WO2024024167A1

WO2024024167A1 - Heat pipe

Info

Publication number: WO2024024167A1
Application number: PCT/JP2023/012223
Authority: WO
Inventors: モハマドシャヘッドアハメド; 剛小川
Original assignee: 株式会社フジクラ
Priority date: 2022-07-29
Filing date: 2023-03-27
Publication date: 2024-02-01

Abstract

Provided is a heat pipe comprising: a container in which hydraulic fluid is sealed; a water-permeable first wick that is in contact with the inner periphery of the container; and a water-permeable second wick that is in contact with the first wick and faces a steam channel provided inside the container. The first wick is formed in a wave shape in a cross-sectional view perpendicular to the longitudinal direction of the container, and no grooves are formed on the inner periphery of the container.

Description

heat pipe

The present invention relates to a heat pipe.
This application claims priority based on Japanese Patent Application No. 2022-121422 filed in Japan on July 29, 2022, the contents of which are incorporated herein.

Patent Document 1 discloses a heat pipe having a container and a working fluid sealed in the container. In this heat pipe, capillary force is applied to the liquid phase working fluid by forming grooves on the inner circumferential surface of the container. This capillary force transports the liquid phase working fluid from the condensing section to the evaporating section.

Japanese Patent Application Publication No. 2022-78819

It is thought that heat transportability can be ensured by using grooves to flow a liquid-phase working fluid, as in Patent Document 1. On the other hand, forming grooves on the inner peripheral surface of the container reduces the strength of the container. In order to ensure the strength of the container, it may be possible to increase the thickness of the container, but in that case it would be difficult to downsize the heat pipe.

The present invention was made in consideration of these circumstances, and an object of the present invention is to provide a heat pipe that can achieve both heat transport performance and size reduction.

In order to solve the above problems, a heat pipe according to aspect 1 of the present invention includes a container in which a working fluid is sealed, a first wick that is in contact with an inner circumferential surface of the container and has water permeability, and a second wick that is in contact with the container, faces a steam flow path provided in the container, and has water permeability; and no groove is formed on the inner circumferential surface of the container.

According to the first aspect, the first wick is formed in a wavy shape in a cross-sectional view, and has a plurality of grooves extending in the longitudinal direction. Since the grooves have high permeability, the flow resistance of the liquid flowing through the grooves is small. Therefore, heat transport performance can be improved by transporting liquid using the grooves. Furthermore, the wall thickness of the container can be reduced compared to the case where grooves are formed on the inner circumferential surface of the container. Therefore, it is possible to provide a heat pipe that achieves both heat transport performance and size reduction.

Further, according to a second aspect of the present invention, in the heat pipe according to aspect 1, the first wick includes a plurality of first convex portions that protrude toward the inner circumferential surface of the container, and a plurality of first convex portions that protrude toward the second wick. a plurality of second convex portions, all of the plurality of second convex portions may be in contact with the second wick.

According to the second aspect, the liquid carried from the condensing section to the evaporating section by the first wick is smoothly transferred to the second wick via the plurality of second convex sections. Thereby, the liquid can be stably supplied to the second wick, and the liquid can be stably evaporated from the surface of the second wick.

Furthermore, according to a third aspect of the present invention, in the heat pipe of the first or second aspect, the second wick may be a sintered body of copper powder or fine copper wire.

According to the third aspect, it is possible to realize a first wick that has water permeability and is waveform in cross-sectional view.

Further, in a fourth aspect of the present invention, in the heat pipe according to any one of aspects 1 to 3, the container has a flat shape, and the second wick extends in the width direction of the container in the cross-sectional view. Good too.

According to the fourth aspect, the vapor flow path and the liquid flow path (grooves of the first wick) can be separated by the second wick. Therefore, even in a flat heat pipe whose steam flow path has a small cross-sectional area, it is possible to ensure heat transport performance.

According to the above aspect of the present invention, it is possible to provide a heat pipe that can achieve both heat transport performance and size reduction.

FIG. 3 is a cross-sectional view of the heat pipe according to the first embodiment. FIG. 3 is a cross-sectional view of a heat pipe according to a second embodiment.

(First embodiment)
Hereinafter, the heat pipe of the first embodiment will be explained based on the drawings.
As shown in FIG. 1, the heat pipe 1A includes a container 10, a first wick 20, and a second wick 30. The first wick 20 and the second wick 30 are housed in the container 10. The first wick 20, the second wick 30, and the container 10 are fixed to each other.

Although the fixing method can be selected as appropriate, for example, the container 10 and the first wick 20 may be fixed by sintering, and the first wick 20 and the second wick 30 may be further fixed by sintering. The container 10 has an elongated shape (not shown) extending in one direction. A working fluid (not shown) is sealed inside the container 10 .

