KR100787953B1 - Heat pipe with light weight wick structure - Google Patents

Abstract

The present invention relates to a heat pipe, and more particularly, a light wick heat pipe having excellent capillary effect by attaching a light and excellent capillary phenomenon such as porous polyvinyl alcohol (PVA) sponge or pulp to the inner wall of the pipe. It is about. The heat pipe of the present invention includes a hollow metal pipe 11 having both ends 11a and 11b sealed in a vacuum state, a lightweight porous wick 12 having excellent capillary action attached to an inner wall of the metal pipe 11, It comprises a working fluid filled inside the hollow pipe (11).

Heat pipe of the present invention is excellent in heat transfer in any of the up, down, left and right directions and both ends of the pipe has a shaft tube finish to simplify the work process.

Heat pipes, wicks, polyvinyl alcohol (PVA) sponges, pulp

Description

Heat pipe with lightweight wick structure {HEAT PIPE WITH LIGHT WEIGHT WICK STRUCTURE}

1 is a schematic diagram showing a heat pipe of a conventional general wick structure.

2 to 4 are longitudinal sectional views of a heat pipe showing the structure of the heat pipe according to the present invention and a manufacturing method thereof.

5 to 7 are cross-sectional views showing a wound state of a wick attached and inserted into the pipe inner wall of the heat pipe of the present invention.

8 is a schematic diagram showing an experimental state of a heat pipe in order to compare and test the operating performance of the heat pipe and the conventional heat pipe according to the present invention;

9 is a table showing the results of a comparative experiment of the operating performance of the heat pipe according to the present invention and the conventional heat pipe.

<Explanation of symbols for the main parts of the drawings>

1, 10: heat pipe

2, 12: Wick

3: metal mesh

14: injection tube

16: closed part

18: sealing part

The present invention relates to a heat pipe, and more particularly, a light wick heat pipe having excellent capillary effect by attaching a light and excellent capillary phenomenon such as porous polyvinyl alcohol (PVA) sponge or pulp to the inner wall of the pipe. It is about.

As shown in FIG. 1, the conventional capillary development type heat pipe 1 attaches a dense and thin metal mesh 3 to the inner wall of the metal pipe 2, or close to the inner wall of the metal pipe 2; It has been produced by injecting a working liquid such as methyl alcohol, acetone, water (distilled water) into a metal pipe having a fine groove or using a combination of the two methods, and sealing the metal pipe by vacuum. This capillary development heat pipe 1 is a working liquid at the heated end 1a when one end 1a of the heat pipe 1 with the metal mesh 3 is heated with an external heat source (not shown). Evaporate, and the evaporated working fluid transfers the latent heat of evaporation around the outside of the heat pipe, moving in the gaseous state through the hollow portion 1b of the heat pipe to the other end 1c that is not heated in the direction of the arrow A. Condensed, and the condensed liquid returns to the heating site, that is, the end 1a in the direction of the arrow B by capillary action through the metal mesh 3 or the grooves, and evaporates again, thereby providing continuous heat transfer. It is configured to

Conventionally, heat pipes using such a dense metal mesh have been most used. However, such a heat pipe is required to adhere a dense metal mesh to the entire inner wall of the heat pipe is difficult to manufacture when the heat pipe is thin or long, thereby increasing the manufacturing cost. In addition, when the heat pipe needs to be bent, it is very difficult to bond the metal mesh to the inner wall of the pipe in a bent state, and when the heat pipe is manufactured and bent after the metal mesh is bonded, the metal mesh in the bent portion There was a problem that the heat transfer is not good because of damage. Even in this case, such a heat pipe has a problem of low working fluid movement force due to capillary action.

Due to these problems, recently, a wick having a relatively good working fluid movement force due to a capillary phenomenon is used, and a heat pipe using a wick in which a metal powder is sintered on an inner wall of a pipe is used. In the sintered metal powder of this type of wick, fine pores are present in the sintered metal powder, so that the working fluid movement force is relatively good due to the capillary action through these pores, so that the heat pipe is relatively good. Its disadvantage is that its manufacturing process is more complicated and its manufacturing cost is higher than that of a heat pipe, and its weight is too heavy.

