Second Law Analysis of Auto Cascade Refrigeration Cycle Using Mixed Hydrocarbon Refrigerant R-600a /R-290/ R170

Abstract

Experimental and theoretical analysis investigations are achieved on the performance of the three-stage auto cascade refrigeration system. Energy and exergy analysis of auto cascade system is considered using zeotropic mixed hydrocarbon refrigerant R-600a/R-290/R-170 at different mass fractions of (25.5/42.5/32), (24.25/42.75/33), (23/43/34) and (20.5/43.5/36) %. The experimental work was performed on test rig for three stages auto cascade refrigeration system of one ton capacity which is designed and constructed for the present study. The theoretical analysis was carried out using a simulation software PROII based on EES and REFPROP software. The investigated results of the mixed refrigerant R600a/R-290/R170 have showed an enhancement in COP and cycle capacity by about 12.39% and 15% respectively, and the evaporator temperature of the system has approached a relatively lower value of -60.3°Cat mass fraction (23/43/34) compared to the average value of the other mass ratios. The higher values of the exergy efficiency observed for the condenser, evaporator and compressor were 0.92, 0.87 and 0.7 respectively. Comparison of the auto-cascade performance with R-600a/R-290/R-170 at mass fraction (23/43/34) has displayed an enhancement around 45.3 % in the cycle capacity and 39% reduction in the evaporator temperature compared to the mixed refrigerant R-134a/R-410A at mass fraction (70/30). The theoretical results have displayed a reasonable agreement compared to the experimental results with deviations 33%, 22%, and 18% in COP, cycle capacity and overall exergy efficiency respectively.