liquid two-phase refrigerant rises along the first flow path 57, when the refrigerant circulation rate in the refrigerant circuit 4 is high and a large amount of refrigerant flows into the expansion valve side header 21, the amount of liquid refrigerant of the low-pressure gas-liquid two-phase refrigerant stagnates in the upper end region 60 of the first flow path 57 more than when the refrigerant circulation rate is low and a small amount of refrigerant flows into the expansion valve side header 21. That is, the amount of liquid refrigerant stagnating in the upper end region 60 of the first flow path 57 increases in proportion to the amount of refrigerant flowing into the expansion valve side header 21. In the expansion valve side header 21 of this embodiment, the liquid refrigerant that reaches the upper end region 60 of the first flow path 57 flows through the first return flow path 51 to the second flow path 58, and then flows from the second flow path 58 through the second return flow path 52 to the first flow path 57 again. That is, while the liquid refrigerant is circulated between the first flow path 57 and the second flow path 58, the refrigerant is diverted from the first flow path 57 to each heat transfer tube 23 through the introduction holes 62 and the insertion spaces 46. Therefore, it is possible to prevent the liquid refrigerant from stagnating in the upper end region 60 of the first flow path 57 inside the expansion valve side header 21, and therefore it is possible to prevent the refrigerant from drifting from the expansion valve side header 21 to each heat transfer tube 23 due to the liquid refrigerant stagnating in the expansion valve side header 21.

[0044] The low-pressure gas-liquid two-phase refrigerant flows through the first flow path 57 from bottom to top and into each of the inlet holes 62. Therefore, in the first flow path 57, the flow rate of the low-pressure gas-liquid two-phase refrigerant decreases toward the upper side in the header longitudinal direction 25. Furthermore, in the expansion valve side header 21, as in this embodiment, the smaller the refrigerant circulation rate of the low-pressure gas-liquid two-phase refrigerant circulating through the circulation flow path 45, the smaller the flow velocity of the low-pressure gas-liquid two-phase refrigerant flowing into the first flow path 57 through the inlet 61. This makes it more difficult for the liquid refrigerant in the low-pressure gas-liquid two-phase refrigerant to reach the upper side of the first flow path 57, and the liquid refrigerant accumulates below the first flow path 57. At this time, the flow rate of the liquid refrigerant flowing from the first flow path 57 into the multiple insertion spaces 46 through the multiple inlet holes 62 decreases toward the upper side and increases toward the lower side. This causes uneven flow of the liquid refrigerant flowing through the heat transfer tubes 23.

[0045] In the expansion valve-side header 21 of this embodiment, the flow path cross-sectional areas of the multiple inlet holes 62 are increased toward the upper side, so that the flow path resistance of the multiple inlet holes 62 decreases toward the upper side. Therefore, when the refrigerant flows upward through the first flow paths 57 and is diverted into each insertion space 46, the resistance the refrigerant encounters as it flows into each insertion space 46 decreases toward the upper side. As a result, the amount of refrigerant flowing from a lower inlet hole 62 to the corresponding insertion space 46 is smaller than the amount of refrigerant flowing from the immediately upper inlet hole 62 to the corresponding insertion space 46. In other words, the amount of low-pressure gas-liquid two-phase refrigerant flowing from each inlet hole 62 to each inlet hole 62 increases toward the upper side. Therefore, even when the flow rate of liquid refrigerant ascending along the first flow paths 57 described above is unevenly distributed so that it becomes smaller toward the upper side, the uneven distribution of liquid refrigerant among the heat transfer tubes 23 is reduced and the amounts of liquid refrigerant are generally equalized.

