HEAT PIPE WITH VARIABLE GROOVED-WICK STRUCTURE AND METHOD FOR MANUFACTURING THE SAME
A heat pipe (10) includes a casing (11), a plurality of grooves (12, 13) defined in the casing, and working fluid contained in the casing. The casing includes a first portion (14) and a second portion (15) having a smaller diameter than the first portion. The grooves (12) at the first portion of the casing have greater apex angles and smaller groove width than those of the grooves (13) at the second portion. A method for manufacturing the heat pipe includes the steps of: providing a casing with a plurality of grooves defined in an inner wall thereof; shrinking a diameter of one portion of the casing to enable the portion to function as an evaporator section of the heat pipe; vacuuming and placing a predetermined quantity of working fluid in the casing; sealing the casing to obtain the heat pipe.
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1. Field of the Invention
The present invention relates generally to a heat pipe for transfer or dissipation of heat from heat-generating components, and more particularly to a heat pipe with variable grooved-wick structure defined therein for increasing heat transfer capability thereof.
2. Description of Related Art
Nowadays, thermal modules are widely used in notebook computers to dissipate heat generated by CPUs. The thermal module includes a blower, a fin assembly, and a heat pipe. The heat pipe has an evaporator section and a condenser section respectively connected with a CPU and the fin assembly so as to transfer heat generated by the CPU to the fin assembly. The fin assembly is arranged at an air outlet of the blower to dissipate heat absorbed from the condenser section of the heat pipe to the surrounding environment.
In the thermal module, the evaporator section of the heat pipe usually has a smaller area than the condenser section. Accordingly, a contacting area between the evaporator section of the heat pipe and the CPU is smaller than that between the condenser section of the heat pipe and the fin assembly. Therefore, the radial power density which the evaporator section of the heat pipe undergoes is greater than that the condenser section of the heat pipe needs to undergo.
In a conventional grooved heat pipe, grooves at the evaporator section thereof have similar groove shapes to grooves at the condenser section thereof. This means the evaporator section of the conventional grooved heat pipe has the same radial power density as the condenser section thereof, which limits the increase of the heat transfer capability of the conventional grooved heat pipe and further limits the increase of the heat dissipating efficiency of the thermal module. Thus, it can be seen that improvement of the radial power density of the evaporator section of the heat pipe is key to improve the heat dissipation efficiency of the thermal module.
SUMMARY OF THE INVENTIONThe present invention relates to a heat pipe for removing heat from heat-generating components and a method for manufacturing the same. The heat pipe includes a casing, a plurality of grooves defined in the casing, and working fluid contained in the casing. The casing includes a first portion and a second portion having a smaller diameter than the first portion. The grooves at the first portion of the casing have smaller groove width than that of the grooves at the second portion. The method includes the steps of: providing a casing with a plurality of tiny grooves defined in an inner wall thereof; shrinking a diameter of one portion of the casing to function the portion as an evaporator section of the heat pipe; vacuuming and placing a predetermined quantity of working fluid in the casing; sealing the casing to obtain the heat pipe.
Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiment when taken in conjunction with the accompanying drawings, in which:
Many aspects of the present invention 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 invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views:
Referring to
The casing 11 is a metallic hollow tube having a ring-like transverse cross section and a uniform thickness T along a longitudinal direction thereof. The casing 11 includes an evaporator section 15 disposed at an end thereof, a condenser section 14 disposed at the other end thereof, and an adiabatic section 17 disposed between the evaporator and the condenser sections 15, 14. A diameter of the evaporator section 15 is smaller than that of the condenser section 14. A transition section 16 is formed between the evaporator section 15 and the adiabatic section 17. A diameter of the transition section 16 is gradually decreased from the adiabatic section 17 towards the evaporator section 15 so that the transition section 16 has a taper-shaped configuration.
The working medium is usually selected from a liquid which has a low boiling point and is compatible with the casing 11, such as water, methanol, or alcohol. Thus, the working medium can easily evaporate to vapor when it receives heat in the evaporator section 15 and condense to liquid when it dissipates heat in the condenser section 14.
The grooves are coextensive with a central longitudinal axis of the casing 11. Grooves 12 at the evaporator section 15 of the casing 11 have substantially similar heights H to the grooves 13 at the condenser section 14 thereof. An apex angle A1 of each of the grooves 12 at the evaporator section 15 is greater than an apex angle A2 of each of the grooves 13 at the condenser section 14. A top width W1 of each of the grooves 12 at the evaporator section 15 is smaller than a top width W3 of each of the grooves 13 at the condenser section 14, whilst a bottom width W2 of each of the grooves 12 at the evaporator section 15 is smaller than a bottom width W4 of each of the grooves 13 at the condenser section 14. This means a middle width (groove width) of each of the grooves 12 at the evaporator section 15 is smaller than that of each of the grooves 13 at the condenser section 14.
