Thermodynamics

Chapter 10 | 575The fractions of steam extracted are determined from the mass and energybalances of the feedwater heaters:Closed feedwater heater:y Open feedwater heater:The enthalpy at state 8 is determined by applying the mass and energyequations to the mixing chamber, which is assumed to be insulated:E # in E # outE # in E # outz 11 y21h 3 h 2 2h 12 h 2112h 8 11 y2h 5 yh 7 1089.8 kJ>kgE # in E # outyh 10 11 y2h 4 11 y2h 5 yh 6h 5 h 41h 10 h 6 2 1h 5 h 4 2 1087.4 643.9213155.0 1087.42 11087.4 643.922 0.1766zh 12 11 y z2h 2 11 y2h 311 0.176621640.09 192.302 0.13063014.8 192.30h 8 11 0.1766211087.42 kJ>kg 0.1766 11101.22 kJ>kg1 kg915 MPa600°CTBoilerReheater10High-PturbineLow-Pturbine15 MPa1 kg9 111 – yMixingchamber875ClosedFWHy P 10 = P 11 = 4 MPa 600°C z4 MPa641 – yOpenFWH3110.5 MPa2121 – y – z1310 kPaCondenser18 75642 31y4 MPa 100.5 MPa z10 kPa1 – y121 – y – z13sPump IIIPump IIPump IFIGURE 10–19Schematic and T-s diagram for Example 10–6.