JPH07208884A - Plate type heat pipe - Google Patents

Abstract

PURPOSE:To provide a plate type heat pipe capable of being efficiently actuated even in the case of a top heat mode. CONSTITUTION:A first wick 13 having a strong capillary force is formed into a block shape, and a plurality of first wicks are radially disposed so that slits 15, which serve as vapor paths, are formed around the bock-shaped first wicks. Second wicks 14 having a comparatively weak capillary force are mounted in the boundaries among the surfaces of the block-shaped first wicks 13 and two inner faces of a container 12, which are opposed to each other. Accordingly, a heat pipe is efficiently actuated even in the case of a top heat mode, and a supply path of a working fuild L to a condensing part 11b is secured even in the case where bubbles are generated in the aforesaid boundaries, so that the capability of heat transport is prevented from being reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat plate heat pipe in which one of two opposing inner surfaces of a flat plate container is an evaporation section and the other is a condensation section.

[0002]

2. Description of the Related Art A general flat plate heat pipe 1 is shown in FIG.
As shown in FIG. 2, of the two inner surfaces of the hollow flat plate-shaped heat pipe container 2 which are opposed to each other in the vertical direction, the lower side surface on which the heating element H is attached is the evaporation section 1a, and the upper side surface is the condensation section 1a.
b, the vapor 3a of the working fluid 3 which is heated and evaporated in the lower evaporation section 1a moves to the upper condensation section 1b. Then, in the condensing portion 1b, the working fluid 3 that releases the latent heat that has been transported and is condensed and returned to the liquid phase is returned to the lower evaporation portion 1a by the action of gravity.

[0003]

However, in the conventional flat plate heat pipe described above, most of the working fluid 3 condensed in the condenser portion 1b is the heat pipe container 2.
Since it flows down along the inner surface of the side wall 2a of the above and returns to the evaporation section 1a, the vicinity of the peripheral edge where this condensed working fluid flows down is covered with the condensed working fluid so that the function as the condensation section 1b can be fulfilled. There is a problem that the temperature of the peripheral portion of the condenser portion 1b becomes low and the temperature distribution of the evaporation portion 1a becomes non-uniform due to the influence of the temperature. As a result, the heat flux at the peripheral portion of the evaporation unit 1a becomes smaller than the heat flux near the center of the evaporation unit. There is a problem that the cooling action differs between the parts.

FIG. 5 shows a case in which the heating element H is provided on the upper side of the conventional flat plate heat pipe 1. In this case, the upper side on which the heating element H is provided serves as an evaporation part, but the upper side Since the means for supplying the working fluid 3 to the evaporation portion 1a is not provided, the evaporation portion 1a is in a dry-out state, does not operate as a heat pipe, and therefore cannot obtain the cooling action.

An object of the present invention is to provide a flat plate type heat pipe capable of operating the heat pipe regardless of which of the two inner surfaces facing each other in the vertical direction is the evaporation portion.

[0006]

As a means for solving the above problems, the present invention provides a liquid passage by a capillary force between two vertically opposed inner surfaces in a hollow flat plate heat pipe container. In the flat plate heat pipe having the wick disposed therein, the wick includes a first wick that generates a high capillary force and a second wick that generates a capillary force lower than the first wick. In addition to being formed in a block shape, a plurality of them are arranged so as to be spaced apart so as to form a void to be a vapor passage around them, and between the block-shaped first wick and the two inner surfaces of the container, It is characterized in that the second wicks are respectively interposed.

