JP2003214780A - Heat pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat pipe possible to prevent the lowering of heat conductivity by restricting decomposition and deterioration of the low-level alcohol sealed inside. <P>SOLUTION: The inner surface of a copper pipe sealed with the low-level alcohol as a heating medium is formed with a thin film such as a Sn plating film at 0.05-2 μm of thickness. Alternatively, the hydroxy compound at 20-2000 ppm is added to the low-level alcohol. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat pipe, and more particularly to a heat pipe that prevents deterioration of heat transfer performance due to decomposition and deterioration of a heat medium.

[0002]

2. Description of the Related Art A heat medium is enclosed in a vacuumed pipe,
The heat pipe that takes heat by evaporating the heat medium and releases the heat by condensing has been used in a wide range of fields such as for cooling a central processing unit of electronic equipment.

Usually, water is used as the heat medium of the heat pipe, but in the case of a low temperature heat pipe,
Lower alcohols are used. Since lower alcohols do not have a risk of freezing at low temperatures and have no environmental problems as in Freon, which is another type of heat medium, they can be said to be optimal as heat mediums for low temperatures.

[0004]

However, according to the conventional heat pipe using the lower alcohol, the enclosed lower alcohol is decomposed and deteriorated within a relatively short period of time, and the internal pressure of the pipe is increased by the generation of gas due to this. However, it has a problem of reducing heat transfer performance.

Therefore, it is an object of the present invention to provide a heat pipe in which lowering of heat transfer performance is prevented by suppressing decomposition and deterioration of lower alcohol.

[0006]

In order to achieve the above object, the present invention provides a heat pipe constructed by enclosing a lower alcohol as a heat medium in a pipe containing copper as a constituent material. , Sn or Sn alloy plating film, oxidized Sn on the inner surface contacting the lower alcohol
The present invention provides a heat pipe characterized by having a thin film having a thickness of 0.05 to 2 μm selected from a film, a Cu oxide film or a chemical conversion treatment film.

Further, in order to achieve the above object, the present invention provides a heat pipe constituted by enclosing a lower alcohol as a heat medium in a pipe having copper as a constituent material,
The lower alcohol contains a hydroxo compound in an amount of 20 to 2000 ppm to provide a heat pipe.

In the present invention, the reason for limiting the thickness of the above-mentioned thin film to 0.05 to 2 μm is that when it is less than 0.05 μm, a predetermined decomposition and deterioration preventing effect for lower alcohols cannot be obtained, while 2 μm. When the value exceeds, the effect of forming a thin film is saturated, which causes a cost disadvantage.

The Sn or Sn alloy plated film, the Sn oxide film, the Cu oxide film and the chemical conversion treatment film, which form the thin film, all have excellent shape-following properties capable of coping with the deformation when the pipe is processed. This is one reason for choosing these films.

Hydroxylamine or hydroquinone is preferably used as the hydroxo compound, and the lower limit of the addition amount thereof is to obtain a predetermined addition effect of these compounds, and
At the upper limit, in order to minimize the damaging effect of these compounds on the inner surface of the pipe or the above-mentioned thin film formed on the inner surface, the above-mentioned 20 to 2000 ppm is used.
It is set within the range of.

The object of the present invention is to suppress the decomposition / deterioration action on the lower alcohol by the oxygen or oxide dissolved in the lower alcohol or the catalytic action of copper for promoting this action. The addition of a hydroxo compound is an effective countermeasure for suppressing the former action based on its reducing action, while the formation of a thin film on the inner surface of the pipe is an effective countermeasure for the latter action.

These measures may be applied either individually or in combination, but in the case of combined use, the preferred form is especially 10 to 4 for lower alcohols.
It can be recommended to add 00 ppm of hydroxylamine and to form an Sn plating film having a thickness of 0.05 to 1 μm on the inner surface of the pipe.

The upper limit of the addition of hydroxylamine and the upper limit of the Sn plating film thickness in this combination are at lower levels than when these are used alone, and therefore, the maximum effect of these two factors, which is increased by increasing the numerical value, is obtained. By thus reducing the upper limit value for obtaining, it is possible to suppress the above-described damaging effect of hydroxylamine and the cost disadvantage due to the formation of a thick Sn plating film to the minimum.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of a heat pipe according to the present invention will be described. Tables 1 and 2 summarize the contents of the examples and comparative examples of the present invention and the results of their implementation.

[0015]

[Table 1]

[0016]

[Table 2]

The heat pipe in each example is made of a copper pipe material having an inner diameter of 14 mm, a wall thickness of 1 mm and a length of 100.
It is processed to 0 mm, and a glass wool wick with an apparent capacity of 22 ml is stored in it, and it is stored in a vacuum of 15.5.
It was constructed by encapsulating ml of methyl alcohol.

Further, various plating films such as Sn plating are commercially available in a copper pipe by a commercially available electroless plating solution [Surface Technology Association, edited by Surface Technology Handbook, p. 322-400 (199
8) (see 8), and the plated film is grown to a predetermined thickness.

For the Sn oxide film and the Cu oxide film, 5 to 90% of air-saturated pure water of 95 ° C. × 2 atm is placed in the coil of the long copper pipe.
It is formed by circulating it for a minute, and the chemical conversion treatment film is formed in a long coil of a copper pipe with NaOH of 5% concentration each.
And a potassium chlorite solution at 80 ° C. for 2-30 minutes.

According to Table 1, Examples 1 to 5 in which the Sn or Sn alloy plating film is formed on the inner surface of the copper pipe show a high level result in the heat transfer performance after the continuous test for 3 months. On the other hand, in the case of Comparative Example 1 in which the copper material was exposed in methyl alcohol, the heat transfer performance was significantly reduced. An internal check was conducted on the heat pipe of Comparative Example 1 after the test, and a clear increase in gas pressure and discoloration of methyl alcohol were confirmed.

