WO2007108240A1 - Heat exchanger - Google Patents

Abstract

A heat exchanger (100) is provided with a box body (14) forming a rectangular first flow channel (14s) wherein water flows, and a piping unit (21) arranged in the first flow channel (14s). The piping unit (21) is composed of a first cooling medium pipe (17) and a second cooling medium pipe (19). The positional relationship between the first cooling medium pipe (17) and the second cooling medium pipe (19) is fixed so that the pipes intersect at a plurality of areas along a water flow direction (FL). Water flows in the first flow channel (14s) to thread through a space generated by the first cooling medium pipe (17) and the second cooling medium pipe (19).

Description

 Specification

 Heat exchanger

 Technical field

 [0001] The present invention relates to a heat exchanger for exchanging heat between a first fluid and a second fluid, and more particularly to a heat exchanger suitable for a heat pump type hot water heater.

 Background art

 [0002] Heat exchange for heat exchange between two types of fluids (for example, water and refrigerant, air and refrigerant) compared to conventional heat pump hot water heaters, air conditioners, floor heating devices, etc. A vessel is being used. A few examples of such heat exchangers are briefly described.

[0003] For example, in Japanese Patent Laid-Open No. 2003-90690 (page 7, Fig. 1), heat exchange using a fluid pipe bent in a zigzag shape is used in order to increase the heat exchange efficiency by stirring the fluid. The vessel is listed.

 [0004] In JP 2003-314975 A (page 4, FIG. 1), a pipe forming a first fluid passage is spirally wound around a container forming a second fluid passage. A heat exchanger is listed. According to this heat exchanger, it is easy to take a long passage for the second fluid, and the wall surface of the container can be used as a heat transfer surface on which heat exchange is performed.

 [0005] Further, Japanese Patent Application Laid-Open No. 2005-24109 describes a box-type heat exchanger in which heat transfer tubes are arranged in a rectangular fluid passage. Since this heat exchanger directly transfers heat between the heat transfer tube wall and the fluid to be heated (for example, water), it can be miniaturized with high heat exchange efficiency.

[0006] However, in the configuration of the heat exchanger described in Japanese Patent Application Laid-Open No. 2003-90690, the plate to which the heat transfer tubes are joined is planar, so that the first fluid spreads uniformly over the entire plate. It is difficult to exchange heat efficiently. In addition, a large stirring effect cannot be obtained in the first fluid, and the temperature boundary layer of the first fluid tends to develop in the vicinity of the heat transfer surface. The development of a temperature boundary layer is not preferable because it prevents efficient heat exchange. The problem that the temperature boundary layer easily develops also exists in the heat exchanger described in Japanese Patent Application Laid-Open No. 2005-24109. [0007] Further, in the configuration of the heat exchanger described in Japanese Patent Laid-Open No. 2003-314975, the fluid flowing in the container does not directly contact the piping. Therefore, there is a problem that it is easily affected by heat radiation from the outside piping to the outside air. In addition, in order to perform efficient heat exchange, it is necessary to form a flow path so that the flow of the first fluid and the flow of the second fluid are opposed to each other. If it tries to do so, the process of winding piping around the outside of the container may become complicated.

 Disclosure of the invention

 [0008] Thus, the force S for which various types of heat exchangers have been proposed, all still have room for improvement. An object of the present invention is to provide a heat exchanger that is excellent in heat exchange efficiency and can be further reduced in size.

[0009] That is, the present invention includes a box body in which a first flow path having a rectangular outer shape that appears in a cross section perpendicular to the flow direction of the first fluid is formed,

 A piping unit disposed in the first flow path and forming a second flow path through which a second fluid to be heat exchanged with the first fluid flows,

 Of the two pairs of opposite sides that form the rectangular outer shape of the first flow path in the cross section, when the direction parallel to the predetermined pair of opposite sides is defined as the width direction of the first flow path,

 The piping unit

 A first pipe whose shape is adjusted so that the center of the pipe draws a serpentine first locus in the plane of the first reference plane which is a plane parallel to both the width direction and the flow direction of the first fluid; A second pipe whose shape is adjusted so that the center of the pipe draws a meandering second locus within the plane of the second reference plane, which is a plane parallel to the first reference plane,

 When the first pipe and the second pipe are observed from a direction orthogonal to the first reference plane, the positional relationship between the first pipe and the second pipe is determined so as to intersect at a plurality of locations along the flow direction of the first fluid. Provide heat exchanger.

