Answer to Question #320197 in Molecular Physics | Thermodynamics for matilda

Question

1 kg of steam at 100 bar and 370℃ expands reversibly in a perfectly thermally insulated cylinder behind a piston until the pressure is 38 bar and the steam is then dry saturated. Calculate the work done

Answer 1

$U=H-PV$

$U_1=2998.82-\frac{100*0.002416*10^5}{10^3}=2757.22 (KJ/kg)$

$U_g=2801.18-\frac{38*0.0524672*10^5}{10^3}=2601.8 (KJ/kg)$

$W=U_1-U_2=2757.22-2601.8=155.42(KJ/kg)$