Heat exchanger

Abstract

A first heat exchanger (1) is provided with a heat exchanger body (11) that forms a first heat medium flow path (10) through which a heat medium (M) flows. The second heat exchanger (2) is also provided with a heat exchanger body (21) that forms a second heat medium flow path (20) through which the heat medium (M) flows. The heat exchanger bodies (11, 21) are buried underground. The heat exchanger main body (11) is formed from an extruded product of an aluminum alloy. The heat exchanger main body (21) is composed of sheet metal parts made of aluminum alloy.

Description

Technical Field

[0001] The present disclosure relates to heat exchangers. Background Art

[0002] Patent Document 1 discloses a geothermal heat utilization system including a U-shaped tube buried underground as a heat exchange device. Geothermal heat is collected while a fluid flows through the U-shaped tube.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-163554.

[0004] U-tubes are made of synthetic resins such as polyethylene. There is room for improvement in heat exchange performance. Summary of the Invention

[0005] The present disclosure aims to improve the heat exchange performance of a heat exchanger buried underground.

[0006] One aspect of the present disclosure provides a heat exchanger including a heat exchanger body buried underground to form a heat medium flow path through which heat medium flows, wherein the heat exchanger body is formed of an aluminum alloy extrusion or sheet metal.

[0007] According to the above configuration, the heat exchanger body is made of an aluminum alloy having excellent thermal conductivity. This facilitates heat exchange between the heat medium and the ground heat, thereby improving the heat exchange performance of the heat exchanger, compared to a heat exchanger made of synthetic resin.

[0008] The heat exchanger body is formed by the extruded member, and the heat medium flow path is formed by the hollow portion of the extruded member.

[0009] According to the above scheme, the extruded part can be easily lengthened, so the long heat exchanger can be easily manufactured. When manufacturing the heat exchanger body, fewer joints are required, which can reduce the man-hours required to manufacture the heat exchanger and bury it underground, and can reduce the burden of construction management.

[0010] Alternatively, the heat exchanger body may be composed of a plurality of sheet metal parts including a first sheet metal part and a second sheet metal part, the first sheet metal part having a recessed portion, the second sheet metal part overlapping with and joined to the first sheet metal part in a manner covering the recessed portion, and the heat medium flow path being composed of a hollow portion formed by the second sheet metal part covering the recessed portion.

[0011] According to the above configuration, a heat exchanger with excellent heat exchange performance can be provided simply by overlapping two sheet metal parts. Sheet metal parts can also be easily lengthened, so a long heat exchanger can be easily manufactured.

[0012] The device may further include a first head for closing an opening on one end side of the hollow portion and a second head for closing an opening on the other end side of the hollow portion.

[0013] According to the above aspect, a sealed heat medium flow path can be formed simply by attaching two headers to both ends of the heat exchanger body.

[0014] The heat medium may further include an inlet for allowing the heat medium to flow into the heat medium flow path and an outlet for allowing the heat medium to flow out of the heat medium flow path, wherein the inlet is provided at one of the first head and the second head, and the outlet is provided at one of the first head and the second head.

[0015] According to the above aspect, a structure for supplying and exhausting the heat medium to the sealed heat medium flow path can be added to the heat exchanger body simply by attaching two headers to both ends of the heat exchanger body.

[0016] The heat exchanger body may be formed with a flow path that is independent of the heat medium flow path and allows a fluid other than the heat medium to flow.

[0017] According to the above scheme, multiple fluids can be circulated underground. For example, when the heat exchanger is buried in a culture medium for growing plants, a heat medium can be used to regulate the temperature of the culture medium while a gas such as carbon dioxide that helps the growth of the plants can be circulated.

[0018] The heat exchanger main body may be buried under the ground or in a cultivation medium for growing plants.

[0019] According to the above scheme, stable ground heat can be utilized to easily manage the temperature of the heat medium. Alternatively, the temperature of the culture medium can be adjusted to promote or assist the growth of plants.

[0020] The heat exchanger may further include a corrosion prevention structure for preventing corrosion of the heat exchanger body.

[0021] According to the above configuration, even if the heat exchanger body is made of aluminum alloy, and even if there is electrolyte in the ground, corrosion of the heat exchanger body can be prevented, thereby improving the service life of the heat exchanger.

[0022] Alternatively, the corrosion prevention structure may include a base metal member and a cable, wherein the base metal member is buried underground together with the heat exchanger body and is made of a metal material having a lower potential than the aluminum alloy, and the cable electrically connects the heat exchanger body and the base metal member.

[0023] According to the above configuration, even if there is electrolyte underground, electrochemical corrosion occurs at the base metal parts, and corrosion of the heat exchanger main body can be suppressed.

[0024] The corrosion prevention structure may include a resin film covering the outer surface of the heat exchanger main body, and the corrosion prevention structure may include an anodized aluminum film or a glass layer provided on the outer surface of the heat exchanger main body.

[0025] According to the above scheme, even if there is electrolyte in the ground, the heat exchanger body is protected by the resin film, which can prevent the corrosion of the heat exchanger body. When the heat exchanger is buried in a culture medium where plants are grown, it is believed that the diffusion of metal into the culture medium is not preferable for the plants. Even in such a situation, the corrosion of the heat exchanger body can be prevented. The resin film has a lower thermal conductivity than the aluminum alloy used as the base material, so the film thickness needs to be set to the minimum limit that can prevent corrosion, and a film thickness of several μm to tens of μm is desired. In addition to resin, the film used as a means of preventing corrosion can be made of an electrically insulating material. Anodized aluminum treatment or inorganic coating treatment such as glass can also be applied as a corrosion prevention measure.

[0026] The heat exchanger may further include a head made of a resin material and provided at an end portion of the heat exchanger body.

[0027] According to the above configuration, even if there is electrolyte in the ground, corrosion does not occur in the resin head, thereby improving the durability of the heat exchanger.

[0028] Effects of the Invention According to the present disclosure, the heat exchange performance of a heat exchanger buried underground can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a conceptual diagram showing a heat exchange system to which the heat exchanger according to the embodiment is applied.

[0030] Figure 2 It is a perspective view of the first heat exchanger.

[0031] Figure 3 It is an exploded perspective view of the first heat exchanger.

[0032] Figure 4 is a cross-sectional view of the first heat exchanger.

[0033] Figure 5 yes Figure 4 VV cross-sectional view of.

[0034] Figure 6A This is a diagram showing an example of installing a heat exchanger below the ground.

