US20110094712A1

US20110094712A1 - Plate-type heat pipe

Info

Publication number: US20110094712A1
Application number: US12/690,933
Authority: US
Inventors: Chuen-Shu Hou
Original assignee: Foxconn Technology Co Ltd
Current assignee: Foxconn Technology Co Ltd
Priority date: 2009-10-22
Filing date: 2010-01-21
Publication date: 2011-04-28
Also published as: CN102042778A; CN102042778B

Abstract

An exemplary plate-type heat pipe includes a condensing plate, an evaporating plate and a first wick portion. The evaporating plate cooperates with the condensing plate to define a hermetic container. Working fluid is contained in the container. The first wick portion is formed on an inner surface of the evaporating plate. The first wick portion defines through holes therein.

Description

BACKGROUND

1. Technical Field
The present disclosure relates to heat pipes and, more particularly, to a plate-type heat pipe having good heat dissipation efficiency and stable and reliable performance.
2. Description of Related Art
Generally, plate-type heat pipes efficiently dissipate heat from heat-generating components such as a central processing unit (CPU) of a computer. A conventional plate-type heat pipe comprises a top plate and a bottom cover hermetically contacting the top plate to form a container. A wick structure is adhered to an inner surface of the bottom cover. Working fluid is contained in the container. All parts of the wick structure have the same thickness. When the bottom cover of the plate-type heat pipe absorbs heat of the heat-generating component, the working fluid is vaporized to absorb heat of the bottom cover.
If the wick structure is too thick, a part of the vaporized working fluid is retarded by the wick structure when the vaporized working fluid is escaping from the wick structure toward the top plate. In addition, if the pores of the wick structure are too small, the vaporized working fluid also tends to be retarded by the wick structure. In these kinds of situations, a plurality of bubbles is formed in and on the wick structure. The bubbles tend to block the pores of the wick structure, and retard the flow of condensed working fluid into the wick structure. When this happens, the amount of condensed working fluid contained in the wick structure decreases. What working fluid there is in the wick structure may absorb the heat of the bottom cover too slowly, whereby heat is accumulated on the bottom cover. In due course, the plate-type heat pipe may overheat, and the heat dissipation efficiency of the plate-type heat pipe is reduced.
What is needed, therefore, is a plate-type heat pipe having good heat dissipation efficiency and stable, reliable performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a plate-type heat pipe in accordance with a first embodiment of the present disclosure, the plate-type heat pipe including an evaporating plate having a heat absorbing portion, a first wick member, and a second wick member having a first wick portion.

FIG. 2 is an isometric view of part of the heat absorbing portion of FIG. 1, showing the first wick portion mounted on the heat absorbing portion.

FIG. 3 is an enlarged, cross-sectional view of part of the heat absorbing portion with the first wick portion, taken along line III-III of FIG. 2.

FIG. 4 is similar to FIG. 3, but showing part of a heat absorbing portion of an evaporating plate arrangement of a plate-type heat pipe in accordance with a second embodiment of the present disclosure, with a first wick portion and a number of auxiliary wick portions mounted on the heat absorbing portion.

FIG. 5 is similar to FIG. 3, but showing part of a heat absorbing portion of an evaporating plate arrangement of a plate-type heat pipe in accordance with a third embodiment of the present disclosure, with a first wick portion and a number of auxiliary wick portions mounted on the heat absorbing portion.

FIG. 6 is similar to FIG. 3, but showing part of a heat absorbing portion of an evaporating plate arrangement of a plate-type heat pipe in accordance with a fourth embodiment of the present disclosure, with a first wick portion and a number of auxiliary wick portions mounted on the heat absorbing portion.

