Extended Thermodynamics

Abstract

The basic ideas underlying Extended Irreversible Thermodynamics are reviewed. This formalism is an extension of the Classical Theory of Irreversible Thermodynamics: it consists essentially of extending the space of the state variables by including the thermodynamical fluxes, like the heat flux, the inelastic stress tensor, mass flux,... among the set of variables. As illustrations, heat conduction in a rigid body and an elastic body will be explicitly treated. The microscopic foundations of Extended Thermodynamics are discussed in the framework of the kinetic theory of gases. It is also shown that Extended Thermodynamics is particularly well suited for obtaining the constitutive equations of rheology in general and, viscoelastic materials in particular. Comparison with Classical Irreversible Thermodynamics, Rational Thermodynamics and the Internal Variable Theory will also be outlined.