Common Questions About Heat Pipes 0 pages

LIQUID RETURN

LIQUID TURNING TO VAPOR

WICK STRUCTURE

A heat pipe is a heat transfer device with an extremely high effective thermal conductivity. Heat pipes are evacuated vessels, typically circular in cross sections, which are back-filled with a small quantity of a working fluid. They are totally passive and are used to transfer heat from a heat source to a heat sink with minimal temperature gradients, orto isothermalize surfaces.

Heat pipes transfer heat by the evaporation and condensation of a working fluid. As stated above, a heat pipe is a vacuum tight vessef which is evacuated and partially back-filled with a working fluid. As heat is input at the evaporator, fluid is vaporized, creating a pressure gradient in the pipe. This pressure gradient forces the vapor to flow along the pipe to the cooler section where it condenses, giving up its latent heat of vaporization. The working fluid is then returned to the evaporator by capillary forces developed in the porous wick structure or by gravity.

Yes; a heat pipe is said to be operating against gravity when the evaporator is located above the condenser. In this orientation, the working fluid must be pumped against gravity back to the evaporator. All heat pipes have wick structures that pump the working fluid back to the evaporator using the capillary pressure developed in the porous wick. The finer the pore radius of a wick structure, the higher against gravity the heat pipe can operate. A thermosyphon is similar to a heat pipe, but has no wick structure and wifi only operate gravity aided.

Heat pipe working fluids range from Heltum and Nitrogen for cryogenic temperatures, to liquid metals like Sodium and Potassium for high temperature applications. Some of the more common heat pipe fluids used for electronics cooling applications are ammonia, water, acetone, and methanol,

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