[0046] The refrigerant flowing in from the refrigerant piping through-hole 44 and the refrigerant flowing in from the second return flow path 52 combine in the lower end region 59 of the first flow path 57, and the refrigerant flows in through the inlet 61. As a result, the flow rate of the low-pressure gas-liquid two-phase refrigerant flowing in the lower end region 59 of the first flow path 57 is greater than the flow rate of the low-pressure gas-liquid two-phase refrigerant flowing in the first flow path 57 other than the lower end region 59. Therefore, the flow rate of the low-pressure gas-liquid two-phase refrigerant flowing into the lowest-stage insertion space 53 is greater than the flow rate of the low-pressure gas-liquid two-phase refrigerant flowing into the plurality of upper insertion spaces 68. Furthermore, if the low-pressure gas-liquid two-phase refrigerant that has flowed into the lowest-stage insertion space 53 is directed to one heat transfer tube, the flow rate of the low-pressure gas-liquid two-phase refrigerant flowing through this one heat transfer tube may be greater than the flow rates of the low-pressure gas-liquid two-phase refrigerant flowing in the other heat transfer tubes.

[0047] By inserting the lower two heat transfer tubes of the plurality of heat transfer tubes 23 into the lowest stage insertion space 53, the low-pressure gas-liquid two-phase refrigerant that flows into the lowest stage insertion space 53 is diverted to the two lower heat transfer tubes and flows into the plurality of flow paths 33 of the two lower heat transfer tubes. As a result, even when the flow rate of the low-pressure gas-liquid two-phase refrigerant flowing into the lowest stage insertion space 53 is high, the flow rate of the low-pressure gas-liquid two-phase refrigerant flowing through each of the two lower heat transfer tubes connected to the lowest stage insertion space 53 approaches the flow rate of the low-pressure gas-liquid two-phase refrigerant flowing through the other heat transfer tubes, improving the divergence of the low-pressure gas-liquid two-phase refrigerant among the plurality of heat transfer tubes 23.

[0048] The low-pressure gas-liquid two-phase refrigerant that has flowed into the multiple insertion spaces 46 flows into the multiple flow paths 33 formed inside the multiple heat transfer tubes 23 and flows toward the compressor-side header 22. The low-pressure gas-liquid two-phase refrigerant flowing through the multiple heat transfer tubes 23 exchanges heat with the air flowing through the ventilation space 19, is heated, and evaporates, becoming low-pressure gas-phase refrigerant. In other words, the outdoor heat exchanger 1 functions as an evaporator when the air conditioner 10 performs heating operation. The outdoor heat exchanger 1 of this embodiment can suppress uneven flow of the liquid refrigerant among the multiple low-pressure gas-liquid two-phase refrigerants flowing through the multiple heat transfer tubes 23. In other words, the heat exchange performance is improved by improving the separation of the refrigerant flow in each heat transfer tube 23. The low-pressure gas-phase refrigerant flows out of the multiple heat transfer tubes 23 and merges in 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, it flows into the suction pipe 11 of the compressor 5 via the four-way valve 6.

[0049] [Cooling operation] When the air conditioner 10 is operated by a user 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.

[0050] 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, condenses, and becomes 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 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 merges in the first flow path 57 flows into the refrigerant pipe 17 through the inlet 61, the inlet space 43, and the refrigerant pipe through-hole 44, flows through the refrigerant pipe 17, and flows into the expansion valve 8.

[0051] The high-pressure liquid-phase refrigerant that flows into the expansion valve 8 is decompressed to become a low-pressure two-phase gas-liquid 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 two-phase gas-liquid refrigerant that flows into the indoor heat exchanger 7 exchanges heat with room air drawn into the indoor unit 3 by the rotation of the indoor fan (not shown). As a result, the air passing through the indoor heat exchanger 7 is cooled by the low-pressure two-phase gas-liquid refrigerant that flows into 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 two-phase gas-liquid 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.

