Saturated steam at 125 kpa is compressed adiabatically in a centrifugal compressor to 700 kpa at the rate of 2.5 kg⋅s-1. the compressor efficiency is 78%. what is the power requirement of the compressor and what are the enthalpy and entropy of the steam in its final state

M° = 2.5 kg/sec

For saturated steam tables

at p₁ = 125Kpa

hg = h₁ = 2685.2 KJ/kg

SQ = s₁ = 7.2847 KJ/kg-k

for isotopic compression

S₁ = S₂ = 7.2847 KJ/kg-k

at 700Kpa steam with S = 7.2847

h₂ 3051.3 KJ/kg

Compressor efficiency

h = 0.78

0.78 = h₂ - h₁/h₂-h₁

0.78 = h₂-h₁ → 0.78 = 3051.3 - 2685.2/h₂ - 2685.2

h₂ = 3154.6KJ/kg

at 700Kpa with 3154.6 KJ/kg

enthalpy gives

entropy S₂ = 7.4586 KJ/kg-k

Work = m (h₂ - h₁) = 2.5 (3154.6 - 2685.2

W = 1173.5KW