3 - Fundamentals of nonequilibrium thermodynamics

Abstract

This chapter outlines the principles of nonequilibrium thermodynamics for systems not far from global equilibrium. In this region, the transport and rate equations are expressed in linear forms, and the Onsager reciprocal relations are valid. Therefore, sometimes this region is called the linear or Onsager region and the formulations are based on linear nonequilibrium thermodynamics theory. In this region, instead of thermodynamic potentials and entropy, a new property called entropy production appears. The formulation of linear nonequilibrium thermodynamics has proven to be valid and useful for a wide range of transport and rate processes of physical, chemical, and biological systems. A local thermodynamic state is determined as elementary volumes at individual points for a nonequilibrium system. These volumes are small such that the substance in them can be treated as homogeneous and contain a sufficient number of molecules for the phenomenological laws to be applicable. This local state shows microscopic reversibility that is the symmetry of all mechanical equations of motion of individual particles with respect to time. Onsager's derivation of the reciprocal rules is based on the assumption of microscopic reversibility.