[0052] [Heat exchanger of comparative example 1] As shown in Fig. 6, the expansion valve side header 100 of the heat exchanger of Comparative Example 1 has a configuration in which the first return flow path 51 and the second return flow path 52 of the expansion valve side header 21 of the outdoor heat exchanger 1 of the previously described embodiment are replaced with a first return flow path 101 and a second return flow path 102, respectively, and the other parts are the same as the previously described expansion valve side header 21. Fig. 6 is an exploded perspective view showing the expansion valve side header 100 of the heat exchanger of Comparative Example 1. The first return flow path 101 is arranged downstream in the introduction direction 48 of the upper ends of the first flow path 57 and the second flow path 58. The second return flow path 102 is arranged downstream in the introduction direction 48 of the lower ends of the first flow path 57 and the second flow path 58.

[0053] The heat exchanger of Comparative Example 1 functions in the same manner as the outdoor heat exchanger 1 of the above-described embodiment. That is, when the heat exchanger of Comparative Example 1 functions as an evaporator, the low-pressure gas-liquid two-phase refrigerant that flows from the inlet space 43 into the first flow path 57 via the inlet 61 circulates through the first flow path 57, the first return flow path 101, the second flow path 58, and the second return flow path 102.

[0054] In the expansion valve-side header 100 of the heat exchanger of Comparative Example 1, a first turn-back flow path 101 is formed downstream of the upper end region 60 of the first flow path 57 in the introduction direction 48 (the arrangement is reversed from the arrangement of the upper end region 60 of the first flow path 57 and the first turn-back flow path 51 in the expansion valve-side header 21 of the example of the present application). If a top-level insertion space 55 (depicted by a dashed line in FIG. 6 ) were provided at a position corresponding to the first turn-back flow path 101, the top-level insertion space 55 would communicate with the first turn-back flow path 101, and a heat transfer tube 23 would also be joined to this top-level insertion space 55 via the heat transfer tube through-hole 47, the refrigerant that flows from the upper end region 60 of the first flow path 57 into the first turn-back flow path 101 would flow directly into the top-level insertion space 55, reducing the amount of refrigerant that turns back to the second flow path 58, and more refrigerant would flow into the heat transfer tube 23 joined to the top-level insertion space 55. That is, the refrigerant flows unevenly in the plurality of heat transfer tubes 23. Therefore, in order to prevent the refrigerant from flowing unevenly in the plurality of heat transfer tubes 23, it is preferable not to provide the uppermost step insertion space 55.

[0055] However, when the top step insertion space 55 is not provided as in the heat exchanger of Comparative Example 1, when the length of the expansion valve side header 100 in the header longitudinal direction 25 is equal to the length of the expansion valve side header 21 in the header longitudinal direction 25 described above, the number of heat transfer tubes 23 is smaller than in the expansion valve side header 21 provided with the top step insertion space 55, and therefore the heat exchange amount in the outdoor heat exchanger 1 is reduced.

[0056] In the outdoor heat exchanger 1 of this embodiment, unlike the above-described comparative example 1, the first turn flow path 51 and the first flow path 57 (upper end region 60) are arranged in this order in the introduction direction 48. Therefore, the refrigerant flowing into the first turn flow path 51 and the refrigerant flowing into the top stage insertion space 55 are separated at the first flow path 57, and therefore, even if the top stage insertion space 55 is provided, the refrigerant does not drift toward the heat transfer tubes 23 joined to the top stage insertion space 55. This means that the number of heat transfer tubes 23 is not reduced as in the heat exchanger of comparative example 1, and the heat exchange capacity can be ensured.

[0057] [Heat exchanger of comparative example 2] The heat exchanger of Comparative Example 2 includes a compressor-side header 22, a plurality of heat transfer tubes 23, and a plurality of fins 24, similar to the outdoor heat exchanger 1 of the previously described embodiment. However, as shown in FIG. 7 , the first return flow path 51 of the expansion valve-side header 21 of the outdoor heat exchanger 1 of the previously described embodiment is replaced with another first return flow path 111. FIG. 7 is an exploded perspective view showing the first return flow path 111 of the heat exchanger of Comparative Example 2. The first return flow path 111 is arranged on the side (upper side) of the other end 42 of the first flow path 57 and the second flow path 58 in the header longitudinal direction 25, and is aligned with the first flow path 57 and the second flow path 58 in the header longitudinal direction 25. The heat exchanger of Comparative Example 2 functions similarly to the outdoor heat exchanger 1 of the previously described embodiment.

