Numerical investigations on the performance of a single-stage auto-cascade refrigerator operating with two vapor–liquid separators and environmentally benign binary refrigerants

The performance of auto-cascade refrigerator operating with two vapor–liquid separators and six binary refrigerants (R23/R134a, R23/R227ea, R23/R236fa, R170/R290, R170/R600a and R170/R600) was investigated with a new approach at the temperature level of −60 °C. The results show that the pressure ratio, the composition of mixed refrigerants, the main stream ratio and the pressure level are the main factors affecting COP, which deserve a good balance in the optimization. The overall and local matching of heat capacity rates of the hot and cold refrigerants in the recuperators are both important for the improvement of COP. Among these binary refrigerants, the 0.55 mol fraction of R23 for R23/R236fa and R170 for R170/R600 are the most prospective compositions in the nonflammable refrigerants and natural refrigerants for medium suction pressure compressors, respectively. The new approach employed in this paper also suggests a promising application to the optimization of the performance with multi-component refrigerants and different temperature levels.