US20140150995A1

US20140150995A1 - Heat pipe and method for manufacturing the same

Info

Publication number: US20140150995A1
Application number: US13/730,623
Authority: US
Inventors: Sheng-Liang Dai; Jia-Hong Wu
Original assignee: Furui Precise Component Kunshan Co Ltd; Foxconn Technology Co Ltd
Current assignee: Furui Precise Component Kunshan Co Ltd; Foxconn Technology Co Ltd
Priority date: 2012-12-04
Filing date: 2012-12-28
Publication date: 2014-06-05
Also published as: TW201423021A; CN103851940A; CN103851940B; TWI586929B

Abstract

An exemplary heat pipe includes a hollow tube, a wick structure configured on an inner surface of the tube and a working medium formed in the tube. Two ends of the tube are sealed and the tube defining a chamber therein. The tube comprises an evaporating section and a condensing section, and the evaporating section is isolated from the condensing section. The wick structure extends from the evaporating section to the condensing section along the inner surface of the tube to form a working medium channel. A pair of through holes is defined in each of the evaporating section and the condensing section of the tube. A pair of metal pipes communicate the through holes of the evaporating section with those of the condensing section to form a pair of vapor channels. A method for manufacturing the heat pipe is also provided.

Description

BACKGROUND

1. Technical Field
The present invention relates generally to heat pipes and methods for manufacturing heat pipes.
2. Description of Related Art
Currently, heat pipes are widely used for removing heat from heat-generating components such as electrical devices in computers. A heat pipe includes a sealed tube held in vacuum but also containing a working medium therein. The working medium is employed to carry, under phase transitions between a liquid state and a vapor state, thermal energy from an evaporator section to a condenser section of the heat pipe. Preferably a wick structure is provided inside the heat pipe, lining an inner wall of the tube, for drawing the working medium back to the evaporator section after it is condensed at the condenser section. In a traditional heat pipe, a vapor channel is defined in a middle of the tube, with the wick structure surrounding the vapor channel. The vapor flows along the vapor channel in a longitudinal direction, and the liquid working medium flows in the wick structure reversely. A shear stress is generated between the vapor and the liquid working medium when they are flowing, and the shear stress reduces the heat transferring performance of the heat pipe.
Therefore, a heat pipe and a method for manufacturing the heat pipe which are capable of overcoming the above described shortcomings are desired.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present embodiments 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 embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a longitudinal cross-sectional view of a heat pipe in accordance with a first embodiment of the present invention.

FIGS. 2-7 are schematic, cross-sectional views showing sequential steps of an exemplary method for manufacturing the heat pipe of FIG. 1.

FIG. 8 is a longitudinal cross-sectional view of a heat pipe in accordance with a second embodiment of the present invention.