[0058] In the expansion valve-side header of the heat exchanger of Comparative Example 2, the first turn-back flow path 111 is arranged above the first flow path 57 and the second flow path 58, and therefore it is necessary to ensure a region where the first turn-back flow path 111 is formed above the first flow path 57 and the second flow path 58, and therefore it is necessary to make the length in the header longitudinal direction 25 longer than the expansion valve-side header 21 of the outdoor heat exchanger 1 of the previously described embodiment. In contrast, in the outdoor heat exchanger 1 of the previously described embodiment, the first turn-back flow path 51 is arranged side by side with the upper end region 60 of the first flow path 57 in the introduction direction 48, and therefore it is not necessary to ensure a region where the first turn-back flow path 111 is formed above the first flow path 57 and the second flow path 58. Therefore, compared to the expansion valve side header of Comparative Example 2, the outdoor heat exchanger 1 of the above-described embodiment can have a shorter length in the header longitudinal direction 25 without reducing the number of heat transfer tubes 23, or can have a larger number of heat transfer tubes 23 provided per length in the header longitudinal direction 25 of the expansion valve side header 21.

[0059] [Effects of the outdoor heat exchanger 1 of the embodiment] The outdoor heat exchanger 1 of the embodiment includes a plurality of heat transfer tubes 23 and an expansion valve side header 21 that distributes refrigerant to the plurality of heat transfer tubes 23. The plurality of heat transfer tubes 23 are arranged side by side in the header longitudinal direction 25. The expansion valve side header 21 includes a first flow path 57, a second flow path 58, a first return flow path 51, a second return flow path 52, and a plurality of insertion spaces 46 therein. The first flow path 57 allows refrigerant to flow from one end 41 side to the other end 42 side 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. One end of each of the heat transfer tubes 23 is disposed in each of the insertion spaces 46. The insertion spaces 46 guide the refrigerant introduced from the first flow path 57 to the heat transfer tubes 23. The first flow path 57 and the second flow path 58 are disposed between the insertion spaces 46 and the first turning flow path 51 and the second turning flow path 52 in an introduction direction 48 in which the refrigerant is guided from the first flow path 57 to the heat transfer tubes 23.

[0060] The outdoor heat exchanger 1 of the embodiment can cause the refrigerant to flow from the upper end region 60 of the first flow path 57 into the top-stage insertion space 55 that is aligned with the first return flow path 51 of the multiple insertion spaces 46 in the introducing direction 48. The outdoor heat exchanger 1 of the embodiment can further suppress bias in the flow rate of the refrigerant flowing from the upper end region 60 of the first flow path 57 into the top-stage insertion space 55 and the flow rate of the refrigerant flowing from a lower region of the first flow path 57 that is different from the upper end region 60 into an insertion space that is different from the top-stage insertion space 55 of the multiple insertion spaces 46, thereby suppressing bias in the refrigerant flowing into the multiple heat transfer tubes 23. The outdoor heat exchanger 1 of the embodiment can further suppress bias in the liquid refrigerant flowing into the multiple insertion spaces 46, thereby suppressing bias in the liquid refrigerant flowing into the multiple heat transfer tubes 23. Therefore, the outdoor heat exchanger 1 of the embodiment can improve the distribution of the refrigerant to the plurality of heat transfer tubes 23, and can improve the heat exchange performance of exchanging heat with the refrigerant flowing through the plurality of heat transfer tubes 23. The outdoor heat exchanger 1 of the embodiment can further increase the number of the plurality of heat transfer tubes 23 provided per length in the header longitudinal direction 25 of the expansion valve side header 21, and can improve the heat exchange performance accordingly.

