Question

Nitrogen at 600 kPa, 127°C is in a 0.5 m3 insulated tank connected to a pipe with a valve to a second insulated initially empty tank of volume 0.5 m3, The valve is opened and the nitrogen fills both tanks at a uniform state. Find the final pressure and temperature and the entropy generation this process causes. Why is the process irreversible?

Answer 1

CV Both tanks + pipe + valve Insulated : Q = 0 Rigid: W = 0

Energy Eq m(u2 - u1) = 0 - 0

=> u2 = u1 = ua1

Entropy Eq m(s2 − s1) = ∫ dQ/T + 1S2 gen

= 1S2 gen (dQ = 0)

1 P1 , T1 , Va => m = PV/RT = (600 × 0.5)/ (0.2968 × 400) = 2 .527

2 V2 = Va + Vb ; uniform state v2 = V2 / m ; u2 = ua1

Irreversible due to unrestrained expansion in valve P ↓ but no work out.