Irreversibility of sudden processes: Compression versus expansion in perfect gases

Abstract: We focus on the study of the processes undergone by a perfect gas when the external pressure is suddenly modified. The analysis shows that, from the second law perspective, there is a non-evident asymmetry between the processes of compression and expansion between the same pressures, which is manifested through different levels of entropy production. If the system remains in contact with a thermal reservoir during the processes this asymmetry is remarkable, since while entropy grows linearly with the relative change of pressure during the compression, the relation between those variables is logarithmic during the expansion.