[0010] According to the heat exchanger of the present invention, the first pipe and the second pipe constituting the pipe unit each have a meandering shape in separate planes (first reference plane and second reference plane). Have. In addition, the positional relationship between the first pipe and the second pipe is determined so as to intersect at a plurality of locations along the flow direction of the first fluid. The first fluid is at the intersection of the first pipe and the second pipe. It flows through the first flow path so as to sew the space formed on the basis thereof. As described above, according to the present invention, it is possible to induce a three-dimensional flow of the first fluid, that is, a complicated flow whose direction changes vertically and horizontally. As a result, the temperature boundary layer can be prevented from reaching around the first pipe and the second pipe. Suppressing the development of the temperature boundary layer contributes to improving the heat exchange efficiency. In addition, since the first pipe and the second pipe meander in the flow direction of the first fluid, the ratio of the total length of the first pipe and the second pipe to the total length of the first flow path can be increased. it can. According to the present invention, these powers can be easily reduced in size as compared with a heat exchanger having comparable performance.

 Brief Description of Drawings

 FIG. 1 is an overall perspective view of a heat exchanger according to an embodiment of the present invention.

 [Figure 2] Exploded plan view of the box shown in Figure 1

 [Figure 3] Exploded plan view of heat exchanger shown in Figure 1

 [Fig.4] AA cross section of Fig.3

 [Fig.5] BB cross section of Fig.3

 FIG. 6A is a conceptual diagram illustrating the shape and arrangement of refrigerant tubes

 [Figure 6B] Schematic plan view of the locus drawn by the center of the refrigerant pipe

 [Figure 7] Partial enlarged view of Figure 3

 [FIG. 8A] Action explanatory diagram showing the flow of water in a conventional heat exchanger

 [FIG. 8B] Action explanatory diagram following FIG. 8A

 FIG. 9A is an operation explanatory diagram showing the flow of water in the heat exchanger of the present embodiment.

 [FIG. 9B] Action explanatory diagram following FIG. 9A

 [FIG. 10A] Action explanatory diagram showing the flow of water in another conventional heat exchanger

 FIG. 10B is an operation explanatory diagram showing the flow of water in the heat exchanger of the present embodiment.

 [Figure 11] Cross section of leak detection tube

 BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

In the present embodiment, a heat exchanger that is used in equipment such as a heat pump type hot water heater and performs heat exchange between water (first fluid) and a refrigerant (second fluid) such as carbon dioxide or alternative chlorofluorocarbon. For example I will give you a description.

 FIG. 1 is an overall perspective view of the heat exchanger of the present embodiment. As shown in FIG. 1, the heat exchanger 100 includes a box 14 and a piping unit 21. The piping unit 21 includes two refrigerant pipes, a first refrigerant pipe 17 (first pipe) and a second refrigerant pipe 19 (second pipe), most of which are accommodated in the box body 14. The box body 14 has a box body 12 and a lid 13. An inlet pipe 15 for allowing water to flow into the box body 14 and an outlet pipe 16 for discharging water from the box body 14 are welded to the peripheral edge of the lid 13. The box body 12 has four holes in total, two near the water inlet and two near the outlet, through which the piping unit 21 consisting of two refrigerant pipes 17 and 19 is placed in the box. Guided inside body 14.

