JPS61190092A - Manufacture of heat transfer pipe - Google Patents

Abstract

PURPOSE:To form a copper plating layer having tree plate-like ruggedness on the inside surface of a heat transfer pipe and to produce the heat transfer pipe having an excellent effect of transferring boiling heat by circulating a copper plating liquid contg. a specific surface active agent and chloride ion in the heat transfer pipe and conducting electricity between said pipe and a counter electrode therein. CONSTITUTION:The counter electrode 14 consisting of a Ti bar coated with Pt is disposed into a Cu heat transfer pipe 10 provided with heat radiating fins 3 made of thin Al sheets on the outside surface. DC is conducted to the pipe 10 as a cathode and the electrode 14 as an anode by a DC power source 13 while the Cu plating liquid 9 in a plating cell 7 is circulated in the pipe 10 by a pump 12 and a connecting pipe 11. The plating liquid contg. copper sulfate and sulfuric acid and contg. 100mg/l polyethylene glycol as an oxyethylene surface active agent and 0.001X10<-3>-2.0X10<-3>mol/l chloride ion such as HCl is used for the plating liquid. The Cu plating layer having the tree plate-like ruggedness is formed on the inside surface of the pipe 10. Such pipe has excellent heat transfer effect when used for a heat exchanger in which gaseous freon is used.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to heat exchangers and heat pipes, in particular heat transfer tubes for flowing liquid media. It is generally known that increasing the surface area promotes boiling heat transfer, but it is difficult to form a porous layer inside the heat transfer tube using sintering or thermal spraying methods, so plating methods are usually used. . However, the plating method used to increase the surface area and measure the effect of promoting boiling heat transfer requires processing under conditions different from those for smooth plating, and it is necessary to finish the plating layer with appropriate porousness and protrusions. 0As for the method of forming such a plating layer, it is necessary to add complex salts, glue-like substances, brighteners, additives for making crystal fine particles, etc. necessary for obtaining normal smooth plating to the plating solution. The plating solution is formed by using a very small amount of plating solution, plating conditions generally at high temperature and high current density, and by performing high-speed fluid stirring.

Problems to be Solved by the Invention However, even if a plating solution is introduced to the inner wall surface of the heat transfer tube under these conditions, it is difficult to uniformly form a porous plating to the inside, and the plating is unstable due to the lack of complex salts. Because the plating solution conditions are such that it decomposes in a short time and is not suitable for mass production, the adhesion between the wall surface of the heat exchanger tube and the plating layer is insufficient, and it is susceptible to vibrations and shocks when the liquid medium flows. There were problems such as the plating layer peeling off.

In view of the above-mentioned problems, the present invention provides a heat transfer tube having a heat transfer wall surface that forms a uniform and highly adhesive uneven plating layer, increases the surface area, and is capable of promoting boiling heat transfer. It is.

Means for Solving the Problems In order to solve the above problems, the heat exchanger tube of the present invention contains polyethylene glycol, which is an oxyethylene surfactant, and 0.001 x 10-3 rnol/fl to 2.
An uneven plating layer is formed on the inner wall surface of the heat exchanger tube by electroplating using a plating solution containing chloride ions of 0x10-'mo17α as an additive and using the heat exchanger tube side as a cathode.

Function The present invention has the above-described structure, so that the metal ions that are caught and complexed by the molecules of polyethylene glycol, which is an oxytyrene surfactant in the plating solution, are reduced to zero.
, 001
, OXl 0-'rnof1. In the presence of chloride ions at a low concentration of /fL, unstable plating solutions with low complex salts or plating under excessive conditions work by unstably bonding with chloride ions to form an uneven plating layer. Since no construction method is required, there is little decomposition of the plating solution, and the adhesion between the plating layer and the wall surface of the heat transfer tube is good, and the uneven plating layer can increase the surface area and promote boiling heat transfer. .

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 4.

Reference numeral 1 denotes a heat exchanger consisting of a heat exchanger tube 2 made of a copper pipe and a radiation fin 3 made of thin aluminum.

