Thermodynamic Modeling of a Steam Power Cycle

A Rankine cycle with one closed heater and one open heater is schematically shown below. Steam leaving the boiler at 500 °C and 10 MPa (state 8) is expanded in the turbine to 7 kPa (state 11). At the location of 500 kPa (state 9) and 250 kPa (state 10), steam is extracted from the turbine to preheat the water in the open and the closed heaters, respectively. The temperature of the water at state 5 is the condensation temperature of the extracted steam at state 10, all of which condenses within the closed heater. The condensate is then throttled (state 4) through a valve to the condenser pressure. The exit flow of the open heat is saturated liquid. The isentropic efficiencies of the turbine and pumps are 92% and 72% respectively. The rate of heat transfer in the boiler is 5 MW. Determine

(a) the steam mass flow rate at state 8;

(b) the steam mass flow rate at the extraction points;

(c) the power production of the turbine;

(d) the thermal efficiency of the cycle.