Heat exchanger and method for manufacturing heat exchanger

Abstract

A heat exchanger (1) is provided with: headers (11, 12) having curved sections (16) in a curved shape; a plurality of flat tubes (22) that penetrate partition walls (17) of the headers (11, 12) and are fixed thereto; and fins (23) provided to the outer surfaces of the flat tubes (22). The flat tubes (22) that are adjacent to each other in a direction along the curved shape and are provided to the curved sections (16) are configured such that the interval between side surfaces facing each other is constant in the longitudinal direction (DL) of the shape of the outline of a cross-section perpendicular to the extension direction (DT) of the flat tubes.

Description

Heat exchanger and method for manufacturing a heat exchanger

[0001] The present disclosure relates to a heat exchanger formed by inserting and fixing a flat tube into a through hole of a header having a curved shape, and a method for manufacturing the heat exchanger.

[0002] Conventional heat exchangers are bent and mounted (see, for example, Patent Document 1) inside a compact housing of a target device such as an air conditioner in order to secure a heat transfer area and a front area as large as possible.

[0003] Japanese Patent Application Laid-Open No. 2022-19459

[0004] In the above-described conventional heat exchanger, a curved portion is provided in the header, and a flat tube is inserted and fixed into the opening of the curved portion. The gap between adjacent flat tubes adjacent to the curved portion is provided so as to narrow in the cross-sectional longitudinal direction, which is the air flow direction. As a result, there is a problem that the ventilation resistance of the air flow passing through the curved portion increases, causing an increase in the blowing power and the blowing noise.

[0005] The present disclosure is for solving the above-described problems, and aims to reduce the ventilation resistance of air flowing through a curved portion even in a heat exchanger having a curved portion in a header.

[0006] The heat exchanger according to the present disclosure includes a header having a curved portion having a curved shape, a plurality of flat tubes penetrating and fixed to the partition wall of the header, and fins provided on the outer surface of the flat tubes. When the longitudinal direction of the shape of the contour of the cross section perpendicular to the extending direction of the flat tubes is defined as the cross-sectional longitudinal direction, at least two flat tubes adjacent to each other in the direction along the curved shape provided in the curved portion have a constant interval between the opposing side surfaces in the cross-sectional longitudinal direction.

[0007] In the heat exchanger of the present disclosure, the interval between the side walls of the gas flow path formed between the opposing side surfaces of the adjacent flat tubes provided in the curved portion is constant and is not reduced, so that it has the effect of suppressing an increase in ventilation resistance.

[0008] This is a cross-sectional view of the entire housing housing the heat exchanger shown in Embodiment 1. This is a perspective view of the heat exchanger shown in Embodiment 1. This is a top view of the header used in Embodiment 1. This is a cross-sectional view of the header used in Embodiment 1 along the line U-U. This is a top view of the header used in Embodiment 1 before the bending process. This is a front view of the heat transfer section of the heat exchanger shown in Embodiment 1. This is a cross-sectional view of the flattened tube used in Embodiment 1 along the line W-W. This is a cross-sectional view of the main part of the heat exchanger shown in Embodiment 1 along the line W-W. This is a front view of the heat transfer section of the heat exchanger showing a first modified example of Embodiment 1. This is a top view of the fins used in the first modified example of Embodiment 1. This is a cross-sectional view of the main part of the heat exchanger showing a first modified example of Embodiment 1 along the line V-V. This is a cross-sectional view of the main part of the heat exchanger showing a second modified example of Embodiment 1 along the line V-V. This is a cross-sectional view of the main part of the heat exchanger showing a third modified example of Embodiment 1 along the line V-V. This is a front view of the main part of the curved section 16 of the heat exchanger before the bending process, showing a fourth modified example of Embodiment 1. This is a top view showing a preliminary assembly of a heat exchanger illustrating a fourth modification of Embodiment 1. This is a top view of the header used in the fourth modification of Embodiment 1 before the bending process. This is a top view of the header used in the fourth modification of Embodiment 1. This is a cross-sectional view of the main part of the preliminary assembly of the heat exchanger illustrating a fourth modification of Embodiment 1 at cross-section X-X. This is a front view of the main part of the heat exchanger illustrating a fourth modification of Embodiment 1. This is a top view of the header used in the fifth modification of Embodiment 1. This is a cross-sectional view of the header used in the fifth modification of Embodiment 1 at cross-section Z-Z. This is a cross-sectional view of the main part of the heat exchanger illustrating a fifth modification of Embodiment 1 at cross-section Z-Z. This is a perspective view of the protruding part forming member used in the fifth modification of Embodiment 1. This is a perspective view of the main part of the flattened tube and protruding part forming member used in the fifth modification of Embodiment 1. This is a top view of the flattened tube and protruding part forming member used in the fifth modification of Embodiment 1. This is a perspective view of the L-shaped plate material of the protruding part forming member used in the fifth modification of Embodiment 1. This is a cross-sectional view of the main part at cross-section Z-Z when a flat tube is inserted into the header of a heat exchanger, showing a fifth modified example of Embodiment 1. This is a flowchart showing the manufacturing method of the heat exchanger shown in Embodiment 1.This is a top view showing a preliminary assembly in the heat exchanger manufacturing method of Embodiment 1. This is a flowchart of a first modified example of the heat exchanger manufacturing method of Embodiment 1. This is a flowchart of a second modified example of the heat exchanger manufacturing method of Embodiment 1. This is a top view showing a preliminary assembly in the second modified example of the heat exchanger manufacturing method of Embodiment 1. This is a flowchart of a third modified example of the heat exchanger manufacturing method of Embodiment 1. This is a cross-sectional view of the header used in Embodiment 2 at cross-section V-V. This is a cross-sectional view of the first modified example of the header used in Embodiment 2 at cross-section V-V. This is a cross-sectional view of the second modified example of the header used in Embodiment 2 at cross-section V-V. This is a top view of the header used in the second modified example of Embodiment 2. This is a cross-sectional view of the header used in the second modified example of Embodiment 2 at cross-section Y-Y. This is a cross-sectional view of the header used in the third modified example of Embodiment 2 at cross-section V-V.

[0009] Embodiment 1. The heat exchanger 1 in Embodiment 1 will be described with reference to Figures 1 to 8. The heat exchanger 1 in this embodiment functions as part of a refrigeration cycle. Figure 1 is a cross-sectional view of the entire housing 2 that houses the heat exchanger 1 shown in this embodiment. In this figure, the front side of the paper is referred to as the upper side, the back side as the lower side, the upper side as the right side, the lower side as the left side, the right side as the front, and the left side as the rear.

[0010] The heat exchanger 1 of this embodiment is housed in a casing 2 having the shape of a rectangular parallelepiped. The casing 2 is the casing of an outdoor unit installed outside the room. The outdoor unit has the function of exchanging heat between the outside air and the heat transfer medium of the refrigeration cycle. The heat exchanger 1 has an L-shaped cross-section that follows two sides of the rectangle that forms the bottom surface of the casing 2: the left short side and the rear (left side of the page) long side. The cross-sectional shape of the heat exchanger 1 has a curved portion at the corner between the portion that follows the short side of the rectangle that forms the shape of the casing 2 and the portion that follows the long side.

[0011] The housing 2 has openings on its left and rear sides facing the heat exchanger 1, in which case the heat exchanger 1 is in direct contact with the outside air. The heat exchanger 1 is capable of passing air, which is a gas, from the outside to the inside of the housing 2. The housing 2 houses a blower 3. The housing 2 has an opening on its front side facing the blower 3, in which which the blower 3 is in direct contact with the outside air. When the blower 3 is operated, the air passes through the openings on the left and rear sides of the housing 2 facing the heat exchanger 1, the heat exchanger 1, and the blower 3 in that order. After that, the air is blown out from the opening on the front side of the housing 2 facing the blower 3, in the direction from the rear to the front of the housing 2 (to the right on the page).

[0012] Furthermore, the housing 2 includes a machine room 6. The machine room 6 is separated from the air passage described above by a partition plate 5. The machine room 6 houses components necessary for the operation of the refrigeration cycle, such as a compressor and expansion valve (not shown). The heat exchanger 1 communicates with the components necessary for the operation of the refrigeration cycle housed in the machine room 6. When the blower 3 is operated and the compressor in the machine room 6 is started, the refrigeration cycle is activated, and heat exchange occurs between the heat transfer medium, which is a fluid flowing inside the heat exchanger 1, and the outside air, which is a gas flowing in contact with the outer surface of the heat exchanger 1.

[0013] When the heat exchanger 1 is operated as a condenser in a refrigeration cycle (for example, during cooling operation), a heat transfer medium that is hotter than the air is cooled by the air, undergoing a phase change from gas to liquid and condensing as it flows through the inside of the heat exchanger 1. When the heat exchanger 1 is operated as an evaporator in a refrigeration cycle (for example, during heating operation), a heat transfer medium that is hotter than the air is heated by the air, undergoing a phase change from liquid to gas and evaporating as it flows through the inside of the heat exchanger 1. At this time, if the air is cooled to a temperature lower than the dew point temperature, water vapor undergoes a phase change and condensation occurs on the surface of the heat exchanger 1. If the air is cooled to below freezing point, water vapor undergoes a phase change and frost occurs on the surface of the heat transfer section 21. The drain water generated by condensation or frost melting flows down the outer surface of the heat exchanger 1, reaches the drain pan 4 located below the heat exchanger 1, and is drained.

[0014] Figure 2 is a perspective view of a heat exchanger 1 showing this embodiment. Here, in this disclosure, the orientation of the heat exchanger 1 is expressed as follows: the vertical direction and the horizontal direction of the paper from the viewpoint in Figure 2 are referred to as the vertical direction and the horizontal direction of the heat exchanger 1, respectively. In addition, in the direction along the shorter side of the L-shaped cross-section of the heat exchanger 1, the side closer to the viewer on the paper is referred to as the front side, and the side further away from the viewer on the paper is referred to as the rear side.

[0015] The heat exchanger 1 comprises a first header 11, a heat transfer section 21, and a second header 12. In this disclosure, a member having an overall shape of a hollow, elongated rod, with multiple through holes 13 arranged in a row that open in one direction for inserting and fixing a flat pipe, is referred to as a header. The first header 11 and the second header 12 are connected by piping (not shown) to components necessary for the operation of the refrigeration cycle, such as a compressor, housed in the machine room 6. In this embodiment, it is preferable that the piping connecting the first header 11 and the second header 12 to the components housed in the machine room 6 is provided on the right side of the first header 11 and the second header 12. In this disclosure, the position of the piping is not limited.

[0016] The heat transfer section 21 comprises a plurality of hollow flat tubes and a plurality of fins provided on the outer surface of the flat tubes to conduct heat. The flat tubes communicate with the first header 11 and the second header 12, respectively. The flat tubes extend in the extending direction DT. In this figure, the extending direction DT of the flat tubes is the vertical direction. The heat transfer medium of the refrigeration cycle can flow in the order of the first header 11, the flat tubes, and the second header 12, or in the reverse order. Alternatively, by appropriately partitioning the inside of the first header 11 and the second header 12, the heat transfer medium may be divided into predetermined numbers and folded back to form a flow path, rather than flowing in parallel through all the flat tubes. The heat transfer section 21 has a central portion 19 in the middle of the extending direction DT of the flat tubes. The central portion 19 here refers to the portion of the flat tube 22 that excludes the ends where the local airflow rate is small, out of the length of the extending direction DT. More specifically, the central portion 19 here refers to the central 80 percent of the length of the flattened pipe 22, after subtracting 10 percent of the length at each end, assuming that the portion exposed from the header is 100 percent of the length in the extending direction DT of the pipe.

[0017] The technical features of this disclosure will be explained in detail below by describing the structure of the second header 12. Figure 3 is a top view of the second header 12 of the heat exchanger 1 showing this embodiment. The second header 12 is a hollow rod-shaped object. In this figure, the front side of the paper is referred to as the upper side, the back side as the lower side, the upper side as the right side, the lower side as the left side, the right side as the front, and the left side as the rear. As described above, the heat exchanger 1 has an L-shaped cross-section and includes a portion with a curved cross-section at the corner between the short side and the long side. The second header 12 is provided at the bottom of the heat exchanger 1 and has an L-shaped cross-section and a curved corner. The straight portion on the short side of the second header 12 is referred to as the first straight portion 14, the straight portion on the long side as the second straight portion 15, and the portion with a curved shape that connects the first straight portion 14 and the second straight portion 15 is referred to as the curved portion 16.

[0018] The second header 12 is provided with a plurality of through holes 13. The through holes 13 penetrate the upper partition wall 17 of the second header 12 and are provided to open in one direction vertically upward, communicating with the hollow portion of the second header 12. Both ends of the second header 12 are closed by the partition wall 17. A pipe (not shown) is provided in the partition wall 17 at the right end of the second straight section 15, and communicates with components necessary for the operation of the refrigeration cycle, such as a compressor, housed in the machine room 6. However, the position of the pipe connecting the second header 12 and the components necessary for the operation of the refrigeration cycle, such as a compressor, housed in the machine room 6 is not limited to this position.

