Pipe structure of heat exchanger and manufacturing method of the same

Abstract

To provide a pipe structure of a heat exchanger which can reduce complexity of a manufacturing process and inhibit heat degradation of a member in the manufacturing process, and to provide a manufacturing method of the pipe structure.SOLUTION: Spaces between each manifold 4A, 4B into which an inner pipe 2 is inserted and an outer pipe 3 are sealed by annular seal materials S1, and spaces between each manifold 4A, 4B and the inner pipe 2 are sealed by annular seal materials S2. Longitudinal ends of the outer pipe 3 are sealed by the respective manifolds 4A, 4B. Bead parts 2a, 2b protruding from two positions, which are spaced apart from each other in a longitudinal direction of the inner pipe 2, on an outer peripheral surface to the outer periphery side are formed. The manifold 4A is sandwiched between the bead part 2a and one longitudinal end of the outer pipe 3 to restrict movement in the longitudinal direction. The other manifold 4B is sandwiched between the other bead part 2b and the other longitudinal end of the outer pipe 3 to restrict movement in the longitudinal direction. Pipe bodies 5a, 5b are respectively connected to the manifolds 4A, 4B by brazing.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a piping structure of a heat exchanger and a manufacturing method thereof, and more particularly to a piping structure of a heat exchanger that can eliminate the complexity of the manufacturing process and suppress thermal deterioration of components during the manufacturing process, and a manufacturing method thereof. [Background technology]

[0002] Various piping structures for heat exchangers have been proposed (see, for example, Patent Document 1). Patent Document 1 describes a double-pipe structure in which a condenser 320 is disposed on the outer periphery of an aluminum alloy pipe 205 between an evaporator 204 and a compressor 201 (see paragraph 0035, Figs. 1 to 8, etc. of Patent Document 1). In the piping structure described in Patent Document 1, end caps 322 and 323 that close both ends of a main body 321 of the condenser 320 are connected to the pipe 205 by brazing. In addition, a refrigerant pipe 330 is connected to the end cap 323 by brazing.

[0003] Conventionally, brazing has been used to improve sealing, but the brazing process requires a lot of time. In addition, there is a risk that the components heated during the brazing process will be thermally deteriorated. Therefore, when manufacturing the piping structure of a heat exchanger, there is room for improvement in reducing the number of brazing points to eliminate the complexity of the manufacturing process and suppressing the thermal deterioration of the components during the manufacturing process. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-148374 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a piping structure for a heat exchanger that can eliminate the complexity of the manufacturing process and suppress thermal deterioration of components during the manufacturing process, and a manufacturing method thereof. [Means for solving the problem]

[0006] In order to achieve the above object, the piping structure of a heat exchanger of the present invention comprises an inner pipe and an outer pipe constituting a double pipe structure, a cylindrical manifold that is inserted around the inner pipe and installed at both longitudinal ends of the outer pipe, and pipe bodies brazed to each of the manifolds, and the longitudinal ends of the outer pipe are sealed by each of the manifolds, a flow path of each of the pipe bodies communicates with an internal space of the brazed manifold, and a flow path between an outer peripheral surface of the inner pipe and an inner peripheral surface of the outer pipe communicates with an outer peripheral region of the inner pipe in the internal space of each of the manifolds. The piping structure of the heat exchanger has an annular sealing material for an outer pipe interposed between each of the manifolds and the outer pipe, an annular sealing material for an inner pipe interposed between each of the manifolds and the inner pipe, and bead portions protruding outward from the outer surface of the inner pipe at intervals in the longitudinal direction of the inner pipe, and one of the manifolds is sandwiched between one of the bead portions and one longitudinal end of the outer pipe, thereby restricting its movement in the longitudinal direction, and the other of the manifolds is sandwiched between the other bead portion and the other longitudinal end of the outer pipe, thereby restricting its movement in the longitudinal direction.