 FIG. 2 is an exploded plan view of the box shown in FIG. However, the refrigerant pipes 17 and 19 are omitted. The internal space of the box 14 has a flat rectangular parallelepiped shape. The sealed internal space constitutes the first flow path 14s through which water flows. The first channel 14s has a rectangular outer shape that appears on the cross section perpendicular to the water flow direction FL. The water flowing in from the inlet pipe 15 flows through the first flow path 14 s and flows out from the outlet pipe 16. Further, the box body 14 has a plurality of partition plates 25 arranged in its internal space. The partition plates 25 are arranged in the box body 12 in parallel with each other at equal intervals in the width direction WL, and the first flow paths 14s in which the water flow direction FL is opposite by 180 degrees are alternately formed in the width direction WL. As shown, the internal space of the box 14 is partially partitioned. By these partition plates 25, the first flow path 14 s forms a so-called single-tain flow path (meandering flow path). The serpentine-type flow path is advantageous for saving useless space in the box 14. The first flow path 14s is formed side by side in the height direction HL perpendicular to the water flow direction FL and the width direction WL.

 [0015] The box body 12, the lid 13, and the partition plate 25 constituting the box body 14 can be made of a metal having good thermal conductivity, such as copper, copper alloy, SUS, aluminum alloy, or the like. . The lid 13 and the partition plate 25 can be joined to the box body 12 by brazing or welding.

On the other hand, the refrigerant pipes 17 and 19 constituting the piping unit 21 are arranged in the first flow path 14s, and form second flow paths 17s and 19s through which a refrigerant to be heat-exchanged with water flows, respectively. Such refrigerant pipes 17 and 19 are made of a metal having good thermal conductivity similar to that of the box body 14. An internally grooved tube made can be used. Preferably, a leak detection tube 32 having a structure in which a small-diameter inner grooved tube 30 is covered with a large-diameter inner grooved tube 31 as shown in FIG. According to such a leakage detection tube 32, by any chance, even if the inside of the inner surface grooved tube 30 is damaged, the container refrigerant Ya lubricating oil along the grooves 31 _P outside the inner surface grooved tube 31 14 The refrigerant can prevent the lubricating oil from entering the water. In the present embodiment, the refrigerant pipes 17 and 19 are formed by bending a common leak detection pipe 32. The refrigerant pipes 17 and 19 can be smooth inner pipes.

 Next, FIG. 3 shows an exploded plan view of the heat exchanger shown in FIG. 1. FIG. 4 is a cross-sectional view taken along line AA in FIG. 3, and FIG. 5 is a cross-sectional view taken along line BB in FIG. It has become. As shown in FIG. 3, each of the first refrigerant pipe 17 and the second refrigerant pipe 19 has a meandering shape with respect to the flow direction FL of water in the first flow path 14s, and one end of the first flow path 14s ( It is arranged over almost the entire area from the inlet pipe 15) to the other end (outlet pipe 16). In addition, as shown in FIGS. 4 and 5, the first refrigerant pipe 17 and the second refrigerant pipe 19 are arranged so as to be overlapped in two upper and lower stages in the first flow path 14s. The first refrigerant pipe 17 occupies the upper half space of the first flow path 14s, and the second refrigerant pipe 19 occupies the lower half space of the first flow path 14s.

 [0018] The shape of the refrigerant tubes 17 and 19 and the arrangement in the box 14 will be described in detail.

 As shown in the conceptual diagram of FIG. 6A, the width direction WL of the first flow path 14s is a predetermined one of the two opposite sides forming the rectangular outer shape of the first flow path 14s in a cross section perpendicular to the water flow direction FL. Can be defined as a direction parallel to the opposite side (long side in the present embodiment). The direction perpendicular to the width direction WL and the water flow direction FL can be defined as the height direction HL. The virtual plane parallel to both the width direction WL and the water flow direction FL is defined as the first reference plane P1, and the virtual plane parallel to the first reference plane P1 is defined as the second reference plane P2. Is possible. In the present embodiment, the stacking direction of the first refrigerant pipe 17 and the second refrigerant pipe 19 coincides with the height direction HL, and the swinging direction of the refrigerant pipes 17 and 19 coincides with the width direction WL. If the dimension of the first flow path 14s with respect to the height direction HL is D, the first reference plane P1 is in the height direction HL.

 h

 A virtual plane passing through the position of D / 4 from one wall 141k (upper surface) of the box 14

 h

 Can be defined. The second reference plane P2 is D / 4 from the other wall 142k (bottom surface).

