US20110277494A1

US20110277494A1 - Heat exchanger and heat pump type hot water supply apparatus equipped with same

Info

Publication number: US20110277494A1
Application number: US13/145,741
Authority: US
Inventors: Tomonori Kikuno; Satoshi Inoue; Akihiro Fujiwara; Hyunyoung Kim; Yoshikazu Shiraishi; Kaori Yoshida; Takayuki Hyoudou
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2009-01-22
Filing date: 2010-01-20
Publication date: 2011-11-17
Also published as: WO2010084889A1; EP2390612A1; CN102292611A; JP2010249495A; JP4770989B2

Abstract

A heat exchanger 21 is provided with a metal tube 47 that has a support member 55 inhibiting deformation in the thickness direction in a fluid flow channel 53, and a multiple-hole metal tube 45 that is stacked on one side of the metal tube 47 in the thickness direction and has an opposing surface disposed opposite an outer surface 61 on the one side of the metal tube 47 and joined by at least part thereof to the outer surface 61 on the one side.

Description

TECHNICAL FIELD

The present invention relates to a heat exchanger and a heat pump type hot water supply apparatus equipped with same.

BACKGROUND ART

Seam welding, which is a type of resistance welding, excels in productivity because the zones that are to be joined can be joined continuously, and seam welding is used for various applications.
For example, as disclosed in Patent Documents 1 and 2, seam welding is used when rounding a steel sheet to form a metal tube. More specifically, a steel tube is manufactured by disposing electrodes in the vicinity of two end surfaces of a steel sheet that has been rounded in a tubular shape such that the end surfaces face each other and forming a continuous seam by passing an electric current to the steel sheet via the electrodes, while moving the electrodes relative to the end surfaces.
Further, seam welding is also used in manufacturing fuel tanks for vehicles. More specifically, flange portions provided on the circumference of two metal sheets having receding portions are overlapped and the flange portions are welded together to manufacture a fuel tank by passing an electric current, while clamping the flange portions between a pair of roller electrodes.
Patent Document 1: Japanese Patent Application Publication No. S 62-50088.
Patent Document 2: Japanese Patent Application Publication No. S 54-112370.
When a heat exchanger for use in an air conditioner, a heat pump type hot water supply apparatus, or the like is manufactured, it is necessary to join together a metal tube having inside thereof a coolant flow channel where a coolant flows and a metal tube having inside thereof a fluid flow channel where fluid such as water or coolant flows. When the aforementioned resistance welding is used for joining these metal tubes together, the following problems are encountered.
Thus, when metal tubes are joined together by resistance welding, it is necessary to weld a plurality of stacked metal tubes, while pressurizing the metal tubes in the stacking direction by a pair of roller electrodes. However, where hollow metal tubes are resistance welded, while being pressurized with a pair of roller electrodes, the metal tubes collapse and the hollow portions are almost entirely eliminated. Therefore, the metal tubes cannot function sufficiently as flow channels for coolants or fluids and the desired efficiency of heat exchange cannot be obtained. Where the pressurization in the stacking direction of the plurality of metal tubes is insufficient, the metal tubes cannot be sufficiently joined and the efficiency of heat exchange is therefore decreased.
Further, an elongated heat exchanger obtained by joining metal tubes is sometimes used in a compact form obtained by bending in order to save space. In such a case, the metal tubes sometimes collapse in the bending zone and the hollow portions are almost entirely eliminated. Where the hollow portions of metal tubes are eliminated, the metal tubes cannot function sufficiently as flow channels for coolants or fluids and the desired efficiency of heat exchange cannot be obtained.

SUMMARY OF THE INVENTION

The present invention has been created with the foregoing in view and it is an object of the present invention to provide a heat exchanger with excellent heat exchange efficiency and a heat pump type hot water supply apparatus equipped with such a heat exchanger.
The heat exchanger in accordance with the present invention includes a metal tube (47) that has a flat shape with a width greater than a thickness, a fluid flow channel (53) formed inside thereof along a longitudinal direction, respective outer surfaces (61, 63) formed on one side and the other side in a thickness direction, and a support portion (55) formed in the fluid flow channel (53) and inhibiting deformation in the thickness direction; and a multiple-hole metal tube (45) stacked on one side of the metal tube (47) in the thickness direction and having a flat shape with a width greater than a thickness, a plurality of fluid flow channels (51) formed inside thereof along the longitudinal direction, and the multiple-hole metal tube (45) having an opposing surface (65) disposed opposite the outer surface (61) on the one side of the metal tube (47) and joined by at least part thereof to the outer surface (61) on the one side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram illustrating a heat pump type hot water supply apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view illustrating a heat exchanger according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view taken along the line in FIG. 2.

FIG. 4 is a cross-sectional view taken along the IV-IV line in FIG. 3.

FIG. 5 is a front view illustrating a method for manufacturing a heat exchanger by resistance welding.

FIG. 6 is a perspective view illustrating a metal tube and a multiple-hole metal tube that have been resistance welded.

FIG. 7 is a cross-sectional view illustrating a heat exchanger according to the second embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating a heat exchanger according to the third embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating a heat exchanger according to the fourth embodiment of the present invention.

FIG. 10 is a perspective view illustrating a metal tube in the heat exchanger according to the fourth embodiment.

FIG. 11 is a plan view illustrating the metal tube in the heat exchanger according to the fourth embodiment.

FIG. 12 is a side view illustrating the metal tube in the heat exchanger according to the fourth embodiment.

FIG. 13 is a cross-sectional view taken along the XIII-XIII line in FIG. 11.

FIG. 14A is a cross-sectional view taken along the XIVa-XIVa line in FIG. 11. FIG. 14B is a cross-sectional view taken along the XIVb-XIVb line in FIG. 11. FIG. 14C is a cross-sectional view taken along the XIVc-XIVc line in FIG. 11.

FIG. 15 is a cross-sectional view illustrating Variation Example 1 of the metal tube.

FIG. 16 is a cross-sectional view illustrating Variation Example 2 of the metal tube.

FIG. 17A is a perspective view illustrating a heat exchanger according to the fifth embodiment of the present invention. FIG. 17B is a plan view illustrating a metal tube of the heat exchanger. FIG. 17C is a cross-sectional view taken along the XVIIc-XVIIc line in FIG. 17B. FIG. 17D is a cross-sectional view taken along the XVIId-XVIId line in FIG. 17B.

FIG. 18A is a cross-sectional view illustrating bending of the heat exchanger according to the fifth embodiment. FIG. 18B is a cross-sectional view illustrating bending of a heat exchanger with a shape of protruding portions different from that of the aforementioned heat exchanger.

FIG. 19 is a plan view illustrating a variation example of the metal tube in the heat exchanger according to the fifth embodiment.

FIG. 20 is a perspective view illustrating a heat exchanger according to the sixth embodiment of the present invention.

FIG. 21A is a perspective view illustrating a metal sheet for forming a metal tube of the heat exchanger according to the sixth embodiment. FIG. 21B is a perspective view illustrating the metal tube of the heat exchanger according to the sixth embodiment. FIG. 21C is a cross-sectional view illustrating the metal tube of the heat exchanger according to the sixth embodiment.

FIG. 22A is a plan view illustrating a variation example of the metal tube in the heat exchanger according to the sixth embodiment. FIG. 22B is a cross-sectional view thereof.

FIG. 23A is a perspective view illustrating a heat exchanger according to the seventh embodiment of the present invention. FIG. 23B is a perspective view illustrating a variation example thereof. FIG. 23C is a perspective view illustrating another variation example.

FIGS. 24A and 24B are cross-sectional views illustrating yet another variation example of the heat exchanger according to the seventh embodiment. FIG. 24C is a cross-sectional view illustrating yet another variation example of the heat exchanger according to the seventh embodiment.

FIG. 25 is a cross-sectional view illustrating a heat exchanger according to the eighth embodiment of the present invention.

FIGS. 26A and 26B are plan views illustrating a process for manufacturing a metal tube for a heat exchanger according to the ninth embodiment of the present invention. FIG. 26C is a cross-sectional view taken along the XXVIc-XXVIx line in FIG. 26B.

FIG. 27A is a plan view illustrating the state in which the relative positions of the first protruding portion and second protruding portion of the metal tube in the heat exchanger according to the ninth embodiment have shifted. FIG. 27B is a cross-sectional view taken along the XXVIIb-XXVIIb line in FIG. 27A.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

An embodiment of the present invention will be described below in greater detail with reference to the appended drawings.
<Heat Pump Type Hot Water Supply Apparatus>
FIG. 1 is a configuration diagram illustrating a heat pump type hot water supply apparatus 11 according to an embodiment of the present invention. As shown in FIG. 1, the heat pump type hot water supply apparatus 11 is provided with a coolant circuit 13 where a coolant is circulated and a hot water storage circuit 17 for boiling low-temperature water by heat exchange with the coolant of the coolant circuit 13 and storing high-temperature water in a tank 15.
The coolant circuit 13 has a compressor 19, a heat exchanger (water heat exchanger) 21, an expansion valve (pressure reducing mechanism) 23, an evaporator 25, and pipes connecting these components. For example, carbon dioxide can be used as the coolant circulating in the coolant circuit 13. When carbon dioxide is used as the coolant, the coolant is compressed to a pressure equal to or higher than a critical pressure by the compressor 19.
The hot water storage circuit 17 has the tank 15 for storing water, a water inlet pipe 27 for introducing water from the tank 15 into the heat exchanger 21, a hot water outlet pipe 29 for returning water heated by heat exchange with the heat exchanger 21 into the tank 15, and a pump 31 that causes water to circulate in the hot water storage circuit 17.
The hot water supply apparatus 11 is provided with a control unit 33 that controls the coolant circuit 13 and the hot water storage circuit 17. By driving the compressor 19 of the coolant circuit 13 and the pump 31 of the hot water storage circuit 17, the control unit 33 introduces low-temperature water located in the tank 15 from a water outlet port provided in the bottom portion of the tank 15 into the heat exchanger 21 through the water inlet pipe 27. The low-temperature water introduced into the heat exchanger 21 is heated in the heat exchanger 21 and returned into the tank 15 from the water inlet port provided in the upper portion of the tank 15 via the hot water outlet pipe 29. As a result, high-temperature water is stored in the upper portion inside the tank 15, and the water temperature decreases toward the lower portion of the tank.
The tank 15 is provided with a hot water supply pipe 35 for taking out the high-temperature water stored in the tank 15 from the upper portion thereof and supplying the high-temperature water into a bath or the like and a water supply pipe 37 for supplying low-temperature water such as tap water to the bottom portion of the tank 15.
<Heat Exchanger>

