Laminar free convection from a vertical plate in partly dissociated gases

Two-dimensional steady free convection from an isothermal vertical plate is studied in a gas where a reversible very fast reaction of dissociation A ↔ 2B takes place at atmospheric pressure. The effective properties in the presence of dissociation are evaluated. The governing boundary-layer equations are solved numerically for a wide range of values of the independent variables. All the data obtained are correlated by a single correlation even if the temperature interval in the boundary layer (TW, T∞) is allowed to vary in a wide range, both in relative location and width, in respect to the temperature interval of dissociation. The correlated dimensionless parameters include the ratio ρW/ρ∞ and are defined through the mixture effective properties calculated at TW and T∞. The maximum absolute value of the relative error results to be dependent essentially by two particular parameters related to the variations of α and ρ∗ in the boundary layer.