Comparative Performance Study of Autocascade and Cascade Refrigeration Systems Using Working Fluid Pair R23/R507A

Thermodynamic analysis has been carried out on an Autocascade refrigeration system (ACS) and its performance is compared with that of a Cascade refrigeration system (CS) in this present paper. An ozone-friendly refrigerant mixture of R23 and R507A is considered as working fluid for ACS; whereas R23 in low-temperature circuits and R507A in the high-temperature circuit are considered for CS. The temperature range considered for performance evaluation is from − 80 to – 40 °C. This consideration is based upon the normal boiling point of low boiling refrigerant and permissible compression ratio. The results of the analysis show that the rate of decrease in compression ratio for CS is not as fast as that of the ACS because of the little variation of intermediate pressure of CS with an increase in evaporator temperature. The performance of CS is found to be better at a lower evaporator temperature and ACS performance outweighs that of CS at an evaporator temperature of – 55 °C. This crossover temperature will be different for other working fluid pairs.