US20060000581A1

US20060000581A1 - Cylindrical heat pipes

Info

Publication number: US20060000581A1
Application number: US10/974,841
Authority: US
Inventors: Yency Chen; Chi-Feng Lin; Chin-Ming Chen
Original assignee: Delta Electronics Inc
Current assignee: Delta Electronics Inc
Priority date: 2004-06-30
Filing date: 2004-10-28
Publication date: 2006-01-05
Also published as: TW200600741A; TWI256994B; JP2006017452A

Abstract

A cylindrical heat pipe. The heat pipe includes a hollow body, a cover, and a tube. The hollow body includes a sealed bottom, a top portion and an inner wall. The cover includes an elevated portion near the top portion. The tube penetrates the cover. The cover seals the hollow body and guides working fluid passing therethrough into the heat pipe. After working fluid is added and vacuums, the tube is sealed, thus the elevated portion enlarges heat-dissipation region of the heat pipe.

Description

BACKGROUND

The invention relates to heat pipes, and in particular to cylindrical heat pipes or heat columns.
In the continued development of electronic devices, the number of transistors per unit area in an electronic device has increased to improve performance. External fans and heat-dissipation devices are normally installed in electronic devices to dissipate excess heat and maintain an acceptable working temperature. Since heat dissipation of the electronic devices can increase effective chip speeds, fan speed is increased to accelerate heat conduction. Power consumption and noise level, however, both increase accordingly. Additionally, heat-dissipation device such as heat-dissipation fin, while improving heat conduction, reduce the available internal space. Thus, currently, a heat pipe with a small cross section and low temperature differential is often used to provide a relatively long distance for heat conduction without requiring an additional power supply. The smaller heat pipe occupies little internal space, and thus, is widely used in electronic devices.
A heat pipe comprises a hollow body with two sealed ends, a wick structure, and working fluid. The heat pipe is a vacuumed vessel charged with a working fluid. The walls of the heat pipe are lined with the wick structure that allows working fluid to travel from one end of the heat pipe to the other via capillary action. The conventional heat pipe is manufactured by sealing an end of the pipe, forming the wick structure, adding working fluid, and vacuuming. Alternatively, the pipe can be vacuumed before adding working fluid. Finally, the other end of the pipe is sealed. In a cylindrical heat pipe comprising a cover and an additional hollow body in the center thereof, the cover seals the pipe opening after adding working fluid and vacuums through the hollow body.
FIG. 1A is a schematic view showing a conventional heat pipe with an open end. FIG. 1B is a cross section of the cylindrical heat pipe of FIG. 1A. The cylindrical heat pipe 1 with an open end comprises a hollow body 10. An interior wall 14 of the hollow body 10 has a gradient, shown in FIG. 1B for use in a subsequent process. After formation of the wick structure, a cover 11 is disposed in the hollow body 10 to form a closed space. The gradient on the interior wall 14 allows the cover 11 to be positioned thereon. The cover 11 comprises a small hollow tube 12 passing through the center thereof. The hollow body 10 can be filled with a working fluid through the hollow tube 12, which is the only injection inlet of the heat pipe 1. After vacuuming and adding working fluid, the hollow tube 12 is sealed. A sealant fills a space 15 between the open end 13 and the cover 11 to ensure the pipe is adequately sealed. Thus, production of a cylindrical heat pipe 1 is completed.
Since the distance between the open end 13 and the cover 11 is long, however, heat-dissipation space of the heat pipe is reduced, thereby reducing heat conductivity and heat-dissipation efficiency. Moreover, due to the combination of the hollow tube 12 and the cover 11, the hollow tube 12 must be sealed after working fluid is added. Thus, the procedure becomes complicated and reduces reliability.

