US20080073066A1

US20080073066A1 - Pulsating heat pipe with flexible artery mesh

Info

Publication number: US20080073066A1
Application number: US11/309,745
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: 2006-09-21
Filing date: 2006-09-21
Publication date: 2008-03-27

Abstract

A pulsating heat pipe (10) includes an elongate capillary tube (11), a working fluid (15) disposed within the elongate tube and an artery mesh (13) disposed in the elongate tube. The capillary tube includes a plurality of heat receiving portions (112) located on a first predetermined part of the elongate tube, and a plurality of heat radiating portions (114) located on a second predetermined part of the elongate tube. The heat receiving and heat radiating portions are alternatively disposed on the elongate tube. The working fluid is propelled to flow between the heat receiving and heat radiating portions via a first channel (132) defined in the artery mesh and a second channel (133) defined between the artery mesh and the elongate tube.

Description

FIELD OF THE INVENTION

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

DESCRIPTION OF RELATED ART

Pulsing 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 pulsating heat pipe is usually an elongate capillary tube containing therein a working fluid, which is employed to carry, under phase transitions between liquid state and vapor state, thermal energy from one section of the pulsating heat pipe (typically referring to as the “heating section”) to another section thereof (typically referring to as the “cooling section”). In the pulsating heat pipe, there is no wick structure inside the capillary tube. The working fluid is drawn back to the heating section after it is condensed at the cooling section under a capillary force generated by the capillary tube and a difference of vapor pressure between the two sections of the pulsating heat pipe. This decreases the thermal resistance thereof and therefore prevents the pulsating heat pipe from dry-out at a higher temperature.
However, there is no additional wick structure disposed in the capillary tube. The pulsating heat pipe is operated under the capillary force generated by the capillary tube. The capillary force is weak in conquering gravity of the working fluid. Therefore, during start up of the pulsating heat pipe, the working fluid at the heating section needs to be heated to vaporize an enough inflating force to conquer gravity of the working fluid so that the vaporized working fluid thereat is driven towards the cooling section. Thus, the pulsating heat pipe has troubles to be operated in lower temperature.
Therefore, it is desirable to provide a pulsating heat pipe which has better gravity conquest capability and easily to be operated under a lower temperature.

SUMMARY OF THE INVENTION

The present invention relates to a pulsating heat pipe for removing heat from heat-generating components. The pulsating heat pipe includes an elongate capillary tube, a working fluid disposed within the elongate tube and an artery mesh disposed in the elongate tube. The capillary tube includes a plurality of heat receiving portions located on a first predetermined part of the elongate tube, and a plurality of heat radiating portions located on a second predetermined part of the elongate tube. The heat receiving and heat radiating portions are alternatively disposed on the elongate tube. The working fluid is propelled to flow between the heat receiving and heat radiating portions via a first channel defined in the artery mesh and a second channel defined between the artery mesh and the elongate tube.
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 pulsating heat pipe in accordance with a preferred embodiment of the present invention;

FIG. 2 is an enlarged view of a circled portion II of the pulsating heat pipe of FIG. 1 ;

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

FIG. 4 is a front view of a mesh of the pulsating heat pipe of FIG. 1;

FIG. 5 a transverse cross-sectional view of the mesh of FIG. 4, taken along line V-V thereof; and

