Optimal volume ratio of two stage rotary compressor using R32/R1234ze(E) mixtures.

Refrigerant mixtures are commonly regarded as potential substitutes because rare pure refrigerants can totally meet all the requirements of environment, thermodynamic performance and safety. Meanwhile, as an effective means, two-stage compression system is widely applied to improve the performance of heat pump under large pressure ratio. The volume ratio of high-pressure stage to the low-pressure stage is a critical parameter for performance, which is largely effected by refrigerants. In this paper, R32/R1234ze(E) mixtures are chosen as typical blend refrigerant to study the impact of concentration on the optimal volume ratio. The result indicates that the optimum volume ratio of mixtures is less than the pure composition which make up the mixtures.