Accordingly, an object of the present invention is to use a new type of wick which is completely different from the conventional wick, and the manufacturing process of the heat pipe using dense grooves and / or fine metal meshes or a combination of the two is difficult and has high manufacturing cost. The wick structure heat pipe using sintered powder metal has a relatively good working fluid movement force due to capillary action, but the manufacturing process is complicated, the price increases, and the weight becomes heavy. The lightweight and easy-to-process wick structure is improved to provide a heat pipe with excellent thermal conductivity.

The invention is now described in more detail with the accompanying drawings.

2 to 4 show the structure of the heat pipe 10 according to the present invention and its manufacturing method.

The heat pipe 10 includes a hollow metal pipe 11 in which both ends 11a and 11b are sealed in a vacuum state, a wick 12 attached to an inner wall of the metal pipe 11, and a hollow pipe 11 inside the hollow pipe 11. Filled working fluid.

In the method for manufacturing the heat pipe 10, first, one end 11a of the hollow metal pipe 11 is sealed by condensation, and then the wick 12 is attached to the inner wall of the pipe 11 (Fig. 2). ). After that, the end 11b is conduited (FIG. 3), and the closing portion 16 is formed in the injection tube 14 while injecting the working fluid through the injection tube 14 on the opposite end 11b under vacuum. The closure 16 is sealed with a closure 18 to produce a heat pipe 10 (FIG. 4). Although each end 11a, 11b of the hollow metal pipe 11 was closed in a axial manner, this is described as an example, and it is also possible to close the end in other ways. For example, it is also possible to close to one end or both ends using a metal plug by welding or gluing.

Since heat transfer of the heat pipe 10 is made through the pipe wall of the metal pipe 11, the hollow metal pipe 11 is excellent in thermal conductivity and copper which can sufficiently withstand the pressure inside the sealed heat pipe and its long time use. Manufactured from iron, aluminum and stainless steel, but mainly using copper pipes a lot.

The wick 12 uses materials such as PVA sponge or pulp of light weight and excellent capillary effect, cotton fabric, chemical fiber, nonwoven fabric (eg, nonwoven polyester), and polyurethane foam. In particular, the PVA sponge is made of water-soluble PVA dissolved with an acid catalyst, and has a large number of pores which are completely interconnected three-dimensionally. These PVA sponges and pulp type wicks are shrunk to a dry state in a dry state, and are easily inserted into the pipe 11, and when the working liquid is injected after insertion, they are properly inflated to naturally adhere to the inner wall surface of the pipe 11. Done. In addition, since the heat resistance is strong when wet with the working liquid, it generally does not interfere with the operation of the heat pipe at a temperature of 150 ° C. or lower, and even when the straight heat pipe 10 is bent, unlike the wick of the metal mesh, The wick 12 of the PVA sponge and pulp type is softly bent and not damaged to facilitate the manufacture of various types of heat pipes. The wick material used in the present invention will be described later in more detail with examples.

The working fluid is a liquid such as ammonia, freon, methanol, water, organic medium (acetone), which has excellent vaporization. Working fluids are classified as shown in the table below, depending on their operating temperature range and their compatibility with the vessel material.

Working temperature (℃) Working fluid Compatibility with container material (○: suitable Ｘ: unsuitable) iron Copper aluminum Stainless steel -60 to 50 ammonia ○ Ｘ ○ ○ -40 to 120 Freon ○ ○ ○ 10 to 30 Methanol ○ Ｘ Ｘ 30 to 200 water Ｘ ○ Ｘ Ｘ 150 to 300 Organic medium ○ ○ ○

The sealing portion 18 may be attached by sealing a metal or plastic cap with an adhesive, or may be sealed with PVC, bakelite, Teflon, or the like.

5-7 show various forms in which the wick 12 is attached to the inner wall of the pipe 11. According to this, the wick 12 is attached to the inner wall of the pipe 11 by one winding (Fig. 5), about two windings (Fig. 6), or a partial winding (Fig. 7). The outer diameter of the heat pipe is 3 mm to 20 mm. The inner diameter changes according to the outer diameter of the heat pipe. When the inner diameter is small, the winding of the wick is less than 1/4 to less than one time to secure a sufficient evaporation gas passage path. On the contrary, when the inner diameter of the heat pipe is large, the winding is performed once or twice.

