A Small-Signal Sound Speed and Parameter of Non-linearity B/A in a Ternary Mixture. Examples on Calculations of Mixture Consisting of Air, Water and Water Vapour

Detail calculations of the excess entropy of a ternary mixture in terms of excess pressure and density are carried out with accuracy up to quadratic non-linear terms. The only assumption is that the vapour and the neutral gas are ideal gases. As an example, a ternary mixture consisting of air and water being in equilibrium with its vapour is considered. Finally, the small-signal sound velocity and the parameter of non-linearity B/A are expressed in terms of mass concentrations of air and vapour and air pressure. Illustrations of sound velocity reveal divergence with previous theories. Calculations of the parameter of non-linearity B/A show that it increases with vapour mass concentration and that it decreases when air partial pressure increases.