Performance of a single-stage auto-cascade refrigerator operating with a rectifying column at the temperature level of −60 °C

This paper proposes a new approach to the performance optimization of an auto-cascade refrigerator (ACR) operating with a rectifying column and six types of binary refrigerants (R23/R134a, R23/R227ea, R23/R236fa, R170/R290, R170/R600a, and R170/R600) at a temperature level of −60 °C. Half of the six binary refrigerants are nonflammable, of which the 0.5 and the 0.6 mole fractions of R23 for the R23/R236fa possess the most prospective composition for the medium and low suction pressure compressors, respectively. The remaining three binary refrigerants are flammable but with low global warming potentials, of which the 0.6 mole fraction of R170 for the R170/R600 is the most prospective one. The results show that the overall matching as well as local matching of heat capacity rates of hot and cold refrigerants in the recuperators are important for the improvement of coefficient of performance of the cycle, which can be adjusted through the simultaneous optimization of the pressure level and composition. The new approach proposed also offers a wider range of applications to the optimization in performance of the cycle using multi-component refrigerants.