[0035] Figure 6B yes Figure 6A BB cross-sectional view.

[0036] Figure 7AThis is a diagram showing another example of installing the heat exchanger below the ground.

[0037] Figure 7B yes Figure 7A BB cross-sectional view.

[0038] Figure 8 is a perspective view of the second heat exchanger.

[0039] Figure 9 It is an exploded perspective view of the second heat exchanger.

[0040] Figure 10 is a cross-sectional view of the second heat exchanger.

[0041] Figure 11 yes Figure 10 XI-XI sectional view.

[0042] Figure 12 This is a flowchart showing a method for manufacturing the second heat exchanger.

[0043] Figure 13 This is a conceptual diagram of a second heat exchanger manufacturing apparatus.

[0044] Figure 14 It is a cross-sectional view of a second heat exchanger of a modified example. DETAILED DESCRIPTION

[0045] Hereinafter, the embodiment will be described with reference to the accompanying drawings. In all the drawings, the same or corresponding elements are denoted by the same reference numerals, and repeated detailed descriptions are omitted.

[0046] (Heat exchange system) Figure 1 A heat exchange system 100 is shown that applies the heat exchangers (first heat exchanger 1 and second heat exchanger 2) of the embodiment. For example, the heat exchange system 100 adjusts the temperature of the plant 90 and the culture medium 91 in which the plant 90 is planted, thereby assisting the growth and reproduction of the plant 90. The plant 90 is preferably a crop. The culture medium 91 is a growth and reproduction medium for the plant 90 and is a candidate for the burial destination of the heat exchanger. The culture medium 91 is soil formed with long edges and has a trapezoidal or hilly cross-section. A plurality of plants 90 are arranged in the extension direction of the culture medium 91 ( Figure 1 The cells are arranged on the culture medium 91 at desired intervals in a direction perpendicular to the paper surface. The number of rows of the culture medium 91 is not particularly limited.

[0047] For ease of illustration, the culture medium 91 is positioned above the ground G. The ground G is the surface of the earth, and the lower portion thereof is a candidate for a buried location for the heat exchanger. The culture medium 91 may be placed on a frame (not shown) supported by the ground G, or may be placed on the ground G. Figure 1, the case where the plants 90 are cultivated in the agricultural house 92 is illustrated, but they can also be cultivated outdoors.

[0048] The heat exchange system 100 includes a first heat exchanger 1 , a second heat exchanger 2 , a heat storage tank 3 , a first supply line 5A, a second supply line 5B, a first discharge line 6A, and a second discharge line 6B.

[0049] The first heat exchanger 1 and the second heat exchanger 2 are both buried underground. "Underground" includes the area below the ground G and the area in the culture medium 91 (especially the soil). The first heat exchanger 1 and the second heat exchanger 2 are both formed into long, wide, and low plates.

[0050] The first heat exchanger 1 is buried under the ground G. The installation depth is not particularly limited. If the depth exceeds 15m, the underground temperature is not affected by the season or weather and is stable, which helps to stabilize the operation of the heat exchange system 100. Underground, the long side direction of the first heat exchanger 1 can be oriented in the vertical direction (refer to Figure 1 and Figure 7A ), or in the horizontal direction (see Figure 6A ).

[0051] The second heat exchanger 2 is embedded in the culture medium 91. The plurality of second heat exchangers 2 correspond one-to-one to the plurality of rows of culture medium 91. The longitudinal direction of each second heat exchanger 2 faces the extending direction of the corresponding culture medium 91.

[0052] The first heat exchanger 1 and the second heat exchanger 2 respectively have a first heat medium flow path 10 and a second heat medium flow path 20 through which a heat medium M flows. The heat medium M is a liquid or gaseous fluid. For example, water and antifreeze are suitable as the heat medium M.

[0053] The thermal storage tank 3 stores heat medium M. The thermal storage tank 3 has a thermal insulation structure, enabling the temperature of the heat medium M within the thermal storage tank 3 to be controlled at the required temperature, regardless of the outside temperature. The thermal storage tank 3 is connected to the upstream end of the first heat medium flow path 10 via a first supply line 5A and to the downstream end of the first heat medium flow path 10 via a first discharge line 6A. The thermal storage tank 3 is connected to the upstream end of the second heat medium flow path 20 via a second supply line 5B and to the downstream end of the second heat medium flow path 20 via a second discharge line 6B. Furthermore, the heat exchange system 100 is provided with a pressure delivery mechanism (not shown) for supplying the heat medium M.

[0054] The heat medium M in the thermal storage tank 3 is supplied to the second heat exchanger 2 via the second supply line 5B. While flowing through the second heat medium flow path 20, the heat medium M exchanges heat with the culture medium 91 by solid heat transfer through the component forming the second heat medium flow path 20 (heat exchanger body 21). After exchanging heat with the culture medium 91, the heat medium M returns to the thermal storage tank 3 via the second discharge line 6B.

[0055] The heat medium M within the thermal storage tank 3 is supplied to the first heat exchanger 1 via the first supply line 5A. While flowing through the first heat medium flow path 10, the heat medium M exchanges heat with the ground through solid heat transfer via the components forming the first heat medium flow path 10 (heat exchanger body 11). As described above, the ground heat is stable, so even if the temperature of the heat medium M changes due to heat exchange with the culture medium 91, the temperature of the heat medium M can be adjusted to be equal to the underground temperature. After heat exchange with the ground heat, the heat medium M returns to the thermal storage tank 3 via the first discharge line 6A.

[0056] The heat medium M, which has a stable temperature due to heat exchange with the ground heat, is supplied to the culture medium 91. In summer, cold water at a lower temperature than the outside air temperature can be supplied to the culture medium 91, while in winter, warm water at a higher temperature than the outside air temperature can be supplied to the culture medium 91. The temperature of the culture medium 91, i.e., the ambient temperature of the roots of the plant 90, can be stabilized regardless of the season, thereby promoting the growth and reproduction of the plant 90.

[0057] The downstream portion of the second supply line 5B branches to supply the heat medium M to each of the plurality of second heat exchangers 2. The upstream portion of the second supply line 5B branches to discharge the heat medium M from each of the plurality of second heat exchangers 2.

[0058] (First Heat Exchanger) Next, refer to Figures 2 to 5 Next, the first heat exchanger 1 will be described. The first heat exchanger 1 includes a heat exchanger body 11 , a first header 12 , a second header 13 , an inlet 14 , and an outlet 15 .

