US20060108103A1

US20060108103A1 - Heat pipe and wick structure thereof

Info

Publication number: US20060108103A1
Application number: US11/247,181
Authority: US
Inventors: Min-Hui Yu; Chi-Feng Lin; Chin-Ming Chen
Original assignee: Delta Electronics Inc
Current assignee: Delta Electronics Inc
Priority date: 2004-11-19
Filing date: 2005-10-12
Publication date: 2006-05-25
Also published as: TW200617339A; JP2006145196A

Abstract

A heat pipe includes a main body, a wick structure, and a working fluid. The wick structure is formed on an inner wall of the main body and the working fluid is filled in the main body. The coil-shaped wire is attached to the inner wall of the main body so as to form a plurality of grooves. The coil-shaped wire is obtained by winding a copper wire around a supporting frame which has a predetermined shape corresponding to the main body. The supporting frame can be exactly accommodated within the heat pipe.

Description

This Non-provisional application claims priority under U.S.C. § 119(a) on Patent Application No(s). 093135591 filed in Taiwan, Republic of China on Nov. 19, 2004, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The invention relates to a heat pipe, and in particular to a heat pipe with an enhanced wick structure.
In electronic devices, with increased number of transistors per unit area, heat is increased. Moreover, as operating frequency of the electronic devices increase, heat generated by on/off operation of the transistors is also increased. To prevent deterioration of operating performance of the electronic devices and prolong the lifespan of the electronic devices, heat generated by the transistors must be effectively removed.
A heat pipe can transfer heat over a long distance within a small cross section and under minor temperature differences. The heat pipe can be operated in the absence of power and is thus widely used to remove heat generated by an electronic device. Conventionally, a heat pipe has a hollow and sealed main body, a wick structure, and a working fluid. The working fluid absorbs heat and vaporizes in a vaporization section. The working fluid then flows to a condensing section to release the heat and is condensed to liquid. The liquid working fluid returns to the vaporization section by capillary attraction provided by the wick structure. By the working fluid circulating in the heat pipe with the aforementioned process, heat generated from the electronic device can thus be continuously transferred away from the electronic device. Therefore, the wick structure plays an important role in the performance of the heat pipe. Conventionally, the wick structure is divided into a meshed wick structure, sintered wick structure, and grooved wick structure.
FIG. 1A is a schematic cross section of a conventional meshed wick structure. The meshed wick structure is attached to an inner wall 11 a of a heat pipe. A working fluid 14 filled in the heat pipe condenses in a condensing section and returns to a vaporization section by the capillary attraction of the meshed wick structure composed of meshes 12. However, compared to other different wick structures, the meshed wick structure provides only normal capillary attraction but poor heat transfer capability and water permeability. Also, since attachment of the meshed wick structure at bent portions of the heat pipe is poor, the meshed wick structure is limited to be applied to a circular heat pipe. Namely, the meshed wick structure cannot be applied to heat pipes of various shapes, such as flat heat pipe, columned heat pipe, and so on.
FIG. 1B is a schematic cross section of a conventional grooved wick structure. Multiple grooves 16 are directly formed on an inner wall 11 b of a heat pipe, thereby forming the grooved wick structure. The working fluid 14 filled in the heat pipe condenses in a condensing section and returns to a vaporization section via the grooved wick structure composed of the grooves 16. Compared to other different wick structures, the grooved wick structure provides better heat transfer capability and water permeability. Nevertheless, manufacture of the grooved wick structure requires advanced techniques, thereby increasing manufacturing costs. Also, due to limitations of manufacturing techniques, most of the grooves are only arranged axially in a grooved wick structure. Namely, radial grooves are difficult to be obtained in the grooved wick structure.
FIG. 1C is a schematic cross section of a conventional sintered wick structure. A sintered wick structure 18 is formed on an inner wall 11 c of a heat pipe by sintering copper and other alloy powders. The working fluid 14 filled in the heat pipe condenses in a condensing section and returns to a vaporization section by the capillary attraction of the sintered wick structure. Compared to the meshed and grooved wick structures, the sintered wick structure provides higher capillary attraction, but poorer heat transfer capability and water permeability. Moreover, as the sintered wick structure is subjected to high-temperature sintering, the main body of the heat pipe is easily softened, which complicates manufacture of the sintered wick structure and increases manufacturing costs thereof.
Accordingly, all the conventional wick structures have drawbacks and limitations in application. As assembly density of components in electronic devices increases, heat generated by the electronic devices also increases. Additionally, as size of the electronic devices is reduced, smaller heat pipes with enhanced capability of heat transfer are thereby required.
Hence, there is a need to provide an improved heat pipe with a wick structure capable of being easily manufactured and can be widely applied to various heat pipes.

