The mixture of 23% HFC-32/25% HFC-125/52% HFC-134a is a nonflammable, chlorine-free alternative to HCFC-22 that is a close match in capacity and energy efficiency in tests with current design air conditioners and heat pumps. Additional performance improvements are possible through optimisation of the expansion device and other system components, including use of liquid line/suction line heat exchange and counterflow evaporators and condensers. Energy-efficiency values that are 6% to 7% higher than those of HCFC-22 are predicted with the mixture in modified equipment. A study of mixture vapour leakage followed by recharging with the initial composition demonstrated a maximum loss of 9% capacity after five cycles, representing a worst-case effect of leakage.

KEYWORDS: R22, replacing, unit air conditioners, heat pumps, mixtures, R32, R125, R134a, refrigerants, capacity, energy, efficiency, testing, performance, optimisation, calculating, leaking, vapours, comparing, heat transfer coefficient, toxicity, properties, operations