[0059] The heat exchanger body 11 is made of an extruded aluminum alloy. As an aluminum alloy, for example, 1000 series with excellent thermal conductivity, 2000 series with excellent strength, or 6000 series with excellent thermal conductivity and strength are suitable. Figure 8 ) is also made of the same material.

[0060] The heat exchanger body 11 comprises a first main wall 11a, a second main wall 11b, a pair of side walls 11c, multiple partition walls 11d, and multiple hollow portions 11e. The first main wall 11a, the second main wall 11b, and the pair of side walls 11c form a long, wide, and low rectangular tube, with both ends of the longitudinal direction open. This longitudinal direction corresponds to the extrusion direction.

[0061] In other words, the first main wall 11a is a rectangular flat plate. A pair of side walls 11c rise from either side of the first main wall 11a. The second main wall 11b is a flat plate of the same shape as the first main wall 11a. It is arranged parallel to the first main wall 11a, completely overlapping it when viewed in the thickness direction, and connecting the ends of the pair of side walls 11c. The four walls 11a-11c define a rectangular opening at each end along the longitudinal direction.

[0062] Multiple partition walls 11d extend parallel to the side walls 11c between the pair of side walls 11c, connecting the inner surfaces of the first main wall 11a and the second main wall 11b. The partition walls 11d divide the space surrounded by the four walls 11a to 11c into multiple hollow portions 11e arranged in the width direction. In the illustrated example, there are six partition walls 11d and seven hollow portions 11e, which is one more than the number, but the number of hollow portions 11e can be appropriately changed. Each hollow portion 11e has a rectangular cross-section. By using extrusion molding, a structure having multiple closed cross-sections or multiple hollow portions 11e can be easily manufactured. The first heat medium flow path 10 is composed of the hollow portion 11e.

[0063] The first head 12 closes the opening at one end of the hollow portion 11e. The second head 13 closes the opening at the other end of the hollow portion 11e. There are multiple hollow portions 11e, and both the first head 12 and the second head 13 close the openings of multiple hollow portions 11e simultaneously.

[0064] The first head 12 includes a cover plate 12a, a peripheral wall 12b rising from the periphery of the cover plate 12a, and an interior space 12c enclosed by the cover plate 12a and the peripheral wall 12b. The interior space 12c is open on the side opposite the cover plate 12a. The cross-section of the interior space 12c (the cross-section of the inner circumference of the peripheral wall 12b) has the same shape as the cross-section of the outer circumference of the heat exchanger body 11 (a rectangular shape in this embodiment). The first head 12 is externally fitted to one end of the heat exchanger body 11 and is fluid-tightly joined thereto. When assembled to the heat exchanger body 11, the inner surface of the cover plate 12a is in surface contact with the rectangular window-frame-shaped end surface at one end of the heat exchanger body 11. All of the partition walls 11d have their longitudinal ends offset inward of the heat exchanger body 11 relative to the end surface of the heat exchanger body 11 that is in surface contact with the cover plate 12a. Consequently, all of the hollow portions 11e are open at one end into the interior of the heat exchanger body 11. The hollow portions 11 e communicate with each other via a communication portion 11 f extending in the width direction within the heat exchanger body 11 between the opening of the heat exchanger body 11 and the hollow portion 11 e.

[0065] The second head 13 has a cover plate 13a, a peripheral wall 13b, and an internal space 13c, similarly to the first head 12, and is attached to the other longitudinal end of the heat exchanger body 11.

[0066] The inlet 14 and the first supply line 5A (see Figure 1 ) is connected to allow the heat medium M to flow into the first heat medium flow path 10. The outlet 15 is connected to the first discharge line 6A (see Figure 1 ) is connected to allow the heat medium M to flow out of the first heat medium flow path 10. The inlet 14 and outlet 15 are cylindrical or pipe joint-shaped. Although not shown in detail, the pipes constituting the first supply line 5A and the first discharge line 6A are respectively assembled to the inlet 14 and outlet 15.

[0067] The inlet 14 and outlet 15 are provided in the first head 12 or the second head 13. In this embodiment, a single inlet 14 is provided in the cover plate 12a of the first head 12, and a single outlet 15 is provided in the cover plate 13a of the second head 13. The correspondence between the inlet 14 and outlet 15 and the first head 12 and the second head 13 may be reversed, or both the inlet 14 and outlet 15 may be provided in the first head 12 or the second head 13. Multiple inlets 14 and multiple outlets 15 may also be provided.

[0068] The heat medium M flows into the communication portion 11f at one end through the inlet 14 and then branches out from the communication portion 11f at one end to each of the plurality of hollow portions 11e. The heat medium M flows from the plurality of hollow portions 11e to merge at the communication portion 11f at the other end and then flows out of the communication portion 11f at the other end through the outlet 15.

[0069] Thus, the first heat medium flow path 10 is composed of a connecting portion 11f at one end, multiple hollow portions 11e, and a connecting portion 11f at the other end. The multiple hollow portions 11e form multiple flow paths along the longitudinal direction within the first heat exchanger 1 (or heat exchanger body 11). In this embodiment, all of the hollow portions 11e constitute the first heat medium flow path 10.

[0070] The first heat exchanger 1, constructed as described above, includes a heat exchanger body 11 buried underground, forming a first heat medium flow path 10 through which the heat medium M flows. The heat exchanger body 11 is constructed from an extruded aluminum alloy. Aluminum alloy has higher thermal conductivity than synthetic resins such as polyethylene. Compared to heat exchangers made of synthetic resins, this facilitates heat exchange between the heat medium M and the ground heat, resulting in higher heat exchange performance.

[0071] The extruded material has a hollow portion 11e, and the first heat medium flow path 10 is formed by the hollow portion 11e. Extrusion molding allows for simple production of the long first heat exchanger 1. With fewer joints, the manufacturing process for the first heat exchanger 1 is reduced, simplifying construction management.

[0072] The first heat exchanger 1 further includes a first head 12 that closes the opening at one end of the hollow portion 11e, a second head 13 that closes the opening at the other end of the hollow portion 11e, an inlet 14 for allowing the heat medium M to flow into the first heat medium flow path 10, and an outlet 15 for allowing the heat medium M to flow out of the first heat medium flow path 10. The inlet 14 is provided at one of the first head 12 and the second head 13, and the outlet 15 is provided at one of the first head 12 and the second head 13. The heat exchanger body 11 is constructed from an extruded member having a hollow portion 11e open at both ends. Simply by attaching the first head 12 and the second head 13 to the ends of the heat exchanger body 11, a sealed first heat medium flow path 10 is formed, and the heat exchanger body 11 is provided with a structure for supplying and discharging the heat medium M to and from the first heat medium flow path 10.