In Table 1, Comparative Example 2 in which the Sn plating film is formed shows a remarkable decrease in heat transfer performance after the three-month test because the Sn plating film is insufficient in thickness. The reason why the present invention excludes this even though Comparative Example 3 exhibits excellent heat transfer performance maintaining characteristics is as follows.
This is due to the saturation of the effect due to the film formation and the uneconomical effect due to the excessive thickness.

According to Comparative Examples 4 and 5 in which the Ni-based plating film was formed on the inner surface of the copper pipe, the formed plating films all caused peeling due to work deformation of the heat pipe. This indicates that since the Ni-based plating film is hard, it is not suitable for the present invention in terms of conformability to deformation. In the present invention, Sn or Sn alloy is particularly selected as the constituent material of the plating film. Here's why.

Although Comparative Examples 6 and 7 show excellent ability to maintain heat transfer performance, the reason why the present invention excludes them is that the material of the forming film is too expensive, and the cost burden is high. This is because it is large and has low feasibility in transactions.

In comparison between Examples 6 to 8 and Comparative Example 8 in which the same Sn oxide film was formed, the former has a superior ability to maintain heat transfer performance, while the latter shows a decrease in heat transfer performance. The reason is that the thickness of the latter Sn oxide film is insufficient, and Example 9 in which the Cu oxide film is formed on the inner surface is used.
The reason why and 10 and Comparative Example 9 have the same relationship is also due to the same reason.

When considering the effect of the oxide film formation, Examples 3 and 4 and Example 6 in which the same Sn-based film was formed,
It should be noted that, in contrast with No. 7, the latter formed with an oxide film exhibits excellent characteristics, even though the formed film has the same thickness. It can be said that the superiority of the oxide film appears.

In Comparative Example 10 in which the Cu oxide film was formed, the heat transfer performance retention characteristics were excellent, but the peeling occurred due to processing deformation because the film thickness was excessive. 3μ
The thickness of m is in a stage where the effect of film formation is already saturated, and the followability to deformation is lost.

In Examples 11 and 12, the effect of forming the chemical conversion treatment film is clearly shown. However, in this case as well, the thickness to be formed is important, and when the thickness is lower than the predetermined level, the heat transfer performance decreases as in Comparative Example 11, and conversely,
When the thickness is excessively large, peeling due to work deformation occurs as in Comparative Example 12.

Table 2 is an example in which hydroxylamine having a reducing action is dissolved in methyl alcohol as a heating medium. While Examples 13 to 15 to which an appropriate amount of the same compound was added show excellent heat transfer performance maintaining characteristics, Comparative Examples 13 and 1 in which the same compound is not added and whose addition amount is insufficient.
In the case of No. 4, the heat transfer performance was remarkably deteriorated in all cases, and in the case of Comparative Example 15 in which it was added excessively, it was shown that the inner surface of the copper pipe was damaged.

Further, in Examples 16 and 17 in which the Sn plating film was formed on the inner surface of the copper pipe and hydroxylamine was added to methyl alcohol, the remarkable effect was also exhibited. The effect of adding an appropriate amount of hydroxo compound such as amine is clearly shown.

In the above examples, only the case where methyl alcohol was used as the lower alcohol was described, but the same effect can be obtained even when other lower alcohol such as ethyl alcohol is used. Needless to say.

[0031]

As described above, according to the heat pipe of the present invention, Sn or Sn is formed on the inner surface of the copper pipe.
As a structure in which a thin film having a thickness of 0.05 to 2 μm selected from a plated film of an alloy, a Sn oxide film, a Cu oxide film, and a chemical conversion treatment film is formed, or a structure in which a hydroxo compound of 20 to 2000 ppm is added to a heat medium Therefore, the decomposition and deterioration of the lower alcohol enclosed as the heat medium can be effectively suppressed, and thus a highly practical heat pipe that prevents deterioration of the heat transfer performance can be provided.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C23C 18/38 C23C 18/38 18/48 18/48 18/52 18/52 (72) Inventor Shoji Kuma 3550 Kidayo-cho, Tsuchiura-shi, Ibaraki Hitachi Shinzai Co., Ltd. (72) Inventor Koichi Isaka 1-6-1, Otemachi, Chiyoda-ku, Tokyo F-Term (in reference) 4K022 AA02 AA33 AA49 BA08 BA21 BA32 DA01 EA01 EA04

Claims (5)

[Claims] 1. A heat pipe configured by enclosing a lower alcohol as a heat medium in a pipe made of copper as a material, wherein the pipe has an inner surface in contact with the lower alcohol,
Sn or Sn alloy plating film, Sn oxide film, C oxide
The thickness selected from the u film and the chemical conversion treatment film is 0.05 to
A heat pipe having a thin film of 2 μm. 2. A heat pipe constructed by enclosing a lower alcohol as a heat medium in a pipe having copper as a constituent material, wherein the lower alcohol contains 20 to 2000 ppm of a hydroxo compound. heat pipe. 3. The heat pipe according to claim 2, wherein the hydroxo compound is selected from hydroxylamine and hydroquinone. 4. The pipe is provided with an Sn or Sn alloy plating film, oxidized S on the inner surface in contact with the lower alcohol.
The heat pipe according to claim 2, further comprising a thin film selected from an n film, a Cu oxide film, and a chemical conversion treatment film. 5. The thin film is composed of an Sn plating film having a thickness of 0.05 to 1 μm, and the lower alcohol contains 10 to 400 ppm of hydroxylamine. heat pipe.