US20070056712A1

US20070056712A1 - Heat dissipation module and heat pipe thereof

Info

Publication number: US20070056712A1
Application number: US11/491,896
Authority: US
Inventors: Min-Hui Yu; Horng-Jou Wang; Chi-Feng Lin; Chin-Ming Chen
Original assignee: Delta Electronics Inc
Current assignee: Delta Electronics Inc
Priority date: 2005-09-09
Filing date: 2006-07-25
Publication date: 2007-03-15
Also published as: TW200712406A; TWI307399B

Abstract

A heat dissipation module includes a heat pipe and at least one fin, which is connected to and disposed on an external surface of the heat pipe. The heat pipe includes a casing, a wick and a working fluid. The casing has an accommodating space and a bottom portion. The bottom portion has an uneven surface facing the accommodating space. The wick is disposed over the uneven surface of the bottom portion and the working fluid is filled within the casing.

Description

This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application Nos. 094130972 filed in Taiwan, Republic of China on Sep. 9, 2005, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of Invention
The invention relates to a heat dissipation module, and in particular to a heat dissipation module having a heat pipe with high dissipation efficiency.
2. Related Art
With the continuous progress of the industrial technology, various electronic products are developed toward small size, light weight, and low power-consumption. Because the energy utilized efficiency of the electronic element cannot reach 100 percent, some power is wasted and thus converted into heat, which rises the temperature in the system. When the temperature of the system exceeds the allowable operating temperature, the physical property of the electronic element changes and the system becomes abnormal and the operation error or the function halt occurs. In addition, when the temperature in the system is getting higher and higher, the fault rate of the system also increases.
In order to make the system have a higher reliability, the operating temperature of the system has to be kept within a proper range. In order to enhance the heat dissipation efficiency of the electronic element, the heat of the heat source is mostly conducted out via a heat sink, and then transferred to the environment through the fin of the heat sink by way of natural or forced convection.
Because a heat pipe can transfer a lot of heat by a considerable distance with a quite small cross section and a quite small temperature difference, and the heat pipe can work without exterior power supply, the heat pipe has become one of the most widely used heat conducting elements in the electronic heat dissipation product.
FIG. 1 is a schematically cross-sectional view showing a conventional heat pipe 10. The heat pipe 10 has a tube wall 11, a wick 12 disposed on the tube wall 11, and a working fluid filled within the heat pipe 10. The heat pipe 10 has one end serving as an evaporating end “A”, and the other end serving as a condensing end “B”. The evaporating end “A” contacts the heat source (not shown). The working fluid at the evaporating end “A” absorbs heat and evaporates into vapor, which flows to the condensing end “B” naturally under the influence of the pressure difference. Then, the vapor releases the latent heat and condenses into liquid at the condensing end “B”. The condensed working fluid flows back to the evaporating end “A” due to the capillary force of the wick 12. The circulation is made repeatedly such that the heat dissipation effect can be achieved.
FIG. 2 is a schematic illustration showing a dashed-line portion C of the heat pipe of FIG. 1. Referring to FIGS. 1 and 2, the wick 12 of the conventional heat pipe 10 has a uniform thickness. If the wick 12 is thick, this can increase the liquid-containing amount of the wick at the evaporating end “A” but tends to make the vaporized bubble “G”, which is produced during the phase change procedure, be congested in the wick 12 and thus influences the mechanism of re-filing the working fluid. As the result, the performance of the heat pipe 10 is deteriorated. On the contrary, if the wick 12 is thin, this prevents the vaporized bubble G from being congested but decreases the liquid-containing amount of the wick at the evaporating end “A”. Thus, the heat that can be dissipated by the heat pipe 10 is reduced, or the dry-out phenomenon may occur.
Thus, it is an important subject of the invention to solve the problem of congestion of the vaporized bubble caused by the thickness of the wick, enlarge the heat exchanging area of the heat pipe effectively, and thus enhance the overall heat dissipation efficiency.

