JP7123576B2 - heat pipe - Google Patents

Description

The present invention relates to heat pipes.

2. Description of the Related Art Conventionally, a heat pipe as disclosed in Patent Document 1 below is known. This heat pipe includes a container containing a working fluid and a first wick that contacts the inner wall of the container. A second wick, which is a twisted thin copper wire, is embedded in the first wick. According to this configuration, the liquid-phase working fluid can be caused to flow rapidly along the second wick with low liquid flow resistance.

JP 2015-135211 A

There is a demand for further improving the heat transport performance of this type of heat pipe.

SUMMARY OF THE INVENTION The present invention has been made in consideration of such circumstances, and an object of the present invention is to provide a heat pipe with improved heat transport performance.

In order to solve the above problems, a heat pipe according to a first aspect of the present invention includes a long container in which a working fluid is sealed, and a first heat pipe that contacts the inner wall of the container and faces a steam flow path. A wick and a second wick having a space therein extending in the longitudinal direction of the container.

According to the heat pipe according to the aspect described above, the two types of wicks, the first wick and the second wick, are provided, and a space extending in the longitudinal direction is formed in the second wick. With this configuration, the liquid-phase working fluid can flow in the space of the second wick, the flow resistance of this working fluid can be reduced, and the maximum heat transfer amount of the heat pipe can be improved.

Also, the second wick may be embedded in the first wick.

In this case, the outer peripheral portion of the second wick is covered with the first wick, and the portion of the wick facing the steam flow path, that is, the evaporation surface is formed by the first wick. As a result, compared to the case where the second wick is exposed to the vapor flow path, for example, the liquid-phase working fluid is less likely to scatter, and the scatter limit can be improved to increase the maximum heat transfer amount of the heat pipe. .

Also, the second wick may be formed of a braided wire.

In this case, compared with the case where the second wick is formed of twisted thin copper wires, for example, variations in liquid flow resistance caused by variations in the degree of twist can be suppressed. As a result, manufacturing variations in the heat transport characteristics of the heat pipe can be suppressed.

Also, the first wick may be made of sintered metal powder.

In this case, the radius of the pores in the first wick can be reduced to generate a large capillary force in the liquid-phase working fluid flowing in the first wick.

Further, the first wick may be formed by bundling a plurality of thin metal wires.

In this case, since the sintering process for forming the first wick is not required, manufacturing efficiency can be improved.

According to the aspect of the present invention, it is possible to provide a heat pipe with improved heat transport performance.

1 is a cross-sectional view of a heat pipe according to a first embodiment; FIG. FIG. 2 is a cross-sectional view of the heat pipe of FIG. 1 taken along line AA. FIG. 4 is a cross-sectional view of a heat pipe according to a modification of the first embodiment; FIG. 5 is a cross-sectional view of a heat pipe according to a second embodiment; FIG. 5 is a cross-sectional view of the heat pipe of FIG. 4 taken along line BB. (a) is a cross-sectional view of a heat pipe according to a modification of the second embodiment. (b) is a cross-sectional view of a heat pipe according to another modification. (a) is a cross-sectional view of a heat pipe of Comparative Example 1, and (b) is a cross-sectional view of a heat pipe of Comparative Example 2. FIG. 4 is a graph showing experimental results of heat transport efficiency of the heat pipe according to Example 1. FIG. 7 is a graph showing experimental results of heat transport efficiency of the heat pipe according to Example 2. FIG.

(First embodiment)
The configuration of the heat pipe according to the first embodiment will be described below with reference to FIGS. 1 and 2. FIG. In addition, in each drawing used for the following description, the reduced scale is appropriately changed in order to make each member recognizable size.

As shown in FIG. 1, a heat pipe 1A according to the present embodiment includes a container 2 containing a working fluid, and a first wick 11 and a second wick 12 disposed within the container 2. . The first wick 11 and the second wick 12 are impregnated with liquid-phase working fluid.

Here, as shown in FIGS. 1 and 2, the container 2 is formed in an elongated shape. Hereinafter, the longitudinal direction of the container 2 will simply be referred to as the longitudinal direction, and a cross section perpendicular to the longitudinal direction will simply be referred to as the cross section.

The container 2 is formed in a tubular shape in a cross-sectional view, and both ends in the longitudinal direction are sealed. An inner wall 2a of the container 2 is formed into a curved surface that is uniform in the circumferential direction. For example, the container 2 is formed of a smooth tube having a uniform thickness and a smooth inner wall 2a. The container 2 is made of a metal pipe material such as copper.

