JPH04190092A - Heat pipe - Google Patents

Abstract

PURPOSE:To prevent the generation of non-condensable gas during operation and permit the operation stabilized for a long period of time by a method wherein a tube, having a strength ratio between oxygen and copper, which is lower than a specified value when the inner surface of the tube before operation is measured utilizing a X-ray microanalyzer, is employed. CONSTITUTION:A copper tube for a heat pipe is received in a vessel capable of heating, evacuating and conducti.ng reducing gas for example, and evacuation is effected between 5kgf/cm<2> from G-1X1O<8> Torr with a sufficient time to remove adsorption gas in the tube. Then, reducing process is effected and the pipe is dried in the atmosphere of inert gas. In the tube material, processed in such a manner, the strength ratio between oxygen (O) and copper (Cu) becomes lower than 1.0X10-<2> when the inner surface of the tube is measured utilizing a X-ray microanalyzer. According to this method, the generation of non-condensable gas upon operating a heat pipe can be prevented. Accordingly, a performance, stabilized for a long period of time, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a copper-based heat pipe that does not generate non-condensable gas and prevents deterioration of performance over time of use.

[Conventional technology and its issues]

A heat pipe is a metal tube made of copper or other material that is sealed with a working fluid such as water under reduced pressure.It transports heat by repeatedly evaporating the working fluid in the evaporator and condensing the steam in the condensing part. It is.

These heat pipes are generally made of copper or other materials, and are usually produced by drawing them out with a die, and then stored in the open air. This creates an oxygen film on the inner surface of the tube. The oxygen film becomes a cause of gas generation in the heat pipe, and the part where gas accumulates when the heat pipe is in operation becomes a deteriorated part that does not function as a heat pipe. Therefore, conventionally, Figure 3 (a)
As shown in (b), the length of the deteriorated part caused by gas generation is anticipated in the design, or as shown in (b), the gas is generated by operating at a temperature higher than the working temperature to be used, and (c). As shown, the tip where gas has accumulated is sealed off again to create a heat pipe.

By the way, the amount of gas generated is not so much of a problem with heat pipes with large diameters, but as the diameter of the heat pipe becomes smaller or the length becomes shorter, and the internal volume becomes smaller, the effect of the gas generated becomes greater. Become.

In particular, for micro heat pipes with a diameter of 4 m or less, it is necessary to ensure a large surface area for operation, but the internal volume decreases as the square of the inner diameter. Therefore, the amount of oxygen attached to the surface becomes a problem.

In other words, when the purpose is to use a thinner and smaller heat pipe, if the length of the deteriorated part is allowed as in the past, the proportion of the deteriorated part will be too large and it will be difficult to meet the original required specifications. be.

Further, even when the above-mentioned double sealing is performed, it is not possible to completely prevent gas generation after the double sealing, and there is a problem in that the deteriorated portion expands due to specifications.

[Problem to be solved by the invention]

The present invention was developed as a result of consideration of the above problems, and is a copper-based heat that does not generate non-condensable gas during operation, thereby preventing performance deterioration over time and enabling stable operation. The pipe was developed.

[Means and effects for solving the problems] The present invention provides a heat pipe whose tube material is made of copper, and when the inner surface of the tube material is measured using an X-ray microanalyzer before the heat pipe is operated, oxygen (O ) and copper (Cu) strength ratio is 1. The heat pipe is characterized by using a tube material having a hardness of OXl0-" or less.

That is, the present invention uses a steel pipe as a heat pipe material, for example,
It is housed in a container that can be heated and can be evacuated and a reducing gas can flow therethrough, and vacuum is applied for a sufficient time between 5 kgf/dG and IX10-''TorrO to remove the adsorbed gas on the tube material.

■Perform reduction processing.

■Dry in an inert gas atmosphere.

By performing any of the above treatments (1) to (2) alone or in combination, a pipe material with a low oxygen content can be obtained. The above treatment may be performed repeatedly, or may be performed at room temperature or by heating. Heating shortens the treatment time. The tube material treated as described above has an oxygen (O) to copper (Co) intensity ratio of 1.0 Xl0-'' or less when the inner surface of the tube material is measured using an X-ray microanalyzer. It is possible to prevent the generation of non-condensable gas during operation of the heat pipe.

If the strength ratio exceeds this, the removal of oxygen from the inner surface of the tube is insufficient and gas generation cannot be prevented.

