Q7 : A cascade refrigeration system is designed to supply 10tonnes of refrigeration at an evaporator temperature of -40°C and acondenser temperature of 36°C. The load at -40°C is absorbed by aunit using R-22 as the refrigerant and is rejected to a cascadecondenser at -10°C. The cascade condenser is cooled by a unit usingR-12 as the refrigerant and operating between - 20°C evaporatingtemperature and 36°C condenser temperature. The refrigerant leavingthe R-22 condenser is subcooled by 6°C but there is no subcoolingof R-12 refrigerant. The gas leaving both the evaporators is dryand saturated and the compressions are isentropic. Neglectinglosses. calculate the COP of whole system
