Performance Analysis of Refrigerants R1234yf, R1234ze and R134a in Ejector-Based Refrigeration Cycle

Performance enhancement of refrigeration and heat pump systems by cycle modification is an emerging research topic now-a-days to reduce the electricity consumption leading to mitigate the problems related to the environmental pollution by utility power plants. Due to no moving parts, low cost, simple structure and low maintenance requirements, the use of two-phase ejector has become a promising cycle modification recently. Use of ejector as an expansion device by replacing the throttle valve in the vapor compression refrigeration cycle seems to be one of the efficient ways to reduce the throttling losses or the expansion irreversibility in the refrigeration/heat pump cycle. Ejector also reduces the compressor work by raising the suction pressure to a level higher than that in the evaporator leading to the improvement of COP. The present work aims to evaluate the performance of an ejector based vapor compression refrigeration cycle under a wide range of operating conditions. Two newly proposed refrigerants i.e., R1234yf and R1234ze, and commonly used refrigerant R134a are considered for simulation and a comparative study has been carried out. A numerical model is developed and a parametric study of important parameters such as entrainment ratio, high side pressure (condenser pressure) and evaporator temperature are analyzed for the improvement of COP of the system. Results show that the COP of the R1234ze is highest compared to R1234yf and R134a for the given evaporating and condensing temperature.