DETAILED DESCRIPTION

Referring to FIG. 1, a heat pipe 1 in accordance with a first embodiment of the present invention includes a hollow tube 10 with a wick structure 11 configured on an inner surface of the hollow tube 10. Two ends of the tube 10 are sealed, so that the tube 10 defines a chamber 12 therein. A working medium is provided in the chamber 12. The tube 10 is symmetrical along a central axis thereof.
The tube 10 forms a reduced section 13 at an intermediate position thereof. The tube 10 includes an evaporating section 14 and a condensing section 15 located adjacent to two ends of the reduced section 13, respectively. The evaporating section 14 is isolated from the condensing section 15, and a length of the evaporating section 14 is less than that of the condensing section 15. An inner diameter and an outer diameter of the evaporating section 14 are equal to those of the condensing section 15, respectively. The reduced section 13 has a middle portion 131, and two end portions 132 located at two ends of the middle portion 131, respectively. An inner diameter and an outer diameter of the middle portion 131 are constant, and both the inner and outer diameters are less than those of the evaporating section 14. An inner diameter and an outer diameter of each end portion 132 respectively increase along a direction away from the middle portion 131, until the inner diameter and the outer diameter of the end portion 132 are equal to those of the corresponding evaporating section 14 or condensing section 15, respectively.
The tube 10 has a metal layer 16 formed therein, and the metal layer 16 is symmetrical about the central axis of the tube 10. The metal layer 16 includes a tapered portion 161 and a cylindrical portion 162 connected to a right end of the tapered portion 161. The tapered portion 161 tapers from the cylindrical portion 162 (in a direction from the evaporating section 14 to the condensing section 15) until the tapered portion 161 terminates at a closed, pointed end. In this embodiment, the tapered portion 161 of the metal layer 16 is a hollow tapered portion. The tapered portion 161 is parallel to a right one of the end portions 132, and abuts the wick structure 11 of the right end portion 132. Thus, a right section of the tapered portion 161 is attached to the wick structure 11 of the right end portion 132. In addition, the cylindrical portion 162 of the metal layer 16 is attached to the wick structure 11 of the evaporating section 14. Accordingly, the chamber 12 of the tube 10 is divided into two parts by the metal layer 16, with the two parts corresponding to the evaporating section 14 and the condensing section 15.
The wick structure 11 extends from the evaporating section 14 to the condensing section 15 along the inner surface of the tube 10, thereby forming a working medium channel. Two through holes 17 are defined in each of the evaporating section 14 and the condensing section 15 of the tube 10. Two hollow metal pipes 18 are provided. One of the hollow metal pipes 18 communicates one of the through holes 17 of the evaporating section 14 with one of the through holes 17 of the condensing section 15 at a same side of the tube 10. The other hollow metal pipe 18 communicates the other through hole 17 of the evaporating section 14 with the other through hole 17 of the condensing section 15 at another same side of the tube 10. Thereby, two vapor channels 181 are defined by the hollow metal pipes 18.
In operation, the evaporating section 14 of the heat pipe 1 is put in thermal contact with a heat generating electronic component (not shown). The working medium in the heat pipe 1 is vaporized after receiving the heat generated by the heat generating electronic component, and the vapor exerts pressure on the metal layer 16. However, the tapered portion 161 of the metal layer 16 tapers in the direction from the evaporating section 14 to the condensing section 15 until the tapered portion 161 terminates at the closed, pointed end. Accordingly, the vapor is blocked from moving directly toward to the condensing section 15, and instead flows to the condensing section 15 via the two vapor channels 181. The vapor condenses into liquid state working medium slowly as it flows through the two vapor channels 181, and then flows into the condensing section 15. Thus, the pressure in the chamber 12 at the condensing section 15 is decreased. The liquid working medium is drawn back to the evaporating section 14 by the wick structure 11 provided on the inner surface of the tube 10.
Therefore the flow of working medium is circulatory along two closed loops that are joined at the tube 10. The flow of working medium along each of the loops is essentially unidirectional, and the flow of working medium along the tube 10 where the loops are joined is also unidirectional. This arrangement avoids or even completely eliminates shear stress that is liable to be generated between vapor and liquid working medium when the vapor and liquid working medium are flowing in opposite directions along paths that are adjacent to each other. Thus, the heat transferring performance of the heat pipe 1 can be improved.
It is understood that in alternative embodiments, the evaporating section 14 and the condensing section 15 can be isolated from each other by other means. That is, other heat pipes are not limited to using the metal layer 16 of the first embodiment.
Referring to FIGS. 2-7, an exemplary method for manufacturing the heat pipe 1 includes steps as described below.
Referring to FIG. 2, a tube 20 is provided, with two ends of the tube 20 being open. The tube 20 is formed with a wick structure 21 on an inner surface thereof, and defines a chamber 22 therein. In this embodiment, the tube 20 is made of a highly thermal conductive material such as copper or aluminum. A transverse cross-section of the tube 20 is a circular ring, and the tube 20 defines a central axis. The wick structure 21 extends along a longitudinal direction of the tube 20. The wick structure 21 is usually a porous structure selected from fine grooves, sintered powder, screen mesh, or bundles of fiber, and provides a capillary force to drive working medium in the tube 20 to flow.
Referring to FIG. 3, a cylindrical metal layer 30 is provided and located in the chamber 22 of the tube 20. The metal layer 30 is attached to the wick structure 21 of the tube 20. The metal layer 30 is close to but spaced from a right end of the tube 20. In this embodiment, a length of the metal layer 30 is 20-60 mm (millimeters), and the metal layer is made of high toughness material such as copper or aluminum.
Referring to FIGS. 4 and 5, a portion of the tube 20 containing a left portion of the metal layer 30 is pressed to obtain a reduced section 40 of the tube 20 containing the pressed portion of the metal layer 30. Specifically, a compressing tool 50 is provided. The compressing tool 50 may for example include a pair of opposite pressing dies. The compressing tool 50 is positioned corresponding to the left portion of the metal layer 30. The compressing tool 50 compresses the left portion of the metal layer 30 along radial directions of the tube 20 until the left end of the left portion of the metal layer 30 is closed. Because the metal layer 30 is made of high toughness material, the metal layer 30 attaches to the wick structure 21 of the tube 20. In this embodiment, the reduced section 40 divides the tube 20 into the evaporating section 23 and the condensing section 24, with the reduced section 40 intervening between the evaporating section 23 and the condensing section 24. Thus, the evaporating section 23 is isolated from the condensing section 24. A length of the evaporating section 23 is less than that of the condensing section 24.
The reduced section 40 has a middle portion 41, and two end portions 42 located at two ends of the middle portion 41. An inner diameter and an outer diameter of the middle portion 41 are constant, and the inner and outer diameters of the middle portion 41 are both less than those of the evaporating section 23. An inner diameter and an outer diameter of each end portion 42 increase along a direction away from the middle portion 41, until the inner diameter and the outer diameter of the end portion 42 are equal to those of the corresponding evaporating section 23 or condensing section 15, respectively. The wick structure 21 extends from the evaporating section 23 to the condensing section 24 along the inner surface of the tube 20, thereby forming a working medium channel. A length of the uncompressed cylindrical portion of the metal layer 30 in the evaporating section 23 is 10 mm.
The tube 20 has a working medium injected into it, and is evacuated of air and sealed. In particular, both the evaporating section 23 and the condensing section 24 are evacuated of air.
Referring to FIG. 6, two pairs of opposite through holes 25 are formed in each of the evaporating section 23 and the condensing section 24 of the tube 20.
Referring to FIG. 7, two hollow metal pipes 60 are provided to communicate the through holes 25 of the evaporating section 23 with those of the condensing section 24, so that two vapor channels 61 are defined by the hollow metal pipes 60. Thus, the heat pipe 1 is manufactured.
Referring to FIG. 8, a heat pipe in accordance with a second embodiment of the present invention is shown. There are four pairs of through holes 25 defined in the tube 20. Four hollow metal pipes 60 are provided to communicate the through holes 25 of the evaporating section 23 with those of the condensing section 24, so that four vapor channels 61 are defined by the hollow metal pipes 60. It is understood that the quantity of the through holes 25 and the hollow metal pipes 60 is not limited to eight through holes 25 and four hollow metal pipes 60.
Particular embodiments are shown and described by way of illustration and example only. The principles and the features of the present disclosure may be employed in various and numerous embodiments thereof without departing from the scope of the disclosure. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.