SUMMARY

Accordingly, an embodiment of the invention provides a wick structure for a heat pipe. The wick structure includes a coil-shaped wire on an inner wall of a main body of the heat pipe. The coil-shaped wire is attached to the inner wall so as to form a plurality of grooves. The coil-shaped wire is obtained by winding a copper wire around a supporting frame. The supporting frame has a predetermined shape corresponding to the main body of the heat pipe so that the supporting frame is exactly accommodated within the heat pipe. The cross section of the heat pipe is circular, elliptical, semicircular, rectangular, triangular, quadrilateral, trapezoid, pentagonal, hexagonal, octagonal, or polygonal shape. The coil-shaped wire includes metal, alloy, or nonmetallic materials. The coil-shaped wire preferably includes copper. The heat pipe is made of plastic, metal, alloy, or nonmetallic materials.
Another embodiment of the invention provides a heat pipe including a main body, a wick structure, and a working fluid. The wick structure is attached to the inner wall of the main body, and the working fluid is filled in the main body. The wick structure includes a coil-shaped wire attached to the inner wall of the main body so as to form a plurality of grooves. The coil-shaped wire is obtained by winding a copper wire around a supporting frame. The supporting frame has a predetermined shape corresponding to the main body of the heat pipe so that the supporting frame is exactly accommodated within the heat pipe. The cross section of the heat pipe is circular, elliptical, semicircular, rectangular, triangular, quadrilateral, trapezoid, pentagonal, hexagonal, octagonal, or polygonal shape. The coil-shaped wire includes metal, alloy, or nonmetallic materials. The coil-shaped wire preferably is copper. The heat pipe is made of plastic, metal, alloy, or nonmetallic materials. The working fluid is inorganic compounds, water, alcohols, liquid metal, ketones, refrigerant, or organic compounds.
Yet another embodiment of the invention provides a method of forming a wick structure in a heat pipe. The method includes steps of providing a supporting frame, winding a copper wire around the supporting frame to form a coil-shaped wire, providing a main body including an inner wall, and attaching the coil-shaped wire onto the inner wall to form a plurality of grooves. The supporting frame has a predetermined shape corresponding to the main body of the heat pipe so that the supporting frame is exactly accommodated within the heat pipe. The cross section of the heat pipe is circular, elliptical, semicircular, rectangular, triangular, quadrilateral, trapezoid, pentagonal, hexagonal, octagonal, or polygonal shape. The coil-shaped wire is made of metal, alloy, or nonmetallic materials. The coil-shaped wire preferably is copper, and the heat pipe is plastic, metal, alloy, or nonmetallic materials.

DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
FIG. 1A is a schematic cross section of a conventional meshed wick structure;
FIG. 1B is a schematic cross section of a conventional grooved wick structure;
FIG. 1C is a schematic cross section of a conventional sintered wick structure;
FIG. 2A is a schematic exploded view of the heat pipe of an embodiment of the invention;
FIG. 2B is a schematic cross section of the wick structure of an embodiment of the invention;
FIGS. 3A, 3B, and 3C are schematic perspective views showing manufacture of the wick structure of FIG. 2A; and
FIG. 4 is a schematic perspective view of another wick structure.

