Question

5. There are 3 kg/min of steam undergoing an isothermal process from 30 bar and 350 o C

to 7 bar. (note 1 bar = 100 kPaa). Find: a) ΔS (kJ/k), b) Heat transferred (kJ), c) ΔH

(kJ), d) ΔU (kJ)

Answer 1

$Given;\\ m=3\ kg/min\\ T=350°C=623.15K\\ P_1=30 \ bar\\ P_2=7 \ bar\\ P_1/P_2=4.3$

$a.\\ ΔS=mR[ln(p1/p2)]=\\ (3\ kg/min)(0.5 kJ/(kg K))(ln4.3) =36.47 kJ/(Ksec)$

$b.\\ Q=TΔS =623.15K(36.47 kJ/(K sec)) =22.73\ MJ/sec$

$c.\\ ∆H\\ ∆H=Q=22.73\ MJ$