First Embodiment

FIG. 2 is a perspective view illustrating the heat exchanger 21 according to the first embodiment of the present invention. As shown in FIG. 2, the heat exchanger 21 has a structure that is spirally wound so that one end 41 in the longitudinal direction is disposed on the inner side and the other end 43 in the longitudinal direction is disposed on the outer side.
The heat exchanger 21 performs heat exchange between the coolant circulating in the coolant circuit 13 and water circulating in the hot water storage circuit 17 in the hot water supply apparatus 11 shown in FIG. 1. The directions of the coolant and water flowing in the heat exchanger 21 are mutually opposite directions as shown in FIG. 1. Therefore, where either of the coolant and water flows from the one end 41 to the other end 43 of the heat exchanger 21, the other fluid flows from the other end 43 toward the one end 41. The temperature of water can thus be regulated by performing heat exchange between the water and coolant as the coolant and water pass through inside the heat exchanger 21.
FIG. 3 is a cross-sectional view taken along the line in FIG. 2. As shown in FIG. 3, the heat exchanger 21 has a structure in which a first multiple-hole metal tube 45, a metal tube 47, and a second multiple-hole metal tube 49 are stacked in the thickness direction in the order of description. These metal tubes 45, 47, 49 are integrated by joining the opposing outer surfaces thereof by joining by the below-described resistance welding.
The first multiple-hole metal tube 45 and the second multiple-hole metal tube 49 have a flat shape with a width greater than a thickness. A plurality of coolant flow channels 51 extending in the longitudinal direction are formed inside these multiple- hole metal tubes 45, 49. The plurality of coolant flow channels 51 are mutually independent and arranged side by side in a row in the width direction. The coolant circulating in the coolant circuit 13 flows in the coolant flow channels 51. In the first multiple-hole metal tube 45 and the second multiple-hole metal tube 49, a drift current of the coolant flowing in the coolant flow channels 51 can be inhibited because the tubes have multiple holes.
The metal tube 47 has a flat shape with a width greater than a thickness. A fluid flow channel 53 extending in the longitudinal direction is formed inside the metal tube 47. Water circulating in the hot water storage circuit 17 flows in the fluid flow channel 53. The metal tube 47 has an outer surface 61 at one side and an outer surface 63 at the other side in the thickness direction. The first multiple-hole metal tube 45 has an opposing surface 65, which is opposite the outer surface 61 on one side of the metal tube 47, and is stacked on the one side in the thickness direction of the metal tube 47. The second multiple-hole metal tube 49 has an opposing surface 67, which is opposite the outer surface 63 on the other side of the metal tube 47, and is stacked on the other side in the thickness direction of the metal tube 47.
At least part of the opposing surface 65 of the first multiple-hole metal tube 45 is fused to the outer surface 61. At least part of the opposing surface 67 of the second multiple-hole metal tube 49 is fused to the outer surface 63. By increasing the ratio of fusion of the opposing surfaces 65, 67 to the outer surfaces 61, 63, it is possible to increase the degree of intimate contact between the opposing surfaces 65, 67 and the outer surfaces 61, 63 and increase the heat exchange efficiency of the heat exchanger 21. The ratio of fusion of the opposing surfaces 65, 67 to the outer surfaces 61, 63 can be adjusted by changing welding conditions during resistance welding. More specifically, the ratio of fusion of the opposing surfaces 65, 67 to the outer surfaces 61, 63 can be increased by setting conditions such as to decrease the welding rate (feed rate) during resistance welding, increase the current value during welding, and increase the pressurizing force in the thickness direction during welding. Therefore, from the standpoint of heat exchange efficiency of the heat exchanger 21, it is preferred that substantially the entire opposing surfaces 65, 67 be fused to the outer surfaces 61, 63.
FIG. 4 is a cross-sectional view taken along the Iv-Iv line in FIG. 3. As shown in FIG. 3 and FIG. 4, the metal tube 47 has, in a fluid flow channel 53 thereof, support members (support portions) 55 that inhibit deformation in the thickness direction. The support members 55 are constituted by a plurality of first columnar bodies 55 a arranged side by side in three rows along the longitudinal direction of the fluid flow channel 53 at an inner surface 57 on one side in the thickness direction of the fluid flow channel 53 and a plurality of second columnar bodies 55 b that are arranged side by side in three rows along the longitudinal direction of the fluid flow channel 53 at an inner surface 59 on the other side in the thickness direction of the fluid flow channel 53.
The first columnar body 55 a is joined by the base end portion thereof to the inner surface 57 and extends toward the inner surface 59. The second columnar body 55 b is joined by the base end portion thereof to the inner surface 59 and extends toward the inner surface 57. The plurality of first columnar bodies 55 a and the plurality of second columnar bodies 55 b are arranged in a spot-like pattern almost equidistantly from the one end 41 to the other end 43 of the heat exchanger 21 in each of the rows.
The distal end portion of the first columnar body 55 a abuts on or is disposed close to the distal end portion of the opposite second columnar body 55 b. The first columnar body 55 a and the second columnar body 55 b, which are thus disposed opposite each other, form a pair and restrict deformation of the metal tube 47 in the thickness direction during resistance welding.
The first columnar body 55 a and the second columnar body 55 b may be also joined by the distal end portions thereof. Whether the distal end portions are joined to each other can be regulated by changing welding conditions during resistance welding. More specifically, the ratio of the distal end portions joined together can be increased, for example, by decreasing the welding rate (feed rate) during resistance welding, increasing the current value during welding, and increasing the pressurizing force in the thickness direction during welding.
By increasing the joining ratio of the distal end portions of the first columnar body 55 a and second columnar body 55 b, it is possible to increase the rigidity of the metal tube 47. By contrast, when the joining ratio of the distal end portions is low, flexibility of the metal tube 47 can be maintained at a certain level. Therefore, the expansion-shrinkage of the metal caused by temperature variations and strains caused by vibrations can be moderated even when the heat exchanger 21 is used in an environment in which temperature variations and vibrations can easily occur.
Metals having thermal conductivity, corrosion resistance, rigidity, and machinability can be used as materials of the metal tube 47, first multiple-hole metal tube 45, and second multiple-hole metal tube 49. Examples of suitable metals include aluminum and aluminum alloys. The support members 55 may be from a material identical to that of the outer peripheral portion of the metal tube 47.
As described hereinabove, in the present embodiment, the support members 55, which inhibit deformation of the metal tube 47 in the thickness direction, are located in the fluid flow channel 53. Therefore, the metal tube 47 and multiple- hole metal tubes 45, 49 that are stacked in the thickness direction can be joined by resistance welding, while pressurizing the tubes in the thickness direction by a pair of roller electrodes 71, 73. Since the heat exchanger can be manufactured by resistance welding that excels in productivity, the cost can be reduced. Further, in the present embodiment, the metal tube 47 has support members 55 in the fluid flow channel 53. Therefore, deformation of the metal tube 47 can be inhibited even in long-term use of the heat exchanger.
Further, according to the present embodiment, the plurality of first columnar bodies 55 a and second columnar bodies 55 b that have distal end portions abutted on each other or disposed close to each other are arranged along the longitudinal direction of the fluid flow channel 53. Therefore, deformation of the metal tube 47 along the longitudinal direction can be inhibited over a long period. Moreover, since a configuration is used in which these columnar bodies 55 a, 55 b are arranged in a spot-like pattern in the longitudinal direction, the increase in resistance to flow of fluid in the fluid flow channel 53 caused by the arrangement of support members 55 can be inhibited and smooth fluid flow can be ensured.
Further, in the present embodiment, when some or all of the plurality of first columnar bodies 55 a and the plurality of second columnar bodies 55 b are joined to each other by the distal end portions thereof, the rigidity of the metal tube 47 can be increased. As a result, deformation of the metal tube 47 can be inhibited over a long period.
According to the present embodiment, since the multiple- hole metal tubes 45, 49 are stacked on both sides in the thickness direction of the metal tube 47, the efficiency of heat exchange between the coolant and water can be further increased.
In the present embodiment, when the opposing surfaces of the multiple- hole metal tubes 45, 49 facing the outer surfaces of the metal tube 47 are substantially entirely fused, the efficiency of heat exchange between the coolant and water can be further increased.
In the present embodiment, since a spirally wound configuration is used in which the one end 41 in the longitudinal direction is disposed on the inner side and the other end 43 in the longitudinal direction is disposed on the outer side, the dead space can be reduced and the heat exchanger 21 can be reduced in size.
Further, in the present embodiment, since the support members 55 that inhibit deformation of the metal tube 47 in the thickness direction are present in the fluid flow channel 53, the following effect can be obtained in addition to the abovementioned effect of inhibiting deformation during resistance welding. Thus, the heat exchanger 21 of the present embodiment is sometimes used in a bent form for example such as shown in FIG. 2. For example, in the case of the form illustrated by FIG. 2, some portions of the entire heat exchanger 21 in the longitudinal direction are curved, whereas other portions remain straight. In the curved portions, the support members 55 of the metal tube 47 have a function of inhibiting deformation of the metal tube 47 in the thickness direction during bending. Meanwhile, in the straight portions, the support members 55 of the metal tube 47 function as barriers such that collide with the fluid flowing inside the metal tube 47 and cause moderate turbulence. Heat transfer between the fluid and the metal tube 47 is enhanced by the moderate turbulence of the fluid. This result is likewise demonstrated in the below-described other embodiments.
(Manufacturing Method)
An example of the method for manufacturing the heat exchanger 21 will be described below. FIG. 5 is a front view illustrating the method for manufacturing the heat exchanger 21. As shown in FIG. 5, for example, a resistance welding apparatus 100 can be used for manufacturing the heat exchanger 21.
First, the resistance welding apparatus 100 will be explained. The resistance welding apparatus 100 is provided with a pair of roller electrodes 71, 73, a pressurizing device 75 that applies pressure to the roller electrode 71, a power supply device 79 that supplies electric power to the pressurizing device 75 and the roller electrodes 71, 73, and a control unit (not shown in the figure) that controls the operation of each unit.
The roller electrode 71 and the roller electrode 73 have a substantially round columnar shape and respectively have rotating shafts 72, 74 in the center thereof. The rotating shaft 72 and the rotating shaft 74 are disposed substantially parallel to each other. The width of the roller electrodes 71, 73 in the axial direction is designed to be greater than the width of the metal tube 47 and multiple- hole metal tubes 45, 49 that are the welding objects.
A motor (not shown in the figure) is connected to the rotating shaft 72, 74, and the shafts are supported on a support table (not shown in the figure) in a state in which each shaft can rotate about the axis thereof. The motor is connected to the power supply device 79. The roller electrode 71 and the roller electrode 73 rotate in the mutually opposite direction. For example, in the configuration shown in FIG. 5, the roller electrode 71 rotates counterclockwise and the roller electrode 73 rotates clockwise. Further, the roller electrode 71 is supported on the support table so as to enable the movement thereof in the direction of approaching the roller electrode 73 and in the opposite direction (up-down direction in FIG. 5). These roller electrodes 71, 73 are connected to the power supply device 79, and electric power is supplied thereto from the power supply device 79 during resistance welding. It is possible to use a configuration in which only the roller electrode 71 moves in the up-down direction, as in the present embodiment, or a configuration in which the two roller electrodes 71, 73 move in the up-down direction.
The pressurizing device 75 is provided with a cylindrical cylinder 78, a piston 77 disposed inside the cylinder 78, and a pump (not shown in the figure) that generates energy such as air pressure or oil pressure. Where electric power is supplied from the power supply device 79 to the pressurizing device 75, the pump is driven and the piston 77 is slidingly moved in a predetermined direction inside the cylinder 78. As a result, the roller electrode 71 is pressurized. The pressurized roller electrode 71 moves toward the roller electrode 73, and the metal tube 47 and the multiple- hole metal tubes 45, 49 disposed between the roller electrodes 71, 73 are pressurized in the thickness direction.
Each manufacturing step will be described below. First, in a metal tube forming step, the metal tube 47, first multiple-hole metal tube 45, and second multiple-hole metal tube 49 are fabricated.
The metal tube 47 is obtained by bending a long thin metal sheet (not shown in the figure) so that the end portions thereof in the width direction face each other and an internal space is formed along the longitudinal direction and then joining together the opposing end sides. The internal space extending in the longitudinal direction serves as the fluid flow channel 53.
Prior to bending the metal sheet, the base end portions of the first columnar bodies 55 a and the base end portions of the second columnar bodies 55 b are joined by welding or the like at predetermined positions in the regions that will be the opposing inner surface 57 and inner surface 59 after the bending is completed. Then, the metal sheet is bent, while controlling the bending position so that the first columnar bodies 55 a and the second columnar bodies 55 b face each other, and the end portions of the metal sheet are joined together. As a result, the metal tube 47 is obtained in which the first columnar bodies 55 a and the second columnar bodies 55 b are provided in the internal fluid flow channel 53.
The first multiple-hole metal tube 45 and the second multiple-hole metal tube 49 are obtained, for example, by extruding a metal material by using a die provided with an extrusion outlet port having a cross-sectional shape such as shown in FIG. 3.
The metal tube 47, first multiple-hole metal tube 45, and second multiple-hole metal tube 49 obtained in the metal tube forming step are then stacked. As shown in FIG. 5, the first multiple-hole metal tube 45, metal tube 47, and second multiple-hole metal tube 49 are arranged so that longitudinal directions and thickness directions thereof are oriented in the same respective directions and the metal tubes are stacked in the thickness direction in the order of description.
The first multiple-hole metal tube 45, metal tube 47, and second multiple-hole metal tube 49 that have thus been stacked in the stacking step are supplied between the roller electrodes 71, 73, fed along the longitudinal direction, while being pressurized in the thickness direction by the roller electrodes 71, 73. In this process, an electric current is supplied through the roller electrodes 71, 73 and the opposing outer surfaces of the metal tubes are resistance welded (seam welded) together. As a result, the linear heat exchanger 21 is obtained in which the metal tubes are integrated as shown in FIG. 6. In the heat exchanger 21, the outer surfaces 61, 63 of the metal tube 47 and the opposing surfaces 65, 67 of the multiple- hole metal tubes 45, 49 are fused and a nugget 76 is continuously formed along the longitudinal direction in the side portion.
The resistance welding conditions include the pressurizing force created by the roller electrodes 71, 73, conduction time, standby time, current value during welding, welding rate (feed rate), electrode shape, and the like. These conditions are set as appropriate according to the welding object, application, etc. The abovementioned resistance welding may be intermittent welding in which conduction periods and standby periods are repeated or continuous welding in which the conduction is continuous.
In the present embodiment, since the first columnar bodies 55 a and the second columnar bodies 55 b are provided in the fluid flow channel 53 of the metal tube 47, where pressurization is performed by the roller electrodes 71, 73 in the thickness direction, the metal tube 47 is slightly deformed in the thickness direction and the distal end portions of some or all of the plurality of first columnar bodies 55 a and the plurality of second columnar bodies 55 b abut on each other. Where the distal end portions thus abut on each other, deformation of the metal tube 47 in the thickness direction can be inhibited. Further, since the electric current flowing through the roller electrodes 71, 73 to the metal tube 47 flows not only through the outer peripheral portion of the metal tube 47, but also through the first columnar bodies 55 a and the second columnar bodies 55 b that abut on each other by the distal end portions thereof, the fusion of the adjacent opposing surfaces 65, 67, which are provided with the first columnar bodies 55 a and the second columnar bodies 55 b that abut on each other by the distal end portions thereof, and the outer surfaces 61, 63 is enhanced. As a result, the fusion ratio of the opposing surfaces 65, 67 and the outer surfaces 61, 63 can be increased.
Further, when an electric current flows through the roller electrodes 71, 73, the electric current also flows through the first columnar bodies 55 a and the second columnar bodies 55 b. Therefore, depending on the resistance welding conditions, the distal end portions are joined together in some or all of the pairs of the plurality of columnar bodies.
The heat exchanger 21 can be used as is, that is, in the linear form such as shown in FIG. 6, or may be used upon bending spirally as shown in FIG. 2. In the case of the form shown in FIG. 2, the bending is performed so that the thickness direction of the metal tubes 45, 47, 49 is in the radial direction of the spiral.
As described hereinabove, with the manufacturing method using resistance welding, the metal tube 47 having the support members 55 in the fluid flow channel 53 and the multiple- hole metal tubes 45, 49 are stacked and disposed between the roller electrodes 71, 73, and the metal tube 47 and the multiple- hole metal tubes 45, 49 are moved along the longitudinal direction and resistance welded, while being pressurized in the thickness direction. Therefore, deformation of the metal tube 47 by pressure during resistance welding can be inhibited.
Thus, during such resistance welding, the welding can be performed in a state in which a sufficient pressure is applied by the roller electrodes 71, 73 in the thickness direction so that the outer surfaces 61, 63 of the metal tube 47 and the opposing surfaces 65, 67 of the multiple-hole metal tubes that are disposed opposite the outer surfaces are brought into intimate contact with each other. As a result, the joining surface area of the outer surfaces 61, 63 and the opposing surfaces 65, 67 can be increased, deformation of the fluid flow channel 53 is inhibited and a flow channel necessary for the fluid to flow smoothly is ensured. Therefore, the efficiency of heat exchange between the coolant and fluid can be increased. Furthermore, since the metal tubes can be joined by resistance welding, which is a simple method, productivity can be increased.

