Additional Problem 6.1 - Steam Power Plant for Athens, Ohio

We wish to evaluate the Steam Power Plant shown in the following diagram, which has been proposed to supply power to the Athens, Ohio region. It is to be placed east of the sewage plant on the east side of Athens (near the bike path) and cooled by water from the Hocking river. The turbine is adiabatic, operating between 10MPa, 600°C at Station (1) and 20kPa, saturated vapor at Station (2). The steam is then condensed to a saturated liquid at Station (3) and a feedwater pump pumps the liquid to 10MPa as shown. The mass flow rate of the steam is 10 kg/s. [The various numerical answers are shown in red]

• 1) Neatly sketch the complete cycle on the pressure-enthalpy P-h diagram below, indicating clearly all 4 stations on the diagram. Plot also the turbine isentropic process on the diagram.
• 2) Using steam tables, and assuming that the turbine is adiabatic, determine the power output of the turbine. [10.2 MW]
• 3) Assuming that the feedwater pump is adiabatic, and that the compressed liquid experiences no change in temperature while passing through the pump, determine the power required to drive the pump. [100 kW]
• 4) Using steam tables, determine the heat transferred to the boiler. [boiler power = 33.7 MW]
• 5) Determine the overall thermal efficiency hth of this power plant. (Thermal efficiency is defined as the net work done by the turbine divided by the heat supplied externally to the boiler). [hth = 30%]
• 6) Plot the turbine process (Stations (1) - (2)) on the enthalpy-entropy h-s "Mollier" diagram below. Plot also the equivalent isentropic turbine process (Stations (1) - (2s)) on the diagram, and indicate the actual turbine specific work as well as the isentropic turbine specific work on the h-s diagram.
• 7) Using steam tables, determine the turbine adiabatic efficiency hT. [75%]
• 8) Assume that all the heat rejected from the condenser is absorbed by cooling water from the Hocking River. To prevent thermal pollution the cooling water is not allowed to experience a temperature rise above 10°C. If the steam leaves the condenser as saturated liquid at 20 kPa, determine the required minimum volumetric flow rate of the cooling water (cubic meters/minute). [34 m3/min]