FIG. 6 is a pulsating heat pipe in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a pulsating heat pipe 10 in accordance with a preferred embodiment of the present invention. The pulsating heat pipe 10 includes a serpentine, elongate capillary tube 11, a flexible interwoven artery mesh 13 disposed within the elongate capillary tube 11, and a predetermined quantity of condensable bi-phase working fluid 15 (FIG. 2) filled in the elongate capillary tube 11 and the artery mesh 13.
The elongate capillary tube 11 is made of deformable metallic materials, such as copper or aluminum, so it can be bent into a required shape by a suitable bending machine (not shown). Alternatively, the elongate capillary tube 11 may be made of other deformable materials such as polymer or macro-molecular material. The elongate capillary tube 11 is bent into a hand-like shape, having a plurality of heat receiving and heat radiating portions 112, 114 formed on predetermined parts thereof, and a plurality of adiabatic portions 116 formed between the heat receiving and heat radiating portions 112, 114. The heat receiving portions 112 are alternately arranged with the heat radiating portions 114. It is noted that the heat receiving portions 112 are disposed in a heating region H and the heat radiating portions 114 are disposed in a cooling region C. The heating region H is located at fingertips of the hand, while the cooling region C is located near a wrist of the hand. Terminal ends (not labeled) of the metallic elongate capillary tube 11 are hermetically connected with each other to form a close looped flow passage of the working fluid 15. Alternatively, shown in FIG. 6, the terminal ends of the elongate capillary tube 11 may be heretically sealed and separated from each other to form an un-looped flow passage of the working fluid 15. In addition, a filling tube 17 is formed at the cooling region C of the elongate capillary tube 11 for filling and supplying the working fluid 15 into the elongate capillary tube 11.
Referring to FIGS. 2 to 5, the artery mesh 13 is an elongate hollow tube, which is attached to an inner wall of the elongate capillary tube 11 and extends along the entire length of the capillary tube 11. Alternatively, the elongate artery mesh 13 may be divided into a plurality of spaced segments (shown in FIG. 6), which are equidistantly disposed in the elongate capillary tube 11. Further alternatively, the spaced segments may also be not equidistant from each other in some parts of the elongate capillary tube 11. The artery mesh 13 is formed by weaving a plurality of metal wires 131 (FIG. 4), such as copper, or stainless steel wires together. Alternatively, the artery mesh 13 can be formed by weaving a plurality of non-metal threads such as fiber together. A first channel 132 is defined in an inner space of the artery mesh 13, whilst a second channel 133 is defined between an outer wall of the artery mesh 13 and the inner wall of the elongate capillary tube 11. Both first and second channels 132, 133 are for passages of vaporized working fluid 15. A plurality of pores (not shown) is formed in a peripheral wall of the artery mesh 13, which provides a first strong circulation propelling force (capillary action) to the working fluid 15 and communicates the first channel 132 with the second channel 133. The artery mesh 13 has a ring-like transverse cross section, a diameter of which is smaller than a diameter of the elongate capillary tube 11. The artery mesh 13 has a linear contact with the inner wall of the elongate capillary tube 11 thereby defining an adjacent portion 134 contacting with the inner wall of the elongate capillary tube 11 and a distal portion 135 spaced a distance from the inner wall of the elongate capillary tube 11 along a radial direction of the pulsating heat pipe 10. In the present pulsating heat pipe 10, the artery mesh 13 may be loosely inserted into the elongate capillary tube 11 with some portions thereof separating from the inner wall of the elongate capillary tube 11.
Particularly referring to FIG. 1, the working fluid 15 is filled in the artery mesh 13 and the elongate capillary tube 11. The working fluid 15 is usually selected from a liquid such as water, methanol, or alcohol, which has a low boiling point and is compatible with the artery mesh 13. Thus, the working fluid 15 can easily evaporate to vapor when it receives heat at the heating region H of the pulsating heat pipe 10. The elongate capillary tube 11 of the pulsating heat pipe 10 is evacuated and hermetically sealed after the working fluid 15 is injected into the elongate capillary tube 11 and fills the capillary tube 11 and the artery mesh 13. Before operation, capillary effect causes the working fluid 15 to form as piece-wise liquid segments 151 distributed along the elongate capillary tube 11, and vapor bubbles 152 existed between the liquid segments 151. During operation, the heating region H is heated to vaporize the working fluid 15 which generates a vapor pressure thereat, whilst the cooling region C is cooled to condense the vaporized working fluid 15 which generates a negative vapor pressure (attracting force) thereat. Mutual actions between the vapor pressure and the attracting force cooperatively cause the liquid segments 151 and the vapor bubbles 152 to pulsate in and finally generate a second strong circulation propelling force to propel the working fluid 15 to circulate in the capillary tube 11.
In addition, one or a plurality of pressure sensitive small-sized check valves 19 (shown in FIG. 6) may be disposed in the circulation passage of the working fluid 15 for limiting flowing direction of the working fluid 15. Mutual distances between the check valves 19 are balanced. It is noted that as the number of the check valves 19 increases, the circulation of the working fluid 15 becomes strong and fast.
In operation, the heat receiving portions 112 generate the vapor pressure due to the vaporization of the working fluid 15 thereat and the heat radiating portions 114 generate the attracting force due to the condensation of the vapor. The artery mesh 13, and the vapor pressure and attracting force generate the respective first and second strong propelling actions toward a predetermined circulation direction for the working fluid 15 and its vapor. These mutual actions cause the working fluid 15 and its vapor to continue circulation at a high speed in the looped elongate capillary tube 11. The circulating working fluid 15 is vaporized by an amount of heat supplied at the heat receiving portions 112 to form the vapor. The amount of heat is absorbed as a latent heat in the vaporization, and the vapor streams in the first channel 132 of the artery mesh 13 and the second channel 133 between the artery mesh 13 and the looped elongate capillary tube 11. When the stream of vapor reaches the heat radiating portions 114, the stream of vapor is cooled and liquefied to the working fluid 15. During the liquefication, the vapor supplies the amount of heat for the heat radiating portions 114 as the latent heat in condensation to radiate heat externally. In this way, the working fluid 15 circulates within the looped elongate capillary tube 11 and the artery mesh 13 and repeats the vaporization and condensation, i.e., the heat reception and the heat radiation.
In the pulsating heat pipe 10, the first propelling action, i.e., the capillary action generated by the artery mesh 13 helps to conquer the gravity of and propel the working fluid 15 to circulate in the elongate capillary tube 11, so that the required start up pressure generated by heating the heating region H of the pulsating heat pipe 10 is decreased. The required start up temperature of the pulsating heat pipe 10 is accordingly decreased, which results in the pulsating heat pipe 10 being easy to be operated under a lower temperature. In addition, the artery mesh 13 helps to prevent the working fluid 15 from accumulating in some portions of the elongate capillary tube 11, which further decreases the required start up pressure of the pulsating heat pipe 10. Therefore, the pulsating heat pipe 10 is capable of being used for dissipating heat generated by heat sensitive electronic components.
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 pulsating heat pipe comprising:

an elongate capillary tube comprising a plurality of heat receiving portions located on a first predetermined part of the elongate tube, and a plurality of heat radiating portions located on a second predetermined part of the elongate tube, the heat receiving and heat radiating portions being alternatively disposed on the elongate tube;

a working fluid disposed within the elongate tube; and

an artery mesh disposed in the elongate tube, the working fluid being propelled to flow between the heat receiving and heat radiating portions via a first channel defined in the artery mesh and a second channel defined between the artery mesh and the elongate tube.

2. The pulsating heat pipe of claim 1, wherein the artery mesh has an adjacent portion contacting with an inner wall of the capillary tube, and a distant portion spaced at a distance from the inner wall of the capillary tube.

3. The pulsating heat pipe of claim 1, wherein the elongate capillary tube is hand-shaped in profile and has two terminals hermetically connected with each other to form a close looped flow passage of the working fluid.

4. The pulsating heat pipe of claim 1, wherein the artery mesh is an elongate hollow tube formed by weaving a plurality of metal wires.

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

6. The pulsating heat pipe of claim 1, wherein the artery mesh comprises a plurality of spaced segments disposed in the entire elongate capillary tube.

7. The pulsating heat pipe of claim 1, wherein the elongate capillary tube is made of deformable metallic materials.

8. The pulsating heat pipe of claim 1, wherein the working fluid comprises a plurality of liquid segments and vapor bubbles alternately distributed along the elongate capillary tube.

9. The pulsating heat pipe of claim 1 further comprising a filling tube for filling and supplying the working fluid into the elongate capillary tube.

10. The pulsating heat pipe of claim 1 further comprising at least one pressure sensitive check valve disposed in a circulation passage of the working fluid for limiting flowing direction of the working fluid.

11. A pulsating heat pipe comprising:

an elongate tube;

working fluid received in the elongate tube and comprising liquid segments and vapor bubbles distributed between the liquid segments; and

an artery mesh received in the elongate tube, wherein a first channel for movement of the working fluid in the pulsating heat pipe is defined between an outer wall of the artery mesh and the an inner wall of the elongate tube, and a second channel for movement of the working fluid in the pulsating heat pipe is defined in the artery mesh.

12. The pulsating heat pipe of claim 11, wherein the artery mesh has an adjacent side abutting against the inner wall of the elongate tube.

13. The pulsating heat pipe of claim 12, wherein the elongate tube is made of one of aluminum and copper.

14. The pulsating heat pipe of claim 12, wherein the artery mesh is formed by weaving metal wires.

15. The pulsating heat pipe of claim 14, wherein the artery mesh is formed by weaving stainless steel wires.

16. The pulsating heat pipe of claim 14, wherein the artery mesh is formed by weaving copper wires.

17. The pulsating heat pipe of claim 14, wherein the artery mesh is formed by weaving a plurality of fiber together.