Question

Nitrogen at 90 lbf/in.2, 260 F is in a 20 ft3 insulated tank connected to a pipe with a valve to a second insulated initially empty tank of volume 20 ft3. The valve is opened and the nitrogen fills both tanks. Find the final pressure and temperature and the entropy generation this process causes. Why is the process irreversible?

Answer 1

C.V. Both tanks + pipe + valve. Insulated : Q = 0, Rigid: W = 0

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

If not a uniform final state then flow until P2b = P2a and valve is closed.

Assume no Q between A and B

Now we must assume ma2 went through rev adiabatic expansion