SUMMARY

Embodiments of the invention provide a cylindrical heat pipe. The cylindrical heat pipe comprises a hollow cylindrical body, a cover, and a hollow tube. The cylindrical body includes a sealed bottom, a top portion and an inner wall. The cover includes an elevated portion, and the hollow tube penetrates the cover. The cover seals the hollow cylindrical body and guides a working fluid passing therethrough into the heat pipe. The inner wall of the hollow cylindrical body comprises a stepped portion or at least one protrusion for fixing and supporting the cover. After the working fluid is added and the heat pipe is vacuumed, the hollow tube is sealed, and the elevated portion enlarges the heat-dissipation space of the cylindrical heat pipe.
Embodiments of the invention further provide another cylindrical heat pipe. The cylindrical heat pipe comprises a hollow cylindrical body and a cover. The cover comprises a center with an opening defined thereon. The cover seals the hollow cylindrical body and guides a working fluid passing therethrough into the heat pipe. The inner wall of the hollow cylindrical body comprises a stepped portion or at least one protrusion for fixing and supporting the cover. After the working fluid is added through the opening of the cover, the heat pipe is vacuumed, and the opening is sealed by a block.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein:
FIG. 1A is a schematic view of a conventional heat pipe with an open end;
FIG. 1B is a cross-sectional view of the cylindrical heat pipe of FIG. 1A;
FIG. 2A is a schematic view of a cover according to a first embodiment of the invention;
FIG. 2B is a cross-sectional view of a cylindrical heat pipe with the cover of FIG. 2A;
FIG. 3A is a cylindrical heat pipe of a second embodiment of the invention;
FIG. 3B is a cross-sectional view of the cylindrical heat pipe of FIG. 3A;
FIG. 4A is a schematic view of a cylindrical heat pipe of a third embodiment when an end thereof is not sealed;
FIG. 4B is a cross section of the cylindrical heat pipe of FIG. 4A;
FIG. 4C is a top view of the cylindrical heat pipe of FIG. 4A;
FIG. 4D is a cross-sectional view of a cylindrical heat pipe with the cover of FIG. 2B; and
FIG. 4E is a cross-sectional view of a cylindrical heat pipe with the cover of FIG. 3B.

DETAILED DESCRIPTION

First Embodiment

FIG. 2A is a schematic view of a cover according to a first embodiment of the invention. The cover 21 comprises an elevated portion 26, and a hollow tube 22 penetrates at the center of the cover 21 as the only injection inlet when the hollow tube 22 guides a working fluid therethrough into the cylindrical heat pipe in a sequential procedure. Referring to FIG. 2B, it is a cross-sectional view of a cylindrical heat pipe with the cover of FIG. 2A. The cylindrical heat pipe 2 comprises a hollow body 20. The hollow body 20 comprises a sealed bottom, a top portion 23, and an inner wall 24. The inner wall comprises a stepped portion for fixing and supporting the cover 21.
After a wick structure is formed on the inner wall 24 of the hollow body 20, the cover 21 is disposed in the hollow body 20 for sealing the pipe. Then a working fluid is added into the hollow body 20 of the cylindrical heat pipe 2 through the hollow tube 22. After the hollow body 20 is vacuumed, the hollow tube 22 is sealed. Thus, process of manufacturing the cylindrical heat pipe 2 is completed. Further, a sealant (or vacuum gel) is filled in a space 25 between the cover 21 and the top portion 23, for ensuring adequately sealing the pipe. The sealant comprises epoxy or thermosetting gel.
Comparing to the conventional heat pipe, a periphery of the cover 21 is raised by the elevated portion 26 from position S1 of the conventional heat pipe to a higher position S2. Thus, the space close to the periphery of the cover 21 is enlarged owing to the elevated portion 26. As a result, the heat-dissipation space is increased and heat conductivity of the cylindrical heat pipe 2 is improved.

Second Embodiment

FIG. 3A is a cylindrical heat pipe 3 of a second embodiment of the invention. FIG. 3B is a cross-sectional view of the cylindrical heat pipe 3 of FIG. 3A. The cylindrical heat pipe 3 comprises a hollow body 30 having a sealed bottom, a top portion 33, and an inner wall 34. The inner wall 34 comprises a stepped portion for fixing and supporting the cover 31.
After a wick structure is formed on the inner wall 34 of the hollow body 30, the cover 31 is disposed in the hollow body 30 for sealing the pipe. The center of the cover 31 has an opening 37 defined thereon, and a Working fluid is added into the hollow body 30 of the cylindrical heat pipe 3 through the opening 37. After the hollow body 30 is vacuumed, the opening 37 is sealed. Thus, process of manufacturing the cylindrical heat pipe 3 is completed. Further, a sealant is filled in a space 35 between the cover 31 and the top portion 33, for ensuring adequately sealing the pipe. The sealant comprises epoxy or thermosetting gel.
The method of sealing the opening 37 is not limited in the invention. For example, the opening 37 can be sealed by a block 38 with a radius slightly larger than the opening 37. The block 38 is pressed and deformed by stress to completely seal the opening 37. The block 38 can be a copper ball, or the block 38 can comprise other materials or have different shapes as long as the opening 37 of the cover 31 can be sealed. Moreover, the opening 37 may be sealed with a copper ball by welding, soldering, brazing, or gluing.
In this embodiment, because adding a working fluid or vacuuming is performed through the opening instead of using a conventional hollow tube, and the pipe is then sealed. Thus, the bottom level of the cover 31 can be raised from the conventional position S1 to a higher position S2. As a result, the heat-dissipation space is increased and heat conductivity of the cylindrical heat pipe 3 is improved.