h Can be defined as a virtual plane passing through the position. FIG. 6B shows a schematic plan view of a locus drawn by the center of the refrigerant pipe. The shape of the first refrigerant pipe 17 is adjusted so that the center of the pipe draws a meandering first locus 17c in the plane of the first reference plane P1. Similarly, the shape of the second refrigerant pipe 19 is adjusted so that the center of the pipe draws a meandering second locus 19c in the plane of the second reference plane P2. In the present embodiment, the first trajectory 17c and the second trajectory 19c each show a periodicity, specifically, a sinusoidal shape. Furthermore, the first refrigerant pipe 17 and the second refrigerant pipe 19 have a positional relationship with each other so as to intersect at a plurality of locations along the water flow direction FL when the directional force perpendicular to the first reference plane P1 is observed. It has been established. Water flows through the first flow path 14s so as to sew a space generated based on the intersection of the first refrigerant pipe 17 and the second refrigerant pipe 19.

 Further, as shown in the partially enlarged view of FIG. 7, the first refrigerant pipe 17 and the second refrigerant pipe 19 are arranged so that the intersecting positions of the two appear at equal intervals t along the water flow direction FL. Each shape is adjusted and the positional relationship with each other is determined. That is, in the straight section of the first flow path 14s, the bent shape of the first refrigerant pipe 17 and the bent shape of the second refrigerant pipe 19 can be made common. In this way, the refrigerant tubes 17 and 19 can be easily manufactured. Further, since the entire structure is simplified, it becomes easy to optimize design conditions such as the bent shape of the refrigerant pipes 17 and 19 and the width of the first flow path 14s by computer simulation, for example.

 More specifically, in the water flow direction FL, the meandering phase of the first locus 17c described in FIGS. 6A and 6B and the meandering phase of the second locus 19c are shifted by a half cycle (180 degrees). The positional relationship between the first refrigerant pipe 17 and the second refrigerant pipe 19 can be determined. In this way, the effect of inducing a three-dimensional water flow can be sufficiently obtained. The width D in the width direction WL of the region surrounded by the first refrigerant pipe 17 and the second refrigerant pipe 19 as shown in FIG.

 1 can be larger than the diameter (outer diameter) of the refrigerant pipes 17 and 19. By doing so, the water flow in the area becomes smooth. The meandering phase shift need not be strictly a half cycle. For example, about 180 ± 10 degrees is included within a half cycle shift.

[0022] Further, as shown in FIG. 3, in the reversal section in which the direction of the first flow path 14s is reversed by 180 degrees, the refrigerant pipes 17 and 19 need to change the direction by 180 degrees. In the present embodiment, in the inversion section, the first refrigerant pipe 17 and the second refrigerant pipe 19 maintain a positional relationship that is shifted inward and outward from each other. The direction is changed 180 degrees while holding. In this way, it is possible to prevent the formation of a region where water flows easily (so-called dead water region). For example, of the two refrigerant tubes 17 and 19, one refrigerant tube is bent and bent so as to change the direction while contacting the wall surface of the box 14 forming the end of the first flow path 14s, and the other The refrigerant pipe is bent and curved so that it passes through the inside with a smaller arc. In this way, it is possible to prevent a large dead water area from being formed in the reversal section where the direction of the first flow path 14s is reversed by 180 degrees.

 [0023] Further, as shown in FIG. 6A, the parallel distance D / 2 between the first reference plane P1 and the second reference plane P2 is

 h The positional relationship between the first refrigerant pipe 17 and the second refrigerant pipe 19 is determined so as to be equal to the diameter (outer diameter) of the pipe. That is, the first refrigerant pipe 17 and the second refrigerant pipe 19 are in point contact with each other at the crossing positions. If the contact point between the first refrigerant pipe 17 and the second refrigerant pipe 19 is prevented from being connected in a linear manner, the flow path of the water can be prevented from being blocked, and the active three-dimensional flow can be prevented. The effect of preventing the increase in pressure loss can be expected.

