The objective of this study is to construct a computer model of a water vapor
power plant. This model will be used to calculate the state properties at all
points within the cycle. Included is an analysis of the ideal extraction
pressures based on the calculated values of net work, energy input, thermal
efficiency, moisture content, and effectiveness.
4.0 Body 4.1 Introduction System to be Analyzed Steam enters the
first turbine stage at 120 bar, 520 °C and expands in three stages to the
condenser pressure of .06 bar. Between the first and second stage, some steam is
diverted to a closed feedwater heater at P1, with saturated liquid condensate
being pumped ahead into the boiler feedwater line. The Terminal Temperature
Difference of the feedwater heater is 5°C. The rest of the steam is reheated to
500°C, and then enters the second stage of expansion. Part of the steam is
extracted between the second and third stages at P2 and fed into an open
feedwater heater operating at that pressure. Saturated liquid at P2 leaves the
open feedwater heater. The efficiencies of all pumps are 80%, and the
efficiencies of all turbines are 85%.
Throughout this report the states will be referenced as depicted above with the
numbers 1-13. The analysis of the system will involve the use of the Energy Rate
Balance to isolate the specific enthalpies and associated values of temperature,
pressure, specific volume, and steam quality. The Entropy balance equation will
be used to calculate the specific entropy at all the above noted states. Energy
Rate Balance (assume KE&PE=0) dEcv/dt = Qcv-Wcv+Smi(hi) - Sme(he)
Entropy Rate Balance dScv/dt = SQj/Tj + Smi(si) - Sme(se) + scv
For simplicity, it is assumed in all calculations that kinetic and potential
energy have a negligible effect. It is also assumed that each component in the
cycle is analyzed as a control volume at steady state; and that each control
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