Numerical Simulation of Vapor-Liquid Equilibria of a Water-Ethanol Mixture

Vapor-liquid equilibrium studies are important to many engineering disciplines. Numerical simulations using empirical equations of state provide an excellent alternative to time consuming experimental measurement. A new methodology is developed to visualize the results from vapor-liquid equilibrium numerical studies of an aqueous alcohol binary mixture. The goal is to provide a better technique to determine the cubic equation of state, mixing rule, and combining rule combinations that will improve the predictability of the simulations, by reducing their dependence on binary interaction parameters. With an improved understanding of the various equations used in vapor-liquid equilibrium models, simulations can be more reliably used to predict data under conditions in which experimental data are unavailable or not easily obtainable. A vapor-liquid equilibrium simulation program is developed that can model fluid mixtures with assorted equation of state, mixing rule, and combining rule blends. A model's success is appraised via both convergence and performance metrics over large ranges of binary interaction pairs. It is shown that increases in equation complexity typically lead to improved correlative accuracy. However, models that converge for large numbers of pairs, and do so with good performance, are chosen as the most predictive combinations due to their ability to reproduce data even with a lack of decent binary interaction parameters. Furthermore, the relationships between the binary interaction pairs are examined. For the arithmetic and conventional combining rules, it is observed that only one experimental fitting parameter is required, for the system under consideration. Using the designed flexibility of this model, other equations and systems can be incorporated in the future, leading to the development of enhanced mixing and combining rules that are linked to specific equations of state, which increase the predictability, and consequently the usability, of the equations