(direction definition)
In this specification, the direction in which the container 10 extends is simply referred to as the longitudinal direction. Further, a cross section perpendicular to the longitudinal direction of the container 10 is referred to as a cross section. FIG. 1 is a cross-sectional view of a heat pipe 1A.
In this embodiment, the container 10 has a flat shape and has a first wall 11 and a second wall 12 that are substantially parallel to each other. In a cross-sectional view, the direction in which the first wall portion 11 and the second wall portion 12 extend is referred to as the width direction. Further, the direction perpendicular to both the longitudinal direction and the width direction is referred to as the thickness direction. In FIG. 1, the direction along the X-axis is the width direction, and the direction along the Y-axis is the thickness direction. The thickness T (external dimension in the thickness direction) of the container 10 is, for example, 1 mm or less.

The working fluid enclosed in the container 10 is a well-known phase-changing substance. Inside the container 10, the working fluid undergoes a phase change between a gas phase and a liquid phase. For example, water (pure water), alcohol, ammonia, etc. can be used as the working fluid. In this specification, a gas-phase working fluid may be referred to as a "steam," and a liquid-phase working fluid may be referred to as a "liquid." Further, when the gas phase and the liquid phase are not particularly distinguished, they may be simply referred to as working fluid.

The container 10 is a sealed hollow container. A steam flow path S1 is provided inside the container 10. The steam flow path S1 is a space for steam to flow. Steam flows mainly along the longitudinal direction within the steam flow path S1. For example, both ends of the container 10 in the longitudinal direction are used as an evaporation section and a condensation section, respectively. In this case, the steam flows in the steam flow path S1 along the longitudinal direction from the evaporating section to the condensing section. The container 10 has an inner peripheral surface 10a. The inner circumferential surface 10a is smooth and has no grooves or the like.

The first wick 20 is formed in a wavy shape when viewed in cross section, and has a substantially uniform thickness. The first wick 20 has a plurality of first protrusions 21 and a plurality of second protrusions 22. In the width direction, the first protrusions 21 and the second protrusions 22 are arranged alternately. Each first convex portion 21 projects toward the inner circumferential surface 10a of the container 10. More specifically, each first convex portion 21 protrudes toward the inner circumferential surface 10a of the first wall portion 11. Each second convex portion 22 projects toward the second wick 30. In other words, each second convex portion 22 protrudes toward the inner circumferential surface 10a of the second wall portion 12. In this embodiment, all the first convex parts 21 are in contact with the first wall part 11 (inner peripheral surface 10a), and all the second convex parts 22 are in contact with the second wick 30.

The first convex portion 21 and the second convex portion 22 extend along the longitudinal direction. A portion between adjacent first convex portions 21 in the width direction is referred to as a first groove 23. The portion between the second convex portions 22 adjacent to each other in the width direction is referred to as a second groove 24. The plurality of first grooves 23 extend along the longitudinal direction and are open toward the first wall portion 11. The plurality of second grooves 24 extend along the longitudinal direction and are open toward the second wick 30.

The first groove 23 and the second groove 24 function as a liquid flow path through which the liquid-phase working fluid flows in the longitudinal direction. For this reason, the widths of the first groove 23 and the second groove 24 are preferably set to such an extent that capillary force is generated in the liquid phase working fluid. As an example, the average value of the widths of the first groove 23 and the second groove 24 may be about 0.1 mm. Moreover, the average value of the depths of the first groove 23 and the second groove 24 may be about 0.1 mm.

In the example of FIG. 1, the cross-sectional shape of the first groove 23 and the second groove 24 is V-shaped. However, the shapes of the first groove 23 and the second groove 24 may be changed as appropriate. For example, the cross-sectional shape of the first groove 23 and the second groove 24 may be U-shaped.

The second wick 30 is sheet-shaped and has a substantially uniform thickness along the width direction. The second wick 30 faces the steam flow path S1. The second wick 30 is formed linearly in a cross-sectional view and extends in the width direction.

The first wick 20 and the second wick 30 have water permeability. Further, the first wick 20 and the second wick 30 have a large number of pores that can generate capillary force in the liquid phase working fluid. Therefore, the liquid phase working fluid can flow through the first wick 20 and the second wick 30 by capillary force. The material for the first wick 20 is preferably copper powder or a sintered body of fine copper wire. For example, the first wick 20 may be formed by sintering copper powder in a corrugated mold. Alternatively, the first wick 20 may be formed by deforming a sheet-like sintered body of fine copper wire into a wave shape. The first wick 20 may be formed using other methods. A suitable material for the second wick 30 is a sintered body of copper powder.