Further, the box body 14 is adjusted so that the height of the first flow path 14 s is approximately equal to the sum of the diameter of the first refrigerant pipe 17 and the diameter of the second refrigerant pipe 19. That is, as shown in FIGS. 3 and 4, the first refrigerant pipe 17 and the second refrigerant pipe 19 are in contact with the inner wall surfaces 14p, 14p, 141k, and 142k of the box body 14 in the upper, lower, left and right directions in the first flow path 14s. . That is, when the first flow path 14s is projected from one end to the other side in the flow direction FL, the inner wall surface on the opposite side of the box body 14 is blocked by the refrigerant pipes 17 and 19 so that it cannot be seen. ing. When the refrigerant tubes 17 and 19 are brought into contact with the box body 14 in this way, it is possible to suppress the generation of a linear flow along the inner wall surfaces 14p, 14p, 141k, and 142k of the box body 14. As described later, suppressing the linear flow results in suppressing the formation of a thick temperature boundary layer, which contributes to the realization of efficient heat exchange. In addition, an effect that heat transfer from the refrigerant pipes 17 and 19 to the box 14 becomes active can be expected.

[0025] As shown in Figs. 3 and 4, the first refrigerant pipe 17 and the second refrigerant pipe 19 are each in contact with the inner wall surface 14p of the box body 14 in the width direction WL of the first flow path 14s. It has a meandering amplitude that enables heat transfer with the body 14. That is, the amplitude of the refrigerant pipes 17 and 19 is equal to the width of the first flow path 14s. By bringing the refrigerant pipes 17 and 19 into contact with the inner wall surface 14p of the box 14 The direct heat flow from the refrigerant tubes 17 and 19 to the box body 14 can be promoted. As a result, the box 14 itself can be used as a heat transfer surface, so that the heat exchange efficiency is increased. In the present embodiment, by causing the refrigerant tubes 17 and 19 to meander, a plurality of contact points between the refrigerant tubes 17 and 19 and the inner wall surface 14p of the box body 14 appear at a predetermined interval t along the water flow direction FL. I am doing so. In this way, the heat flow from the refrigerant pipes 17 and 19 to the box body 14 becomes more active. Each refrigerant pipe 17, 19 may be in direct contact with the box body 14, or may be in indirect contact with another heat transfer section 27 as in the present embodiment.

[0026] In addition, by making the refrigerant pipes 17 and 19 meander significantly, the ratio of the total length of the refrigerant pipes 17 and 19 to the total length of the first flow path 14s can be increased, so that the heat exchanger 100 can be downsized. It is advantageous.

 [0027] Specific examples of the other heat transfer section 27 that indirectly contact the refrigerant pipes 17 and 19 and the box body 14 include the box body 14 and the first refrigerant pipe 17, and the box body 14 and the second refrigerant pipe. This is a brazed joint 27 for joining 19. Such a brazed joint 27 is suitable because it can be easily formed as follows. Placing the refrigerant pipes 17 and 19 (piping unit 21) into the box while placing the brazing material previously formed into a sheet shape between the inner wall surfaces 14p, 14p, 141k and 142k of the box 14 and the refrigerant pipes 17 and 19 14 Place in. Then, the brazing material is melted and solidified in the heating furnace, and the box body 14 and the refrigerant pipes 17 and 19 are joined. The first refrigerant pipe 17 and the second refrigerant pipe 19 may be joined by brazing or welding.

 [0028] The box body 14 and / or the refrigerant pipes 17 and 19 may be made of a non-metallic material such as a resin. Non-metallic materials represented by resins generally have the advantage of being lighter than metallic materials. Also, the resin is generally less expensive than the metal material. As such a non-metallic material, it is preferable to use a material having high thermal conductivity. An example of a nonmetallic material having good thermal conductivity is a resin containing a thermal conductive filler. When both the box body 14 and the refrigerant pipes 17 and 19 are made of a resin containing a heat conductive filler, an adhesive having an improved heat conductivity (for example, a polymer adhesive kneaded with metal powder) is used to The body 14 can be brought into contact with the refrigerant pipes 17 and 19. By doing so, the inner wall surface of the box 14 can be used as a heat transfer surface, so that the heat exchange efficiency can be increased.