[0019] In this disclosure, the shape of the curved portion 16 is represented by two arc-shaped contours of the second header 12 of the curved portion 16 in this figure. The two arc-shaped contours of the second header 12 of the curved portion 16 in this figure are arcs with the same center of curvature O, different radii of curvature, and a central angle of 90°. Here, the smaller of the two arcs constituting the contour of the curved portion 16 is referred to as the inner radius of curvature RI, and the larger of the two arcs is referred to as the outer radius of curvature RO. The side of the arc constituting the contour of the curved portion 16 that has the inner radius of curvature RI is referred to as the inner side, and the side that has the outer radius of curvature RO is referred to as the outer side. The inner arc of the curved portion 16 connects to the right-hand contour of the first straight portion 14 (upper side of the paper) and the front side of the second straight portion 15 (right side of the paper). The outer arc of the curved section 16 connects to the left contour of the first straight section 14 (bottom of the paper) and the rear side of the second straight section 15 (left of the paper). Also, the side of the curved section 16 that is closer to the center of curvature O is the inner circumference, and the side that is farther away is the outer circumference.

[0020] Furthermore, the outer and inner circular arcs that constitute the contour of the curved portion 16 do not necessarily have the same center of curvature O. However, the centers of curvature O of both the outer and inner circular arcs are located at a greater distance from the outer circular arc to the inner circular arc when viewed from the outer circular arc to the inner circular arc. In addition, the outer and inner circular arcs that constitute the contour of the curved portion 16 may each be a combination of multiple curves, and the center of curvature O is not necessarily limited to one.

[0021] The through-hole 13 has a rectangular shape as its contour on the surface of the second header 12. More precisely, it is a rectangle with both ends in the longitudinal direction beveled in an arc shape. All the through-holes 13 provided in the first straight section 14 have a longitudinal direction perpendicular to the longitudinal direction of the first straight section 14. Furthermore, all the through-holes 13 provided in the first straight section 14 have the same shape as their contour on the surface of the second header 12. Moreover, all the through-holes 13 provided in the first straight section 14 have straight lines formed by the outer and inner ends of the first straight section 14, which are aligned in the longitudinal direction of the first straight section 14, and these lines are parallel to the longitudinal direction of the first straight section 14.

[0022] Similarly, all through holes 13 provided in the second straight section 15 have a longitudinal direction perpendicular to the longitudinal direction of the second straight section 15. Furthermore, all through holes 13 provided in the second straight section 15 have the same contour shape on the surface of the second header 12. Moreover, all through holes 13 provided in the second straight section 15 have straight lines formed by the outer and inner ends, respectively, aligned in the longitudinal direction of the second straight section 15, which are parallel to the longitudinal direction of the second straight section 15.

[0023] Therefore, in the first straight section 14 and the second straight section 15, the opposing contours of adjacent through holes 13 in the longitudinal direction are all parallel. Also, in the first straight section 14 and the second straight section 15, the distances between the longitudinal contours of adjacent through holes 13 are all equal.

[0024] The curved section 16 is provided with six through holes 13. The shape of these six through holes 13 on the surface of the second header 12 is the same rectangle as the through holes 13 provided in the first straight section 14 and the second straight section 15. Furthermore, the spacing between the contours of adjacent through holes 13 on the surface of the second header 12 in the direction along the curved shape of the curved section 16 is all equal. Moreover, the contours of adjacent through holes 13 in the direction along the curved shape of the curved section 16 that extend in the direction connecting the inner and outer circumferences of the curved section 16 and face each other are all parallel. The centroid C of the shape of the six through holes 13 of the curved section 16 on the surface of the second header 12 lies on a virtual arc-shaped curve LA that is midway between the arc-shaped contours of the inner and outer circumferences of the curved section 16.

[0025] Furthermore, the number of through holes 13 provided in the curved portion 16 is not limited to 6, but can be any number of 2 or more. Also, the spacing between the longitudinal contours of adjacent through holes 13 in the direction along the curved shape of the curved portion 16 does not necessarily have to be equal. Moreover, the arrangement of the centroid C of the shape of the through holes 13 of the curved portion 16 on the surface of the second header 12 in the direction connecting the inner circumference and outer circumference of the curved portion 16 is not limited to being aligned on an arc-shaped curve that is midway between the arc-shaped contours of the inner circumference and the outer circumference.

[0026] Figure 4 is a cross-sectional view of the second header 12 at cross-section U-U, which is a cross-section perpendicular to the longitudinal direction of the second straight section 15. Here, cross-section U-U is at the same position as cross-section U-U shown in Figure 3, and in Figure 3, it is a cross-section at a distance of half the longitudinal length of the second straight section 15 from the right end of the second straight section 15, and does not include the through hole 13. In this embodiment, the second header 12 is provided with a partition wall 17 whose cross-sectional shape at cross-section U-U is square. In the figure, the cross-section of the partition wall 17 is shown with diagonal shading. The partition wall 17 of the second header 12 has a square cross-sectional shape on both its outer and inner surfaces. The second header 12 has a hollow space inside the inner surface of the partition wall 17. Note that the shape of the cross-section perpendicular to the direction along the curved shape of the curved section 16 of the second header 12 is not limited to a square, but may be, for example, a rectangle, circle, ellipse, semicircle, triangle, or polygon.

[0027] Figure 5 is a top view of the second header 12 before the bending process that imparts the curved shape to the curved portion 16. In this disclosure, there are two possible methods for manufacturing the heat exchanger 1 having the curved portion 16. One method for manufacturing the heat exchanger 1 having the curved portion 16 is to insert and fix the flattened pipe 22 into the through-hole 13 of a straight-shaped header to create a flat plate-shaped assembly, and then impart the curved portion 16 by a bending process. The other method for manufacturing the heat exchanger 1 having the curved portion 16 is to insert and fix the flattened pipe 22 into the header having the curved portion 16. In the figure, the second header 12, which has an overall straight shape, is shown when the former of these two methods is used in the manufacturing process of the heat exchanger 1.

[0028] After the bending process, the length of the inner circumference of the curved portion 16 in the direction of the curved shape decreases, while the length of the outer circumference in the direction of the curved shape increases. Consequently, the shape of the upper surface of the curved portion 16 changes from a rectangle to a fan shape. In this embodiment, the longitudinal directions of all through holes 13 in the curved portion 16 after the bending process are parallel. Considering the change in the shape of the upper surface of the curved portion 16 as described above, the through holes 13 in the curved portion 16 before the bending process are arranged such that the spacing between the contours of adjacent through holes 13 narrows from the inner circumference (left side of the paper) to the outer circumference (right side of the paper), as shown in the figure.

[0029] Figure 6 is a front view of the heat transfer section 21 of the heat exchanger 1 according to this embodiment, which includes a flattened tube 22 and fins 23. The fins 23 allow air to pass through in the longitudinal direction of the cross-section perpendicular to the extending direction DT of the adjacent flattened tube 22. The fins 23 have the function of increasing the heat transfer area on the air side of the heat exchanger 1 and promoting heat transfer between the air and the heat transfer medium. The fins 23 are not limited in shape, but it is desirable that they have a shape that can be flexibly deformed in accordance with the change in the arrangement of the flattened tube 22 due to the change in the arrangement of the through holes 13 in the bending process described above, and specifically, wire mesh can be mentioned.

[0030] The flattened tube 22 has no bends or twists throughout its entire length in the extending direction DT and maintains the same cross-sectional shape. Since the length of the flattened tube 22 in the extending direction DT is vertical, as described above, the drain water generated on the surface of the flattened tube 22 and fins 23 due to condensation or frost melting can be guided downward by its own weight along the surface and directed to the drain pan 4 at the bottom of the heat exchanger 1. It is desirable that the fins 23 have a structure that promotes the downward flow of water droplets by gravity and induces capillary force on water droplets in order to move and guide the drain water generated on its surface to the flattened tube 22 as quickly as possible.

[0031] Figure 7 is a cross-sectional view of the flattened pipe 22 used in this embodiment, taken along a cross section W-W perpendicular to the extending direction DT. Here, the cross section W-W is at the same position as the cross section W-W shown in Figure 6, and in Figure 6, it is the cross section at a distance of half the length of the extending direction DT of the flattened pipe 22 from the upper end of the flattened pipe 22. In Figure 7, the extending direction DT of the flattened pipe 22 is not shown, but it is the direction from the back of the paper to the front of the paper. As shown in Figure 7, the shape of the flattened pipe 22 in a cross section perpendicular to the extending direction DT is rectangular and has a longitudinal direction. In this disclosure, the longitudinal direction of the shape of the flattened pipe 22 in a cross section perpendicular to the extending direction DT is referred to as the longitudinal direction DL of the cross section. More precisely, it is a rectangle with both ends of the longitudinal direction DL of the cross section being chamfered in an arc shape. The longitudinal directions of the two sides forming the long side of the rectangle are both parallel to the longitudinal direction DL of the cross section. The holes 41 formed in the cross-section W-W of the flattened pipe 22 are formed in a cross-section perpendicular to the extending direction DT over the entire extending direction DT. Therefore, inside the heat exchanger 1, the heat transfer medium can pass through the flow path formed in the flattened pipe 22 over the extending direction DT, with the holes 41 having a cross-sectional shape perpendicular to the extending direction DT.

[0032] The outer surface of the flattened tube 22 acts as a heat transfer surface with air in the heat transfer section 21 of the heat exchanger 1. The cross-sectional shape of the flattened tube 22 perpendicular to the extending direction DT is rectangular, with the direction in which air passes through the fins 23 by the shortest distance being the longitudinal direction DL of the cross-section. By making the side of the flattened tube 22 that is perpendicular to this direction in which air passes by the shortest distance and has an arrangement that obstructs the airflow the shortest side of the rectangle, it has the effect of not increasing the airflow resistance. Furthermore, by arranging the long axis side of the rectangle along the direction of airflow, it has the effect of securing a heat transfer area without increasing the airflow resistance. In the figure, the flattened tube 22 is provided with six holes 41 having a rectangular or semicircular cross-sectional shape, but the number and shape of the holes 41 in the flattened tube 22 are not limited to those described above.

[0033] Figure 8 is a cross-sectional view of the main part of the cross section W-W, which is a cross-section of the central part 19 in the height direction of the heat exchanger 1 in this embodiment. The cross section W-W here is in the same position as the cross section W-W shown in Figure 6. The main part here refers to all six flattened tubes 22 of the curved section 16, three flattened tubes 22 each from the side closest to the curved section 16 in both the first straight section 14 and the second straight section 15, and the fins 23 provided on those flattened tubes 22. The outline of the second header 12, which is located below (towards the back of the paper) the cross section W-W of the heat exchanger 1, is shown by a dashed line in the figure.

[0034] In the figure, the six flat pipes 22 in the curved section 16, whose longitudinal cross-sectional direction DL is from the upper left to the lower right, have their longitudinal cross-sectional directions DL parallel to each other in the direction along the curved shape of the curved section 16. As described above, the longer side of the rectangular shape of the outline of the flat pipe 22 is parallel to the longitudinal cross-sectional direction DL. Therefore, the longer sides of the rectangular shape of the outlines of the flat pipes 22 provided in the curved section 16 that are adjacent in the direction along the curved shape of the curved section 16 are parallel. In other words, the arrangement of the flat pipes 22 provided in the curved section 16 ensures that the distance between the opposing sides of two flat pipes 22 adjacent in the direction along the curved shape of the curved section 16 of the second header 12 is constant along the longitudinal cross-sectional direction DL.

[0035] In this way, by positioning the flattened pipe 22 in the central part 19 of the extension direction DT of the curved section 16, the airflow path between adjacent flattened pipes 22 is not narrowed, allowing for smooth airflow and reducing ventilation resistance.

[0036] Furthermore, in addition to the features relating to the arrangement of the flattened tubes 22 in the curved section 16 described above, the heat exchanger 1 of this embodiment has the following features relating to the arrangement and dimensions of the flattened tubes 22 and fins 23 in the curved section 16.

[0037] In Figure 8, the flattened tubes 22 of the first straight section 14 and the second straight section 15 are equipped with fins 23a, while the flattened tubes 22 of the curved section 16 are equipped with fins 23b. The width of the flattened tubes 22 of the first straight section 14 and the second straight section 15 in the longitudinal direction DL of the cross-section is greater than the width of the fins 23a. On the other hand, the width of the flattened tubes 22 of the curved section 16 in the longitudinal direction DL of the cross-section is smaller than the width of the fins 23b.

[0038] Therefore, the fins 23b provided on the flattened pipe 22 of the curved section 16 are wider than the fins 23a provided on the flattened pipe 22 of the first straight section 14 and the second straight section 15. In this case, by appropriately designing the wider fin 23b to have a higher density per unit volume than the narrower fin 23a, it is possible to make the airflow resistance of both equal. Specific methods for adjusting the density per unit volume of the fins 23 include, for example, increasing the number of wires per unit volume in the case of wire mesh, or increasing the number of corrugations per unit volume in the case of corrugated fins. In this disclosure, the density per unit volume of the fins 23 is not limited. By making the airflow resistance of the entire heat exchanger 1 equal in this way, it is possible to make the air velocity distribution of the entire heat exchanger 1 closer to uniform, thereby reducing heat transfer loss that occurs when the heat load is uneven.

