EXTENDED IRREVERSIBLE THERMODYNAMICS BEYOND THE LINEAR REGIME - A CRITICAL OVERVIEW

This paper is devoted to a discussion of some thermodynamical aspects of non-equilibrium phenomena. Linear Irreversible Thermodynamics (LIT), which successfully accounts for irreversible processes occurring near the equilibrium states of a system fails beyond certain limits. Such limits are quantitatively examined in the case of several specific systems. Although it is difficult to conceive a general method capable of generating a parameter which clearly indicates the limit of validity of LIT for a given process, a general methodology does emerge from this analysis. Some attempts set forth during the last decade to cope with such phenomena generically known as Extended Irreversible Thermodynamics are critically examined and compared with other approaches such as Rational Thermodynamics, the Thermodynamics of Internal Variables and the Wave Approach to Thermodynamics. Emphasis is laid on the conceptual frame underlying these efforts trying to clarify their mutual agreement, where there exists, as well as the significant differences among them. The main conclusion of this review is that the extension of LIT to produce a unique theory capable of describing non-linear effects in irreversible processes is still far from being accomplished.