[0029] Next, the operation of the heat exchanger 100 of the present embodiment will be described. The water guided from the inlet pipe 15 into the box body 14 flows through the first flow path 14s toward the outlet pipe 16 on the downstream side. Since the refrigerant pipes 17 and 19 are bent so as to intersect the water flow direction FL, water flows over the second refrigerant pipe 19 and flows under the first refrigerant pipe 17. Flows alternately and flows out of the box 14 from the outlet pipe 16. On the other hand, the high-temperature and high-pressure refrigerant heated by the compressor or the like is guided into the refrigerant pipes 17 and 19 from the side close to the outlet pipe 16. That is, the water flowing through the first flow path 14s and the high-temperature and high-pressure refrigerant flowing through the refrigerant pipes 17 and 19 flow opposite to each other. In this way, the efficiency of heat exchange between water and the refrigerant can be increased.

As shown in FIG. 8A, consider a case where water flows straight along the longitudinal direction outside the refrigerant pipe 171. In this case, since the stirring action received from the refrigerant pipe 171 is small, the water as shown in FIG. 8B has a relatively large temperature δ in the vicinity of the surface of the refrigerant pipe 171.

 0 Flows while forming a boundary layer. When the thickness δ of the temperature boundary layer is large, efficient heat exchange is achieved.

 0

 Be disturbed.

 [0031] On the other hand, consider the case where the two refrigerant pipes 17, 19 are arranged vertically so as to intersect as shown in FIG. 9B. In this case, the water first flows so as to get over one refrigerant pipe 17 located on the upstream side. Since the other refrigerant pipe 19 exists at the position where it has been overcome, it cannot proceed straight as it is, and this time it flows under the refrigerant pipe 19. When such a flow exists, the temperature boundary layer formed near the surface of the refrigerant pipes 17 and 19 as shown in Fig. 9 (b) flows straight along the longitudinal direction of the pipe (see Figs. 8 (b) and 8 (b)). It is thicker and harder to grow. The thickness δ of the temperature boundary layer shown in Fig. 9Β is the temperature shown in Fig. 8Β.

 1

 This is much smaller than the boundary layer thickness δ. That is, the heat exchanger 100 of the present embodiment

 0

 By actively creating a flow in a direction that intersects the longitudinal direction of the refrigerant pipes 17 and 19 as described above, it is possible to prevent the temperature boundary layer from becoming thicker and thus to perform efficient heat exchange. become.

[0032] Further, according to the heat exchanger 100 of the present embodiment, most of the surfaces of the refrigerant tubes 17 and 19 can contribute to heat transfer. For example, consider a piping unit 211 in which two refrigerant tubes 172 and 174 are spirally twisted as shown in FIG. 10A. According to such a piping unit 211, since water tends to flow along the periphery of the piping unit 211, the two refrigerant tubes 172, The surface of 174 cannot necessarily be effectively used.

 [0033] On the other hand, according to the heat exchanger 100 of the present embodiment, as shown in FIG. 10B, the first refrigerant pipe 17 and the second refrigerant pipe 19 create a moderately large space between them. However, since it is meandering, water forms a complex flow in that space. Since water flows while colliding with the surfaces of both the first refrigerant pipe 17 and the second refrigerant pipe 19, the surfaces of the first refrigerant pipe 17 and the second refrigerant pipe 19 can be effectively used as heat transfer surfaces. In addition, the dead water area can be reduced. As the dead water area becomes smaller, the heat transfer area increases, so the heat exchange efficiency increases.

 [0034] As described above, according to the heat exchanger of the present invention, high heat exchange efficiency can be achieved, and therefore, it is easy to reduce the size as compared with a heat exchanger having comparable performance.

 [0035] In this embodiment, the partition plates 25 are arranged at equal intervals in the width direction WL, but the arrangement at equal intervals is not essential. For example, the arrangement interval of the partition plates 25 in the box body 14 can be adjusted so that the channel width on the downstream side is wider than the channel on the upstream side in the width direction WL. When water containing a large amount of metal ions such as calcium ions is heated, scale is likely to deposit from around 60 ° C. If the flow path close to the water outlet 16 is designed to have a slightly wide opening, the increase in pressure loss due to scale deposition can be suppressed.

