Performance Research on Heat Pump Using Blends of R744 with Eco-friendly Working Fluid

In order to protect the environment and save energy, new refrigerants with zero ozone depleting potential, low global warming potential have been investigated by more and more researches to substitute HCFCs/HFCs for eco-friendly working fluid. Among alternatives, non-azeotropic mixtures are becoming the more potential and important candidates. In this research, the transcritical system performances of water heater heat pump using R744/DME (dimethyl ether) binary mixture as working fluid were theoretically analyzed. On mix R744 with DME in a smaller mass fraction, both the optimum heat rejection pressure and the heating coefficient of performance (COP) are decreased. The mean relative reduction rate of optimum heat rejection pressure, however, is greater than that of heating COP. Also, the influence of superheat degree at the inlet of compressor upon the optimum heat rejection pressure and the heating COP is also discussed. The results show that the R744/DME can work as a promising alternative to replace with current widely-used Freons. (C) 2017 The Authors. Published by Elsevier Ltd.