Helmholtz energy, extended corresponding states and local composition model for fluid mixtures

An improved Helmholtz energy model for non-polar fluids and their mixtures. Part 1: Application to non-polar pure fluids

“…This first document is concerned with the application of such model to pure fluids whereas the second document is dedicated to the application to mixtures. This work capitalises on works reported by the author and co-workers in [1,2].…”

“…For instance, for mixtures of non-polar fluids the overall average absolute deviation (AAD) obtained with the model of [15] was 0.11 percent for densities, 0.55 percent for isobaric heat capacities and 0.20 percent for speeds of sound. Thence the rationale for the models of [1,2]: the Helmholtz energy can be given by the contribution of two terms, one is an ECS term and the other is a supplemental contribution due to different intermolecular forces between unlike species. Given that ECS models are in fact Helmholtz energy models, the desired effect is that the ECS term responds for an accurate approximation to the Helmholtz energy and thus the formulation of the correction term is arguably much simpler.…”

“…Given that ECS models are in fact Helmholtz energy models, the desired effect is that the ECS term responds for an accurate approximation to the Helmholtz energy and thus the formulation of the correction term is arguably much simpler. In the models of [1,2] the correction terms were temperature-and density-dependent mixing rules in terms of local compositions calculated with a local composition model for square-well fluids. The model of [1] was expressed in terms of absolute temperature and density and was linear in density whereas the model of [2] was expressed in terms of reduced temperature and density and was quadratic in density.…”

“…In the models of [1,2] the correction terms were temperature-and density-dependent mixing rules in terms of local compositions calculated with a local composition model for square-well fluids. The model of [1] was expressed in terms of absolute temperature and density and was linear in density whereas the model of [2] was expressed in terms of reduced temperature and density and was quadratic in density. The model of [2] was applied to air and the related binary mixtures and proved to be superior to the formulation of model [1] when applied to those systems [19].…”

“…The model of [1] was expressed in terms of absolute temperature and density and was linear in density whereas the model of [2] was expressed in terms of reduced temperature and density and was quadratic in density. The model of [2] was applied to air and the related binary mixtures and proved to be superior to the formulation of model [1] when applied to those systems [19]. From the above experience emerges the rationale for this work: to extend to a set of non-polar fluids and the related mixtures the application of a Helmholtz energy model analogous to that of [2], i.e.…”