Second Embodiment

FIG. 7 is a cross-sectional view illustrating the heat exchanger according to the second embodiment of the present invention. As shown in FIG. 7, in the heat exchanger 21, the structure of the support members 55 is different from that of the first embodiment. Other components are assigned with same reference numerals as in the first embodiment and the explanation thereof is herein omitted.
The support members (support portions) 55 according to the second embodiment are constituted by a plurality of columnar bodies arranged along the longitudinal direction of the fluid flow channel 53. One end in an axial direction of each columnar body is joined to an inner surface (inner surface 57 or inner surface 59) on either side in the thickness direction of the fluid flow channel 53, and the other end in the axial direction of each columnar body is disposed on the inner surface side on the other side in the thickness direction of the fluid flow channel 53. All of the plurality of columnar bodies may be joined by one end thereof to the inner surface on the same side, or some of them may be joined to the inner surface on the other side.
Both ends in the axial direction of some or all of the plurality of columnar bodies are respectively joined to the inner surface 57 on one side and the inner surface 59 on the other side of the fluid flow channel 53. When both ends of the columnar bodies are joined, the rigidity of the metal tube 47 can be increased. Where only one end of the columnar bodies is joined and the other end is not joined, the flexibility of the metal tube 47 can be maintained at a certain level.
The metal tube 47 according to the second embodiment may be fabricated in the same manner as the metal tube 47 according to the first embodiment. Thus, the metal tube 47 is obtained by bending a flat metal sheet (not shown in the figure) so as to form a hollow portion along the longitudinal direction and joining by welding the side end portions thereof. The hollow portion along the longitudinal direction serves as the fluid flow channel 53.
Prior to bending the metal sheet, one end of each columnar body is joined by welding or the like in the region that will be the inner surface 57 or the inner surface 59 after the bending is completed. Then, the metal sheet is bent and the side end portions of the metal sheet are joined together. As a result, the metal tube 47 is obtained in which the support members 55 constituted by a plurality of columnar bodies are provided in the internal fluid flow channel 53.
According to the second embodiment, since a plurality of columnar bodies are arranged along the longitudinal direction of the fluid flow channel 53, deformation of metal tube 47 in the longitudinal direction can be inhibited over a long period. Furthermore, since the columnar bodies are arranged in a spot-like pattern in the longitudinal direction, the increase in resistance to the flow of fluid in the fluid flow channel 53 that is caused by the support members 55 can be inhibited and the fluid can smoothly flow in the fluid flow channel.
Further, according to the second embodiment, one end of each columnar body is joined to the inner surface 57 or the inner surface 59 in the thickness direction of the fluid flow channel 53. Therefore, the columnar bodies can be prevented from displacing when pressurized in the thickness direction by the roller electrodes 71, 73 during resistance welding. As a result, a sufficient pressure can be applied in the thickness direction by the roller electrodes 71, 73 to the metal tube 47 and the multiple- hole metal tubes 45, 49 during resistance welding.
Further, in the present embodiment, a plurality of columnar bodies are provided in the fluid flow channel 53 of the metal tube 47. Therefore, where pressurization is performed in the thickness direction by the roller electrodes 71, 73, the metal tube 47 is slightly deformed in the thickness direction and other ends of some or all of the plurality of columnar bodies abut on the inner surface 57 or the inner surface 59 of the metal tube 47. Such an abutment of other ends of the columnar bodies inhibits deformation of the metal tube 47 in the thickness direction. Further, since the electric current flowing through the roller electrodes 71, 73 to the metal tube 47 flows not only through the outer peripheral portion of the metal tube 47, but also through the columnar bodies that abut by the other ends thereof on the inner surface, the fusion of the adjacent opposing surfaces 65, 67, which are provided with the columnar bodies that abut by the other ends thereof on the inner surface, and the outer surfaces 61, 63 is enhanced. As a result, the fusion ratio of the opposing surfaces 65, 67 and the outer surfaces 61, 63 can be increased.
Further, since the electric current also flows through the columnar bodies when flowing through the roller electrodes 71, 73, the columnar bodies can be joined to the inner surface 57 or the inner surface 59 under certain conditions of resistance welding.

Third Embodiment

FIG. 8 is a cross-sectional view illustrating the heat exchanger according to the third embodiment of the present invention. As shown in FIG. 8, the structure of the support member 55 of the heat exchanger 21 is different from that of the first embodiment. Other components are assigned with same reference numerals as in the first embodiment and the explanation thereof is herein omitted.
The support member (support portion) 55 according to the third embodiment is a plate-like body that is disposed along the longitudinal direction of the fluid flow channel 53 and has a corrugated cross-section perpendicular to the longitudinal direction. The plate-like body is disposed so that peaks of depressions and protrusions are continuous along the width direction of the fluid flow channel 53.
The metal tube 47 according to the third embodiment may be fabricated by bending a flat metal sheet (not shown in the figure) so as to form a hollow portion along the longitudinal direction, joining the side end portions together by welding or the like, and then inserting a corrugated plate-like body into the hollow portion, or by disposing a corrugated plate-like body at a predetermined position of the metal sheet prior to bending and then performing bending and welding the side end portions to each other.
According to the third embodiment, since the support member 55 is a corrugated plate-like body, deformation of the metal tube 47 in the longitudinal direction can be inhibited over a long period. Further, since the rigidity of the support member 55 itself can be increased over that attained when the support member 55 is in the form of the above-described columnar bodies, such a configuration is particularly advantageous when a larger pressurization force is desired to be obtained with the pair of roller electrodes 71, 73. Furthermore, since the corrugated plate-like body acts to disperse the fluid flow, it is possible to regulate the fluid flow and produce a flow with low turbulence.