[0039] The outer ends of the flattened tubes 22 in the curved section 16, along the longitudinal cross-sectional direction DL, are arranged on an arc-shaped curve that follows the curved shape of the curved section 16. In this arrangement of flattened tubes 22, if fins 23 having a width smaller than the width of the longitudinal cross-sectional direction DL of the flattened tubes 22 are provided, then among the multiple holes 41 of the flattened tubes 22, there will be some where fins 23 are not provided on the side walls perpendicular to the longitudinal cross-sectional direction DL. In this case, among the multiple holes 41 of the flattened tubes 22, those with fins 23 on the side walls have an increased heat transfer area on the air side, thus promoting heat transfer. On the other hand, among the multiple holes 41 of the flattened tubes 22, those without fins 23 on the side walls do not have an increased heat transfer area on the air side, so heat transfer is not promoted. Therefore, the presence or absence of fins 23 on the side walls causes an imbalance in heat flux among the multiple holes 41 of the flattened tubes 22, resulting in heat transfer loss.

[0040] In this embodiment, the flattened tube 22 of the curved section 16 is positioned so that one end on either the outer or inner circumference side of the longitudinal cross-section DL follows the curved shape of the curved section 16. The flattened tube 22 of the curved section 16 is provided with fins 23b that are wider than the width of the longitudinal cross-section DL of the flattened tube 22. Therefore, all holes 41 of the flattened tube 22 of the curved section 16 have fins 23b on the side walls perpendicular to the longitudinal cross-section DL.

[0041] By configuring the heat exchanger 1 in this manner, as described above, even if the line connecting the outer ends of the flattened tubes 22 provided in the curved section 16 is not a straight line, the heat flux through the holes 41 of the multiple flattened tubes 22 becomes balanced, which has the effect of reducing heat transfer loss.

[0042] Modification 1. Figure 9 is a front view of the heat transfer section 21 of the heat exchanger 1 shown in this modification. The heat exchanger 1 shown in this modification, like the first embodiment, has an arrangement in which the distance between the opposing sides of two adjacent flat tubes 22 in the direction along the curved shape of the header is constant along the longitudinal direction DL of the cross-section in the provided curved section 16. In this modification, the shape of the fins 23 is limited to corrugated fins, which are formed by bending a long, narrow rectangular sheet of metal into a wave shape. In the figure, the fins 23 provided between the flat tubes 22 are corrugated fins. The corrugated fins are inclined toward the point where they contact the adjacent flat tube 22 in the direction in which the header extends, and have a structure that allows drain water generated on the surface to slide down the inclination and easily flow to the flat tubes 22. This modification is identical to the first embodiment except for the shape of the fins 23.

[0043] Figure 10 is a top view of the fin 23 used in this modified example. The top view here refers to the top view of the fin 23 as seen from the top of the paper (the top of the heat exchanger 1) in the viewpoint of Figure 9. In this figure, the fin 23 is a corrugated fin and has dimensions called fin width WF and fin height HF. The fin width WF refers to the outer dimension of the fin 23 in the heat exchanger 1 in the direction along the longitudinal direction DL of the cross-section of the flattened tube 22. The fin height HF is a dimension in the heat exchanger 1 that is the same as the distance between adjacent flattened tubes in the direction along the curved shape of the curved portion 16 of the second header 12. The fin 23 is equipped with a fin pattern 40 which consists of protrusions and openings for controlling the airflow on the surface and improving heat transfer. In conventional techniques for manufacturing corrugated fins, the fin width WF, fin height HF, and fin pattern 40 are uniquely determined by the specifications of the corrugated fin manufacturing equipment.

[0044] FIG. 11 is a cross-sectional view of a main part at cross-section W-W of the central portion 19 of the flat tube 22 of the heat exchanger 1 showing this modified example. Cross-section W-W here is the same as that shown in FIG. 9. The main part here refers to all six of the curved portions 16, and three flat tubes 22 each from the side closer to the curved portions 16 of both the first straight portion 14 and the second straight portion 15, and the fins 23 provided on those flat tubes 22. The outline of the second header 12 located below (the back side of the paper) of cross-section W-W of the heat exchanger 1 is shown by a broken line in the figure.

[0045] In this figure, the fin 23 represents the cross-section of a thin plate forming a corrugated fin. In this figure, the fin 23 is shown as contacting one of the flat tubes 22 adjacent to the left side in the direction along the curved shape of the curved portion 16 of the second header 12. Here, the corrugated fin is a thin plate bent in a wave shape when viewed from the front of the heat exchanger 1. Therefore, when scanning the cross-section from cross-section W-W in the extending direction DT of the flat tube 22, the cross-section of the thin plate of the fin 23 is not necessarily in contact with the flat tube 22 on the left side, but is located somewhere between the flat tube 22 on the left side and the flat tube 22 on the right side. In this figure, the region where the cross-section of the thin plate of the fin 23 is located at an arbitrary position in the central portion 19 of the flat tube 22 is referred to as the fin cross-section appearance region AF, and is represented by a rectangle surrounded by a broken line. The corrugated fin has a fin width WF which is the width in the direction along the cross-section longitudinal direction DL of the fin cross-section appearance region AF, and a fin height TF which is the width in the direction perpendicular to the cross-section longitudinal direction DL.

[0046] The heat exchanger 1 of this modified example has the following features regarding the form of the fin 23 in addition to the features regarding the arrangement of the flat tubes 22 of the above-described curved portion 16 and the features regarding the arrangement and dimensions of the flat tubes 22 and fins 23 of the curved portion 16.

[0047] In this figure, in all the fins 23 provided on the flat tubes 22 of the first straight portion 14, the second straight portion 15, and the curved portion 16 including the omitted portions, the form is a corrugated fin, the fin width WF is the same, and the fin height HF is the same. Also, although not shown in this figure, the fin pattern 40 of all the fins 23 is the same.

[0048] By configuring the heat exchanger 1 in this way, the local ventilation resistance of the fins 23 becomes equal throughout the heat exchanger 1. As a result, the wind speed distribution for each fin can be made closer to being uniform, allowing the air to spread evenly throughout the heat exchanger 1, and it becomes possible to enhance the efficiency of heat exchange. Also, it becomes possible to manufacture the heat exchanger 1 of the present embodiment using a manufacturing apparatus for corrugated fins of one specification, and compared with the case of using corrugated fins of multiple specifications, resource savings of the manufacturing apparatus becomes possible.

[0049] In this figure, fins 23 are provided on side walls in a direction perpendicular to the cross-sectional longitudinal direction DL of the holes 41 of all the flat tubes 22 provided in the curved portion 16, such that the fins 23 having a width larger than the width of the flat tube 22 in the cross-sectional longitudinal direction DL of the flat tube 22 are provided on the flat tube 22. This modified example does not necessarily have to have the features regarding the arrangement and dimensions of the flat tube 22 and the fins 23 of the curved portion 16 described herein.

[0050] Modified Example 2. FIG. 12 is a cross-sectional view of a main part at the cross-section W-W which is a cross-section at the central portion 19 of the flat tube 22 of the heat exchanger 1 showing this modified example. The meaning of the cross-section W-W and the main part here is the same as that in FIG. 11. The contour of the second header 12 located below (the back side of the paper surface) the cross-section W-W of the heat exchanger 1 is shown by a broken line in the figure.

[0051] The heat exchanger 1 showing this modified example includes a curved portion 16, similar to Embodiment 1. And the arrangement of the flat tubes 22 provided in the curved portion 16 is such that the distance between the opposing side surfaces of two adjacent flat tubes 22 along the curved shape of the curved portion 16 of the second header 12 is constant over the cross-sectional longitudinal direction DL. This modified example is the same as Embodiment 1 except for the arrangement of the fins 23.

[0052] The heat exchanger 1 of this modified example has the following features regarding the arrangement of the fins 23 in addition to the features regarding the arrangement of the flat tubes 22 of the curved portion 16 described above.

[0053] In this figure, the line LF connecting the outer ends of all the fins 23 provided on the flattened tube 22 of the curved section 16 is a straight line. The line LF is positioned further outward than the outer ends of all the flattened tubes 22 of the curved section 16.

[0054] In this modified example, the housing 2 housing the heat exchanger 1 has wire LF exposed to the outside of the housing 2 and is installed outdoors. Outdoors, foreign objects, such as a ball, may collide with the outer surface of the heat exchanger 1. If one fin 23 protrudes from the outer surface of the heat exchanger 1, when a foreign object collides with the protruding fin 23, only the protruding portion of the fin 23 makes contact with the foreign object. As a result, the kinetic energy of the foreign object is concentrated on the small contact area with the fin 23. The external pressure generated in this way deforms the fin 23. Once the fin 23 is deformed, air does not flow to the deformed portion of the fin 23, and the heat transfer performance of the heat exchanger 1 deteriorates.

[0055] In this modified heat exchanger 1, the outer edges of the fins 23 are aligned in a straight line, which increases the contact area when foreign objects collide with them. As a result, the kinetic energy of the foreign objects is distributed and transmitted to the larger contact area with the fins 23. In this way, external pressure is mitigated and deformation of the fins 23 is suppressed. The fins 23 in this modified example may be corrugated fins.

[0056] By configuring the heat exchanger 1 in this way, it is possible to suppress deformation of the fins 23 due to collisions with foreign objects and maintain heat transfer performance in installation environments where collisions with foreign objects are possible.

[0057] Modification 3. Figure 13 is a cross-sectional view of the main part of the flattened tube 22 of the heat exchanger 1 shown in this modification, at cross-section W-W, which is a cross-section of the central part 19. The meaning of cross-section W-W and the main part here is the same as in Figure 11. The outline of the second header 12, which is located below (towards the back of the paper) the cross-section W-W of the heat exchanger 1, is shown by a dashed line in the figure.

[0058] The heat exchanger 1 shown in this modified example includes a curved section 16, similar to the first embodiment. The arrangement of the flattened tubes 22 provided in the curved section 16 is such that the distance between the opposing sides of two adjacent flattened tubes 22 in the direction along the curved shape of the second header 12 is constant along the longitudinal direction DL of the cross-section. Except for the arrangement of the flattened tubes 22, this modified example is identical to the first embodiment and the second modified example.

[0059] In addition to the features relating to the arrangement of the flattened tubes 22 in the curved section 16 described above, the modified heat exchanger 1 has the following features relating to the arrangement of the flattened tubes 22.

[0060] In this figure, the line LT connecting the outer ends of the flattened pipe 22 of the curved section 16 is a straight line. The line LT is positioned further outward than the outer ends of all the fins 23 provided on the flattened pipe 22 of the curved section 16.

[0061] When a foreign object collides with the outer surface of the heat exchanger 1, if one flat tube protrudes, the kinetic energy of the foreign object is concentrated on the small contact area with the flat tube 22. The resulting external pressure causes the flat tube 22 to deform and its strength to decrease. If this pressure falls below the pressure resistance strength of the heat transfer medium flowing inside, the heat transfer medium leaks to the outside, and the heat exchanger 1 loses its function. In the heat exchanger 1 shown in this modified example, the outer ends of the flat tubes 22 are aligned in a straight line, making it possible to increase the number of flat tubes that come into contact when a foreign object collides with them. As a result, the kinetic energy of the foreign object is distributed and transmitted to the contact area with multiple flat tubes 22. In this way, the external pressure is mitigated and the deformation of the flat tubes 22 is suppressed. The fins 23 in this modified example may be corrugated fins.

[0062] By configuring the heat exchanger 1 in this way, deformation of the flattened pipe 22 can be suppressed and the function of the heat exchanger 1 can be maintained in installation environments where collisions with foreign objects are possible.

[0063] Modification 4. Figure 14 is a front view of the main part of the curved section 16 of the heat exchanger 1 before the bending process, which shows this modification. As described above, in this disclosure, one method for manufacturing the heat exchanger 1 having a curved section 16 is to insert and fix a flat pipe 22 into a through hole 13 of a straight header to create a flat plate-shaped assembly, and then to give the curved section 16 by a bending process. This figure is a front view of the main part of the flat plate-shaped assembly that is formed before the bending process, and the part to which the curved shape is given in the bending process is called the main part. In this modification, the main part in this figure has a twisted section 25 having a twisted shape between the part of the flat pipe 22 that is inserted into and fixed in the second header 12 and the end of the fin 23. Except for this feature, it is the same as Modification 1 of this embodiment, in which the fin 23 is a corrugated fin. The twisted section 25 is formed in a part of the flat pipe 22 that is closer to the end that is inserted into the second header 12 than to the end of the central part 19 in the extending direction DT.

[0064] Figure 15 is a top view showing a temporary assembly 30 in the manufacturing method of the heat exchanger 1, which illustrates this modified example. In the figure, the temporary assembly 30 is placed on a horizontal stage ST with its flat plate shape lying horizontally. The direction from the front to the back of the paper is vertically downward. This figure shows a top view in this orientation.

