Modeling Thermodynamic Systems using Bond Graphs

Bond graphs enable the modeler to describe the dynamics of a physical system in a modular fashion using energy storage, dissipative power flow, energy source, and transformation elements. The basic bond-graphic icon library enables the user to model, in a systematic fashion, physical systems, the dynamic behavior of which is governed by power flows alone. Systems with macroscopic mass flows add additional complexity to the modeling task, since the mass that flows through the system carries with it its stored internal free energy, which is thus transported from one location to another in a non-dissipative fashion. In the most general sense, thermodynamics ought to be described by distributed parameter models. Since bond graphs are geared to be used for the description of lumped parameter models only, a simplifying assumption will be made, in that the system to be modeled is compartmentalized, whereby each compartment is considered to be homogeneous. This work introduced new bond-graphic macro-elements to describe the energy storage within a compartment as well as the mass (and energy) flows between neighboring compartments and phase changes within one compartment. Several examples were done, e.g. a pressure cooker, Biosphere II. Latest work dealt with chemical reactions.

Bondgraphen in der Thermodynamik

Bondgraphen bilden eine Methodik, Energieströme und -potentiale über beliebige Systemgrenzen hinweg zu beschreiben. Leider wurde die Thermodynamik aufgrund ihrer Komplexität auf einzelne Phänomene, wie beispielsweise Reibungswärme, begrenzt. Erst durch die Einführung von mehrdimensionalen Bondstrukturen und gekoppelten, aber in sich homogenen Parzellen, gelang es, thermodynamische Prozesse wie Konduktion, Stoffströme, Druckausgleich und seit kurzem selbst chemische Reaktionen in Gänze zu beschreiben.