Modeling Chemical Reactions Using Bond Graphs

摘要

This article offers a general methodology for modeling basic chemical reactions and carries forward a series of papers on modeling thermodynamic behavior using true rather than pseudo-bond graphs. In order to make processes of heating and expansion within the mixture visible, our approach does not deal with one overall volume and the overall entropy -as would be normal for classical chemistry- but rather with separated entities, one for each compound. Furthermore, assumptions of quasi-stationary or equilibrium conditions are minimized to ensure the largest possible degree of generality in the conclusions reached. It will be shown, that chemical reactions can be modeled as transformative behavior, which makes their external behavior linear and therefore allows for superposing several chemical reactions. While the mass flows (respectively molar flows) are assumed to be determined directly from Arrhenius' equation and the underlying stoichiometry, the determination of entropy and volume flow processes needed a more extensive discussion. A bondgrapher's Modelica model of the HBr-synthesis based on the assumption of ideal gas serves as an example of the presented theory of chemical reaction dynamics.