An ideal Rankine steam cycle modified with two closed feedwater heaters is shown below. The power cycle receives 75 kg/s of steam at the high pressure inlet to the turbine. The feedwater heater exit states for the boiler feedwater and the condensed steam are the normally assumed ideal states. The fraction of mass entering the high pressure turbine at state 5 that is extracted for the feedwater heater operating at 1400 kPa is y = 0.1446. Use the data provided in the tables given below to
(a) Determine the fraction of mass, z, that is extracted for the closed feedwater heater operating at the 245 kPa extraction pressure.
(b) Determine the required cooling water flow rate, in kg/s, to keep the cooling water temperature rise in the condenser to 10°C. Assume cp = 4.18 kJ/kg·K for cooling water.
(c) Determine the net power output and the thermal efficiency of the plant.

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Process states and selected data State P kPa h, kJ/k s, kJ/kg. K 20 2 5000 5000 5000 5000 1400 245 20 4 3900 3406 2918 2477 7.512 7.512 7.512 7.512 700 6 7 8 Saturation data v,, m/kg 0.00102 P kPa 20 245 1400 5000 h, kJ/kg 251 533 830 1154 , kJ/kg-K 7.907 7.060 6.468 5.973 0.00129 Turbine Wturb Cooling water in Condenser Cooling water out pump Steam trap Steam trap FIGURE P10-57