Refrigeration

Refrigeration, removal of heat from an enclosure in order to lower its temperature. It is used for freezing water or food, for food preservation, for air conditioning, and for low-temperature chemical processes and cryogenics studies and applications. Modern refrigerators are insulated cabinets containing a compressor, which forces a refrigerant gas, such as ammonia or freon, to pass through a condenser; losing heat through condensation, the refrigerant gas goes through refrigeration coils, where it vaporizes, removing heat from the coils, and returns as a gas to the compressor for another cycle. In another system compression is accomplished by absorbing the refrigerant in a secondary fluid, such as salt water, and pumping the solution through a heat exchanger to a generator, where it is heated to drive off the refrigerant at high pressure. Other cycles, similar in principle, using steam or air, are also used.