Optimization of a multistage vapor-compression refrigeration system for various refrigerants

This work focuses on theoretical investigation of the performance of a multistage vapor-compression refrigeration system using energy, exergy and economic analysis. The system was modeled using Engineering Equation Solver (EES) software and the model was validated against published data with maximum error of 1.14%. System optimization was carried out using Conjugate Directions Method. Optimization objective function was maximizing the coefficient of performance (COP) of the multistage vapor-compression refrigeration system by varying four optimization variables. Those variables are sub-cooling, de-superheating parameters, and evaporator and condenser temperatures of the system. Eight refrigerants were used in the investigation. They are: R717, R22, R134a, R1234yf, R1234ze(E), R410A, R404A, and R407C. Results show that COP increases with increasing the sub-cooling parameter. The maximum COP of 6.17 was achieved with ammonia while minimum COP of 4.95 was achieved with R407C. The optimization results give also that, R717 is a best option compared with all refrigerants, while R407C is not recommended to use.