JP2000054159A - Heat transfer material, heat transfer body, production of heat transfer material, and production of heat transfer body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a heat transfer material which stably maintains the nuclei of cells and has satisfactory capillary action even as the wick of a heat pipe. SOLUTION: A copper-contg. metal powder is stuck to a support material which has three-dimensional network voids and can be vanished by heating. The support material is vanished and the copper-contg. metal powder is sintered to obtain an open cell type porous body of the copper-contg. metal. This porous body is subjected to oxidation treatment, in particular blackening oxidation treatment by oxidation up to the state of cupric oxide to produce the objective heat transfer material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat transfer material, a heat transfer body, and a method for manufacturing a heat transfer material.

[0002]

2. Description of the Related Art A refrigerator cools an object by utilizing a phenomenon of absorbing heat from the surroundings when a heat medium evaporates in an evaporator. The heat medium evaporated by absorbing heat from the surroundings is guided to the condenser, where it is cooled and liquefied and returned to the evaporator.

In a heat pipe, the heat medium absorbs heat from the surroundings in the evaporating section, evaporates the heat medium, and dissipates heat to the surroundings in the condensing section, condenses the evaporated heat medium, and acts on the evaporating section by capillary action of the wick. The heat is transported from the evaporator to the condenser.

[0004] In order to increase the heat transfer efficiency between the heat transfer medium and the heat medium, the heat transfer medium used in a heat exchanger involving evaporation requires a large heat transfer area and a heat transfer medium. It is said that it is effective to activate the heat transfer medium, spread the heat medium over the entire surface of the heat transfer body, and easily generate turbulence when the heat medium flows. In addition, if the wettability between the heat medium and the surface is poor, a region that does not participate in heat transfer is formed. Therefore, improving the wettability of the heat transfer material surface is also an important issue. Conventionally, the degreasing treatment, the surface activation treatment, the etching treatment and the like have been performed independently or in combination.

[0005] For this reason, a heat transfer body in which a heat transfer material made of a porous metal body is adhered to a substrate has attracted attention. Kaihei 4-
Japanese Patent Application Laid-Open No. Sho 53-43270), and a heat pipe in which a metal powder is sprinkled on a metal plate and then sintered to form a tube with the sintered layer inside (see Japanese Patent Application Laid-Open No. 53-43270). .

[0006]

The heat transfer due to the boiling of the heat medium is performed by generating bubbles on the surface of the heat transfer material and separating from the surface of the heat transfer material. The air bubbles are generated when the gas such as air adsorbed in the small dents on the surface of the heat transfer material becomes nuclei (called bubble nuclei), and the vapor of the heat medium transfers to the nuclei. Detach from the surface of the material. Then, when a bubble is released, a part of the gas remains at the bottom of the recess, so that the bubble nucleus is held and boiling continues.

[0007] It is known that if the depression is such that the heat medium penetrates into the bottom of the depression due to the surface tension, the bubble nucleus is not retained and the boiling becomes unstable. From this, in order to promote heat transfer accompanied by evaporation, a heat transfer material having a surface structure such that bubble nuclei are easily held stably is suitable.

However, in the conventional heat transfer material made of a porous metal material, the bubble nucleus may not be stably held in a place where the pore diameter is large. If the bubble nuclei are not held stably, the heat transfer material may overheat, leading to a melting accident, and its improvement has been awaited.

Regarding the wettability of the surface of the heat transfer material, the conventional surface treatment method improves the wettability, but does not sufficiently obtain the diffusion (spread) of the heat medium by the capillary force.
The wick of the heat pipe has a problem that the operation of the heat pipe becomes unstable because the heat medium is hardly refluxed to the evaporating section.

The present invention is intended to solve such a problem. According to the first, second or third aspect of the present invention, bubble nuclei are stably held in heat transfer by boiling of a heat medium. Another object of the present invention is to provide a heat transfer material and a heat transfer body having a sufficient capillary force as a wick of a heat pipe.

Further, the invention according to claim 4 or 5 provides a method for producing a heat transfer material in which bubble nuclei are stably held and which has a sufficient capillary force as a wick of a heat pipe. Aim.