The working fluid enclosed in the container 2 is composed of a substance that changes phase at a predetermined temperature. Well-known liquids such as water, alcohols, and aqueous ammonia can be used as the working liquid.

The first wick 11 is a porous structure formed by sintering metal powder such as copper. For example, the average particle size of the copper powder that forms the first wick 11 is approximately 125 μm. Note that the material of the first wick 11 may be changed as appropriate.
In cross-sectional view, the first wick 11 is formed in an annular shape, and its outer peripheral portion is in contact with the inner wall 2a over the entire circumference. The outer peripheral portion of the first wick 11 is fixed to the inner wall 2a of the container 2 by sintering. A space inside the first wick 11 (hereinafter referred to as a vapor flow path S1) serves as a flow path for the vapor-phase working fluid. That is, the first wick 11 faces the steam flow path S1. The steam flow path S1 extends over the entire length of the space inside the container 2 in the longitudinal direction.

The pores in the first wick 11 serve as flow paths for the liquid-phase working fluid, which are irregular like a labyrinth. The gap formed between the outer peripheral portion of the first wick 11 and the inner wall 2a also serves as a flow path for the liquid-phase working fluid.

The second wick 12 is embedded within the first wick 11 . The second wick 12 is not exposed to the steam flow path S1. In this embodiment, two second wicks 12 are arranged in the first wick 11 at regular intervals. As shown in FIG. 2 , these second wicks 12 are arranged parallel to each other over the entire longitudinal length of the space within the container 2 . The second wick 12 is a braided wire wick formed by weaving a plurality of thin wires 12a, and has a tubular shape in cross section. In cross-sectional view, the outer diameter of the second wick 12 is smaller than the thickness of the first wick 11 . Inside the second wick 12, a space extending in the longitudinal direction (hereinafter referred to as liquid flow path S2) is formed. The liquid flow path S2 is a flow path for liquid-phase working fluid.

As shown in FIG. 2, the first wick 11 and the second wick 12 extend in the longitudinal direction so as to connect the evaporating section E and the condensing section C of the heat pipe 1A. A capillary force acts on the liquid-phase working fluid impregnated in the first wick 11 and the second wick 12 . When the heat pipe 1A is in operation, the liquid-phase working fluid is evaporated by external heat in the evaporator E to become gas, and the gas flows through the vapor passage S1 and moves to the condenser C (see arrow F1). In the condensation section C, the vapor-phase working fluid is condensed by heat dissipation, and the first wick 11 and the second wick 12 are impregnated with the liquid-phase working fluid. Then, due to the capillary force of the first wick 11 and the second wick 12, the liquid-phase working fluid flows back from the condensation section C toward the evaporation section E (see arrow F2). The liquid-phase working fluid that has reached the evaporator E is evaporated again. In this manner, the heat pipe 1A can transport heat from the evaporator section E to the condenser section C repeatedly.

Here, the reflux characteristics of the liquid-phase working fluid will be described. In each channel of the liquid-phase working fluid, the magnitude of the capillary force that the working fluid receives increases as the capillary radius (size of the gap) decreases. Comparing the first wick 11 and the second wick 12 with respect to the size of the capillary radius, the first wick 11 has a smaller capillary radius than the second wick 12 . In other words, the first wick 11 is formed to exert a greater capillary force than the second wick 12 .

On the other hand, pressure loss occurs in the first wick 11 and the second wick 12 when the liquid-phase working fluid flows. This pressure loss is caused by the shape of the flow path. In this specific example, the channels in the first wick 11 are labyrinthine, and the channels in the second wick 12 are linear. Therefore, the pressure loss in the second wick 12 is smaller than the pressure loss in the first wick 11 . In addition to this, the second wick 12 of this embodiment is formed in a tubular shape, and the inside thereof is used as the liquid flow path S2. The liquid flow path S2 extends in the longitudinal direction and has a substantially constant width in the longitudinal direction, so that the flow resistance of the liquid-phase working fluid is very small.

As described above, in the heat pipe 1A of this embodiment, the second wick 12 with low flow resistance is embedded inside the first wick 11 that exerts a large capillary force. As a result, it is possible to increase the heat transport amount and improve the heat transport performance while extending the transportable distance.

Also, the second wick 12 is formed of a braided wire. As a result, compared to the case where the second wick 12 is formed of a twisted thin copper wire, for example, it is possible to suppress variations in liquid flow resistance caused by variations in the degree of twisting. As a result, manufacturing variations in the heat transport characteristics of the heat pipe 1A can be suppressed.