SUMMARY OF THE INVENTION

In view of the foregoing, the invention is to provide a heat dissipation module and a heat pipe thereof capable of solving the prior art problems of the congestion of the vaporized bubble, effectively enlarging the heat exchanging area of the heat pipe and enhancing the overall heat dissipation efficiency.
The invention achieves the above-identified object by providing a heat pipe, which includes a casing, a wick and a working fluid. The casing has an accommodating space and a bottom portion. The bottom portion has an uneven surface facing the accommodating space. The wick is disposed on the surface of the bottom portion, and the working fluid is filled within the casing.
The invention also achieves the above-identified object by providing a heat dissipation module including a heat pipe and at least one fin. The heat pipe includes a casing, a wick and a working fluid. The casing has an accommodating space and a bottom portion. The bottom portion has an uneven surface facing the accommodating space. The wick is disposed on the surface, and the working fluid is filled within the casing. The fins are disposed on an external surface of the heat pipe and connected to the heat pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more fully understood from the detailed description given herein below illustration only, and thus is not limitative of the present invention, and wherein:
FIG. 1 is a schematically cross-sectional view showing a conventional heat pipe;
FIG. 2 is a schematic illustration showing a dashed-line portion C of the heat pipe of FIG. 1;
FIG. 3A is a schematic illustration showing a heat pipe according to a preferred embodiment of the invention;
FIG. 3B is a schematic illustration showing a dashed-line portion D of FIG. 3A;
FIGS. 4 and 5 are schematic illustrations showing another two wicks of FIG. 3B;
FIGS. 6 to 8 are schematic illustrations showing various shapes of the cross section of a casing of the heat pipe;
FIG. 9 is a schematic illustration showing a column-like heat pipe according to the preferred embodiment of the invention;
FIG. 10 is a schematic illustration showing a heat dissipation module according to the preferred embodiment of the invention; and
FIGS. 11 and 12 are schematic illustrations showing another two heat dissipation modules according to another two embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements.
FIG. 3A is a schematic illustration showing a heat pipe according to a preferred embodiment of the invention. FIG. 3B is a schematic illustration showing a dashed-line portion D of FIG. 3A. Referring to FIGS. 3A and 3B, a heat pipe 20 of the embodiment is a plate-like heat pipe and includes a casing 21, a wick 22 and a working fluid W. The casing 21 has an accommodating space 211 and a bottom portion 212. In this embodiment, the casing 21 is a hollow plate-like casing and is made of copper, silver, aluminum or the alloy thereof, or a material with high thermal conductivity. Thus, when the bottom portion 212 of the casing 21 contacts a heat source (not shown, such as an electronic device generating heat), the heat of the heat source can be transferred to other places quickly. The bottom portion 212 has a surface 213 facing the accommodating space 211, and the accommodating space 211 of the casing 21 is a airtight space.
The surface 213 of the bottom portion 212 is an uneven surface. That is, the bottom portion 212 has a varied thickness. The surface 213 is formed with at least one protrusion 214 or multiple protrusions 214 arranged on the surface 213 to form a checkerboard pattern, a pattern in a row, a symmetrical pattern or an asymmetrical pattern. In FIG. 3B, the surface 213 shows a checkerboard pattern composed of multiple rectangular column-like protrusions 214, and the cross section of the surface 213 has a square shape or a rectangular shape.
The wick 22 is disposed on the surface 213 of the bottom portion 212. Take FIG. 3B as the example, the wick 22 is disposed over the surface 213 of the bottom portion 212 such that the wick 22 faces the accommodating space 211 to form a plane. In other words, the sum of the thickness of the bottom portion 212 of the casing 21 and the thickness of the wick 22 is same. Consequently, the wick 22 has a first thickness H1 and a second thickness H2 in a direction perpendicular to the bottom portion 212. The first thickness H1 is relatively greater than the second thickness H2. Herein, it is to be noted that the designs of the wick 22 and the bottom portion 212 are mainly aimed at the evaporating end “A” of the heat pipe. The wick 22 is made of a material such as a plastic material, a metal, an alloy, a porous non-metallic material or the combination thereof, and the wick 22 is formed on the surface 213 by way of sintering, adhering, filling and/or depositing.
