JPS6126785A - Manufacture of heat exchanger member - Google Patents

Abstract

PURPOSE:To form a porous layer at heat transfer surface to improve boiling heat transfer coefft., by coating heat transfer surface of heat exchanger with solder mixed with Zn powder, then melting only Zn powder and removing it. CONSTITUTION:Solder flux for Sb-Sn is poured into a Cu tube 2 of heat exchanger composed of a fin 1 made of Al and the tube 2 to coat the inner part. Next, the heat exchanger is put in furnace having about 300 deg.C inside temp., while cooling the fin 1 side with the furnace temp. air, on the other hand, Pb- Sn solder mixed with Zn powder is poured in the tube 2 while being melted at about 350 deg.C. Soldered layer is solidified and formed in the tube 2, then acidic etching agent is fed in the tube 2 to etch only Zn in the soldered layer, and the porous layer 5 having about 50-200mu pore is formed at inner surface of the tube 2. Heat exchanger having extremely high boiling and forced convection heat transfer coefft. at inner side of the tube 2 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a member for a heat exchanger that heats or cools a fluid by heat transfer.

Conventional Structures and Problems Conventional heat exchanger members have been designed with heat transfer surfaces to maximize the contact area of heat exchange parts. However, in recent years, a porous metal layer has been proposed to further improve its efficiency, and this has been proven to be particularly effective as a tube member for evaporators that utilizes the promotion of boiling heat transfer. . Conventionally, as a method for forming a porous layer on a metal object, there is a method of sintering metal powder or bonding it using a special brazing material. All of these methods have the common drawback of high temperature and long processing times. or,
Generally, heat exchangers used for air conditioning are composed of aluminum fins and copper circular tubes, and methods such as sintering metal powder inside copper circular tubes, which are expected to be particularly effective, have a temperature higher than the melting point of Al. In addition, it is extremely difficult to form a porous layer uniformly over a long distance within a circular pipe, and it has not been put to practical use.

Purpose of the Invention Therefore, the present invention provides a method for forming a porous layer that can be heat-treated at a temperature below that does not affect Al, that can form a porous layer even in a long pipe, and that is industrially easy. This is what we provide.

Composition of the invention That is, the present invention mixes zinc powder into solder.

While melting, the heat transfer surface inside the evaporation tube is coated, and after cooling, only the Zn is etched with acid to form a porous layer.

Description of examples An embodiment of the present invention will be described below with reference to the accompanying drawings.

In the heat exchanger for refrigeration and air conditioning shown in Fig. 1, the fins 1 are made of Al
The tube 2 is made of Cu and has a structure assembled by mechanically expanding the Cu tube. Air to be cooled 3 flows on the fin 1 side, and a fluorocarbon-based refrigerant 4 flows in the tube 2, and in the case of an evaporator, a boiling-forced convection heat transfer state is established.

In this case, if a porous material with pores of about 5 to 200 microns is formed on the inner wall surface of the tube 2, an extremely high effect of improving the boiling-forced convection heat transfer coefficient inside the tube by 3 to 10 times can be obtained. Proven.

Pb--Sn solder flux is introduced into the tube 2 to coat the inside of the tube 2 with 7 lux.

Next, the heat exchanger was placed in a chamber with a furnace temperature of about 300°C, and while the heat exchanger fin 1 side was cooled by the furnace-temperature air, the Pb-8n solder mixed with Zn powder was heated to 350°C. After melting at a certain level, it flows into the tube 2. When the molten solder flows in, a portion of the inflow solder solidifies on the inner wall surface of the tube 2, and a solder layer is formed on the inner wall surface of the tube 2. Thereafter, the tube is filled with an acid-based etching agent, and a chemical reaction occurs. In this example, Pb-8n has good compatibility with Zn and melts at 300C to 400C. During solidification, the Zn component agglomerated to a suitable particle size, so that a porous layer with pores of 1 to 50 microns was formed by acid etching, resulting in an extremely high boiling heat transfer effect.

Effects of the Invention As is clear from the above explanation, since the present invention forms a porous layer in a solid state, it can be widely applied to pipe materials other than copper, such as iron and aluminum. It is now possible to make even inner tubes with complex shapes porous, promoting boiling heat transfer and improving the efficiency of the heat exchanger.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a heat exchanger manufactured according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line . FIG. 2...Tube (heat exchanger heat transfer surface), 6...
・Porous layer. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
figure

Claims (1)

[Claims] Manufacture of a heat exchanger member characterized by coating the heat transfer surface of the heat exchanger with solder mixed with zinc powder, and then melting only the zinc powder with acid to form a porous layer on the heat transfer surface. Method.