[0065] In the manufacturing method described above, the temporary assembly 30 of the heat transfer section 21, in which the flattened tube 22 is inserted and fixed into the through-hole 13 of the second header 12 before the bending process, has an arrangement in which the flattened tube 22 and fins 23 are arranged alternately. A conventional method for fixing the flattened tube 22 and the header is to braze them together using a continuous furnace. A conventional method for fixing the flattened tube 22 and the fins 23 in a heat-conductive manner is to braze them together at the same time as brazing the flattened tube 22 and the header. In this joining method, a conventional method is to use a continuous furnace that has a mechanism for introducing the assembled product into the furnace using a conveyor. In a continuous furnace, the internal atmosphere is replaced from air to nitrogen in order to prevent the formation of an oxide film on the surface of the metal material of the heat exchanger 1 components, which would hinder brazing. Therefore, reducing the amount of nitrogen required by minimizing the tunnel-shaped internal space of the continuous furnace is required in order to conserve resources in the manufacturing process. By making the temporary assembly 30 a flat plate shape, it becomes possible to reduce the height of the tunnel-shaped internal space of the continuous furnace and make the internal space smaller.

[0066] In this figure, the flat tubes 22 and fins 23 of the temporary assembly 30 are not joined before heating in the continuous furnace. By fixing the fins 23 to the flat tubes 22 of the temporary assembly 30 and simultaneously inserting all the flat tubes 22 into the through holes 13 of the header, it is possible to shorten the time required for the manufacturing process of the heat exchanger 1. To fix the flat tubes 22 and fins 23, restraining jigs 31 are placed at both ends of the flat tubes 22 of the temporary assembly 30 in a direction perpendicular to the extending direction DT of the flat tubes 22, so as to extend along the extending direction DT of the flat tubes 22. Then, two wire-shaped fixing restraining jigs 33, which extend in a direction perpendicular to the extending direction DT of the flat tubes 22, are wrapped around the entire member sandwiched between the two restraining jigs 31, and the flat tubes 22 and fins 23 are fixed together by the tension of the fixing restraining jigs 33.

[0067] In the temporary assembly 30, fins 23 are not provided between the flat tubes 22 inserted into the first straight section 14 and the second straight section 15 that are adjacent to the curved section 16, and between the flat tubes 22 inserted into the curved section 16 that are adjacent to the first straight section 14 and the second straight section 15. In these sections, a jig called a buffer section 32 is placed. The restraint jig 31, buffer section 32, and fixing restraint jig 33 are made of a material different from the heat exchanger 1, having a higher melting point than the heat exchanger 1, and are not joined to the contacting flat tubes 22 or fins 23 by heating in a continuous furnace. After heating in a continuous furnace, the restraint jig 31, buffer section 32, and fixing restraint jig 33 can be easily detached from the assembly. The curved section 16 is formed using the assembly after the restraint jig 31, buffer section 32, and fixing restraint jig 33 have been detached.

[0068] As described above, the through holes 13 in the curved section 16 of the second header 12 before the bending process are arranged such that the spacing between adjacent through holes 13 narrows from the inner circumference to the outer circumference, taking into account the change in the shape of the upper surface of the curved section 16 from a rectangle to a fan shape during the bending process. Therefore, in the temporary assembly 30, the flat pipes 22 inserted into the through holes 13 of the curved section 16 having the above-described arrangement are required to be arranged such that the spacing between adjacent outlines narrows from the inner circumference to the outer circumference. On the other hand, a corrugated fin is a thin, elongated rectangular metal plate with folds extending in a direction perpendicular to the extending direction DT of the flat pipe 22. Deformation that twists these folds is plastic deformation, so the ventilation resistance increases at the deformed location. To avoid an increase in ventilation resistance, if the fin 23 is a corrugated fin, the cross-sectional shape in the direction perpendicular to the extending direction DT of the flat pipe 22 is fixed to a rectangle. Therefore, in the temporary assembly 30, the portion where the fins 23 are provided is required to have a constant spacing between the contours of adjacent flattened pipes 22 and to be parallel.

[0069] Therefore, the flattened tube 22 inserted into and fixed in the curved portion 16 of the second header 12 is provided with a twisted portion 25 having a twisted shape between the portion inserted into the header and the end of the fin 23. In the flattened tube 22 of the curved portion 16, the distance between adjacent contours is constant in the portion of the length DT in the extending direction where the fin 23 is provided. Then, in the end portion inserted into the through hole 13 via the twisted portion 25 from the portion where the fin 23 is provided, the flattened tube 22 of the curved portion 16 is arranged such that the distance between adjacent contours narrows from the inner circumference to the outer circumference.

[0070] Furthermore, in the flat pipe 22 having the twisted portion 25, after the bending process, the spacing between the contours of adjacent portions inserted into the header becomes constant and parallel. Therefore, in the bending process, it is required to simultaneously impart the curved shape of the curved portion 16 to the header and twist the twisted portion 25 in the opposite direction to the twist to return the twisted portion 25 to a straight shape. At this time, since the twisted portion 25 has undergone plastic deformation, it will not have the same straight shape as the other flat pipes 22 that do not have the twisted portion 25 formed on them, and traces of plastic deformation remain. In this disclosure, these traces of plastic deformation are also referred to as the twisted portion 25.

[0071] In this modified example, the heat exchanger 1 may have a change before and after the bending process such that the longitudinal direction of the cross-sectional shape of the section perpendicular to the direction in which the through-holes 13 of the curved portion 16 of the second header 12 open is no longer parallel to adjacent sections. The arrangement of the through-holes 13 of the second header 12 before and after the bending process is illustrated in Figures 16 and 17, respectively. In Figure 17, the through-holes 13 of the curved portion 16 are arranged radially around the center of curvature O, with the longitudinal direction of the cross-sectional shape of the section perpendicular to the direction in which they open being parallel to adjacent sections. In this case, in the temporary assembly 30, all the flat pipes 22 do not have twisted sections 25 formed, and the longitudinal direction DL of the cross-section is parallel. Then, after the curved portion 16 is inserted into and fixed in the straight-shaped second header 12, the twisted sections 25 are formed in the flat pipes 22 provided in the curved portion 16 at the same time as the bending process that forms the curved portion 16. As a result, the portion inserted into and fixed in the second header 12 has its longitudinal cross-sectional direction DL arranged radially around the center of curvature O, and the central portion 19 on which the fins 23 are provided has adjacent fins parallel to each other in the direction along the curved shape of the curved portion 16 of the header.

[0072] By configuring the heat exchanger 1 in this way, it is possible to reduce the airflow resistance of the heat transfer section 21 provided in the curved section 16. This configuration is particularly effective in a heat exchanger 1 in which a flat pipe 22 of a flat plate-shaped heat transfer section 21 is inserted into a straight header, brazed in a continuous furnace, and then a curved shape is given to the header to form the curved section 16.

[0073] Furthermore, in addition to the features relating to the arrangement of the flattened tubes 22 in the curved section 16 and the twisting of the flattened tubes 22 in the curved section 16 described above, the modified heat exchanger 1 has the following features relating to the length of the twisted section 25.

[0074] In Figure 15, there are six flattened tubes 22 in the curved section 16. Figure 18 is a cross-sectional view of these six flattened tubes 22 at cross-section X-X, which is perpendicular to the direction of extension. Here, cross-section X-X refers to the same cross-section X-X as in Figure 15. Also, in Figure 18, the outline of the flattened tube 22 at the end inserted into the second header 12 is shown by a dashed line in a cross-section perpendicular to the direction of extension of the flattened tube 22. In the figure, the angle between the central part 19 in the extension direction DT of the flattened tube 22 and the longitudinal direction DL of the cross-section of the part joined to the header is defined as the twist angle RT. Of the six flattened tubes 22, the two central flattened tubes 22, the third and fourth from the left, have an extremely small twist angle RT between the central part 19 in the extension direction DT and their ends. Furthermore, of the six flattened tubes 22, the first and sixth flattened tubes 22 from the left have a larger torsion angle RT between the central part 19 and the end in the extending direction DT compared to the other flattened tubes 22. In addition, of the six flattened tubes 22, the second and fifth flattened tubes 22 from the left have a torsion angle RT between the central part 19 and the end in the extending direction DT that is between the central and the two flattened tubes 22 at both ends.

[0075] In Figure 14, we focus on the six flattened tubes 22 of the curved section 16. The central flattened tube 22, which has a small twist angle RT, has an extremely small distance between the end closest to the twisted portion 25 of the fin 23 and the portion joined to the second header 12. The flattened tubes 22 at both ends, which have a large twist angle RT, have a larger distance between the end closest to the twisted portion 25 of the fin 23 and the portion joined to the second header 12 than the other flattened tubes 22 in the curved section 16. The second and fifth flattened tubes 22 from the left, whose twist angles RT are between those at both ends and the central tube, have a distance between the end closest to the twisted portion 25 of the fin 23 and the portion joined to the second header 12 that is between those at both ends and the central tube.

[0076] In other words, the distance between the end of the fin 23 that is closest to the twisted portion 25 of the flat tube 22 having the twisted portion 25 and the portion that is joined to the header increases as the twist angle RT increases.

[0077] By configuring the heat exchanger 1 in this way, the deformation of the flattened tube 22 in the twisted section 25 does not interfere with the fins 23 in the curved section 16. Therefore, since the fins 23 do not deform along the longitudinal direction DL of the cross-section, it is possible to reduce the airflow resistance of the heat transfer section 21 provided in the curved section 16. This is particularly effective in a heat exchanger 1 in which a flattened tube 22 of a flat plate-shaped heat transfer section 21 is inserted into a straight header, fixed by brazing in a continuous furnace, and then a curved shape is given to the header to form the curved section 16.

[0078] Furthermore, in addition to the features relating to the arrangement of the flattened pipes 22 in the curved section 16, the twisting of the flattened pipes 22 in the curved section 16, and the length of the twisted section 25 described above, the modified heat exchanger 1 has the following features relating to the air shielding member 26 provided in the twisted section 25.

[0079] Figure 19 is a front view of the main part of the heat exchanger 1, which shows this modified example. The main part here refers to the portion of the flattened pipe 22 of the curved section 16 that is inserted into and fixed to the second header 12. In the figure, an air shielding member 26 is provided between the fins 23 provided on the flattened pipe 22 of the curved section 16 and the second header 12. The air shielding member 26 has an airflow resistance equal to or greater than that of the fins 23. If the air shielding member 26 is not provided, the portion of the curved section 16 without fins, between the end of the fins 23 in the extending direction DT closest to the second header 12 and the second header 12, has an extremely small airflow resistance compared to the central portion 19 with fins 23. Therefore, the air passing through the curved section 16 selectively concentrates and flows to the portion of the flattened pipe 22 close to the second header 12 that does not have fins 23. As a result, the airflow to the portion where heat transfer is promoted by the fins 23 is reduced, and an air velocity distribution is induced that reduces the overall heat transfer efficiency. As shown in the figure, by providing an air shielding member 26 between the second header 12 and the fin 23, it is possible to suppress the induction of the wind speed distribution described above.

[0080] When the temperature of the heat transfer medium in the heat exchanger 1 is lower than the dew point temperature of the air, condensation occurs on the surface of the heat exchanger 1. In this case, if the air shielding member 26 is provided at the bottom of the heat exchanger 1, the condensation generated on the surface of the heat exchanger 1 becomes drain water and is supplied to the air shielding member 26. If the drainage of the drain water is obstructed by the air shielding member 26, the drain water that accumulates at the top of the air shielding member 26 increases the airflow resistance in that area. Therefore, it is desirable that the air shielding member 26 has the effect of quickly draining the drain water by promoting the flow of water droplets by gravity and inducing capillary action on the water droplets. Specific examples include wire mesh, open-cell type foamed metal, and molded resin products with drain water channels inside.

[0081] By configuring the heat exchanger 1 in this way, it is possible to improve the air velocity distribution in the heat transfer section 21 provided in the curved section 16 and maintain the efficiency of heat transfer. This is particularly effective in a heat exchanger 1 in which the flat plate-shaped heat transfer section 21 members are brazed together in a continuous furnace, and then a curved shape is given to the header to form the curved section 16, and a larger gap is provided between the end of the fin 23 and the header than between the other flat tubes 22.

[0082] Modification 5. The heat exchanger 1 shown in this modification is equipped with a curved section 16, similar to the first embodiment. The arrangement of the flattened tubes 22 provided in the curved section 16 is such that the distance between the opposing sides of two adjacent flattened tubes 22 in the direction along the curved shape of the second header 12 is constant along the longitudinal direction DL of the cross-section. This modification is identical to the first embodiment, except for the features relating to the structure of the header, which will be described later. Figure 20 is a top view of the second header 12 used in the heat exchanger 1 shown in this modification.

[0083] In addition to the features relating to the arrangement of the flattened tubes 22 in the curved section 16 described above, the modified heat exchanger 1 has the following features relating to the structure of the header.

[0084] As described above, in this disclosure, one method for manufacturing a heat exchanger 1 having a curved portion 16 is to insert and fix a flattened tube 22 into a header having a curved portion 16. The heat exchanger 1 shown in this modified example is manufactured by this method. The following method is used to manufacture a header having a curved portion 16. First, a header is created that has a straight shape along the entire direction of the curved shape of the curved portion 16 and has a plurality of through holes 13 on its upper surface that are aligned along the curved shape of the curved portion 16. Then, the header is curved so that all of the plurality of through holes 13 on its upper surface open upward to form the curved portion 16.

