JP2001296093A - Heat pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat pipe in which a good heat transfer property can be stably obtained even when it is disposed in a substantially horizontal position. SOLUTION: The heat pipe has minute grooves provided on its inner surface and working fluid sealed therein. The minute grooves comprise one or a plurality of spiral minute grooves or a plurality of loop shaped minute grooves inclined in one longitudinal direction of the pipe 2. When the working fluid condensed in a heat radiating part moves to a heat generating part, it receives the action of gravity on both the surfaces C and D in the inner surface of the heat pipe 2, so that the working fluid smoothly moves to the heat generating part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat pipe particularly suitable for cooling electronic equipment.

[0002]

2. Description of the Related Art In recent years, electronic devices have been improved in performance and density, and the amount of heat generated has increased. In order to use such an electronic device with high performance and long life, it is necessary to dissipate the heat using a fan or a heat pipe.

The heat pipe is a pipe in which a working fluid is sealed under reduced pressure in a pipe. When one end of the pipe is brought into contact with a heating section, the working fluid absorbs heat from the heating section and becomes steam, and the steam is cooled at the other end. It condenses and moves to the heating part side. The heating section is cooled by repeating the evaporation and condensation of the working fluid. In such a heat pipe, in order to quickly return the condensed working fluid to the heat generating portion side of the heat pipe by utilizing the capillary phenomenon, a mesh-like copper plate is attached to the inner surface of the pipe, or a fine spiral groove is provided. I have.

[0004]

However, the heat pipe to which the mesh copper plate is attached has a drawback that when the heat pipe is bent and mounted in a narrow electronic device, the mesh copper plate is peeled off. On the other hand, the heat pipe provided with the spiral groove has little damage due to bending, but has a problem that sufficient heat transfer characteristics cannot be obtained when the heat pipe is installed in a horizontal or nearly horizontal state. The present inventors have studied a remedy for the above problem, and when the heat pipe is installed in a horizontal or nearly horizontal state, the reason why a conventional heat pipe provided with a spiral groove cannot provide sufficient heat transfer characteristics. Clarified.

That is, the conventional heat pipe is shown in FIG.
As shown in the perspective view of FIG. 5, a fine spiral groove 9 is provided on the inner surface of the pipe 2. On the C surface (see FIG. 5A), as shown in FIG. The condensed hydraulic fluid on the spiral groove 9 is inclined in the direction of descending toward the heat generating portion, and the condensed hydraulic fluid smoothly moves to the heat generating portion under the action of gravity. As shown in FIG. 5 (c), the spiral groove 9 is inclined in a direction in which the condensing hydraulic fluid on the spiral groove 9 climbs toward the heat-generating portion, that is, in a direction against gravity, and Was found to be difficult to move to the heating part side. The hydraulic fluid dropped on the lower surface B of the pipe has no resistance in the spiral groove 9 on the surface D because the spiral groove 9 faces the heat generating portion, but the spiral groove 9 is opposite to the heat generating portion on the surface C. It has been found that the spiral groove 9 becomes a resistance to the flow because it is directed in the direction of, and becomes a cause of obstructing the flow of the hydraulic fluid. Based on these findings, the present inventors have further studied and completed the present invention. An object of the present invention is to provide a heat pipe capable of stably obtaining good heat transfer characteristics even when installed in a horizontal or nearly horizontal state.

[0006]

According to the first aspect of the present invention,
In a heat pipe in which a fine groove is provided on an inner surface of a pipe and a working fluid is sealed therein, the fine groove is formed in one or a plurality of spiral fine grooves or a plurality of loops inclined in one direction in a length direction of the pipe. A heat pipe characterized by being a fine groove.

The invention according to claim 2 is the heat pipe according to claim 1, wherein a grooveless portion having a predetermined width is provided in a length direction of the pipe.

The invention according to claim 3 is the heat pipe according to claim 1 or 2, wherein an inclination angle of the fine groove with respect to a length direction of the pipe is 5 to 50 degrees.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. FIGS. 1A and 1B show a first embodiment of a heat pipe of the present invention. FIG. 1A is a perspective view, FIG. 1B is an explanatory view of a loop-shaped fine groove on a C plane viewed from the front, and FIG. It is explanatory drawing of a fine groove. In the heat pipe 1a, the fine grooves on the inner surface of the pipe are a plurality of loop-shaped fine grooves 3 inclined in one direction in the length direction of the pipe, and the working fluid is sealed inside the pipe 2. This heat pipe 1
Installed in a horizontal or nearly horizontal state, one side in the length direction (the side in the direction in which the loop-shaped fine groove is inclined) is used as a heat radiator, and the bottom (B) in the other direction is used as a heat generator. When arranged and used, the hydraulic fluid condensed on the loop-shaped fine grooves 3 of the heat radiating portion is subjected to gravity on both the C surface and the D surface of the inner surface of the heat pipe when moving to the heat generating portion side (the side in the other direction). Under the action, the condensed working fluid smoothly moves to the heat generating portion side, and the working fluid dropped on the lower surface B of the heat pipe 1 has the loop-shaped fine grooves 3 on both surfaces C and D facing the heat generating portion side. The flow of the hydraulic fluid to the heat generating portion is not obstructed. Therefore,
Good thermal conductivity is stably obtained.

