Kids Research Express

For every refrigerant there is a specific boiling, or vaporization, temperature associated with each pressure, so that it is only necessary to control the pressure in the evaporator to obtain a desired temperature. A similar pressure-temperature relationship holds in the condenser. One of the most widely used refrigerants for many years has been dichlorodifluoromethane, known popularly as Refrigerant-12. This synthetic chlorofluorocarbon (CFC) when used as a refrigerant would, for example, vaporize at -6.7° C (20° F) in its evaporator under a pressure of 246.2 kPa (35.7 psi), and after compression to 909.2 kPa (131.9 psi) would condense at 37.8° C (100° F) in the condenser. The resulting condensed liquid would then enter the expansion valve to drop to evaporator pressure and repeat the cycle of absorbing heat at low temperature and low pressure and dissipating heat at the much higher condenser pressure and temperature. In small domestic refrigerators used for food storage, the condense

Refrigerant-12 and related CFCs, Refrigerant-11 and Refrigerant-22, are currently the major compounds used in the cooling and insulation systems of home refrigeration units. It has been found, however, that CFCs are posing a major threat to the global environment through their role in the destruction of the ozone layer . A search has therefore begun for replacements, and some manufacturers of CFCs have already pledged to phase out these products by the end of the century.