Answer
$\dot{m}_2=0.107\ kg/s$
Work Step by Step
From tables A-4 to A-6:
Inlet 1 ($T_1=20°C$): $h_1=83.91\ kJ/kg$
Inlet 2 ($P_2=300\ kPa, T_2=300°C$): $h_2=3069.6\ kJ/kg$
Outlet ($P_3=300\ kPa, T_3=60°C$): $h_3=251.18.2\ kJ/kg$
From the energy balance:
$\dot{m}_1h_1+\dot{m}_2h_2=\dot{m}_3h_3=(\dot{m}_1+\dot{m}_2)h_3$
Given $\dot{m}_1=1.8\ kg/s$:
$\dot{m}_2=0.107\ kg/s$