Fourth Embodiment

FIG. 9 is a cross-sectional view illustrating the heat exchanger 21 according to the fourth embodiment of the present invention. FIGS. 10 to 13 illustrate the metal tube 47 used in the heat exchanger 21. As shown in FIGS. 9 to 13, the structure of the support portion of the metal tube 47 of the heat exchanger 21 is different from that of the first embodiment. Other components are assigned with same reference numerals as in the first embodiment and the explanation thereof is herein omitted.
The metal tube 47 according to the fourth embodiment has a flat shape with a width greater than a thickness. Side portions at both sides in the width direction of the metal tube 47 have a circular-art cross-sectional shape, but such a shape is not limiting. For example, the side portions of the metal tube 47 may have a linear cross-sectional shape as shown in FIG. 3 or other shape. Further, the side portions at both sides in the width direction of the metal tube 47 protrude outward in the width direction from the first multiple-hole metal tube 45 and the second multiple-hole metal tube 49, but such a configuration is not limiting. For example, the side portions of the metal tube 47 may have a shape that does not protrude outward in the width direction as shown in FIG. 3. The fluid flow channel 53 extending in the longitudinal direction is formed inside the metal tube 47.
As shown in FIGS. 11 to 13, the metal tube 47 has, in the fluid flow channel 53 thereof, the support portions 55 that inhibit deformation in the thickness direction. The support portions 55 are constituted by a plurality of first protruding portions 55 a arranged along the longitudinal direction of the fluid flow channel 53 at the inner surface 57 on one side in the thickness direction of the fluid flow channel 53 and a plurality of second protruding portions 55 b arranged along the longitudinal direction of the fluid flow channel 53 at the inner surface 59 on the other side in the thickness direction of the fluid flow channel 53. Each first protruding portion 55 a extends from the inner surface 57 on one side toward the inner surface 59 on the other side, and each second protruding portion 55 b extends from the inner surface 59 on the other side toward the inner surface 57 on one side.
These first protruding portions 55 a and second protruding portions 55 b are formed by press forming a metal sheet as described hereinbelow. Therefore, the outer surface 61 on the one side in the thickness direction recedes on the inner surface 59 side, thereby causing the first protruding portions 55 a to protrude to the inner surface 59 side in the fluid flow channel 53. The outer surface 63 on the other side in the thickness direction recedes on the inner surface 57 side, thereby causing the second protruding portions 55 b to protrude to the inner surface 57 side in the fluid flow channel 53. A first receding portion 55 c is formed on the rear surface (outer surface 61) of the first protruding portion 55 a, and a second receding portion 55 d is formed on the rear surface (outer surface 63) of the second protruding portion 55 b.
As shown in FIG. 11, in a plan view of the metal tube 47, the support portions 55 have the following specific features because the first protruding portions 55 a and second protruding portions 55 b are arranged in a regular manner.
The support portions 55 are arranged regularly so as to form five rows (row A1 to row A5), each row extending in the longitudinal direction. The first protruding portions 55 a and second protruding portions 55 b are arranged together in the row A1 to row A5. In the row A3 among these rows, the second protruding portions 55 b are disposed at positions facing the first protruding portions 55 a in the thickness direction. Thus, the second protruding portions 55 b are provided at all of the respective positions facing the first protruding portions 55 a of the row A3 shown in FIG. 11. This row A3, from among the five rows, is positioned in the central portion in the width direction of the metal tube 47.
Further, the support portions 55 are arranged regularly so as to form a plurality of rows, namely, row B1, row B2, row B3, . . . extending in the oblique direction at an angle to the longitudinal direction. The first protruding portions 55 a are disposed by five protruding portions in each of rows B2, B4, B6, but disposed by one protruding portion in each of rows B1, B3, B5. This one first protruding portion 55 a is disposed in the row A3. The second protruding portions 55 b are disposed by five protruding portions in each of rows B1, B3, B5, but disposed by one protruding portion in each of rows B2, B4, B6. This one second protruding portion 55 b is disposed in the row A3. Thus, the rows B2, B4, B6 of the first protruding portions 55 a in the oblique direction and the rows B1, B3, B5 of the second protruding portions 55 b in the oblique direction are arranged alternately along the longitudinal direction.
Therefore, in the fourth embodiment, the first protruding portions 55 a and second protruding portions 55 b are disposed opposite each other only in the row A3 (see FIG. 14C), and in other rows A1, A2, A4, A5, the first protruding portions 55 a and the second protruding portions 55 b are disposed alternately in the longitudinal direction (see FIGS. 14A and 14B). In other words, in the rows A1, A2, A4, A5, the first protruding portions 55 a are provided at positions shifted in the longitudinal direction with respect to the second protruding portions 55 b. Thus, only the row A3 is configured such that the first protruding portions 55 a and the second protruding portions 55 b are opposite each other.
Further, as shown in FIG. 11, an angle θ1 between an oblique direction D2 and the longitudinal direction D1 and an angle θ2 between an oblique direction D3 and the longitudinal direction D1 are set to mutually different values. The oblique direction D2 as referred to herein is an arrangement direction of the aforementioned rows B1, B2, . . . . The oblique direction D3 is a regular arrangement direction crossing the rows B1, B2, . . . . In the present embodiment, the angle θ1 is set to about 50 degrees and the angle θ2 is set to about 40 degrees, and the oblique direction D2 and the oblique direction D3 cross each other at about 90 degrees.
In the configuration according to the fourth embodiment, since the angle θ1 and the angle θ2 are set to different values, as mentioned hereinabove, protruding portions 55 a, 55 b are not disposed on the same line in the width direction with a position at which a random first protruding portion 55 a (or second protruding portion 55 b) is disposed. The first protruding portions 55 a and second protruding portions 55 b can thus be disposed with a certain degree of randomness in the fluid flow channel 53 and therefore pulsations can be generated in the flow of fluid in the fluid flow channel 53. As a result, for example, the occurrence of drift in the fluid flow channel 53 can be inhibited and the development of turbulent flow of the fluid in the fluid flow channel 53 can be enhanced, thereby increasing the efficiency of heat exchange.
Further, as shown in FIG. 14C, the distal end of the first protruding portion 55 a is disposed at a predetermined distance t from the distal end of the second protruding portion 55 b opposite thereto in the thickness direction. Therefore, the gap between the distal ends of the first protruding portions 55 a and the second protruding portions 55 b also serves as a flow channel for coolant. As a result, the reduction of the fluid flow channel 53 caused by the provided first protruding portions 55 a and second protruding portions 55 b can be inhibited. Further, in the present embodiment, the distal end portions of the first protruding portions 55 a are disposed at the predetermined distance from the distal end portions of the second protruding portions 55 b opposite thereto in the thickness direction, but the protruding portions may be also disposed without the distance t therebetween and the distal end portions thereof may abut on each other.
The metal tube 47 can be formed, for example, in the following manner. First, a plate-like metal sheet is pressed to form a plurality of protruding portions in predetermined positions, the protruding portions protruding in the thickness direction of the metal sheet. Then, the metal sheet is bent at positions corresponding to circular-arc side portions at both sides in the width direction of the metal tube 47 and a flat shape is obtained. The end portions of the obtained metal sheet are joined together by welding or the like. The plurality of protruding portions formed by pressing serve as the first protruding portions 55 a and second protruding portions 55 b.
As described hereinabove, in the fourth embodiment, some of the plurality of first protruding portions 55 a are provided at positions opposite the second protruding portions 55 b in the thickness direction. Therefore, where the first protruding portions 55 a and the second protruding portions 55 b disposed at positions opposite thereto abut on each other, subsequent deformation of the metal tube 47 is inhibited even when a pressure is applied in the thickness direction to the metal tube 47 during the resistance welding or bending such as described hereinabove. As a result, deformation in the thickness direction of the metal tube 47 during resistance welding or bending can be effectively inhibited.
Further, in the fourth embodiment, the first protruding portions 55 a and second protruding portions 55 b are disposed opposite each other in the central portion in the width direction. Therefore, the effect of inhibiting the deformation of the metal tube 47 can be further increased.
Further, in the fourth embodiment, the first protruding portions 55 a and second protruding portions 55 b are disposed opposite each other in the central portion in the width direction, as mentioned hereinabove, but in the rows positioned at both sides, the first protruding portions 55 a are provided at positions displaced in the longitudinal direction with respect to the second protruding portions 55 b. Therefore, deformation in the thickness direction of the metal tube 47 in the central portion in the width direction can be effectively inhibited, and narrowing of the fluid flow channel can be inhibited and a smooth fluid flow can be realized at both sides in the width direction. Further, since the first protruding portions 55 a or second protruding portions 55 b are provided on both sides in the width direction, when an unexpectedly high pressure is applied in the thickness direction, the distal end portions of the first protruding portions 55 a abut on the inner surface 59 of the metal tube 47 and the distal end portions of the second protruding portions 55 b abut on the inner surface 57 of the metal tube 47, thereby making it possible to inhibit subsequent deformation of the metal tube 47.
Further, in the forth embodiment, as described hereinabove, the plurality of first protruding portions 55 a are arranged so as to form five rows A1 to A5, each row extending in the longitudinal direction, and the first protruding portions 55 a are also arranged so as to form a plurality of rows B2, B4, B6 extending in the oblique direction at an angle to the longitudinal direction. The second protruding portions 55 b are also arranged so as to form a plurality of rows B1, B3, B5, each row extending in the oblique direction. The oblique rows of the first protruding portions 55 a and the oblique rows of the second protruding portions 55 b are disposed alternately along the longitudinal direction. When such a configuration is used, steps (protruding portions) in the thickness direction can be disposed continuously and at an angle with respect to the longitudinal direction in the fluid flow channel 53. In addition, steps (first protruding portions 55 a) on one side in the thickness direction and steps (second protruding portions 55 b) on the other side can be disposed alternately. Therefore, the occurrence of pulsations in the flow of fluid in the fluid flow channel 53 can be effectively prevented. As a result, drift in the fluid flow channel can be inhibited and the development of turbulent flow of the internal fluid can be enhanced, thereby making it possible to enhance the heat transfer effect.
Further, in the fourth embodiment, the metal tube 47 is shaped by pressing a metal sheet to form a plurality of protruding portions, which protrude in the thickness direction of the metal sheet, at predetermined positions, bending the metal sheet to obtain the aforementioned flat shape, and then joining together the end portions of the metal sheet. Therefore, it is not necessary to join by welding, for example, the columnar bodies serving as support portions to the metal sheet. As a result, the process is simplified and the production cost can be reduced.

Fifth Embodiment

FIG. 17A is a perspective view illustrating the heat exchanger 21 according to the fifth embodiment of the present invention. The structure of the protruding portion 55 serving as the support portion of the heat exchanger 21 is different from that of the first embodiment. Other components are identical to those of the heat exchanger 21 according to the first embodiment and therefore assigned with same reference numerals as in the first embodiment and the explanation thereof is herein omitted.
FIG. 17B is a plan view illustrating the metal tube 47 of the heat exchanger 21. This metal tube 47 is provided with a plurality of first protruding portions 55 a and a plurality of second protruding portions 55 b as support portions 55. The plurality of first protruding portions 55 a are arranged along the longitudinal direction of the fluid flow channel 53 at the inner surface on one side in the longitudinal direction of the fluid flow channel 53. The plurality of second protruding portions 55 b are disposed along the longitudinal direction of the fluid flow channel 53 at the inner surface on the other side in the thickness direction of the fluid flow channel 53. Each first protruding portion 55 a protrude from the inner surface on the one side toward the inner surface on the other side, and each second protruding portion 55 b protrude from the inner surface on the other side toward the inner surface on the one side. Each first protruding portion 55 a and each second protruding portion 55 b can be formed, for example, by press forming a metal sheet in the same manner as in the fourth embodiment.
As shown in FIG. 17B, the size in the width direction W of each first protruding portion 55 a and second protruding portion 55 b is less than the size thereof in the longitudinal direction L. Thus, each of the first protruding portions 55 a and second protruding portions 55 b has an elongated shape in the plan view thereof. The longitudinal direction of the first protruding portions 55 a and second protruding portions 55 b is substantially parallel to the longitudinal direction L of the metal tube 47.
In the fifth embodiment, all of the plurality of first protruding portions 55 a are provided, as shown in FIGS. 17C and 17D, at positions that are opposite the second protruding portions 55 b in the thickness direction. It is also possible to provide some of the plurality of first protruding portions 55 a at positions that are opposite the second protruding portions 55 b in the thickness direction and provide the remaining first protruding portions 55 a at positions that are not opposite the second protruding portions 55 b. In such a configuration, the first protruding portions 55 a provided at positions that are not opposite the second protruding portions 55 b function as obstacles that create appropriate turbulence in the fluid in the fluid flow channel 53. Where the fluid becomes appropriately turbulent, heat transfer between the fluid and the metal tube 47 is enhanced. Therefore, heat exchange efficiency of the heat exchanger can be increased.
According to the fifth embodiment, the opposing first protruding portions 55 a and second protruding portions 55 b are disposed along the longitudinal direction. Therefore, such a configuration is particularly advantageous in terms of the effect of ensuring contact surface area of the first protruding portions 55 a and second protruding portions 55 b when the heat exchanger 21 is bent, for example, spirally as shown in FIG. 2.
When the heat exchanger 21 is bent as shown in FIG. 2, the elongation of material in the portion of the metal tube 47 on the radially outer side is large and the elongation of material in the portion on the radially inner side is small, as shown in FIG. 18A. Therefore, relative positions of the first protruding portions 55 a and second protruding portions 55 b can be easily displaced. In the fifth embodiment, the longitudinal direction of the first protruding portions 55 a and the longitudinal direction of the second protruding portions 55 b are arranged along the longitudinal direction of the metal tube 47. Therefore, the contact state of the first protruding portions 55 a and second protruding portions 55 b can be maintained even when the relative positions of the first protruding portions and second protruding portions are somewhat displaced. As a result, bending with a small curvature radius can be performed.
Where the size of the first protruding portions 55 a in the longitudinal direction and the size of the second protruding portions 55 b in the longitudinal direction are decreased, as shown in FIG. 18B, the allowance range in which the aforementioned contact state can be maintained against the displacement of the relative positions is decreased accordingly.
FIG. 19 is a plan view illustrating a variation example of the metal tube 47 in the heat exchanger 21 according to the fifth embodiment. As shown in FIG. 19, in the metal tube 47 according to this variation example, the first protruding portions 55 a and the second protruding portions 55 b have a wedge-like shape. In other words, the first protruding portions 55 a and the second protruding portions 55 b have a substantially triangular shape in a plan view thereof. In this variation example, the first protruding portions 55 a and the second protruding portions 55 b are disposed so that the apexes of the triangles face the flow direction F of the fluid in a plan view. As a result, the fluid flows smoothly along the side surfaces of the first protruding portions 55 a and second protruding portions 55 b and therefore the occurrence of pressure loss inside the metal tube 47 can be inhibited.
Further, in the fifth embodiment illustrated by FIGS. 17 to 19, the size of the protruding portions 55 in the width direction, that is, the size in the direction perpendicular to the flow direction F of the fluid, is less than the size of the protruding portions 55 in the longitudinal direction. As a result, the increase in resistance encountered by the fluid flowing in the metal tube 47 can be inhibited.

