Answer
$\dot{Q}=182.0\ Btu/s$
Work Step by Step
From tables A-4E to A-6E:
Inlet ($P_1=1000\ psia, T_1=900°F$): $h_1=1448.6\ kJ/kg$
Outlet ($P_2=5\ psia$, sat. vapor): $h_2=1130.7\ kJ/kg$
From the energy balance:
$\dot{m}h_1=\dot{m}h_2+\dot{W}_s+\dot{Q}$
Given $\dot{m}=45000\ lbm/h,\ \dot{W}_s=4MW=3791.5\ Btu/s$
solving for the heat loss rate: $\dot{Q}=182.0\ Btu/s$
