JP2003247791A - Heat pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase heat transfer capacity of a heat pipe. <P>SOLUTION: In this heat pipe 1, a large number of grooved pipes 3 are formed in parallel or spiral in a pipe length direction inside a heat pipe container 2 sealed in an airtight condition, and working fluid 6 with a condensing property is sealed inside the heat pipe container 2. A plurality of ultrafine wires 4 are brought into contact with the inside of the heat pipe container 2, and wicks of the plurality of the ultrafine wires 4 and the grooved pipes 3 are formed to the heat pipe container 2. Wire bar elements are pressed and held to the inner face of the heat pipe container by an elastic element, and the wire bar elements are twisted together into a bundle. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat pipe that transfers heat as latent heat of vaporization of a working fluid.

[0002]

2. Description of the Related Art Conventionally, as a latent heat of a working fluid, a heat pipe that transports heat is widely known. This type of heat pipe degasses the inside of a closed container, then seals a condensable fluid such as water, evaporates the working fluid by the heat input from the outside, and the vapor has a low-temperature, low-pressure condensation section. The heat conducting element is configured to transfer heat as latent heat of the working fluid by radiating heat and condensing after flowing. Therefore, since the heat pipe transports heat as the latent heat of the working fluid, the heat pipe has a transport capacity of several tens to one hundred and several tens of times that of copper, which is considered to have the highest thermal conductivity.

In this type of heat pipe, the evaporated working fluid transfers heat by flowing into the condensation section on the low temperature / low pressure side. However, after transporting the heat, it is necessary to recirculate the condensed working fluid to the evaporation section (heat input section),
Generally, the action for the reflux is performed by utilizing the capillary pressure generated by the wick.

The most common structure of a wick in a heat pipe is a fine groove formed on the inner surface of the pipe. The narrow groove is formed on the inner surface of the pipe along the axial direction by etching or cutting. A groove type wick of this kind can generate a capillary pressure for reflux. Together, the narrow grooves form the flow path for the liquid phase working fluid. Therefore, it is possible to generate a pumping action for causing the liquid-phase working fluid to recirculate with the flow path resistance when the liquid-phase working fluid recirculates reduced. An example of a heat pipe using this type of groove tube is disclosed in JP-A-03-117892 and JP-A-61-16692.
It is introduced in Japanese Patent No. 4 publication.

In the former heat pipe disclosed in Japanese Patent Laid-Open No. 03-117892, the opening portion of the groove tube provided on the inner wall is deep, and the entire shape of the groove tube is pleated. In the example of the heat pipe described in this publication, the heat transport amount is increased by devising the shape of the groove pipe.

In the latter heat pipe disclosed in Japanese Patent Laid-Open No. 61-36694, a wire net is brought into contact with the groove pipe provided on the inner wall to increase the heat transport amount.

When the heat pipes introduced in the above two publications are used in electronic equipment such as personal computers, electronic parts attached to the electronic equipment can be efficiently cooled or radiated.

[0008]

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention
In the heat pipe described in Japanese Patent No. 17892, the shape of the groove tube on the inner wall is formed in a specific shape different from the shape of the conventional groove tube to increase the heat transport amount. Therefore, in order to form the heat pipe, it is necessary to separately form a plug member that forms the groove tube, which causes an inconvenience that the manufacturing cost increases. When forming the groove tube in a specific shape,
Depending on the material of the container that is the main body of the heat pipe, there are restrictions on the shape of the groove pipe,
There is an inconvenience that it cannot be formed into the specific shape.
As a result, there is a possibility that a sufficient heat transport capacity cannot be obtained.

Further, in the latter heat pipe disclosed in Japanese Patent Laid-Open No. 61-36694, the amount of heat transport is increased by bringing the wire net into contact with the groove pipe. Therefore, it is necessary to fix the wire mesh in contact with the groove tube. Therefore, during the work of forming the heat pipe, a special process or device is required to prevent the wire mesh from moving while being in contact with the groove pipe. as a result,
There is a disadvantage that it becomes difficult to mass-produce the heat pipe. Further, when the heat pipe is bent or processed into a flat shape, the wire mesh may be deformed by buckling and may be separated from the groove pipe. As a result, a sufficient amount of hydraulic fluid is not supplied to the evaporator, impairing the heat transfer characteristics,
There was a possibility that the heat transport capacity would be hindered.

