Question

An ideal refrigerator-a Carnot engine running backwards-freezes ice-cubes at a rate of 5gs-1 starting with water at its freezing point. Energy is given off to the room which is at 30°C. The fusion energy of ice is 320Jg-1. At what rate must electrical energy be supplied as work, and at what rate is energy given off to the room

Answer 1

The rate energy is given off to the room equals to P_r = P_f/(1-η) = mλT_h/T_l = 5*320*303/273 = 1.8 (kW). The electrical energy rate P_el = P_r – P_f = 1800 – 5*320 = 200 (W).