[0061] The expansion valve side header 21 of the outdoor heat exchanger 1 of the embodiment also includes a plurality of plate-like members 71-76 stacked in the introduction direction 48. The plurality of plate-like members 71-76 include a plurality of return flow path plate-like members 74 that form the first return flow path 51 and the second return flow path 52, a plurality of circulation flow path plate-like members 73 that form the first flow path 57 and the second flow path 58, and a plurality of insertion space plate-like members 75 that form the plurality of insertion spaces 46. Because the expansion valve side header 21 is formed by stacking the plurality of plate-like members 71-76 in this way, strength and durability can be improved compared to, for example, a box-shaped header that forms a flow division space inside by combining two members with a U-shaped cross section. Furthermore, in the outdoor heat exchanger 1 of the embodiment, when changing the shapes of the first return flow path 51, the second return flow path 52, the first flow path 57, the second flow path 58, and the multiple insertion spaces 46 formed inside the expansion valve side header 21, this can be accommodated by simply changing the shape of only one of the plate-like members to be changed in each insertion space 46, thereby improving the design freedom of the expansion valve side header 21 and reducing development and manufacturing costs without requiring complex molds or their modifications or additions.

[0062] Furthermore, the flow path cross-sectional area of ​​the first turn flow path 51 is larger than the flow path cross-sectional area of ​​the second turn flow path 52. In this case, the outdoor heat exchanger 1 of the embodiment can reduce the flow path resistance of the first turn flow path 51, and can prevent liquid refrigerant from accumulating at the upper end of the first flow path 57, even during high circulation when the refrigerant circulation amount in the refrigerant circuit 4 is large. By preventing liquid refrigerant from accumulating at the upper end of the first flow path 57, the outdoor heat exchanger 1 of the embodiment can prevent uneven flow of the liquid refrigerant flowing from the first flow path 57 into the plurality of heat transfer tubes 23 via the plurality of insertion spaces 46.

[0063] Furthermore, in the outdoor heat exchanger 1 of the embodiment, the first turn flow path 51 and the second turn flow path 52 are formed in a plurality of turn-back flow path plate-shaped members 74 stacked in the introduction direction 48. In the outdoor heat exchanger 1 of the embodiment, the volumes of the first turn flow path 51 and the second turn flow path 52 can be easily adjusted by changing the number of the plurality of turn-back flow path plate-shaped members 74 without changing the shapes of the first turn flow path holes 81 and the second turn flow path holes 82 of the plurality of turn-back flow path plate-shaped members 74. This improves the degree of freedom in design, allowing the volumes of the first turn flow path 51 and the second turn flow path 52 to be selected depending on the refrigerant circulation rate and the pressure of the refrigerant used in the outdoor unit 2 in which the outdoor heat exchanger 1 is incorporated.

[0064] Incidentally, the expansion valve-side header 21 of the outdoor heat exchanger 1 in the above-described embodiment includes multiple turn-back flow path plate members 74. However, the multiple turn-back flow path plate members 74 may be replaced with a single turn-back flow path plate member. In this case, the volumes of the first turn-back flow path 51 and the second turn-back flow path 52 are adjusted by changing the thickness of the single turn-back flow path plate member or the shapes of the first turn-back flow path holes 81 and the second turn-back flow path holes 82. Even in this case, the heat exchange performance of the outdoor heat exchanger 1 can be improved.

[0065] The expansion valve-side header 21 of the outdoor heat exchanger 1 of the embodiment further includes a plurality of inlet holes 62 therein that introduce the refrigerant from the first flow path 57 into each of the plurality of insertion spaces 46. The flow path cross-sectional area of ​​the plurality of inlet holes 62 increases toward the upper side. Because the refrigerant rising along the first flow path 57 flows into the plurality of insertion spaces 46 through the plurality of inlet holes 62, the flow rate of the refrigerant rising along the first flow path 57 decreases toward the upper side. In the outdoor heat exchanger 1 of the embodiment, the flow path resistance of the plurality of inlet holes 62 can be made smaller toward the upper side. Therefore, even when the flow rate of the refrigerant rising along the first flow path 57 is smaller toward the upper side, the flow rates of the refrigerant flowing into the plurality of insertion spaces 46 can be made equal to each other, and uneven flow of the liquid refrigerant flowing into the plurality of heat transfer tubes 23 can be suppressed.

