Entropieerzeugende Prozesse an Phasengrenzflächen

Abstract

AbstractA thermodynamic theory for the treatment of transport phenomena in multiphase and multicomponent systems is presented. Starting point is a field theoretical description of interfacial systems. The interface in its three dimensional structure is described by new thermodynamic variables, namely the structure vectors ak of the components k. This offers the possibility to analyse processes related with a change of the three dimensional structure by means of the methods of irreversible thermodynamics. Compared to the well known theory of irreversible processes in single phase and membrane systems there are differences regarding the balance equations for component masses and momentum; additionally a balance equation for the structure vector has to be introduced to treat changes of the interfacial structure. The linear constitutive equations obtained from the production term of the entropy balance equation describe transport processes at every point of a multiphase system.—It is shown that in the interfacial region of multiphase systems there are other processes producing entropy than in the bulk of a single phase system. E. g. in the region of an interface Fickian diffusion is not allowed to occur due to a stability criterion. Instead of this a tensorial transport phenomenon due to the structural change of the interface sets in which is possible only at interfaces. By means of a thermodynamic coupling of this tensorial process with the tensorial momentum transport a thermodynamic explanation and description of the Marangoni‐effect is obtained.—New expressions for entropy producing processes are also derived for generalized chemical reactions and transport of momentum. A discussion of potential interactions between fluxes shows that the same cross‐effects occurring in single phase systems cannot be supposed to occur in an interfacial region roo. This results in new aspects for the thermodynamic explanation of active transport.