On the refrigerator always there are four component like on the above picture. The refrigeration cycle alternately evaporates (B) and condenses (A) a refrigerant such as Freon-12. Liquid refrigerant stored at high pressure in the receiver is released through an expansion valve (2) into the evaporator coils (3) inside the refrigerator. With the pressure reduced, the refrigerant evaporates and absorbs heat from the interior. A compressor (4) circulates the vaporized refrigerant to the exterior condenser coils (1), where it is condensed by pressure. Heat from inside the refrigerator is lost to the environment there. The cooled liquid then return to the receiver.
Refrigeration is the cooling of a space or its content to a lower value than of the surrounding space or of the ambient atmosphere. Until the advent of modern technology, natural ice was the only mens of refrigeration. Ice act as an efficient refrigerant because the temperature of melting ice remain at 0oC until it is entirely melted. It absorb heat from warmer surroundings, thereby cooling them while not itself becoming warmer until completely melted. Since the time of the Greeks and Romans, snow and ice were harvested in winter and stored in insulated pits for later use. Ice was a valuable cargo for 19th century clipper ships, but it was difficult and expensive to ship. The demand for ice created a strong impetus for inventors to develop artificial cooling methods.
The first successful refrigeration machine in the United States was developed in 1844 by John Gorrie. His device did not use a volatile liquid but operated by the principle that air gets hot when compressed and cools when it expands.
Another type of refrigeration unit, the absorption type machine, was developed by Ferdinand Carre in France between 1850 and 1859. Such device which can operated exclusively by burning natural gas or other fuel, were commonly use prior to the widespread availability of electricity.