DETAILED DESCRIPTION

Referring to FIGS. 1-2, a plate-type heat pipe in accordance with a first embodiment of the present disclosure is shown. The plate-type heat pipe includes a hermetic container 10, a continuous wick structure 30 mounted on an inner surface of the container 10, and working fluid (not shown) contained in the container 10.
The container 10 is made of copper, aluminum, or an alloy thereof, and includes an elongated condensing plate 11 and a bowl-shaped evaporating plate 13 hermetically contacting the condensing plate 11. The evaporating plate 13 absorbs heat generated by one or more components (not shown) such as electronic devices. The condensing plate 11 dissipates heat, transferred from the evaporating plate 13, to the ambient environment.
The evaporating plate 13 includes an elongated heat absorbing portion 131, two transition portions 133, two extending portions 134 and two sidewalls 135. The transition portions 133 extend upwardly and outwardly from opposite lateral edges of the heat absorbing portion 131, respectively, and are symmetrically opposite each other. The extending portions 134 extend outwardly along opposite horizontal directions from outer edges of the transition portions 133, respectively. The sidewalls 135 extend upwardly from outer edges of the extending portions 133, respectively. The sidewalls 135 are perpendicular to the extending portions 133. In the illustrated embodiment, top ends of the sidewalls 135 are integrally formed with two ends of the condensing plate 11. That is, the evaporating plate 13 and the condensing plate 11 are a single body of the same material without any seams. In other embodiments, the evaporating plate 13 and the condensing plate 11 can be two separate bodies connected together.
The wick structure 30 is made of sintered metallic powder, and includes an elongated first wick member 31 and a second wick member 33. A plurality of capillary pores (not labeled) are defined in the first wick member 31 and the second wick member 33 for providing a capillary force to draw condensed working fluid back toward a middle portion of the second wick member 33 (see also below). The first wick member 31 is adhered to an inner surface of the condensing plate 11. The second wick member 33 is adhered to an inner surface of the evaporating plate 13. Opposite ends of the second wick structure 33 interconnect opposite ends of the first wick member 31, respectively, thereby forming the continuous wick structure 30.
Referring also to FIG. 3, the second wick structure 33 includes an elongated first wick portion 331, two second wick portions 333, two third wick portions 335 and two fourth wick portions 337. The first wick portion 331, the second wick portions 333, and the third wick portions 335 are spaced from the first wick member 31.
The first wick portion 331 is adhered to an inner surface of the heat absorbing portion 131 of the evaporating plate 13. The first wick portion 331 defines a plurality of rectangular or square through holes 3313 therein. In the illustrated embodiment, the through holes 3313 are arranged in a regular m x n array. Because the through holes 3313 are defined in the first wick portion 331, a portion of the working fluid is contained in the through holes 3313 and contacts the heat absorbing portion 131 of the evaporating plate 13 directly. The working fluid contained in the through holes 3313 and contained in the first wick portion 331 absorbs the heat of the heat absorbing portion 131 quickly and then is vaporized. The vaporized working fluid in the through holes 3313 escapes the first wick portion 331 from the through holes 3313 directly. Therefore the working fluid in the first wick portion 331 escapes from the first wick portion 331 via the through holes 3313 quickly. Accordingly, unlike in other conventional plate-type heat pipes, few or even no bubbles accumulate in the first wick portion 331 when the plate-type heat pipe is in operation. Thus, the heat dissipation efficiency of the plate-type heat pipe is improved. In alternative embodiments, the through holes 3313 can be triangular, circular, oval-shaped, elliptical, etc, and can be larger than the pores of the first wick member 31 and the second wick member 33.
The second wick portions 333 extend upwardly and outwardly from opposite ends of the first wick portion 331, respectively, and are symmetrically opposite each other. The second wick portions 333 are adhered to inner surfaces of the transition portions 133 of the evaporating plate 13. The third wick portions 335 are horizontal, and extend outwardly from the second wick portions 333, respectively. The third wick portions 335 are adhered to inner surfaces of the extending portions 134 of the evaporating plate 13. Each fourth wick portion 337 is adhered to an inner surface of the corresponding sidewall 135 of the evaporating plate 13, and fills a corner formed by the sidewall 135 and the corresponding extending portion 134. A cross-section of each fourth wick portion 337 is substantially triangular. That is, a transverse thickness (horizontal, from left to right, as viewed in FIG. 1) of the fourth wick portion 337 progressively decreases from a bottom end of the fourth wick portion 337 to a top end of the fourth wick portion 337. The fourth wick portions 337 connect the opposite ends of the first wick member 31, respectively. The second wick portions 333, third wick portions 335, and fourth wick portions 337 cooperatively guide the condensing working fluid contained in or accumulated on the first wick member 31 back to the first wick portion 331 to ensure that a quantity of the condensing working fluid in the first wick portion 331 is sufficiently large at all times.
Referring to FIG. 4, this shows part of a heat absorbing portion arrangement of a plate-type heat pipe in accordance with a second embodiment of the present disclosure. A first wick portion 331 and a plurality of auxiliary wick portions 332 are adhered to an inner surface of a heat absorbing portion 131. In the illustrated embodiment, the auxiliary wick portions 332 fill bottom ends of the through holes 3313, respectively. Bottom end surfaces of the auxiliary wick portions 332 and a bottom surface of the first wick portion 331 are coplanar with one another, and contact the inner surface of the heat absorbing portion 131. Each of the auxiliary wick portions 332 has a same thickness and is much thinner than the first wick portion 331. For example, each auxiliary wick portion 332 is less than half the thickness of the first wick portion 331.
Because the auxiliary wick portions 332 are thinner than the first wick portion 331, heat transfer paths of the working fluid in the heat absorbing portion 131 are generally shorter than those of conventional plate-type heat pipes. Accordingly, the working fluid is vaporized quickly. Thus, the heat dissipation efficiency of the plate-type heat pipe is improved. In addition, a capillary suction of the second wick member 33 is improved because of the auxiliary wick portions 332 filling bottoms of the through holes 3313 of the first wick portion 331. Therefore, the condensed working fluid flows back to the first wick portion 331 more quickly. Thus, stable and reliable performance of the plate-type heat pipe can be ensured.
Referring to FIG. 5, this shows part of a heat absorbing portion arrangement of a plate-type heat pipe in accordance with a third embodiment of the present disclosure. A first wick portion 331 and a number of auxiliary wick portions 334 are adhered to an inner surface of a heat absorbing portion 131. A cross-section of each of the auxiliary wick portions 334 is a trapezoid. Each auxiliary wick portion 334 has a smaller end, and a larger end opposite to the smaller end. The smaller ends of the auxiliary wick portions 334 are all oriented toward the same direction. In this embodiment, a top side of each auxiliary wick portion 334 is aslant, and a bottom side of each auxiliary wick portion 334 is horizontal and adhered to the inner surface of the heat absorbing portion 131. The larger ends of the auxiliary wick portions 334 are all thinner than the first wick portion 331.
Referring to FIG. 6, this shows part of a heat absorbing portion arrangement of a plate-type heat pipe in accordance with a fourth embodiment of the present disclosure. A first wick portion 331 and a plurality of auxiliary wick portions 336 are adhered to an inner surface of a heat absorbing portion 131. A cross-section of each of the auxiliary wick portions 336 has a top side being concave, and a bottom side being horizontal and adhered to the inner surface of the heat absorbing portion 131. That is, a thickness of each auxiliary wick portion 336 gradually increases from a central portion thereof to each of opposite ends thereof. The opposite ends of the auxiliary wick portions 336 are all thinner than the first wick portion 331.
It is to be understood, however, that even though numerous characteristics and advantages of various embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, 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 disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. A plate-type heat pipe comprising:

a condensing plate;

an evaporating plate cooperating with the condensing plate to define a hermetic container;

working fluid contained in the container; and

a first wick portion formed on an inner surface of the evaporating plate, the first wick portion defining a plurality of through holes therein.

2. The plate-type heat pipe of claim 1, wherein the first wick portion is made of sintered metallic powder.

3. The plate-type heat pipe of claim 1, wherein a plurality of auxiliary wick portions are received in the through holes, respectively, and contact the inner surface of the evaporating plate.

4. The plate-type heat pipe of claim 3, wherein each of the auxiliary wick portions is thinner than the first wick portion, each auxiliary wick portion comprising a first side contacting the inner surface of the evaporating plate and an opposite second side.

5. The plate-type heat pipe of claim 4, wherein a cross-section of each of the auxiliary wick portions is a rectangle, the second side being parallel to the first side.

6. The plate-type heat pipe of claim 4, wherein a cross-section of each of the auxiliary wick portions is a trapezoid, the second side being aslant relative to the first side.

7. The plate-type heat pipe of claim 6, wherein the auxiliary wick portions are all oriented toward the same direction.

8. The plate-type heat pipe of claim 4, wherein the second side of each of the auxiliary wick portions is concave, and a thickness of each of the auxiliary wick portions gradually increases from a central portion thereof to each of opposite ends thereof.

9. The plate-type heat pipe of claim 4, wherein the evaporating plate comprises a central heat absorbing portion and two sidewalls extending upwardly at opposite sides of the heat absorbing portion and connecting with the condensing plate, and the first wick portion is adhered on an inner surface of the heat absorbing portion.

10. The plate-type heat pipe of claim 9, further comprising two second wick portions adhered on inner surfaces of the sidewalls, respectively.

11. The plate-type heat pipe of claim 10, wherein the evaporating plate further comprises two transition portions extend outwardly and upwardly from opposite ends of the heat absorbing portion, and two third wick portions are adhered on inner surfaces of the transition portions.

12. The plate-type heat pipe of claim 11, wherein the evaporating plate further comprises two extending portions extending outwardly from opposite ends of the transition portions, respectively, and connecting with the two sidewalls, respectively, and two fourth wick portions are adhered on inner surfaces of the extending portions.

13. The plate-type heat pipe of claim 10, wherein each of the second wick portions fills a corner formed by the corresponding sidewall and the corresponding extending portion, and a cross-section of each of the second wick portions is generally triangular.

14. The plate-type heat pipe of claim 11, wherein a first wick member is adhered on an inner surface of the condensing plate and connects with the second wick portions.

15. A plate-type heat pipe comprising:

a hermetic container comprising an evaporating plate and a condensing plate facing each other;

working fluid contained in the container; and

a wick portion formed on an inner surface of the evaporating plate, the wick portion defining a plurality of capillary pores and a plurality of through holes therein.

16. The plate-type heat pipe of claim 15, wherein an auxiliary wick is arranged in each of the through holes of the wick portion and contacts the inner surface of the evaporating plate.

17. The plate-type heat pipe of claim 16, wherein each of the auxiliary wicks is thinner than the wick portion, and comprises a first side contacting the inner surface of the evaporating plate and an opposite second side.

18. The plate-type heat pipe of claim 17, wherein the second side of each of the auxiliary wicks is aslant relative to the first side.

19. The plate-type heat pipe of claim 17, wherein the second side of each of the auxiliary wicks is concave, and a thickness of each of the auxiliary wicks gradually increases from a central portion thereof to each of opposite ends thereof.

20. The plate-type heat pipe of claim 15, wherein the evaporating plate comprises a heat absorbing portion and two transition portions extending outwardly and upwardly from opposite ends of the heat absorbing portion, the wick portion being arranged on the heat absorbing portion.