Reactive mixing in a tubular jet reactor: a comparison of PDF simulations with experimental data

Abstract

The simulation of turbulent reactive flows in chemical reactors can be extremely useful for practical applications. In particular, both industrial and academic chemical reaction engineers are keenly interested in the exact description of the composition field in a reactor volume. Results from two different probability density function (PDF) descriptions of a laboratory tubular jet reactor are compared with experimental data for acid—base neutralization in turbulent liquid media. The first description is based on the Lagrangian joint PDF of velocity and composition, while the second is based on the Eulerian composition PDF. In both descriptions chemical reactions are treated exactly, but molecular mixing must be modeled. A computational fluid dynamics code (FLUENT) provides the mean velocity field and turbulence quantities. Results are found to be sensitive both to turbulent diffusivity and to the model for molecular mixing. A new model for the effect of scalar integral-length scale relaxation on the molecular mixing rate is proposed. By comparison with experimental data, the superior performance of a new model over existing molecular mixing models is demonstrated.