[0073] There may be electrolytes in the ground below the ground G. If the first heat exchanger 1 is made of metal such as aluminum alloy, it is considered that the corrosion will proceed faster. Figure 1 As shown, a corrosion prevention structure 40 is provided to prevent corrosion of the heat exchanger body 11. The corrosion prevention structure 40 includes a base metal member 41 and a cable 42.

[0074] The base metal member 41 is made of a metal material with a lower natural potential than the aluminum alloy used as the heat exchanger body 11 (i.e., a material with a low electrode potential). Examples of such metal materials include zinc and magnesium. Zinc is relatively inexpensive and is particularly suitable. As an example, the base metal member 41 is rod-shaped, but other shapes such as plates are also possible. The base metal member 41 is adjacent to the heat exchanger body 11 and buried underground.

[0075] The cable 42 electrically and mechanically connects the base metal member 41 to the heat exchanger body 11. The cable 42 is made of a conductive material such as copper. The cable 42 may be covered with an insulating material.

[0076] The provision of corrosion prevention structure 40 prevents corrosion of heat exchanger body 11, even when the heat exchanger body 11 is made of an aluminum alloy and even when the ground contains electrolytes. Specifically, since heat exchanger body 11 has a higher electrode potential than base metal member 41, electrochemical corrosion of base metal member 41 is promoted, suppressing corrosion of heat exchanger body 11. This improves the service life of heat exchanger body 11.

[0077] The first head 12 and the second head 13 are made of the same metal as the heat exchanger body 11, for example, aluminum alloy, and are welded to the heat exchanger body 11. The corrosion preventing structure 40 also suppresses corrosion of the first head 12 and the second head 13.

[0078] The first and second heads 12, 13 can also be made of resin. In this case, even if there are electrolytes in the ground, the first and second heads 12, 13 will not corrode. Compared to the heat exchanger body 11, the first and second heads 12, 13 are small components, so even if they are made of resin, the heat exchange performance of the first heat exchanger 1 is not affected. Furthermore, the head of the second heat exchanger 2, described later, can also be made of resin, thereby achieving the same effect.

[0079] Figure 6A and Figure 6B This figure shows an example of installing the first heat exchanger 1 below the ground G. In this example, a single first heat exchanger 1 is buried underground. The longitudinal direction of the first heat exchanger 1 is horizontal. A base metal member 41 is installed above the first heat exchanger 1. The base metal member 41 is in the shape of a rod or an elongated plate and has the same length (longitudinal dimension) as the first heat exchanger 1.

[0080] Figure 7A and Figure 7BAnother example of a method of installing the first heat exchanger 1 below the ground G is shown. In this example, multiple first heat exchangers 1 are buried underground. The long side direction of each first heat exchanger 1 is oriented in the vertical direction. A base metal part 41 is arranged between two adjacent first heat exchangers 1, and each of the two first heat exchangers 1 is connected to the base metal part 41 via a corresponding cable 42. In the illustrated example, three first heat exchangers 1 and two base metal parts 41 are arranged alternately, but the number is not specifically limited. In this example, the base metal part 41 is in the shape of a rod or a long plate and has the same length (dimension in the long side direction) as the first heat exchanger 1.

[0081] In either of the above two examples, the service life of the heat exchanger having excellent heat exchange performance can be improved. Figure 1 ) can also be connected in parallel with multiple first heat exchangers 1. Multiple first heat exchangers 1 can also be connected in series. When connected in series, the outlet 15 of a first heat exchanger 1 (see Figure 1 ) and the inlet 14 of the other first heat exchanger 1 (refer to Figure 1 ) are connected, and the heat medium M flows sequentially inside the plurality of first heat exchangers 1 one by one.

[0082] (Second heat exchanger) Next, refer to Figures 8 to 11 Next, the second heat exchanger 2 will be described. The second heat exchanger 2 includes a heat exchanger body 21 , a first header 22 , a second header 23 , an inlet 24 , and an outlet 25 .

[0083] The heat exchanger body 21 is made of aluminum alloy sheet metal. More specifically, the heat exchanger body 21 is made of a plurality of sheet metal members, including a first sheet metal member 31 and a second sheet metal member 32. The first sheet metal member 31 and the second sheet metal member 32 are rectangular in plan view. The second sheet metal member 32 is flat.

[0084] The first sheet metal part 31 has a plurality of recesses 31a. The number of recesses 31a is not particularly limited. Each recess 31a is the inner space of a convex portion formed by protruding a portion of the first sheet metal part 31 toward the side opposite to the second sheet metal part 32, and is open toward the second sheet metal part 32. Each recess 31a is in the shape of a groove extending along the longitudinal direction of the first sheet metal part 31 and is also open at both edges in the longitudinal direction of the first sheet metal part 31. The cross-sectional shape of the recess 31a or the convex portion is not particularly limited. The plurality of recesses 31a extend parallel to each other and are arranged at intervals in the width direction.

[0085] The second sheet metal part 32 overlaps with the first sheet metal part 31 and is joined to the first sheet metal part 31 in a manner that closes the recess 31a of the first sheet metal part 31. Thus, the heat exchanger main body 21 is formed. The joining means is not particularly limited. Heat fusion is simpler than welding and fixing, and it is easier to ensure airtightness, so it is more suitable. A heat fusion film can also be sandwiched between the joining surfaces of the first sheet metal part 31 and the second sheet metal part 32, and an adhesive film of a non-polar resin can also be formed on the joining surfaces of the first sheet metal part 31 and the second sheet metal part 32. The adhesive film is thinner than the heat fusion film, so it helps to reduce the thermal resistance of the heat exchanger main body 21 and helps to improve the heat exchange performance of the second heat exchanger 2.

[0086] The heat exchanger body 21 is provided with a hollow portion 21a formed by enclosing a recessed portion 31a with a second sheet metal member 32. Each hollow portion 21a has a closed cross-section and is open at both ends of the heat exchanger body 21. The plurality of hollow portions 21a are independent of one another. In this embodiment, all of the plurality of hollow portions 21a constitute the second heat medium flow path 20.

