OPTIMIZATION OF THE MULTI-STAGE VAPOUR COMPRESSION REFRIGERATION SYSTEM USING EIGHT LOW GWP REFRIGERANTS

Abstract

This work aims to optimize a multi-stage vapour compression refrigeration system using flash inter-cooling for different refrigerants. The performance (COP) for the system is optimized based on the evaporation temperature (𝑇𝑒 ), condensation temperature (𝑇𝑐), sub-cooling parameter (a), and de-superheating parameter (de). Eight low GWP and zero ODP refrigerants (R717, R32, R152a, R290, R41, R600a, R134a, and R1234ze(E)) are analysed for optimization at different operating conditions. Modelling of the system is accomplished using EES software. The conjugate direction method, which is generally known as the direct search method, is used to optimize the COP of the system. Research suggests that increasing the parameter “a” increases the system's COP. R717 performs better than other refrigerants with a maximum COP of 6.199, followed by R152a with a maximum COP of 6.155 for 𝑇𝑒𝑣𝑎𝑝 = 0 °𝐶, 𝑇𝑐𝑜𝑛𝑑 = 45 °𝐶, a = 1, and de = 1. When the de-superheating parameter increases, the performance of the refrigerants R717, R32, and R152a increases, R1234ze(E) and R600a show a negligible change in COP, and the rest of the refrigerants show adverse effects, i.e., COP decreases with an increase in the de superheating parameter. The capital cost and the environmental effect are also calculated and the result shows that after optimization the total capital cost is increased and the average TEWI factor for all the eight refrigerants decreased by 40%.