[0007]

As described above, in the flat plate heat pipe, the first wick having a high capillary force and the second wick having a capillary force lower than the first wick are provided between the two inner surfaces facing each other in the vertical direction in the heat pipe container. The wick consisting of the wick serves as a liquid passage and supplies the working fluid in the liquid phase to the evaporation section in the top heat mode, and in the bottom heating mode, the working fluid returned to the liquid phase in the condensation section to the evaporation section. The vapor of the working fluid, which is made to flow down and heated in the evaporation section, moves to the condensation section via the void formed around the block-shaped wick. Further, since the first wick is in contact with the inner surface of the heat pipe container via the second wick having a weak capillary force, the working fluid can pass even if bubbles are generated between the block wick and the inner surface of the container. Therefore, the working fluid can be supplied to the condenser. Therefore, whether the heating element is on the lower side or the upper side of the flat plate heat pipe, that is, the heat pipe operates equally in the top heat mode and the bottom heat mode, and the decrease in heat transport capacity due to the generation of bubbles is prevented. To be done.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment in which the flat plate heat pipe of the present invention is used as a cooling device for a large scale integrated circuit (LSI) will be described below with reference to FIGS.

The flat plate type heat pipe 11 includes a hollow flat plate type container 12 in which a fine mesh metal net is vertically bundled into a rectangular parallelepiped and has a strong capillary force. And a second wick 14 having a relatively weak capillary force. This second wick 14
Are arranged in close contact with the entire two inner surfaces of the container 12 which are opposed to each other in the vertical direction, and the first wick 13 formed in a rectangular parallelepiped has the second wick 1
A space 1 that is sandwiched from above and below by 4 and serves as a steam passage.
5 are arranged radially so as to be formed in the periphery.

The flat plate type heat pipe 11 is manufactured by inserting it into a container 12 having one side open, sandwiching the first wick 13 from above and below with the second wicks 14, 14, and then degassing. After closing the hole (not shown) and vacuuming the inside of the container 12, a predetermined amount of condensable working fluid is injected and the gas vent hole is closed to complete the process.

Next, the operation of this embodiment configured as described above will be described with reference to FIG. 2. In the flat plate heat pipe 11 which is a cooling device, the LSI which is the heating element H is mounted on the upper surface. Therefore, the so-called top heat mode in which the upper surface serves as the evaporation portion 11a is set. Therefore, the heating element H
When the temperature rises, the heat is generated by the flat plate heat pipe 11
Is transmitted to the upper surface of, and this upper surface becomes the evaporation portion 11a. When the liquid-phase working fluid L accumulated in the lower part of the container is sucked up by the capillary force of the first wick 13 and the second wick 14 and supplied to the evaporation section 11a, the working fluid L supplied to the evaporation section 11a. Is heated and boils,
It becomes the working fluid V in the vapor phase.

At this time, even if the working fluid L boils on the surface of the evaporation portion 11a and bubbles are generated, a relatively weak capillary force is generated between the fine first wick 13 and the inner surface of the evaporation portion 11a. Since the two wicks 14 are interposed, the evaporation unit 1
The supply path of the working fluid L to 1a is secured, and the reduction of the heat transport capacity can be prevented.

Then, the working fluid V which has become a vapor phase in the evaporation section 11a moves to the condensation section 11b via the void 15 around the first wick 13, and is deprived of heat in the condensation section 11b and condensed. And returns to the liquid-phase working fluid L and accumulates below. In this way, even in the so-called top heat mode in which the evaporation section 11a is located above the condensation section 11b, the working fluid circulates smoothly and operates as a heat pipe, so that the heating element H can be efficiently cooled. it can.

Further, since the first wicks 13 are radially arranged as described above and the voids 15 serving as vapor passages are formed around each of the first wicks 13, vaporization is carried out in the evaporation section 11a. The working fluid V is
It is easy to diffuse over the entire area b, so that the flat plate heat pipe 11 can be uniformly heated.

Therefore, the heat flux at the peripheral portion of the evaporation portion 11a of the flat plate heat pipe 11 is the same as the heat flux near the center of the evaporation portion, and when the cooling device is used, the entire flat plate heat pipe 11 is uniform. Since it has a good cooling effect, LS
It is possible to increase the mounting density of the heating elements H such as I.