Sixth Embodiment

FIG. 20 is a perspective view illustrating the heat exchanger 21 according to the sixth embodiment of the present invention. The structure of the metal tube 47 of the heat exchanger 21 according to the sixth embodiment is different from that of the first embodiment. Other components are identical to those of the heat exchanger 21 according to the first embodiment and therefore assigned with same reference numerals as in the first embodiment and the explanation thereof is herein omitted.
The metal tube 47 in this heat exchanger 21 is provided with the fluid flow channel 53 and the support portion 55. The fluid flow channel 53 has a first fluid flow channel 53 a and a second fluid flow channel 53 b extending in the longitudinal direction L and arranged parallel to each other in the width direction W. The support portion 55 is provided in the fluid flow channel 53 constituted by the first fluid flow channel 53 a and the second fluid flow channel 53 b arranged parallel to each other in the width direction W. The metal tube 47 is obtained by bending a flat metal sheet M and joining the predetermined portions as shown in FIG. 21A.
The first fluid flow channel 53 a is formed in the following manner. First, the metal sheet M is bent at a bending position B1 extending along the longitudinal direction L and the metal sheet M is bent into a tube so that the end side El on one side in the width direction of the metal sheet M comes into contact with a surface S on one side of the metal sheet M. Then, the end side E1 is joined for example by welding to the surface S along the longitudinal direction L, thereby forming the first fluid flow channel 53 a.
Likewise, the second fluid flow channel 53 b is formed in the following manner. First, the metal sheet M is bent at a bending position B2 extending along the longitudinal direction L and the metal sheet M is bent into a tube so that the end side E2 on one side in the width direction of the metal sheet M comes into contact with the surface S on one side of the metal sheet M. Then, the end side E2 is joined for example by welding to the surface S along the longitudinal direction L, thereby forming the second fluid flow channel 53 b.
As shown in FIG. 21C, the support portion 55 is constituted by portions of the metal sheet M, that is, by portions extending upward in the height direction (thickness direction of the metal tube 47) from the end side E1 and end side E2. In the support portion 55, zones in the vicinity of the end side E1 and end side E2 abut on each other. Further, the support portion 55 branches to both sides in the width direction W from the vicinity of the central portion in the height direction. The branched portions of the support portion 55 extend obliquely from the height direction to the left and to the right.
Since the metal tube 47 according to the sixth embodiment is formed in the above-described mariner by using the metal sheet M, the metal tube has a substantially B-like cross-sectional shape. The support portion 55 thus extending along the longitudinal direction L can be formed by a simple manufacturing method. Further, since the support portion 55 of the metal tube 47 extends continuously along the longitudinal direction L, the configuration demonstrates excellent effect of inhibiting deformation in the thickness direction.
FIG. 22A is a plan view illustrating a variation example of the metal tube 47 according to the sixth embodiment. FIG. 22B is a cross-sectional view of the metal tube. As shown in FIGS. 22A and 22B, the metal tube 47 has a plurality of protruding portions 55 c and a plurality of protruding portions 55 d in the first fluid flow channel 53 a and in the second fluid flow channel 53 b, respectively.
The plurality of protruding portions 55 c are arranged in a row along the longitudinal direction L at the inner surface 57 on one side in the thickness direction of the fluid flow channels 53 a, 53 b. The plurality of protruding portions 55 d are arranged in a row along the longitudinal direction L at the inner surface 59 on the other side in the thickness direction of the fluid flow channels 53 a, 53 b. The protruding portions 55 c extend from the inner surface 57 on one side toward the inner surface 59 on the other side, and the protruding portions 55 d extend from the inner surface 59 on the other side toward the inner surface 57 on one side.
The protruding portions 55 c and protruding portions 55 d may be disposed opposite each other in the thickness direction or at positions that are not opposite each other. When the protruding portions are disposed at the opposing positions, the protruding portions 55 c and the protruding portions 55 d, together with the support portion 55, function as support portions inhibiting deformation of the metal tube 47 in the thickness direction. When the protruding portions are disposed at positions that are not opposite each other, the protruding portions 55 c and the protruding portions 55 d function as obstacles that create appropriate turbulence in the fluid in the fluid flow channel 53. Where the fluid becomes appropriately turbulent, heat transfer between the fluid and the metal tube 47 is enhanced.
In the metal tube 47 according to the sixth embodiment, the support portion 55 can be formed in the fluid flow channel 53 by using the above-described manufacturing method. Therefore, the protruding portions for increasing the heat transfer performance can be provided in the fluid flow channels 53 a, 53 b by a free design (design focused on the increase in heat transfer performance), as in the variation example illustrated by FIGS. 22A and 22B.

Seventh Embodiment

FIG. 23A is a perspective view illustrating the heat exchanger 21 according to the seventh embodiment of the present invention. The structure of the metal tube 47 of the heat exchanger 21 according to the seventh embodiment is different from that of the first embodiment. Other components are identical to those of the heat exchanger 21 according to the first embodiment and therefore assigned with same reference numerals as in the first embodiment and the explanation thereof is herein omitted.
The metal tube 47 in the heat exchanger 21 according to the seventh embodiment is constituted by a first metal tube 47 a and a second metal tube 47 b arranged parallel to each other in the width direction W. The first metal tube 47 a and the second metal tube 47 b are cylindrical flat pipes formed separately from each other by an appropriate method, for example, extrusion forming. Therefore, the fluid flow channel 53 of the metal tube 47 is constituted by the first fluid flow channel 53 a inside the first metal tube 47 a and the second fluid flow channel 53 b inside the second metal tube 47 b. These first fluid flow channel 53 a and second fluid flow channel 53 b are partitioned by the support portion 55. In other words, the support portion 55 is provided in the fluid flow channel 53 constituted by the first fluid flow channel 53 a and the second fluid flow channel 53 b arranged parallel to each other in the width direction W.
The support portion 55 is constituted by a side wall 55 a of the first metal tube 47 a and a side wall 55 b of the second metal tube 47 b. The side wall 55 a and the side wall 55 b are in surface contact with each other. Protruding portions 55 c and protruding portions 55 d such as shown in FIGS. 22A and 22B may be provided in the fluid flow channels 53 a, 53 b.
In the seventh embodiment, the cylindrical flat pipes can be formed in a simple manner by an appropriate method, for example, extrusion forming. Therefore, the production cost can be reduced.
The number of flat tubes arranged parallel to each other in the width direction W is not limited to 2 and may be 3, as shown in FIG. 23B, or 4 or more.
As shown in FIG. 23C, an integrated flat tube in which the first fluid flow channel 53 a and second fluid flow channel 53 b are partitioned by the support portion 55 by using a method such as extrusion forming can be also used as the metal tube 47. The support portion 55 of the metal tube 47 is formed continuously in the longitudinal direction L and partitions the first fluid flow channel 53 a and second fluid flow channel 53 b.
The metal tube 47 such as shown in FIG. 24B may be also used. This metal tube 47 is obtained by combining two tubular members 47 a, 47 b with a substantially P-like cross-sectional shape, as shown in FIG. 24A. The tubular members 47 a, 47 b are formed by bending a metal sheet. Thus, the tubular member 47 a is formed by folding the metal sheet at a bending position extending along the longitudinal direction and bending the metal sheet to a substantially P-like shape such that the end side on one side in the width direction of the metal sheet is brought into contact with the surface on one side of the metal sheet. The tubular member 47 b is formed in a similar manner.
The tubular member 47 a has the first fluid flow channel 53 a, and the tubular member 47 b has the second fluid flow channel 53 b. The tubular member 47 a and the tubular member 47 b have flat portions 48 a, 48 b extending in the width direction W from cylindrical portions constituting the fluid flow channels 53 a, 53 b. The first fluid flow channel 53 a and the second fluid flow channel 53 b are arranged parallel to each other in the width direction W. The flat portion 48 a is disposed below the tubular member 47 b, and the flat portion 48 b is disposed below the tubular member 47 a. The side wall of the tubular member 47 a functions as the support portion 55 a, and the side wall of the tubular member 47 b functions as the support portion 55 b. The support portion 55 a and the support portion 55 b are in surface contact with each other.
With the metal tube 47 in which the tubular members 47 a, 47 b are thus combined, the entire upper surface and the entire lower surface in the thickness direction are flat. Therefore, the surface area of contact with the multiple- hole metal tubes 45, 47 can be increased. As a result, heat exchange efficiency of the heat exchanger 21 can be increased.
Further, in the metal tube 47 shown in FIG. 24C, the fluid flow channels 53 a, 53 b of the tubular member 47 a and tubular member 47 b are less than those shown in FIG. 24B, and the support member 55 a and the support member 55 b are separated so as to avoid surface contact thereof. As a result, a third fluid flow channel 53 c is additionally formed between the first fluid flow channel 53 a and the second fluid flow channel 53 b.

Eighth Embodiment

FIG. 25 is a cross-sectional view illustrating the heat exchanger 21 according to the eighth embodiment of the present invention. The structure of the metal tube 47 of the heat exchanger 21 according to the eighth embodiment is different from that of the first embodiment. Other components are identical to those of the heat exchanger 21 according to the first embodiment and therefore assigned with same reference numerals as in the first embodiment and the explanation thereof is herein omitted.
The metal tube 47 of this heat exchanger 21 is formed by spirally bending a metal sheet. The metal tube 47 has the support portion 55 and the fluid flow channel 53. The fluid flow channel 53 is constituted by the first fluid flow channel 53 a and the second fluid flow channel 53 b partitioned in the width direction W by the support portion 55. In other words, the support portion 55 is provided in the fluid flow channel 53 constituted by the first fluid flow channel 53 a and the second fluid flow channel 53 b arranged parallel to each other in the width direction W.
The support portion 55 corresponds to a portion obtained by bending the end portion on one side of the metal sheet in the width direction W in a L-like shape with a width substantially of the same order as the thickness of the first fluid flow channel 53 a. The metal sheet is bent spirally so that the support portion 55 is positioned close to the center of the metal tube 47 in the width direction W. Because of such spiral bending, a joining surface 50 a and a joining surface 50 b are in surface contact with each other. The joining surface 50 a and the joining surface 50 b can be joined by an appropriate method such as the above-described resistance welding, brazing, and soldering.
When joining by brazing, for example, the following joining can be performed. First, a braze layer is formed in advance over the entire both surfaces of the metal sheet. Then, the sheet is spirally bent in the above-described manner and processed into the shape of the metal tube 47. In this case, since the braze layer has been formed on the joining surface 50 a and the joining surface 50 b, the joining surfaces 50 a, 50 b can be joined together by heating the metal tube 47 in a heating furnace (not shown in the figure) or the like. Further, as shown in FIG. 25, a pre-assembled body obtained by pre-assembling the metal tube 47 in a state prior to joining the joining surfaces 50 a, 50 b and the multiple- hole metal tubes 45, 49 may be heated in a heating furnace or the like. Since the braze layer has been formed on both surfaces (upper and lower surfaces) in the thickness direction of the metal tube 47, not only the joining surfaces 50 a, 50 b, but also the metal tube 47 and the multiple- hole metal tubes 45, 49 can be joined together at the same time by heating the pre-assembled body in the heating furnace.
In the eighth embodiment, the entire upper surface and the entire lower surface in the thickness direction of the metal tube 47 can be flat. Therefore, the contact surface area with the multiple- hole metal tubes 45, 47 can be increased. As a result, heat exchange efficiency of the heat exchanger 21 can be improved.
Further, the metal tube 47 has a plurality of protruding portions 55 c and a plurality of protruding portions 55 d in the first fluid flow channel 53 a and the second fluid flow channel 53 b, respectively. As described above, in the metal tube 47 according to the eighth embodiment, the support portion 55 can be formed, by forming the tube by the above-described manufacturing method. Therefore, the protruding portions for increasing the heat transfer performance can be provided in the fluid flow channels 53 a, 53 b by a free design (design focused on the increase in heat transfer performance).