An uneven copper plating layer 5 is formed on the inner wall surface 4 of the heat exchanger tube 2. Also, both ends 6a of this heat exchanger tube 2.

6b is completely sealed by caulking and welding, and fluorocarbon gas is sealed inside. 7 is a plating tank whose temperature can be controlled by a heater 8, into which a plating solution 9 is placed. This plating solution 9 is 0.6 moj! /J!
Cu 5o4-5H20, 0,5rnol/It H
2SO4゜0.04x10 rnoX/X HCX and 1oorny/j! Contains polyethylene glycol. Reference numeral 10 denotes a heat exchanger tube made of a copper pipe before both ends 6a and 6b are sealed, and by combining a connecting tube 11 and a circulation pump 12, the plating solution 9 is circulated inside the heat exchanger tube 1°. Note that the heat radiation fins 3 have already been fixed to the outer periphery of the heat exchanger tube 10 by expanding the heat exchanger tube 10. Furthermore, in the connecting pipe 11,
A counter electrode 14 made of a platinum-plated titanium rod directly connected to a DC power source 13 and a connecting terminal 15 to which a charge opposite to that of the counter electrode 14 is applied are fixed. When the heat exchanger tube 1o and the connecting tube 11 are connected with the connection terminal 16, a spacer 16 made of a non-conductor made of polypropylene is inserted to prevent contact between the connection terminal 15 and the heat exchanger tube 1o. Further, 17 is an air pump that sucks air into the plating solution 9.

Next, a method for manufacturing a heat exchanger with such a configuration will be described.

First, the heat exchanger tube 1o and the heat radiation fin 3 are temporarily fitted in a fixed position, and the heat exchanger tube 10f is expanded using a predetermined tube expanding machine, and the heat exchanger tube 1o and the heat radiation fin 3 are crimped together. Next, the heat transfer tube 10, the connecting tube 11, and the circulation pump 12 are combined to circulate the plating solution 9 in the plating bath 7 into the heat transfer tube 10. At this time, the plating solution 9 is 0,6rno
X/fl CuSo4・5H20゜0.5moA/J!
H2SO4,0,04x10 rnoX/ft HC
jl.

An acidic copper sulfate plating solution containing 1009/n polyethylene glycol is used. Therefore, the counter electrode 14, which is a titanium rod plated with platinum, is positively charged by the DC power source 13, making it the anode side, and one of the connecting terminals 16 is negatively charged, making it the cathode side. The current value at this time is approximately 200 mA/
Crd and turn on electricity for about 20 minutes. The temperature of the plating solution was heated to about 50° C. by the heater 8 of the plating tank 7.

If a normal plating solution is used, copper will be deposited in a uniform thickness on the entire inner wall surface of the heat exchanger tube 10 on the cathode side, but the plating solution 9 contains polyethylene glycol, which is an oxyethylene-based surfactant. Since the copper plating layer 6 contains chlorine ions produced by low concentration hydrochloric acid, the copper plating layer 6 does not have a uniform thickness over the entire surface, and the copper plating layer 6 is uneven. The reason for this is that copper ions, which are trapped and complexed by molecules of polyethylene glycol, a surfactant, combine unstablely with chlorine ions in the presence of low concentrations of chlorine ions. In the formation of the copper plating layer 5, the concentrations of surfactants polyethylene, recall, and hydrochloric acid play important roles, and in particular, the concentration of hydrochloric acid must be defined within the following range. 'mo11. /fl ~2. O
X10-3rnoV1 Next, the inner wall of the heat transfer tube 10 is washed with hot water, and after drying, Freon gas is sealed inside, and both ends 6a are sealed.

By performing 6bi caulking welding, a heat exchanger 1 having heat transfer tubes 2 and radiation fins 3 is completed.

