Discussion
The power required for the compressor in kW is
Answer: C
The compressor needs about 7.9 kW.
Compression is isentropic, so the exit entropy equals the inlet entropy sg at 120 kPa, 0.95 kJ/kg.K. At 800 kPa this matches the superheated entry, where h = 276.45 kJ/kg:
\[ \begin{aligned} W &= \dot{m}(h_{2}-h_{1}) \\ &= 0.2(276.45-237) = 7.89\ \text{kW} \end{aligned} \]
Taking the exit as saturated vapour at 800 kPa (267.3) gives 6.1 kW, which is not offered and ignores the superheat. 39.5 forgets the mass flow rate of 0.2 kg/s (39.45 kJ/kg is the specific work), and 1.83 and 5.94 do not follow from the table.
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