Further, since the outer peripheral portion of the second wick 12 is covered with the first wick 11, the portion of the wick facing the steam flow path S1, that is, the evaporation surface is formed by the first wick 11 only. As a result, compared to the case where the second wick 12 is exposed to the vapor flow path S1, for example, the liquid-phase working fluid is less likely to scatter, the scatter limit is improved, and the maximum amount of heat transport is increased.

The number of second wicks 12 embedded in the first wick 11 is not limited to the illustrated example, and can be changed as appropriate. For example, four or more than five second wicks 12 may be embedded in the first wick 11 like the heat pipe 1B shown in FIG.

(Second embodiment)
Next, a second embodiment according to the present invention will be described, but the basic configuration is the same as that of the first embodiment. For this reason, the same reference numerals are assigned to the same configurations, the description thereof is omitted, and only the points of difference will be described.

As shown in FIG. 4, the heat pipe 1C of this embodiment is a flat heat pipe, and differs from the first embodiment in the shape and arrangement of the wick. The first wick 11 of this embodiment is arranged in the central portion of the container 3 in the width direction. Also, the first wick 11 does not contact the upper surface 3 a of the container 3 , but contacts the lower surface 3 b of the container 3 . That is, the width of the first wick 11 is less than the width of the lower surface 3b of the container 3, and the thickness of the first wick 11 is smaller than the distance between the upper surface 3a and the lower surface 3b of the container 3. In this embodiment, the space between the first wick 11 and the container 3 functions as the steam flow path S1.

In cross-sectional view, the first wick 11 has a flat portion 11a and a curved portion 11b. The flat portion 11 a is in contact with the lower surface 3 b of the container 3 , and the curved portion 11 b is formed in a curved surface that protrudes toward the upper surface 3 a of the container 3 . As shown in FIGS. 4 and 5, the first wick 11 has a substantially semi-cylindrical shape extending in the longitudinal direction of the heat pipe 1C. In this embodiment, the flat portion 11a of the first wick 11 is fixed to the bottom surface 3b of the container 3 by sintering.
The flat type heat pipe 1C as in the present embodiment can also obtain the same effects as in the first embodiment.

The number of first wicks 11 and second wicks 12 arranged in the container 3 can be changed as appropriate. For example, a plurality of second wicks 12 may be embedded in one first wick 11, like a heat pipe 1D in FIG. 6(a). Alternatively, a plurality of first wicks 11 and second wicks 12 may be brought into contact with the upper surface 3a and the lower surface 3b of the container 3, respectively, like the heat pipe 1E in FIG. 6(b).

In addition, in the first and second embodiments, the configuration of the first wick 11 may be changed as appropriate. For example, the first wick 11 may be formed of a plurality of thin metal wires, and the second wick 12 formed of braided wires may be embedded in the first wick 11 . In this case, although the material and diameter of the fine wire forming the first wick 11 can be changed as appropriate, a fine copper wire having a diameter of about 125 μm, for example, may be used. Alternatively, the first wick 11 may be configured by bundling a plurality of fine wires without twisting them. In this case, the second wick 12 can be easily embedded inside the first wick 11 .

When the first wick 11 is formed by using a plurality of thin wires, the gaps between the thin wires serve as flow paths for the liquid-phase working fluid. Therefore, by reducing the gap between the fine wires, a large capillary force can be generated in the liquid-phase working fluid flowing in the first wick 11 . Moreover, since the sintering process for forming the first wick 11 is not necessary, the manufacturing efficiency can be improved.

The above embodiments will be described below using specific examples. In addition, the following examples do not limit the present invention.

(Example 1)
In Example 1, a heat pipe 1C (see FIGS. 4 and 5) similar to that described in the second embodiment was produced. The first wick 11 in Example 1 is a porous structure formed by sintering copper powder. The longitudinal distance between the evaporator E and the condenser C was about 300 mm. Moreover, the width of the container 3 was set to 11.5 mm, and the thickness of the container 3 was set to 2.5 mm.
(Comparative example 1)
As Comparative Example 1, a heat pipe 100A as shown in FIG. The wick W1 of the heat pipe 100A is formed by sintering metal powder, like the first wick 11 of the heat pipe 1C. Other points are the same as those of the heat pipe 1C of the first embodiment.
(Comparative example 2)
As Comparative Example 2, a heat pipe 100B as shown in FIG. 7B was produced. The wick W2 of the heat pipe 100B is formed by bundling thin copper wires. Other points are the same as those of the heat pipe 1C of the first embodiment.

