Answer
$\dot{S}_{gen}=0.1025\ kW/K$
Work Step by Step
The entropy balance for this system:
$\dot{S}_{in}-\dot{S}_{out}+\dot{S}_{gen}=\Delta \dot{S}_{sys} = 0\ \mbox{(steady state)}$
$\dot{S}_{gen}=\dot{m}(s_2-s_1)$
For the ideal gas:
$\dot{m}=\dfrac{P_1\pi D_1^2\mathcal{V}_1}{4RT_1}$
Given $P_1=240\ kPa,\ T_1=293\ K,\ R=0.2598\ kJ/kg.K,\ D_1=0.12\ m,\ \mathcal{V}_1=70\ m/s$
$\dot{m}=2.496\ kg/s$
For an ideal gas:
$s_2-s_1=c_p\ln\left(\frac{T_2}{T_1}\right)-R\ln\left(\frac{P_2}{P_1}\right)$
With $T_2=291\ K,\ c_p=0.918\ kJ/kg.K,\ P_2=200\ kPa$
$s_2-s_1=0.04108\ kJ/kg.K$
Therefore:
$\dot{S}_{gen}=0.1025\ kW/K$
