Adiabatic irreversible process vs adiabatic reversible

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SUMMARY

An adiabatic irreversible process results in a positive change in system entropy (denoted as ##S_g##) when transitioning from initial state A to final state B. In contrast, a reversible adiabatic process cannot occur without heat transfer, as the entropy change (ΔS) must be accounted for. The discussion confirms that for ΔS to be greater than zero, heat flow (dQrev) must occur during the reversible process, contradicting the definition of an adiabatic process where no heat is exchanged.

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

AM
 
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