The refrigeration engineering is based on the Laws of Thermodynamics. The relationship of pressure, volume and temperature of all matter is described by these laws. In layman’s terms thermodynamics is basically the application or production of energy, in the form of work or heat, to manipulate or manage the transfer of heat from one system to another. Heat always flows from a system with a high energy state to a low energy system. This allows heat to be manipulated.
Refrigeration Engineering itself is a sub discipline that specifically deals with the removal of heat from a closed system by the application of energy. Refrigeration methods require a cooling agent. In standard home refrigerators, a man-made chemical, like Freon, is used as the cooling agent. In ammonia refrigeration methods, like the gas absorption refrigerator, ammonia is the cooling agent. Semiconductor technology offers a novel use materials to form what is called a thermocouple. This allows direct application of electricity to produce cooling in some applications.