Answer
$\dot{m}=0.674\ kg/s$
Work Step by Step
From table A-17:
Inlet ($T_1=25°C$): $h_1=298.2\ kJ/kg$
Outlet ($T_2=347°C$): $h_2=628.7\ kJ/kg$
From the energy balance:
$\dot{m}(h_1+\mathcal{V}_1^2/2)+\dot{W}_s=\dot{m}(h_2+\mathcal{V}_2^2/2)+\dot{Q}$
Given $\mathcal{V}_1\approx0,\ \mathcal{V}_2=90\ m/s,\ \dot{W}_s=250\ kW,\ \dot{Q}=1500\ kJ/min$:
$\dot{m}=0.674\ kg/s$