[0087] The first head 22 closes the opening at one end of the hollow portion 21a, and the second head 23 closes the opening at the other end of the hollow portion 21a. There are multiple hollow portions 21a, and the first head 22 and the second head 23 close the openings of the multiple hollow portions 21a together.

[0088] The first head 22 includes a cover plate 22a, a peripheral wall 22b extending from the periphery of the cover plate 22a, and an internal space 22c enclosed by the cover plate 22a and the peripheral wall 22b. The internal space 22c is open on the side opposite the cover plate 22a. The cross-section of the internal space 22c (the cross-section of the inner circumference of the peripheral wall 22b) has the same shape as the cross-section of the outer circumference of the heat exchanger body 21 (in this embodiment, a shape of a short rectangle with three ridges arranged horizontally). The first head 22 is externally fitted to one end of the heat exchanger body 21 and is fluid-tightly joined thereto. When mounted on the heat exchanger body 21, the inner surface of the cover plate 22a is in fluid-tight contact with the end surface of one end of the heat exchanger body 21. This seals the opening at one end of the hollow portion 21a.

[0089] The same applies to the other longitudinal end. The second head 23, like the first head 22, comprises a cover plate 23a, a peripheral wall 23b, and an internal space 23c. Like the first head 22, the second head 23 is mounted on the other longitudinal end of the heat exchanger body 21. The opening at the other end of the hollow portion 21a is sealed. This creates independent spaces within the second heat exchanger 2, with the multiple hollow portions 21a forming separate spaces.

[0090] The inlet 24 is connected to the second supply line 5B, allowing the heat medium M to flow into the second heat medium flow path 20. The outlet 25 is connected to the second discharge line 6B, allowing the heat medium M to flow out of the second heat medium flow path 20. The inlet 24 and outlet 25 are cylindrical or pipe joint-shaped. Although not shown in detail, the pipes constituting the second supply line 5B and the second discharge line 6B are attached to the inlet 24 and outlet 25, respectively.

[0091] The inlet 24 and the outlet 25 are provided in the first head 22 or the second head 23. In this embodiment, the three inlet 24 are provided in the cover plate 22a of the first head 22, and the three outlet 25 are provided in the cover plate 23a of the second head 23.

[0092] The central inlet of the three inlets 24 communicates with an opening at one end of the hollow portion 21a (second heat medium flow path 20) in the center in the width direction. The central outlet of the three outlets 25 communicates with an opening at the other end of the same hollow portion 21a (second heat medium flow path 20). One inlet of the three inlets 24 communicates with an opening at one end of the hollow portion 21a (second heat medium flow path 20) on one side in the width direction. One outlet of the three outlets 25 communicates with an opening at the other end of the same hollow portion 21a (second heat medium flow path 20). The other inlet of the three inlets 24 communicates with an opening at one end of the hollow portion 21a (second heat medium flow path 20) on the other side in the width direction. The other outlet of the three outlets 25 communicates with an opening at the other end of the same hollow portion 21a (second heat medium flow path 20).

[0093] The downstream end of the second supply line 5B branches near each second heat exchanger 2 and connects to three inlet ports 24. The upstream end of the second discharge line 6B branches near each second heat exchanger 2 and connects to three outlet ports 25. The heat medium M flows from the downstream portion of the second supply line 5B through the three inlet ports 24 into the three second heat medium flow paths 20. The heat medium M flows unidirectionally through each second heat medium flow path 20, from one side to the other in the longitudinal direction. The heat medium M flows from each second heat medium flow path 20 through the corresponding outlet port 25 to the downstream portion of the second discharge line 6B.

[0094] The second heat exchanger 2, constructed as described above, is buried underground and includes a heat exchanger body 21 forming a second heat medium flow path 20 through which the heat medium M flows. The heat exchanger body 21 is constructed from an aluminum alloy sheet metal. Compared to heat exchangers made of synthetic resin, this facilitates heat exchange between the heat medium M and the ground heat, achieving high heat exchange performance. This makes it easier to control the temperature of the culture medium 91 to the target, promoting the growth of the plants 90.

[0095] The heat exchanger body 21 is constructed from multiple sheet metal parts, including a first sheet metal part 31 and a second sheet metal part 32. The first sheet metal part 31 has a recessed portion 31a, and the second sheet metal part 32 is bonded to the first sheet metal part 31 to close the recessed portion 31a. The second heat medium flow path 20 is formed by the second sheet metal part 32 closing the recessed portion 31a. By overlapping sheet metal parts, the long second heat exchanger 2 can be easily manufactured. The heat exchanger body 21 can also be constructed from three or more sheet metal parts.

[0096] The second heat exchanger 2 and the first heat exchanger 1 (see Figure 2 ) is similarly provided with a first head 22 that closes the opening on one end side of the hollow portion 21a, a second head 23 that closes the opening on the other end side of the hollow portion 21a, an inlet 24 for allowing the heat medium M to flow into the second heat medium flow path 20, and an outlet 25 for allowing the heat medium M to flow out of the second heat medium flow path 20. The inlet 24 is provided on either the first head 22 or the second head 23, and the outlet 25 is provided on either the first head 22 or the second head 23. The same functions and effects as those of the first heat exchanger 1 are achieved.

[0097] The culture medium 91 contains a large amount of electrolyte to promote the growth of the plant 90. If the second heat exchanger 2 is made of a metal such as an aluminum alloy, it is considered that corrosion will proceed rapidly.

[0098] The second heat exchanger 2 may also be provided with a corrosion prevention structure 40 having a base metal part 41 and a cable 42. In this case, the metal ions of the base metal part 41 that is corroding diffuse into the culture medium 91. There are cases where the plant 90 requires zinc for growth. Therefore, the growth of the plant 90 can sometimes be assisted by the diffusion of the base metal into the culture medium 91. In this case, the first head 22 and the second head 23 can be made of an aluminum alloy, which not only suppresses the corrosion of the heat exchanger body 21 but also suppresses the corrosion of the first head 22 and the second head 23. On the other hand, it is also believed that the heavy metals contained in the aluminum alloy constituting the heat exchanger body 21 diffuse into the culture medium 91. The heavy metals may hinder the healthy growth of the plant 90.