[0007] The method for manufacturing a piping structure of a heat exchanger of the present invention is a method for manufacturing a piping structure of a heat exchanger having a double pipe structure consisting of an inner pipe and an outer pipe, a cylindrical manifold that is inserted onto the inner pipe and installed at both longitudinal ends of the outer pipe, and a tube body brazed to each of the manifolds, the method comprising the steps of forming one bead portion protruding outward on an outer circumferential surface of the inner pipe, inserting one of the manifolds onto the inner pipe and abutting the one bead portion with an annular inner pipe between the one of the manifolds and the inner pipe, the outer pipe is fitted onto the inner pipe, and one of the manifolds is sandwiched between the one bead portion and one longitudinal end of the outer pipe, and the gap between the one of the manifolds and the outer pipe is sealed with an annular sealing material for the outer pipe; the one longitudinal end of the outer pipe is sealed with one of the manifolds; the other manifold is fitted onto the inner pipe, and the outer pipe is sandwiched between the two manifolds, and the gap between the other manifold and the inner pipe is sealed with another annular sealing material for the inner pipe. a second bead portion protruding outwardly from the outer circumferential surface of the inner pipe at a position spaced in the longitudinal direction from the first bead portion of the inner pipe; and a second bead portion protruding outwardly from the outer circumferential surface of the inner pipe at a position spaced in the longitudinal direction from the first bead portion of the inner pipe. The first manifold is sandwiched between the first bead portion and one longitudinal end of the outer pipe to restrict movement in the longitudinal direction. The second manifold is then inserted between the first bead portion and the outer circumferential surface of the inner pipe. The manifold is clamped between the other longitudinal end of the pipe to restrict longitudinal movement, and is installed to connect a flow path between the outer peripheral surface of the inner pipe and the inner peripheral surface of the outer pipe to the outer peripheral region of the inner pipe in the internal space of one of the manifolds and the other of the manifolds, connect a flow path of one of the pipe bodies brazed to one of the manifolds to the internal space of one of the manifolds, and connect a flow path of the other pipe body brazed to the other manifold to the internal space of the other manifold. Effect of the Invention

[0008] According to the present invention, the two bead portions formed at intervals in the longitudinal direction of the inner pipe are used to install the manifolds together with the outer pipe while restricting their longitudinal movement, and the manifolds and the inner pipe are sealed by the annular seal material for the inner pipe, and the manifolds and the outer pipe are sealed by the annular seal material for the outer pipe. The brazing work is only required for connecting the manifolds and the pipe bodies, so that the complication of the manufacturing process of this piping structure can be eliminated. This is advantageous in suppressing the thermal deterioration of the inner pipe and the outer pipe during the manufacturing process. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is an explanatory diagram illustrating an embodiment of a piping structure of a heat exchanger as viewed from the front; [Diagram 2] 2 is an explanatory diagram illustrating the piping structure of FIG. 1 in a vertical cross-sectional view. [Diagram 3] 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] FIG. 3 is a partially enlarged view of FIG. [Diagram 5] 2 is an explanatory diagram illustrating an inner pipe before the piping structure of FIG. 1 is manufactured, as viewed from the front with a lower half in cross section. [Figure 6] 6 is an explanatory view illustrating a state in which one bead portion is formed in the inner pipe of FIG. 5. FIG. [Figure 7] 7 is an explanatory view illustrating a process of extrapolating one manifold onto the inner tube of FIG. 6. FIG. [Figure 8] 8 is an explanatory view illustrating a process of inserting an outer tube onto the inner tube of FIG. 7. [Figure 9] 9 is an explanatory view illustrating a process of extrapolating the other manifold onto the inner tube of FIG. 8. FIG. [Figure 10] 10 is an explanatory view illustrating a state in which the other manifold in FIG. 9 is abutted against the other end of the outer tube in the longitudinal direction. FIG. [Figure 11] 13 is an explanatory diagram illustrating a part of another embodiment of a piping structure in a vertical cross-sectional view. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a piping structure for a heat exchanger and a method for manufacturing the same according to the present invention will be described based on an embodiment shown in the drawings.

[0011] The embodiment of the piping structure of the heat exchanger 1 illustrated in Figs. 1 to 4 includes an inner pipe 2 and an outer pipe 3 constituting a double pipe structure, two cylindrical manifolds 4A, 4B, and two pipes 5a, 5b. Furthermore, this piping structure includes an annular seal material S1, S1 for the outer pipe, an annular seal material S2, S2 for the inner pipe, and bead portions 2a, 2b protruding from the outer peripheral surface of the inner pipe 2 at intervals in the longitudinal direction. One manifold 4A, the outer pipe 3, and the other manifold 4B are arranged in order between the bead portions 2a and 2b. Note that Fig. 4 shows the periphery of the other manifold 4B, but the periphery of the one manifold 4A has the same structure as Fig. 4. The dashed line CL in the figure indicates the cylinder axis of the inner pipe 2, the outer pipe 3, and the manifolds 4A, 4B.

