JPS5945913B2 - heat pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat pipe in which one end of a sealed pipe sealed with a working fluid is used as a heating part and the other end is used as a cooling part, for example, a heat pipe that is used by rotating around a central axis ( In particular, it relates to heat pipes for cooling rotating electric machines (so-called rotary heat pipes).

This type of conventional heat pipe is constructed as shown in FIGS. 1 and 2.

FIG. 1 shows a heat pipe with a uniform inner diameter, and FIG. 2 shows a tapered tube heat pipe in which the inner diameter of the cooling section is tapered such that it expands in the direction of the heating section.

In both figures, 1 is a pipe whose both ends are sealed, and 2 is an appropriate amount of hydraulic fluid sealed inside the pipe.

The inside of the pipe 1 is filled with a working fluid 2 and its saturated steam.

One end of the pipe 1 functions as a power heating section 3, and when heat is generated in this power heating section 3, the working fluid there evaporates, and the cooling section constructed at the other end of the pipe 1 is heated. 4, the steam moves at high speed to the cooling section 4.

The steam that has moved to the cooling section 4 condenses on its inner wall, where it releases latent heat of vaporization.

In this way, heat is transferred from the heating section 3 to the cooling section 4 as latent heat through evaporation, movement, and condensation of the working fluid, so that unlike normal solid heat conduction, a large heat flux is obtained.

The working fluid 2 condensed in the cooling section 4 is subjected to a force loss by the smoothing effect of centrifugal force during rotation (in the case of a horizontal type) or gravity in the heat pipe shown in Fig. 1, and by centrifugal force in the heat pipe shown in Fig. 2. It is returned to the heating section 3, where it repeats evaporation and condensation, creating a closed circulation circuit.

In such a heat pipe, when the heat pipe is rotated, the working fluid is evaporated in the heating section 3 or condensed in the cooling section 4 via a liquid layer thickly stuck to the inner wall of the pipe 1 due to centrifugal force. Therefore, the thermal resistance of the heating section 3 or the cooling section 4 increases, resulting in a decrease in the heat transfer coefficient.

Generally, the thicker the liquid layer and the larger the heat flux, the smaller the heat transfer coefficient becomes, and the temperature difference between the heating section 3 and the cooling section 4 also increases.

In order to obtain a predetermined heat transfer performance under such conditions, a larger and heavier heat pipe is required.

It is an object of the present invention to provide a heat pipe of the type mentioned at the beginning, which does not have these drawbacks, has good heat transfer properties, is small, lightweight, and can be manufactured at low cost.

In order to achieve this object, the present invention includes inserting an inner fin having a gear-shaped cross section into the cooling part of the sealed pipe concentrically with the sealed pipe in a state of good thermal conductivity. It is characterized by:

With this configuration, the effective area of the condensing section increases, the liquid layer thickness becomes thinner, and the heat transfer coefficient increases, thereby achieving the improvement in heat transfer performance.

Hereinafter, an embodiment in which the inner fin according to the present invention is provided only in the cooling section will be described in detail with reference to the drawings.

FIG. 3 shows an embodiment of the present invention.

The basic structure of this heat pipe is the same as the conventional one already described, and consists of a sealed pipe 1 with an appropriate amount of working fluid 2 sealed inside the pipe 1. be satisfied.

One end functions as a heating section 3, and the other end functions as a cooling section 4.

In the cooling section 4 of the heat pipe having such a basic structure, according to the present invention, an inner fin 5 having a gear-shaped cross section is provided concentrically with respect to the pipe 1 and in a state of good thermal conductivity. For example, it is inserted and arranged by means such as shrink fitting or press fitting.

Then, end plates or shaft ends are hermetically joined to both ends of the pipe 1 by welding, brazing, or the like.

Examples of the cross-sectional shape of the inner fin 5 are shown in FIGS. 4-6.

The inner fin 51 in FIG. 4 and the inner fin 52 in FIG. It is of a type in which the part collectively known as the southern part is expanding.

The inner fin 51 shown in FIG. 4 has a flat plate shape at its southern part, and the inner fin 52 shown in FIG. 5 has a parallel slit-shaped space formed between the teeth.

The inner fin 53 shown in FIG. 6 is referred to as an internal gear type in the present invention, and a common connecting portion is located on the outer circumferential side, from which toothed portions protrude radially inward. The part is formed as a space.

By providing the inner fins 5, the effective heat transfer area of the cooling section 4 is increased.

