US20080078530A1

US20080078530A1 - Loop heat pipe with flexible artery mesh

Info

Publication number: US20080078530A1
Application number: US11/309,808
Authority: US
Inventors: Chang-Shen Chang; Juei-Khai Liu; Chao-Hao Wang; Hsien-Sheng Pei
Original assignee: Foxconn Technology Co Ltd
Current assignee: Foxconn Technology Co Ltd
Priority date: 2006-10-02
Filing date: 2006-10-02
Publication date: 2008-04-03

Abstract

A loop heat pipe (10) includes an evaporator (11) thermally connected with a heat generating electronic component and including a wick structure (112) disposed therein, a condenser (12) thermally connected with a heat dissipating component, a vapor line (13) and a liquid line (14) connecting the evaporator with the condenser to form a closed loop, a predetermined quantity of bi-phase working medium contained in the closed loop, and an artery mesh (15) located within the liquid line.

Description

1. FIELD OF THE INVENTION

The present invention relates generally to a loop heat pipe for transfer or dissipation of heat from heat-generating components, and more particularly to a loop heat pipe with flexible artery mesh disposed therein for improving heat dissipation for the heat-generating components.

2. DESCRIPTION OF RELATED ART

Loop heat pipes have excellent heat transfer performance due to their low thermal resistance, and are therefore an effective means for transfer or dissipation of heat from heat-generating components such as central processing units (CPUs) of computers.
A conventionally loop heat pipe includes an evaporator thermally connected with a CPU and disposing a wick structure therein, a condenser thermally connected with a heat sink, a vapor line and a liquid line disposed between and connecting the evaporator with the condenser, a compensation disposed between the wick structure and the liquid line, and a predetermined quantity of bi-phase working medium contained in the evaporator and the liquid line.
During operation of the loop heat pipe, the working medium in the evaporator absorbs heat from the CPU and vaporizes, thus generating a vapor pressure which propels vaporized working medium towards the condenser via the vapor line. The vaporized working medium dissipates the heat to the heat sink at the condenser and condenses to liquid thereat. The condensed working medium is then propelled through the liquid line, the compensation and the evaporator in that order by the vapor pressure and by capillary action generated by the wick structure. The condensed working medium at the evaporator then evaporates and is condensed to liquid thus perpetuating the cycle.
In the operation of the loop heat pipe, the working medium at the evaporator needs to be heated to vaporize and generate enough vapor pressure to conquer gravitational force acting on the working medium in the liquid line so as to power the circulation of the working fluid. Therefore, a start up temperature must first be achieved before the heat pipe can operate, which troubles the loop heat pipe to be operated in a lower temperature.
Therefore, it is desirable to provide a loop heat pipe which has better gravity conquest capability and easily to be operated under lower temperature.

SUMMARY OF THE INVENTION

The present invention relates to a loop heat pipe for removing heat from heat-generating components. The loop heat pipe includes an evaporator with a wick structure disposed therein and thermally connected with a heat generating electronic component, a condenser thermally connected with a heat dissipating component, a vapor line and a liquid line connecting the evaporator with the condenser to form a closed loop, with a predetermined quantity of bi-phase working medium contained in the closed loop, and an artery mesh disposed within the liquid line.
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

Many aspects of the present invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views:

FIG. 1 is a loop heat pipe in accordance with a preferred embodiment of the present invention;

FIG. 2 is an enlarged transverse cross-sectional view of the loop heat pipe of FIG. 1, taken along line II-II;

FIG. 3 is an enlarged transverse cross-sectional view of the loop heat pipe of FIG. 1, taken along line III-III;

FIG. 4 is an enlarged view of a circled portion IV of the loop heat pipe of FIG. 1;

FIG. 5 is an enlarged transverse cross-sectional view of the loop heat pipe of FIG. 1, taken along line V-V;