[0012] The inner tube 2, the manifolds 4A, 4B, and the tube bodies 5a, 5b are each made of metal and are formed of a known material, while the outer tube 3 is made of metal or a polymeric material such as resin and is formed of a known material. The outer tube 3 may be made of stainless steel, but the inner tube 2, the outer tube 3, the manifolds 4A, 4B, and the tube bodies 5a, 5b are preferably made of, for example, aluminum or an aluminum alloy, and these parts are preferably made of the same material.

[0013] The sizes of the inner pipe 2, outer pipe 3, and pipe bodies 5a, 5b vary depending on the performance required of the heat exchanger 1, but the outer diameter of the inner pipe 2 is, for example, about 4 mm or more and 500 mm or less, the outer diameter of the outer pipe 3 is, for example, about 8 mm or more and 500 mm or less, and the outer diameter of the pipe bodies 5a, 5b is, for example, about 4 mm or more and 500 mm or less. The sizes of the manifolds 4A, 4B are appropriately set based on the sizes of the inner pipe 2 and the outer pipe 3, etc.

[0014] In this embodiment, each of the bead portions 2a, 2b extends in a ring shape in the circumferential direction on the outer circumferential surface of the inner tube 2. The bead portions 2a, 2b are formed by processing the inner tube 2. The protruding height of the bead portions 2a, 2b toward the outer circumferential side may be a height capable of restricting the movement of each of the manifolds 4A, 4B in the longitudinal direction of the inner tube 2, as described later. The protruding height of the bead portions 2a, 2b varies depending on the outer diameter of the inner tube 2, and is, for example, 2 mm or more. The bead portions 2a, 2b are not limited to the specifications exemplified in this embodiment, and may be any specification capable of restricting the movement of each of the manifolds 4A, 4B in the longitudinal direction of the inner tube 2.

[0015] Each of the manifolds 4A, 4B is fitted onto the inner tube 2 and installed at both longitudinal ends of the outer tube 3. Each of the manifolds 4A, 4B has through holes 4c, 4d at one end and the other end in the axial direction, respectively, and an internal space P3 is formed between the through holes 4c and 4d in the axial direction. In this embodiment, each of the manifolds 4A, 4B has a cylindrical flange portion 4f with a reduced diameter at one end in the axial direction, and the inner peripheral surface of this flange portion 4f forms the through hole 4c.

[0016] The inner pipe 2 passes through the through holes 4c, 4d of one manifold 4A and the through holes 4c, 4d of the other manifold 4B. The flange portion 4f of one manifold 4A is inserted into one longitudinal end of the outer pipe 3, and the flange portion 4f of the other manifold 4B is inserted into the other longitudinal end of the outer pipe 3. Both longitudinal ends of the outer pipe 3 are sealed by the manifolds 4A and 4B. It is preferable to make the gap between the inner peripheral surface of the outer pipe 3 and the outer peripheral surface of each flange portion 4f as small as possible, for example, 1 mm or less. It is also preferable to make the gap between the outer peripheral surface of the inner pipe 2 and the inner peripheral surface of each through hole 4d as small as possible, for example, 1 mm or less.

[0017] More specifically, a seal material S1, S1 is interposed between each of the manifolds 4A, 4B and the outer pipe 3, and a seal material S2, S2 is interposed between each of the manifolds 4A, 4B and the inner pipe 2. In this embodiment, the seal material S1, S1 is disposed between the outer peripheral surface of each of the flange portions 4f, 4f and the inner peripheral surface of the outer pipe 3, sealing the gaps between them. In addition, the seal material S2, S2 is disposed between the outer peripheral surface of the inner pipe 2 and the inner peripheral surface of each of the through holes 4d, 4d, sealing the gaps between them. Each of the seal materials S2, S2 is disposed at a position where it does not come into contact with the adjacent bead portions 2a, 2b.

[0018] One longitudinal end face of the outer pipe 3 abuts against an end face of one manifold 4A that is closer to the outer periphery than the flange portion 4f. Similarly, the other longitudinal end face of the outer pipe 3 abuts against an end face of the other manifold 4B that is closer to the outer periphery than the flange portion 4f. One manifold 4A is engaged with one bead portion 2a, with its end face abutting against the bead portion 2a. Similarly, the other manifold 4B is engaged with the other bead portion 2b, with its end face abutting against the bead portion 2b. As a result, both longitudinal ends of the outer pipe 3 are hermetically sealed by the manifolds 4A and 4B.

[0019] Various known sealing materials that seal gaps airtightly can be used for the sealing materials S1 and S2. Specifically, O-rings made of various known elastic materials such as silicone rubber, various gaskets, various packings, various adhesives, etc. can be used as the sealing materials S1 and S2.

