US20060157229A1

US20060157229A1 - Heat pipe

Info

Publication number: US20060157229A1
Application number: US11/292,258
Authority: US
Inventors: Chu-Wan Hong; Ching-Tai Cheng; Chang-Ting Lo; Jung-Yuan Wu
Original assignee: Foxconn Technology Co Ltd
Current assignee: Foxconn Technology Co Ltd
Priority date: 2005-01-14
Filing date: 2005-12-01
Publication date: 2006-07-20
Also published as: TW200624754A; TWI271501B

Abstract

A heat pipe (10) includes a pipe body (30) filled with working fluid, a screen mesh (50) located in the pipe body, a porous support member (70) supporting the screen mesh to contact with an inner wall (32) of the pipe body.

Description

TECHNICAL FIELD

The present invention relates to a heat pipe, and especially to a support member for providing a support force to press the mesh structure tightly against an inner wall of a pipe body of the heat pipe.

BACKGROUND

As electronic industry continues to advance, electronic components such as central processing units (CPUs), are made to provide faster operational speeds and greater functional capabilities. When a CPU operates at a high speed, its temperature frequently increases greatly. It is desirable to dissipate the heat generated by the CPU quickly.
To solve this problem of heat generated by the CPU, a cooling device is often used to be mounted on top of the CPU to dissipate heat generated thereby. It is well known that heat absorbed by fluid having a phase change is ten times more than that the fluid does not have a phase change; thus, the heat transfer efficiency by phase change of fluid is better than other mechanisms, such as heat conduction or heat convection. Thus, a heat pipe has been developed.
The heat pipe has a hollow pipe body receiving working fluid therein and a wick structure disposed on an inner wall of the pipe body. During operation of the heat pipe, the working fluid absorbs the heat generated by the CPU or other electronic device and evaporates. Then the vapor moves to a condensing section of the heat pipe to dissipate the heat thereof, whereby the vapor is cooled and condensed at the condensing section. The condensed working fluid returns to the evaporating section. The above process is repeated and heat is continuously transferred from the evaporating section into the condensing section.
In general, movement of the working fluid from the condensing section to the evaporating section depends on capillary action of the wick structure. Usually the wick structure has the following four configurations: sintered powder, grooved, fiber and screen mesh. For the thickness and porous size of the screen mesh can be easily changed, the screen mesh is widely used in the heat pipe.
Conventionally, the wick structure of screen mesh of the heat pipe is tightly stuck to the inner wall of the pipe body by a sintering process. The sintering process will soften the screen mesh; thus, the screen mesh consequently cannot provide sufficient support to allow the wick structure of screen mesh to adhere tightly to the inner wall of the pipe body. This in turn adversely affects the capillary action of the heat pipe as well as the function thereof.
For the foregoing reasons, therefore, there is a need in the art for a heat pipe which overcomes the above-mentioned problems.

