JPH028691A - Method for manufacturing heat exchange equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Object of the invention] [Industrial field of application] The present invention relates to a heat exchange device and a method for manufacturing the same, and in particular,
The present invention relates to a heat exchange device that uses a composite structure in which a porous material such as foamed aluminum and a hollow metal object are integrally formed. Possible applications include, for example, exhaust heat recovery equipment for automobiles and heat dissipation equipment for high-temperature fluid used in factories.

[Prior art] A heat exchange device using foamed aluminum was disclosed in Japanese Patent Application Laid-Open No. 1986-
It is disclosed in Japanese Patent No. 52198. This heat exchange inspection device is made of aluminum foam that has been formed into a predetermined shape in advance, through which heat transfer tubes are passed, and a large number of through holes for ventilation are bored therein. In this type of heat exchange device, the ventilation through holes have a fin shape, which provides a large heat transfer area, and the fluid passing through the holes becomes turbulent due to the foamed pores, resulting in high heat transfer efficiency. It also has the advantage of being easy to manufacture.

[Problems to be Solved by the Invention] By the way, in this type of heat exchange device, it is known that the heat exchange performance is greatly influenced by the quality of heat transfer at the joint between the heat exchanger tube and foamed aluminum. .

However, in this type of conventional heat exchange device,
Heat transfer between the heat exchanger tube and aluminum foam is not sufficient.

Conventionally, the following methods have been used to make composite structures of foamed aluminum and pipes.

(a) Using a gun drill, etc., cut an insertion hole of a size corresponding to the outside diameter of the pipe to be integrated into a foamed product formed by primary forming a product made by adding a foaming agent to molten metal such as aluminum and casting it. The hole is drilled with a tool, and then a pipe is press-fitted into the insertion hole to integrate them.

(b) A preheated pipe is set in the 1M mold in advance, and inside the SB mold, the foam molded product that is being manufactured, that is, the added foaming agent starts foaming and air bubbles are formed inside. Inject certain molten metals and allow them to cool and solidify.

However, no matter which method (a) or (b) is used, the boundary between the metal foam molded body and the pipe (
A void is formed at the joint (joint location), and a sufficient joint condition cannot be obtained.

FIG. 5a shows an enlarged cross-section of the joint portion between the pipe 41 and the porous material 42 of the composite structure obtained by the method of (a). Referring to FIG. 5a, it can be seen that in this example, the pipe 41 and the porous material 42 are in contact through a number of cut cells in the porous material 42. In other words, the higher the porosity of the porous material, the smaller the contact area between the two.

FIG. 5b shows an enlarged cross-section of the joint portion between the pipe 43 and the porous material 44 of the composite structure obtained by the method of (b). Referring to FIG. 5b, in this example, the surface of the porous material 44 in the portion facing the pipe 43 is wavy, that is, has an uneven shape, and an air layer 45 is formed at the boundary between the pipe 43 and the porous material 44. I know it exists. Therefore, the contact area between the pipe 43 and the porous material 44 is small. This kind of air J? J45 is formed because the viscosity of the molten metal poured into the mold increases and its flow deteriorates.

In any case, in a composite structure of a porous material and a pipe made by a conventional method, the contact area between the pipe and the porous material is small. Therefore, the thermal resistance between the two is relatively large. For this reason, in conventional heat exchange devices composed of aluminum foam and heat transfer tubes, it is inevitable that the heat exchange performance will be low.

An object of the present invention is to provide a heat exchange device with high heat exchange performance using a porous material such as aluminum foam, and a method for manufacturing the same.

[Structure of the Invention] [Means for Solving the Problems] In order to achieve the above object, the present invention provides a metal porous material whose thermal expansion coefficient is equal to or lower than that of the metal porous material. and a hollow metal member penetrating the interior of the metal porous material; and a composite structure in which the two are integrally formed in close contact with no air layer at the boundary between the two; A heat exchange device is constructed by forming a plurality of single holes in the heat exchanger.

The above-mentioned composite structure in which a metal porous material and a hollow metal member are integrally formed in close contact with each other is a mold containing molten metal such as aluminum or aluminum alloy, a thickening agent such as calcium, and titanium hydride. The foamed material is added, the viscosity is adjusted and stirred, and the bubbles of the foamed material in the molten metal expand and the bubbles grow before the independent cells form a thin film-like cell M structure. It can be obtained by inserting a hollow metal member having the same or lower coefficient of thermal expansion into the mold, and cooling and solidifying the molten metal in the mold after foaming is completed.

[Function] In the heat exchange device configured as described above, the ventilation through holes have a fin shape, and a large heat transfer area is obtained, and the fluid passing through the holes is irregularly combed by the foamed pores. High heat transfer efficiency can be obtained. Moreover, the porous metal material and the hollow metal member are in close contact with each other.