[0066] Furthermore, the flow path cross-sectional area of ​​the lowest-stage introduction hole 64, which is located closest to the one end 41 among the multiple introduction holes 62 of the outdoor heat exchanger 1 of the embodiment, is smaller than the flow path cross-sectional area of ​​the second introduction hole 66, which is located second from the one end 41 among the multiple introduction holes 62. In the outdoor heat exchanger 1 of the embodiment, the flow path resistance of the lowest-stage introduction hole 64 can be made larger than the flow path resistance of the second introduction hole 66. Therefore, in the outdoor heat exchanger 1 of the embodiment, even when the flow rate of the refrigerant flowing through the lower end region 59 of the first flow path 57 is large, the flow rate of the refrigerant flowing into the lowest-stage insertion space 53 can be made smaller, and the flow rate of the refrigerant flowing into the lowest-stage insertion space 53 can be made closer to the flow rate of the refrigerant flowing into each of the multiple upper introduction holes 65. In the outdoor heat exchanger 1 of the embodiment, the flow rate of the refrigerant flowing into the lowest-stage insertion space 53 is close to the flow rate of the refrigerant flowing into each of the multiple upper inlet holes 65, thereby suppressing the uneven flow of the liquid refrigerant flowing into the multiple heat transfer tubes 23.

[0067] Although the multiple inlet holes 62 of the outdoor heat exchanger 1 in the above-described embodiment are formed so that the flow path cross-sectional area increases toward the upper side, they may also be formed so that the flow path cross-sectional area does not increase toward the upper side. For example, the multiple inlet holes 62 may be formed so that the flow path cross-sectional areas are equal to each other. Even in this case, the outdoor heat exchanger 1 can suppress uneven flow of liquid refrigerant into each heat transfer tube 23 and improve heat exchange performance by arranging the first flow path 57 and the second flow path 58 between the multiple insertion spaces 46 and the first return flow path 51 and the second return flow path 52.

[0068] Furthermore, the expansion valve-side header 21 of the outdoor heat exchanger 1 of the embodiment further includes an inlet 61 therein for allowing refrigerant to flow into the end of the first flow path 57 on the side of one end 41. One ends of two of the plurality of heat transfer tubes 23 are disposed in the lowest-stage insertion space 53, which is disposed closest to the one end 41 of the plurality of insertion spaces 46. In the outdoor heat exchanger 1 of the embodiment, even when the flow rate of refrigerant flowing into the lowest-stage insertion space 53 is high, the liquid refrigerant does not flow directly into the lowest-stage insertion space 53 from the inlet 61, but flows from the first flow path 57 through the lowest-stage introduction hole 64 into the lowest-stage insertion space 53, and is then diverted to the two heat transfer tubes inserted into the lowest-stage introduction hole 64, thereby suppressing uneven flow of the liquid refrigerant flowing into the plurality of heat transfer tubes 23.

[0069] Although one ends of two heat transfer tubes are inserted into the lowest-stage insertion space 53 of the outdoor heat exchanger 1 in the above-described embodiment, one ends of three or more heat transfer tubes may be inserted when the degree of refrigerant flow deviation toward the lower heat transfer tubes is large. Furthermore, when the flow rate of the refrigerant flowing into the lowest-stage insertion space 53 is approximately equal to the flow rate of the refrigerant flowing into the plurality of upper insertion spaces 68, one end of only one heat transfer tube may be inserted into the lowest-stage insertion space 53. In this way, the required heat exchange performance can be ensured by increasing or decreasing the number of heat transfer tubes inserted into the lowest-stage insertion space 53 depending on the degree of refrigerant flow deviation toward the lower heat transfer tubes.