FIG. 2 shows a heat pipe according to a second embodiment of the present invention. FIG. 2A is a perspective view, FIG. 2B is an explanatory view of a spiral fine groove on the C plane viewed from the front, and FIG. It is explanatory drawing of the spiral fine groove | channel. In the heat pipe 1b, the fine grooves on the inner surface of the pipe are a plurality of spiral fine grooves 4 inclined in one direction in the length direction of the pipe, and the working fluid is sealed inside the pipe 2. When the heat pipe 1b is installed in a horizontal or nearly horizontal state and used,
As in the case of the heat pipe shown in (1), good heat transfer characteristics can be stably obtained.

FIG. 3 is a developed view of an inner bottom surface showing a third embodiment of the heat pipe of the present invention. This heat pipe 1
c shows a grooved portion 5 provided at the bottom of the pipe shown in FIG. 1 with a predetermined width in the length direction of the pipe 1c. In the heat pipe 1c, the condensed working fluid moves more smoothly through the grooveless portion 5 to the heat generating portion. Heat pipe 1 shown in FIG.
Also in b, the same effect can be obtained by providing a grooveless portion at the bottom of the pipe inner surface. It is desirable that the smoother the surface of the grooveless portion, the more the hydraulic fluid moves.

The width of the grooveless portion 4 is preferably about 5 to 10% of the inner circumferential length of the pipe. If the width is less than 5%, the effect cannot be sufficiently obtained. The effect cannot be obtained sufficiently. If the straight groove is formed by excavating the grooveless portion 4, the hydraulic fluid can move more easily. If the straight groove is provided with a taper that becomes deeper toward the heat generating portion, the effect is further increased.

In the present invention, the inclination angle .theta.
50 degrees is desirable. Any material having excellent conductivity, such as copper or aluminum, can be used for the pipe. The cross-sectional shape of the pipe is arbitrary such as a circle, an ellipse, and a square. The heat pipe of the present invention can be easily manufactured by a method such as extrusion using a core or a method in which predetermined fine grooves are formed in a plate material and then processed into a cylindrical shape by electric sewing. The non-groove portion may be formed by removing a fine groove at a predetermined position after the formation of the fine groove. However, a method in which the fine groove at the bottom of the inner surface of the pipe is not formed in advance is preferable because the number of steps is small.

[0014]

The present invention will be described below in detail with reference to examples. (Example 1) A fine groove having a predetermined shape is formed in a copper strip having a thickness of 0.5 mm by a rolling method, and then the copper strip is rounded into a cylindrical shape with the fine groove forming surface inside, and an edge portion is formed. A round pipe having an outer diameter of 10 mm was formed by electric resistance welding. After water (hydraulic fluid) was injected into the pipe, both ends were welded while reducing the pressure inside. Next, the pipe was pressed in the vertical direction to produce a heat pipe having a flat cross section with a height of 6 mm, a width of 9 mm, and a length of 300 mm, in which a loop-shaped fine groove was provided on the inner surface inclined in one direction of the pipe. The inclination angle of the fine groove is 3 to
Various changes were made in the range of 60 degrees.

(Embodiment 2) The center of the bottom of the inner surface of the pipe has a width of 2
A heat pipe was manufactured in the same manner as in Example 1 except that a grooveless portion having a diameter of about 7% of the inner circumferential length of the pipe (about 7% of the inner length of the pipe) was provided in the length direction of the pipe. The non-groove portion was provided at the stage of rolling the fine groove.

Example 3 A heat pipe was manufactured in the same manner as in Example 1, except that the fine grooves were formed as spiral fine grooves inclined in one direction of the heat pipe shown in FIG.

Example 4 A groove was not formed at the bottom of the inner surface of the pipe by the same method as in Example 2 except that the fine groove was a spiral fine groove which was provided to be inclined in one direction of the heat pipe shown in FIG. The heat pipe provided with the section was manufactured.

