Energy
Energy can neither be created nor destroyed. It can be converted from one form to another. The total amount of energy in universe always remains constant. The principle of total energy in universe being constant, and the fact that demand for energy exceeds day by day creating an energy crisis scenario forces to think in the direction of energy saving.Heat is a form of energy to which abides to the principle of energy conservation. Heat can flow naturally from higher potential (higher temperature) to lower (lower temperature). However to transfer heat from lower temperature to higher, we need to have mechanism and some energy input. Refrigeration cycle provisions this flow of heat from lower temperature to higher temperature.
