Why Is There Disagreement on Entropy in Irreversible Adiabatic Processes?

[Brian Curtis]

Why does there tend to be disagreement on an irreversible adiabat entropy determination? Doesn't an irreversible adiabatic expansion increase the entropy of a system by the Clausius inequality?

 

[Let'sthink]

Total entropy of an isolated system or of Universe increases when the isolated system or universe undergoes irreversible adiabatic process.

 

[Brian Curtis]

Total entropy of an isolated system or of Universe increases when the isolated system or universe undergoes irreversible adiabatic process.

That's what I've thought. It can be proved by determining entropy through a reversible cycle. However, in class, it was mentioned on an assignment that the delta S is negative and not spontaneous. Which again, does not make sense

 

[Let'sthink]

I do not understand what is meant by spontaneous but for any process the change in entropy of a system can be negative but then the change in entropy of environment will be positive and greater in magnitude of the change for system, for an irreversible process.