[0020] In this piping structure, one manifold 4A is sandwiched between one bead portion 2a and one longitudinal end of the outer pipe 3, and installed with its longitudinal movement restricted. The other manifold 4B is sandwiched between the other bead portion 2b and the other longitudinal end of the outer pipe 3, and installed with its longitudinal movement restricted. Therefore, one manifold 4A, the outer pipe 3, and the other manifold 4B are installed between the bead portion 2a and the bead portion 2b, and are substantially fixed with respect to the longitudinal direction of the inner pipe 2.

[0021] One tube 5a is brazed to the outer circumferential surface of one manifold 4A, and the other tube 5b is brazed to the outer circumferential surface of the other manifold 4b. These manifolds 4A, 4B and the tubes 5a, 5b are brazed using a known brazing material suitable for the materials thereof.

[0022] The flow path P2 of one tube body 5a communicates with the internal space P3 of one manifold 4A brazed to the tube body 5a. The flow path P2 of the other tube body 5b communicates with the internal space P3 of the other manifold 4B brazed to the tube body 5b. The flow path P1 between the outer peripheral surface of the inner tube 2 and the inner peripheral surface of the outer tube 3 communicates with the outer peripheral side regions of the inner tube 2 in the internal spaces P3, P3 of each manifold 4A, 4B. Therefore, the flow path P2 of one tube body 5a communicates with the outer peripheral side region of the inner tube 2 in the internal space P3 of one manifold 4A, the flow path P1 between the outer peripheral surface of the inner tube 2 and the inner peripheral surface of the outer tube 3, the outer peripheral side region of the inner tube 2 in the internal space P3 of the other manifold 4B, and the flow path P2 of the other tube body 5b.

[0023] As illustrated in FIG. 2, the high-temperature fluid HF flows from the flow path P2 of one tube body 5a through the outer peripheral region of the inner tube 2 in the internal space P3 of one manifold 4A, the flow path P1 between the outer peripheral surface of the inner tube 2 and the inner peripheral surface of the outer tube 3, and the outer peripheral region of the inner tube 2 in the internal space P3 of the other manifold 4B, and then flows into the flow path P2 of the other tube body 5b. The low-temperature fluid LF flows through the flow path of the inner tube 2. Between the inner tube 2 and the outer tube 3 of the double-tube structure, the thermal energy of the high-temperature fluid HF is transferred to the low-temperature fluid LF, so that the temperature of the high-temperature fluid HF decreases and the temperature of the low-temperature fluid LF increases. In this way, in the heat exchanger 1, heat exchange is performed between the high-temperature fluid HF and the low-temperature fluid LF. This heat exchanger 1 is applied to, for example, air conditioners installed in vehicles such as automobiles, and air conditioners installed in houses, factories, and various facilities.

[0024] An example of a procedure for manufacturing the piping structure of the heat exchanger 1 will now be described.

[0025] As shown in Fig. 5, an inner pipe 2 of a predetermined length is prepared. Next, as shown in Fig. 6, one bead portion 2a that protrudes outward is formed at one location on the outer circumferential surface of the inner pipe 2. The bead portion 2a may be formed by a known method. For example, the inner pipe 2 is subjected to bead processing (stringing processing) to cause a part of the inner pipe 2 to protrude outward, thereby forming the bead portion 2a.

[0026] Next, as shown in FIG. 7, one manifold 4A is fitted onto the inner pipe 2. Sealing materials S1 and S2 are attached to this manifold 4A in advance. One tube body 5a is brazed to the outer circumferential surface of the manifold 4A. The end face of the manifold 4A facing one bead portion 2a is then abutted against the bead portion 2a. As a result, the gap between the manifold 4A and the inner pipe 2 is sealed by the sealing material S2, as shown in FIG. 8.

[0027] Next, as shown in Fig. 8, the outer pipe 3 is fitted onto the inner pipe 2, and the longitudinal end face of the outer pipe 3 facing the manifold 4A is abutted against the end face of the manifold 4A. As a result, the gap between the manifold 4A and the outer pipe 3 is sealed with the sealant S1 at a position where the manifold 4A is sandwiched between one bead portion 2a and one longitudinal end of the outer pipe 3, as shown in Fig. 9. As a result, one longitudinal end of the outer pipe 3 is sealed by the manifold 4A.

