A refrigerant is a compound used in a heat cycle that reversibly undergoes a phase change from a gas to a liquid. Traditionally, fluorocarbons, especially chlorofluorocarbons were used as refrigerants, but they are being phased out because of their ozone depletion effects. Other refrigerants are ammonia, sulfur dioxide, carbon dioxide, and non-halogenated hydrocarbons such as methane. Physical properties The ideal refrigerant has good thermodynamic properties, is unreactive chemically, and saf… (More on Refrigerant)