[0085] When a straight header is curved, the length of the inner circumference of the curved portion 16 decreases in the direction along the curved shape, while the length of the outer circumference increases in the direction along the curved shape. Consequently, the shape of the upper surface of the curved portion 16 changes from a rectangle to a fan shape. Here, the shape of the through hole 13 provided on the upper surface of the curved portion 16 is a rectangle with a longer side perpendicular to the direction along the curved shape of the curved portion 16 and a shorter side in the direction along the curved shape of the curved portion 16. Therefore, before and after the formation of the curved portion 16, the shape of the through hole 13 deforms such that the length of the shorter side on the inner circumference becomes shorter and the length of the shorter side on the outer circumference becomes longer.

[0086] The heat exchanger 1 shown in this modified example has a manufacturing process in which the flattened tubes 22 of the heat transfer section 21 are inserted into the through holes 13 of a header having a curved section 16, which is manufactured as described above. When inserting the flattened tubes 22 from the direction in which the through holes 13 open, it is desirable that the shape of the through holes 13 of the header be a shape that expands the contour of the flattened tubes 22 to be inserted at equal intervals. If the distance between the contour of the flattened tubes 22 and the through holes 13 is too narrow, insertion becomes difficult, and if it is too wide, it becomes difficult to completely fill the gap between the flattened tubes 22 and the through holes 13 that is formed after insertion and to join them.

[0087] In this modified example, the flattened pipes 22 inserted into the first straight section 14 and the second straight section 15, and the flattened pipes 22 inserted into the curved section 16, have the same cross-sectional shape in the direction perpendicular to the extending direction DT. At this time, it is desirable that the shape of the through-hole 13 formed in the second header 12 is also the same. However, as described above, the through-hole 13 of the curved section 16 deforms, making it difficult to insert the flattened pipe 22 into the shorter side on the inner circumference, which deforms to become shorter in length. Therefore, in this modified example, as shown in Figure 20, the second header 12 is provided with a notch 18 on the outer circumference side of the curved section 16, which has a shape continuous with the through-hole 13 on the upper surface. The notch 18 of the second header 12 makes it possible to insert the flattened pipe 22 into the through-hole 13 of the curved section 16 from a direction perpendicular to the direction in which the through-hole 13 opens.

[0088] In the figure, the notch 18 has the same width as the through hole 13 in the direction along the curved shape of the curved portion 16, and has a shape that is continuous with the through hole 13. The short side on the outer circumference of the through hole 13 is integrated with the space of the notch 18 and disappears as an outline. In other words, the through hole 13 provided in the second header 12 has a shape that is continuous with the notch 18, which is provided on the side surface of the second header 12 located on the outer circumference in the longitudinal direction of the cross section perpendicular to the direction of opening. Note that the shape of the through hole 13 that is continuous with the notch 18 is provided in all through holes 13 in this figure, but it is sufficient if at least the through hole 13 provided in the curved portion 16 has it.

[0089] In the figure, the shorter side of the outer circumference of the through hole 13 is shown by a dashed line. The inner contour of the partition wall 17 on the outer circumference side of the second header 12 is exposed on the upper surface of the notch 18. In the figure, the inner contour of the partition wall 17 on the outer circumference side of the second header 12 is shown by a solid line.

[0090] Figure 21 is a cross-sectional view of the second header 12 used in this modified example, taken along a cross section Z-Z perpendicular to the direction along the curved shape of the curved portion 16. In this figure, the cross section Z-Z is the same as the cross section Z-Z shown in Figure 20, and is a cross section including the through hole 13. In the cross section Z-Z, the cross-sectional shape of both the outer surface and the inner surface of the second header 12 is square. Inside the inner surface, which has a square cross-sectional shape, there is a hollow space. The second header 12 has a through hole 13 on its upper surface that communicates with the hollow space. In the figure, the second header 12 has a notch 18 at the corner formed by the left side and the upper surface. The through hole 13 and the notch 18, whose contours are not actually visible, are shown by dashed lines in the figure. The lower end of the notch 18 is located below the lower end of the through hole 13. In this example, the lower end of the through-hole 13 refers to the inner surface of the partition wall 17, which forms the upper surface of the second header 12 having the through-hole 13. Note that the cross-sectional shape in the direction perpendicular to the direction in which the header extends in this modified example is not limited to a square.

[0091] Figure 22 is a cross-sectional view of the curved portion 16 of the heat exchanger 1 in this embodiment, taken along a cross section Z-Z perpendicular to the direction along the curved shape of the curved portion 16 of the second header 12. Cross section Z-Z is the same as the cross section Z-Z shown in Figure 20 and includes a through hole 13. In this figure, the flattened pipe 22 is inserted into the through hole 13. The notch 18 is into which the protrusion 27 provided on the flattened pipe 22 is inserted. The interfaces where the second header 12, the flattened pipe 22, and the protrusion 27 are in contact with each other are joined. The heat transfer medium sealed inside the second header 12 can only pass through the hole 41 of the flattened pipe 22 in cross section Z-Z.

[0092] Figure 23 is a perspective view showing a projection-forming member 28 used in this embodiment to form a protrusion 27 on a flat pipe 22. The projection-forming member 28 includes a protrusion 27 and a winding portion 29. The protrusion 27 has a shape that closes the notch 18 provided in the second header 12 when the flat pipe 22 is inserted into the through hole 13. The protrusion 27 is joined to the notch 18 when the flat pipe 22 is inserted into the through hole 13.

[0093] In the figure, the protrusion 27 has a rectangular parallelepiped shape overall. The width of the protrusion 27 in the left-right direction is slightly smaller than the width of the notch 18 in the direction along the curved shape of the curved portion 16 of the second header 12, and is a size that allows it to be fitted into the notch 18 with an appropriate spacing. The height of the protrusion 27 in the up-down direction is greater than the thickness of the upper wall of the second header 12. The width of the protrusion 27 in the depth direction, perpendicular to the left-right and up-down directions, is greater than the thickness of the partition wall 17 on the outer peripheral side of the second header 12. The winding portion 29 of the protrusion forming member 28 has a shape in which two rod-shaped portions that branch into two in the left-right direction extend longitudinally in the depth direction of the protrusion 27 on the back side of the paper in the depth direction of the protrusion 27. The length of the winding portion 29 in the longitudinal direction is slightly longer than the width DL in the longitudinal direction of the cross-section of the flat pipe 22. The width of the rod-shaped portion of the winding section 29 in the left-right direction is half the width of the protrusion 27 in the left-right direction. The height of the rod-shaped portion of the winding section 29 in the up-down direction is equal to the width of the rod-shaped portion of the winding section 29 in the left-right direction, and is smaller than the height of the protrusion 27 in the up-down direction.

[0094] Figure 24 is a perspective view of the main parts of the flattened tube 22 and the protruding part forming member 28 used in this modified example. Here, the main part refers to the end of the flattened tube 22 that is inserted into the through hole 13 of the second header 12. In the figure, the winding portion 29 of the protruding part forming member 28 has a bifurcated base where the protrusion 27 is provided, and this portion contacts one end of the flattened tube 22 in the longitudinal direction DL of the cross-section. The two opposing surfaces of the two rod-shaped portions of the winding portion 29 contact the outer shell of the flattened tube 22 and extend along the longitudinal direction DL of the cross-section. The end of the winding portion 29 in the direction of extension that does not have the protrusion 27 is bent so that the two opposing surfaces of the two rod-shaped portions become the inner circumference, so as to follow the contour of the end of the flattened tube 22 that does not contact the protrusion 27. In this way, by applying a process that causes plastic deformation to the winding portion 29, the frictional force applied to the portion in contact between the winding portion 29 and the flat pipe 22 makes it possible to fix the protruding portion forming member 28 to the flat pipe 22.

[0095] Figure 25 is a top view of the flattened tube 22 and the protruding part forming member 28 used in this modified example. In the figure, the winding portion 29 of the protruding part forming member 28 has two opposing sides of the rod-shaped portion in contact with the contour of the flattened tube 22.

[0096] Figure 26 is a perspective view of the L-shaped plate material 45 used for the protruding part forming member 28 in this modified example. The L-shaped plate material 45 is made by punching out an L-shape from a plate material with the same thickness as the width of the protruding part forming member 28 in the left-right direction, with the short side and long side joined perpendicularly at one end of each other. The L-shaped plate material 45 has a short side portion 42, a long side portion 43, and a cut portion 44. The short side portion 42 is the part that constitutes the protrusion 27 of the protruding part forming member 28. The long side portion 43 is the part that forms the wrapping portion 29 of the protruding part forming member 28 by forming a cut portion 44 in the longitudinal direction so as to halve the thickness of the plate material and tearing the long side portion 43 into two. The L-shaped plate material 45 can be manufactured in a short time using press processing.

[0097] Figure 27 is a cross-sectional view of the main part of the curved portion 16 of the second header 12 of the heat exchanger 1 in this embodiment, taken along a cross section Z-Z perpendicular to the direction of the curved shape of the curved portion 16 of the second header 12 when inserting a flat pipe 22. The main part here refers to the area around the through hole 13 of the curved portion 16 of the second header 12. In this figure, the cross section Z-Z is the same as the cross section Z-Z shown in Figure 20 and is a cross section including the through hole 13. In this figure, the insertion process of inserting the flat pipe 22 into the through hole 13 of the second header 12 is shown in the order of (a), (b), and (c) in chronological order. During the insertion process, the flat pipe 22 moves laterally from the outer circumference side (left side of the figure) to the inner circumference side (right side of the figure) of the second header 12, along the longitudinal direction of the cross-sectional shape of the through hole 13 on the upper surface of the second header 12. Subsequently, the flattened tube 22 is fixed in place, and the second header 12 is moved vertically in the vertical direction DT, which is the extension direction DT of the flattened tube 22, thereby completing the insertion process.

[0098] First, the flattened pipe 22 is positioned such that the end to be inserted into the through hole 13 is on the outer circumference side of the second header 12, above the lower end of the notch 18 and below the lower end of the through hole 13. Then, the flattened pipe 22 is positioned in a direction along the curved shape of the curved portion 16 of the second header 12, such that the shorter side of the cross-sectional shape perpendicular to the extending direction DT fits within the width of the curved shape of the curved portion 16 of the second header 12 in the direction along the curved shape of the notch 18. Then, the flattened pipe 22 is inserted by moving laterally along the notch 18 from the shorter side of the cross-sectional shape perpendicular to the extending direction DT. The positional relationship between the second header 12 and the flattened pipe 22 during this lateral movement is shown in Figure 27(a). This lateral movement continues until one end of the flattened pipe 22, on the side without the protrusion 27 in the longitudinal direction DL of its cross-section, contacts the short side on the inner circumference of the cross-sectional shape perpendicular to the opening direction of the through-hole 13 of the second header 12. The relative positions of the second header 12 and the flattened pipe 22 when the lateral movement is complete are shown in Figure 27(b). Once the lateral movement is complete, the second header 12 is moved vertically upward in the plane of the paper, which is the extending direction DT of the flattened pipe 22. This vertical movement continues until the lower surface of the protrusion 27 contacts the lower end of the notch 18. The relative positions of the second header 12 and the flattened pipe 22 when the vertical movement is complete are shown in Figure 27(c).

[0099] As described above, in a header in which a straight header is curved to form a curved portion 16, the shape of the cross section perpendicular to the opening direction of the through hole 13 is deformed. The deformation of the through hole 13 in the curved portion 16 is such that the dimension of the inner header in the direction along the curved shape of the curved portion 16 shrinks, and the dimension of the outer header in the direction along the curved shape of the curved portion 16 expands. In this modified example, the width of the curved portion 16 in the direction along the curved shape at the outer end of the through hole 13 and the outer end of the notch 18 of the curved second header 12 is wider than before the curvature, making insertion by lateral movement from the outer end to the notch 18 and through hole 13 easier. Also, during the lateral movement process, the flattened pipe 22 is guided to the end faces of the partition walls 17 that extend in the longitudinal direction of the shape of the cross section perpendicular to the opening direction on both sides in the direction along the curved shape of the notch 18 and through hole 13. Therefore, although the inner circumference end of the through hole 13 is narrower than before curving, it is possible to move laterally until contact is made with this portion. Then, during the vertical movement process, by moving along the side surface of the notch 18 and the through hole 13 until the lower surface of the protrusion 27 contacts the lower end of the notch 18, it becomes possible to bring the flattened pipe 22 and the protrusion 27 into appropriate contact with the second header 12, which facilitates joining.

[0100] By configuring the header and flattened tubes 22 of the heat exchanger 1 in this way, the flattened tubes 22 of the heat transfer section 21 are reliably inserted, making it possible to increase the yield of the heat exchanger 1 in the manufacturing process. This is particularly effective in heat exchangers 1 that have through holes 13 in the curved section 16, which are deformed when the header is curved.

[0101] The method of providing the flattened pipe 22 with a protrusion 27 that closes the notch 18 of the header is merely one example and is not limited to using a protrusion-forming member 28 equipped with a winding portion 29.

[0102] The following describes a method for manufacturing the heat exchanger 1, showing Embodiment 1 and Modifications 1 to 5 of Embodiment 1.

