GATE 2018 ME (ME2) – Question 53
A standard vapour-compression refrigerator condenses at 35°C and evaporates at −10°C, providing 15 kW cooling. Its pressure–enthalpy diagram is shown. Compressor isentropic efficiency is 0.75. Find compressor power (kW), to two decimal places.
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Correct answer: 9.50 to 10.50
Explanation
Evaporator enthalpy rise is $400-250=150$ kJ/kg. Refrigerant mass flow is $15/150=0.1$ kg/s. Isentropic compressor work is $475-400=75$ kJ/kg; actual work is $75/0.75=100$ kJ/kg. Required power is $0.1(100)=$ **10.00 kW**.