[0028] Next, as shown in FIG. 9, the other manifold 4B is fitted onto the inner tube 2. The seal materials S1 and S2 are attached to this manifold 4B in advance. The other tube body 5b is brazed to the outer peripheral surface of the manifold 4B. The end face of the manifold 4B facing the outer tube 3 is then abutted against the outer tube 3. As a result, as shown in FIG. 10, at the position where the outer tube 3 is sandwiched between the manifold 4A and the manifold 4B, the gap between the manifold 4B and the inner tube 2 is sealed with the seal material S2, and the gap between the manifold 4B and the outer tube 3 is sealed with the seal material S1. As a result, the other longitudinal end of the outer tube 3 is sealed by the manifold 4B.

[0029] Next, the other bead portion 2b that protrudes outward is formed on the outer circumferential surface of the inner pipe 2 so as to be adjacent to the manifold 4B, thereby manufacturing the piping structure illustrated in Fig. 2. The method of forming the other bead portion 2b is the same as that of the one bead portion 2a.

[0030] According to the piping structure of the heat exchanger 1 described above, the manifolds 4A, 4B can be installed together with the outer pipe 3 while restricting their movement in the longitudinal direction by using the two bead portions 2a, 2b formed at intervals in the longitudinal direction of the inner pipe 2. In addition, the manifolds 4A, 4B and the inner pipe 2 are sealed by the respective seal materials S2, S2, and the manifolds 4A, 4B and the outer pipe 3 are sealed by the respective seal materials S1, S1. Brazing work is only required for connecting the manifolds 4A, 4B and the corresponding pipe bodies 5a, 5b. The work of brazing and connecting while ensuring airtightness requires a considerable amount of time and high skill. Therefore, according to this embodiment in which the brazing points are limited to only two places, it greatly contributes to eliminating the complexity of the manufacturing process of this piping structure. Accordingly, in this manufacturing process, the inner pipe 2 and the outer pipe 3 are not heated by the brazing work, which is advantageous in suppressing thermal deterioration of the inner pipe 2 and the outer pipe 3.

[0031] In this embodiment, one manifold 4A is brazed to one tube body 5a before being fitted around the inner tube 2. Also, the other manifold 4B is brazed to the other tube body 5b before being fitted around the inner tube 2. If the manifolds 4A, 4B are brazed to the corresponding tube bodies 5a, 5b before being assembled together with the inner tube 2, the outer tube 3, and the manifolds 4A, 4B as in this embodiment, the assembly process is further simplified.

[0032] It is also possible to install one manifold 4A by clamping it between one bead portion 2a and one longitudinal end of the outer pipe 3 to restrict its longitudinal movement, and install the other manifold 4B by clamping it between the other bead portion 2b and the other longitudinal end of the outer pipe 3 to restrict its longitudinal movement, and then braze each of the manifolds 4A, 4B to the corresponding tube bodies 5a, 5b. By following this procedure, it is possible to prevent the tube bodies 5a, 5b from getting in the way during the process of assembling the inner pipe 2, the outer pipe 3, and the manifolds 4A, 4B.

[0033] The embodiment illustrated in FIG. 11 differs from the previous embodiment only in the arrangement of the seal material S2. In this embodiment, the seal materials S2, S2 are arranged between the outer circumferential surface of the inner tube 2 and the inner circumferential surfaces of the through holes 4d, 4d of the manifolds 4A, 4B, respectively, to seal the gaps between them. Each seal material S2, S2 is arranged at a position where it contacts the adjacent bead portions 2a, 2b. That is, the other seal material S2 is arranged so as to be exposed on the end surface of the manifold 4B facing the bead portion 2b. Similarly, one seal material S2 is arranged so as to be exposed on the end surface of the manifold 4A facing the bead portion 2a. In this embodiment, the seal material S2 simultaneously seals the gaps between the manifolds 4A, 4B and the outer circumferential surface of the inner tube 2, and the gaps between the manifolds 4A, 4B and the bead portions 2a, 2b facing the manifolds 4A, 4B. [Explanation of symbols]

[0034] 1 heat exchanger 2 Inner tube 2a, 2b Bead section 3 outer tube 4A, 4B manifold 4c, 4d through hole 4f Flange part 5a, 5b Body S1 Annular seal for outer pipe S2 Annular seal for inner pipe P1, P2 flow path P3 interior space LF Cryogenic fluid HF high temperature fluid