The present invention has been made in view of the above circumstances, and an object thereof is to increase the heat transport capacity of a heat pipe.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a heat pipe container hermetically sealed in which a plurality of grooves are piped. In a heat pipe that is formed in parallel or in a spiral shape in the length direction and has a condensable working fluid enclosed in the heat pipe container, a plurality of filaments are arranged along the inner surface of the heat pipe container. Is a heat pipe.

Therefore, in the first aspect of the present invention, the plurality of filaments are held on the inner surface of the heat pipe container, and the wick is formed from the plurality of filaments and the groove. As a result, when the working fluid comes into contact with the groove, the working fluid can generate a capillary pressure for reflux. Further, the groove increases the surface area in contact with the liquid-phase working fluid. As a result, the thermal resistance between the heat pipe container and the working fluid is extremely low. In addition, a fine space is secured between the filaments. As a result, a high capillary pressure is generated and a return path for the liquid phase working fluid is secured.

The invention of claim 2 is the heat pipe according to the structure of claim 1, wherein the linear member is pressed against and held by the inner surface of the heat pipe container by an elastic body. .

Therefore, according to the second aspect of the present invention, the linear body is pressed and held by the elastic body and closely adheres to the inner surface of the heat pipe container.

A third aspect of the present invention is the heat pipe according to the first or second aspect, wherein the filaments are twisted together to form a bundle.

Therefore, according to the third aspect of the invention, the filaments are twisted together so that they can be easily inserted into the heat pipe container.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described with reference to the drawings. FIG. 1 shows a specific example of the heat pipe according to the present invention. Heat pipe 1 shown here
The heat pipe container 2 is formed by sealing both ends of a copper pipe material into a hollow hermetically sealed state. Fine grooves are provided in parallel on the inner wall of the heat pipe container 2 to form a groove tube 3.

In the heat pipe container 2, a large number of copper ultrafine wires (fibers) 4 which are in contact with the groove tubes 3 are provided.
And a spiral pressing member 5 for pressing the ultrafine wire 4 against the inner wall surface of the heat pipe container 2, that is, the groove tube 3. As a result, the ultrafine wire 4 is fixed to the groove pipe 3 of the heat pipe container 2.
The groove tube 3 and the ultrafine wire 4 form a wick of the heat pipe 1. Also, heat pipe container 2
A predetermined amount of a condensable fluid such as pure water or alcohol is enclosed as a working fluid 6 in the inside of the vacuum degassed state. One end of the heat pipe 1 thus configured serves as the heating unit 7, and the other end serves as the heat radiating unit 8. A heating element or the like (not shown) is in contact with the heating unit 7.

In the space between the groove tube 3 and the pressing member 5, that is, inside the heat pipe container 2, a large number of ultrafine wires 4 are arranged in a posture along the longitudinal direction. That is, the heating unit 7 in the heat pipe container 2
And the inner surface of the heat radiating portion 8 are connected by the bundle of groove tubes 3 and the ultrafine wires 4. Examples of the ultrafine wire 4 include a copper wire having a circular cross section with a diameter of about 0.05 to 0.1 mm. Further, if a copper oxide (cupric oxide) film is formed on the surface of the copper wire, the wettability of water as a working fluid is improved.

The bundle of these ultrafine wires 4 is held by being pressed against the inner wall surface of the heat pipe container 2 by the outer peripheral surface of the pressing member 5. In this case, since the pressing member 5 has a large elasticity in the winding radius direction, the ultrafine wire 4 is fixed at a predetermined position without being dislocated.

Heat pipe 1 constructed as described above
The heat is transferred from the heating element (not shown) or the like to the end portion of the heating unit 7. The heat transferred to the heating unit 7 heats and evaporates the working fluid 6 enclosed in the heat pipe container 2. At that time, the ultrafine wire 4 is fixed by the pressing member 5 to the inner wall surface of the heat pipe container 2 in which the groove tube 3 is provided. Therefore, heat is transferred between the groove tube 3 and the ultrafine wire 4 and the working fluid 6 by heat conduction. Then, the heat of the working fluid 6 in contact therewith is transferred from the groove tube 3 and the ultrafine wire 4. That is, the surface of the groove pipe 3 and the surface of the ultrafine wire 4 provided on the inner wall surface of the heat pipe container 2 serve as a heat transfer surface from the heat pipe container 2 to the working fluid 6. In this way
The heat transfer surface from the heat pipe container 2 to the working fluid 6 is enlarged. As a result, the resistance (heat resistance) when heat is transferred from the heat pipe container 2 to the working fluid 6 becomes small, and the heat resistance of the heat pipe 1 itself becomes small.