Ninth Embodiment

FIGS. 26A and 26B are plan views illustrating the process for manufacturing the metal tube 47 for the heat exchanger 21 according to the ninth embodiment of the present invention. FIG. 26C is a cross-sectional view taken along the XXVIc-XXVIc line in FIG. 26B. The structure of the protruding portion 55 serving as the support portion of the heat exchanger 21 is different from that of the first embodiment. Other components are identical to those of the heat exchanger 21 according to the first embodiment and therefore assigned with same reference numerals as in the first embodiment and the explanation thereof is herein omitted.
The metal tube 47 is provided with a plurality of first protruding portions 55 a and a plurality of second protruding portions 55 b serving as support portions 55. The plurality of first protruding portions 55 a are arranged along the longitudinal direction of the fluid flow channel 53 at the inner surface on one side in the thickness direction of the fluid flow channel 53. The plurality of second protruding portions 55 b are provided along the longitudinal direction of the fluid flow channel 53 at the inner surface on the other side in the thickness direction of the fluid flow channel 53. Each first protruding portion 55 a protrudes from the inner surface on the one side toward the inner surface on the other side, and each second protruding portion 55 b protrudes from the inner surface on the other side toward the inner surface on the one side. The first protruding portions 55 a and the second protruding portions 55 b are formed by press forming a metal sheet in the same manner as in the fourth embodiment.
As shown in FIG. 26B, the first protruding portions 55 a and the second protruding portions 55 b have an elongated shape in a plan view therefor. The first protruding portion 55 a and the second protruding portion 55 b opposing each other in the thickness direction are provided so as to cross each other in a plan view thereof. The longitudinal direction of the first protruding portions 55 a is inclined to one side in the width direction W of the metal tube 47 with respect to the longitudinal direction L of the metal tube 47. The longitudinal direction of the second protruding portions 55 b is inclined toward the other side in the width direction W with respect to the longitudinal direction L of the metal tube 47. The inclination angle of the first protruding portions 55 a with respect to the longitudinal direction is equal to the inclination angle of the second protruding portions 55 b with respect to the longitudinal direction.
As shown in FIGS. 26B and 26C, the end surfaces of the first protruding portion 55 a and second protruding portion 55 b abut on each other in a contact region T.
The metal tube 47 according to the ninth embodiment is formed in the following manner. First, as shown in FIG. 26A, the plurality of protruding portions 55 are formed with a predetermined spacing on almost the entire surface of the metal sheet M. These protruding portions 55 include a plurality of first protruding portions 55 a formed in a region on one side (upper side in FIG. 26A) on a central line B3 positioned as a boundary close to the center of the metal tube M in the width direction W and a plurality of second protruding portions 55 b formed in a region on the other side (lower side in FIG. 26A). In the metal sheet M, the first protruding portions 55 a and second protruding portions 55 b are formed in the same direction at the same inclination angle.
Where the metal sheet M is folded along the central line B3, the first protruding portions 55 a and the second protruding portions 55 b are disposed in a mutual arrangement such as to cross each other, as shown in FIG. 26B, and the end side El on one side and the end side E2 on the other side in the width direction W of the metal sheet M come close to each other. The metal tube 47 is obtained by joining the end sides E1, E2 together by an appropriate method, for example, welding.
When the abovementioned metal sheet M is folded, the opposing positions of the corresponding first protruding portions 55 a and second protruding portions 55 b are somewhat displaced as shown in FIGS. 27A and 27B. Even in such cases, since the first protruding portions 55 a and second protruding portions 55 b are disposed to cross each other, the contact surface area of the mutual contact region T assumes an almost same value, provided that the displacements in various directions take place within a range in which the crossed state of the first protruding portions 55 a and second protruding portions 55 b is maintained. As a result, even where a certain displacement occurs when the metal tube 47 is formed, the effect of inhibiting the deformation in the thickness direction of the metal tube 47 can be prevented from reducing.
Further, when the heat exchanger 21 is fabricated by stacking the metal tube 47 and the multiple- hole metal tubes 45, 49 and then the heat exchanger 21 is spirally bent, for example as shown in FIG. 2, even if the relative positions of the opposing first protruding portions 55 a and second protruding portions 55 b are somewhat displaced, the mutual contact surface area can be prevented from decreasing. Thus, even if a certain displacement occurs, the contact surface area of the contact region T assumes an almost same value. Therefore, the variation in of the effect of inhibiting the deformation in the thickness direction can be inhibited over the entire metal tube 47. As a result, such inconveniences as the occurrence of an extremely large deformation in part of the metal tube 47 can be inhibited. Therefore, the variation in the degree of pressure loss among the zones of the metal tube 47 can be inhibited.
Thus, as mentioned hereinabove, portions where the elongated first protruding portions 55 a and second protruding portions 55 b are in contact with each other function to inhibit deformation in the thickness direction. Meanwhile, portions where the elongated first protruding portions 55 a and second protruding portions 55 b are not in contact with each other function as obstacles that create appropriate turbulence in the fluid in the fluid flow channel 53. Where the fluid becomes appropriately turbulent, heat transfer between the fluid and the metal tube 47 is enhanced. Therefore, heat exchange efficiency of the heat exchanger 21 can be increased.
Further, in the ninth embodiment, the first protruding portions 55 a and second protruding portions 55 b provided in the metal sheet M may be formed at the same inclination angle with respect to the same direction. Therefore, the design is simple. Moreover, in the ninth embodiment, the size of the first protruding portions 55 a or second protruding portions 55 b in the width direction W can be reduced by comparison with the case in which either the first protruding portions 55 a or the second protruding portions 55 b are disposed parallel to the width direction W of the metal tube 47. As a result, the increase in resistance encountered by the fluid flowing inside the metal tube 47 can be inhibited.
(Other Manufacturing Methods)
In the heat exchanger 21 according to the above-described first to ninth embodiments, the metal tube 47 and the multiple- hole metal tubes 45, 49 can be joined by using not only the above-described method based on resistance welding, but also other methods such as brazing and soldering. Brazing as referred to herein is a joining method performed using a braze having a melting point equal to or higher than 450° C. and soldering is a joining method performed using a solder having a melting point of less than 450° C.
With the joining method using brazing, a braze is disposed, for example, between the metal tube 47 and the multiple-hole metal tube 45 and between the metal tube 47 and the multiple-hole metal tube 49, and the components are heated in this state in a heating furnace or the like. As a result, the braze is melted and the metal tube 47 and the multiple- hole metal tubes 45, 49 are joined to each other.
For example, ultrasonic soldering can be used as a joining method based on soldering. With this method, a solder is disposed between the metal tube 47 and the multiple-hole metal tube 45 and between the metal tube 47 and the multiple-hole metal tube 49, an ultrasonic soldering probe is brought into contact with at least one component from among the metal tube 47, multiple-hole metal tube 45, and multiple-hole metal tube 49, and ultrasonic vibrations are applied thereto under heating. As a result, the solder is melted and the metal tube 47 and the multiple- hole metal tubes 45, 49 are joined to each other.

