JPS61201796A - Manufacture of wall surface of heat exchanger tube - Google Patents

Abstract

PURPOSE:To accelerate boiling heat transfer by a heat exchanger tube by forming an uneven metallic layer on the wall surface of the tube by plating so as to increase the surface area. CONSTITUTION:An uneven metallic layer is formed on the wall surface of a heat exchanger tube by plating with a plating soln. contg. an oxyethylene surfactant and low concn. chloride ions as additives. At this time, a counter electrode put in the plating soln. along the inner wall of the heat exchanger tube is made of a metal nobler than the metal for plating. In the 1st stage, the metal for plating is deposited on the counter electrode by using the wall surface of the heat exchanger tube as the anode and the counter electrode as the cathode. In the 2nd stage, the wall surface of the heat exchanger tube is plated by using the wall surface as the cathode and the counter electrode as the anode. The electric capacity in the 2nd stage is made larger than the electric capacity in the 1st stage.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to heat exchanger tubes for use in heat exchangers and heat pipes, in particular for flowing liquid media.

Conventional Technology It is generally known that a porous layer is formed in a heat exchanger member to increase the surface area and promote boiling heat transfer, but forming a porous layer in a heat exchanger tube is difficult due to sintering, Since thermal spraying is difficult, plating is usually used. However, the plating layer that is used to increase the surface area and promote boiling heat transfer needs to be processed under conditions different from those for smooth plating to create a 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. Using a very small amount of plating solution,
The plating conditions are generally high temperature and high current density, and the plating solution is formed by high-speed fluid stirring.

Problems to be Solved by the Invention However, even if the plating solution is introduced onto the inner wall surface of the heat transfer tube under these conditions, it is not possible to uniformly form porous plating all the way to the inside, and the plating solution is unstable due to the presence 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 heat exchanger tube wall and the plating layer is also insufficient, and it is susceptible to vibrations and shocks when the liquid medium flows. There were defects 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, has an increased surface area, and is effective in 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 is manufactured using a plating solution containing an oxyethylene surfactant and a low concentration of chloride ions as additives. This method forms an uneven metal plating layer on the wall surface.The counter electrode inserted along the inner wall of the heat transfer tube is made of a metal more noble than the plating metal.In the first step, the heat transfer tube wall surface is placed on the anode side and the counter electrode is placed on the cathode side. side, plated metal is deposited on the counter electrode, and in the second step, the heat transfer tube wall surface is switched to the cathode side and the counter electrode to the anode side, and the second process time is longer than the first process time. This is the manufacturing method.

Function According to the present invention, the oxyethylene surfactant in the plating solution forms a complex with metal ions, and the chloride ions work to form an appropriate unevenness. moreover,
By making the wall surface of the heat transfer tube the anode side in advance and electrolyzing the wall surface of the heat transfer tube, the wall surface of the heat transfer tube is not only cleaned, but also
Since the uneven state is promoted, the adhesion becomes good and the uneven state becomes suitable for a heat exchanger tube.

Furthermore, by making the second step longer than the first step, the surface of the noble metal of the counter electrode is exposed, and a large amount of oxygen is generated from the surface of the noble metal. , a smooth, adhesive and hard plating layer will be overplated. In other words, a metal plating layer with an uneven surface area that requires an unstable plating solution containing few complex salts, a plating method under excessive conditions, or has roughness 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 vibrator and a heat radiation fin 3 made of a thin piece of aluminum.

An uneven copper plating layer 5 is formed on the inner wall surface 4 of the heat exchanger tube 2, and an overplating layer 5' is further formed thereon. Moreover, both ends 6a of this heat exchanger tube 2.

6b is completely sealed by caulking and welding, and fluorocarbon gas is sealed inside. 07 is a plating bath whose temperature can be controlled by a heater 8, into which a plating solution 9 is placed. The plating solution 9 was 150 t/1. Cu
5O4-sH20, and sot/1H2So4. O,0
An acidic copper sulfate plating solution containing 15 f/jl polyoxyethylene oleyl ether and 0.3 mmol of hydrochloric acid is used.