The working fluid W is filled within the casing 21 and the working fluid W is an inorganic compound, pure water, alcohol, ketone, a liquid metal, a refrigerant, an organic compound or a mixture thereof. When the heat pipe 20 is disposed on the heat source, the working fluid W at the end (i.e., the evaporating end A) of the wick 22 close to the heat source absorbs the heat generated by the heat source to evaporate, and the vaporized working fluid further releases its latent heat and condenses back to the liquid working fluid at the end (i.e., the condensing end B) of the wick 22 away from the heat source. Then, the capillary force provided by the wick 22 forces the fluid to flow back to the evaporating end A. The circulation is made continuously such that the heat is transferred away from the heat source continuously and the heat dissipation can be achieved.
Because the bottom portion 212 of the casing 21 has the uneven surface 213, the surface contact area between the casing 21 and the wick 22 is increased, which is advantageous to the enhancement of the heat dissipation performance of the heat pipe 20. Furthermore, because the wick 22 has the uneven thickness, the portion (i.e., the portion above the protrusion 214) having the smaller thickness “H2” enables the working fluid to evaporate easily and separate from the wick 22 so as to avoid the boiling of the working fluid between the bottom portion 212 and the wick 22 and the problem of congestion caused by the vaporized bubble. On the other hand, the sufficient liquid working fluid W can be provided at the portion (i.e., the portion without the protrusion 214) having the larger thickness “H1” in order to supplement the fluid to the portion having the smaller thickness “H2” and to avoid the dry-out phenomenon.
However, the invention is not limited to the above-mentioned embodiments, in which the wick 22 is disposed over the surface 213 of the bottom portion 212 such that the wick 22 faces the accommodating space 211 to form a plane. Furthere, the wick 22 may also be disposed along the profile of the surface 213 such that the wick 22 also forms an uneven surface. That is to say, the wick 22 has the single uniform thickness on the surface 213. For example, as shown in FIGS. 4 and 5, the wick 22′ on the protrusion 214′ has a thickness H1′, and the wick 22′ on the bottom portion 212′ without the protrusion 214′ has a thickness H2′. The thickness H1′ may be equal or unequal to the thickness H2′ according to the users' requirements.
Because the wick 22′ is disposed along the profile of the surface 213′, the surface contact area of the wick 22′ exposed to the accommodating space is increased and thus the evaporating area is enlarged, which is advantageous to the enhancement of the overall efficiency of the heat pipe. In addition, the surface 213′ of the bottom portion 212′ is an uneven surface such that the surface contact area between the casing and the wick is enlarged and the heat dissipation performance of the heat pipe can be enhanced.
Furthermore, the shape of the cross section of the bottom portion 212′ of the casing is not particularly limited, and may be a square shape or a rectangular shape as shown in FIGS. 3B and 4, or a triangular shape (FIG. 5), a semi-spheral shape (FIG. 6), an arc shape (FIG. 7) or a trapezoidal shape (FIG. 8). In addition, the shape of the cross section may be a discontinuous pattern or a curved surface.
In addition, the heat pipe 20 in FIG. 3A has the hollow plate-like casing 21 as the example. However, the casing 21 may also have other different shapes according to the shapes of the to-be-used heat sources. So, the bottom portion 212 of the casing 21 may have a circular shape, a rectangular shape, or other geometric shapes. FIG. 9 is a schematic illustration showing a column-like heat pipe 30 according to the preferred embodiment of the invention. Referring to FIG. 9, the heat pipe 30 of the embodiment includes a casing 31, a wick 32 and a working fluid W. The wick 32 and the working fluid have the same technological features and functions as the wick 22 and the working fluid W of the first embodiment, and detailed descriptions thereof will be omitted.
