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.
The 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.
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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.