A further object of the present invention is to provide a method of manufacturing such a heat transfer body, in which bubble nuclei are stably held and which has a sufficient capillary force as a wick of a heat pipe. And

[0013]

According to the first aspect of the present invention, there is provided a heat transfer material obtained by subjecting a continuous porous metal body containing copper to oxidation treatment.

As for copper, needle-like oxides are formed on the surface by the oxidation treatment, whereby fine depressions are formed on the surface. This depression is suitable for maintaining stable bubble nuclei, and stable boiling heat transfer is performed. In addition, the formation of the depression can improve the capillary force.

Copper has two oxidation states, cuprous oxide and cupric oxide. Cuprous oxide is yellow or red and cupric oxide is black. From the viewpoint of thermal conductivity, there is little difference between the two. However, since the needle-like oxide formed by the oxidation treatment becomes longer and denser, it is preferable to oxidize to the state of cupric oxide to blacken.

According to a second aspect of the present invention, there is provided the heat transfer material according to the first aspect, wherein the oxidation treatment is an oxidation treatment for producing black cupric oxide.

Further, since the heat transfer material of the present invention is porous, it is preferable that the heat transfer material is adhered to the substrate surface.

According to a third aspect of the present invention, there is provided a heat transfer body having the heat transfer material according to the first or second aspect adhered to a substrate surface.

Further, the heat transfer material of the present invention is manufactured using a holding material having three-dimensional mesh-like voids which can be eliminated by heating, from the viewpoint of manufacturing a heat transfer material having a uniform thickness and a hole diameter. Is preferred.

According to a fourth aspect of the present invention, there is provided: A step of applying a metal powder containing copper to a holding material having three-dimensional mesh-like voids which can be eliminated by heating; b. Removing the holding material, and further sintering a metal powder containing copper to obtain a continuous porous metal body containing copper; c. A method for producing a heat transfer material, comprising a step of subjecting the obtained continuous porous material to an oxidation treatment in this order.

It is preferable that the heat transfer material manufactured by the manufacturing method according to claim 4 be compressed in the thickness direction to adjust the thickness and the hole diameter.

That is, the invention according to claim 5 includes a step of compressing the continuous porous body obtained by erasing the holding material in the thickness direction to obtain a continuous porous body having a predetermined thickness. The method for producing a heat transfer material according to claim 4, further comprising:

The heat transfer material of the present invention is used as a heat transfer body adhered to a base. When the porous body serving as the heat transfer material is formed, the heat transfer material is simultaneously applied to the base. It is preferable to apply it because the number of steps can be reduced.

The invention according to claim 6 is the invention according to claim 4 or 5
In the method for producing a heat transfer material according to the above, the holding material in which the metal powder containing copper is applied to the holding material that has a three-dimensional mesh-like void and can be removed by heating, and further contains the copper-containing metal The step of obtaining a continuous porous porous body of a metal containing copper by sintering the powder of the heat transfer material in a state in which the holding material is in contact with the base via the powder of the metal containing copper. This is a method for manufacturing a heat transfer member that is integrally attached to a heat transfer member.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION As a metal containing copper, copper or a copper alloy can be used. Specific examples of the copper alloy include brass, which is an alloy of copper and zinc, and white copper, which is an alloy of copper, nickel, iron and manganese. Also,
When a copper alloy is used, the content of copper is preferably 70% by weight or more, and more preferably 90% by weight or more, from the viewpoint of forming irregularities by an oxidation treatment. Further, the porosity of the continuous porous body of metal containing copper (hereinafter referred to as a porous body) is preferably 90 to 95%.
If the porosity is less than 90%, the pore size becomes small,
Bubbles are less likely to escape, and the heat transfer coefficient tends to decrease. On the other hand, if it exceeds 95%, the pore diameter becomes large, so that it is difficult to hold the air bubbles, and similarly, the heat transfer coefficient tends to decrease.