In addition, although the wick 12 may be attached over the entire length in the longitudinal direction depending on the use of the heat pipe, it is also possible to partially attach the wick 12 to the heating portion. That is, in the case of a 1 m heat pipe, it is only partially attached to the point of 10 to 200 mm from the heating site. 1, the working fluid evaporated when the heat pipe is used so that one end 11a of the metal pipe 11 where the external heat source is present is located lower than the other end 11c. This is possible because heat transfer can be achieved by natural convection. Thereby, the work at the time of manufacture is easy and an economic burden can be reduced. In the case of using as a whole, unlike the case described above, the heat pipe is used so that the heat source is located in the upper or horizontal plane. It is also possible to use the wick material of the present invention together with a conventional metal mesh. That is, although the metal mesh is less absorbent and capillary force as compared to the PVA sponge of the present invention, the movement fluid of the working fluid is low, but the heat resistance is excellent, so the heat source site is about 10 to 200 mm to form the wick with the metal mesh and the rest It is also possible to use the PVA sponge etc. of this invention for a part.

(Example 1)

In order to compare and test the operating performance of the heat pipe according to the present invention and the conventional heat pipe, a winding of 110 cm in the inner wall of the copper pipe having an inner diameter of 110 mm, an outer diameter of 127 mm and a length of 110 cm Temperature and heat transfer time tests were performed using heat pipes with attached PVA sponge wicks and conventional metal mesh. The working fluid used about 6% methyl alcohol relative to the total volume inside the pipe. At atmospheric conditions with an atmospheric temperature of 23 ° C. and a humidity of 65%, the length of each heat pipe exposed to the heat source is about 10 cm as shown in FIG. 8, and 0.1 m, 0.5 m, 1 from the heat source to each heat pipe. The m point was marked, the heat pipe was kept horizontal, and the heat source was water at 60 ° C., and the temperature at each point from 10 to 60 seconds in 10 seconds was measured over time. As a result, as shown in the diagram shown in Fig. 9, the heat pipes using the PVA sponge wicks of this application had always had a high temperature at each point, compared to the heat pipes using the metal mesh wicks, and the first 40 In seconds, a significant temperature difference remains. According to this, the heat pipes of the present invention resulted in an excellent increase in heat transfer efficiency when compared to the conventional one.

(Example 2)

In Example 2, a heat pipe using a conventional metal mesh and a heat pipe using various materials of the present invention were tested under the same conditions as in Example 1 to perform a comparative experiment, but the temperature after 60 seconds at each point was measured. The temperature deviation between the 1 m point and the 0.1 m point was calculated. The results are shown in the table below.

Wick material Contact temperature (℃) Temperature at each measuring point (° C)  Temperature range (℃) 0.1 m 0.5 m 1 m Metal mesh 60 47.0 44.2 42.3 4.7 PVA Sponge 60 52.8 51.2 49.6 3.2 pulp 60 52.4 50.7 48.8 3.6 dismission 60 52.2 50.4 48.4 3.8 Chemical Fiber (Nylon) 60 48.6 47.6 44.2 4.4 Foamed polyurethane 60 48.2 46.5 43.7 4.6 Nonwoven polyester 60 47.3 45.4 43.0 4.3

According to this, it turns out that the PVA sponge etc. which are the wick material by this invention have the outstanding heat transfer effect compared with a metal mesh.

Conventional capillary heat pipes have a problem that the manufacturing process is complicated, heavy and expensive mainly using metal mesh or sintered metal powder, but in the present invention, as described above, by using a light and inexpensive material of a porous material Not only is the process simpler than the technique, but also has good bendability, and the movement of the working fluid due to the osmotic phenomenon is increased, so that the heat transfer effect is much better, and the weight and economy are also excellent.

Claims (6)

A hollow metal pipe 11 whose both ends 11a and 11b are sealed in a vacuum state; A lightweight porous wick 12 having excellent capillary action attached to the inner wall of the hollow metal pipe 11; In the configuration consisting of a working fluid filled in the hollow metal pipe 11, After the injection pipe 14 is formed at the end portion 11b of the hollow metal pipe 11, the closing pipe 16 is formed in the injection pipe 14 to be sealed by the sealing part 18. The wick (12) attached to the inside of the (11) is composed of cotton direct current made of natural fibers, the wick (12) is wound one to two times on the inner wall of the hollow metal pipe (11) having a large inner diameter to overlap Heat pipe characterized by the above-mentioned. delete delete delete delete delete

Images