Optimum thermodynamic performance of three-stage refrigerating systems

The refrigeration efficiency, mass flows through IP and HP compressors, power input and inter-stage pressures at the optimum thermodynamic performance of three stage systems are presented graphically for the most common refrigerants, R 12, R 22 and R 717. Correlations are developed to account for the effects of subcoooing of condensate and super-heating of vapour in the evaporator, each up to 15 K. The effects of superheat up to 4 K for the vapours entering the IP and HP compressors on the system performance are also studied in order to simulate real systems more closely. The respective ranges of condensing and evaporating temperatures are taken as 273.15 to 333.15 K and 273.15 to 213.15 K, with T h − T 1 ⩾60 K.