FIG. 6 is a front view of an artery mesh of the loop heat pipe of FIG. 1; and

FIG. 7 a transverse cross-sectional view of the artery mesh of the FIG. 6, taken along line VII-VII.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a loop heat pipe 10 in accordance with a first embodiment of the present invention. The loop heat pipe 10 includes an evaporator 11 thermally connected with a heat generating electronic component such as a CPU (not shown), a condenser 12 thermally connected with a heat dissipating component such as a heat sink (not shown), vapor and liquid lines 13, 14 connecting the evaporator 11 with the condenser 12 to form a closed loop, a predetermined quantity of bi-phase working medium (not labeled) contained in the closed loop, and a flexible interwoven artery mesh 15 disposed within the liquid line 14.
Referring particularly to FIGS. 2 and 3, the evaporator 11 is a hollow tube which contains a wick structure 112 coextensive with a central longitudinal axis of the evaporator 11. The wick structure 112 is tubular shaped in profile and has a column shaped outer wall 113 contacting with an inner wall of the evaporator 11. The wick structure 112 has a closed end 114 abutting against the liquid line 14 and an open end 115 abutting against the vapor line 13. A column-shaped vapor channel 116 communicating with an inner space of the vapor line 13 is defined in a middle portion along a central longitudinal axis of the wick structure 112. A diameter of the vapor channel 116 is larger than a diameter of an inner wall of the vapor line 13, thus increasing the flow rate of vaporized working medium entering into the inner space of the vapor line 13. The wick structure 112 in the evaporator 11 of the loop heat pipe 10 can, for example, consist of porous structures, such as fine grooves integrally formed at the inner wall of the evaporator 11, screen mesh or fiber inserted into the evaporator 11 and held against the inner wall thereof, or sintered powders combined to the inner wall of the evaporator 11 using a sintering process.
The condenser 12 is disposed distant from the evaporator 11 and has a lower temperature than that of the evaporator 11, thus causing the vaporized working medium to be condensed. The condenser 12 is a heat sink including a plurality of fins (not shown) for increasing heat dissipation area thereof so as to benefit the condensation of the vaporized working medium. An end of the liquid line 14 extends into the condenser 12 and connects with the vapor line 13 so that the vaporized working medium is condensed at the condenser 12 and is directly propelled towards the evaporator 11. Alternatively, the condenser 12 may be a cooling chamber, with the liquid line 14 and the vapor line 13 separating from each other and respectively connecting with two ends of the chamber. Under this status, the vaporized working medium enters into the condenser 12 and is condensed thereat. The condenser working medium in the condenser 12 enters into the liquid line 14 and is propelled towards the evaporator 11.
The vapor and the liquid lines 13, 14 are made of deformable materials compatible with the working medium, such as aluminum, stainless steel, or plastics. Each of the vapor and liquid lines 13, 14 includes two parallel sections 13 a and 13 b/14 a and 14 b with two corresponding ends thereof connecting with the respective ends of the evaporator 11 and the condenser 12, and a perpendicular section 13 c/14 c with two ends thereof connecting with the other two ends of the parallel sections 13 a and 13 b/14 a and 14 b.
The working medium is usually selected from a liquid which has a low boiling point such as water, methanol, or alcohol. Thus, the working medium can easily evaporate to vapor when it receives heat in the evaporator 11 and condense to liquid when it dissipates heat in the condenser 12.
Referring to FIGS. 4 to 7, the artery mesh 15 is an elongated hollow tube, which is attached to and extends along an inner wall of the liquid line 14. The artery mesh 15 is woven from a plurality of metal wires 151 (FIG. 6), such as copper, or stainless steel wires. Alternatively, the artery mesh 15 can be formed by weaving a plurality of non-metal threads such as fiber together. A first channel 152 is defined in an inner space of the artery mesh 15, whilst a second channel 153 is defined between an outer wall of the artery mesh 15 and the inner wall of the liquid line 14 for passage of the condensed working medium. A plurality of pores (not shown) are formed in a peripheral wall of the artery mesh 15, which provide capillary action to the working medium and communicate the first channel 152 with the second channel 153. The artery mesh 15 has a ring-like transverse cross section, a diameter of which is smaller than a diameter of the liquid line 14. The artery mesh 15 has a linear contact with the inner wall of the liquid line 14 thereby defining an adjacent portion 154 contacting with the inner wall of the liquid line 14 and a distal portion 155 spaced a distance from the inner wall of the liquid line 14 along a radial direction of the loop heat pipe 10. In the present loop heat pipe 10, the artery mesh 15 may be loosely inserted into the liquid line 14 with some portions thereof isolated from the inner walls thereof.
In operation of the loop heat pipe 10, the working medium in the evaporator 11 absorbs heat from the heat generating electronic component and evaporates. A vapor pressure is generated due to the vaporization of the working medium and propels the vaporized working medium into the vapor line 13 and towards the condenser 12. The vaporized working medium looses its heat to the heat dissipating component at the condenser 12 and condenses to liquid to accumulate in the condenser 12 and the artery mesh 15 thereat. The condensed working medium in the condenser 12 is propelled towards the liquid line 14 and into the evaporator 11 via the vapor pressure and the capillary force generated by the artery mesh 15 and the wick structure 112. The condensed working medium then evaporates to vapor thus perpetuating a cycle in the loop heat pipe and continuously absorbing heat from the heat generating electronic component and dissipate the heat to the heat dissipating component.
In the present loop heat pipe 10, the capillary force generated by the artery mesh 15 conquers the gravity action of the condensed working medium and helps to propel the condensed working medium to enter into the evaporator 11 via the liquid line 14. Therefore, the vapor pressure exerted on the condensed working medium is decreased, and the start up temperature needed to generate the vapor pressure is accordingly decreased. This results in the dependence of the start up temperature of the loop heat pipe 10 not being limited by the gravity action of the condensed working medium. Thus, the loop heat pipe 10 is easy to be operated under a lower temperature and is preferably used for dissipating heat generated by heat sensitive electronic components.
As compared to a conventional loop heat pipe with a plurality of vapor channels defined between an inner wall of the evaporator and an outer wall of the wick structure, the wick structure 112 of the present loop heat pipe 10 has a larger contacting area for the inner wall of the evaporator 11. The larger contacting area of the inner wall of the evaporator enables the heat generating electronic component to transfer more heat to the working medium in the evaporator 11 and therefore increases the heat dissipation efficiency of the present loop heat pipe 10. Moreover, the wick structure 112 has a simpler structure than the conventional loop heat pipe, which simplifies the manufacture thereof. Furthermore, a part of the condensed working medium is accommodated in the artery mesh of the present loop heat pipe 10, which compensates for the working medium in the evaporator 11 which evaporates to vapor, thus preventing the drying out of the evaporator. Thus, there is no need to for additional compensation in the evaporator 11 thus preventing the working medium therein from drying out, which reduces the volume of the evaporator 11 of the present loop heat pipe 10.
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 loop heat pipe comprising:

an evaporator configured for thermally connecting with a heat generating electronic component and comprising a wick structure disposed therein;

a condenser configured for thermally connecting with a heat dissipating component;

a vapor line and a liquid line connecting the evaporator with the condenser to form a closed loop;

a predetermined quantity of bi-phase working medium filled in the closed loop; and

an artery mesh positioned within the liquid line.

2. The loop heat pipe of claim 1, wherein the artery mesh has a linear contact with an inner wall of the liquid line.

3. The loop heat pipe of claim 1, wherein a diameter of a cross section of the artery mesh is smaller than that of the liquid line.

4. The loop heat pipe of claim 1, wherein the artery mesh is a flexible hollow tube woven from a plurality of metal wires.

5. The loop heat pipe of claim 4, wherein the material of the metal wires is selected from a group consisting of copper wires and stainless steel wires.

6. The loop heat pipe of claim 1, wherein the artery mesh is formed by weaving a plurality of fiber together.

7. The loop heat pipe of claim 1, wherein the wick structure is selected from the group consisting of grooves, sintered powder, fiber and screen mesh.

8. The loop heat pipe of claim 1, wherein the wick structure is tubular shaped in profile and disposed in an inner wall of the evaporator.

9. The loop heat pipe of claim 1, wherein the wick structure has a closed end contacting with the liquid line and an open end communicating with the vapor line, a vapor channel being defined in a middle portion of the open end.

10. A loop heat pipe comprising:

a vapor line connecting an open end of the wick structure with the condenser;

a liquid line connecting a closed end of the wick structure with the condenser;

a vapor channel defined in a middle portion of the open end of the wick structure and communicating with the vapor line;

an artery mesh positioned within the liquid line; and

a predetermined quantity of bi-phase working medium contained in the loop heat pipe.

11. The loop heat pipe of claim 10, wherein the artery mesh is a hollow tube in contact with an inner wall of the liquid line.

12. The loop heat pipe of claim 10, wherein a diameter of a cross section of the artery mesh is smaller than that of the liquid line.

13. The loop heat pipe of claim 10, wherein the artery mesh is woven from a plurality of metal wires selected from a group consisting of copper and stainless steel wires.

14. The loop heat pipe of claim 10, wherein the artery mesh is tightly attached to inner walls of the liquid line.

15. The loop heat pipe of claim 10, wherein the wick structure has a column shaped outer wall contacting with an inner wall of the evaporator.

16. The loop heat pipe of claim 10, wherein a diameter of the vapor channel is larger than a diameter of an inner wall of the vapor line.