Comparison and analysis on multi-objectives of cascade refrigeration system using CO2 as low temperature cycle refrigerant.

In this paper, based on the thermodynamics, economy and environment cascade refrigeration systems of R290, R32, R717 and R404A as high-temperature cycle refrigerant respectively, CO2 as low-temperature cycle refrigerant are compared and analyzed in multiple target. It is concluded that, under the same conditions, the cascade refrigeration system using R717 as high-temperature circuit refrigerant has higher thermal efficiency, better economy and more friendly environment compared to the other three cascade refrigeration systems. R290 / CO2 and R32/CO2 cascade refrigeration systems have similar thermal efficiency and friendly environment, but the R290 / CO2 cascade refrigeration system has better economy. The coefficient of performance, economyand environment of the R404A / CO2 cascade refrigeration system compared with that of the R717/CO2 , R290 / CO2 and R32 / CO2 cascade refrigeration system respectively decreace by14.1%, 7.5%, 13.7%, 8.0%, 5.0%, 7.8% and 6.6%, 4.4%, 6.8%.