Project ForgeFor the same refrigerator described above (R-134a ideal vapor compression cycle, 120 kPa to 800 kPa, saturated vapor into the compressor, saturated liquid out of the condenser, ṁ=0.2 kg/s, with the isentropic compression from s1=0.95 kJ/kg.K at 120 kPa landing exactly on the given superheated-table state at 800 kPa/40°C where s=0.95 kJ/kg.K, h=276.45 kJ/kg), the power required for the compressor in kW is
- A5.94
- B1.83
- 7.9
- D39.5
Explanation
State 2 (compressor exit) is found by isentropic compression: s2=s1=0.95 kJ/kg.K, which exactly matches the given superheated-table entry at 800 kPa, 40°C — so h2=276.45 kJ/kg directly, no interpolation needed. Compressor power = ṁ(h2−h1) = 0.2×(276.45−237) = 0.2×39.45 = 7.89 ≈ 7.9 kW.
Source: GATE ME 2012 (Booklet Code A) (2012)
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