[0070] Furthermore, in the outdoor heat exchanger 1 of the embodiment, the multiple insertion spaces 46 are formed from the multiple insertion space plate-shaped members 75 stacked in the introduction direction 48. In the outdoor heat exchanger 1 of the embodiment, the volume of the multiple insertion spaces 46 can be easily adjusted by changing the number of the multiple insertion space plate-shaped members 75 without changing the shapes of the multiple insertion space holes 87 of the multiple insertion space plate-shaped members 75.

[0071] The expansion valve-side header 21 of the outdoor heat exchanger 1 of the previously described embodiment includes a plurality of insertion space plate-like members 75. The number of insertion space plate-like members 75 can be adjusted depending on the length by which the tips of the heat transfer tubes 23 arranged in each insertion space protrude upstream in the introduction direction 48. As described above, the heat transfer tube-side plate-like member 72 is formed with a burring (not shown), which protrudes upstream in the introduction direction 48. The protruding length of the burring is set according to the strength required to join the heat transfer tubes 23, and therefore varies depending on the shape of the heat transfer tubes 23. In this case, if the tips of the heat transfer tubes 23 joined to the burring are close to the introduction hole, the refrigerant flowing from the introduction hole into the insertion space may not flow evenly through each flow path 33 of the heat transfer tube 23. In the present invention, by changing the number of plate-like members 75 for insertion spaces according to the above-mentioned protruding dimension, it is easy to set the dimension between the tip of the heat transfer tube 23 and the introduction hole to an appropriate value, so that the liquid refrigerant that flows into each insertion space can flow evenly to each flow path 33 of the heat transfer tube.

[0072] Furthermore, the first flow path 57 and the second flow path 58 are formed from a plurality of circulation flow path plate-shaped members 73 stacked in the introduction direction 48 of the outdoor heat exchanger 1 of the embodiment. In the outdoor heat exchanger 1 of the embodiment, the volumes of the first flow path 57 and the second flow path 58 can be easily adjusted by changing the number of the plurality of circulation flow path plate-shaped members 73 without changing the shapes of the first flow path holes 84 and the second flow path holes 85 of the plurality of circulation flow path plate-shaped members 73.

[0073] Incidentally, the expansion valve-side header 21 of the outdoor heat exchanger 1 in the above-described embodiment includes multiple circulation path plate-shaped members 73. However, the multiple circulation path plate-shaped members 73 may be replaced with a single circulation path plate-shaped member. In this case, the volumes of the first flow paths 57 and the second flow paths 58 are adjusted by changing the thickness of the single circulation path plate-shaped member or the shapes of the first flow path holes 84 and the second flow path holes 85. Even in this case, the outdoor heat exchanger 1 can improve its heat exchange performance by arranging the first flow paths 57 and the second flow paths 58 between the multiple insertion spaces 46 and the first return flow paths 51 and the second return flow paths 52.

[0074] Incidentally, the expansion valve side header 21 of the outdoor heat exchanger 1 in the above-described embodiment is formed by stacking multiple plate-like members 71-76, but it may also be formed without using multiple stacked plate-like members 71-76. For example, the expansion valve side header 21 may be formed using a 3D printer. Even in this case, the outdoor heat exchanger 1 can improve its heat exchange performance by arranging the first flow path 57 and the second flow path 58 between the multiple insertion spaces 46 and the first return flow path 51 and the second return flow path 52.

