The IGE Model: An Extension of the Ideal Gas Model to Include Chemical Composition as Part of the Equilibrium State

Abstract

The TEST (The Expert System for Thermodynamics, www.thermofluids.net) web portal is a comprehensive thermodynamic courseware consisting of multimedia problems and examples, an online solution manual for educators, traditional thermodynamic charts and tables, fifteen chapters of animations to illustrate thermodynamic systems and fundamental concepts, and a suite of thermodynamic calculators called daemons for evaluating thermodynamic properties and analyzing thermodynamic problems.. The state module offers Java applets for evaluation of thermodynamic states of different working substances grouped into several material models according to underlying assumptions. Gas mixtures are modeled by the perfect gas (PG) or ideal gas (IG) mixture models. In this work, we extend the IG model mixture model into an ideal gas equilibrium (IGE) mixture model by incorporating chemical equilibrium calculations as part of the state evaluation process. Through a simple graphical interface users can set the atomic composition of a gas mixture. In the state panel, the known thermodynamic properties are entered. For a given pressure and temperature, the mixture’s Gibbs function is minimized subject to atomic constraints and the equilibrium composition along with thermodynamic properties of the mixture are calculated and displayed. What is unique about this approach is that equilibrium computations are performed in the background, without requiring any major change in the familiar user interface used in other state daemons. Properties calculated by this equilibrium state daemon are compared with results from other established applications such as NASA CEA and STANJAN. Also, two different algorithms, an iterative approach and a direct approach based on minimizing different thermodynamic functions in different situation are compared.