Question

A rigid insulated container has two rooms separated by a membrane. Room A contains 1 kg air at 200°C and room B has 1.5 kg air at 20°C, both rooms at 100 kPa. Consider two different cases

(1) Heat transfer between A and B creates a final uniform T.

(2) The membrane breaks and the air comes to a uniform state.

For both cases find the final temperature. Are the two processes reversible and different? Explain.

Answer 1

C.V. Total A+B

(1) Energy Eq.:

2) Same energy eq. Since ideal gas u(T) same T2 = 92°C, but now also same P2

Both cases irreversible 1) Q over a finite ∆T and in 2) mixing of 2 different states (internal u redistribution)

(Case 2) is more irreversible as the final state in 1 could drive a turbine between the two different pressures until equal.