[0075] 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 so-called equivalent range. 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 without departing from the spirit of the embodiments. [Explanation of symbols]

[0076] 1: Outdoor heat exchanger (heat exchanger) 21: Expansion valve side header (header) 22: Compressor side header 23: Multiple heat transfer tubes 24: Multiple fins 25: Header longitudinal direction (longitudinal direction) 41:One end 42:Other end 43:Inflow space 46: Multiple insertion spaces 48: Introduction direction 51: First return flow path 52: Second return flow path 53: Bottom insert space 57: First flow path 58: Second flow path 61:Inlet 62: Multiple inlet holes 64: lowest inlet (first inlet flow path) 66: Second inlet (second inlet flow path) 73: A plurality of plate-shaped members for circulation flow paths 74: A plurality of plate-shaped members for return flow paths 75: A plurality of plate-shaped members for insertion spaces 76: Plate-shaped member for introduction hole

Claims

1. A plurality of heat transfer tubes; a header for dividing the refrigerant into the plurality of heat transfer tubes, The plurality of heat transfer tubes are arranged side by side in the longitudinal direction of the header, The header has therein: a first flow path through which a refrigerant flows from one end side to the other end side in the longitudinal direction of the header; a second flow path through which a coolant flows from the other end to the one end; a first return flow path that allows the refrigerant to flow from the first flow path to the second flow path on the other end side; a second return flow path that allows the refrigerant to flow from the second flow path to the first flow path on the side of the one end; a plurality of insertion spaces into which one ends of the plurality of heat transfer tubes are respectively disposed, the plurality of insertion spaces guide the refrigerant guided from at least one of the first flow path and the second flow path to the plurality of heat transfer tubes; The first flow path and the second flow path are disposed between the insertion spaces and the first turning flow path and the second turning flow path in an introduction direction in which the refrigerant is introduced from one of the flow paths to the heat transfer tubes. heat exchanger.

2. the header has a plurality of plate-like members stacked in the introduction direction, The plurality of plate-like members include: a plate-shaped member for forming the first and second return flow paths; a circulation flow path plate-shaped member in which the first flow path and the second flow path are formed; and a plate-shaped member for forming the insertion spaces in which the plurality of insertion spaces are formed. The heat exchanger of claim 1 .

3. The header further includes an inlet therein for allowing the refrigerant to flow into an end of the first flow path on the side of the one end, The cross-sectional area of ​​the first turning flow path is larger than the cross-sectional area of ​​the second turning flow path.

3. The heat exchanger of claim 2.

4. The turn-back flow path plate-shaped member is formed of a plurality of turn-back flow path plate-shaped members stacked in the introduction direction. The heat exchanger according to claim 3.

5. The header further includes a plurality of inlet flow paths that introduce the refrigerant from the one flow path into each of the plurality of insertion spaces, A flow path cross-sectional area of ​​a first introduction flow path among the plurality of introduction flow paths is different from a flow path cross-sectional area of ​​a second introduction flow path among the plurality of introduction flow paths, the second introduction flow path being disposed closer to the one end than the first introduction flow path. The heat exchanger of claim 1 .

6. The plurality of introduction channels communicate the first channel with each of the plurality of insertion spaces, The cross-sectional area of ​​the first inlet flow path is larger than the cross-sectional area of ​​the second inlet flow path.

6. The heat exchanger according to claim 5.

7. A flow path cross-sectional area of ​​a first inlet flow path arranged closest to the one end among the plurality of inlet flow paths is smaller than a flow path cross-sectional area of ​​a second inlet flow path arranged second from the one end among the plurality of inlet flow paths.

7. The heat exchanger of claim 6.

8. The header further includes an inlet therein for allowing the refrigerant to flow into an end of the first flow path on the side of the one end, One ends of two heat transfer tubes among the plurality of heat transfer tubes are placed in the insertion space that is arranged closest to the one end among the plurality of insertion spaces. The heat exchanger of claim 1 .

9. The plate-shaped member for insertion space is formed from a plurality of plate-shaped members for insertion space that are stacked in the insertion direction.

3. The heat exchanger of claim 2.

10. The circulation flow path plate-shaped member is formed of a plurality of circulation flow path plate-shaped members stacked in the introduction direction.

3. The heat exchanger of claim 2.

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