Since their contact area is large, the thermal resistance between them is sufficiently small, and therefore high heat exchange performance can be obtained.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[Example] FIG. 1 and FIG. 3 respectively show a longitudinal sectional view and a perspective view of a heat exchange device embodying the present invention, and FIG. 2 shows a sectional view taken along the line ■--■ in FIG. 1. This will be explained with reference to each episode. The main body 10 of the heat exchange device is a composite structure formed integrally with a cylindrical aluminum foam 11 and an aluminum pipe 12 placed in the center.The foam aluminum 11 will be described later. It is formed by foaming molten aluminum, and as shown in FIG. 2, it has numerous small air bubbles 11a over its entire area.

As shown in FIG. 3, a large number of through holes 13 are bored in the aluminum foam 11 of the main body IO in the same direction as the pipe 12. The entire portion of foamed aluminum 11 is covered with a cover 14. Channels 14a and 14b are formed in the cover 14, and these channels communicate with openings of a large number of through holes formed in the aluminum foam 11.

Therefore, if fluid is allowed to flow in from one of the channels formed in the cover 14, the fluid will flow through the through holes 13 of the aluminum foam.
and flows out to the other channel. At this time, if there is a temperature difference between the fluid and foamed aluminum 11, heat exchange occurs between them. Also, when the fluid is passed through the pipe 12,
Since the wall surface of the pipe 12 is in contact with the foamed aluminum 11, even if there is a temperature difference between the fluid and the foamed aluminum 11, heat exchange occurs between them.

That is, when fluid (1) is passed through the pipe 12 and fluid (2) is passed through the flow path formed in the cover 14, heat exchange occurs between the fluid (1) and the fluid (2).

Flanges 15 and 16 are provided at both ends of the pipe 12, respectively.
is fixed, and flanges 17 and 18 are formed at both ends of the flow path of the cover 14, respectively.

These flanges are used to fix the heat exchange device itself and to connect the flow channels with external pipes.

In the heat exchange device shown here, the wall surface around the through hole 13 has a fin shape and has a very large surface area, so the heat transfer efficiency between the fluid (2) and the aluminum foam 11 is very high. . Further, the heat transfer efficiency between the fluid (1) and the foamed aluminum 11 is determined depending on the contact area of the contact portion between the pipe 12 and the foamed aluminum 11. Foamed aluminum 1 used in this example
In the composite structure of pipe 1 and pipe 12, the contact area is very large. Therefore, the heat conversion efficiency between fluid (1) and fluid (2) is very good.

Composite structure of aluminum foam 11 and pipe 12 @
The method for creating this will be explained below.

FIG. 6a schematically shows an apparatus configuration for manufacturing a composite structure. This will be explained with reference to FIG. 6a. Mold M
The mold case 6 is equipped with a lower lid 3 at the bottom in which the lower end of the pipe 1 is embedded and a concave holding hole 2 is formed, and an upper lid 5 at the top in which a through hole 4 through which the pipe 1 passes is formed. We are prepared. The mold M is arranged so that its bottom part fits inside the bottom plate 7.

Inside the mold M, molten metal such as aluminum or aluminum alloy and a caking agent such as calcium are placed. After that, the melting point temperature of the molten metal (for aluminum, 700~
720° C.) to sufficiently melt the contents, stir using a stirrer (not shown), and adjust the amount of caking agent added so that the molten metal has a predetermined viscosity. After the desired viscosity is achieved, a blowing agent such as titanium hydride is added.

Further stir the contents of the mold. This causes the added foaming agent to start foaming.

At the stage when the blowing agent expands and bubbles begin to grow,
Pipe 1 preheated at a temperature of 0 to 500°C is placed in the upper M
5 through the through hole 4, and the lower end is fixed in the holding hole 2 of the lower lid 3. A sealing material (same material as pipe 1 or material with a higher melting point than pipe 1) 8 is attached to the lower end of this pipe 1.
is fitted.

After a while, the foaming of the added foaming agent is completed, the bubbles grow sufficiently, and as a result, the molten metal is produced as foamed metal. After that, by cooling or other means,
As the contents of mold M cool, the molten metal solidifies. When the mold M is dismantled after the molten metal has solidified, a composite structure in which the foamed metal (aluminum) 9 and the pipe 1 are integrated as shown in the figure is obtained.

In the example of FIG. 6a, a composite structure is obtained in which only one end of the pipe 1 protrudes from the foamed metal 9. A schematic diagram of an apparatus for obtaining a composite structure in which both ends of the pipe protrude from the foamed metal is shown in FIG. 6b. Referring to FIG. 6b, in this example, a plurality of supporting legs 3a are formed at the lower end of the lower end L3 so that it has a height sufficient to allow one end tb of the pipe 1 to protrude. Further, the holding hole 2 is formed to a size that allows the pipe 1 to be inserted therethrough. The rest of the structure is the same as that in FIG. 6a.

In the device shown in FIG. 6b, a composite structure of pipe 1 and metal foam can be obtained using the same method and conditions as in the device shown in FIG. 6a. In the example shown in FIG. 6a, the lower end of the pipe 1 is filled with a sealing material 8 to prevent the inflow of the foamed metal, but in the example shown in FIG. 6b, the lower end of the pipe 1
is disposed through the holding hole 2 of the lower lid 3, so molten metal will not flow in from the end 1b of the pipe 1, and no sealing material is required.

