Question
In a steam power plant based on Rankine cycle, steam is initially expanded in a high-pressure turbine. The steam is then reheated in a reheated and finally expanded in a low-pressure turbine. The expansion work in the high-pressure turbine is 400 kJ/kg and in the low-pressure turbine is 850 kJ/kg, whereas the pump work is 15 kJ/kg. If the cycle efficiency is 32%, the heat rejected in the condenser is ________ kJ/kg (round off to 2 decimal places).
Answer :
Correct answer is : 2624.37
Work done in HPT, WT1 = 400 kJ/kg ,
Work done in LPT, WT2 = 850 kJ/kg
Wp = 15 kJ/kg, ηcycle = 0.32,
Heat rejected in the condenser, Qout =?
0.32 = (400 + 850 - 15) / Qin
Qin = 3859.37 kJ/kg
Efficiency is also written as:
0.32 = 1 - (Qout / Qin )
Qout = 3859.37 × 0.68
Qout = 2624.37 kJ/kg
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