In the heating section 7, the working fluid 6 is evaporated by heat input from the outside. As a result, the internal pressure of the heating unit 7 increases. On the other hand, at the other end, which is the heat dissipation portion 8, the temperature is lowered due to heat dissipation. Therefore, the internal pressure is low. Therefore, the vapor of the working fluid 6 flows toward the heat dissipation portion 8 due to the pressure difference. The heat of the vapor of the working fluid 6 is taken to the outside in the heat dissipation portion 8. Therefore, it radiates heat and condenses.

In this way, the working fluid 6 is liquefied in the heat radiating portion 8 of the heat pipe 1. After that, it is returned to the heating section 7 side through each gap formed by the groove tube 3 and the plurality of ultrafine wires 4. That is, evaporation of the working fluid 6 occurs in the heating unit 7, and thus capillary pressure is generated. The liquid pressure working fluid is caused to flow toward the heating unit 7 by the capillary pressure. Such working fluid 6
Evaporation, condensation, and reflux occur repeatedly. As a result, the heat of the heating element is transported and the heating element is cooled.

Therefore, in the heat pipe 1 shown as the above specific example, the groove tube 3 and the ultrafine wire 4 are provided.
Functions as a wick, and the capillary pressure of the wick can cause the liquid-phase working fluid 6 to flow back from the heat radiating portion 8 to the heating portion 7. Further, each gap formed between the groove tube 3 and the large number of ultrafine wires 4 serves as a return path for the liquid phase working fluid.
Therefore, most of the return passages of the liquid phase working fluid are shielded from the gas phase working flow passage formed on the inner peripheral side of the heat pipe container 2. Therefore, the degree to which the liquid-phase working fluid in the middle of reflux is directly exposed to the working fluid vapor flowing at a high speed is reduced. As a result, the reflux performance of the liquid phase working fluid is improved. Therefore, in combination with the low heat resistance of the heat pipe 1, a large amount of heat can be transported without causing dryout in the heating section 7. As a result, the heat transport capacity of the heat pipe as a whole is improved.

Further, the ultrafine wire 4 is in contact with the groove tube 3 provided on the inner wall of the heat pipe container 2.
Therefore, heat is transferred to the working fluid 6. In the heat radiation part 8, heat is transferred from the working fluid vapor to the heat pipe container 2. That is, the heat pipe container 2
The substantial heat exchange area between the working fluid 6 and the working fluid 6 is widened. Therefore, the thermal resistance of the heat pipe 1 is reduced. Furthermore, since the ultrafine wire 4 is held on the inner surface of the heat pipe container 2, each gap formed between the groove tube 3 and the ultrafine wire 4 functions as a return path.
Therefore, the flow resistance of the working fluid 6 becomes small. As a result, the reflux performance is improved.

FIG. 4 shows another example of the heat pipe of the present invention. The same parts are designated by the same reference numerals and the description thereof will be omitted. In the heat pipe 1A of FIG. 4, the groove pipe 3
The linear body in contact with is made into a stranded wire to form an ultrafine wire 4A. Even with such a heat pipe 1A, it is possible to obtain the same operational effects as those of the heat pipe 1 described above.
In addition, several fine wires 4A are bundled. Therefore, it becomes easy to insert it into the heat pipe container 2. Therefore, the heat pipe 1A is easily manufactured, and the work and the process can be simplified. as a result,
The manufacturing cost can be reduced. The pressing member 5 may be inserted inside the heat pipe 1A.

The results obtained by the experiments of the present inventors are shown in FIG. FIG. 3 is a diagram showing the results of measuring the characteristics of a conventional general heat pipe with a groove tube alone, a conventional heat pipe with an extra-fine wire inserted in a smooth tube, and the heat pipe according to the present invention. . In FIG. 3, □ indicates the measurement result of the groove type heat pipe, ◇ indicates the measurement result of the conventional heat pipe in which the ultrafine wire is inserted in the smooth pipe, and the Δ mark indicates the present invention. The measurement result of this heat pipe is shown.