For example, in the case of the inner fin 52 shown in FIG. 5, the effective area of the condensing part of the cooling part 4 is 2.7 times (geometrically, 3 As a result, the liquid layer thickness in the condensing section decreased to about 1/2.7 (the heat flux became smaller), and the condensing heat transfer coefficient increased by about 1.5 times. .

As a result, the apparent condensation heat transfer coefficient is 2.7XI,5.
We were able to improve this by 4 times.

When centrifugal force due to shaft rotation acts on the P1-pipe into which inner fins 5 having a gear-shaped cross section are inserted, the working fluid gradually flows from the center of the inner fins 5 to the side with a larger diameter, causing the fluid to flow. The layer also gradually becomes thicker, and the liquid collects on the outermost diameter side.

This collected liquid is returned to the heating section 3 by the smoothing action of centrifugal force.

In this case, the inner fins 5 can not only increase the condensation area but also thin the liquid layer on the surface of the inner fins, thereby improving heat transfer performance.

The material of the inner fin 5 is determined by the coefficient of thermal expansion of the pipe 1.
It is desirable that the material be the same as that of the material.

However, if the materials are different, for example, if the material of the inner fin 5 has a larger coefficient of thermal expansion than the material of the pipe 1, the inner fin 54. ! By providing slits 64 and 65 in the axial direction with respect to 155 with a width W equal to or less than the number of slits 64 and 65, thermal expansion to the extent possible can be released.

Although the embodiment shown in FIG. 4 shows the integral inner fin 5, this is divided into a plurality of pieces in the axial direction as shown in FIG. You may.

This also makes it possible to achieve the same effect as that shown in FIG.

In the above embodiments, a rotary type heat pipe that utilizes centrifugal force due to shaft rotation has been described, but the present invention can also be applied to a gravity type heat pipe that uses gravity to return liquid from a cooling section to a heating section.

As described above, according to the present invention, an inner fin having a gear-shaped cross section is inserted concentrically with respect to the sealed pipe in a state with good heat transfer properties inside the cooling part of the sealed pipe. This not only greatly increases the effective area for evaporation or condensation, but also reduces the thickness of the mud layer, which prevents the surface of the inner fin from being covered with a thick layer of liquid, especially when centrifugal force is applied. Therefore, the heat transfer coefficient can be improved by 1, that is, the heat transfer performance can be improved, and there is an effect that the size and weight of the heat pipe can be reduced, that is, the size of the cooling part of the heat pipe can be reduced, for example.

Furthermore, especially when using a sealed pipe with a uniform inner diameter, the inner fin can be easily manufactured by press caroe using a plate material with a thickness of several millimeters or less, and when using an aluminum material as the material, Inner fins can be easily manufactured by extrusion molding.

Further, the axial length of the heating section or the cooling section and the axial length of the inner fin can be freely expanded or contracted depending on the heat load.

As a result, according to the present invention, a heat pipe with high heat transfer performance can be manufactured at low cost.

[Brief explanation of the drawing]

1 and 2 are longitudinal sectional views of a conventional heat pipe, FIG. 3 is a longitudinal sectional view of an embodiment of a heat pipe according to the present invention, and FIGS. 4, 5, and 6 are longitudinal sectional views of a conventional heat pipe. Fig. 5 is a cross-sectional view showing different embodiments of the inner fin with different cross-sectional shapes, Figs. 7 and 8 are cross-sectional views showing different embodiments in which the inner fin is provided with slits for thermal expansion countermeasures, and Fig. 9 is a cross-sectional view showing different embodiments in which the inner fin has a slit for preventing thermal expansion. FIG. 4 is a longitudinal sectional view showing another embodiment of the present invention compared to the embodiment of FIG. 3; 1... Sealed pipe, 2... Working fluid, 3
... Heating section, 4... Cooling section, 5, 51
~55...Inner fin.

Claims (1)

[Scope of Claims] 1. A heat pipe in which one end of a sealed pipe containing a working fluid is used as a heating part and the other end is used as a cooling part, in which a cross section of the cooling part of the sealed pipe has a gear shape. A B1-pipe characterized in that a sealed inner fin is inserted concentrically into a sealed pipe in a state of good thermal conductivity. 2. The heat pipe according to claim 1, wherein the inner fin is divided into a plurality of pieces in the axial direction. 3! The heat pipe according to claim 1 or 2, wherein the inner fin is configured in the shape of an external gear. 4% Allowance The heat pipe according to claim 1 or 2, wherein the inner fin is configured in the shape of an internal gear. 5% allowance The heat pipe according to any one of claims 1 to 4, wherein the inner fin has a slit formed in a radial direction along an axial direction. .