Claims

What is claimed is:

1. A heat pipe comprising

a hollow tube, two ends of the tube being sealed and the tube defining a chamber therein;

a wick structure provided on an inner surface of the tube; and

a working medium provided in the chamber;

wherein the tube comprises an evaporating section and a condensing section, the evaporating section is isolated from the condensing section, the wick structure extends from the evaporating section to the condensing section along the inner surface of the tube to form a working medium channel, a through hole is defined in each of the evaporating section and the condensing section of the tube, and a metal pipe communicates the through hole of the evaporating section with the through hole of the condensing section, respectively, to form a vapor channel.

2. The heat pipe of claim 1, further comprising a metal layer therein, wherein the evaporating section is isolated from the condensing section by the metal layer, the metal layer comprises a tapered portion and a cylindrical portion connected to a right end of the tapered portion, the tapered portion tapers from the evaporating section to the condensing section until the tapered portion terminates at a closed end thereof, and the tapered portion and the cylindrical portion are attached to the wick structure of the tube.

3. The heat pipe of claim 2, wherein the tube further comprises a reduced section between the evaporating section and the condensing section, the reduced section is located outside the metal layer, the evaporating section and the condensing section of the tube have a same inner diameter and a same outer diameter which constitute an inner diameter and an outer diameter of the tube, respectively, and an inner diameter and an outer diameter of the reduced section are less than the inner diameter and the outer diameter of the tube, respectively.