Summary of Embodiments

The embodiments are summarized below.
(1) The heat exchanger includes a metal tube that has a flat shape with a width greater than a thickness, a fluid flow channel formed inside thereof along a longitudinal direction, respective outer surfaces formed on one side and the other side in a thickness direction, and a support portion formed in the fluid flow channel and inhibiting deformation in the thickness direction; and a multiple-hole metal tube stacked on one side of the metal tube in the thickness direction, the multiple-hole metal tube that has a flat shape with a width greater than a thickness, a plurality of fluid flow channels formed inside thereof along the longitudinal direction, and an opposing surface disposed opposite the outer surface on the one side of the metal tube and joined by at least part thereof to the outer surface on the one side.
In such a configuration, a support portion that inhibits deformation in the thickness direction is provided in the fluid flow channel of the metal tube. Therefore, the heat exchanger can be manufactured by using resistance welding by which the flat metal tube and flat multiple-hole metal tube stacked in the thickness direction are welded, while being pressurized in the thickness direction by a pair of roller electrodes. Since the heat exchanger can thus be manufactured by resistance welding that excels in productivity, the cost can be reduced.
Further, since the support portion is provided in the fluid flow channel, the metal tube and multiple-hole metal tubes can be sufficiently pressurized in the thickness direction by the pair of roller electrodes during resistance welding. As a result, the joining surface area of the outer surfaces of the metal tube and the opposing surfaces of the multiple-hole metal tubes opposite thereto can be increased and therefore a heat exchanger with excellent heat exchange efficiency can be obtained.
Further, with such a configuration, since the metal tube has a support portion in the fluid flow channel, deformation of the metal tube can be inhibited even in a long-term use of the heat exchanger.
Moreover, with such a configuration, since the metal tube has a support portion in the fluid flow channel, for example, even when the heat exchanger is bent as shown in the below-described FIG. 2, the excess deformation of the metal tube can be inhibited. As a result, the fluid flow channel can be prevented from being excessively narrowed or closed.
(2) The support portion may have a plurality of columnar bodies arranged along the longitudinal direction of the fluid flow channel, one end of each of the columnar bodies in an axial direction may be joined to an inner surface on either side in the thickness direction of the fluid flow channel, and the other end of each of the columnar bodies in the axial direction may be disposed on an inner surface side on the other side in the thickness direction of the fluid flow channel.
In such a configuration, since a plurality of columnar bodies are arranged along the longitudinal direction of the fluid flow channel, deformation of the metal tube in the longitudinal direction can be inhibited over a long period. Furthermore, since the columnar bodies are arranged in a spot-like pattern in the longitudinal direction, the increase in resistance to the flow of fluid in the fluid flow channel that is caused by the support portion can be inhibited and the fluid can smoothly flow in the fluid flow channel. In addition, in this configuration, one end of each columnar body is joined to the inner surface of the fluid flow channel. Therefore, the columnar bodies can be prevented from tilting or tumbling even when pressurized in the thickness direction by roller electrodes during resistance welding. As a result, deformation of the fluid flow channel is inhibited and the desired flow channel can be ensured.
(3) Both ends in the axial direction of at least one of the plurality of columnar bodies may be respectively joined to the inner surface on one side and the inner surface on the other side of the fluid flow channel.
In such a configuration, since columnar bodies are provided that are joined to the inner surface on one side and the inner surface on the other side of the fluid flow channel, the rigidity of the metal tube can be further increased. As a result, deformation of the metal tube can be inhibited over a longer period.
(4) In another possible configuration, the support portion has a plurality of first columnar bodies arranged along the longitudinal direction of the fluid flow channel on an inner surface on one side in the thickness direction of the fluid flow channel and a plurality of second columnar bodies arranged along the longitudinal direction of the fluid flow channel on an inner surface on the other side in the thickness direction of the fluid flow channel; the first columnar bodies extend from the inner surface on the one side toward the inner surface on the other side; and the second columnar bodies extend from the inner surface on the other side toward the inner surface on the one side, and distal end portions thereof abut on or are disposed close to respective distal end portions of the plurality of first columnar bodies.
In such a configuration, when a pressure is applied in the thickness direction to the metal tube and multiple-hole metal tubes by a pair of roller electrodes during resistance welding, the first columnar bodies and second columnar bodies that have been abutted on each other by the distal end portions are in the abutted state and the columnar bodies that have distal end portions disposed close to each other abut on each other by the distal end portions, thereby making it possible to receive and stop the pressure in the thickness direction. As a result, deformation of the metal tubes in the thickness direction during resistance welding can be effectively inhibited. In the present configuration, a plurality of first columnar bodies and a plurality of second columnar bodies that have distal portions abutted on each other or disposed close to each other are arranged in the longitudinal direction of the fluid flow channel. Therefore, deformation of the metal tubes in the longitudinal direction can be inhibited over a long period. Furthermore, since the columnar bodies are arranged in a spot-like pattern in the longitudinal direction, the increase in resistance to the flow of fluid in the fluid flow channel that is caused by the support portion can be inhibited and the fluid can smoothly flow in the fluid flow channel.
(5) At least one of the plurality of first columnar bodies and at least one of the plurality of second columnar bodies may be joined together at the distal end portions thereof.
In such a configuration, since the first columnar bodies and second columnar bodies are provided that are joined together at the distal end portions thereof, the rigidity of the metal tubes can be further increased. As a result, deformation of the metal tubes can be inhibited over a longer period.
(6) The support portion may be a corrugated plate-like body disposed along the longitudinal direction of the fluid flow channel.
In such a configuration, since the corrugated plate-like body is disposed along the longitudinal direction, deformation of the metal tubes in the longitudinal direction can be inhibited over a long period. Further, the corrugated plate-like body acts to disperse the fluid flow. Therefore, it is possible to regulate the fluid flow and produce a flow with low turbulence. Since the rigidity of the support body itself can be increased over that in the case of the above-described columnar bodies, such a configuration is particularly advantageous when a larger pressurization force is desired to be obtained with the pair of roller electrodes.
(7) The support portion may have a plurality of protruding portions arranged along the longitudinal direction of the fluid flow channel, and each of the protruding portions may protrude from an inner surface on either side in the thickness direction of the fluid flow channel toward an inner surface on the other side in the thickness direction.
In such a configuration, since a plurality of protruding portions are arranged along the longitudinal direction of the fluid flow channel, deformation of the metal tubes can be inhibited over a long period.
(8) A size of each of the protruding portions in a width direction may be set less than the size thereof in the longitudinal direction.
In such a configuration, by reducing the size of each protrusion in the width direction, that is, the size in the direction perpendicular to the fluid flow direction, below the size in the longitudinal direction, it is possible to inhibit an excess increase in the resistance encountered by the fluid flowing in the metal tube. Further, the size of each protruding portion in the longitudinal direction may be designed as appropriate to a value required to inhibit deformation of the metal tubes in the thickness direction. As a result, the resistance encountered by the fluid can be reduced and the effect of inhibiting the deformation of the metal tube in the thickness direction can be maintained.
(9) The protruding portions are not limited to the abovementioned columnar bodies and can be formed, for example, by causing the outer surface on one side in the thickness direction to recede toward the other side or the outer surface on the other side in the thickness direction to recede toward the one side.
In such a case, the protruding portions can be formed, for example, by pressing a metal sheet. Therefore, the production is simple and cost can be reduced.
(10) The support portion may have a plurality of first protruding portions arranged along the longitudinal direction of the fluid flow channel on an inner surface on one side in the thickness direction of the fluid flow channel, and a plurality of second protruding portions arranged along the longitudinal direction of the fluid flow channel on an inner surface on the other side in the thickness direction of the fluid flow channel, the first protruding portions may protrude from the inner surface on the one side toward the inner surface on the other side, and the second protruding portions may protrude from the inner surface on the other side toward the inner surface on the one side.
With such a configuration, the plurality of the first protruding portions and the plurality of the second protruding portions are arranged along the longitudinal direction of the fluid flow channel Therefore, deformation of the metal tube in the longitudinal direction can be inhibited over a long period.
(11) Such first protruding portions and second protruding portions are not limited to the abovementioned first columnar bodies and second columnar bodies and can be formed, for example, by causing the outer surface on one side and the outer surface on the other side in the thickness direction to recede.
In the case of such a configuration, the protruding portions can be formed, for example, by pressing a metal sheet. Therefore, the production is simple and cost can be reduced.
(12) Some or all of the plurality of first protruding portions are preferably provided at positions opposite the second protruding portions in the thickness direction.
With such a configuration, where the first protruding portions and the second protruding portions disposed at positions opposite thereto abut on each other, subsequent deformation of the metal tube 47 is inhibited even when a pressure is applied in the thickness direction to the metal tube 47 during the resistance welding or bending such as described hereinabove. As a result, deformation in the thickness direction of the metal tube during resistance welding or bending can be effectively inhibited.
(13) The first protruding portions and the second protruding portions may respectively have elongated shapes in a plan view thereof, and the first protruding portions and the second protruding portions, which are facing each other in the thickness direction, may be provided so as to cross each other in a plan view thereof.
With such a configuration, even when the relative positions of the opposing first protruding portions and second protruding portions are somewhat displaced in various directions when forming the metal tube 47, bending of the heat exchanger, and the like, changes in the mutual contact surface area thereof can be inhibited. Thus, where displacements in various directions take place within a range in which the crossed state of the first protruding portions and second protruding portions is maintained, the mutual contact surface area assumes an almost same value. Therefore, even when a certain displacement occurs, the first protruding portions and second protruding portions come into contact with each other over a contact surface area of an almost same value. Therefore, the variation in the effect of inhibiting the deformation in the thickness direction decreases over the entire metal tube. As a result, when the heat exchanger is bent, a stable deformation inhibition effect can be obtained over the entire metal tube. Therefore, the variation in the degree of pressure loss among the zones of the metal tube can be inhibited.
In this configuration, elongated first protruding portions and second protruding portions are disposed to cross each other, and there are portions in which the first protruding portions and second protruding portions are in contact with each other and portions adjacent thereto in which the first protruding portions and second protruding portions are not in contact with each other. These contact-free portions function as obstacles that create appropriate turbulence in the fluid in the fluid flow channel Where the fluid becomes appropriately turbulent, heat transfer between the fluid and the metal tube is enhanced. Therefore, heat exchange efficiency of the heat exchanger can be increased.
Further, this configuration is effective when the metal tube is formed by bending a metal sheet (flat sheet) and joining together the end sides of the metal sheet. In this case, the first protruding portions and second protruding portions are formed at the metal sheet in advance, before the metal sheet is bent. Even when the opposing positions of the opposing first protruding portions and second protruding portions somewhat shift during bending, where the displacement in various directions takes place within the range in which the crossing state of the first protruding portions and second protruding portions is maintained, the mutual contact surface area assumes an almost same value. As a result, decrease in the deformation inhibition effect in the thickness direction of the metal tube can be suppressed even if the displacement occurs when the metal tube is formed.
(14) It is preferred that a longitudinal direction of the first protruding portions be inclined to one side in a width direction of the metal tube with respect to the longitudinal direction of the metal tube; a longitudinal direction of the second protruding portions be inclined to the other side in the width direction with respect to the longitudinal direction of the metal tube; and an inclination angle of the first protruding portions with respect to the longitudinal direction be equal to an inclination angle of the second protruding portions with respect to the longitudinal direction.
In this configuration, the first protruding portions and the second protruding portions provided at the metal tube may be formed in the same direction and at the same inclination angle. Therefore, the design and processing are simple. Furthermore, in this configuration, the size component of the first protruding portions 55 a or the second protruding portions 55 b in the width direction of the metal tube can be reduced by comparison with that in the case in which either of the first protruding portions and second protruding portions are disposed parallel to the width direction of the metal tube. As a result, an excess increase in the resistance encountered by the fluid flowing in the metal tube can be inhibited.
(15) The first protruding portions and the second protruding portions may respectively have elongated shapes in a plan view thereof, and a longitudinal direction of the first protruding portions and the second protruding portions, which are facing each other in the thickness direction, may be parallel to the longitudinal direction of the metal tube.
In such a configuration, the effect of ensuring the contact surface area of the opposing first protruding portions and second protruding portions is especially advantageous when the heat exchanger is bent spirally or in a zigzag shape. Thus, when the heat exchanger is bent as mentioned above, in the curved portion of the metal tube, the elongation of material on the radially outer side is less than the elongation of material on the radially inner side. Therefore, relative positions of the first protruding portions and second protruding portions are easily displaced. Accordingly, in this configuration, the longitudinal direction of the first protruding portions and the second protruding portions is along the longitudinal direction of the metal tube and therefore excellent effect of maintaining the mutual contact state is demonstrated even when the relative positions are displaced in the longitudinal direction by the abovementioned bending. As a result, bending with a small curvature radius is possible.
(16) It is preferred that the plurality of first protruding portions be arranged so that three or more rows thereof extending in the longitudinal direction are formed, and in a row positioned in a central portion in the width direction from among these rows, the first protruding portions be provided at positions opposite the second protruding portions in the thickness direction.
With such a configuration, since the first protruding portions and the second protruding portions are opposite each other in the central portion in the width direction, deformation of the metal tube can be inhibited with good balance in the central portion in the width direction. Further, “the row positioned in the central portion in the width direction” as referred to herein means the row closest to the center of the metal tube in the width direction. Therefore, when the number of the plurality of rows (the aforementioned three or more rows) extending in the longitudinal direction is an even number, “the row positioned in the central portion in the width direction” can mean two rows.
(17) It is preferred that in rows positioned at both sides of the row positioned in the central portion in the width direction, the first protruding portions be provided at positions displaced in the longitudinal direction with respect to the second protruding portions.
With such a configuration, as mentioned hereinabove, in the central portion in the width direction, the first protruding portions and the second protruding portions are disposed opposite each other, whereas in the rows positioned at both sides, the first protruding portions are provided at positions displaced in the longitudinal direction with respect to the second protruding portions. Therefore, deformation of the metal tube in the thickness direction in the central portion in the width direction can be inhibited with good balance, narrowing of the fluid flow channel at both sides in the width direction is inhibited, and a smooth flow of the fluid can be realized. Further, since the first protruding portions and the second first protruding portions are provided at both sides in the width direction, when an unexpectedly high pressure is applied in the thickness direction, the distal end portions of the first protruding portions or the distal end portions of the second protruding portions abut on an inner surface or an inner surface of the metal tube, thereby making it possible to inhibit subsequent deformation of the metal tube.
(18) It is preferred that the plurality of first protruding portions be arranged, as described hereinabove, so that three or more rows thereof extending in the longitudinal direction are formed, and also that the first protruding portions be arranged so that a plurality of rows thereof extending in a inclination direction inclined with respect to the longitudinal direction are formed; the second protruding portions be also arranged so that a plurality of rows thereof extending in the inclination direction are formed; and the rows of the first protruding portions in the inclination direction and the rows of the second protruding portions in the inclination direction be disposed alternately along the longitudinal direction.
Where such a configuration is used, steps (protruding portions) in the thickness direction can be disposed continuously with an inclination against the longitudinal direction and the steps (first protruding portions) on one side and the steps (second protruding portions) on the other side in the thickness direction can be disposed alternately. Therefore pulsations can be effectively generated in the flow of fluid in the fluid flow channel As a result, the drift in the fluid flow channel can be inhibited and the development of turbulent flow of the fluid in the fluid flow channel can be enhanced, thereby increasing the efficiency of heat exchange.
(19) The configuration is preferred in which the fluid flow channel includes a first fluid flow channel and a second fluid flow channel provided parallel to each other in the width direction and extending in the longitudinal direction; the first fluid flow channel is formed by folding a metal sheet at a position along the longitudinal direction and bending the metal sheet into a tubular shape so that one end side in the width direction of the metal sheet abuts on a surface on one side of the metal sheet, and the one end side is joined to the one surface along the longitudinal direction; the second fluid flow channel is formed by folding the metal sheet at another position along the longitudinal direction and bending the metal sheet into a tubular shape so that another end side in the width direction of the metal sheet abuts on the one surface at a position adjacent to the one end side, and the other end side is joined to the one surface along the longitudinal direction; and the support portion is constituted by parts of the metal sheet, each part extending from the one end side and the other end side in the thickness direction or a direction inclined from the thickness direction.
With such a configuration, a metal with a substantially B-like cross section can be obtained by forming a metal sheet in the above-described manner. In such a metal tube, the support portion extending along the longitudinal direction can be formed and a pair of fluid flow channel can be formed by forming the metal sheet in the above-described manner. Therefore, the metal tube is manufactured in a simple manner. Further, since the support portion of the metal tube extends continuously along the longitudinal direction, an excellent effect of inhibiting deformation in the thickness direction is demonstrated.
(20) In the heat exchanger, the multiple-hole metal tube may be a first multiple-hole metal tube and the heat exchanger may further include a second multiple-hole metal tube stacked on the other side of the metal tube in the thickness direction, the second multiple-hole metal tube that has a flat shape with a width greater than a thickness, a plurality of fluid flow channels formed inside thereof along the longitudinal direction, and an opposing surface that is disposed opposite an outer surface on the other side of the metal tube and joined by at least part thereof to the outer surface on the other side.
In such a configuration, multiple-hole metal tubes are stacked on both sides in the thickness direction of the metal tube. Therefore, the heat exchange surface area can be increased and the efficiency of heat exchange between the coolant and the fluid can be further increased.
(21) It is preferred that substantially the entire opposing surfaces be joined to the outer surfaces.
In such a configuration, substantially entire opposing regions of the metal tube and multiple-hole metal tubes are joined to each other. Therefore, the efficiency of heat exchange between the coolant and the fluid can be further increased.
(22) For example, the heat exchanger may be configured by spirally winding so that one end in the longitudinal direction is disposed inside and another end in the longitudinal direction is disposed outside.
With such a configuration, because the heat exchanger is spirally wound, dead space can be reduced and the heat exchanged can be reduced in size. Further, since the support portion is provided in the fluid flow channel of the metal tube, the fluid flow channel can be prevented from decreasing is size or closing due to deformation of the metal tube occurring during bending from a linear shape to the spiral shape and the decrease in heat exchange efficiency can be inhibited.