An example of specific conditions when actually manufacturing a composite structure is shown below.

Molten metal: 99.7% pure aluminum thickener.
... Calcium 2.0% by weight Foaming agent ... Titanium hydride 2.0% by weight Sealing material (8) ... Aluminum pipe (1) ... Aluminum (AOII-T5) 5
0+smφ Wall thickness: 1.2mm Material of foaming mold component...SS41 Size of composite slide structure...Diameter: 250mm Height: 23
0mm That is, aluminum with a purity of 99.7% was placed in a mold M, the entire mold M was heated to 700°C with a heater to melt the aluminum, and then 2.0% by weight of Calcilla 11 was added as a thickener. The mixture was stirred and thickened. Subsequently, after adjusting the viscosity of the molten metal, while maintaining the temperature of the molten metal at 700°C, 2.0% by weight of titanium hydride powder was added as a blowing agent.
Add and stir.

A preheated upper lid 5 was attached. Furthermore, when the foaming agent starts foaming inside the mold M and the bubbles in the molten aluminum expand and grow, the aluminum pipe l is passed from the through hole 4 of the upper lid 5 to the holding hole 2 of the lower M3 at its lower end. 1b is inserted and fixed, and the 1g mold M is heated in that state. When the foaming agent in the molten metal is completely foamed and the bubbles become a uniform thin film-like cell structure, the mold M is heated. was stopped and cooled to room temperature to solidify the molten metal. After solidification, the mold M was dismantled to obtain a composite structure.

The cross section of the composite structure obtained by this manufacturing method is
Shown in Figures a and 4b.

The composite structure shown in FIG. 4a was obtained when the cooling period of the mold M, the stirring time after adding the thickener, etc. were adjusted to allow the bubbles in the molten aluminum to grow sufficiently. Fourth
Referring to figure a, in this composite structure, the size of the bubbles , an aluminum layer without bubbles X is formed.

The composite structure shown in FIG. 4b was obtained when the cooling period of the mold M, the stirring time after adding the thickener, etc. were adjusted to prevent the growth of air bubbles in the molten aluminum to a large extent. Referring to FIG. 4b, in this composite structure:
The size of the bubbles Y in the foamed aluminum 9 is substantially uniform throughout. At the boundary portion S between the foamed aluminum 9 and the pipe 1, an aluminum layer in which no air bubbles Y are present is formed.

In any case, in the composite structure manufactured using the above-mentioned method, the contact area between the pipe and foamed aluminum has a completely independent thin film cell structure, and there is no air layer in that area. The contact area between the aluminum and foamed aluminum is very large. Therefore, the thermal resistance between the pipe and foamed aluminum is small, and the heat transfer efficiency is very high.

[Effects] As described above, according to the present invention, a heat exchange device having a simple structure, easy to manufacture, and high heat exchange performance can be obtained.

[Brief explanation of the drawing]

1 and 3 are a longitudinal cross-sectional view and a perspective view, respectively, of a heat exchange device embodying the present invention. FIG. 2 is a sectional view taken along the line ■--■ in FIG. 1. FIGS. 4a and 4b are longitudinal cross-sectional views showing the boundary between the pipe and aluminum foam of the composite structure obtained by the method of the present invention, respectively. FIGS. 5a and 5b are longitudinal cross-sectional views showing the boundary between a pipe and aluminum foam of a composite structure obtained by a conventional method, respectively. FIGS. 6a and 6b are perspective views showing the configuration of an apparatus for manufacturing a composite structure according to an example. 1.12: Pipe (hollow metal member) 2: Concave holding hole 3: Lower lid 3a: Support leg 4: Through hole 5: Upper lid 6: Mold case 7: Bottom plate 8: Sealing material 9: Foamed metal 10: Main body (composite structure 11: Foamed aluminum (metallic porous material) 13: Through hole 14: Cover 14a, 14b: Channel 15.16, 17.18: Flange 41.43: Pipe 42, 44: Porous material 45:
Air layer M: Mold S: Boundary portions

Claims (3)

[Claims] (1) A metal porous material and a hollow metal member having a coefficient of thermal expansion equal to or lower than the metal porous material and penetrating the inside of the metal porous material are air-filled at the boundary between the two. A heat exchange device comprising: a composite structure in which these are integrally formed in close contact with each other without any layers; and a plurality of through holes formed in the composite structure. (2) The heat exchange device according to claim (1), wherein the metal porous material is a foam molded body containing aluminum. (3) Add molten metal such as aluminum or aluminum alloy, thickener such as calcium, and foaming material such as titanium hydride into the mold, adjust the viscosity and stir, and bubble the foamed material in the molten metal. During bubble growth, before the bubbles expand and independent bubbles form a thin film-like cell structure, a hollow metal member having a coefficient of thermal expansion equal to or lower than that of the molten metal is inserted into the mold, and a hollow metal member is inserted into the mold. After the foaming in the molten metal is completed, it is cooled and solidified to form a composite structure of the porous metal material and the hollow metal member, and for the composite structure, the portion of the porous metal material is A method for manufacturing a heat exchange device, the method comprising forming a plurality of through holes passing through the heat exchange device.