The casing 31 has a hollow column-like casing and has an accommodating space 311 and a bottom portion 312. The bottom portion 312 has an uneven surface 313 facing the accommodating space 311. The casing 31 further has a cover plate 314 and a sidewall 315. The sidewall 315 is disposed around the bottom portion 312, and the cover plate 314 is disposed opposite to the bottom portion 312. In the hollow column-like casing 31, the evaporating end of the heat pipe 30 is located at the bottom portion 312 while the condensing end of the heat pipe 30 is located at the sidewall 315. Because the bottom portion 312 of the casing 31 has the uneven surface 313, the surface contact area between the bottom portion 312 and the wick 32 may be increased such that the efficiency of the heat pipe 30 can be enhanced. In addition, if the wick 32 disposed over the surface 313 of the bottom portion 312 is also uneven, the surface contact of the wick 32 exposed to the accommodating space 311 may be enlarged, and the efficiency of the heat pipe 30 is enhanced.
FIG. 10 is a schematic illustration showing a heat dissipation module 40 according to the preferred embodiment of the invention. Referring to FIG. 10, the heat dissipation module 40 includes a heat pipe 50 and at least one fin 60. The heat pipe 50 includes a casing 51, a wick 52 and a working fluid W. The heat pipe 50 may have the same technological features as the heat pipe 20 of FIG. 3A and the heat pipe 30 of FIG. 9, and detailed descriptions thereof will be omitted.
In FIG. 10, the heat pipe 50 is a plate-like heat pipe. That is to say, the casing 51 is a hollow plate-like casing. Of course, the casing 51 may also be a column-like casing as shown in FIG. 11 or 12. The fins 60 are manufactured by way of aluminum extrusion and are disposed on an external surface of the heat pipe 50 and connected to the heat pipe 50. The fins 60 are connected to the heat pipe 50 by way of welding, embedding, engaging or adhering. The fins 60 may directly contact the heat pipe 50. Alternatively, a soldering paste, a grease or a material capable of serving as a heat sink interface may be coated between the fins 60 and the heat pipe 50.
The fins 60 are disposed on the plate-like heat pipe 50. Alternatively, the heat pipe 50′ is mounted and fit within the fins 60′ or 60″, as shown in FIG. 11 or 12, and the fins 60′ or 60″, are embedded in and/or engaged with the heat pipe by way of hot mounting. The fins 60, 60′ or 60″ may be disposed in a horizontal interval distribution, a vertically interval distribution, a slantingly interval distribution, a radial distribution, or other distributions.
Referring again to FIG. 10, the heat dissipation module 40 may be applied to a heat source (not shown), and the heat pipe 50 contacts the heat source directly or indirectly via an external base “S”. As shown in FIG. 10, the base “S” is a solid metal block, one side of the base “S” contacts the bottom portion 512 of the casing 51 of the heat pipe 50, and the other side of the base “S” contacts the heat source. The heat generated by the heat source can be quickly conducted to the casing 51 of the heat pipe 50 and then to the fins 60 according to the high conducting property of the base “S”. The heat source is an electronic element, such as a CPU (Central Processing Unit), a transistor, a server, an advanced graphics card, a hard disk, a power supply, a mobile control system, a multimedia electronic mechanism, a wireless communication transceiver station or an advanced game machine, which generates the heat. In addition, the heat dissipation module 40 may further be combined with a fan to dissipate heat, which facilitates heat dissipation more quickly.
As mentioned in the heat dissipation module and the heat pipe thereof according to the invention, the casing has the bottom portion having the uneven surface such that the surface contact area between the casing and the wick is increased, which is advantageous to the enhancement of the heat dissipation performance of the heat pipe. In addition, the wick disposed over the surface to form a plane has a varied thickness. The portion with the smaller thickness enables the working fluid to evaporate easily and thus avoid the problem of congestion caused by the boiling and the vaporized bubble between the bottom portion and the wick. The portion with the larger thickness can provide the sufficient liquid working fluid for supplementation to the portion with the smaller thickness and avoid the occurrence of the dry-out phenomenon. In addition, the wick disposed along the profile of the surface of the bottom portion of the casing can enlarge the surface contact area of the wick to expose to the accommodating space, and thus enlarges the evaporating area, whereby the dissipation efficiency of the heat pipe is improved.
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.