Other Embodiments

The present invention is not limited to the abovementioned embodiments and can be variously changed or modified without departing from the essence thereof. For example, in the fourth embodiment, an exemplary configuration is explained in which the first protruding portions 55 a protrude from one inner surface 57, the second protruding portions 55 b protrude from the other inner surface 59, and some of the first protruding portions 55 a and some of the second protruding portions 55 b are disposed at mutually opposing positions, but such a configuration is not limiting.
For example, in Variation Example 1 shown in FIG. 15, the first protruding portions 55 a protrude from one inner surface 57, the second protruding portions protrude from the other inner surface 59, and these first protruding portions 55 a and second protruding portions 55 b are disposed alternately in the longitudinal direction and thickness direction, instead of being disposed at the mutually opposing positions. With such a configuration, the distal end portions of the first protruding portions 55 a extend close to the other inner surface 59, and the distal end portions of the second protruding portions 55 b extend close to the one inner surface 57. As a result, when a pressure is applied to the metal tube 47 in the thickness direction, the first protruding portions 55 a abut on the other surface 59, and the second protruding portions 55 b abut on the one inner surface 57 and therefore subsequent deformation of the metal tube 47 is inhibited. In the Variation Example 1, the first protruding portions 55 a and the second protruding portions 55 b are formed by pressing.
Further, for example, in Variation Example 2 shown in FIG. 16, the protruding portions 55 may protrude only from one inner surface 57. In such a configuration, the distal end portions of the protruding portions 55 extend to the vicinity of the other inner surface 59. As a result, the protruding portions 55 abut on the other inner surface 59 and subsequent deformation of the metal tube 47 is inhibited even when a pressure is applied to the metal tube 47 in the thickness direction. In this Variation Example 2 the protruding portions 55 are formed by pressing.
Further, in the abovementioned embodiments, a heat exchanger that is spirally bent is explained by way of example, but the heat exchanger in accordance with the present invention is not limited to the spiral configuration and can be used in a linear configuration or can be processed into a variety of other shapes. A plurality of spiral heat exchangers such as shown in FIG. 1 may be stacked.
Further, in the abovementioned embodiments, the case of heat exchange between water and a coolant is explained by way of example, but the heat exchanger in accordance with the present invention may be used for heat exchange between coolants or for heat exchange between the coolant and another fluid.
Further, in the abovementioned embodiments, the case in which the support member is a columnar body or a corrugated plate-like body is explained by way of example, but a variety of other configurations such as a configuration in which a plurality of plate-like bodies are arranged in a spot-like pattern in the fluid flow channel of the metal tube substantially parallel to the thickness direction thereof and a configuration in which a plurality of spherical bodies are disposed in the fluid flow channel can be also used. Further, in addition to the case in which the support member is a corrugated plate-like body in the form of an S-like curve, as in the abovementioned embodiments, the support member can be in the form of a corrugated plate-like body composed by angular protrusions and depressions.
Further, in the abovementioned first embodiment and second embodiment, the configuration in which the columnar bodies are arranged in three rows is explained by way of example, but the columnar bodies in accordance with the present invention may be disposed in one row, in two rows, or in a plurality of rows (four or more rows).
Further, in the abovementioned embodiments, the case is explained in which the first embodiment, second embodiment, and third embodiment are implemented individually, but two or more implementation modes thereof may be combined.
Further, in the abovementioned embodiments, a three-layer configuration is explained that is obtained by stacking the first multiple-hole metal tube, metal tube, and second multiple-hole metal tube in the order of description, but a two-layer configuration including only one multiple-hole metal tube and the metal tube or a configuration including four or more layers may be also used.
Further, in the abovementioned embodiments, the case in which each metal tube has a flat shape having a substantially quadrangular cross section is explained by way of example, but another flat shape, for example, such that has a cross section with a curved side portion in the width direction, may be also used.
Further, in the abovementioned embodiments, the case is explained in which the metal tube and the multiple-hole metal tube are joined by a melt joining method by which the outer surface of the metal tube and the opposing surface of the multiple-hole metal tube are locally fused together in the vicinity of the boundary thereof, but in accordance with the present invention, the joining may be also performed by resistance welding in a state in which a fusion metal with a melting point lower than those of the metal tube and the multiple-hole metal tube is disposed between the outer surface of the metal tube and the opposing surface of the multiple-hole metal tube.
Further, in the abovementioned embodiments, the case in which the roller electrode is fixed and welding is performed by moving the metal tube which is the object of welding is explained by way of example, but the resistance welding may be also performed by fixing the metal tube and moving the roller electrode.
Further, in the abovementioned embodiments, the case in which the heat exchanger is used in a heat pump type hot water supply apparatus is explained by way of example, but the heat exchanger in accordance with the present invention can be also used for other applications such as air conditioners.
Further, in the abovementioned fourth embodiment, the case in which the metal sheet is pressed to form the protruding portions is explained by way of example, but the protruding portions may be also formed by joining another member to the metal sheet, for example, by welding.
Further, in the abovementioned fourth embodiment, the configuration in which the plurality of protruding portions are arranged in a spot-like pattern is explained by way of example, but the protruding portions may also have a continuous ridge-like shape along the longitudinal direction.
Further, in the abovementioned fourth embodiment, the case is explained in which some of the plurality of first protruding portions are provided at positions opposite the second protruding portions in the thickness direction, but all of the plurality of first protruding portions may be provided at positions opposite the second protruding portions in the thickness direction.
Further, in the abovementioned fourth embodiment, the configuration is explained in which the first protruding portions and second protruding portions are arranged in five rows extending in the longitudinal direction, but the first protruding portions and second protruding portions may be disposed in different rows.
Further, in the abovementioned embodiments, the case is explained in which the protruding portions with the size in the width direction such as shown, for example, in FIG. 17B and FIG. 19, less than the size in the longitudinal direction are provided on one inner surface and other inner surface in the thickness direction of the metal tube 47, but such protruding portions may be provided only on either inner surface in the thickness direction of the metal tube 47.
Further, in the abovementioned ninth embodiment, the case is explained in which the inclination angle of the first protruding portions 55 a with respect to the longitudinal direction L is equal to that of the second protruding portions 55 b, but such configuration is not limiting and the inclination angle of the first protruding portions 55 a may be different from the inclination angle of the second protruding portions 55 b. Further, a configuration may be used in which the first protruding portions 55 a are disposed along the longitudinal direction L and the second protruding portions 55 b are disposed along the width direction.

EXPLANATION OF REFERENCE NUMERALS

11 hot water supply apparatus
13 coolant circuit
15 tank
17 hot water storage circuit
19 compressor
21 heat exchanger
23 expansion valve
25 evaporator
45 first multiple-hole metal tube
47 metal tube
49 second multiple-hole metal tube
51 coolant flow channel
53 fluid flow channel
55 support member (support portion)
55 a first columnar body
55 b second columnar body
F flow direction of fluid

Claims

1. A heat exchanger comprising:

a metal tube that has a flat shape with a width greater than a thickness, a fluid flow channel formed inside thereof along a longitudinal direction, respective outer surfaces formed on one side and the other side in a thickness direction, and a support portion formed in the fluid flow channel and inhibiting deformation in the thickness direction; and

a multiple-hole metal tube stacked on one side of the metal tube in the thickness direction, the multiple-hole metal tube that has a flat shape with a width greater than a thickness, a plurality of fluid flow channels formed inside thereof along the longitudinal direction, and an opposing surface disposed opposite the outer surface on said one side of the metal tube and joined by at least part thereof to the outer surface on said one side.

2. The heat exchanger according to claim 1, wherein

the support portion has a plurality of columnar bodies arranged along the longitudinal direction of the fluid flow channel, one end of each of the columnar bodies in an axial direction is joined to an inner surface on either side in the thickness direction of the fluid flow channel, and the other end of each of the columnar bodies in the axial direction is disposed on an inner surface side on the other side in the thickness direction of the fluid flow channel.

3. The heat exchanger according to claim 2, wherein

both ends in the axial direction of at least one of the plurality of columnar bodies are respectively joined to the inner surface on one side and the inner surface on the other side of the fluid flow channel.

4. The heat exchanger according to claim 1, wherein

the support portion has a plurality of first columnar bodies arranged along the longitudinal direction of the fluid flow channel on an inner surface on one side in the thickness direction of the fluid flow channel and a plurality of second columnar bodies arranged along the longitudinal direction of the fluid flow channel on an inner surface on the other side in the thickness direction of the fluid flow channel,

the first columnar bodies extend from the inner surface on said one side toward the inner surface on said other side, and

the second columnar bodies extend from the inner surface on said other side toward the inner surface on said one side, and distal end portions thereof abut on or are disposed close to respective distal end portions of the plurality of first columnar bodies.

5. The heat exchanger according to claim 4, wherein

at least one of the plurality of first columnar bodies and at least one of the plurality of second columnar bodies are joined together at the distal end portions thereof

6. The heat exchanger according to claim 1, wherein

the support portion is a corrugated plate-like body disposed along the longitudinal direction of the fluid flow channel.

7. The heat exchanger according to claim 1, wherein

the support portion has a plurality of protruding portions arranged along the longitudinal direction of the fluid flow channel, and each of the protruding portions protrudes from an inner surface on either side in the thickness direction of the fluid flow channel toward an inner surface on the other side in the thickness direction.

8. The heat exchanger according to claim 7, wherein

a size of each of the protruding portions in a width direction is less than a size thereof in said longitudinal direction.

9. The heat exchanger according to claim 7, wherein

the protruding portions are formed by causing the outer surfaces on one side and other side in the thickness direction to recede toward said other side or said one side.

10. The heat exchanger according to claim 1, wherein

the support portion has a plurality of first protruding portions arranged along the longitudinal direction of the fluid flow channel on an inner surface on one side in the thickness direction of the fluid flow channel, and a plurality of second protruding portions arranged along the longitudinal direction of the fluid flow channel on an inner surface on the other side in the thickness direction of the fluid flow channel, and

the first protruding portions protrude from the inner surface on said one side toward the inner surface on said other side, and the second protruding portions protrude from the inner surface on said other side toward the inner surface on said one side.

11. The heat exchanger according to claim 10, wherein

the first protruding portions are formed by causing the outer surface on one side in the thickness direction to recede toward said other side, and the second protruding portions are formed by causing the outer surface on said other side in the thickness direction to recede toward said one side.

12. The heat exchanger according to claim 10, wherein

some or all of the plurality of first protruding portions are provided at positions opposite the second protruding portions in the thickness direction.

13. The heat exchanger according to claim 12, wherein

the first protruding portions and the second protruding portions respectively have elongated shapes in a plan view thereof, and

the first protruding portions and the second protruding portions, which are facing each other in the thickness direction, are provided so as to cross each other in a plan view thereof.

14. The heat exchanger according to claim 13, wherein

a longitudinal direction of the first protruding portions is inclined to one side in a width direction of the metal tube with respect to the longitudinal direction of the metal tube,

a longitudinal direction of the second protruding portions is inclined to the other side in the width direction with respect to the longitudinal direction of the metal tube, and

an inclination angle of the first protruding portions with respect to the longitudinal direction is equal to an inclination angle of the second protruding portions with respect to the longitudinal direction.

15. The heat exchanger according to claim 12, wherein

a longitudinal direction of the first protruding portions and the second protruding portions, which are facing each other in the thickness direction, is parallel to the longitudinal direction of the metal tube.

16. The heat exchanger according to claim 12, wherein

the plurality of first protruding portions are arranged so that three or more rows thereof extending in the longitudinal direction are formed, and in a row positioned in a central portion in the width direction from among these rows, the first protruding portions are provided at positions opposite the second protruding portions in the thickness direction.

17. The heat exchanger according to claim 16, wherein in rows positioned at both sides of the row positioned in the central portion in the width direction, the first protruding portions are provided at positions displaced in the longitudinal direction with respect to the second protruding portions.

18. The heat exchanger according to claim 17, wherein

the plurality of first protruding portions are arranged so that a plurality of rows thereof extending in a inclination direction inclined with respect to the longitudinal direction are formed,

the plurality of second protruding portions are arranged so that a plurality of rows thereof extending in the inclination direction are formed, and

the rows of the first protruding portions in the inclination direction and the rows of the second protruding portions in the inclination direction are disposed alternately along the longitudinal direction.

19. The heat exchanger according to claim 1, wherein

the fluid flow channel includes a first fluid flow channel and a second fluid flow channel provided parallel to each other in the width direction and extending in the longitudinal direction,

the first fluid flow channel is formed by folding a metal sheet at a position along the longitudinal direction and bending the metal sheet into a tubular shape so that one end side in the width direction of the metal sheet abuts on a surface on one side of the metal sheet, and said one end side is joined to said one surface along the longitudinal direction,

the second fluid flow channel is formed by folding the metal sheet at another position along the longitudinal direction and bending the metal sheet into a tubular shape so that another end side in the width direction of the metal sheet abuts on said one surface at a position adjacent to said one end side, and the other end side is joined to said one surface along the longitudinal direction, and

the support portion is constituted by parts of the metal sheet, each part extending from said one end side and said other end side in the thickness direction or a direction inclined from the thickness direction.

20. The heat exchanger according to claim 1, wherein the multiple-hole metal tube is a first multiple-hole metal tube, and

the heat exchanger further comprises a second multiple-hole metal tube stacked on said other side of the metal tube in the thickness direction, the second multiple-hole metal tube that has a flat shape with a width greater than a thickness, a plurality of fluid flow channels formed inside thereof along the longitudinal direction, and an opposing surface that is disposed opposite an outer surface on said other side of the metal tube and joined by at least part thereof to the outer surface on said other side.

21. The heat exchanger according to claim 1, wherein substantially the entire opposing surfaces are joined to the outer surfaces.

22. The heat exchanger according to claim 1, which is spirally wound so that one end in the longitudinal direction is disposed inside and another end in the longitudinal direction is disposed outside.

23. A heat pump type hot water supply apparatus comprising:

a coolant circuit having a compressor, the heat exchanger according to claim 1, a pressure reducing mechanism, an evaporator, and a pipe for connecting these elements; and

a hot water storage circuit having a tank storing water, a water inlet pipe for introducing water from the tank into the fluid flow channel of the heat exchanger, and a hot water outlet pipe for returning water heated by the heat exchanger into the tank.