Modelling entropy and exergy changes during a fluid self-organization process

The possibility and the need to describe a complex system behaviour by means of functions of state variables is stressed here, yielding a detailed calculation of exergy and entropy changes within a fluid model, according to input flows of available resources. This 'from within' approach is presented as an applied example of our previous claims (Ulgiati, S., Bianciardi, C., 1997. Ecol. Model. 96, 75-89) about the relevance of measures of far-from-equilibrium states based on internal and physically measurable state variables. The system model evolution to a thermodynamic equilibrium state is described, through different conduction, convection and chaos phases. Transition from conduction to convection is carefully investigated. Results are compared with literature 'from outside' descriptions based on assumed links between internal organization and input flows from outside. (C) 1998 Elsevier Science B.V. All rights reserved.