Refrigeration and Airconditioning Miscellaneous
 Refrigerant vapor enters into the compressor of a standard vapor compression cycle at –10°C (h = 402 J/kg) and leaves the compression at 50°C (h = 432 kJ/kg). It leaves the condenser at 30°C (h = 237 kJ/kg). The COP of the cycle is ________.

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Work done = 432 – 402 = 30 kJ/kg
Refrigerating effect = 402 – 237 = 165 kJ/kg.COP = 165 = 5.5 30 Correct Option: B
Work done = 432 – 402 = 30 kJ/kg
Refrigerating effect = 402 – 237 = 165 kJ/kg.COP = 165 = 5.5 30
 The power required for compressor in kW is

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Power required by compressor p = ṁ(h_{2} – h_{1})
= 0.2 (276.45 – 237) = 7.9 kWCorrect Option: C
Power required by compressor p = ṁ(h_{2} – h_{1})
= 0.2 (276.45 – 237) = 7.9 kW
 The rate at which heat is extracted, in kJ/s from the refrigerated space is

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Rate at which heat is extracted = ṁ(h_{1} – h_{4})
= 0.2 (237 – 95.5) = 28.3 kWCorrect Option: A
Rate at which heat is extracted = ṁ(h_{1} – h_{4})
= 0.2 (237 – 95.5) = 28.3 kW
 In an ideal vapour compression refrigeration cycle, the specific enthalpy of refrigerant (in kJ/kg) at the following states is given as :
Inlet of condenser : 283
Exit of condenser : 116
Exit of evaporator : 232
The COP of this cycle is

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1– 2 → work done by the compressor
2 – 3 → condenser heat rejected at constant pressure
3 – 4 → throttling
4 – 1 → heat addition in evaporator
Given: h_{2} = 283 kJ/ kg
h_{3} = 116 kJ/kg = h_{4} (from ph curve)
h_{1} = 232 kJ/kg
We knowC.O.P = desired effect = Cooling effect work input work done by compressor C.O.P = h_{1} – h_{4} = 232  116 = 2.27 h_{2} – h_{1} 283  232
Correct Option: A
1– 2 → work done by the compressor
2 – 3 → condenser heat rejected at constant pressure
3 – 4 → throttling
4 – 1 → heat addition in evaporator
Given: h_{2} = 283 kJ/ kg
h_{3} = 116 kJ/kg = h_{4} (from ph curve)
h_{1} = 232 kJ/kg
We knowC.O.P = desired effect = Cooling effect work input work done by compressor C.O.P = h_{1} – h_{4} = 232  116 = 2.27 h_{2} – h_{1} 283  232
 The vapour compression refrigeration cycle is represented as shown in the figure below, with state 1 being the exit of the evaporator. The coordinate system used in this figure is

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Th curve
Correct Option: D
Th curve