Further, 1o is a heat transfer tube made of a copper pipe before both ends ea and eb are sealed, and by combining a connecting tube 11 and a circulation pump 12, the plating solution 9 is circulated inside the heat transfer tube 10. . 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 1o. Further, fixed to the connecting tube 11 are a counter electrode 15 made of platinum-plated titanium rod, which is directly connected to a DC power supply 14 via a changeover switch 13, and a connecting terminal 16 that is given an opposite charge to the counter electrode 16. . When the heat exchanger tube 10 and the connecting tube 11 are connected by the connecting terminal 16, the connecting terminal 16
and the heat exchanger tube 10 become electrically conductive. Further, a spacer 7 17 made of polypropylene and a non-conductor is inserted into the counter electrode 15 to prevent contact with the heat exchanger tube 1o. Further, 18 is an air pump for blowing 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 10 and the heat radiation fin 3 are temporarily fitted in a fixed position, the heat exchanger tube 1o is expanded using a predetermined tube expanding machine, and the heat exchanger tube 10 and the heat radiation fin 3 are crimped together. Next, the heat exchanger tube 1o, the connecting tube 11, and the circulation pump 12 are combined, and the plating liquid 9 in the plating bath γ is circulated inside the heat exchanger tube 10. At this time, the plating solution 9 is 150 g/X C.
u SO4・5 H20.

50 f/fl H,,SO4,0,06t7Q1.
polyoxyethylene oleyl ether, and 0.3
Use an acidic copper sulfate plating solution containing millimoles of hydrochloric acid. Therefore, in the first step, a negative charge is applied to the DC power supply 14 and the counter electrode 15, which is made of a dititanium bar plated with platinum, to make it the cathode side, and a positive charge is applied to the other side and the connecting terminal 16, and it becomes the anode. do. The current value at this time is approximately 1oomA
/d and energize for about 20 minutes. That is, since the connection terminal 1θ and the heat exchanger tube 10 are electrically conductive, the heat exchanger tube 1o has a positive charge, and copper ions, which are cations in the plating solution s, are deposited on the counter electrode 16, and the heat exchanger tube 1o is electrically conductive. Copper on the inner wall surface of 10 is eluted by electrolysis.Next, as a second step, the changeover switch 13 is used to reverse the positive and negative charges.

That is, the counter electrode 16 side is used as an anode, and the connection terminal 16 and heat exchanger tube 10 side are used as a cathode. Therefore, the copper deposited on the counter electrode 15 side in the step is instead dissolved in the plating solution 9, and the copper ions in the plating solution 9 are deposited as copper on the inner wall surface of the heat exchanger tube 10.

The current value at this time was also about 1 oomA/-, and the time was about 30 minutes. Further, the temperature of the plating solution 9 was heated by the heater 8 of the plating tank 7 to about 60°C.

If a normal plating solution is used, copper will be deposited with a uniform thickness on the entire inner wall surface of the heat exchanger tube 10, but the plating solution 9 contains polyoxyethylene oleyl ether, an oxyethylene surfactant, and Since the copper plating layer 6 contains chlorine ions generated by hydrochloric acid at a low concentration of .3 mmol, 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 low concentrations of chlorine ions bond unstablely with complexed copper ions. Further, the copper plating layer 5 obtained in this manner has a height difference of about 100 μm between the unevenness.

However, since the plating is performed inside the tube, a large amount of monovalent copper ions are generated, resulting in an unstable state, so the uneven copper plating layer 6 may become relatively soft.