As shown in FIG. 3, the heating element H is L.
When the SI is attached to the lower surface of the flat plate heat pipe 11, the so-called bottom heat mode in which the lower surface serves as the evaporation portion 11a is set. Therefore, when the temperature of the heating element H rises, the lower surface of the flat plate type heat pipe 11 is moved to the evaporation portion 11a.
Then, the liquid-phase working fluid L accumulated in the lower part of the container is heated to become the vapor-phase working fluid V, which moves to the upper condensing part 11b via the void 15 around the first wick 13 and then to the condensing part 11b. At, the heat is taken away to condense and return to the liquid-phase working fluid L, flow down through the first wick 13 and the second wick 14, and return to the lower evaporation section 11a.

Therefore, the working fluid L returned to the liquid phase in the upper condensing section 11b travels through the first wick 13 and the second wick 14 which are radially arranged at a substantially uniform density, and the lower evaporating section 11a. Of the flat plate type heat pipe 11, so that the whole of the evaporation portion 11a of the flat plate heat pipe 11 is soaked. Therefore, when the cooling device is used, the entire flat plate-shaped heat pipe 11 has a uniform cooling action, so that the packaging density of the heating elements H such as LSI can be increased.

In this embodiment, as the first wick 13 and the second wick 14, metal nets bundled or stacked are used, but felt, non-woven fabric, porous ceramics or sintered metal may be used in addition to the metal nets. Materials with similar capillary forces can be used, such as. In particular, if a material having high compressive strength such as a porous ceramic or a sintered metal is formed into a block shape and used as the first wick, it is possible to prevent the container from being deformed by negative pressure.

[0019]

As described above, in the flat plate heat pipe of the present invention, as the wick which constitutes the liquid passage by the capillary force, the first wick which generates a high capillary force and the capillary force lower than the first wick. And a plurality of second wicks for generating the vapor are formed in a block shape, and a plurality of the first wicks are arranged so as to be spaced apart so as to form a vapor passage around the first wick. Since the second wicks are respectively interposed between the 1 wick and the two inner surfaces of the heat pipe container, the heat pipe can be operated in the top heat mode, and the first wick and the inner surface of the heat pipe container can be connected to each other. By the second wicking action interposed at the boundary, even if bubbles are generated at the boundary, the working fluid supply path can be secured, and the heat transport capacity is low. It is possible to prevent.

[Brief description of drawings]

FIG. 1 is a cross-sectional plan view of an embodiment of a flat plate heat pipe of the present invention.

FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1 showing a flat heat pipe in a top heat mode.

FIG. 3 is a sectional side view of a flat plate heat pipe in a bottom heat mode.

FIG. 4 is a cross-sectional side view of a conventional bottom heat mode flat plate heat pipe.

FIG. 5 is a sectional side view showing a dry-out state in a top heat mode in a conventional flat plate heat pipe.

[Explanation of symbols]

11 ... Flat plate heat pipe, 11a ... Evaporating section, 11
b ... condensation part, 12 ... container, 13 ... 1st wick, 14 ... 2nd wick, 15 ... gap.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Masuko 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Ltd. (72) Inventor Hitoshi Hasegawa 1-1-5, Kiba, Koto-ku, Tokyo Shareholders In Fujikura Ltd. (72) Inventor Michio Takaoka 1-5-1 Kiba, Koto-ku, Tokyo Fujikura Ltd. (72) Inventor Mikiyuki Ono 1-1-5 Kiba, Koto-ku, Tokyo Incorporated Fujikura Ltd.

Claims (1)

[Claims] 1. A flat plate heat pipe in which a wick forming a liquid passage due to a capillary force is disposed between two inner surfaces facing each other in a vertical direction in a hollow flat plate heat pipe container, wherein the wick is a high capillary tube. It is composed of a first wick that generates a force and a second wick that generates a capillary force lower than the first wick. The first wick is formed in a block shape, and a void serving as a vapor passage is formed around the block. In addition to arranging a plurality so as to be separated,
A flat plate heat pipe, characterized in that the second wicks are respectively interposed between the block-shaped first wick and the two inner surfaces of the container.