# What is a thermodynamic process that is not polytropic?

In discussion under another question, it was pointed out: "Not every process is polytropic; that is just a special case when $$pV^n$$ is constant" Must have missed that in school.

What is a real life example of a non-polytropic process in a closed system (energy transfer yes, mass transfer no)?

How are non-polytropic processes simulated/calculated?