Simulation software for thermodynamic models, part 1

Abstract

The extensive software available for simulating systems modeled by standard bond graphs does not address most thermodynamic systems, because they are not modeled effectively by those graphs. The convection bond graphs which do address those systems have not previously been implemented by generic simulation software. The complexities inherent in these bond graphs make the development of such software quite challenging; heretofore differential equations for each model have been written on an ad hoc basis from the bond graphs. Free downloadable software is described herein that deduces, organizes and executes differential equations for most convection and hybrid bond graphs, thereby simulating the unsteady behavior of lumped models that represent hybrid thermodynamic, mechanical, electrical and hydraulic systems. The imbedded computation of the thermodynamic properties of any of thirty-six different single or multiphase substances is generally accurate and efficient, requiring virtually no iteration. The user enters the bond graph largely through the use of two matrices; a graphical interface could be developed. Examples given include a steam catapult and a rock drill driven by compressed wet air. The inclusion of fluid kinetic energy and overall conclusions are made in part 2 of the paper.