As shown in FIG. 3, in the heat pipe having only the groove tube, the heat resistance is rapidly increased although the heat input amount is not particularly increased. This indicates that the amount of heat input causes dryout in the heating section. Therefore, further heat transport cannot be performed. On the other hand, in the heat pipe of the type using the smooth tube and the ultrafine wire, the thermal resistance does not particularly increase. As a result, the amount of heat input can be increased. Therefore, the heat transport amount can be increased as compared with a groove-type heat pipe. Further, in the heat pipe in which the groove tube and the ultrafine wire according to the present invention are used, the thermal resistance shows a substantially constant value despite the increase in the heat input amount. Moreover, the thermal resistance is smaller than that of the conventional heat pipe of the smooth pipe and the ultrafine wire type. Therefore, it was revealed that the heat transport capacity is far superior to that of the conventional heat pipe.

Next, an example using the heat pipe according to the present invention will be described. FIG. 5 is a diagram showing a state in which the heat pipe 1 of the present invention is applied to the cooling of electronic parts (not shown).

The heat pipe container 2 is bent at a right angle in the middle part. A plurality of metal plate fins 9 are fixed to one end of the heat pipe container 2. This flat plate fin 9 is used for the heat pipe container 2
Are arranged in parallel at regular intervals so as to spread in the radial direction. Therefore, the heat pipe container 2 and the flat plate fin 9 can transfer heat to each other. It should be noted that this one end portion is the heat radiation portion 8 of the heat pipe 1. Therefore, the other end is the heating unit 7. A heating block 10 is fixed to the heating unit 7. further,
Electronic components (not shown), which are heating elements, are attached to the heating block 10. In addition, a fan (not shown) that allows air to flow from the inside of the housing to the outside is provided near the flat plate fin 9. Then, by rotating the fan (not shown), an airflow is generated from the inside of the housing to the outside. This air flow is configured to pass through the gap between the flat plate fins 9.

Next, the operation of the above heat pipe will be described. When the electronic device is energized, the electronic components operate and generate heat. Then, the heat generated in the electronic component is transferred to the heating unit 7 of the heat pipe 1.

In the heating section 7 of the heat pipe 1, the working fluid 6 is heated and evaporated by the heat transferred thereto. Further, the evaporated working fluid 6 flows toward the heat dissipation portion 8 side. Then, in the heat radiating portion 8, the vapor-phase working fluid 6 radiates heat and liquefies. The radiated heat is transmitted from the heat radiating portion 8 to the flat plate fins 9, and is radiated from there into the airflow flowing through the gap. Then, the airflow received from the flat plate fins 9 is exhausted to the outside of the housing by a fan (not shown). As a result, the heat generated from the electronic component is radiated to the outside of the housing of the electronic device.

On the other hand, the working fluid 6 liquefied in the heat radiating section 8 of the heat pipe 1 is returned to the heating section 7 side by the capillary pressure generated in each gap formed by the groove tube 3 and the plurality of ultrafine wires 4. Then, the above operation is repeated.

According to the above-mentioned embodiment, since the groove tube 3 and the ultrafine wire 4 are used for the wick,
By the capillary pressure of the groove tube 3 and the ultrafine wire 4, the working fluid 6 in the liquid phase can be returned from the heat radiating section 8 to the heating section 7. Further, the flow resistance of the working fluid becomes small. As a result, it is possible to obtain a heat pipe having an excellent heat transport ability.

Further, in the above heat pipe 1, the flexible heat pipe container 2 and the ultrafine wire 4 are supported from the inside by the pressing member 5. Therefore, for example, even if the heat pipe container 2 is bent or flattened, the bundle of the extra fine wires 4 is not cut or separated from the inner wall surface of the heat pipe container 2. Further, the close contact state between the pressing member 5 and the heat pipe container 2 is maintained. Therefore, it is possible to exhibit a high heat transport capacity.

In the heat pipe 1 described above, the required performance for cooling the electronic parts can be met by increasing or decreasing the number of the ultrafine wires 4. Therefore,
There is no need to form special members and jigs. Therefore, the manufacturing cost can be reduced.

As described above, in the above heat pipe 1, the gap between the ultrafine wires 4 is extremely small. Also, the groove tube 3
And the pumping action of the ultrafine wire 4 is large. In addition, the vapor channel and the liquid channel are separated. Further, the liquid phase working fluid is supplied to a wide range of the evaporation section. Therefore, it is possible to improve the heat transport capacity particularly in the top heat mode as compared with the conventional one.

