US20060207751A1

US20060207751A1 - Heat pipe

Info

Publication number: US20060207751A1
Application number: US11/292,253
Authority: US
Inventors: Chu-Wan Hong; Ching-Tai Cheng; Jung-Yuan Wu; Chang-Ting Lo
Original assignee: Foxconn Technology Co Ltd
Current assignee: Foxconn Technology Co Ltd
Priority date: 2005-03-18
Filing date: 2005-12-01
Publication date: 2006-09-21
Also published as: TWI259895B; TW200634279A

Abstract

A heat pipe includes a hollow tube, a working medium filled in the tube, and a wick structure disposed in and contacting with the tube. The wick structure is formed by weaving first wires and second wires together. The second wires each have two opposite major surfaces. A portion of one of the two major surfaces contacts with an interior wall of the tube.

Description

TECHNICAL FIELD

The present invention relates to a heat pipe, and more specifically to a heat pipe having a better heat exchange capability by increasing contacting areas between a wick structure and an interior wall of the heat pipe.

BACKGROUND

In nowadays, heat pipes are always used in a heat dissipating apparatus for dissipating heat generated by high frequency electronic components. Each of the heat pipes includes an evaporator section adjacent to the electronic components and a condenser section apart from the electronic components. In the heat dissipating apparatus, the heat pipes are usually received in holes disposed in a group of spaced cooling fins with the evaporator sections and the condenser sections of the heat pipes separately positioned at two ends of the group of the cooling fins, for conducting heat from the electronic components to the fins apart from the electronic components. A dissipating fan is mounted to the cooling fins for generating airflows facing to spaces formed between two adjacent cooling fins to take away the heat conducted to the cooling fins from the electronic components.
In working procession of the heat dissipating apparatus, a tube of each heat pipe absorbs heat generated by the electronic components and conducts the heat to a wick structure contacted with an inner surface of the tube. At the evaporator section of the heat pipe, a working fluid filled in the heat pipe absorbs heat from the wick structure and the tube for evaporating itself to a steam. This increases a vapor pressure in a region of the evaporator section of the heat pipe and causes the steam to flow through a vapor space of the heat pipe toward the condenser section. Since the condenser section of the heat pipe being cooled by the cooling fins located thereat, the steam condenses in the condenser section by giving up the heat absorbed by the working fluid at the evaporator section, thereby changing the steam to a liquid. The liquid returns to the evaporator section by capillary action of the wick structure. With the heat generated by the electronic components being absorbed by the working fluid at the evaporator section of the heat pipe, and the heat being given away by the evaporated working fluid at the condenser section of the heat pipe, a circulation of the working fluid are formed in the heat pipe. The heat generated by the electronic components is continuously taken away by the working fluid of the heat pipe during the circulation.
In this heat dissipating procession, the heat of the wick structure absorbed from the inner surface of the tube of the heat pipe acts an important influence of the heat transferring between the tube and the working fluid, and further influences the evaporating velocity of the working fluid and the heat transfer capability of the heat pipe. The additional mesh type wick structure is woven by a plurality of wires, the cross sectional of the wire is a circle. This makes a contacting area of the circular wire and the inner surface of the heat pipe to be a line. The linear contacting between the circular wire of the wick structure and the inner surface of the tube reduces the heat conducting capability of the heat pipe. So how to increase the contacting area of the wick structure and the inner surface of the heat pipe is a problem we want to solve.