Therefore, since the time of the second step is longer than that of the first step, the noble metal surface of the counter electrode 16 is exposed, and a large amount of oxygen is generated from the surface of the counter electrode 16. This large amount of oxygen is 1
In order to oxidize valent copper ions to stable divalent copper ions, the unstable bond with chlorine ions, which is a feature of the present invention, is canceled and the uneven metal plating layer is no longer created. Then, a stable overplating layer 5' which is relatively hard and has good adhesion is formed.

Next, the inner wall of the heat exchanger tube 10 is washed with hot water and dried, after which a fluorocarbon gas is sealed inside and both ends 6a and 8b are caulked and welded to form a heat exchanger having the heat exchanger tube 2 and the heat radiation fins 3. 1 is completed.

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 has the effect of increasing the surface area and promoting boiling heat transfer, and when the fluorocarbon gas liquefies on the inner wall surface 4, the liquid layer forms particles on the convex parts of the plating layer 5. The heat exchanger 1, which is like a heat pipe and which is filled with liquefied gas and repeats vaporization and condensation, has a significantly improved heat transfer efficiency.

In the examples of the present invention, an acidic copper sulfate plating solution was used as a means for forming an uneven plating layer, but although copper-based plating solutions are advantageous in terms of thermal conductivity, other metal plating solutions may also be used. , it is not limited to copper plating. Although polyoxyethylene oleyl ether was used as a surfactant, all oxyethylene surfactants such as polyethylene glycol and polyoxyethylene noryl phenyl ether are included. Also, regarding hydrochloric acid, Na
A chloride such as Cl2 is also possible, and includes all chloride ions released as chloride ions in the plating solution. However, when the chlorine ion concentration exceeds 1 mmol, the bond with the complexed copper ion becomes stable, so
Since copper is deposited with a uniform thickness throughout, the chlorine ion concentration must be kept at a low concentration of 1 mmol or less.

In addition, in the examples of the present invention, the capacitance was changed by making the second step longer than the first step, but even if the current density was larger in the second step, the uneven metal It is possible to form an overmetal layer on the plating layer S.

Effects of the Invention As described above, the present invention forms an uneven metal plating layer on 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. , a metal more noble than the plated metal is used for the counter electrode inserted along the inner wall of the heat exchanger tube, and in the first step, the wall surface of the heat exchanger tube is set as the anode side, the counter electrode is set as the cathode side, and the plated metal is deposited on the counter electrode, In the second step, the wall surface of the heat transfer tube is placed on the cathode side.

This method of manufacturing heat transfer tube walls is characterized by switching the counter electrode to the anode side and making the capacitance in the second step much higher than the capacitance in the first step, which is inexpensive and under plating conditions that can be mass-produced. By controlling the chlorine ion concentration, plating solution temperature, current density, and plating time, we can stabilize the hardness and shape of the unevenness, form an uneven plating layer with excellent adhesion, increase the surface area, and improve boiling heat transfer. It also has the effect of promoting heat transfer efficiency in condensation, making it easy to form highly efficient heat transfer tube walls.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of heat exchanger A-8 showing an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of the heat exchanger, FIG. 3 is a perspective view of the heat exchanger, and FIG. The figure is a schematic diagram of the plating apparatus. 1... Heat exchanger, 2.10... Heat exchanger tube, 5... Uneven metal plating layer, 9... Plating solution, 16... Counter electrode . Name of agent: Patent attorney Toshio Nakao and one other person J2N) i Ward (cQ Castle)

Claims (1)

[Claims] An uneven metal plating layer is formed on the wall surface of the heat transfer tube using a plating solution containing an oxyethylene surfactant and a low concentration of chloride ions as additives. , a metal nobler than the plating metal is used, and in the first step, the wall surface of the heat transfer tube is made the anode side and the counter electrode is the cathode side, and the plating metal is deposited on the counter electrode, and in the second step, the wall surface of the heat transfer tube is made the cathode side, A method for manufacturing a heat exchanger tube wall surface, characterized in that the counter electrode is switched to the anode side, and the capacitance in the second step is made larger than the capacitance in the first step.