A heat pipe is a device that efficiently transports thermal energy from its one point to the other. It utilizes the latent heat of the vaporized working fluid instead of the sensible heat. As a result, the effective thermal conductivity may be several orders of magnitudes higher than that of the good solid conductors. A heat pipe consists of a sealed container, a wick structure, a small amount of working fluid that is just sufficient to saturate the wick and it is in equilibrium with its own vapor. The operating pressure inside the heat pipe is the vapor pressure of its working fluid. The length of the heat pipe can be divided into three parts viz. evaporator section, adiabatic section and condenser section. In a standard heat pipe, the inside of the container is lined with a wicking material.

Container:

The function of the container is to isolate the working fluid from the outside environment. It has to be there for leak proof, maintain the pressure differential across the walls, and enable transfer of thermal energy to take place from and into the working fluid.

The prime requirements are:

1. Compatibility (Both with working fluid and External environment)
2. Porosity
3. Wettability
4. Ease of fabrication including welding, machinability and ductility
5. Thermal conductivity
6. Strength to weight ratio