US20060260786A1

US20060260786A1 - Composite wick structure of heat pipe

Info

Publication number: US20060260786A1
Application number: US11/134,339
Authority: US
Inventors: Hul-Chun Hsu
Original assignee: FAFFE Ltd
Current assignee: Jaffe Ltd; FAFFE Ltd
Priority date: 2005-05-23
Filing date: 2005-05-23
Publication date: 2006-11-23

Abstract

A composite multi-layer wick structure includes a tubular member with an internal sidewall, and a composite wick structure including a multi-layer woven mesh and a sintered-powder layer. The multi-layer woven mesh is curled to cover on and extend over the internal sidewall. The sintered-powder layer is coated on a portion of the multi-layer woven mesh and the internal sidewall to extend along a longitudinal direction of the tubular member. By the strong capillary force provided by the sintered-powder layer, the working fluid at the liquid phase easily reflows back to the bottom of the heat pipe, such that the heat transmission efficiency is greatly enhanced.

Description

BACKGROUND OF THE INVENTION

The present invention relates in general to a composite wick structure of a heat pipe, and more particularly, to a composite wick structure fabricated from a multi-layer woven mesh and a sintered powder layer.
Having the features of high heat transmission capability, high-speed heat conductance, high thermal conductivity, light weight, mobile-elements free, simple structure, the versatile application, and low power for heat transmission, heat pipes have been popularly applied in heat dissipation devices in the industry. The conventional heat pipe includes a wick structure on an internal sidewall of a tubular member. The wick structure typically includes a woven mesh or sintered powder to aid in transmission of working fluid.
However, the woven mesh or the sintered powder each has advantages and drawbacks.
For example, the fine and dense structure of the sintered-powder wick structure provides better capillary force for reflow of the liquid-state working fluid. However, during fabrication, an axial rod has to be inserted into the tubular member to serve as a support member of the wick structure during the sintering process, so as to avoid collapse of the powdered which has not been sintered yet. Therefore, the thickness of the sintered powder wick structure is thicker. Consequently, the capillary thermal resistance is increased to be disadvantageous to the heat transmission. Further, requirement of the axial rod hinders the mass production of the heat pipe and causes fabrication and quality issues of the heat pipe.
The woven mesh wick structure does not require the axial rod, such that the problems of the sintered powder wick structure do not encounter. Further, the woven mesh wick structure is more easily to fabricate compared to the sintered-powder wick structure. However, as the woven mesh is made by weaving metal wires, the porosities are larger to provide a poor capillary effect. The working fluid is less easily to reflow, and the thermal conduction efficiency is affected.
Thus, there still is a need in the art to address the aforementioned deficiencies and inadequacies.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a composite wick structure of a heat pipe. The composite structure adapts the advantages of both the multi-layer woven-mesh and the sintered-powder wick structure, such that the transmission capability of the wick structure is maintained, and the heat conduction performance of the heat pipe is improved, while the problems caused by the axial rod are resolved.
A heat pipe provided by the present invention includes a tubular member with an internal sidewall, and a composite wick structure including a multi-layer woven mesh and a sintered-powder layer. The multi-layer woven mesh is curled to cover on and extend over the internal sidewall. The sintered-powder layer is coated on a portion of the multi-layer woven mesh and the internal sidewall to extend along a longitudinal direction of the tubular member. By the strong capillary force provided by the sintered-powder layer, the working fluid at the liquid phase easily reflows back to the bottom of the heat pipe, such that the heat transmission efficiency is greatly enhanced.
These and other objectives of the present invention will become obvious to those of ordinary skill in the art after reading the following detailed description of preferred embodiments.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

