Consider a cogeneration plant Steam enters the turbine at 9 MPa and 600 C. Some steam is extracted from the turbine at 500 kPa for process heating The remaining steam continues to expand to 7.5 kPa. Steam is then condensed at constant pressure and pumped to the boiler pressure of 9 MPa. At times of high demand for process heat, some steam leaving the boiler is throttled to 500 kPa and is routed to the process heater. The extraction fractions are adjusted so that steam leaves the process heater as a saturated liquid at 500 kPa. It is subsequently pumped to 9 MPa. The mass flow rate of steam through the boiler is 15 kg/s. Disregarding any pressure drops and heat losses in the piping and assuming the turbine and the pump to be isentropic, determine (a) the maximum rate at which process heat can be supplied, (b) the power produced, and the utilization factor when no process heat is supplied, and (c) the rate of process heat supply when 10 percent of the steam is extracted before it enters the turbine and 70 percent of the steam is extracted from the turbine at 500 kPa for process heating.

Draw the schematic and T-S diagrams.

1. Enthalpy at points 1, 2, 3 in kJ/kg =
2. Enthalpy at point 4 in kJ/kg =
3. Enthalpy at point 5 in kJ/kg =
4. Enthalpy at point 6 in kJ/kg =
5. Enthalpy at point 7 in kJ/kg =
6. Enthalpy at point 8 in kJ/kg =
7. Enthalpy at point 9 in kJ/kg =
8. Enthalpy at point 10 in kJ/kg =
9. (a) Maximum rate at process heater in kW =
10. Pump Work at Q_p=0 in kW =
11. Turbine Work at Q_p=0 in kW =
12. (b) Net Work at Q_p=0 in kW =
13. Utilization factor at Q_p=0 (%) =
14. (c) Q_p at given steam extraction in kW =