Next, the operation of the heat pipe 1A configured as above will be explained.

At least a portion of the first wick 20 and the second wick 30 is impregnated with a liquid-phase working fluid. In the portion of the heat pipe 1A that is in contact with the heat source (evaporation portion), the liquid-phase working fluid evaporates. This evaporation occurs, for example, on the surface of the second wick 30. The working fluid that has evaporated into a gas phase travels through the vapor flow path S1 to a portion (condensation portion) of the heat pipe 1A that is remote from the heat source. In the condensing section, the gas phase working fluid is deprived of heat and condensed.

The working fluid that has condensed into a liquid phase returns to the evaporation section through the first groove 23 and the second groove 24. The liquid (liquid-phase working fluid) that has reached the evaporator through the first groove 23 passes through the first wick 20 and heads toward the second wick 30 . The liquid that has reached the evaporation section through the second groove 24 heads directly to the second wick 30. Then, the liquid evaporates again on the surface of the second wick 30. By repeating this action, the heat pipe 1A can continuously transport heat from the evaporation section to the condensation section. Thereby, the heat pipe 1A can cool the heat source.

Here, in order to improve the heat transport performance of the heat pipe 1A, it is required to circulate the working fluid smoothly within the container 10. In this embodiment, the first wick 20 has a wavy shape when viewed in cross section. That is, the first wick 20 has a plurality of first grooves 23 and second grooves 24. These first grooves 23 and second grooves 24 function as a flow path (liquid flow path) for liquid-phase working fluid. In this way, when the liquid flow path is a groove, higher permeability can be obtained than when the liquid flow path is a pore. The higher the permeability of the liquid flow path in the longitudinal direction, the lower the flow resistance of the liquid, and the smoother the liquid can be returned from the condensing section to the evaporating section. This increases heat transport performance.

Furthermore, in a heat pipe, the direction in which steam flows and the direction in which liquid flows are generally opposite to each other. Also in this embodiment, vapor flows from the evaporator to the condensing part, but liquid flows from the condensing part to the evaporating part. Therefore, if the vapor flow path and the liquid flow path are in contact with each other, the flow of vapor and the flow of liquid may interfere with each other, resulting in a decrease in heat transport performance. In particular, in a flat heat pipe with a small thickness (for example, thickness T of 1 mm or less), the cross-sectional area of the steam flow path S1 is also small, and a reduction in heat transport performance due to steam pressure loss becomes a significant issue. .

In this embodiment, the vapor flow path S1 and the liquid flow path (the first groove 23 and the second groove 24) are separated by the second wick 30. This prevents vapor and liquid from interfering with their flow. Thereby, heat transport performance can be further improved.

Additionally, in recent years, heat pipes are sometimes used to cool internal components of small electronic devices (for example, smartphones, etc.). Therefore, there is a need for a heat pipe that has both heat transport performance and miniaturization. In this embodiment, no groove is formed in the inner circumferential surface 10a of the container 10. Therefore, compared to the case where grooves are formed on the inner circumferential surface 10a of the container 10, it is easier to achieve both thinness and strength of the container 10. Furthermore, the first wick 20 has a first groove 23 and a second groove 24 that serve as liquid flow paths. Therefore, heat transport performance equivalent to that achieved by forming grooves in the container 10 can be achieved.

As explained above, the heat pipe 1A of the present embodiment includes a container 10 in which a working fluid is sealed, a first wick 20 that is in contact with the inner peripheral surface 10a of the container 10 and has water permeability, and a first wick 20 that is in contact with the inner peripheral surface 10a of the container 10. A second wick 30 that is in contact with, faces the steam flow path S1 provided in the container 10, and has water permeability. The first wick 20 is formed in a wave shape in a cross-sectional view perpendicular to the longitudinal direction of the container 10, and no groove is formed in the inner circumferential surface 10a of the container 10. According to this configuration, the first wick 20 has

grooves

23 and 24 extending in the longitudinal direction. Since the

grooves

23 and 24 have high transmittance, the flow resistance of the liquid is reduced, and the heat transport performance can be improved. In addition, the wall thickness of the container 10 can be reduced compared to the case where a groove is formed on the inner circumferential surface 10a of the container 10. Therefore, it is possible to provide a heat pipe 1A that achieves both heat transport performance and size reduction.

The first wick 20 also includes a plurality of first convex portions 21 that protrude toward the inner peripheral surface 10a of the container 10 and a plurality of second convex portions 22 that protrude toward the second wick 30. , all of the plurality of second convex portions 22 may be in contact with the second wick 30. According to this configuration, the liquid carried from the condensing section to the evaporating section by the first wick 20 is smoothly delivered to the second wick 30 via the plurality of second convex sections 22. Thereby, the liquid can be stably evaporated from the surface of the second wick 30.