The critical heat transport rate of each of the heat pipes manufactured in Examples 1 to 4 was measured by the following method. That is, as shown in FIG.
a is cooled by a fan 7 on one side, and a plate-shaped heater (heating unit) 6 is adhered to the bottom of the pipe inner surface on the other side, and the temperature of the plate-shaped heater 6 is maintained while maintaining the working fluid temperature at 50 ° C. The amount of heat generated and the amount of cooling of the fan 7 were increased, and the amount of heating of the plate heater 6 immediately before the heat pipe 1a stopped operating due to a rapid rise in the temperature of the heat generating portion was defined as the critical heat transport amount. . During the measurement, the heat was sufficiently insulated so that there was no heat radiation other than the heat radiation part. For comparison, the same measurement was performed on a conventional heat pipe having a mesh copper plate adhered to the inner surface of the pipe and a heat pipe having fine spiral grooves formed on the inner surface of the pipe (see FIG. 5). Table 1 shows the results. In addition, the critical heat transport amount is shown as a ratio when the critical heat transport amount of a conventional heat pipe in which a mesh-like copper plate is adhered to the inner surface of the pipe is set to 1.

[0019]

[Table 1]

As is clear from Table 1, N of the present invention example
o. In all of Nos. 1 to 11, the critical heat transport amount exceeded the conventional heat pipe. The pipes provided with a grooveless portion at the bottom of the inner surface of the pipe (Nos. 9 and 11) showed a further increase in the critical heat transfer rate.

[0021]

As described above, in the heat pipe of the present invention, a plurality of loop-shaped fine grooves or one or a plurality of spiral fine grooves are inclined in one direction in the length direction of the heat pipe on the inner surface of the pipe. Since the heat pipe is provided with the heat pipe, one side of the heat pipe is arranged in the heat radiating portion, and the bottom of the other side is arranged in the heat generating portion, so that the heat pipe is horizontal or nearly horizontal. Even if used in the state,
The hydraulic fluid condensed in the heat radiating part is smoothly moved to the heat generating part side by the action of gravity on both sides of the heat pipe, and the hydraulic fluid dropped on the lower surface of the heat pipe 1 has the loop-shaped fine grooves 3 on both sides. Since it is directed to the heat generating portion side, the flow of the working fluid to the heat generating portion side is not obstructed. Further, by providing a predetermined width in the length direction of the grooveless portion at the bottom of the inner surface of the pipe, the condensed working fluid moves more smoothly to the heat generating portion side. Therefore, the heat pipe of the present invention has excellent heat transfer characteristics even when used in a horizontal or nearly horizontal state, and has an industrially significant effect.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a heat pipe of the present invention, FIG. 1 (b) is an explanatory view of a loop-shaped fine groove on a C plane viewed from the front, and FIG. It is explanatory drawing of a loop-shaped fine groove.

FIG. 2 is a perspective view showing a second embodiment of the heat pipe of the present invention, FIG. 2 (b) is an explanatory view of a spiral fine groove on a C plane viewed from the front, and FIG. It is explanatory drawing of a spiral fine groove.

FIG. 3 is a developed view of a bottom portion of an inner surface of a heat pipe according to a third embodiment of the present invention.

FIG. 4 is an explanatory diagram of a method for measuring a critical heat transport amount of a heat pipe.

5 (a) is a perspective view of a conventional heat pipe, FIG. 5 (b) is an explanatory view of a fine spiral groove on the C-plane viewed from the front, and FIG.
It is explanatory drawing of the fine spiral groove on a surface.

[Explanation of symbols]

 1a, b, c Heat pipe 2 of the present invention 2 Pipe 3 Loop-shaped fine groove provided in one direction inclined 4 Spiral fine groove provided in one direction inclined 5 No groove provided at bottom of pipe inner surface Part 6 Plate heater 7 Fan 8 Conventional heat pipe 9 Fine spiral groove

Claims (3)

[Claims] 1. A heat pipe in which a fine groove is provided on an inner surface of a pipe and a working fluid is sealed therein, wherein the fine groove on the inner surface of the pipe has one or more spirals inclined in one direction in a length direction of the pipe. A heat pipe comprising a plurality of loop-shaped fine grooves or a plurality of loop-shaped fine grooves. 2. The heat pipe according to claim 1, wherein a grooveless portion having a predetermined width is provided in a length direction of the pipe. 3. The heat pipe according to claim 1, wherein an inclination angle of the fine groove with respect to a length direction of the pipe is 5 to 50 degrees.