FIG. 8 shows the results of confirming the heat transport performance of the above three heat pipes. The horizontal axis of FIG. 8 is the heat input Q (W), and the vertical axis of FIG. 8 is the heat resistance Rhp (C/W).
As shown in FIG. 8, with the heat pipe 1C of Example 1, a larger maximum heat transfer amount than with the heat pipes 100A and 100B of Comparative Examples 1 and 2 could be obtained. The reason for this will be considered below.

In the heat pipe 100A of Comparative Example 1, the wick W1 is made of only sintered metal powder, so that the transmittance and porosity thereof are small. For this reason, the flow resistance of the liquid-phase working fluid flowing in the wick W1 is large, and the ability to circulate the liquid-phase working fluid from the condensation section C to the evaporation section E is considered to be small.
In the heat pipe 100B of Comparative Example 2, the wick W2 is formed only by the bundled thin copper wires, so that the capillary force is small. Therefore, it is considered that the force to circulate the liquid-phase working fluid flowing in the wick W2 is small.

In contrast to these comparative examples, in the heat pipe 1C of Example 1, a second wick 12 with a low flow resistance is placed inside the first wick 11 that exerts a large capillary force because it is made of sintered metal powder. is embedded. As a result, it is considered that the liquid-phase working fluid can be rapidly circulated from the condenser section C to the evaporator section E, and the maximum amount of heat transport can be increased.

(Example 2)
As Example 2, a heat pipe having a cross-sectional shape as shown in FIG. 6(a) was produced. In Example 2, the first wick 11 was formed by bundling a plurality of thin copper wires without twisting them. The longitudinal distance between the evaporating section E and the condensing section C, and the width and thickness of the container 3 are the same as in the first embodiment.
(Comparative Example 3)
As Comparative Example 3, a heat pipe was produced by removing the second wick 12 from Example 2. FIG. The cross-sectional shape of Comparative Example 3 is the same as that of FIG. 7(b).

The results of confirming the heat transport performance of the heat pipes of Example 2 and Comparative Example 3 are shown in FIG. The horizontal axis of FIG. 9 is the heat input Q (W), and the vertical axis of FIG. 10 is the heat resistance Rhp (C/W).
As shown in FIG. 9, in Example 2, the thermal resistance was smaller than in Comparative Example 3, and a large maximum heat transfer amount could be obtained. The reason for this will be considered below.

In Comparative Example 3 (FIG. 7(b)), the wick W2 is formed only of bundled thin copper wires, so that the capillary force is small. The wick W2 of Comparative Example 3 had a transmittance of 3.6 [m ² ×10 ^-10 ] and a capillary radius of 0.056 [m×10 ^-3 ].
In contrast to Comparative Example 3, in Example 2, a second wick 12 with low flow resistance is embedded inside the first wick 11 that exerts a large capillary force because it is formed by bundling a plurality of thin wires. there is The capillary radii of the first wick 11 and the second wick 12 of Example 2 were 0.056 [m×10 ⁻³ ], which was equivalent to Comparative Example 3. On the other hand, the transmittance in Example 2 was 4.3 [m ² ×10 ⁻¹⁰ ], which was higher than that in Comparative Example 3. Thus, in Example 2, the transmittance is high, so that the liquid-phase working fluid can be rapidly circulated from the condenser section C to the evaporator section E, and the maximum heat transfer amount can be increased. It is thought that

The technical scope of the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

For example, the structures and manufacturing methods of the first wick 11 and the second wick 12 are not limited to the above embodiments, and may be changed as appropriate.

In addition, it is possible to appropriately replace the components in the above-described embodiment with known components without departing from the scope of the present invention, and the above-described embodiments and modifications may be combined as appropriate.

DESCRIPTION OF SYMBOLS 1A-1E... Heat pipe 2, 3... Container 11... 1st wick 12... 2nd wick S1... Vapor flow path S2... Liquid flow path (space)

Claims (4)

an elongated container containing hydraulic fluid;
a first wick in contact with the inner wall of the container and facing the steam channel;
a second wick having therein a space extending in the longitudinal direction of the container and serving as a flow path for the liquid-phase hydraulic fluid ;
The heat pipe, wherein the second wick is formed of a braided wire. 2. The heat pipe of claim 1, wherein said second wick is embedded in said first wick. 3. The heat pipe of claim 1 or 2, wherein the first wick is formed by sintered metal powder. 3. The heat pipe according to claim 1, wherein said first wick is formed by bundling a plurality of thin metal wires.

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