Correct Answer - Option 2 : 34% and 590 kW
Concept:
The net work done by the power plant is the difference between turbine work and pump work i.e. Wnet = WT - Wp
And in other words, net work done by the power plant is the difference between heat absorbed and heat rejected, i.e. Wnet = Qs - QR
The thermal efficiency of the plant is given as, \(\eta_{th}=1-\frac{Q_R}{Q_S}\)
Calculation:
Given:
QS = 100000 kJ/min, QR = 66000 kJ/min, Wp = 1400 kJ/min
So, net work done is,
Wnet = 100000 - 66000 = 34000 kJ/min
And Turbine work, WT = Wnet + Wp
WT = 34000 + 1400 = 35400 kJ/min ⇒ \(\frac{35400}{60}=590~kW\)
Thermal efficiency,
\(\eta_{th}=1-\frac{66000}{100000}=0.34=34\)%