BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat dissipating apparatus, and more particularly to a heat dissipating apparatus used for battery set or heat-generating electronic device and employing gas-liquid phase transition of a heat-guiding unit to convey heat from the battery set or heat-generating electronic device.
2. Description of Prior Art
As the progress of electronic technology and the demand of consumer product, the electronic devices and electrical machines are powered by battery set composed of cells in serial or parallel connection to provide power. The battery set composed of cells can provide high power energy with low pollution. Therefore, the battery set can be advantageously applied to electrical tool, electrical motorcycle, and electrical car. However, there is huge transient current for battery set in those applications and the battery set has the problem of high temperature. Moreover, the chipset and CPU in computer become smaller and work in higher frequency. The heat dissipation for battery set and computer become serious issue,
- SUMMARY OF THE INVENTION
Conventional heat dissipating apparatus for battery set comprises a metal pad between two adjacent cells to form a battery set. The metal pad provides thermal conduction for heat and conveys heat from the battery set. The conveyed heat is dissipated by air convection. However, the cells are arranged in stacked manner and the effective heat-dissipating area is not enough. The thermal conduction and heat-dissipating effect is limited and the battery life is also reduced. Moreover, the working principle of battery set involves with huge transient current. The heat generated is proportional to the square of current. The rate of heat generation will exceed the rate of heat dissipation by natural convection when there is huge transient current. Moreover, the temperature will further rise if the battery set is also charged. The battery set has safety problem if the temperature thereof exceeds 60° C. and the heat dissipating apparatus for battery set is not sufficient.
The present invention is to provide a heat dissipating apparatus used for heat-generating electronic device and employing gas-liquid phase transition of a heat-guiding unit to convey heat from the heat-generating electronic device, whereby the heat-generating electronic device works in a relatively low temperature.
Accordingly, the present invention provides a heat dissipating apparatus for a battery set or heat-generating electronic device. The heat dissipating apparatus comprises a sealing envelope and a heat-guiding unit. The sealing envelope is composed of an upper film, a lower film sealed with the upper film and an accommodation space defined between the upper film and the lower film. The accommodation space is functioned to accommodate the heat-guiding unit and comprises a retaining region and empty regions. The heat-guiding unit comprises a wick structure and a working fluid.
BRIEF DESCRIPTION OF DRAWING
The above summaries are intended to illustrate exemplary embodiments of the invention, which will be best understood in conjunction with the detailed description to follow, and are not intended to limit the scope of the appended claims.
The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself however may be best understood by reference to the following detailed description of the invention, which describes certain exemplary embodiments of the invention, taken in conjunction with the accompanying drawings in which:
FIG. 1 shows a perspective view of the heat dissipating apparatus of the present invention.
FIG. 2 shows an exploded view of the present invention used for a battery set.
FIG. 3 shows a sectional view of the present invention used for a battery set.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 4 shows the application of the present invention used for a battery set.
FIG. 1 shows a perspective view of the heat dissipating apparatus of the present invention. The dissipating apparatus comprises a sealing envelope 10 and a heat-guiding unit 20.
The sealing envelope 10 is made of flexible composite material or metal sheet. The metal sheet could be aluminum foil or other material deformable by heat and could be of rectangular shape, rounded shape or other shape. In the shown embodiment the metal sheet is of rectangular shape. The sealing envelope 10 comprises an upper film 11, a lower film 12 sealed with the upper film 11 and an accommodation space 13 defined between the upper film 11 and the lower film 12.
The heat-guiding unit 20 is arranged in the accommodation space 13 of the sealing envelope 10 and divides the accommodation space 13 into a retaining region 131 and two empty regions 132. The retaining region 131 is functioned to accommodate the heat-guiding unit 20 and the heat-guiding unit 20 comprises a wick structure 21 and a working fluid 22 attached to the wick structure 21. The wick structure 21 could be one of unwoven cloth, metal mesh, sintered metal or other porous material. The working fluid 22 could be liquid with low boiling point such as water, methyl alcohol, acetone, ammonia, coolant or the mixture of above liquids. Moreover, the heat-guiding unit 20 could be extended to the empty regions 132 (not shown).
To assemble the heat dissipating apparatus of the present invention, the heat-guiding unit 20 is placed in the retaining region 131 and then a radio frequency heating machine is used to seal the peripheral of the sealing envelope 10. Moreover, an opening is preformed on one side of the sealing envelope 10 and working fluid 22 in injected into the sealing envelope 10. Afterward, the sealing envelope 10 is vacuumed and sealed to form the heat dissipating apparatus of the present invention.
With reference to FIGS. 2, 3 and 4, the heat dissipating apparatus of the present invention can be applicable to a battery set or a heat-generating electronic device. In the shown embodiment, the heat dissipating apparatus is used for a battery set. The battery set comprises a plurality of cells 3, which can be polymer lithium cells or lithium ion cells with their anodes and cathodes in serial or parallel connection. The heat dissipating apparatus of the present invention is placed between the cells 3. In the embodiment, the battery set is used to power, for example, an electric car. The cell 3 will have maximum output current when the electric car is started or drives uphill. The cell 3 will generate high thermal energy and the thermal energy is conveyed to the wick structure 21 to increase the temperature thereof.
When the temperature reaches a boiling point of the working fluid 22 of the wick structure 21, the working fluid 22 is vaporized and the pressure within the sealing envelope 10 is increased. Therefore, the vapor is driven to the empty region 132 at both sides of the accommodation space 13. The empty regions 132 are expanded due to the vapor and the thermal energy is conveyed by the vapor. The exterior portion of the sealing envelope 10 is in contact with air such that the vaporized working fluid 22 will be cooled to liquid. At this time the empty regions 132 are shrunk due to the condensation of the vapor into liquid. The working fluid 22 flows back to the retaining region 131. Moreover, the working fluid 22 quickly flows back due to the capillary action of the wick structure 21. Therefore, the cell 3 operates at a relatively low temperature.
Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.