An ideal vapour compression refrigerator using Freon-12 operates between temperature limits of –10° C and 40oC. The refrigerant leaves the condenser dry saturated. The rate of flow of refrigerant through the unit is 150 kg/hr.
Calculate the refrigerating effect per kg of refrigerant, the coefficient of performance and the capacity of the plant if,
(i) the refrigerant leaves the condenser dry saturated as stated.
(ii) the refrigerant is sub cooled to 20° C before throttling.
Assume that the enthalpy of refrigerant before throttling is approximately equal to the enthalpy of liquid refrigerant at under-cooled temperature of 20° C and take it as hf = 50.59 kJ/kg. Give your comments on the result. Solve the problem by using tables.
Take (cpv)at condenser pressure = 0.76 kJ/kg.K