What is Heat Pipe?
"A Heat Pipe may be regarded as a synergistic engineering structure which is equivalent to a material having a thermal conductivity greatly exceeding that of any known metal."- Grover (Los Alamos National Laboratory)
In simpler words, a Heat Pipe can transfer about thousand times more heat than a geometrically equivalent copper rod.
Most common Heat Pipe comprises of a high thermal conductivity metal (copper/aluminium) tube with a capillary wick (metal mesh/sintered metal powder/axial grooves) on its inner wall. This tube is evacuated and charged with a specific amount of working fluid. The working fluid is selected in accordance with the operating temperature range of Heat Pipe and its merit number.
When heat is added to the evaporator section, the working fluid in this section evaporates, absorbing the latent heat of evaporation. The vapours of working fluid travel at enormous speeds to the condenser section of the Heat Pipe. In the condenser section, the vapours condense, giving out the absorbed heat. The condensed liquid, then returns to the evaporator section with the help of capillary wick. As the latent heat of the working fluid is very high, large amount of heat can be transferred with a very small temperature drop across the ends of a Heat Pipe.