Theoretical investigation on the performance of a modified refrigeration cycle using binary zeotropic hydrocarbon mixture R170/R290

In this study, a modified refrigeration cycle (MRC) using refrigerant mixture R170/R290 was proposed for applications in low-temperature freezers. Different from traditional auto-cascade cycle (ARC), additional recuperator and expansion valve are set between condenser and separator to realize phase separation at an intermediate pressure. The MRC can significantly improve volumetric refrigeration capacity (qev) and the coefficient of performance (COP) especially in low evaporating temperature condition. As evaporating temperature is set at −60°C, using MRC system can acquire 18% and 35% COP and qev improvements, and the compression ratio in MRC reduced 23% in comparison to ARC. In general, decreasing both separating temperature and quality of condenser outlet will benefit the performance of MRC. Besides, there exist an appropriate mixture quality at evaporator outlet to obtain the best COP and qev under the given condition.