Project ForgeA steam power plant operates on an ideal reheat Rankine cycle. Work input to the pump is 20 kJ/kg. Work output from the HP turbine is 750 kJ/kg. Work output from the LP turbine is 1500 kJ/kg. The thermal efficiency of the cycle is 50%. The enthalpy of saturated liquid and saturated vapour at condenser pressure are 200 kJ/kg and 2600 kJ/kg, respectively. The quality of steam at the exit of the LP turbine is ___ % (round off to the nearest integer).
Explanation
Wnet = 750+1500-20 = 2230 kJ/kg. η=Wnet/Qin ⟹ Qin=2230/0.5=4460 kJ/kg. Qout=Qin-Wnet=4460-2230=2230 kJ/kg. Condenser exit is saturated liquid, so h_exit(LP turbine)=hf+Qout=200+2230=2430 kJ/kg. Quality x=(2430-200)/(2600-200)=2230/2400≈0.929=93%.
Source: GATE ME 2021 Session 1 (ME-1) (2021)
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