Project ForgeA steam power cycle with regeneration uses a single open feedwater heater. The turbine is isentropic; bled steam enters the feedwater heater at state 2 (enthalpy 2800 kJ/kg), and condensate returns from the condenser at state 4 (enthalpy 175 kJ/kg, pump work negligible). The feedwater heater outlet, which is the boiler input, is state 5 (enthalpy 700 kJ/kg). The mass flow rate of steam bled from the turbine as a percentage of the total mass flow rate at the turbine inlet is
Explanation
Energy balance on the open feedwater heater, with y = bled fraction: y·h2 + (1−y)·h4 = h5. So 2800y + 175(1−y) = 700 → 2625y = 525 → y = 0.20 = 20%.
Source: GATE ME 2019 Session 1 (Set 1) (2019)
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