Thermosyphons are passive heat transfer devices that operate on the simple process of convection through vaporization and condensation. Heat transfer will only occur when the low end of the unit is warmer that the high end.


Ther refrigeration cycle is similar to that of  mechanical refrigeration plant in that the refrigerant changes phase from liquid to vapour to liquid as it boils and condenses. The temperature differential across the thermosyphon drives the heat transfer like the compressor in a mechanical plant and the larger the temperture differential the higher the heat transfer rate.


In the context of Thermo Probes and Thermo Piles, the conductance of a thermosyphon is a function of three main resistances:

• Heat flow to the evaporator

• Thermosyphon internal resistance

• Heat flow away from the radiator