DETAILED DESCRIPTION

FIG. 2A is a schematic exploded view of the heat pipe of an embodiment of the invention. The heat pipe 20 includes a main body 21, a wick structure 22, a working fluid (not shown), and a cover 23. The main body 21 includes an inner wall 21 a to which the wick structure 22 is attached. The working fluid is filled in the main body 21. The main body 21 is preferably a hollow tube having one open end and the other close end or is a hollow tube having two open ends. After the wick structure 22 is formed, the main body 21 is then filled with the working fluid and is evacuated, and the cover 23 seals the main body 21 so that the heat pipe 20 is completed as a closed system. Alternatively, one end of the main body 21 is sealed, and the wick structure 22 is formed on the inner wall 21 a of the main body 21. The main body 21 is then filled with the working fluid and sealed by the cover 23. After the main body 21 is evacuated, manufacture of the heat pipe 20 is completed.
The heat pipe 20 can be applied to a heat-generating electronic device alone or be used by combining with a heat sink for transferring heat from the heat-generating electronic device to other places. The heat-generating electronic device may be a CPU, a transistor, a server, an advanced graphic card, a hard disk drive, a power supply, a vehicle control system, a multimedia electronic mechanism, a radio base station, or an advanced video game machine. Moreover, in addition to the heat pipe 20 and heat sink, a fan can also be applied to the heat-generating electronic device to enhance heat dissipation effect or transfer efficiency.
FIG. 2B is a schematic cross section of the wick structure of an embodiment of the invention. Referring both to FIG. 2A and FIG. 2B, the wick structure 22 includes a coil-shaped wire 26 attached to the inner wall 21 a of the main body 21. Specifically, the coil-shaped wire 26 can be tightly attached to the inner wall 21 a or separated from the inner wall 21 a by keeping a minor distance such that a minor space is formed therebetween to accommodate parts of a working fluid 24. Several grooves are formed between every two adjacent copper wires and the inner wall 21 a, so that the working fluid 24 can flow back from a condensing section to a vaporization section of the heat pipe by capillary attraction provided by the grooves. As compared to the conventional wick structures, the wick structure 22 of this embodiment provides high heat transfer capability, high permeability and great capillary attraction.
FIGS. 3A, 3B, and 3C are schematic perspective views showing manufacture of the wick structure of FIG. 2A. The coil-shaped wire 26 is obtained by winding a wire 26 a made of copper around a supporting frame 28 which has a predetermined shape corresponding to the main body of the heat pipe using a winding machine. Specifically, one end of the wire 26 a is fixed in a predetermined starting position S of the supporting frame 28, as shown in FIG. 3A. The wire 26 a is then wound around the supporting frame 28 along a predetermined direction according to a virtual axle X, as shown in FIG. 3B. Every two adjacent wires 26 a can be separated by a predetermined distance so as to form a pitch of the grooves of the wick structure, and each two adjacent wires 26 a can be arranged in parallel or non-parallel in according to requirements of follow-up wick structure manufacturing procedure. A predetermined ending position E, with respect to the predetermined starting position S, is set on the supporting frame 28. After the wire 26 a is continuously wound on the supporting frame 28 from the predetermined starting position S to the predetermined ending position E, the wire 26 a is spread over the supporting frame 28 to form the coil-shaped wire 26. Thereof, when the wire 26 a reaches the point of E, formation of the coil-shaped wire 26 is completed, as shown in FIG. 3C.
The supporting frame 28 preferably includes multiple columns, such as several rectangular columns as shown in FIGS. 3A, 3B, and 3C, but the supporting frame 28 is not limited thereto. The supporting frame 28 can be designed according to a predetermined shape corresponding to the main body 21 of the heat pipe 20. Namely, the supporting frame 28 has a predetermined shape corresponding to the main body 21 of the main body 21 so that the supporting frame 28 is exactly accommodated within the main body 21. Specifically, the cross sections of the heat pipe 20 and supporting frame 28 can be circular, elliptical, semicircular, rectangular, triangular, quadrilateral, trapezoid, pentagonal, hexagonal, octagonal, or polygonal shape. Further, the heat pipe 20 is made of plastic, metal, alloy, or nonmetallic materials. The material of the coil-shaped wire 26 or the wire 26 a is not limited to copper, metal, alloy, or nonmetallic materials is also suitable.
Moreover, the coil-shaped wire 26 is not limited to being winding in only one single predetermined direction according to a virtual axle X, as shown in FIGS. 3A-3C. For example, as shown in FIG. 4, the coil-shaped wire 26 can be wound along multiple directions.
In addition to application in transformers, mature winding techniques can also be applied to manufacture of the heat pipe. As compared to the conventional sintered wick structure requiring complicated manufacturing processes of stuffing powders and sintering, the present wick structure with the coil-shaped wire can simply be manufactured by using mature winding techniques, thereby reducing manufacturing costs thereof.
Moreover, the pitch of the grooves of the wick structure can be adjusted by changing the diameter of the copper wire and adjusting the distance between adjacent wires during winding of the wire. As the result, the manufacture of the present wick structure is thus simplified. Also, the present wick structure can cooperate with the meshed, sintered, and grooved wick structures to be employed on various heat pipes.
In conclusion, the heat pipe of this embodiment has a novel wick structure with the coil-shaped wire. The manufacture of the wick structure of this embodiment is simplified, compared to that of conventional wick structures, and the wick structure of this embodiment provides high heat transfer capability, high permeability and greater capillary attraction.
While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.