SUMMARY OF THE INVENTION

According to a preferred embodiment of the present invention, a heat pipe includes a hollow tube, a working medium filled in the tube, and a wick structure disposed in and contacting with the tube. The wick structure is formed by weaving a plurality of first and second wires. The second wires each have two opposite major surfaces. One of the two major surface contacts with an interior wall of the tube, whereby the wick structure has a large surface in contacting with the tube. Accordingly, heat transfer capability of the heat pipe is improved.
Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiment when taken in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a heat pipe according to a preferred embodiment of the present invention, wherein some portions of the heat pipe are cut away to show an internal structure thereof;
FIG. 2 is a perspective view of a wick structure of the heat pipe of FIG. 1 in an unrolled condition;
FIG. 3 is an enlarged view of a circled portion of FIG. 2 indicated by III;
FIG. 4 is an enlarged perspective view of a portion of a wick structure in an unrolled condition according to another embodiment of the present invention; and
FIG. 5 is a view similar to FIG. 4, showing a wick structure according to a third embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 1, a heat pipe 10 according to a first embodiment of the present invention includes a hollow tube 12, a wick structure 14 disposed in and contacting with an interior wall of the tube 12, and a working medium (not shown) filled in the tube 12.
The tube 12 is made of a material having a good heat conductivity, so that the tube 12 can transfer a heat absorbed from a heat generating component (not shown) to the wick structure 14 and the working medium filled in the tube 12 rapidly. In this embodiment, the tube 12 is made of copper.
The working medium is made of a fluid having a lower boiling point, such as water, alcohol, kerosene, and paraffin. The tube 12 is vacuumed. The working medium filled in the tube 12 of the heat pipe 10 can easily become vapor after absorbing heat from the tube 12. The vapor is capable of moving from an evaporator portion toward a condenser portion of the tube 12. The vapor condenses into liquid at the condenser portion. The liquid is drawn back to the evaporator portion by capillary force of the wick structure 14 of the heat pipe 10.
Also referring to FIGS. 2 and 3, the wick structure 14 is formed by weaving a plurality of first wires 141 and a plurality of second wires 142 together. The first wires 141 each have a rod configuration while the second wires 142 each has a stripe configuration. The first wires 141 each have a round cross section and the second wires 142 each have a rectangular-shaped cross section. The second wires 142 are more flexible than the first wires 141. After rolled and inserted into the tube 12, the first wires 141 extend along an axial direction of the tube 12, while the second wires 142 extend along a circumferential direction of the tube 12. Each second wire 142 has two opposite major surfaces 143, 144 contacting with the first wires 141 in an alternated manner. After rolled and inserted into the tube 12, the wick structure 14 has an outer surface 145 contacting with the interior wall of the tube 12. The outer surface 145 is constituted by a portion of a corresponding one of the opposite major surfaces 143, 144 of each second wire 142 not engaging with the first wires 141. Since the major surfaces 143, 144 of the second wires 142 are planar, the outer surface 145 of the wick structure 14 can have a larger area in contacting with the interior wall of the tube 12 in comparison with the prior art. This increases the heat transfer between the interior wall of the tube 12 and the wick structure 14 of the heat pipe 10, thereby improving the heat transfer capability of the heat pipe 10.
Moreover, in the present invention, since the area of the contacting surface between the tube 12 and the wick structure 14 is increased, the heat absorbed by the tube 12 from the heat generating component can be quickly transferred to the wick structure 14 and then to the working medium. Accordingly, the evaporation speed of the working medium is increased, and the heat transfer capability of the heat pipe 10 with this wick structure 14 is improved.
Referring to FIGS. 4 and 5, wick structures 14′, 14″ in accordance with the second and third embodiments of the present invention are shown. Except the difference regarding the cross section of the first wires, the second and third embodiments are substantially the same as the first embodiment. In the second embodiment, the cross section of each of the first wires 141′ is changed to be substantially square. In the third embodiment, the cross section of the first wires 141″ is changed to be I-shaped. Alternatively, the cross section of the second wires 142 may be in square, or I-shaped. This makes the first and second wires 141, 142 constituting the wick structure 14 have the same or two different shapes of cross sections. The first wires 141 may extend along a direction defining a sharp angle with the axial direction of the tube 12, while the second wires 142 may extend along a direction defining a sharp angle with the circumferential direction of the tube 12. The second wires 142 may have the same flexibility with the first wires 141. Thus, the first wires 141 may be in ripple-like style and intersect with the second wires 142.
In the present invention, the first wires 141, 141′, 141″ and the second wires 142 are made of metallic materials such as copper, aluminum, nickel, and stainless steel, which have good heat conductivity and strength. The wick structure 14, 14′, 14″ may be woven by wires of one material or two different materials.
In the preferred embodiments of the present invention, the wick structure 14, 14′, 14″ can have a better contact with the interior wall of the tube 12 by inserting a supporting member into the tube 12. The wick structures 14, 14′, 14″ and the support member can be further sintered to integrally connect with each other.
It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. A heat pipe comprising:

a hollow tube;

a working medium filled in the tube; and

a wick structure disposed in and contacting with the tube, the wick structure comprising a plurality of first and second wires woven together, the wick structure contacting an interior wall of the tube mainly by the second wires, and the first wires and the second wires having different cross sections.

2. The heat pipe as described in claim 1, wherein the second wires are more flexible than the first wires.

3. The heat pipe as described in claim 2, wherein each of the first wires has a cross section which is one of round, square, and I-shaped.

4. The heat pipe as described in claim 3, wherein each of the second wires has a stripe-like configuration.

5. The heat pipe as described in claim 1, wherein the first wires and second wires are made of different materials, respectively.

6. The heat pipe as described in claim 5, wherein the first wires and second wires are made of different metals.

7. The heat pipe as described in claim 1, wherein the first wires extend along an axial direction of the tube while the second wires extend along a circumferential direction of the tube.

8. The heat pipe as described in claim 1, wherein the second wires each have two opposite major surfaces, one of the two opposite major surfaces contacting with the interior wall of the tube.

9. The heat pipe as described in claim 1, wherein the wires are made of at least one of copper, aluminum, and stainless steel.

10. A heat pipe comprising:

a tube;

a wick structure rolled and inserted into the tube, the wick structure having first wires and second wires woven together, the first wires extending along an axial direction of the tube while the second wires extending along a circumferential direction of the tube, the second wires each being made of a stripe having two major surfaces alternately contacting the first wires, a portion of one of the two major surfaces of the second wires contacting an interior wall of the tube.

11. The heat pipe of claim 10, wherein the first wires each have a round cross section.

12. The heat pipe of claim 10, wherein the first wires each have a substantially square cross section.

13. The heat pipe of claim 10, wherein the first wires each have an I-shaped cross section.

14. The heat pipe of claim 10, wherein the second wires are more flexible than the first wire.

15. The heat pipe of claim 10, wherein the wires are made of metal.

16. The heat pipe of claim 10, wherein the first and second wires are made of different metals, respectively.

17. A heat pipe comprising:

a tube made of metal;

a wick structure attached on an interior wall of the tube and having first metal wires and second metal wires woven together, wherein the first metal wires extend along an axial direction of the tube and the second metal wires extend along a circumferential direction of the tube, wherein the second metal wires are more flexible than the first metal wires.

18. The heat pipe of claim 17, wherein the second metal wires each have a rectangular cross section with two major surface, a portion of one of the two major surface being in contact with the interior wall of the heat pipe.

19. The heat pipe of claim 18, wherein the first metal wires each have a round cross section.

20. The heat pipe of claim 18, wherein the first metal wires each have an I-shaped cross section.