US20090090487A1

US20090090487A1 - Heat pipe

Info

Publication number: US20090090487A1
Application number: US11/987,818
Authority: US
Inventors: Yaw-Huey Lai
Original assignee: Tai Sol Electronics Co Ltd
Current assignee: Tai Sol Electronics Co Ltd
Priority date: 2007-10-09
Filing date: 2007-12-05
Publication date: 2009-04-09
Also published as: JP3138963U; TWM329759U

Abstract

A heat pipe includes a pipe body having two enclosed ends and defining a heat absorbing section and a condensing section, a wick structure formed on the inside wall of the pipe body and having a thickness relatively thicker at the heat absorbing section and relatively thinner at the condensing section, and a working fluid filled in the pipe body. By means of the design that the diameter of the space surrounded by the wick structure in the condensing section is greater than that in the heat absorbing section, the heat pipe eliminates fluid accumulation and maintains excellent temperature uniformity.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates a heat pipe and more particularly, to a heat pipe of better temperature uniformity.
2. Description of the Related Art
A regular heat pipe generally comprises an enclosed pipe body, a wick structure provided inside the enclosed pipe body, and a working fluid filled in the enclosed pipe body. The heat pipe transfers heat energy by means of the phase change of the working fluid between liquid and gas and flowing of the working fluid in the enclosed pipe body. During operation, the working fluid in the heat absorbing section of the enclosed pipe body is heated into steam, the steam thus produced immediately disperses and is then condensed into liquid at the condensing section of the enclosed pipe body, and the condensed liquid is then guided backwards to the heat absorbing section by means of the capillary effect of the wick structure. This heat exchange action is repeated again and again, achieving the desired heat transfer effect.
In some installation cases due to space limitation, for example, for installation in a notebook computer, display card, or any other hot sources, the heat pipe may have to be flattened. When a heat pipe is flattened, as shown in FIG. 4, the internal space of the heat pipe 70 is relatively reduced, and therefore the steam space becomes smaller and thinner. When steam is condensed into fluid 79 in the condensing section C, one part of the fluid 79 is guided back to the heat absorbing section H while the other part of the fluid 79 is kept in the condensing section C. This condition occurs just because the space surrounded by the wick structure 73 is reduced and this reduced space works as a capillary tube to cause a capillary effect. Therefore, the aforesaid heat pipe design cannot eliminate accumulation of the fluid 79 inside the condensing section C.
Because the fluid is not fully guided back from the condensing section C to the heat absorbing section H, liquid gas conversion cannot be performed in the condensing section C that has fluid accumulation, i.e., thermal energy cannot be transferred to this location. This fluid accumulation results in a relatively lower temperature level, obstructing temperature uniformity of the heat pipe and lowering its heat transfer efficiency.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances in view. It is one object of the present invention to provide a heat pipe, which eliminates fluid accumulation, thereby maintaining excellent temperature uniformity.
To achieve this and other objects of the present invention, the heat pipe comprises a pipe body having two distal ends closed, a wick structure formed on the inside wall of said pipe body and having a predetermined thickness, and a working fluid filled in the pipe body. The pipe body defines a heat absorbing section and a condensing section. The thickness of the wick structure in the heat absorbing section is greater that the thickness of the wick structure in the condensing section. By means of the design that the diameter of the space surrounded by the wick structure in the condensing section is greater than that in the heat absorbing section, the heat pipe eliminates fluid accumulation and maintains excellent temperature uniformity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic top plain view of a heat pipe in accordance with the present invention.

FIG. 2 is a schematic sectional view of the heat pipe in accordance with the present invention.

FIG. 3 is an enlarged view of a part of FIG. 2.

FIG. 4 is a schematic sectional side view of a flattened heat pipe according to the prior art.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1-3, a heat pipe 10 in accordance with the present invention is shown comprised of a pipe body 11, a wick structure 21, and a working fluid 31. The pipe body 11 has its two distal ends closed. The wick structure 21 is formed on the inside wall of the pipe body 11, having a predetermined thickness. The working fluid 31 is filled in the pipe body 11.
The pipe body 1 defines a heat absorbing section H, a heat isolation section A, and a condensing section C. The thickness of the wick structure 21 at the heat absorbing section H is greater than the thickness of the wick structure 21 at the condensing section C. The heat isolation section A is connected between the heat absorbing section H and the condensing section C. The wick structure 21 at the heat isolation section A is relatively thicker at the end close to the heat absorbing section H and relatively thinner at the end close to the condensing section C. Further, the wick structure 21 at the heat isolation section A reduces gradually from the thicker end toward the thinner end, i.e., reduces gradually in direction from the heat absorbing section H toward the condensing section C.
Referring to FIG. 2 again, when the heat pipe 10 is in use, the fluid 31 inside the heat absorbing section H is heated into steam that flows through the space surrounded by the wick structure 21 in the heat absorbing section H to the heat isolation section A and then the condensing section C. When reached the condensing section C, steam is condensed into a fluid 31 that enters the wick structure 21. Because the wick structure 21 is relatively thinner at the condensing section C, the diameter of the space surrounded by the wick structure 21 inside the condensing section C is relatively greater, the amount of the condensed fluid 31 in the condensing section C is insufficient to block the space surrounded by the wick structure 21 inside the condensing section C, therefore no fluid accumulation will occur. FIG. 3 illustrates the fluid 31 condensed at the wick structure 21. Therefore, the wick structure 21 quickly guides the condensed fluid 31 back to the heat absorbing section H for further circulation, maintaining excellent temperature uniformity and achieving excellent heat transfer effect.
As stated above, the wick structure 21 is relatively thicker at the heat absorbing section H and relatively thinner at the condensing section C. In consequence, the diameter of the space surrounded by the wick structure 21 at the heat absorbing section H is relatively smaller than the diameter of the space surrounded by the wick structure 21 at the condensing section C. Therefore, the steam pressure in the heat absorbing section H is greater than the steam pressure in the condensing section C, facilitating movement of steam toward the condensing section C.
Therefore, the invention effectively eliminates the problems of fluid accumulation and non-uniformity of temperature of the prior art design. By means of the wick thickness variation design, the invention prevents blocking of the space surrounded by the wick structure at the condensing section, eliminating water accumulation and maintaining excellent temperature uniformity.

Claims

1. A heat pipe comprising:

a pipe body, said pipe having two distal ends closed;

a wick structure formed on the inside wall of said pipe body, said wick having a predetermined thickness; and

a working fluid filled in said pipe body;

wherein said pipe body defines a heat absorbing section and a condensing section; the thickness of said wick structure in said heat absorbing section is greater that the thickness of said wick structure in said condensing section.

2. The heat pipe as claimed in claim 1, wherein said pipe body further defines a heat isolation section connected between said heat absorbing section and said condensing section.

3. The heat pipe as claimed in claim 2, wherein the thickness of said wick structure in said heat isolation section is relatively thicker at one end and relatively thinner at an opposite end.

4. The heat pipe as claimed in claim 3, wherein the relatively thicker end of the part of said wick structure in said heat isolation section is close to said heat absorbing section and the relatively thinner end of the part of said wick structure in said heat isolation section is close to said condensing section.

5. The heat pipe as claimed in claim 3, wherein the thickness of said wick structure in said heat isolation section gradually reduces in direction from said heat absorbing section toward said condensing section.