[0099] Therefore, the second heat exchanger 2 embedded in the culture medium 91 may also be provided with a resin coating 46 as an example of the corrosion prevention structure 40. When heat-sealing the resin coating is used to join the first sheet metal 31 and the second sheet metal 32, the coating 46 can be formed simultaneously with the formation of the bonding coating on the surface of the heat exchanger body (the surface of each of the first sheet metal 31 and the second sheet metal 32 opposite the joining surface). Since the coating 46 serving as the corrosion prevention structure 40 is formed during the manufacturing process of the second heat exchanger 2, the second heat exchanger 2 with corrosion protection measures can be manufactured simply.

[0100] If the heat exchanger body 21 is covered with a resin coating 46, the heat exchanger body 21 will not corrode even in an environment prone to metal corrosion, such as the culture medium 91, thereby preventing the diffusion of heavy metals. In this case, the first head 22 and the second head 23 can be made of resin, in which case there is no need to form a resin coating on the first head 22 and the second head 23.

[0101] The following includes the steps of forming the corrosion-preventing film 46 (and the bonding film), referring to Figure 12 and Figure 13 A method for manufacturing the second heat exchanger 2 will be described.

[0102] Figure 12 A flowchart showing a method for manufacturing the second heat exchanger 2. First, an aluminum alloy plate 30 (see Figure 13 ) are formed on both sides of the film 46 (step S1). Then, the concave portion 31a is formed on the plate 30 by roll forming (step S2). Then, the first plate 30a (refer to Figure 13 ), the second sheet material 30b which is not subjected to roll forming after the film is formed (refer to Figure 13 ) are joined by heat welding (step S3). Next, the joined body is cut into the desired size to form the heat exchanger body 21 (step S4). Next, resin seals 47 are placed on both edges of the heat exchanger body 21 in the width direction (step S5). Next, the first head 22 and the second head 23 are bonded to the heat exchanger body 21 (step S6). Thus, the second heat exchanger 2 is completed.

[0103] Figure 13 The manufacturing device 50 of the second heat exchanger 2 is shown. The manufacturing device 50 includes a film forming device 60 that performs the film forming process (step S1). The film forming device 60 includes an uncoiler 61, a chemical conversion treatment unit 62, a roller coater 63, a drying furnace 64, a rewinder 65, and a supply roller 66. The uncoiler 61 unwinds a coil formed from the sheet material 30 before the film is formed. The rewinder 65 rewinds the sheet material 30 after the film is formed to form a new coil. The supply roller 66 forms a supply path for the sheet material 30 and feeds the sheet material 30 along the supply path from the uncoiler 61 to the rewinder 65.

[0104] The chemical conversion treatment section 62 applies a chemical conversion treatment to the sheet material 30 supplied from the uncoiler 61. Both surfaces of the sheet material 30 serve as the treated surfaces. In the chemical conversion treatment section 62, the treated surfaces are cleaned and then subjected to the chemical conversion treatment. The chemical conversion treatment can be either a chemical conversion or a coating type, and can be either a chromate coating or a non-chromate coating method. Examples of chromate coating treatments include chromate plating and phosphoric acid plating.

[0105] The roller coater 63 includes a tank 63a for storing the adhesive and a transfer roller 63b for applying the adhesive in the tank 63a to the treated surface of the plate 30 after the chemical conversion treatment. The adhesive is composed of a non-polar resin with thermal adhesive properties. Examples of the non-polar resin include polypropylene, polyethylene, or polyolefins blended therefrom. In particular, acid-modified polyolefins are suitable examples of non-polar resins for the adhesive.

[0106] The drying oven 64 fixes the chemical conversion treatment layer 46a and the adhesive layer 46b to the adhesive-coated plate 30, thereby forming a coating 46 on the treated surface (in this example, both surfaces) of the plate 30. The coating 46 has a thickness of approximately several micrometers. Due to its low thermal resistance, the solid heat transfer performance of the heat exchanger main body 21 and the heat exchange performance of the second heat exchanger 2 are unlikely to deteriorate.

[0107] The manufacturing device 50 further includes a first uncoiler 51 , a second uncoiler 52 , a roll former 53 , a welding machine 54 , a cutter 55 , and a supply roll 56 .

[0108] The coil recovered by the rewinder 65 is mounted on the first uncoiler 51 and the second uncoiler 52. Both the first uncoiler 51 and the second uncoiler 52 unwind the coil formed from the sheet materials 30 (30a, 30b) after the film has been formed. The supply roller 56 forms a supply path for the sheet materials 30a, 30b. The supply path includes a first path 56a extending from the first uncoiler 51 through the roll former 53 to the welding machine 54; a second path 56b extending from the second uncoiler 52 to the welding machine 54; and a third path 56c extending from the welding machine 54 to the cutting machine 55.

[0109] The roller forming machine 53 performs the concave portion forming process (step S2). The roller forming machine 53 has a roller pair consisting of a roller 53a with a flange and a roller 53b with a groove. The first plate 30a sent out from the first uncoiler 51 passes between the roller pair. In this process, the concave shape is transferred to the first plate 30a by the cooperation of the flange and the groove. A plurality of groups of flanges and grooves are arranged along the axial direction of the roller pair, and a plurality of concave shapes are formed on the first plate 30a. Each concave shape extends along the extension direction of the first path 56a (the supply direction of the first plate 30a). This concave shape serves as the aforementioned concave portion 31a (refer to Figure 9 ) to perform its function.

[0110] The welding machine 54 performs the heat welding process (step S3). The welding machine 54 includes a pair of heated rollers. The first path 56a and the second path 56b both terminate at the gap between the roller pairs. The first sheet 30a fed from the roller forming machine 53 and the second sheet 30b fed from the second uncoiler 52 pass between the roller pairs. During this process, the film 46 on the joining surfaces of the first sheet 30a and the second sheet 30b are heated, bonding the first sheet 30a and the second sheet 30b. The concave shape of the first sheet 30a is sealed by the second sheet 30b.

[0111] The cutting machine 55 performs the cutting process (step S4). The cutting machine 55 cuts the joined sheet materials 30a and 30b fed from the welding machine 54 into the desired size. This forms the heat exchanger body 21. The first sheet material 30a corresponds to the first sheet metal component 31 of the heat exchanger body 21, and the second sheet material 30b corresponds to the second sheet metal component 32 of the heat exchanger body 21.

[0112] Reference Figure 10 , the entire surface of the first sheet metal 31 on the side opposite to the joining surface is covered by the film 46. The entire surface of the second sheet metal 32 on the side opposite to the joining surface is also covered by the film 46. In the sealing process (step S5), a film made of a resin such as polyolefin is adhered to the edge portions on both sides of the heat exchanger body 21 as a seal 47. With the help of the seal 47, the side edges where the film 46 is difficult to form are also covered with the resin material. With the help of the corrosion prevention structure 40 composed of the film 46 and the seal 47, the aluminum alloy as the material of the heat exchanger body 21 is not exposed to the culture medium 91, and the service life of the heat exchanger body 21 is improved.

