On the role of external and internal irreversibilities towards classical entropy generation predictions in equilibrium thermodynamics and their relationship with heat transfer

Abstract

In classical equilibrium thermodynamics description, ambiguities exist in terms of pinpointing external and internal irreversibilities in overall entropy generation prediction, as a system undergoes a thermodynamic process. The present work attempts to bridge this gap between classical thermodynamics-based irreversibility predictions and finite time heat transfer analysis. By choosing a model problem, expressions for external irreversibilities are quantitatively derived and it is observed that ambiguities may exist in the pertinent quantification depending on the very definition of system, immediate surroundings and surroundings. It is observed that if variations within immediate surroundings are taken into account, more realistic estimates of external irreversibilities can be obtained in equilibrium thermodynamics framework, as a function of heat transfer characteristics of the same. It is also shown that for some special cases, different expressions for external irreversibilities asymptotically converge to the same entropy generation predictions, in effect.