Analysis of a Vapor Power Plant

8/20/96

ME1361 Thermo II

3.0 Abstract

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 ÃÂ°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 5ÃÂ°C. The rest of the steam is reheated to 500ÃÂ°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...