Thermodynamic systems analysis—I. A graph-theoretic approach

An analysis of thermodynamic systems using the porcess graph model is presented in this paper. The process graph model is a linear-graph representation of systems undergoing thermodynamic processes. It provides a concise model of the interconnections and interaction interfaces of a thermodynamic system with respect to all types of flows. The analysis procedure accounts for all types of work, heat flow, and their interactions in a unified manner. The modelling and analysis procedures are illustrated by examples.The relation between the postulates of system theory and the laws of thermodynamics are stated as theorems. The first and second law analyses in thermodynamics are shown to be direct applications of network postulates from system theory. Appropriate system variables, namely, energy flow and exergy factors are introduced, which are shown to correspond to through and across variables, respectively.