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Steam enters a well insulated turbine and expands isentropically throughout. At an intermediate pressure, 20 percent of the mass is extracted for process heating and the remaining steam expands isentropically to 9 kPa.
Inlet to turbine: P = 14 MPa, T = 560°C,
h = 3486 kJ/kg, s = 6.6 kJ/(kgK)
Intermediate stage: h = 276 kJ/kg
Exit of turbine: P = 9 kPa, hf = 174 kJ/kg,
hg = 2574 kJ/kg, sf = 0.6 kJ/(kgK), sg = 8.1 kJ/(kgK)
If the flow rate of steam entering the turbine is 100 kg/s, then the work output (in MW) is____.
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- 125MW
- 125.56 MW
- 129.56 MW
- 525.56 MW
Correct Option: B
h1 = 3486 kJ/kg
h2 = 2776 kJ/kg
s1 = s3 = 6.6
6.6 = .6 + x(0.1 – .6)
x = 0.8 
= 2094 kJ/kg
w = (3486 – 2776) + .8 (2776 – 2094)
= 1255.6 kJ/kg = 125.56 MW
