ABSTRACT
Refrigerant mixtures were introduced for heat pump applications primarily to meet environmental concerns. However, the use of refrigerant mixtures was considered as early as the late 1800s and then again in the 1950s and thereafter to improve their capacity control and energy efficiency. The use of mixtures was studied as alternatives of hydrochlorofluorocarbons (HCFCs) after the inclusion of HCFCs as one of controlled substances in the Montreal Protocol in 1992.
