Adiabatic irreversible process vs adiabatic reversible

[cianfa72]

TL;DR Summary

adiabatic irreversible vs adiabatic reversible processes between two given thermodynamic states

Hi,

consider an adiabatic irreversible process carrying a thermodynamic system from initial state A to final state B: this process is accompanied by a positive change in system entropy (call it $S_g$). Then consider a reversible process between the same initial and final system state. Such reversible process could be adiabatic itself ?

I believe not because the exceeding entropy between final and initial state (that are the same regardless the process) has to be transferred out to the surrounding by means of heat "crossing" the boundary of the system itself.

Does it make sense ? Thanks

 

[Andrew Mason]

Yes. Since $\Delta S = \int_A^B \frac{dQ_{rev}}{T}$, if ΔS > 0 then dQ_rev cannot be zero throughout: ie. there must be some heat flow during the reversible process from A to B

AM