An ammonia refrigerator works between -6.7°C and 26.7° C, the vapour being dry at the end of isentropic compression. There is no under-cooling of liquid ammonia and the liquid is expanded through a throttle valve after leaving the condenser. Sketch the cycle on the T-s and p-h diagram and calculate the refrigeration effect per kg of ammonia and the theoretical coefficient of performance of the unit with the help of the properties given below: Temperature, °C Enthalpy, kJ/kg Entropy, kJ/kg K Liquid Vapour Liquid Vapour -6.7 152.18 1437.03 0.6016 5.4308 26.7 307.18 1467.03 1.1515 5.0203