[0103] The manufacturing method of the heat exchanger 1, which shows Embodiment 1 and Modifications 1 to 3 of Embodiment 1, comprises: a header creation step of creating a linear header provided in a partition wall with a plurality of through holes such that the distance between adjacent holes at both ends in the longitudinal direction of the cross-sectional shape perpendicular to the direction of opening is smaller at one end than at the other; a preliminary assembly step of creating a preliminary assembly of a heat transfer section comprising a plurality of flattened tubes having a cross-sectional longitudinal direction DL which is the longitudinal direction of the contour shape of the cross-section perpendicular to the direction of extension, and a plurality of fins; an insertion step of inserting the flattened tubes of the preliminary assembly created in the preliminary assembly step into the through holes of the header; and a joining step of joining the contact portions between the through holes and the flattened tubes formed by the insertion step to create a flat plate-shaped assembly. The process includes a bending step in which a curved shape is formed on the header of the assembled product created in the joining process, such that the side with the narrower distance between adjacent through holes at both ends in the longitudinal direction of the through holes becomes the outer circumference, and adjacent flat pipes in the direction along the curved shape are formed such that the distance between their opposing sides is constant along the longitudinal direction DL of the cross-section.

[0104] Figure 28 is a flowchart showing a method for manufacturing a heat exchanger 1, illustrating Embodiment 1 and Modifications 1 to 3 of Embodiment 1. The manufacturing method here includes a header creation step S1, a preliminary assembly step S2, an insertion step S3, a joining step S4, and a bending step S5. The header creation step S1 and the preliminary assembly step S2 can be performed simultaneously and in parallel.

[0105] The header creation process S1 is a process of creating a header by forming multiple through holes 13 in a hollow rod-shaped object in the direction in which the header extends, so that a flat pipe 22 can be fixed through them to the upper surface, as shown in Figure 5. Figure 5 shows the shape of the second header 12 in the process before the bending process S5. Therefore, the curved portion 16 is not given a curved shape, but in Figure 5 and in this description it will be referred to as the curved portion 16.

[0106] In the second header 12, the multiple through holes 13 have the same shape. They are also arranged at equal intervals in the direction in which the second header 12 extends, and the longitudinal direction of the cross-section perpendicular to the direction of opening is perpendicular to the direction in which the second header 12 extends. Furthermore, one end of the longitudinal direction of the cross-section perpendicular to the direction of opening is provided to align with the direction in which the second header 12 extends. However, in the manufacturing method described here, the through holes 13 formed in the curved portion 16 have a longitudinal direction of the cross-section perpendicular to the direction of opening that is not perpendicular to the direction in which the second header 12 extends. Also, the spacing between adjacent through holes 13 formed in the curved portion 16 in the direction in which the second header 12 extends is smaller at one end (the upper end in the figure) than at the other end (the lower end in the figure) of the longitudinal direction of the cross-section perpendicular to the direction of opening. Furthermore, the spacing between adjacent through holes 13 in the direction extending of the second header 12 in the curved portion 16 is equal to the spacing between adjacent through holes 13 in portions other than the curved portion 16, at the center of the longitudinal direction of the cross section perpendicular to the opening direction.

[0107] The header creation step S1 may also be a step in which a rectangular plate-shaped member forming the upper surface has multiple through holes 13 arranged in the longitudinal direction, and a partition member is attached to the lower surface of the rectangular plate-shaped member to form a hollow space that communicates with the through holes 13.

[0108] Figure 29 shows a temporary assembly 30 in the manufacturing method of the heat exchanger 1 described herein, where Figure 29(a) is a top view and Figure 29(b) is a side view. In Figure 29(b), the holes 41 in the flattened tubes 22 are omitted from the drawing. The temporary assembly step S2 is a step in which the flattened tubes 22 and fins 23 are arranged alternately on a horizontally placed stage ST to create the temporary assembly 30, as shown in Figure 29. At this time, the longitudinal direction DL of the cross-section of the flattened tubes 22 is in the vertical direction (from the front side of the paper to the back side). In the figure, the flattened tubes 22 inserted into the through holes 13 of the curved portion 16 of the second header 12 of the temporary assembly 30 are arranged such that the distance between adjacent tubes via the fins 23 is smaller at one end than at the other end in the longitudinal direction DL of the cross-section. This arrangement is aligned with the arrangement of the through-holes 13 in the header, and the spacing at one end of the longitudinal cross-section DL (the upper end in Figure 29(b)) is smaller than the spacing at the other end (the lower end in Figure 29(b)). Therefore, in Figure 29, the flattened tubes 22 of the temporary assembly 30, sandwiched between the two buffer sections 32, have an arrangement where the longitudinal cross-section DL is not parallel. The stage ST may include either or both a structure or mechanism for fixing the flattened tubes 22 and fins 23 of the temporary assembly 30 in a desired arrangement.

[0109] The flat tube 22 and the fin 23 of the temporary assembly 30 do not need to be joined together. However, in order to prevent the flat tube 22 and the fin 23 of the temporary assembly 30 from separating during the insertion process S3, they need to be fixed together within the temporary assembly 30. The method of fixing the flat tube 22 and the fin 23 of the temporary assembly 30 is described below. First, square pipe-shaped restraint jigs 31 are placed at both ends of the flat tube 22 of the temporary assembly 30 in a direction perpendicular to the extending direction DT (left and right direction in the figure), so as to extend along the extending direction DT of the flat tube 22. Then, two wire-shaped fixing restraint jigs 33 are wrapped around the entire member sandwiched between the two restraint jigs 31, extending in a direction perpendicular to the extending direction DT of the flat tube 22. In this way, the flat tube 22 and the fin 23 are fixed together by the tension of the fixing restraint jigs 33. The method for fixing the gap between the flattened tube 22 and the fin 23 of the temporary assembly 30 in the temporary assembly process S2 is not limited to the method described above. For example, the gap between the flattened tube 22 and the fin 23 may be partially bonded with adhesive.

[0110] Insertion step S3 involves inserting the flat tubes 22 of the heat transfer section 21, created in the temporary assembly step S2, into the header created in the header creation step S1. In this example, insertion step S3 has the following procedure. First, the shape of the cross-section of the upper surface of the multiple through holes 13 of the header is matched to the shape of the cross-section perpendicular to the extending direction DT of the multiple flat tubes 22 of the temporary assembly 30 fixed on the stage ST. Then, the direction in which the through holes 13 of the header open is matched to the extending direction DT of the flat tubes 22 of the temporary assembly 30. Next, the header is moved from one end of the flat tube 22 towards the center 19 in the direction in which the through holes 13 of the header open. Through the above procedure, insertion step S3 ensures that all the flat tubes 22 of the temporary assembly 30 are simultaneously inserted into the through holes 13 of the header. The stage ST may have a structure and / or mechanism that allows the flat tubes 22 to be smoothly inserted into the through holes 13 of the header.

[0111] The joining process S4 involves joining the flat tube 22, which was inserted into the header of the temporary assembly 30 in the insertion process S3, to the header. In this example, the joining between the header and the flat tube 22, and between the flat tube 22 and the fin 23 in joining process S4, is shown as a brazing method using a continuous furnace. Clad material, which is a material with brazing material laminated to its surface, is suitable as the material for the header and the flat tube 22 or fin 23. When the brazing material on the surface of the clad material is heated to a temperature higher than its melting point in the continuous furnace, it melts and becomes liquid. The liquid brazing material flows into the gaps between the through-hole 13 of the header and the flat tube 22, and between the flat tube 22 and the fin 23, due to capillary forces acting on these gaps. Subsequently, when the temperature of the brazing material cools to a temperature lower than its melting point, the brazing material solidifies while forming an alloy with the surrounding material, joining the header and the flat tube 22, and the flat tube 22 and the fin 23. After the connection between the header and the flattened tube 22, and between the flattened tube 22 and the fin 23, the restraining jig 31, the buffer section 32, and the fixing restraining jig 33 are removed from the heat transfer section 21. Note that the joining process S4 is not limited to the method using the continuous furnace described above. For example, in the joining process S4, the connection between the flattened tube 22 and the fin 23 may be made using an adhesive with high thermal conductivity, and the connection between the through-hole 13 of the header and the flattened tube 22 may be made using a method that does not use a continuous furnace, such as high-frequency brazing or torch brazing.

[0112] The bending process S5 imparts a curved shape to the header of the flat assembly created in the joining process S4. In this example, the bending process S5 has the following procedure. First, the flat assembly, with the flattened tube 22 of the heat transfer section 21 joined to the header, is placed on the stage ST in a lying position. Next, a bending die, which has the curved shape of the inner circumference of the curved section 16 on its outer surface, is fixed in a predetermined position on the assembly, and a force is applied to move the header so that one end in the longitudinal direction is raised upward while pressing it against the bending die. In this way, the part of the header and the heat transfer section 21 that comes into contact with the bending die is formed into the curved shape of the inner circumference of the curved section 16. Note that the bending process S5 is not limited to the method using the bending die described above.

[0113] In the heat transfer section 21 after the bending process S5, the adjacent flat pipes 22 in the direction along the curved shape of the curved section 16 have a constant distance between their opposing side surfaces along the longitudinal direction DL of the cross-section. Before and after the bending process S5, the distance between the opposing side surfaces of two adjacent flat pipes 22 in the direction along the curved shape of the curved section 16 changes from being inconsistent, as shown in the temporary assembly 30 in Figure 29, to being constant, as described above. The fins 23 have a flexible structure like a wire mesh and deform flexibly in accordance with the change in the distance between the flat pipes 22 in the longitudinal direction DL of the cross-section provided at both ends in the direction along the curved shape of the curved section 16.

[0114] By configuring the manufacturing method of the heat exchanger 1 in this way, the assembled product fed into the continuous furnace is flat, thus reducing the tunnel-shaped internal space of the continuous furnace and enabling resource-saving brazing. Furthermore, by devising the arrangement of the through holes 13 in the header creation process S1, after the bending process S5, the spacing between adjacent flat pipes 22 in the curved section 16 naturally becomes constant along the longitudinal direction DL of the cross-section. In this way, it becomes possible to manufacture a heat exchanger 1 that reduces the airflow resistance of the curved section 16.

[0115] The manufacturing method for the heat exchanger 1 shown in Modification 4 of Embodiment 1 is a modification of the above-described manufacturing method and includes a step of giving a twisted portion 25 to the flattened tube 22 of the heat transfer section 21. The manufacturing method for the heat exchanger 1 shown in Modification 4 of Embodiment 1 has a first twisting step before the temporary assembly step and a second twisting step simultaneously with the bending step. The first twisting step is to form a twisted portion 25 in the flattened tube 22 used for the curved section 16. The second twisting step is to twist the twisted portion 25 of the curved section 16 in a direction that reduces the twist angle RT.

[0116] Figure 30 is a flowchart showing a modification 4 of Embodiment 1 for manufacturing a heat exchanger 1. The manufacturing method here includes a header creation step S21, a first twisting step S22, a temporary assembly step S23, an insertion step S24, a joining step S25, a bending step S26, and a second twisting step S27. The header creation step S21, the first twisting step S22, and the temporary assembly step S23 can be performed simultaneously and in parallel. The bending step S26 and the second twisting step S27 are performed simultaneously.

[0117] The header creation step S21 is the same as the header creation step S1 of the manufacturing method described above. The header creation step S21 is the step of creating a header that has a linear shape as shown in Figure 5, and in which the longitudinal directions of the shapes of the upper surfaces of the multiple through holes 13 of the curved portion 16 are not parallel.

[0118] The first twisting step S22 is a step in which a twisted portion 25 is added to the flattened pipe 22 of the curved portion 16 of the temporary assembly 30. At this time, the flattened pipe 22 to which the twisted portion 25 has been added has a cross-sectional longitudinal direction DL that is parallel to the adjacent pipe in the central portion 19, but not parallel to the adjacent pipe in the portion that is inserted into the through hole 13 of the header.

[0119] Figure 15 shows a temporary assembly 30 in the manufacturing method of the heat exchanger 1 described herein. Figure 15(a) is a top view, and Figure 15(b) is a side view. In Figure 15(b), the holes 41 of the flattened tube 22 and the fin pattern 40 of the fin 23 are omitted and not shown. The temporary assembly step S2 is a step in which the flattened tube 22 and the fin 23 are arranged alternately on a horizontally placed stage ST, as shown in Figure 15, so that the longitudinal direction DL of the cross-section of the central part 19 of the flattened tube 22 is in the vertical direction, thereby creating a temporary assembly 30. The part of the temporary assembly 30 sandwiched between the two buffer parts 32 is the part that will be inserted into the curved part 16 of the header, and the flattened tube 22 in this part has a twisted part 25 formed in the first twisting step S22. The stage ST may have either or both a structure or mechanism for fixing the flattened tube 22 and the fin 23 of the temporary assembly 30 in the desired arrangement.

[0120] Insertion step S24 involves inserting the flattened tube 22 of the heat transfer section 21, which was created in the temporary assembly step S23, into the header created in the header creation step S21. Insertion step S24 here is the same as insertion step S3 in the manufacturing method described above.

[0121] The joining process S25 involves joining the flattened pipe 22, which was inserted into the header of the temporary assembly 30 in the insertion process S24, to the header. The joining process S25 here is the same as the joining process S4 of the manufacturing method described above.

