PERFORMANCE EVALUATION OF CASCADE REFRIGERATION SYSTEMS USING DIFFERENT REFRIGERANTS

Due to the negative effects of synthetic refrigerants on the environment, natural refrigerants have obtained again interest as alternative refrigerants for di®erent applications because of their zeroODP and negligible GWP. This paper presents a thermodynamic analysis of di®erent two-stage cascade refrigeration systems using as refrigerant carbon dioxide (R744) in low-temperature circuit, and, respectively, ammonia (R717), propane (R290), butane (R600), R404A, R410A and R134a in high temperature circuit. The operating parameters considered in this study include condensing and evaporating temperatures in high-temperature circuit, temperature di®erence in the cascade heat exchanger, and evaporating and condensing temperatures in the low-temperature circuit.The results obtained show that a cascade refrigeration system using natural refrigerants is an interesting alternative to systems using synthetic refrigerants for energetic, security and environmental reasons.