Heat exchange – With adjustor for heat – or exchange material – flow
Reexamination Certificate
2002-02-12
2002-10-08
Atkinson, Christopher (Department: 3672)
Heat exchange
With adjustor for heat, or exchange material, flow
C165S104260, C361S700000, C257S715000, C174S015200
Reexamination Certificate
active
06460612
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of heat transfer devices and more particularly, to a heat transfer device with a self adjusting wick and a method of manufacturing same.
BACKGROUND OF THE INVENTION
A heat transfer device, generally called a “heat pipe”, is a device that can efficiently transfer heat from one point to another. It is often referred to as a superconductor of heat because it possesses an extraordinary heat transfer capacity and rate with almost no temperature drop. A heat pipe typically consists of a sealed aluminum or copper container whose inner surfaces have a capillary wicking material. A heat pipe is based on the principle of closed loop evaporation/boiling and condensation of a fluid. The liquid inside the heat pipe evaporates and/or boils off the areas where heat is dissipated by electronic components (mounted externally to the heat pipe) and travels to the condensation space as vapor. The vapor spreads evenly in the condensation space and condenses back into liquid form by rejecting heat to the ambient. The condensed liquid travels back to the heated section by capillary action through the porous wick structure on the interior of the heat pipe. The quality and type of wick usually determines the performance of the heat pipe. Different types of wicks are chosen depending on the application for which the heat pipe is being used.
The wick structure of a traditional heat pipe remains constant throughout its operating temperature range. Thus, the porosity and pore size of the wick structure cannot be changed during operation. This inhibits the ability to adjust the capillary pressure according to temperature conditions along points within the heat pipe, which in turn, could result in local “dry-out” if a large local heat flux is presented at a point within the heat pipe. This dry-out condition could result in the total failure of the heat pipe. Some variable-wick heat pipes are known. In these heat pipes, a specific wick structure is tailored for the anticipated heat flux distribution. At locations where the highest heat fluxes are expected, the pore size is made small to increase the capillary force. The pore size in other locations is kept larger to allow low resistance to liquid flow. These heat pipes do not have the capability of adjusting the wick structure once the heat pipe is assembled. Thus, the usefulness of these known variable wick heat pipes is limited to the exact heat flux distribution and temperature that they were designed for.
Thus there is a need for an improved heat pipe wherein the capillary pressure of the wick can be adjusted post assembly to prevent dry-out and failure of the heat pipe.
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Chen James P.
Sehmbey Maninder S.
Atkinson Christopher
Motorola Inc.
Williams Lalita P.
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