Heat Pipes

Product Description:

A heat pipe is a simple device that can transfer heat from one point to another without having to use an external power supply. It is a sealed tube that has been partially filled with a working fluid. In HVAC applications, this fluid is refrigerant.
The sealed refrigerant - which will boil under low-grade heat - absorbs heat from the warm return air such as in an air-conditioning system and vaporizes inside the tube. The vapor then travels to the other end of the heat pipe (the high end), which is placed in the stream of cold air that is produced by the air conditioner. 
The heat that was absorbed from the warm air at the low end is now transferred from the refrigerant's vapor through the pipe's wall into the cool supply air. This loss of heat causes the vapor inside the tube to condense back into a fluid. The condensed refrigerant then travels by gravity to the low end of the heat pipe where it begins the cycle all over again.