The oxidizing treatment of the porous body can be performed by a treatment method known as a roughening treatment of an inner circuit board in the production of a multilayer printed wiring board. For example, it can be carried out by immersing in a treatment solution of copper acetate / copper sulfate / barium sulfide / ammonium chloride system or a treatment solution of sodium chlorite / sodium hydroxide system. By using a treatment solution of copper acetate / copper sulfate / barium sulphide / ammonium chloride system, yellow or red cuprous oxide is produced, and by using a treatment solution of sodium chlorite / sodium hydroxide system, a black or black solution is obtained. Produces cupric oxide.

As the base of the heat transfer body, stainless steel or copper is preferably used, and copper is more preferably used, from the viewpoint of heat transfer properties and adhesion when the heat transfer material is applied. The thickness of the heat transfer material applied to the substrate after compression is 0.3
It is preferably set to 0.7 mm. If the thickness is less than 0.3 mm, it tends to be difficult to make the porosity 90% or more, and if it exceeds 0.7 mm, it tends to be difficult to make the porosity 95% or less. Therefore, in any case, the heat transfer coefficient tends to decrease as described above.

The heat transfer body may be flat or tubular. Further, the heat transfer material may be applied to one side of the base, or may be applied to both sides. Whether to adhere on one side or both sides is appropriately selected depending on the application. The tubular heat transfer body can be manufactured by, for example, forming a flat plate-shaped base on which a heat transfer material is applied and welding the joint. The tubular heat transfer body is also called a heat transfer tube.

As a holding material having three-dimensional mesh-like voids and capable of being eliminated by heating (hereinafter referred to as a holding material), an organic foam having an open-cell structure, a nonwoven fabric of organic fibers, a woven fabric of organic fibers, and the like are used. be able to. Above all, an organic foam whose thickness and porosity can be freely selected is preferable. As the organic material, a material which does not melt by heating and disappears at a temperature at which metal particles containing copper sinter is preferable. Preferred organic materials include polyurethane, polypropylene, polyethylene, polyvinyl alcohol, phenol resin, urea resin and the like.

Next, the metal powder containing copper is swung by placing a holding material provided with tackiness in the metal powder containing copper, and the copper powder is adhered to the metal powder containing copper. It can be applied by, for example, a method of spraying the holding material having the property. As a method of imparting tackiness to the holding material, acrylic, rubber-based pressure-sensitive adhesive solution, or phenolic resin,
Examples include a method of applying a solution of an adhesive resin such as an epoxy resin and a furan resin to the holding material, and a method of giving the holding material itself tackiness by plasma treatment. The particle diameter of the metal powder containing copper is preferably in the range of 0.01 to 100 μm in order to adhere to the holding material. It is preferable from the viewpoint of the sintering strength between the particles that the particle size distribution is such that the small particles fill the gaps between the large particles.

As a method of removing the holding material by heating, a method of heating in an air atmosphere in which oxygen is sufficiently present is preferable, but other appropriate methods can also be used.

The step of subjecting the obtained continuous porous material to an oxidation treatment can be carried out by an oxidation treatment method for the inner layer surface employed when manufacturing a multilayer printed wiring board. The oxidation treatment in which the oxidation treatment produces black cupric oxide can be performed by using a sodium chlorite-sodium hydroxide-based treatment solution. When a copper acetate-based treatment solution is used, a brown oxide (also referred to as brown oxide) is generated, but this method can also be used.

As a method of compressing the continuous porous body in the thickness direction, a method using a press machine capable of controlling a moving distance, a method using a spacer having a predetermined height so that a distance between press plates becomes a predetermined value. And compression. It is preferable to compress at a low compression rate so as not to damage the continuous pore porous body.

