Problem 3. Water is the working fluid in a regenerative Rankine cycle. Superheated vapor enters the turbine at 80 bar, 480°C, and the condenser pressure is 0.1 bar. Steam expands through the first-stage turbine to 5 bar where some of the steam is extracted and diverted to an open feedwater heater operating at 5 bar. The remaining steam expands through the second-stage turbine to the condenser pressure of 0.1 bar. Saturated liquid exits the feedwater heater at 5 bar. Consider that the pump and each stage of turbine have an isentropic efficiency of 80% and determine for the cycle
(a) the heat addition, in kJ per kg of steam entering the first-stage turbine.
(b) the thermal efficiency.
[Answers: (a) 2697.93 kJ/kg, (b) 34.32%. Also, y = 0.1708, specific enthalpy at the exit of the second turbine $h_3$ = 2328.83 kJ/kg.]
