Project ForgeIn an ideal Rankine cycle, superheated steam enters the turbine at 3 MPa, 350°C, and the condenser pressure is 75 kPa. Given hf=384.39 kJ/kg, vf=0.001037 m³/kg, sf=1.213 kJ/kg-K, hfg=2278.6 kJ/kg, sfg=6.2434 kJ/kg-K at 75 kPa, and h=3115.3 kJ/kg, s=6.7428 kJ/kg-K at the turbine inlet, the thermal efficiency of the cycle (in percent) is __________.
Explanation
Isentropic expansion: x4=(6.7428-1.213)/6.2434≈0.886, h4=384.39+0.886×2278.6≈2402.7 kJ/kg. Pump work wp=vf(p1-p2)=0.001037×2925≈3.03 kJ/kg, h2=384.39+3.03=387.42 kJ/kg. Wnet=(h3-h4)-wp=(3115.3-2402.7)-3.03≈709.6 kJ/kg. Qin=h3-h2=3115.3-387.42≈2727.9 kJ/kg. η=Wnet/Qin≈26.0%.
Source: GATE ME 2016 Set-1 (2016)
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.