Remaining air and gas components generated during the pretreatment process can be removed by evacuation for a long time. Oxygen on the inner surface of the tube can also be removed by reduction treatment. Furthermore, the surface can be oxidized. It is then dried in an inert gas atmosphere to avoid increasing the oxygen content on the surface.

A heat pipe is made by sealing a well-degassed working fluid into the tube material thus produced.

The heat pipe of the present invention generates far less gas during operation than conventional heat pipes, and therefore the proportion of degraded parts that occupy a small internal volume of heat pipes such as small-diameter heat pipes and short-length heat pipes is small. and significantly less deterioration than conventional heat pipes during long-term operation.

In the present invention, as the working fluid, water, fluorocarbon, and other working fluids commonly used in copper heat pipes can be used.

〔Example〕

An embodiment of the present invention will be described below.

As a tube material for heat pipes, the outer diameter is 3.0mm, and the wall thickness is 0.1mm.
A 5m long 200mm steel pipe was heated to 0700°C.
Put it in a vacuum container heated to , evacuate it, and then
2. Supply gas, plant, and vacuum.

After the final evacuation is completed, an inert gas (N, ) is supplied and the system is cooled down to atmospheric pressure at room temperature.

By adjusting the number of times of the above treatment, H, gas concentration, etc., pipe materials with different strength ratios of oxygen and copper were produced.

For comparison, we also prepared a conventional pipe material of the same dimensions that was not subjected to the above treatment.

This intensity ratio of oxygen and copper was measured using an X-ray microanalyzer under the following conditions.

■Equipment: JEOL JXA-8600■Measurement conditions
Accelerating voltage 15kV Sample absorption current 50nA Measurement area 10-φ Curved crystal Cu -K a 1.5418 people LiF spectroscopic crystal 0
-α23.65A d:60A multilayer Ml color spectroscopic crystal (bank ground is subtracted from each intensity) Using the above tube material, degassed water was sealed as a working fluid to produce a heat pipe. These heat pipes have an operating temperature of 1
After operating at 50°C for 700 hours, the strength ratio of oxygen and copper in the tube before the above operation and the temperature difference occurring in each heat pipe were investigated. The results are shown in FIG.

Note that this temperature difference is caused by the generation of non-condensable gas and is normally required to be within 1°C.

As is clear from Figure 1, the strength ratio of oxygen and copper is 1. O
For those below Xl0-”, the temperature difference between the heat pipes is 1°C.
It can be seen that the allowable temperature difference within

In addition, the strength ratio of oxygen and copper in the tube material of conventional heat pipes is 4.
．． 1×10−”, and the temperature difference is approximately 4.0° C., which is unacceptable.

Furthermore, the temperature from the evaporation end of the heat pipe of the present invention and the conventional heat pipe at an operating temperature of 50°C was investigated. The results are shown in FIG. As is clear from the figure, in the conventional heat pipe, the temperature drops from around 0.85% from the evaporation end, whereas in the heat pipe of the present invention, the temperature is uniform over almost the entire length, and performance deterioration due to gas generation is avoided. It turns out that there are few.

In this example, the oxygen film attached to the surface was removed by hydrogen reduction, but it may also be removed by pickling in an inert gas and drying.

〔effect〕

As described above, according to the present invention, since the generation of non-condensable gas during operation is extremely small, the deteriorated portion of the heat pipe can be reduced, and the size of the heat pipe can be further reduced.

In addition, since there is little performance deterioration due to gas generation, stable performance is guaranteed for a long period of time, which is a significant industrial effect.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between oxygen, copper, and temperature difference in a heat pipe according to an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between the position and temperature of a heat pipe according to an embodiment of the present invention. The graph shown in FIG. 3 is a cross-sectional view showing a conventional method for manufacturing a heat pipe. l...heat pipe, 2...non-condensable gas. Patent applicant Furukawa Electric Co., Ltd.! '! l I
! ! Phase (ρ) Length from the end of the evaporator/full length heat pipe position Figure 2 Figure 3 Procedure amendment (voluntary) March 1991 is

Claims (1)

[Claims] In a heat pipe whose tube material is made of copper, when the inner surface of the tube material is measured using an X-ray microanalyzer before the heat pipe is activated, the intensity ratio of oxygen (O) to copper (Cu) is 1.0 x 10. A heat pipe characterized by using a pipe material having a temperature of ^-^2 or less.