[0122] The bending process S26 imparts a curved shape to the flat plate-shaped header of the assembly created in the joining process S25. In the bending process S26, the method for curving the header, which has a straight shape, is the same as in the bending process S5 of the manufacturing method described above. The manufacturing method of the heat exchanger 1 here includes a second twisting process S27 in which, simultaneously with the bending process S26 for curving the header, the flat tube 22, which has a twisted portion 25 provided in the curved portion 16, is twisted in a direction that reduces the twist angle RT.

[0123] In the second header 12, before and after the bending process S26, the shape of the upper surface of the curved portion 16 changes from a rectangle shown in Figure 5 to a fan shape shown in Figure 3. Accordingly, the arrangement of the cross-sectional longitudinal direction DL in the shape of the upper surface of the through hole 13 of the curved portion 16 changes from non-parallel as shown in Figure 5 to parallel as shown in Figure 3. At this time, if the flattened pipe 22 of the curved portion 16 retains the twisted portion 25, adjacent pipes will be parallel in the portion fixed to the through hole 13, but will not be parallel in the central portion 19. As a result, after the bending process S26, the opposing sides of adjacent flattened pipes 22 in the central portion 19 along the curved shape of the curved portion 16 will not be constant along the cross-sectional longitudinal direction DL, leading to an increase in the airflow resistance of the air passing through this portion. Therefore, the manufacturing method of the heat exchanger 1 here includes a second twisting process S27 in which the twisted portion 25 is twisted so that the twist angle RT becomes 0°, simultaneously with the bending process S26. In the second twisting process S27, the distance between the opposing sides of the flat pipes 22 adjacent to each other in the direction along the curved shape of the curved section 16 becomes constant along the longitudinal direction DL of the cross-section at the central section 19.

[0124] By configuring the manufacturing method of the heat exchanger 1 in this way, the fins 23 provided on the flattened tube 22 of the curved section 16 do not deform, making it possible to manufacture a heat exchanger 1 that reduces the airflow resistance of the curved section 16.

[0125] Furthermore, as a modified example of the manufacturing method of the heat exchanger 1 shown in Modification 4 of Embodiment 1, the manufacturing method shown in the flowchart in Figure 31 is also mentioned.

[0126] The header creation step S31 is the same as the header creation step S1 described above. The header creation step S31 is the step of creating a header that has a linear shape as shown in Figure 16, and in which the longitudinal directions of the shapes of the upper surfaces of the multiple through holes 13 of the curved portion 16 are parallel. Figure 16 shows the shape of the second header 12 in the step before the curving step S26. Therefore, the curved portion 16 is not given a curved shape, but in Figure 16 and in this description it is referred to as the curved portion 16.

[0127] Figure 32 shows a preliminary assembly 30 in the manufacturing method of the heat exchanger 1 described herein. Figure 32(a) is a top view, and Figure 32(b) is a side view. In Figure 32(b), the holes 41 in the flattened tubes 22 are omitted from the diagram. The preliminary assembly step S2 is a step in which the flattened tubes 22 and fins 23 are arranged alternately on a horizontally placed stage ST, as shown in Figure 32, so that the longitudinal direction DL of the cross-section of the central part 19 of the flattened tubes 22 is in the vertical direction, thereby creating a preliminary assembly 30. All of the flattened tubes 22 in the preliminary assembly 30 are not twisted or bent. Note that the fins 23 in the preliminary assembly 30 in the manufacturing method of the heat exchanger 1 described herein may be corrugated fins.

[0128] The insertion step S33 involves inserting the flattened tube 22 of the heat transfer section 21, which was created in the temporary assembly step S32, into the header created in the header creation step S31. The insertion step S33 here is the same as the insertion step S3 of the manufacturing method described above.

[0129] The joining process S34 involves joining the flattened pipe 22, which was inserted into the header of the temporary assembly 30 in the insertion process S33, to the header. The joining process S34 here is the same as the joining process S4 of the manufacturing method described above.

[0130] The bending process S35 imparts a curved shape to the flat assembled header created in the joining process S34. In the bending process S35, the method for curving the header, which has a straight shape, is the same as in the bending process S5 described above. The manufacturing method of the heat exchanger 1 here includes a bending process S35 for curving the header and a twisting process S36 for twisting the flat tube 22, which has a twisted portion 25 provided in the curved portion 16, in a direction that increases the twist angle RT.

[0131] Before and after the bending process S26, the shape of the upper surface of the curved section 16 of the second header 12 changes from a rectangle shown in Figure 16 to a fan shape shown in Figure 17. Consequently, the arrangement of the longitudinal cross-sectional directions DL in the shape of the upper surface of the through hole 13 of the curved section 16 changes from parallel as shown in Figure 16 to non-parallel as shown in Figure 17. At this time, if the flattened pipes 22 provided in the curved section 16 remain straight pipes without twisting, the longitudinal cross-sectional directions DL of adjacent pipes will no longer be parallel in both the portion fixed to the through hole 13 and the central portion 19. As a result, after the bending process S26, the opposing sides of adjacent flattened pipes 22 in the central portion 19 along the curved shape of the curved section 16 will not be constant along the longitudinal cross-sectional direction DL, leading to an increase in the airflow resistance of the air passing through this portion. Therefore, the manufacturing method of the heat exchanger 1 described here includes a twisting step S27 in which a twisted portion 25 is formed in the flattened pipe 22 of the curved section 16 at the same time as the bending step S26. In the flattened pipe 22 of the curved section 16, the location where the twisted portion 25 is formed is the portion of the flattened pipe 22 in the extending direction between the portion that is fixed through to the second header 12 and the portion where the fins 23 are provided, in which the fins 23 are not provided. Due to the twisting step S27, the opposing sides of adjacent flattened pipes 22 in the direction along the curved shape of the curved section 16 are constant along the longitudinal direction DL of the cross-section at the central portion 19.

[0132] By configuring the manufacturing method of the heat exchanger 1 in this way, the fins 23 provided on the flattened tube 22 of the curved section 16 are not deformed during manufacturing, making it possible to manufacture a heat exchanger 1 that reduces the airflow resistance of the curved section 16.

[0133] The manufacturing method for the heat exchanger 1, which shows a modified example 5 of Embodiment 1, comprises a curved header creation step, a temporary assembly step, an insertion step, and a joining step. The curved header creation step is the step of creating a header having a curved section 16 having a curved shape and a partition wall 17 through which a plurality of flat tubes 22 can be passed and fixed. The temporary assembly step is the step of temporarily assembling a heat transfer section having a plurality of flat tubes 22 and a plurality of fins 23, which have a cross-sectional longitudinal direction DL that is the longitudinal direction of the cross-sectional contour shape perpendicular to the extending direction DT. The insertion step is the step of inserting the plurality of flat tubes 22 of the heat transfer section through the partition wall 17 of the header. The joining step is the step of joining the contact points between the through-holes 13 formed by the insertion step and the flat tubes 22 to create a flat plate-shaped assembly.

[0134] Figure 33 is a flowchart showing a method for manufacturing a heat exchanger 1, which is a modified example 5 of Embodiment 1. The manufacturing method here includes a curved header creation step S11, a temporary assembly step S12, an insertion step S13, and a joining step S14. The curved header creation step S11 and the temporary assembly step S12 can be performed simultaneously and in parallel.

[0135] The curved header creation step S11 is a step in which a curved header, such as the second header 12 shown in Figure 20, is created by forming multiple through holes 13 in a row along the longitudinal direction on the upper surface of a hollow rod-shaped object having a curved portion 16 having a curved shape, through which a flat pipe 22 can be passed and fixed. Alternatively, the curved header creation step S11 may be a step in which a curved header is created by first providing multiple through holes 13 on a hollow rod-shaped object and then forming the curved portion 16. Or, the curved header creation step S11 may be a step in which multiple through holes 13 are formed in a row on a plate-shaped member having a curved shape that forms the upper surface, and a member that serves as a partition wall 17 forming a hollow space communicating with the through holes 13 is attached to the lower surface of this plate-shaped member.

[0136] The preliminary assembly process S12 is a process in which fins 23 are placed between flattened tubes 22 that are lined up with their longitudinal cross-sections DL aligned, and the contact points between the flattened tubes 22 and the fins 23 are joined to create a preliminary assembly 30. In the preliminary assembly 30, the flattened tubes 22 and the fins 23 are joined, for example, by brazing using a continuous furnace or by adhesive bonding using an adhesive with high thermal conductivity. The preliminary assembly 30 consists of a first preliminary assembly 30a, a flat plate into which the flattened tubes 22 are inserted in the first straight section 14; a second preliminary assembly 30b, a flat plate into which the flattened tubes 22 are inserted in the second straight section 15; and a third preliminary assembly 30c, a flat plate into which the flattened tubes 22 are inserted in the curved section 16.

[0137] Insertion step S13 involves inserting the flattened pipe 22 of the temporary assembly 30, created in temporary assembly step S12, into the header created in curved header creation step S11. In this example, insertion step S3 involves placing the second header 12 on a horizontal stage ST with the side having the through-hole 13 facing upwards, and inserting the flattened pipe 22 of the temporary assembly 30 into the through-hole 13. Here, the flattened pipe 22 of the first temporary assembly 30a is inserted into the through-hole 13 of the first straight section 14, the flattened pipe 22 of the second temporary assembly 30b is inserted into the through-hole 13 of the second straight section 15, and the flattened pipe 22 of the third temporary assembly 30c is inserted into the through-hole 13 of the curved section 16.

[0138] Figure 27 shows the insertion process S13 in the order of (a), (b), and (c) in chronological order. In the insertion process S13, first, the flattened pipe 22 moves laterally from the outer circumference side (left side of the figure) to the inner circumference side (right side of the figure) of the second header 12, along the longitudinal direction of the cross-sectional shape of the through hole 13 on the upper surface of the second header 12. Then, the flattened pipe 22 is fixed, and the second header 12 moves vertically in the vertical direction DT, which is the extension direction of the flattened pipe 22. In this lateral movement, the flattened pipe 22 is inserted into the notch 18 from one end (right side of the figure) in the longitudinal direction DL of the cross-section, and then moves through the through hole 13 in the direction of the longitudinal direction DL of the cross-section.

[0139] In addition, the insertion step S13 in the manufacturing method of the heat exchanger 1 described here may involve inserting the flattened pipe 22 of the temporary assembly 30 from the direction in which the through hole 13 opens. In this case, it is preferable that the header does not have a notch 18 that has a shape continuous with the through hole 13.

[0140] The joining process S14 involves joining the flattened tube 22, which was inserted into the header of the temporary assembly 30 in the insertion process S13, to the header. In this example, the joining method between the header and the flattened tube 22, and between the flattened tube 22 and the fin 23 in the joining process S14, is preferably a method that does not use a continuous furnace, such as high-frequency brazing or torch brazing.

[0141] By configuring the manufacturing method of the heat exchanger 1 in this way, the fins 23 provided on the flattened tube 22 of the curved section 16 do not deform, making it possible to manufacture a heat exchanger 1 that reduces the airflow resistance of the curved section 16. Furthermore, if the insertion step S13 is a step in which the flattened tube 22 is inserted by moving it laterally from the notch 18 to the through hole 13, the flattened tube 22 of the heat transfer section 21 is reliably inserted, making it possible to increase the yield of the heat exchanger 1 in the manufacturing process. This is particularly effective in a heat exchanger 1 having a through hole 13 in the curved section 16 that has been deformed when the header is curved.

[0142] Embodiment 2. The heat exchanger 1 of Embodiment 2 will be described with reference to Figure 34. The heat exchanger 1 of Embodiment 1 had a partition wall 17 whose cross-sectional shape perpendicular to the direction along the curved shape of the curved portion 16 of the second header 12 did not have a distribution of wall thickness. The heat exchanger 1 of this embodiment has a distribution of wall thickness on either the inner circumference side, the outer circumference side, or both sides of the partition wall 17, with a thick portion and a thin portion.

[0143] The heat exchanger 1 of this embodiment has the same overall shape as the heat exchanger 1 of Embodiment 1 shown in Figure 2, is housed in a housing 2 as shown in Figure 1, and includes a second header 12 having a curved portion 16 with the curved shape shown in Figure 3. In Figure 3, the second header 12 has parallel longitudinal directions in the cross-sectional shape of the upper surface of the through hole 13 of the curved portion 16, but in the header used in this embodiment, this part does not have to be parallel. Also, in the header used in this embodiment, the distance between the sides of at least two adjacent flat pipes 22 facing each other in the direction along the curved shape of the curved portion 16 does not have to be constant along the longitudinal direction DL of the cross-section.

[0144] Figure 34 is a cross-sectional view of the second header 12 of the heat exchanger 1 shown in this embodiment, taken along cross-section V-V. Here, cross-section V-V is in the same position as cross-section V-V shown in Figure 3. In this embodiment, the same reference numerals used in Embodiment 1 indicate the same or corresponding parts. In this figure, the cross-sectional shape perpendicular to the direction along the curved shape of the curved portion 16 of the second header 12 used in this embodiment has a distribution of wall thickness of the partition wall 17. This distribution of wall thickness of the partition wall 17 alternates between portions with a minimum wall thickness TS and portions with a maximum wall thickness TL on the inner circumference side (right side in the figure) and outer circumference side (left side in the figure) of the curved portion 16.

[0145] Furthermore, the thickness distribution of the partition wall 17 on the side of the header used in this embodiment may be on either the inner or outer circumference side. Also, the cross-sectional shape of the header used in this embodiment at cross-section V-V may be triangular as shown in Figure 35, pentagonal as shown in Figure 36, or any other shape.

