JPS6131891A - Heat transfer tube - Google Patents

Abstract

PURPOSE:To permit to form the wall surface of the heat transfer tube having a high efficiency easily by a method wherein a recessed and protruded metal plating layer is formed on the wall surface of heat transfer tube by plating liquid added with oxyethylene series surface-active agent and chloride ion as an additive agent. CONSTITUTION:The protruded and recessed copper plating layer 5 is formed on the inner wall surface 4 of heat transfer tube 2 for a heat exchanger 1, consisting of the heat transfer tube 2 of copper pipe and heat radiating fins 3 formed by aluminum thin pieces. In this case, the plating liquid added with oxyethylene series surface-active agent and chloride ion of low concentration as the adding agent, is employed. For example, the plating liquid of acid copper sulfate consisting of 100g/l of CuSO4. 5H2O, 0.50g/l of H2SO4, 0.02g/l of polyoxyethyleneprophleneglycol and 0.2mm.mol of hydrochloric acid is employed. When the concentration of chlorine ion becomes 1mm.mol or more, copper is separated out with an uniform thickness as a whole, therefore, the concentration of chlorine ion should be kept lower than 1mm.mol.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to heat exchanger tubes used in heat exchangers and heat pipes, in particular to flow a liquid medium.

Conventional structure and its problems It is generally known that a porous layer is formed in a heat exchange member to increase the surface area and promote boiling heat transfer, but it is generally known that a porous layer is formed in a heat exchanger tube to increase the surface area and promote boiling heat transfer. This is difficult to do with sintering or thermal spraying, so plating is usually used. However, such a plating layer, which is intended to increase the surface area and promote boiling heat transfer, must be processed under conditions different from those for smooth plating, and it is necessary to finish the plating layer with appropriate porousness and protrusions.

The method for forming such a plating layer is to avoid adding complex salts, glue-like substances, brighteners, additives for making crystal fine particles, etc. to the plating solution, which are necessary to obtain normal smooth plating. A very small amount of plating solution is used, the plating conditions are generally high temperature and high current density, and the plating solution is stirred at high speed.

However, even if the plating solution is introduced onto the inner wall surface of the heat transfer tube under these conditions, it will not be possible to uniformly plate the inside of the tube, resulting in unstable plating solution conditions with less complex salts. Not only does this cause separation, making it unsuitable for mass production, but the adhesion between the heat exchanger pipe wall and the plating layer is also insufficient, resulting in defects such as the plating layer peeling off when the liquid medium flows or due to vibration or impact. was there.

Purpose of the Invention The present invention provides a plating solution by intervening a surfactant such as oxyethylene and an appropriate concentration of chloride ions in the plating solution.
By forming striations and roughness on the inner wall surface of the heat transfer tube, it is possible to have a plated product uniformly and with excellent adhesion under stable plating conditions that can be mass-produced, increasing the surface area and promoting boiling heat transfer. The purpose is to form a heat transfer wall surface that can be measured.

Structure of the Invention In order to achieve this object, the present invention interposes an oxyethylene surfactant and an appropriate concentration of chloride ions in the plating solution, and performs electroplating using the heat transfer tube side as a cathode. A metal deposit layer with striations or roughness is formed on the inner wall surface of the heat tube. In other words, there is no need for an unstable plating solution with less complex salts or a plating method under excessive conditions, so there is less decomposition of the plating solution, and the adhesion between the plating layer and the wall surface of the heat transfer tube is good, which eliminates the above-mentioned streaks or variations. The metal deposit layer can increase the surface area and promote boiling heat transfer.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below 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. Both ends ea and eb of this heat transfer tube 2 are still completely sealed by caulking and welding, and fluorocarbon gas is sealed inside.

7 is a plating bath whose temperature can be controlled by a heater 8, into which a plating solution 9 is placed. This plating solution 9 is 1o
oy/i Cu5O4-sH20.

s o y/e H2S O4+ O-02y/ l
An acidic copper sulfate plating solution containing polyoxyethylene propylene glycol and 0.2 mmol of hydrochloric acid is used. Further, 1o is a copper pipe before both ends 6a and eb are sealed, and by combining a connecting pipe 11 and a circulation pump 12, the plating solution 9 is circulated inside the copper pipe 1o. Note that the radiation fins 3 have already been fixed to the outer periphery of the copper pipe 10 by expanding the copper pipe 1o. Furthermore, an anode side electrode 14 with a positive charge and a cathode side electrode 16 with a negative charge, which are directly connected to the DC power supply 13, are fixed to the connecting pipe 11.
When the copper pipe 10 and the connecting pipe 11 are connected, the copper pipe 9 and the cathode side electrode 15 are brought into contact with each other.