Furthermore, the first wick 20 may be a sintered body of copper powder or fine copper wire. Thereby, it is possible to realize the first wick 20 which has water permeability and is waveform in cross-sectional view.

Further, the container 10 of this embodiment has a flat shape, and the second wick 30 extends in the width direction of the container 10 (X-axis direction in FIG. 1) in a cross-sectional view. According to this configuration, the second wick 30 can separate the vapor flow path S1 and the liquid flow path (grooves 23, 24). Therefore, even in the flat heat pipe 1A in which the steam flow path S1 has a small cross-sectional area, it is possible to ensure heat transport performance.

(Second embodiment)
Next, a second embodiment according to the present invention will be described, which has the same basic configuration as the first embodiment. Therefore, similar configurations will be given the same reference numerals and their explanations will be omitted, and only the different points will be explained.

As shown in FIG. 2, the heat pipe 1B of this embodiment has a cylindrical shape. More specifically, the container 10, the first wick 20, and the second wick 30 each have a cylindrical shape. The steam flow path S1 is located at the center of the heat pipe 1B and is surrounded by the second wick 30. In this embodiment, the direction intersecting the central axis O of the container 10 in a cross-sectional view is referred to as the radial direction, and the direction going around the central axis O is referred to as the circumferential direction.

The first wick 20 has a wavy shape when viewed in cross section. The first wick 20 has a plurality of first protrusions 21 and a plurality of second protrusions 22. The first convex portions 21 and the second convex portions 22 are arranged alternately in the circumferential direction. The plurality of first convex portions 21 protrude radially outward and are in contact with the container 10. The plurality of second convex portions 22 protrude radially inward and are in contact with the second wick 30.

Similarly to the first embodiment, the heat pipe 1B of the present embodiment includes a container 10 in which a working fluid is sealed, a first wick 20 that is in contact with the inner peripheral surface 10a of the container 10 and has water permeability, and 20, facing the steam flow path S1 provided in the container 10, and having water permeability. The first wick 20 is formed in a wave shape in a cross-sectional view perpendicular to the longitudinal direction of the container 10, and no groove is formed in the inner circumferential surface 10a of the container 10. Therefore, the same effects as in the first embodiment can be obtained. That is, since the first wick 20 has

grooves

23 and 24 extending in the longitudinal direction, and the

grooves

23 and 24 have high transmittance, the flow resistance of the liquid is reduced and the heat transport performance can be improved. In addition, the wall thickness of the container 10 can be reduced compared to the case where a groove is formed on the inner circumferential surface 10a of the container 10. Therefore, it is possible to provide a heat pipe 1B that achieves both heat transport performance and size reduction.

Note that the technical scope of the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention.

For example, in the first embodiment, one first wick 20 and one second wick 30 were provided in the container 10. However, two first wicks 20 and two second wicks 30 may be provided in the container 10. In this case, in addition to the first wick 20 shown in FIG. 1, a corrugated first wick 20 may be arranged so as to be in contact with the second wall portion 12. Furthermore, the second wick 30 may be arranged so as to be in contact with the first wick 20 arranged on the second wall portion 12 side and to face the steam flow path S1.

Further, in the embodiment described above, all the first convex portions 21 are in contact with the inner circumferential surface 10a of the container 10, but some of the first convex portions 21 may not be in contact with the inner circumferential surface 10a. good. Similarly, some of the second convex portions 22 may not be in contact with the second wick 30.

In addition, the components in the embodiments described above can be replaced with well-known components as appropriate without departing from the spirit of the present invention, and the embodiments and modifications described above may be combined as appropriate.

1A, 1B... Heat pipe 10... Container 10a... Inner peripheral surface 20... First wick 21... First convex part 22... Second convex part 30... Second wick S1... Steam flow path

Claims

a container containing a working fluid;
a first wick that is in contact with the inner peripheral surface of the container and has water permeability;
a second wick that is in contact with the first wick, faces a steam flow path provided in the container, and has water permeability;
The first wick is formed in a wave shape in a cross-sectional view perpendicular to the longitudinal direction of the container,
A heat pipe in which a groove is not formed on the inner circumferential surface of the container.
The first wick has a plurality of first convex portions that protrude toward the inner circumferential surface of the container, and a plurality of second convex portions that protrude toward the second wick,
The heat pipe according to claim 1, wherein all of the plurality of second convex portions are in contact with the second wick.
The heat pipe according to claim 1 or 2, wherein the second wick is a sintered body of copper powder or fine copper wire.
The container has a flat shape,
The heat pipe according to any one of claims 1 to 3, wherein the second wick extends in the width direction of the container in the cross-sectional view.