[0034]

EXAMPLES Example 1 Acrylic copolymer (HTR, manufactured by Teikoku Chemical Industry Co., Ltd.)
-600 LB (trade name)), 50 parts by weight, an acrylic copolymer (manufactured by Nippon Carbide Industrial Co., Ltd.,
1161.5 parts by weight of toluene were dissolved in 50 parts by weight of -1851 (trade name) and 1 part by weight of a crosslinking agent (Coronate L (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd.) to prepare an adhesive solution. Prepared. 3 mm thick, 300 x 200 m used as a holding material in the prepared pressure-sensitive adhesive solution
m polyurethane foam (manufactured by Bridgestone Corporation,
Everlite SF (trade name) was immersed, excess adhesive solution was removed through a roll, and heated and dried at 100 ° C. for 10 minutes to remove toluene, thereby imparting tackiness to the holding material. The holding material having the tackiness is coated with an average particle size of 5 μm.
m of copper powder was buried in the copper powder, and the copper powder was swung so that the copper powder could enter the voids of the holding material, so that the holding material was coated with the copper powder. Thickness 0.5
A copper plate of 300 mm × 200 mm is used as a substrate, and copper powder is scattered and applied to one surface of the substrate, and the above-described holding material coated with copper powder is laid thereon. To remove the holding material, and then 900
C. and kept in a hydrogen gas atmosphere for 20 minutes. As a result, the copper powder scattered on one surface of the substrate and the copper powder adhered to the holding material were sintered to form a continuous porous sintered body of copper integrated with the substrate on one surface of the substrate. This continuous pore sintered body is
The porosity was 96% at a thickness of 1.5 mm. Next, the substrate on which the copper continuous-porous sintered body obtained above was formed was placed on a press plate of a press machine, and a spacer having a height of 1 mm was placed around the plate and pressed at a pressure of 1 MPa. The resulting continuous porous material has a thickness of 0.5 mm and a porosity of 48 mm.
%Met.

Sodium chlorite, sodium hydroxide and sodium phosphate are dissolved in 1 liter of pure water at a ratio of 31 g of sodium chlorite, 15 g of sodium hydroxide and 12 g of sodium phosphate to prepare an oxidized solution. Prepared. Using a cutter, the periphery of the continuous porous body obtained above was cut off at a width of 10 mm and immersed in an oxidation treatment solution heated to 60 to 80 ° C. for 2 minutes. Then, wash with tap water for 5 minutes, wash with pure water at 60 ° C for 2 minutes, and
Drying was performed in a dryer at 30 ° C. for 30 minutes to produce a plate-shaped heat transfer material having a heat transfer material on one side obtained by oxidizing a continuous porous copper body.

In the obtained heat transfer material, black cupric oxide was generated including the inside of the pores, and in the electron micrograph (× 30,000), fine irregularities were formed as shown in FIG. It was confirmed that it was formed. For reference, FIG. 1 shows an electron micrograph (magnification: 30,000) before the oxidation treatment. Further, the contact angle of pure heat to the heat transfer material of the obtained plate-shaped heat transfer body was 0 °, indicating that the wettability to pure water was extremely good. In addition, when the capillary force was examined by sucking pure water in the vertical direction at normal temperature and atmospheric pressure, the capillary force was 150 mm.

Comparative Example 1 A heat conductor was produced in the same manner as in Example 1 except that the oxidation treatment was not performed. The heat transfer material of the obtained heat transfer material was examined for the contact angle with respect to pure water in the same manner as in Example 1, and found to have a contact angle of 120 degrees. The capillary force measured in the same manner as in Example 1 was 0 mm. there were.

Example 2 The holding material was set to a thickness of 2.5 mm and dimensions of 500 × 50 mm.
Further, the thickness of the base was changed to 1 mm and the dimensions were 500 × 50 mm, respectively, and a flat heat conductor was produced in the same manner as in Example 1 below. Using this heat transfer material as a material, a pipe is formed, and the seam is welded by high frequency welding to obtain an outer diameter of 16 m.
m, a heat transfer tube 21 having a heat transfer material 20 made of a porous copper body on the outer periphery of a copper tube formed to have an inner diameter of 14 mm.