[0146] By providing a thickness distribution in the partition wall 17 on the side of the curved portion 16, the portion with the minimum thickness TS becomes less rigid than the portion with the maximum thickness TL. In this way, during the manufacturing process of the header, when the curved portion 16 deforms from a straight shape to a curved shape, a portion with low rigidity can be intentionally provided, making it possible to mitigate the deformation of the through hole 13 in the curved portion 16.

[0147] In this way, by providing a distribution in the thickness of the partition wall 17 on the side of the curved portion 16, deformation of the through hole 13 during molding of the curved portion 16 is suppressed, and the insertion of the flattened pipe 22 into the through hole 13 and the joining between the through hole 13 and the flattened pipe 22 become more reliable. This also makes it possible to improve the yield of the header material.

[0148] Modification 6. Figure 37 is a top view of the second header 12 of the heat exchanger 1 showing a modification of this embodiment. Figure 38 is a cross-sectional view of the second header 12 of the heat exchanger 1 showing a modification of this embodiment, at cross-section Y-Y, which is a cross section perpendicular to the direction along the curved shape, including the through hole 13 of the curved portion 16. Here, cross-section Y-Y is at the same position as cross-section Y-Y shown in Figure 37.

[0149] The second header 12 used in this modified example has a cross-sectional shape perpendicular to the direction of the curved shape, including the through-holes 13 of the curved portion 16, such that the thickness of the partition wall 17 on the outer peripheral side is greatest at the end on the side with the through-holes 13 in the direction in which the through-holes 13 open. In Figure 37, of the six through-holes 13 provided in the curved portion 16, the outer peripheral contour of the shape of the upper surface of four of the through-holes 13, excluding the two at both ends in the direction of the curved shape, protrudes. In Figure 38, the through-holes 13 are provided on the upper surface of the partition wall 17 of the second header 12. The outer peripheral side (left side in the figure) of the partition wall 17 has a minimum thickness TS and a maximum thickness TL at the upper end. This portion with the maximum thickness TL is the second portion from the right in Figure 37, which is the protruding part of the outer peripheral contour. Furthermore, the cross-section Y-Y of the second header 12 has a thickness distribution in which the partition walls 17 on the outer and inner sides alternate between the minimum thickness TS and the maximum thickness TL, with portions having a thickness greater than the minimum thickness TS and smaller than the maximum thickness TL.

[0150] The number of through holes 13 in the curved portion 16 is not limited to six. Also, the number of protruding parts on the outer circumference of the curved portion 16 only needs to be at least one.

[0151] By increasing the thickness of the portion of the curved section 16 that forms the outer contour of the through hole 13 compared to other parts, the rigidity of this portion is increased. In this way, during the manufacturing process of the header, when the curved section 16 deforms from a straight shape to a curved shape, the elongation of the outer circumference of the through hole 13 is reduced, and the deformation of the through hole 13 from a rectangle to a fan shape is suppressed.

[0152] In Figure 38, the cross-section Y-Y of the second header 12 has a thickness distribution in which the partition walls 17 on the outer and inner sides alternate between portions with a thickness greater than the minimum thickness TS and portions with a thickness less than the maximum thickness TL. In this modified example, the partition walls 17 on the sides do not necessarily have to have such a thickness distribution.

[0153] In this way, by providing a distribution in the thickness of the partition wall 17 on the side of the curved portion 16, deformation of the through hole 13 during molding of the curved portion 16 is suppressed, and the insertion of the flattened pipe 22 into the through hole 13 and the joining between the through hole 13 and the flattened pipe 22 become more reliable. This also makes it possible to improve the yield of the header material.

[0154] Modification 7. Figure 39 is a cross-sectional view of the second header 12 used in this modification at cross-section V-V, which is a cross-section perpendicular to the longitudinal direction of the second straight section 15. Cross-section V-V here is in the same position as cross-section V-V shown in Figure 3. In this modification, the heat exchanger 1 has a distribution in which the thickness of the partition walls 17 on the inner and outer sides of the curved section 16 of the header, in a cross-section perpendicular to the direction along the curved shape, is such that the thickest part is closer to the side with the through hole 13 than the thinnest part.

[0155] In the figure, the inner circumference (right side of the paper) and outer circumference (left side of the paper) sides of the partition wall 17 of the second header 12 have a minimum thickness TS at the lower end and a maximum thickness TL at the upper end. The second header 12 has a through hole 13 on its upper surface. Therefore, in this figure, the partition wall 17 on the inner circumference and outer circumference sides of the second header 12 has a thickness distribution in which the thickest part is closer to the side with the through hole 13 (the upper surface in this figure) than the thinnest part.

[0156] By increasing the thickness of the side surface (top surface in this figure) of the curved portion 16 that has the through hole 13 compared to other parts, the rigidity of this part is increased. In this way, when the curved portion 16 deforms from a straight shape to a curved shape during the header manufacturing process, the elongation on the outer circumference of the through hole 13 is reduced, and the deformation of the through hole 13 from a rectangle to a fan shape is suppressed.

[0157] In this way, by providing a distribution in the thickness of the partition wall 17 on the side of the curved portion 16, deformation of the through hole 13 when forming the curved portion 16 is suppressed, and the insertion of the flattened pipe 22 into the through hole 13 and the joining between the through hole 13 and the flattened pipe 22 become more reliable. This makes it possible to improve the yield of the header material.

[0158] Although the heat exchanger 1 in this disclosure is exemplified as having an L-shaped cross-section comprising a first straight section 14, a second straight section 15, and a curved section 16, it is sufficient to have a curved section 16 with a curved shape. For example, it may have a U-shaped cross-section comprising two curved sections 16 between three straight sections, an O-shaped cross-section comprising three curved sections 16 between four straight sections, or a C-shaped cross-section without any straight sections.

[0159] 1 Heat exchanger, 11 First header, 12 Second header, 13 Through hole, 16 Curved section, 17 Partition wall, 18 Notched section, 19 Central section, 22 Flattened tube, 23 Fin, 25 Twisted section, 26 Air shielding member, 27 Protrusion, 42 Fin pattern, DL Longitudinal direction of cross-section, DT Direction of extension of flattened tube, HF Fin height, O Center of curvature, S1 Header creation process, S2 Temporary assembly process, S3 Insertion process, S4 Joining process, S5 Curving process, S11 Curved header creation process, S12 Temporary assembly process, S13 Insertion process, S14 Joining process, S21 Header creation process, S22 First twisting process, S23 Temporary assembly process, S24 Insertion process, S25 Joining process, S26 Curving process, S27 Second twisting process, S31 Header creation process, S32 Temporary assembly process, S33 Insertion process, S34 Joining process, S35 Bending process, S36 Twisting process, WF Fin width

Claims

1. A heat exchanger comprising a header having a curved section having a curved shape, a plurality of flattened tubes penetrating and fixed to the partition wall of the header, and fins provided on the outer surface of the flattened tubes, wherein, if the longitudinal direction of the shape of the cross-sectional contour perpendicular to the extending direction of the flattened tubes is defined as the longitudinal direction of the cross-section, at least two of the flattened tubes provided in the curved section that are adjacent in the direction along the curved shape have a constant distance between their opposing side surfaces along the longitudinal direction of the cross-section.

2. The heat exchanger according to claim 1, wherein the width of the flattened tube provided in the curved portion is smaller than the width of the fin in the longitudinal direction of its cross-section.

3. The heat exchanger according to claim 1 or 2, wherein all of the fins are corrugated fins, have the same fin width, the same fin height, and the same fin pattern.

4. The heat exchanger according to claim 1, wherein all of the fins provided in the curved portion have a straight line connecting the ends on the outer circumference side that is farther from the center of curvature of the curved shape.

5. The heat exchanger according to claim 1, wherein all of the flattened tubes provided in the curved section have a straight line connecting the ends on the outer circumference side that is farther from the center of curvature of the curved shape.

6. The heat exchanger according to claim 1, wherein the flattened tube provided in the curved portion has a twist between the central portion in the extending direction and the portion joined to the header.

7. The heat exchanger according to claim 6, wherein the portion of the flattened tube provided with the twist is defined as a twisted portion, and the angle between the longitudinal direction of the cross-section at one end of the twisted portion in the extending direction and the longitudinal direction of the cross-section at the other end is defined as the twist angle, and the plurality of flattened tubes having the twisted portion provided in the curved portion have a distance between the end of the fin closest to the twisted portion and the portion joined to the header, with the distance increasing in descending order of the twist angle.

8. The heat exchanger according to claim 7, further comprising an air shielding member having greater airflow resistance than the fins between the header and the fins.

9. The heat exchanger according to claim 1, wherein the through-hole provided in the partition wall of the curved portion into which the flattened pipe is inserted and fixed has a shape that is continuous with a notch provided on the side surface of the header located on the outer circumference side of the curved shape in the longitudinal direction in a cross-sectional shape perpendicular to the direction of opening.

10. The heat exchanger according to claim 9, wherein the flattened tube has a protrusion that closes the notch when inserted into the through hole.

11. A heat exchanger comprising a header having a curved portion having a curved shape, a plurality of flattened tubes penetrating and fixed to the partition wall of the header, and fins provided on the outer surface of the flattened tubes, wherein the side closer to the center of curvature of the curved shape is the inner circumference side and the side farther away is the outer circumference side, and at least one side of the curved shape on the innermost and outermost sides in a cross section perpendicular to the extending direction of the header of the curved portion has a thickness distribution consisting of alternating thick and thin portions.

12. A heat exchanger comprising a header having a curved section having a curved shape, a plurality of flattened tubes penetrating and fixed through a partition wall of the header, and fins provided on the outer surface of the flattened tubes, wherein the side furthest from the center of curvature of the curved shape is considered the outer circumference, and the cross-sectional shape of the section perpendicular to the direction along the curved shape of the header, including through holes through which the flattened tubes provided in the curved section penetrate, is such that the wall thickness of the partition wall on the outer circumference side is maximum at the end on the side with the through holes in the direction in which the through holes open.

13. A heat exchanger comprising a header having a curved portion having a curved shape, a plurality of flattened tubes penetrating and fixed through a partition wall of the header, and fins provided on the outer surface of the flattened tubes, wherein the side closer to the center of curvature of the curved shape is defined as the inner circumference side and the side farther from the center of curvature as the outer circumference side, and the partition wall on at least one side of the inner circumference and outer circumference side of the curved shape in a cross section perpendicular to the direction along the curved shape of the curved portion has a wall thickness distribution in which the thickest part is closer to the partition wall through which the flattened tubes penetrate and are fixed than the thinnest part.

14. A method for manufacturing a heat exchanger, comprising: a header creation step of creating a linear header provided in a partition wall with a plurality of through holes such that the distance between adjacent through holes at both ends in the longitudinal direction of the cross-sectional shape in a cross section perpendicular to the direction of opening is smaller at one end than at the other; a preliminary assembly step of creating a preliminary assembly of a heat transfer section comprising a plurality of flat tubes and a plurality of fins having a longitudinal direction of the cross section which is the longitudinal direction of the contour shape of the cross section perpendicular to the direction of extension; an insertion step of inserting the flat tubes of the preliminary assembly created in the preliminary assembly step into the through holes of the header; a joining step of joining the contact portions between the through holes and the flat tubes formed by the insertion step to create a flat plate-shaped assembly; and a curving step of giving the header of the assembly created in the joining step a curved shape such that the side with the narrower distance between the ends in the longitudinal direction of the cross-sectional shape of adjacent through holes is the outer circumference, and shaping the curved portion of the adjacent flat tubes in the direction along the curved shape such that the distance between the opposing sides is constant along the longitudinal direction of the cross section.

15. A method for manufacturing a heat exchanger according to claim 14, comprising a twisting step during the period from the start to the completion of the bending step, wherein a twisted portion is provided at the end of the flattened pipe in the extending direction of the curved portion.

16. A method for manufacturing a heat exchanger, comprising: a curved header manufacturing step of creating a curved header having a curved section having a curved shape, wherein the partition wall of the curved section has through holes where the spacing between adjacent holes at both ends of the cross-sectional shape perpendicular to the direction of opening is constant along the longitudinal direction; a preliminary assembly step of creating a preliminary assembly of a heat transfer section having a plurality of flattened tubes and a plurality of fins, wherein the longitudinal direction of the cross-section is such that the shape of the contour of the cross-section perpendicular to the direction of extension is in the longitudinal direction; an insertion step of inserting the flattened tubes of the preliminary assembly created in the preliminary assembly step into the through holes of the curved header created in the curved header manufacturing step; and a joining step of joining the contact portion between the through holes formed by the insertion step and the flattened tubes.

17. The method for manufacturing a heat exchanger according to claim 16, wherein the curved header creation step includes providing a notch in the partition wall of the curved portion, which is located on the outer circumference of the curved shape in the longitudinal direction of the cross-sectional shape perpendicular to the direction in which the through hole of the curved portion opens and has a shape continuous with the through hole, and the insertion step includes inserting the flattened pipe into the notch from one end in the longitudinal direction of the cross-section and then moving it through the through hole in the longitudinal direction of the cross-section to insert it.

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