Claims

1. A heat pipe, comprising:

a casing having an accommodating space and a bottom portion, the bottom portion having an uneven surface facing the accommodating space;

a wick disposed on the surface; and

a working fluid filled within the casing.

2. The heat pipe according to claim 1, wherein the casing comprises copper, silver, aluminum or alloy thereof, or a material with high thermal conductivity.

3. The heat pipe according to claim 1, wherein the casing is a hollow plate-like casing or a hollow column-like casing.

4. The heat pipe according to claim 1, wherein the casing further has a cover plate opposite to the bottom portion, and a sidewall mounted around the bottom portion.

5. The heat pipe according to claim 1, wherein a cross section of the bottom portion of the casing has a semi-spheral shape, an arc shape, a triangular shape, a square shape, a rectangular shape or a trapezoidal shape, and the bottom portion has a circular or rectangular profile.

6. The heat pipe according to claim 1, wherein the surface is formed with at least one protrusion or a plurality of protrusions arranged in a checkerboard pattern, a pattern in a row, a symmetrical pattern or an asymmetrical pattern.

7. The heat pipe according to claim l, wherein the wick is disposed over the surface such that the wick faces the accommodating space to form a plane.

8. The heat pipe according to claim 7, wherein the wick has a first thickness and a second thickness in a direction perpendicular to the bottom portion, and the first thickness is relatively greater than the second thickness.

9. The heat pipe according to claim 1, wherein the wick is disposed along a profile of the surface, and the wick on the surface has a uniform thickness or a varied thickness.

10. A heat dissipation module, comprising:

a heat pipe comprising a casing, a wick and a working fluid, the casing having an accommodating space and a bottom portion, the bottom portion having an uneven surface facing the accommodating space, the wick being disposed on the surface, and the working fluid being filled within the casing; and

at least one fin disposed on an external surface of the heat pipe and connected to the heat pipe.

11. The heat dissipation module according to claim 10, wherein the casing comprises copper, silver, aluminum or alloy thereof, or a material with high thermal conductivity.

12. The heat dissipation module according to claim 10, wherein the casing is a hollow plate-like casing or a hollow column-like casing.

13. The heat dissipation module according to claim 10, wherein the casing further has a cover plate opposite to the bottom portion, and a sidewall mounted around the bottom portion.

14. The heat dissipation module according to claim 10, wherein a cross section of the bottom portion of the casing has a semi-spherical shape, an arc shape, a triangular shape, a square shape, a rectangular shape or a trapezoidal shape, and the bottom portion has a circular or rectangular profile.

15. The heat dissipation module according to claim 10, wherein the surface is formed with at least one protrusion or a plurality of protrusions arranged in a checkerboard pattern, a pattern in a row, a symmetrical pattern or an asymmetrical pattern.

16. The heat dissipation module according to claim 10, wherein the wick is disposed over the surface such that the wick faces the accommodating space to form a plane.

17. The heat dissipation module according to claim 16, wherein the wick has a first thickness and a second thickness in a direction perpendicular to the bottom portion, and the first thickness is relatively greater than the second thickness.

18. The heat dissipation module according to claim 10, wherein the wick is disposed along a profile of the surface, and the wick on the surface has a uniform thickness or a varied thickness.

19. The heat dissipation module according to claim 10, wherein the heat pipe contacts a heat source via a base or contact the heat source directly so as to transfer heat emitted by the heat source to the fin.