Performance assessment of a low-grade heat driven dual ejector vapour compression refrigeration cycle

In the present study, an ejector expansion refrigeration cycle is modified by placing a low-grade heat driven ejector between the compressor exit and the condenser inlet to reduce the secondary energy consumption. This modified cycle is designated as dual ejector vapour compression refrigeration cycle. The condenser temperature is assumed to be 308 K. R32 and R1234yf are considered as working fluids due to their lower global warming potentials and lesser flammability compared to hydrocarbons. The result indicates that for each of the considered working fluids, there is an optimum compressor pressure ratio corresponding to which mechanical COP (Coefficient of performance) is a maximum. It is observed that using combinations of the heat driven ejector and the compressor, mechanical COPs are 25.7% and 37.2% higher compared to those of ejector expansion refrigeration cycles operating with R32 and R1234yf respectively for an evaporator temperature of 263 K. Corresponding heater exit temperatures are found to be 338 K (for R32) and 348 K (for R1234yf). Mechanical COP of the proposed dual ejector cycle is also higher than that of the vapour compression cycle operating with single heat driven ejector.