Referring to
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In the present heat pipe 10, each of the grooves 12 at the evaporator section 15 has smaller groove width and greater apex angle than that of each of the grooves 13 at the condenser section 14. This increases the density of the grooves 12 at the evaporator section 15 of the heat pipe 10. The radial power density the evaporator section 15 of the heat pipe 10 can undergo is therefore increased, and the thermal resistance of the evaporator section 15 of the heat pipe 10 is decreased. Thus, the heat transfer capability of the heat pipe 10 is improved. In addition, the capillary action generated by the grooves 12 at the evaporator section 15 of the heat pipe 10 is increased, which increases the heat transfer capabilities of the heat pipe 10. The heat transfer capability of the heat pipe 10 is improved according to the shrinkage of the evaporator section 15 of the heat pipe 10, which simplifies the manufacturing of the heat pipe 10. In this way the present heat pipe 10 is adapted for mass production.
In the present heat pipe 10, the evaporator section 15 and the condenser section 14 are respectively disposed at two ends of the casing 11. Alternatively, referring to
It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, 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 invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
Claims
1. A heat pipe comprising:
- a casing comprising a first portion and a second portion having a smaller diameter than the first portion;
- a plurality of grooves defined in an inner wall of the casing; and
- a predetermined quantity of bi-phase working fluid contained in the casing;
- wherein the grooves at the first portion of the casing have smaller groove width than that of the grooves at the second portion.
2. The heat pipe of claim 1, wherein the grooves extends along a central axis of the casing.
3. The heat pipe of claim 1, wherein the grooves at the first portion of the casing have greater apex angles than that of the grooves at the second portion.
4. The heat pipe of claim 1, wherein the first portion is an evaporator section of the heat pipe, whilst the second section is a condenser section of the heat pipe.
5. The heat pipe of claim 4, wherein the evaporator section is disposed at an end of the heat pipe.
6. The heat pipe of claim 4, wherein the evaporator section is disposed at a middle portion of the heat pipe.
7. The heat pipe of claim 1 further comprising a transition section disposed between the first portion and the second portion, a diameter of the transition section being gradually decreased from the second portion towards the first portion.
8. The heat pipe of claim 1, wherein the casing of the heat pipe is flat in profile.
9. A method for manufacturing a heat pipe with variable grooved-wick structure comprising the steps of:
- providing a casing with a plurality of tiny grooves defined in an inner wall thereof;
- shrinking a diameter of one portion of the casing via a shrinkage tool to enable it to function as an evaporator section of the heat pipe;
- vacuuming and placing a predetermined quantity of working fluid in the casing; and
- sealing the casing to obtain the heat pipe.
10. The method as described in claim 9, wherein the grooves are axially carved in the inner wall of the casing.
11. The method as described in claim 9, wherein the shrinkage tool is a high speed spinning tube shrinkage tool, the shrinkage process of the evaporator section comprises the step of controlling the high speed spinning tube shrinkage tool to move towards the evaporator section of the casing along a central longitudinal axis thereof so as to shrink the diameter thereof.
12. The method as described in claim 11, wherein the high speed spinning tube shrinkage tool comprises a tapered portion which enables to compress an outer wall of the evaporator section so as to shrink the diameter thereof and a guiding portion which guides the movement of the high speed spinning tube shrinkage tool.
13. The method as described in claim 12, wherein the high speed spinning tube shrinkage tool further comprises a diminished portion, the tapered portion being disposed between the guiding portion and the diminished portion.
14. The method as described in claim 9, wherein the shrinkage tool is a spinning stamping tube shrinkage tool, the shrinkage process of the evaporator section comprises the step of controlling the spinning stamping tube shrinkage tool to move towards the evaporator section of the casing along a radial direction of the casing so as to shrink the diameter of the evaporator section.
15. The method as described in claim 14, wherein the shrinkage process of the evaporator section further comprises the step of controlling the spinning stamping tube shrinkage tool to move towards the evaporator section of the casing along a central longitudinal axis of the heat pipe in order to obtain a predetermine length for the evaporator section.
16. The method as described in claim 14, wherein the spinning stamping tube shrinkage tool includes more than two sub-tools with arc-shaped inner surfaces thereof distributed around an imaginary circle which is coaxial with and surrounds the casing.
17. The method as described in claim 16, wherein each of the sub-tools comprises diminished portion and a tapered portion connecting with the diminished portion at an end thereof, a diameter of the tapered portion being gradually increased from the end towards an opposite end thereof.
18. The method as described in claim 17, wherein each of the sub-tools further comprises an enlarged portion connecting with the tapered portion at the opposite end thereof.
Type: Application
Filed: Nov 3, 2006
Publication Date: May 8, 2008
Applicant: FOXCONN TECHNOLOGY CO., LTD. (Tu-Cheng)
Inventors: CHANG-SHEN CHANG (Tu-Cheng), JUEI-KHAI LIU (Tu-Cheng), CHAO-HAO WANG (Tu-Cheng), HSIEN-SHENG PEI (Tu-Cheng)
Application Number: 11/556,613
International Classification: F28D 15/00 (20060101);