Third Embodiment

FIG. 4A is a schematic view of a cylindrical heat pipe of a third embodiment when an end thereof is not sealed. FIG. 4B is a cross-sectional view of the cylindrical heat pipe of FIG. 4A. FIG. 4C is a top view of a cylindrical heat pipe of FIG. 4A. Referring to FIG. 4A to FIG. 4C, the cylindrical heat pipe 4 comprises a hollow body 40 having a sealed bottom, a top portion 43, and an inner wall 44.
The inner wall 44 of the hollow body 40 having a stepped portion is formed by a lathe. The inner wall 44 is partially cut, forming the stepped portion, such that the cover can be fixed and supported by the stepped portion. Alternatively, several protrusions 48 or a circular flange can be directly formed on the inner wall 44 of the hollow body 40 by a mold at a predetermined location. As shown in FIGS. 4B and 4C, four protrusions 48 are preferably formed at the location S2 by a jig or molding such that the protrusions 48 can serve as fixing points for supporting the cover. The width and thickness of the flange or quantity and shape of the protrusions are not limited in the invention as long as support for the cover is provided.
In the subsequent processes, several different covers and various sealing method are applied to the hollow body 40 with protrusions 48 thereon. For example, as shown in FIG. 4D, a cover 41 is disposed in the hollow body 40. The cover 41 is similar to the cover 21 of FIG. 2B in the first embodiment. Also, the sealing method is similar to that of the first embodiment. A working fluid is added through the hollow tube 42 into the internal space of the hollow body 40 of the cylindrical heat pipe 4. After vacuuming, the hollow tube 42 is sealed. Thus, process of manufacturing the cylindrical heat pipe 4 is completed. Further, a sealant is filled in a space 45 between the cover 41 and the top portion 43, for ensuring adequately sealing the pipe. The sealant comprises epoxy or thermosetting gel.
Comparing to the conventional heat pipe, a periphery of the cover 41 is raised by the elevated portion 46 from the conventional position S1 to a higher position S2. Thus, the space close to the periphery of the cover 41 is enlarged owing to the elevated portion 46. As a result, the heat-dissipation space is increased and heat conductivity of the cylindrical heat pipe 4 is improved.
Furthermore, FIG. 4E is a cross-sectional view of a cylindrical heat pipe 4 with the cover of FIG. 3B. As shown in FIG. 4E, the cover 51 is the same as that in FIG. 3B of the second embodiment. The center of the cover 51 has an opening 57 defined therein, so that a working fluid can be added through the opening 57 into the hollow body 40 of the cylindrical heat pipe 4. The opening 57 is sealed after the hollow body 40 is vacuumed, thereby completing the formation of the cylindrical heat pipe 4. Further, a sealant is filled in a space 55 between the cover 51 and the top portion 43, for ensuring sealing adequately sealing the pipe. The sealant comprises epoxy or thermosetting gel.
The method of sealing the opening 57 is not limited in the present invention. For example, the opening 57 can be sealed by a block 58 with a radius slightly larger than the opening 57. The block 58 is pressed and deformed by stress to completely seal the opening 57. The block 58 can be a copper ball, or the block 38 can comprise other materials or have different shapes as long as the opening 57 of the cover 51 can be sealed. Moreover, the opening 57 may be sealed with a copper ball by welding, soldering, brazing, or gluing.
In this embodiment, because adding a working fluid or vacuuming is performed through the opening 57 instead of using a conventional hollow tube, and the pipe is then sealed. Thus, the bottom level of the cover 31 can be raised from the conventional position S1 to a higher position S2. As a result, the heat-dissipation space is increased and heat conductivity of the cylindrical heat pipe 3 is improved.
In the above-disclosed embodiments, the wick structure can comprise mesh, fiber, sinter, or grooved wick, formed by sintering, gluing, filling, or deposition. The working fluid can comprise inorganic compounds, water, alcohol, liquid metal such as mercury, ketone, refrigerant such as HFC-134a, or other organic compounds. Typically, the most frequently used working fluid is water. The surface tension between corresponding working fluids differs with wick structures. The sequence of adding the working fluid and vacuuming can be interchanged, followed by sealing the opening. The cylindrical heat pipe of embodiments of the invention can be applied in any heat-dissipation module of any electronic device and can be shaped to meet requirements of the heat-dissipation module.
In conclusion, the disclosed cylindrical heat pipe of the invention comprises a cover with an elevated portion, wherein a working fluid can be added not only through a hollow tube, but also through an opening in the cover such that the bottom level of the cover can be elevated. Moreover, the inner wall of the hollow body has a stepped portion or at least one protrusion for fixing and supporting the cover. Embodiments of the invention maintain or increase the space of the heat-dissipation region by forsaking conventional using a hollow tube to add a working fluid and vacuum. Thus, the heat-dissipation region of the cylindrical heat pipe according to embodiments of the invention can be enlarged, thereby increasing heat conductivity.
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 heat pipe, comprising:

a hollow body, comprising a sealed bottom, a top portion and an inner wall, wherein the inner wall connects the sealed bottom and the top portion;

a cover comprising an elevated portion near the top portion; and

a tube, penetrating the cover;

wherein the cover seals the hollow body, after a working fluid is added through the tube, the tube is sealed, and the elevated portion enlarges the heat-dissipation region of the heat pipe.

2. The heat pipe as claimed in claim 1, wherein the inner wall comprises a stepped portion for fixing and supporting the cover.

3. The heat pipe as claimed in claim 1, wherein the inner wall comprises at least one protrusion for fixing and supporting the cover.

4. The heat pipe as claimed in claim 1, wherein the inner wall comprises a flange for fixing and supporting the cover.

5. The heat pipe as claimed in claim 1, further comprising a sealant, disposed between the cover and the top portion.

6. The heat pipe as claimed in claim 1, wherein the cover and the hollow body comprise the same material.

7. The heat pipe as claimed in claim 6, wherein the cover and the hollow body comprise plastic, metal, alloy, non-metal or a combination thereof.

8. The heat pipe as claimed in claim 1, wherein the bottom and the hollow body are integrally formed.

9. The heat pipe as claimed in claim 8, wherein the bottom and the hollow body are formed by forging.

10. A heat pipe, comprising:

a hollow body, comprising a sealed bottom, a top portion and an inner wall, wherein the inner wall connects the sealed bottom and the top portion; and

a cover, disposed near the top portion and comprising a center with an opening defined therein;

wherein the cover seals the hollow body, after a working fluid is added through the opening of the cover, and the opening is sealed.

11. The heat pipe as claimed in claim 10, wherein the inner wall comprises a stepped portion for fixing and supporting the cover.

12. The heat pipe as claimed in claim 10, wherein the inner wall comprises at least one protrusion for fixing and supporting the cover.

13. The heat pipe as claimed in claim 10, wherein the inner wall comprises a flange for fixing and supporting the cover.

14. The heat pipe as claimed in claim 10, wherein the opening is sealed by a block.

15. The heat pipe as claimed in claim 10, wherein the opening is sealed by welding, soldering, or brazing.

16. The heat pipe as claimed in claim 10, wherein the opening is sealed by an adhesive.

17. The heat pipe as claimed in claim 10, further comprising a sealant, disposed between the cover and the top portion.

18. The heat pipe as claimed in claim 10, wherein the cover and the hollow body comprise the same material, and the material comprises plastic, metal, alloy, non-alloy or a combination thereof.

19. The heat pipe as claimed in claim 10, wherein the bottom and the hollow body are integrally formed.

20. The heat pipe as claimed in claim 19, wherein the bottom and the hollow body are formed by forging.