These as well as other features of the present invention will become more apparent upon reference to the drawings therein:
FIG. 1 shows an exploded view of a multi-layer woven mesh installing in a heat pipe;
FIG. 2 shows a cross sectional view of the heat pipe with the multi-layer woven mesh;
FIG. 3 shows a cross sectional view of a composite wick structure attached to heat pipe; and
FIG. 4 shows a cross sectional view along the longitudinal direction of the heat pipe in operation.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
FIGS. 1 and 2 illustrate an exploded view and a cross sectional view of a heat pipe with a multi-layer woven mesh, respectively. The heat pipe 1 comprises a tubular member 10 and the multi-layer woven mesh 110.
The tubular member 10 is preferably in the form of a cylindrical hollow tube having an internal sidewall 102 and two open ends 100, 101. After filling a working fluid, a vacuum process is performed so that the tubular member 10 can be closed and sealed at both ends 100, 101 by a shrinking and sealing process.
Referring further to FIG. 3, a composite wick structure 11 of the present invention attached to the internal sidewall 102 of the tubular member 10 includes the multi-layer woven mesh 110 extending all over the sidewall 102 and a sintered-powder layer 111 formed on at least a portion of the multi-layer woven mesh 110 and the sidewall 102. The multi-layer woven mesh 110 is first curled to be put into the tubular member 10 of the heat pipe 1. At this time, the multi-layer woven mesh 110 has not formed a close circumference. However, after a shrinking process, the circumference of the multi-layer woven mesh 110 will be close to form a cylindrical shape so that the multi-layer woven mesh 110 is securely attached on the sidewall 102 of the heat pipe 1. The sintered-powder layer 111 lays on a portion of the multi-layer woven mesh 110 and the sidewall 102 to extend along a longitudinal direction of the tubular member 10. As the sintered-powder layer 111 does not have to cover the whole area of the multi-layer woven mesh 110, that is, the internal sidewall 102 of the tubular member 10, the traditional axial rod is not required. To form the sintered-powder layer 111, the powder to be sintered is disposed inside of the tubular member 10. The tubular member 10 is laid down with the side at which sintered-powder layer 111 facing downwardly for performing sintering.
By the above processes, a composite wick structure is obtained.
Together referring to FIGS. 3 and 4, when a heat source starts to generate heat, the working fluid in the heat pipe absorbs the heat and is evaporated into a gas. The gas is then condensed into a liquid absorbed by the wick structure 11 around the internal sidewall 102 of the tubular member 10. Meanwhile, the sintered-powder layer 111 has the better capillary effect to instantly reflow the work fluid back to the location of the heat source. On the other hand, some liquid working fluid at the woven mesh 110 will also flow to the sintered-powder layer 111 along circular direction because the flowing rate is faster at sintered-powder layer 111. Thereby, the reflow speed of the working fluid is greatly increased to enhance the heat transmission efficiency.
Therefore, the composite wick 11 of the heat pipe 1 includes both the advantages of the multi-layer woven mesh 110 and the sintered-powder layer 111. The sintered-powder layer 111 provides better capillary force for reflow of the liquid-state working fluids without need of the axial rod anymore. Meanwhile, the multi-layer woven mesh 110 is convenient for installation with secure attachment to the sidewall 102 of the tubular member 10. The multi-layer woven mesh 110 is not easy to collapse when a high-temperature annealing process is performed so that the wick structure 11 will have a reliable support.
This disclosure provides exemplary embodiments of wick structure of a heat pipe. The scope of this disclosure is not limited by these exemplary embodiments. Numerous variations, whether explicitly provided for by the specification or implied by the specification, such as variations in shape, structure, dimension, type of material or manufacturing process may be implemented by one of skill in the art in view of this disclosure.

Claims

1. A heat pipe comprising:

a tubular member with an internal sidewall; and

a composite wick structure including a multi-layer woven mesh curled to cover on and extend over the internal sidewall, and a sintered-powder layer coated on a portion of the multi-layer woven mesh and the internal sidewall to extend along a longitudinal direction of the tubular member.

2. The heat pipe of claim 1, wherein the multi-layer woven mesh is formed a cylindrical shape to securely attached to the tubular member.