The heat exchanger 1 thus obtained has a copper plating layer 6 having an uneven surface on the inner wall surface 4 of the heat exchanger tube 2 due to the addition of a specified amount of polyethylene glycol and hydrochloric acid as surfactants in the plating solution. In addition to increasing the surface area, the uneven copper plating layer 6 has densely formed dendritic copper plating, which prevents boiling heat transfer. When the freon gas liquefies on the inner wall surface 4, the liquid layer forms a boiling nucleus, which promotes boiling heat transfer compared to ordinary needle-shaped uneven plating. Since the particles become droplets at the inner wall surface 4 and separate from the inner wall surface 4 faster than the smooth surface, a thick heat-insulating liquid layer is not formed, and heat transfer during condensation is also promoted. Enclose, evaporate and condense
The inner wall surface 4 of the heat exchanger tube 2 on which the dendritic copper plating formed by the above method is densely formed is obtained. The uneven copper plating layer 5 does not require an unstable plating solution with few complex salts or a plating method under excessive conditions, so there is little decomposition of the plating solution and its hardness and adhesion are very good, and the unevenness is always stable. A copper plating layer 6 is formed.

In the embodiment of the present invention, an acidic copper sulfate plating solution was used as a means for forming the uneven plating layer 5, but although copper is advantageous in terms of thermal conductivity, other metal plating solutions may also be used. It is not limited to copper plating. Furthermore, as for hydrochloric acid, a chloride such as N a Cft can be used, and it contains all the chloride ions liberated as chloride ions in the plating solution. However, the chlorine ion concentration is 2,
When Ox 10-3 rnoR, 711 or more, the plating layer does not become an uneven plating layer 5, but becomes a flat plating layer, and 0. When oo1x is less than 10-5 mOβ/J2, an uneven plating layer 5 is formed, but the density of the plating becomes sparse.

Effects of the Invention As described above, the present invention provides polyethylene glycol, which is an oxyethylene surfactant, and 0.001%
X 10-'rnoIl,,/λ to 2.0X1
Since the heat exchanger tube is formed by forming a dendritic uneven plating layer using a plating solution containing chloride ions of 0-'man/n as an additive, the following effects can be obtained.

(al) Tree-like plating is densely formed on the uneven plating layer on the inner wall surface of the heat exchanger tube, and this not only increases the surface area, but also because the dendritic plating is densely formed. When the plating layer is used in a heat pipe, it becomes a boiling nucleus for boiling heat transfer, and the effect of promoting boiling heat transfer can be measured compared to ordinary needle-like uneven plating.

(b) Regarding heat transfer during condensation, when fluorocarbon gas liquefies on the inner wall of the heat transfer tube when used in a heat pipe, the liquid layer becomes droplets on the convex parts of the uneven plating layer, and the liquid layer spreads from the inner wall to the smooth surface. Because they separate quickly, a thick insulating liquid layer is not formed, and heat transfer during condensation is promoted. (C) The uneven plating layer formed on the inner wall of the heat transfer tube is Since it does not require an unstable plating solution containing few complex salts or a plating method under excessive conditions, there is little decomposition of the plating solution, its hardness and adhesion are very good, and a stable uneven plating layer is always formed.

However, the concentration of chloride ions is 0.001
If the 'mo is less than 171, an uneven plating layer will be formed, but the density of the plating will be sparse; OX10-3m
oj! /n or more, the plating layer becomes a flat plating layer instead of an uneven plating layer, so the chlorine ion concentration becomes o.
, oolx 1o -'rno11. /11~2xi
It is necessary to specify the range of o -'moil/It.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a heat exchanger showing an embodiment of the present invention;
FIG. 2 is a longitudinal sectional view of the heat exchanger, FIG. 3 is a perspective view of the heat exchanger, and FIG. 4 is a schematic diagram of the plating apparatus. 1...Heat exchanger, 2...Heat transfer tube, 6.
...Rough copper plating layer, 9...Plating solution, 1
6... Opposite. Name of agent: Patent attorney Toshio Nakao Haga 1 person 1°
"9-jv"='1i151.
vs. Yang

Claims (1)

[Claims] Polyethylene glycol, which is an oxyethylene surfactant, and 0.001 x 10^-^3 mol on the wall surface of the heat exchanger tube.
A method for manufacturing a heat exchanger tube in which a dendritic uneven plating layer is formed using a plating solution to which chloride ions of 2.0×10^-^3 mol/l are added as an additive.