Project ForgeCommon Data for Q48-49: In a steam power plant operating on the Rankine cycle, steam enters the turbine at 4MPa, 350°C and exits at 15kPa, then enters the condenser and exits as saturated water; a pump feeds the water back to the boiler. The adiabatic efficiency of the turbine is 90%. States: Steam at 4MPa,350°C: h=3092.5 kJ/kg, s=6.5821 kJ/kgK. Water at 15kPa: hf=225.94, hg=2599.1 kJ/kg, sf=0.7549, sg=8.0085 kJ/kgK, vf=0.001014 m³/kg. The net work output (kJ/kg) of the cycle is
- A498
- B775
- 860
- D957
Explanation
Isentropic expansion: s2s=s1=6.5821. Quality x=(6.5821-0.7549)/(8.0085-0.7549)≈0.8034. h2s=225.94+0.8034×(2599.1-225.94)≈2132.6 kJ/kg. Actual turbine work=η(h1-h2s)=0.9×(3092.5-2132.6)≈863.9 kJ/kg. Pump work=vf(P1-P2)=0.001014×(4000-15)≈4.04 kJ/kg. Net work=863.9-4.04≈860 kJ/kg.
Source: GATE ME 2010 (2010)
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