Exergetic Port-Hamiltonian Systems: Modelling Basics

Abstract

Port-Hamiltonian systems theory provides a modular approach to modeling and potential-based control of multiphysical systems. These systems are defined based on geometric objects called Dirac structures which encode the power-conserving interconnection of different parts of a system and its environment. Complex physical systems can be expressed through composition of Dirac structures. This article shows how port-Hamiltonian theory can be applied to thermodynamic systems. Using total exergy as the Hamiltonian function, reversible and irreversible processes can be modeled on an equal footing and in accordance with the now classical theory for electro-mechanical systems. The structured representation of physical models can be used as a valuable ingredient in the exergy analysis method. Port-Hamiltonian systems are naturally passive which is an attractive property for network modeling of complex physical systems and their control. For exergetic port-Hamiltonian systems, passivity results from the first and the second law of thermodynamics being encoded as structural system properties. We use lumped-parameter examples and the bond-graph modeling language to express the key ideas.