4. The heat pipe of claim 3, wherein the reduced section has a middle portion and two end portions located at two ends of the middle portion, an inner diameter and an outer diameter of the middle portion are constant, the inner diameter and the outer diameter of the middle portion are less than the inner diameter and the outer diameter of the tube, respectively, and an inner diameter and an outer diameter of each end portion increases along a direction away from the middle portion until the inner diameter and the outer diameter of the end portion are equal to the inner diameter and the outer diameter of the tube, respectively.

5. The heat pipe of claim 1, wherein a length of the evaporating section is less than that of the condensing section.

6. The heat pipe of claim 1, wherein the tube is made of thermally conductive material.

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

8. A method for manufacturing a heat pipe, the method comprising:

providing a tube with a wick structure on an inner surface thereof, the tube defining a chamber therein, and further defining an evaporating section and a condensing section;

insolating the evaporating section from the condensing section by blocking the chamber, the wick structure extending from the evaporating section to the condensing section along the inner surface of the tube to form a working medium channel;

evacuating the evaporating section and the condensing section, injecting a working medium into the tube, and sealing the tube;

defining at least one through hole in each of the evaporating section and the condensing section of the tube; and

arranging at least one metal pipe to communicate the at least one through hole of the evaporating section with the at least one through hole of the condensing section, thereby defining at least one vapor channel.

9. The method of claim 8, wherein insolating the evaporating section from the condensing section further comprises:

providing a metal layer in the tube between the evaporating section and the condensing section, the metal layer being attached to the wick structure of the tube;

pressing the tube at the metal layer to obtain a reduced section of the tube, an inner diameter and an outer diameter of the reduced section being less than an inner diameter and an outer diameter of the tube, respectively, one portion of the metal layer in the reduced section tapering in a direction from the evaporating section to the condensing section until terminating at a closed end of said one portion, another portion of the metal layer in the evaporating section remaining attached to the wick structure of the tube, the evaporating section thereby being insolated from the condensing section by the metal layer.

10. The method of claim 9, wherein the reduced section has a middle portion and two end portions located at two ends of the middle portion, an inner diameter and an outer diameter of the middle portion are constant and both less than that of the tube, and an inner diameter and an outer diameter of the end portion increase along a direction away from the middle portion until the inner diameter and the outer diameter of the end portion being equal to that of the tube.

11. The method of claim 8, wherein the tube is made of thermally conductive materials.

12. The method as claimed in claim 8, wherein the wick structure is selected from fine grooves, sintered powder, screen mesh, and bundles of fiber.

13. The method of claim 8, wherein a length of the evaporating section is less than that of the condensing section.

14. A heat pipe comprising

a wick structure provided on an inner surface of the tube; and

a working medium provided in the chamber;

wherein the tube comprises an evaporating section and a condensing section, the evaporating section is isolated from the condensing section, the wick structure extends from the evaporating section to the condensing section along the inner surface of the tube to form a working medium channel, two through holes are defined in each of the evaporating section and the condensing section of the tube, and two metal pipes communicate the two through holes of the evaporating section with the two through holes of the condensing section, respectively, to form two vapor channels.

15. The heat pipe of claim 14, further comprising a metal layer therein, wherein the evaporating section is isolated from the condensing section by the metal layer, the metal layer comprises a tapered portion and a cylindrical portion connected to a right end of the tapered portion, the tapered portion tapers from the evaporating section to the condensing section until closed, and the tapered portion and the cylindrical portion are attached to the wick structure of the tube.

16. The heat pipe of claim 15, wherein the tube further comprises a reduced section between the evaporating section and the condensing section, the reduced section is located outside the metal layer, and an inner diameter and an outer diameter of the reduced section are both less than that of the tube respectively.

17. The heat pipe of claim 16, wherein the reduced section has a middle portion and two end portions located at two ends of the middle portion, an inner diameter and an outer diameter of the middle portion are constant, and the inner diameter and outer diameter of the middle portion both less than that of the tube, and an inner diameter and an outer diameter of the end portion increase along a direction away from the middle portion, until the inner diameter and the outer diameter of the end portion being equal to that of the tube.

18. The heat pipe of claim 14, wherein a length of the evaporating section is less than that of the condensing section.

19. The heat pipe of claim 14, wherein the tube is made of thermally conductive materials.

20. The heat pipe of claim 14, wherein the wick structure is selected from fine grooves, sintered powder, screen mesh, and bundles of fiber.