Answer
a) $P_2=339\ kPa$
b) $s_{gen}=0.346\ kJ/kg.K$
Work Step by Step
a) From the energy balance:
$q_{out}=c_p(T_1-T_2)$
Given $q_{out}=1.75\ kJ/kg,\ c_p=5.1926\ kJ/kg.°C, T_1=60°C=333\ K$ we can solve for:
$T_2=59.7°C=332.7\ K$
For ideal gases:
$\Delta s_{He}=c_p\ln{\dfrac{T_2}{T_1}}-R\ln{\dfrac{P_2}{P_1}}$
With $\Delta s_{He} = 0.34\ kJ/kg.K,\ c_p=5.1926\ kJ/kg.K,\ P_1=400\ kPa,\ R=2.0769\ kJ/kg.K$
solving for $P_2=339\ kPa$
b) From the entropy balance:
$s_{gen}=\Delta s_{He}+\Delta s_{surr}=\Delta s_{He}+\dfrac{q_{out}}{T_{surr}}$
$s_{gen}=0.346\ kJ/kg.K$