[0036] In the present embodiment, an example in which two refrigerant pipes are used has been described. However, a piping unit in which three or more refrigerant pipes are arranged in layers can be employed. For example, when using three refrigerant pipes, the meandering phase of the first layer pipe and the meandering phase of the second layer pipe are shifted by 180 degrees as in this embodiment, and the third layer pipe It is possible to adopt an arrangement pattern (ABA type) that matches the phase of the meandering to the meandering phase of the first layer pipe. Or, as an arrangement pattern (ABC type) in which the phase of the meander of the first layer pipe, the phase of the meander of the second layer pipe, and the phase of the meander of the third layer pipe are shifted by 120 degrees, The significant effects described in this specification can be obtained.

 Industrial applicability

 [0037] The heat exchanger according to the present invention has excellent heat exchange performance, and is useful as a heat exchanger for a heat pump water heater using a refrigerant. It can also be applied to heat exchangers that exchange heat between gases or liquids.

Claims

The scope of the claims  [1] A box body in which a first flow path having a rectangular outer shape appearing in a cross section perpendicular to the flow direction of the first fluid is formed,  A pipe unit that is arranged in the first flow path and that forms a second flow path through which a second fluid to be heat-exchanged with the first fluid flows;  Of the two pairs of opposite sides that form the rectangular outer shape of the first flow path in the cross section, when the direction parallel to the predetermined one pair of opposite sides is defined as the width direction of the first flow path,  The piping unit is  In the first reference plane, which is a plane parallel to both the width direction and the flow direction of the first fluid, the shape is adjusted so that the center of the tube draws a serpentine first locus. A pipe and a second pipe whose shape is adjusted so that the center of the pipe draws a meandering second locus in the plane of the second reference plane which is a plane parallel to the first reference plane,  When the first pipe and the second pipe are observed from a direction orthogonal to the first reference plane, the positional relationship between the first pipe and the second pipe is determined so as to intersect at a plurality of locations along the flow direction of the first fluid. ,Heat exchanger. [2] The heat exchanger according to claim 1, wherein the intersecting positions of the first pipe and the second pipe appear at equal intervals along the flow direction of the first fluid. [3] The positional relationship between the first pipe and the second pipe so that the meandering phase of the first locus and the meandering phase of the second locus are shifted by a half cycle in the flow direction of the first fluid. The heat exchanger according to claim 2, wherein [4] The first pipe and the second pipe are transferred to and from the box body by contacting the inner wall surfaces of the box body in the width direction directly or indirectly through another heat transfer section. 2. A heat exchanger according to claim 1, having a meandering amplitude that allows heating. [5] The further heat transfer section further includes a brazed joint that joins the inner wall surface of the box and the first pipe, and the inner wall face of the box and the second pipe. 4. The heat exchanger according to 4. [6] The diameter of the first pipe is equal to the diameter of the second pipe The heat exchange according to claim 1, wherein a positional relationship between the first pipe and the second pipe is determined so that a parallel distance between the first reference plane and the second reference plane is equal to the diameter. A piping unit consists of two pipes, the first pipe and the second pipe, and the box has a rectangular parallelepiped inner space, and the height of the first flow path constituted by the inner space is , Adjusted to a dimension equal to the sum of the diameter of the first pipe and the diameter of the second pipe,  The said 1st piping and said 2nd piping are contacting the inner wall surface of the said box directly or indirectly through another heat-transfer part by the up-down and left-right in the said 1st flow path. Heat exchanger.  The said other heat-transfer part was further equipped with the brazing junction part which joins the inner wall surface of the said box, said 1st piping, and the inner wall surface of the said box, and said 2nd piping. Heat exchanger.  The internal space of the box has a rectangular parallelepiped shape, and the first flow paths whose directions of flow of the first fluid are opposite to each other by 180 degrees are arranged alternately in the width direction or the direction perpendicular to the width direction. 2. The heat exchanger according to claim 1, further comprising a plurality of partition plates that partially partition the internal space so as to be formed.  2. The heat exchanger according to claim 1, wherein the heat exchanger is configured for a heat pump type hot water heater in which the first fluid is water and the second fluid is a refrigerant.