[0113] The film 46 also remains on the inner surface of the hollow portion 21a, which does not contribute to heat welding. The surface defining the second heat medium flow path 20 is protected by the film 46. Even when a non-neutral fluid is used as the heat medium M, corrosion of the heat exchanger body 21 can be prevented, thereby extending the service life of the second heat exchanger 2.

[0114] (Variation) Although the embodiments have been described above, the above-described configurations can be appropriately changed, deleted, or added within the scope of the present disclosure.

[0115] Reference Figure 14For example, the heat exchanger body 21 may form a flow path for a fluid other than the heat medium M independently of the second heat medium flow path 20. Examples of the fluid other than the heat medium M include carbon dioxide. In this case, the heat exchange system 100 includes a CO2 tank 4 and a CO2 line 7. The CO2 tank 4 stores carbon dioxide and is connected to the second heat exchanger 2 via the CO2 line 7. The downstream portion of the CO2 line 7 may branch to supply carbon dioxide to each of the plurality of second heat exchangers 2.

[0116] Of the three hollow portions 21a of the heat exchanger body 21, the two hollow portions 21a on both sides in the width direction constitute the second heat medium flow path 20. The central hollow portion 21a in the width direction constitutes a CO2 flow path 29 through which carbon dioxide flows as a fluid other than the heat medium M. However, the arrangement of the flow paths is not particularly limited.

[0117] The first head 22 is connected to the CO2 line 7, and a gas inlet 26 for flowing carbon dioxide is provided in the CO2 flow path 29. The gas inlet 26 is also in the shape of a tube or a pipe joint, and the pipe constituting the CO2 line 7 is assembled on the gas inlet 26. A plurality of gas outlets 27 are provided in the heat exchanger body 21. The gas outlet 27 is a through hole formed in at least one of the first sheet metal and the second sheet metal 32 (in the illustrated example, only the first sheet metal 31 is used as an example) to connect the CO2 flow path 29 with the outside of the second heat exchanger 2. The plurality of gas outlets 27 may be arranged at intervals in the longitudinal direction, which is the direction in which the CO2 flow path 29 extends.

[0118] Carbon dioxide flows from the downstream portion of the CO2 line 7 through the gas inlet 26 into the CO2 flow path 29. Carbon dioxide is directed into the CO2 flow path 29, allowing it to flow from one longitudinal side to the other through the widthwise center of the heat exchanger body 21. The other end of the CO2 flow path 29 is sealed by the inner surface of the cover plate 23a of the second head 23. Carbon dioxide is released from the CO2 flow path 29 through the gas outlet 27 to the outside of the heat exchanger body 21, i.e., into the culture medium 91.

[0119] In the first heat exchanger 1, a single inlet 14 is provided in the first header 12, and a single outlet 15 is provided in the second header 13. However, multiple inlets may correspond to multiple first heat medium flow paths 10, and multiple outlets may correspond to multiple first heat medium flow paths 10. In the second heat exchanger 2, multiple inlets 24 are provided in the first header 22, and multiple outlets 25 are provided in the second header 23. However, the heat medium M flowing into the first header 22 through a single inlet may be branched into multiple second heat medium flow paths 20, or the heat medium M, after being combined in the second header 23, may flow out of the second header 23 through a single outlet.

[0120] In the above embodiment, for ease of explanation, the heat exchanger constructed from an extruded member and buried beneath the ground G is referred to as the "first heat exchanger 1," and the heat exchanger constructed from a sheet metal member and buried in the culture medium 91 is referred to as the "second heat exchanger 2." However, a heat exchanger constructed from an extruded member may be buried in the culture medium 91. A heat exchanger constructed from a sheet metal member may also be buried beneath the ground G.

[0121] Heat exchangers buried beneath the ground G may also have a resin coating on the outer surface of the heat exchanger body. In heat exchangers buried under the culture medium 91, base metal components electrically connected to the heat exchanger body may also be embedded in the culture medium 91. Both a coating and a base metal component may be used in a single heat exchanger as the corrosion prevention structure 40. The heat exchanger body may also be wrapped with a polyethylene bag instead of a resin coating.

[0122] The outer surface of the heat exchanger body may be covered with a film other than the resin film 46. In this case, the heat exchanger body is subjected to the required surface treatment. Similar to the resin film 46, the surface treatment is performed to improve corrosion resistance against water, including electrolytes such as salt in soil. The film formed by the surface treatment is expected to have the following properties: electrical insulation while minimizing the impairment of the heat exchanger's thermal conductivity.

[0123] For example, when the heat exchanger body is made of aluminum alloy, the outer surface of the heat exchanger body can also be covered with an anodic oxide film formed by anodizing aluminum. The treatment bath (electrolyte) can use sulfuric acid, oxalic acid, chromic acid or phosphoric acid. In addition, the outer surface of the heat exchanger body can also be covered with a film of thermal spray material sprayed by thermal spraying. Ceramics are a suitable example of thermal spray material. In addition, a glass layer can also be provided on the outer surface of the heat exchanger body. For example, liquid glass can also be applied to the surface of the aluminum alloy. Liquid glass includes liquid glass obtained by applying siloxane, silane, or polysilazane to the surface of the aluminum alloy constituting the heat exchanger to form a glassy amorphous silicon dioxide film. In addition, liquid glass can also be applied after the anodic oxide film is formed by anodizing aluminum. There are multiple pores in the anodic oxide film obtained by anodizing aluminum. In a subsequent process, liquid glass is applied so that the liquid glass invades the pores, thereby integrating the liquid glass and the anodic oxide film, which can suppress the decrease in thermal conductivity. By forming such a film, corrosion of the heat exchanger body can be prevented, similarly to the above-mentioned embodiment, and the durability of the heat exchanger can be improved.

[0124] A flow path for circulating a fluid other than the heat medium may also be provided in the heat exchanger buried under the ground G. The fluid is not limited to carbon dioxide, and may be other liquids or gases.

[0125] When the heat exchanger body includes multiple hollow portions, the heat medium flow path can be configured in any manner. When multiple hollow portions constitute independent heat medium flow paths, the heat medium flow direction in some of the hollow portions may be opposite to that in the remaining portions. Adjacent two of the multiple hollow portions may be connected to each other, thereby providing the heat medium flow path with one or more return portions.