SUMMARY

According to a preferred embodiment of the present invention, a heat pipe comprises a hollow pipe body for retaining a working fluid therein, a mesh structure located in the pipe body, and a porous support member received in the pipe body and supporting the mesh structure to contact with an inner wall of the pipe body. The porous support member is made of metal foam and continuously extends in the pipe body.
Other objects, advantages and novel features of the present invention will be drawn from the following detailed description of a preferred embodiment of the present invention with attached drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinally cross-sectional view of a heat pipe in accordance with a preferred embodiment of the present invention;
FIG. 2 is a transversely cross-sectional view of the heat pipe of FIG. 1;
FIG. 3 is longitudinally cross-sectional view of a heat pipe in accordance with a second embodiment of the present invention;
FIG. 4 is a longitudinally cross-sectional view of a heat pipe in accordance with a third embodiment of the present invention; and
FIG. 5 is a transversely cross-sectional view of the heat pipe of FIG. 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1-2, a heat pipe 10 according to a preferred embodiment of the present invention comprises a hollow pipe body 30, a screen mesh 50 and a support member 70 for supporting the screen mesh 50 received in the pipe body 30. The heat pipe 10 is divided into an evaporating section, an adiabatic section and a condensing section along an axial direction of the heat pipe 10. The adiabatic section is located between the evaporating and condensing sections.
The pipe body 30 is made of high heat conductivity material such as copper or aluminum. A working fluid (not shown) is filled in the hollow pipe body 30. The working fluid is water, alcohol or other material having a low boiling point. Thus, the working fluid can easily evaporate to vapor when it receives heat at the evaporating section of the heat pipe 10. The heat pipe 10 is vacuumed, and two ends thereof are sealed.
The screen mesh 50 is disposed on an inner wall 32 of the pipe body 30. An outer diameter of the screen mesh 50 is approximately the same as an inner diameter of the pipe body 30. The screen mesh 50 is made of stainless steel, copper etc., which can coexist with the working fluid. A plurality of pores is defined in the screen mesh 50 for providing a capillary action to the working fluid.
The support member 70 is received in a central portion of the pipe body 30. Thus the screen mesh 50 is sandwiched between the inner wall 32 of the pipe body 30 and the support member 70. The support member 70 has a column shape. The support member 70 extends continuously along an axial direction of the pipe body 30, and has approximately the same length as the screen mesh 50. The support member 70 is solid. The support member 70 has an outer diameter substantially the same as an inner diameter of the screen mesh 50. The support member 70 provides sufficient support to press the screen mesh 50 tightly against the inner wall 32 of the pipe body 30 so that the screen mesh 50 can have an intimate contact with the inner wall 32 of the pipe body 30.
The support member 70 is made of metal foam wherein the metal can be copper, aluminum, magnesium, nickel etc.. A plurality of pores is defined in the support member 70 for reducing the resistance regarding the flowing of the vapor from the evaporating section to the condensing section of the heat pipe 10. Also the support member 70 can be made of other material having pores, for example polyethylene or other porous polymer material. For reducing the resistance of the flowing of the vapor, the volume ratio of the pores of the support member 70 should be more than 50%.
During operation of the heat pipe 10, when the working fluid saturated in the screen mesh 50 in the evaporating section of the heat pipe 10 evaporates to vapor due to heat absorbed from a heat source such as a CPU, vapor moves toward the condensing section of the heat pipe 10 due to the difference of vapor pressure to perform heat transport, and then cools and condenses in the condensing section to perform heat dissipation. In this case, the condensed working fluid enters the screen mesh 50 in the condensing section and then returns to the evaporating section due to the difference of capillary pressure between the condensing and evaporating sections. Such a process is repeated so that heat is continuously transferred from the evaporating section into the condensing section.
Since the screen mesh 50 is tightly attached to the inner wall 32 of the pipe body 30 by the support member 70, the capillary action of the screen mesh 50 is improved, which in turn improves the efficiency of the heat pipe 10.
Referring to FIG. 3, it illustrates an alternative embodiment of the present invention. Except for the support member 72, other parts of the heat pipe 10 in accordance with this second embodiment have substantially the same configuration with the heat pipe 10 of the previous first preferred embodiment. According to this second embodiment, along the axial direction of the heat pipe 10, the support member 72 is discrete. The support member 72 comprises several sections. A space 90 is defined between two neighboring sections. The heat pipe 10 according to this embodiment can be more easily bent to have a complicated shape, such as a U-like shape or an S-like shape. The support member 72 with a discrete configuration can reduce the resistance for the flowing of the vapor from the evaporating section to the condensing section of the heat pipe 10.
FIGS. 4-5 show a third embodiment of the present invention, the difference between the third embodiment and the previous two embodiments is that the support member 74 of this third embodiment is hollow. A through hole 80 is defined in a central portion of the support member 74. Thus, the third embodiment can further reduce the flowing resistance of the vapor. Then the vapor can easily move from the evaporating section toward the condensing section.
It is understood that the invention may be embodied in other forms without departing from the spirit thereof. Thus, the present example and embodiment is to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.

Claims

1. A heat pipe comprising:

a hollow pipe body having an inner wall;

a mesh structure located in the pipe body, and

a porous support member supporting the mesh structure to contact with the inner wall of the pipe body.

2. The cooling device as claimed in claim 1, wherein the support member is disposed in a central portion of the pipe body, the mesh structure is sandwiched between the pipe body and the support member.

3. The cooling device as claimed in claim 1, wherein the support member is column shaped and extends along an axial direction of the pipe body.

4. The cooling device as claimed in claim 3, wherein support member extends continuously along the axial direction of the pipe body.

5. The cooling device as claimed in claim 4, wherein support member extends discretely along the axial direction of the pipe body, and comprises several sections and a space is defined between two neighboring sections.

6. The cooling device as claimed in claim 1, wherein the support member is hollow and defined a through hole in a central portion thereof.

7. The cooling device as claimed in claim 1, wherein the support member is solid.

8. The cooling device as claimed in claim 1, wherein the support member is made of one of metal foam and porous polymer material.

9. The cooling device as claimed in claim 8, wherein the metal foam is selected from following material: copper, aluminum, magnesium, nickel.

10. The cooling device as claimed in claim 8, wherein the porous polymer material is polyethylene.

11. The cooling device as claimed in claim 1, wherein a volume ratio of pores of the support member is larger than 50%.

12. A heat pipe comprising:

a hollow pipe body having an inner wall;

a mesh structure disposed on the inner wall of the pipe body, and

a column shaped support member disposed in a central portion of the pipe body to support the mesh structure to contact with the inner wall of the pipe body, the support member having pores therein for passage of vapor.

13. The cooling device as claimed in claim 12, wherein support member is made of one of metal foam and porous polymer material.

14. The cooling device as claimed in claim 13, wherein a volume ratio of pores of the support member is larger than 50%.

15. The cooling device as claimed in claim 14, wherein the support member is hollow and defined a through hole therein.

16. The cooling device as claimed in claim 14, wherein the support member extends discretely along an axial direction of the pipe body, and comprises several sections and a space is defined between two neighboring sections.

17. A heat pipe comprising:

a hollow pipe body having an inner wall;

a mesh structure received in the hollow pipe body; and

a support member made of metal foam received in the hollow pipe body and pressing the mesh structure against the inner wall of the pipe body.

18. The heat pipe of claim 17, wherein the support member is continuously extended in the pipe body.

19. The heat pipe of claim 17, wherein the support member is discrete in the pipe body.

20. The heat pipe of claim 17, wherein the support member is hollow.