The present invention is not limited to the above specific examples. Therefore, in the present invention, other than the above-mentioned copper ultrafine wire, an appropriate metal fiber can be used as the filament. The wire diameter is 50 for copper fiber.
It is about 100 μm. Similarly, the heat pipe container is not limited to copper, and an appropriate metal pipe is used. The inner diameter is, for example, about several mm. Furthermore, in order to improve the wettability between the metal fiber or the container and the working fluid, an oxide film may be formed on the inner surface of the metal fiber or the container, or a roughening treatment such as sandblasting or etching may be performed. Good.

Further, although the ultrafine wire 4 is brought into contact with the inner wall of the heat pipe container 2 by the pressing member 5, the contacting method is not limited to the above-mentioned pressing metal fitting method. The ultrafine wire 4 may be sintered and fixed to the inner wall of the heat pipe container 2. Alternatively, they may be fixed by an appropriate welding method such as ultrasonic welding or friction welding, or a joining method such as brazing.

Further, although the pressing member 5 has a spiral shape, this shape is not limited to the above shape and may be a round wire spring. The point is that the extra fine wire 4 may be pressed against the inner surface of the heat pipe container 2 by elastic force.

[0041]

As described above, according to the present invention,
By fixing the filament on the inner surface of the heat pipe container having the groove formed on the inner wall, capillary pressure is generated not only on the groove but also on the filament, so that the working fluid in the liquid phase is radiated by the heat radiation part. Therefore, it can be efficiently refluxed to the heating section. As a result, the reflux characteristic of the liquid phase working fluid is improved, and it is possible to obtain a heat pipe having an excellent heat transport ability without causing dryout in the heat input section (heating section). Also,
In addition to the surface of the groove, the surface of the filamentous body can also be used as the heat transfer surface, so that the thermal resistance between the heat pipe container and the working fluid can be made extremely small. As a result, the heat transfer performance between the heat pipe container and the working fluid, or the heat transfer performance between the external heat source or cooling source and the heat pipe can be improved.

The flexible heat pipe container and the linear member are supported from the inside by the elastic body. Therefore, even if the heat pipe container is bent or flattened, the bundle of filaments does not separate from the inner wall surface of the heat pipe container. As a result, the close contact between the elastic body and the heat pipe container is maintained. Therefore, it is possible to exhibit a high heat transport capacity. Further, the required performance for cooling the electronic component can be met by increasing or decreasing the number of filaments. As a result, it is not necessary to form special members and jigs, so that the manufacturing cost can be reduced.

By bundling the filaments, it becomes easy to insert the filaments into the heat pipe container. Therefore, the heat pipe can be easily manufactured, and the work and the process can be simplified. As a result, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing a specific example of a heat pipe according to the present invention.

FIG. 2 is an overall view of the heat pipe of FIG.

FIG. 3 is a diagram showing the results of measuring the characteristics of the heat pipe according to the present invention, a conventional general heat pipe using a groove tube, and a conventional heat pipe in which an ultrafine wire is inserted in a smooth tube. is there.

FIG. 4 is a diagram showing another specific example of the heat pipe according to the present invention.

FIG. 5 is a diagram showing an example in which a heat pipe according to the present invention is applied to an apparatus.

[Explanation of symbols]

1 ... Heat pipe, 2 ... Heat pipe container, 3
... Groove tube, 4 ... Extra fine wire, 6 ... Working fluid.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Chiba             5-1-2 Gomotono Yumoto, Akita City, Akita Prefecture             Tohoku Fujikura Ltd. (72) Inventor Fukushi Naoto             5-1-2 Gomotono Yumoto, Akita City, Akita Prefecture             Tohoku Fujikura Ltd.

Claims (3)

[Claims] 1. A large number of grooves are formed in a heat pipe container that is hermetically sealed in parallel or in a spiral shape in the pipe length direction, and a condensable working fluid is contained in the heat pipe container. In the enclosed heat pipe, a plurality of filaments are arranged along the inner surface of the heat pipe container. 2. The heat pipe according to claim 1, wherein the linear member is pressed against and held by an inner surface of the heat pipe container by an elastic body. 3. The heat pipe according to claim 1, wherein the filaments are twisted together to form a bundle.