[0126] Heat exchange systems using heat exchangers can also be used for purposes other than agriculture.

[0127] The present disclosure may include the following aspects.

[0128] (Method 1) A heat exchanger, A heat exchanger body is provided, wherein the heat exchanger body is buried underground and forms a heat medium flow path through which heat medium flows. The heat exchanger body is made of an aluminum alloy extrusion or sheet metal.

[0129] (Method 2) The heat exchanger as described in embodiment 1, The heat exchanger body is composed of the extruded part. The heat medium flow path is formed by the hollow portion of the extruded member.

[0130] (Method 3) The heat exchanger as described in embodiment 1, The heat exchanger body is composed of a plurality of sheet metal parts including a first sheet metal part and a second sheet metal part. The first sheet metal member has a recessed portion, and the second sheet metal member overlaps with and is joined to the first sheet metal member in a manner covering the recessed portion. The heat medium flow path is composed of a hollow portion formed by covering the recessed portion with the second sheet metal member.

[0131] (Method 4) The heat exchanger as described in method 2 or 3, The invention further includes a first head for closing an opening on one end side of the hollow portion, and a second head for closing an opening on the other end side of the hollow portion.

[0132] (Method 5) The heat exchanger as described in mode 4, further comprising an inlet for allowing the heat medium to flow into the heat medium flow path, and an outlet for allowing the heat medium to flow out of the heat medium flow path, The inlet is provided at one of the first head and the second head, and the outlet is provided at one of the first head and the second head.

[0133] (Method 6) The heat exchanger according to any one of modes 1 to 5, The heat exchanger body is formed with a flow path that is independent of the heat medium flow path and allows a fluid other than the heat medium to flow.

[0134] (Method 7) The heat exchanger according to any one of modes 1 to 6, The heat exchanger body is buried under the ground or in a cultivation medium for growing plants.

[0135] (Method 8) The heat exchanger according to any one of modes 1 to 7, The heat exchanger further includes a corrosion prevention structure for preventing corrosion of the heat exchanger body.

[0136] (Method 9) The heat exchanger as described in embodiment 8, The corrosion prevention structure includes a base metal member and a cable. The base metal member is buried underground together with the heat exchanger body and is made of a metal material with a lower potential than the aluminum alloy. The cable electrically connects the heat exchanger body and the base metal member.

[0137] (Method 10) The heat exchanger as described in embodiment 8, The corrosion prevention structure includes a resin film covering the outer surface of the heat exchanger body.

[0138] (Method 11) The heat exchanger as described in embodiment 8, The corrosion prevention structure includes an anodized aluminum coating or a glass layer provided on the outer surface of the heat exchanger body.

[0139] (Method 12) The heat exchanger according to any one of modes 8 to 12, The heat exchanger further includes a head made of a resin material and provided at an end portion of the heat exchanger body.

[0140] This application claims the benefit of priority based on Japanese Patent Application No. 2023-036693, filed on March 9, 2023, and Japanese Patent Application No. 2023-119928, filed on July 24, 2023. Both Japanese Patent Application No. 2023-036693 and Japanese Patent Application No. 2023-119928 are hereby incorporated by reference into this specification.

[0141] Description of Reference Numerals 1. First heat exchanger 2 Second heat exchanger 10 First heat medium flow path 11 Heat exchanger body 11e Hollow 12 First Head 13 Second Head 14 Inlet 15 outflow 20 Second heat medium flow path 21 Heat exchanger body 21a Hollow part 22 First Head 23 Second Head 24 Inlet 25 outflow 29 CO2 flow path 31 First Sheet Metal 31a recess 32 Second sheet metal part 40 Corrosion prevention structure 41 Base metal parts 42 cables 46 membrane 90 plants 91 culture medium 100 heat exchange system G Ground M heat medium.

Claims

1. A heat exchanger, characterized in that: A heat exchanger body is provided, wherein the heat exchanger body is buried underground and forms a heat medium flow path through which the heat medium flows. The heat exchanger body is made of an aluminum alloy extrusion or sheet metal.

2. The heat exchanger according to claim 1, wherein The heat exchanger body is composed of the extruded part. The heat medium flow path is formed by the hollow portion of the extruded member.

3. The heat exchanger according to claim 1, wherein The heat exchanger body is composed of a plurality of sheet metal parts including a first sheet metal part and a second sheet metal part. The first sheet metal member has a recessed portion, and the second sheet metal member overlaps with and is joined to the first sheet metal member in a manner covering the recessed portion. The heat medium flow path is composed of a hollow portion formed by covering the recessed portion with the second sheet metal member.

4. The heat exchanger according to claim 2 or 3, characterized in that The invention further includes a first head for closing an opening on one end side of the hollow portion, and a second head for closing an opening on the other end side of the hollow portion.

5. The heat exchanger according to claim 4, characterized in that further comprising an inlet for allowing the heat medium to flow into the heat medium flow path, and an outlet for allowing the heat medium to flow out of the heat medium flow path, The inlet is provided at one of the first head and the second head, and the outlet is provided at one of the first head and the second head.

6. The heat exchanger according to any one of claims 1 to 3, characterized in that The heat exchanger body is formed with a flow path that is independent of the heat medium flow path and allows a fluid other than the heat medium to flow.

7. The heat exchanger according to any one of claims 1 to 3, characterized in that The heat exchanger body is buried under the ground or in a cultivation medium for growing plants.

8. The heat exchanger according to any one of claims 1 to 3, characterized in that The heat exchanger further includes a corrosion prevention structure for preventing corrosion of the heat exchanger body.

9. The heat exchanger according to claim 8, wherein The corrosion prevention structure includes a base metal member and a cable. The base metal member is buried underground together with the heat exchanger body and is made of a metal material with a lower potential than the aluminum alloy. The cable electrically connects the heat exchanger body and the base metal member.

10. The heat exchanger according to claim 8, wherein The corrosion prevention structure includes a resin film covering the outer surface of the heat exchanger body.

11. The heat exchanger according to claim 8, wherein The corrosion prevention structure includes an anodized aluminum coating or a glass layer provided on the outer surface of the heat exchanger body.

12. The heat exchanger according to claim 8, wherein The heat exchanger further includes a head made of a resin material and provided at an end portion of the heat exchanger body.

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