Claims

1. The device has an inner pipe and an outer pipe that form a double pipe structure, a cylindrical manifold that is inserted around the inner pipe and installed at both ends of the outer pipe in the longitudinal direction, and a pipe body that is brazed to each of the manifolds, In a piping structure of a heat exchanger, longitudinal ends of the outer tube are sealed by the manifolds, flow paths of the tube bodies are in communication with internal spaces of the brazed manifolds, and flow paths between an outer circumferential surface of the inner tube and an inner circumferential surface of the outer tube are in communication with an outer circumferential side region of the inner tube in the internal spaces of the manifolds, A piping structure for a heat exchanger having annular sealing material for an outer pipe interposed between each of the manifolds and the outer pipe, annular sealing material for an inner pipe interposed between each of the manifolds and the inner pipe, and bead portions protruding outward from the outer surface of the inner pipe at intervals in the longitudinal direction of the inner pipe, wherein one of the manifolds is sandwiched between one of the bead portions and one longitudinal end of the outer pipe, thereby restricting its longitudinal movement, and the other manifold is sandwiched between the other bead portion and the other longitudinal end of the outer pipe, thereby restricting its longitudinal movement.

2. 2. The piping structure of a heat exchanger as described in claim 1, wherein each of the manifolds has a cylindrical flange portion that is inserted into the outer pipe, and an annular seal material for the outer pipe is arranged between the outer peripheral surface of each of the flange portions and the inner peripheral surface of the outer pipe.

3. 3. A piping structure of a heat exchanger as described in claim 1 or 2, wherein each of the manifolds has a through hole through which the inner pipe passes near an adjacent bead portion, and an annular sealing material for the inner pipe is disposed between the inner surface of each of the through holes and the outer surface of the inner pipe.

4. 4. The piping structure of a heat exchanger according to claim 3, wherein each of the annular sealing members for the inner pipe is disposed at a position where it does not come into contact with an adjacent one of the bead portions.

5. A method for manufacturing a piping structure of a heat exchanger having a double-pipe structure of an inner pipe and an outer pipe, a cylindrical manifold that is inserted around the inner pipe and installed at both longitudinal ends of the outer pipe, and a pipe body brazed to each of the manifolds, comprising: forming one bead portion protruding outward on an outer circumferential surface of the inner pipe, and fitting one of the manifolds onto the inner pipe so that the one manifold and the inner pipe are sealed at a position where the one manifold abuts against the one bead portion with an annular seal material for the inner pipe; the outer pipe is fitted onto the inner pipe, and a gap between the one manifold and the outer pipe is sealed with an annular seal material for the outer pipe at a position where the one bead portion and one longitudinal end of the outer pipe sandwich the one manifold, thereby sealing the one longitudinal end of the outer pipe with the one manifold; the other manifold is inserted onto the inner pipe at a position where the outer pipe is sandwiched between the manifolds, the gap between the other manifold and the inner pipe is sealed with another annular seal material for the inner pipe, and the gap between the other manifold and the outer pipe is sealed with another annular seal material for the outer pipe, and the other longitudinal end of the outer pipe is sealed with the other manifold; a second bead portion protruding outward is formed on an outer peripheral surface of the inner pipe at a position spaced apart from the first bead portion in the longitudinal direction of the inner pipe, one of the manifolds is sandwiched between the first bead portion and one longitudinal end of the outer pipe to restrict movement in the longitudinal direction, and the other manifold is sandwiched between the other bead portion and the other longitudinal end of the outer pipe to restrict movement in the longitudinal direction, A manufacturing method for a piping structure of a heat exchanger, which connects a flow path between the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube with an outer peripheral region of the inner tube in the internal space of one of the manifolds and the other of the manifolds, connects a flow path of one of the tube bodies brazed to one of the manifolds with the internal space of one of the manifolds, and connects a flow path of the other of the tube bodies brazed to the other manifold with the internal space of the other manifold.

6. 6. A method for manufacturing a piping structure of a heat exchanger according to claim 5, wherein one of the manifolds is brazed to one of the pipe bodies before the one of the manifolds is externally fitted onto the inner pipe, and the other of the manifolds is brazed to the other of the pipe bodies before the other of the manifolds is externally fitted onto the inner pipe.

7. 6. A method for manufacturing a piping structure of a heat exchanger as claimed in claim 5, further comprising the steps of: installing one of the manifolds by clamping it between one of the bead portions and one longitudinal end of the outer tube to restrict its longitudinal movement; and installing the other of the manifolds by clamping it between the other of the bead portions and the other longitudinal end of the outer tube to restrict its longitudinal movement; and then brazing one of the manifolds to the one of the tube bodies and brazing the other of the manifolds to the other of the tube bodies.

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