Further, the anode side electrode 14 is covered with a non-conductive net 16 made of polyester fiber or the like to prevent contact with the copper pipe 10.

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

First, the copper vibrator 1o and the heat radiation fin 3 are temporarily fitted in a fixed position, and the copper pipe 10 is expanded using a predetermined tube expander, and the copper pipe 10 and the heat radiation fin 3 are crimped together. next,
The copper pipe 10, the connecting pipe 11, and the circulation pump 12 are combined to circulate the plating solution 9 in the plating bath 7 inside the copper pipe 10. At this time, the plating solution 9 is 1oo
y/1CuS04.5H20,6oy/1H2So4.
An acidic sulfuric acid steel plating solution containing o, o2y/l polyoxyethylene propylene glycol and 0.2 mmol of hydrochloric acid is used. Therefore, the DC power supply 13 applies a positive charge to the anode side electrode 14 and a negative charge to the cathode side electrode 15. That is, the cathode side electrode 15 and the copper pipe 1
Since the copper pipe 10 is in contact with the copper pipe 10, the copper pipe 10 has a negative charge. Therefore, copper ions, which are cations in the plating solution 9, are deposited on the inner wall of the copper pipe 1°. If it is a normal plating solution, copper will be deposited with a uniform thickness on the entire inner wall surface of the copper pipe 1o, but the plating solution 9 contains polyoxyethylene propylene glycol, which is an oxyethylene-based surface active layer, and 0.2 mm%) W) Hydrochloric acid plating bath temperature was about 3 o'C, current density was about s, s
A/dm2, approximately 60 II m when the current is applied for approximately 30 minutes
A plating layer 6 having uneven heights is formed.

Next, the inner wall of the copper pipe 10 is washed with hot water and dried, after which a fluorocarbon gas is sealed inside, and both ends 6a and 6b are caulked and welded to form a heat exchanger having a heat exchanger tube 2 and a heat radiation fin 3. 1 is completed 0 The heat exchanger 1 obtained in this way has the inner wall surface 4 of the heat exchanger tube 2.
The uneven plating layer 6 not only has the effect of increasing the surface area and promoting boiling heat transfer, but also has the effect of increasing the surface area of the inner wall surface 4.
When the fluorocarbon gas liquefies, the liquid layer becomes droplets on the convex part of the plating layer 6 and separates from the inner wall surface 4, so a thick insulating liquid layer is not formed, so heat transfer during condensation is prevented. will also be promoted. That is, a heat pipe-like heat exchanger 1 in which liquefied fluorocarbon gas is sealed and repeats vaporization and condensation can be obtained, with significantly improved heat transfer efficiency.

In the embodiments of the present invention, an acidic copper sulfate plating solution was used as a means for forming an uneven plating layer, but although copper is advantageous in terms of thermal conductivity, it is possible to use other metal plating solutions. It is not limited to copper plating. Although polyoxyethylene propylene glycol was used as a surfactant, it includes all oxyethylene surfactants such as polyoxyethylene nonylphenyl ether and polyethylene glycol. Furthermore, regarding hydrochloric acid, N
It is also possible to use chloride such as aCl, which contains all chloride ions released as chloride ions in the plating solution. However, if the chlorine ion concentration is 1 mmol or more, copper will precipitate with a uniform thickness over the entire surface, so the chlorine ion concentration must be kept at a low concentration of 1 mmol or less.

Effects of the Invention As is clear from the above explanation, the present invention has the advantage of applying an oxyethylene surfactant and a low concentration of chloride ions to the wall surface of a heat transfer tube using a plating solution containing an oxyethylene surfactant and a low concentration of chloride ions as additives. This product has a plated layer formed on it, under stable plating conditions that can be mass-produced, by controlling the chlorine ion concentration, the uneven shape is stabilized, and an uneven plated layer with excellent adhesion is formed.
It increases the surface area, has the effect of promoting boiling heat transfer, and also has the effect of promoting heat transfer efficiency in condensation, making it possible to easily form a highly efficient heat transfer tube wall surface.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a heat exchanger showing an embodiment of the present invention, Fig. 2 is a vertical sectional view of the heat exchanger, and Fig. 3 is an A of the heat exchanger.
-A/Horizontal view, FIG. 4 is a schematic diagram of the same plating apparatus. 1... Heat exchanger, 2... Heat exchanger tube, 3.
・Mark・Radiating fin, 5... Uneven plating layer, 9
・・・・・・Plating liquid. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3

Claims (1)

[Claims] A heat exchanger tube with an uneven metal plating layer formed on the wall surface of the tube using a plating solution containing an oxyethylene surfactant and a low concentration of chloride ions as additives.