Operation of Heat Pipe:
Hollow cylinder filled with a vaporizable liquid under vacuum. The Heat Pipe functions as
follows
Heat is absorbed in the evaporating section.
Fluid boils to vapor phase.
Heat is taken away from the upper part of cylinder to the environment; then vapor
condenses to liquid phase.
Liquid returns by gravity force to the lower part of cylinder (i.e. evaporating section).
When heat is added to the evaporator section, the working fluid is boiled and converted into
vapor absorbing latent heat.
After reaching at the condenser section, due to partial pressure build up, the vapor is
transformed backwards into liquid thus latent heat is released. From the condenser section,
heat is then taken out by means of air cooling/water cooling with fins etc. The liquid then
returns to the original position through the capillary return method, thus completes the cycle.
Due to very high latent heat of fluid vaporization a large quantity of heat is transferred.
Heat pipes are vacuum vessels that are filled partially with a working fluid, typically water/air in
electronic cooling, which serves as the heat transfer medium. The heat pipe envelope is made
of copper in different types of shapes including rectangular, cylindrical, or any other enclosed
type. The wall of the pipe is lined with a wick structure, which provides surface area for the
capillary capability and condensation /evaporation cycle. Since the heat pipe is evaporated and
then charged with the working fluid prior to being sealed, the internal pressure required is set
by the vapor pressure of the working media.
When heat is applied to the surface of the heat pipe, the working water is vaporized. The vapor
formed at the evaporator section is at a slightly higher in temperature and pressure than other
areas. This creates a pressure gradient that forces the vapor to flow towards the cooler regions
of the heat pipe. As the vapor condenses on the heat pipe walls, the latent heat of vaporization