1 - Fluid absorbs heat when it turns from a liquid to a gaseous state (from liquid to vapor) and expel heat at the transition from vapor to liquid.
2 - change the condition when the fluid temperature and pressure fixed.
Heat is transferred only three of the body temperature up to body temperature which is less than a hot body to cold body).
4 - metal parts of the evaporator and condenser must be good conductors of heat and must choose the metal does not react with the refrigerant is brass and red copper and aluminum are the most common minerals.
5 - thermal power and other forms of energy can be converted from any one image to another, for example, can turn electrical energy into heat energy, and can Beks turning thermal energy into electrical energy, as well as thermal energy is transformed into energy Miktanikip and so on.