Claims

1. A wick structure for a heat pipe, characterized in that the wick structure is formed by a coil-shaped wire and disposed on an inner wall of a main body of the heat pipe.

2. The wick structure as claimed in claim 1, wherein the coil-shaped wire is attached to the inner wall of the main body of the heat pipe.

3. The wick structure as claimed in claim 1, wherein the coil-shaped wire is attached to the inner wall of the main body of the heat pipe so as to form a plurality of grooves.

4. The wick structure as claimed in claim 1, wherein the coil-shaped wire is obtained by winding a wire around a supporting frame.

5. The wick structure as claimed in claim 4, wherein the supporting frame has a predetermined shape corresponding to the main body of the heat pipe, and the supporting frame is exactly accommodated within the heat pipe.

6. The wick structure as claimed in claim 1, wherein a cross section of the heat pipe is circular, elliptical, semicircular, rectangular, triangular, quadrilateral, trapezoid, pentagonal, hexagonal, octagonal, or polygonal shape.

7. The wick structure as claimed in claim 1, wherein the coil-shaped wire comprises metal, alloy, or nonmetallic materials.

8. A heat pipe, comprising:

a main body comprising an inner wall;

a wick structure disposed on the inner wall; and

a working fluid filled in the main body, wherein the wick structure is formed by a coil-shaped wire on the inner wall of the main body of the heat pipe.

9. The heat pipe as claimed in claim 8, wherein the coil-shaped wire is attached to the inner wall of the main body of the heat pipe.

10. The heat pipe as claimed in claim 8, wherein the coil-shaped wire is attached to the inner wall of the main body of the heat pipe so as to form a plurality of grooves.

11. The heat pipe as claimed in claim 8, wherein the coil-shaped wire is obtained by winding a wire around a supporting frame.

12. The heat pipe as claimed in claim 11, wherein the supporting frame has a predetermined shape corresponding to the main body of the heat pipe, and the supporting frame is exactly accommodated within the heat pipe.

13. The heat pipe as claimed in claim 8, wherein a cross section of the heat pipe is circular, elliptical, semicircular, rectangular, triangular, quadrilateral, trapezoid, pentagonal, hexagonal, octagonal, or polygonal shape.

14. The heat pipe as claimed in claim 8, wherein the coil-shaped wire comprises metal, alloy, or nonmetallic materials.

15. The heat pipe as claimed in claim 8, wherein the heat pipe comprises plastic, metal, alloy, or nonmetallic materials.

16. The heat pipe as claimed in claim 8, wherein the working fluid comprises inorganic compounds, water, alcohols, liquid metal, ketones, refrigerant, or organic compounds.

17. A method of forming a wick structure in a heat pipe, comprising:

providing a supporting frame;

winding a wire around the supporting frame to obtain a coil-shaped wire;

providing a main body comprising an inner wall; and

attaching the coil-shaped wire on the inner wall so as to form a plurality of grooves.

18. The method as claimed in claim 17, wherein the supporting frame has a predetermined shape corresponding to the main body of the heat pipe, and the supporting frame is exactly accommodated within the heat pipe.

19. The method as claimed in claim 17, wherein a cross section of the heat pipe is circular, elliptical, semicircular, rectangular, triangular, quadrilateral, trapezoid, pentagonal, hexagonal, octagonal, or polygonal shape.

20. The method as claimed in claim 17, wherein the coil-shaped wire comprises metal, alloy, or nonmetallic materials.