A coolant tank 22 having a cube shape of 450 mm in inner dimension and insulated so that heat does not flow in and out of the outside air is prepared.
The heat transfer tube 21 was attached at a position 150 mm from the bottom of the heat transfer pipe. Further, the refrigerant tank 22 and the condenser 23 were connected by a pipe 24 from above the refrigerant tank 22. Further, the air in the refrigerant tank 22 is suctioned and removed by a vacuum pump, and HFC-134a (representing a code number of Freon, representing 1,1,1,2-tetrafluoroethane) is filled as a refrigerant to the upper end of the refrigerant tank 22. (See FIG. 3). In this state, H
The evaporation temperature of FC-134a was 5 ° C. Then, while passing a predetermined amount of water from one end of the heat transfer tube 21, both ends of the heat transfer tube 21, the central portion surface of the heat transfer tube 21 and the heat transfer tube 21.
The temperature of the refrigerant at a position 20 mm immediately above the center of the sample was measured. When the temperature of each part becomes constant, the heat transfer amount (heat flux) is obtained from the temperature difference and the flow rate at both ends of the heat transfer tube 21, and the heat transfer amount, the surface of the central portion of the heat transfer tube 21 and immediately above the central portion of the heat transfer tube 21 2
The heat transfer coefficient was determined from the refrigerant temperature at the position of 0 mm. The relationship between the heat transfer coefficient and the amount of heat transfer (heat flux) was determined by changing the flow rate of water passing through the heat transfer tube 21. The result is shown in FIG. 4 as a graph.

Comparative Example 2 A heat transfer tube was prepared as a heat transfer member using the continuous porous sintered body before the oxidation treatment, and the relationship between the heat transfer coefficient and the heat transfer amount (heat flux) in the same manner as in Example 2 I asked. The result is shown in FIG. 4 as a graph.

[0041]

According to the heat transfer material and the heat transfer body of the present invention, since the bubble nuclei can be stably held on the surface of the heat transfer material, the nucleate boiling phenomenon can be stably maintained. . Therefore, the heat transfer coefficient of evaporation is increased, the size and performance of the heat exchanger can be reduced, and a melting accident due to a partial temperature rise can be prevented.

Furthermore, since the heat transfer material has a large capillary force, and the heat medium diffuses throughout the heat transfer material, uniform heat transfer is performed on the entire heat transfer surface. It can be operated stably when used as a heat pipe.

[Brief description of the drawings]

FIG. 1 is an electron micrograph showing a state before an oxidation treatment.

FIG. 2 is an electron micrograph showing unevenness formed by an oxidation treatment.

FIG. 3 is a schematic cross-sectional view of an apparatus used for obtaining a heat transfer amount (heat flux) in Example 2 and Comparative Example 2.

FIG. 4 is a graph showing a relationship between a heat transfer coefficient and a heat transfer amount (heat flux) in Example 2 and Comparative Example 2.

[Explanation of symbols]

 Reference Signs List 20 heat transfer material 21 heat transfer tube 22 refrigerant tank 23 condenser 24 piping

Claims (6)

[Claims] 1. A heat transfer material obtained by subjecting a continuous porous metal body containing copper to oxidation treatment. 2. The heat transfer material according to claim 1, wherein the oxidation treatment is an oxidation treatment for producing black cupric oxide. 3. A heat transfer body having the heat transfer material according to claim 1 applied to a surface of a base. 4. a. A step of applying a metal powder containing copper to a holding material having three-dimensional mesh-like voids which can be eliminated by heating; b. Removing the holding material by heating and further sintering a metal powder containing copper to obtain a continuous porous metal body containing copper; c. A method for producing a heat transfer material, comprising a step of subjecting the obtained continuous porous material to an oxidation treatment in this order. 5. A continuous pore porous body having a predetermined thickness by compressing in a thickness direction a porous body obtained by sintering a metal powder containing copper after removing the holding material by heating. The method for producing a heat transfer material according to claim 4, further comprising a step of forming a heat transfer member. 6. The method for producing a heat transfer material according to claim 4, wherein a metal powder containing copper is applied to the holding material having three-dimensional mesh-shaped voids and capable of being eliminated by heating. The step of obtaining the continuous porous body of the metal containing copper by sintering the metal powder containing copper by further erasing the holding material is performed by contacting the holding material with the base via the metal powder containing copper. A method for manufacturing a heat transfer body, wherein the heat transfer material is applied to a substrate integrally by performing the heat transfer in a state.