Influence of composition of binary mixed working fluids on the performance of cascade heat pump

Abstract

The optimized design of the cascade heat pump facilitates the recovery and reuse of waste heat in printing and dyeing wastewater. This paper constructs a cascade heat pump system with two-stage cycles sampling the same binary mixed working fluids. The effects of three kinds of combinations of working fluids, including R134a/R152a, R134a/R22, and R152a/R22, on the COP and heating power, are discussed through the thermodynamic cycle process simulation when the component ratio varies. It is found that, for the R134a/R152a mixed working fluids, the system performance can be adjusted approximately linearly by changing the component ratio. For the two mixed working fluids of R134a/R22 and R152a/R22, the performance of the cascade heat pump system is closer to the case of using pure R134a and R152a as corresponding working fluids. The system’s heating capacity is significantly reduced, compared with the case of pure R22 employed. Besides, with the component ratio of working fluid increasing, the COP and heating power change with opposite trends.