Thermo-economic analysis and multi-objective optimization of vapour cascade refrigeration system using different refrigerant combinations

Abstract

A numerical investigation of energetic, exergetic, economic and environmental performances of a 50-kW cooling capacity cascade refrigeration system using four different refrigerant pairs, namely R41–R404A, R170–R404A, R41–R161 and R170–R161, has been carried out. Effects of evaporator temperature, condenser temperature, LTC condenser temperature and cascade condenser temperature difference have been studied parametrically. The COP and exergetic efficiency of the system are found to be maximum with R41–R161 refrigerant pair followed by R170–R161 for the same operating conditions. Genetic algorithm technique has been employed to carry out multi-objective optimization for the cascade refrigeration system using above-mentioned four refrigerant pairs to evaluate the optimal performances (for maximizing exergetic efficiency and minimizing the total plant cost rate) and the corresponding operating conditions. A set of non-dominated solutions have been obtained from the optimization, and then, TOPSIS method is employed to get the unique solutions for all four investigated refrigerant pairs. Better results in terms of optimum exergetic efficiency and the total plant cost rate are obtained using R41–R161 and R170–R161 refrigerant pairs compared to those obtained using R41–R404A pair.