Question

An existing steam turbine operating on a reheat Rankine cycle in which the first stage turbine has an inlet pressure of 12.5MPa and inlet temperature of 550 degree celcius. The second stage has an inlet temperature of 500 degree celcius. Assuming both turbines and water pump run at 100% isentropic efficiency. The steam leaves the condenser as saturated liquid at 15kPa.

Based on the set up above, the engineer decides to add an open feedwater heater (FWH) to the reheat steam turbine cycle itself. Steam enters low pressure turbine 1 (LT1) at the reheater pressure of 3.40MPa and expands to 0.8 MPa. A fraction of the steam then enters the open feedwater heater (operating at 0.8 MPa), and the mixture leaves the FWH as saturated liquid. All other operating conditions remain the same as before adding up the FWH.

HT LT1 U LT2 LT1 Reheat 6 9 Boiler Open PWH Condenser

1. Draw the T-s diagram for this steam power plant. (1 pts)
2. The fraction of steam extracted to the FWH. (2 pts)
3. The thermal efficiency of the cycle. Compare your calculation with the thermal efficiency in Part A and discuss the difference. (1 pts)
4. The total mass flow rate (kg/h) of steam in the cycle, if a net power output of 150 MW is to be achieved. (1 pts)

Answer 1