Project ForgeSteam 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/(kg.K). Intermediate stage: h=2776 kJ/kg. Exit of turbine: P=9 kPa, hf=174 kJ/kg, hg=2574 kJ/kg, sf=0.6 kJ/(kg.K), sg=8.1 kJ/(kg.K). If the flow rate of steam entering the turbine is 100 kg/s, then the work output (in MW) is __________.
Explanation
HP-stage work (full 100 kg/s down to the extraction point) = 100×(3486−2776) = 71,000 kW = 71 MW. At the extraction point s=6.6 kJ/kg-K (isentropic throughout); at exit (9 kPa), quality x=(6.6−0.6)/(8.1−0.6)=6.0/7.5=0.8, so h_exit=174+0.8×(2574−174)=174+1920=2094 kJ/kg. LP-stage work (remaining 80 kg/s) = 80×(2776−2094) = 54,560 kW = 54.56 MW. Total work = 71+54.56 = 125.56 MW.
Source: GATE ME 2015 (Session 1) (2015)
This question is part of a 15-day revision cycle — sign in and Project Forge will bring it back the day before you'd forget it.