Answer
a) $T_2=179.9°C$, $\dot{W}_s=1616\ kW$
b) $T_2=151.8°C,\ \dot{W}_s=2134\ kW$
c) $T_2=99.6°C,\ \dot{W}_s=2333\ kW$
d) $T_2=81.3°C,\ \dot{W}_s=2173\ kW$
Work Step by Step
From table A-6:
Flash inlet ($x_1=0, T_1=230°C$): $h_1=990.14\ kJ/kg$
Sep.inlet ($P_2=1\ MPa, h_2=h_1$): $x_2=0.113,\ T_2=179.9°C$
Turb. inlet ($P_3=1\ MPa, x_3=1$): $h_3=2777.1\ kJ/kg$
Turb. outlet ($P_4=20\ kPa, x_4=0.95$): $h_4=2491.1\ kJ/kg$
$\dot{m}_3=x_2\dot{m}_1,\ \dot{m}_1=50\ kg/s$
$\dot{m}_3=5.649\ kg/s$
$\dot{W}_s=\dot{m}_3(h_3-h_4)$
$\dot{W}_s=1616\ kW$
Repeating the procedure for:
$P_2=500\ kPa$: $T_2=151.8°C,\ \dot{W}_s=2134\ kW$
$P_2=100\ kPa$: $T_2=99.6°C,\ \dot{W}_s=2333\ kW$
$P_2=50\ kPa$: $T_2=81.3°C,\ \dot{W}_s=2173\ kW$
