Numerical Analysis of Mixing and Chemical Reactions in a Two-Dimensional Laminar Flow Field

Residence time distributions, single bimolecular and series-parallel chemical reactions are numerically simulated in the incompressible laminar flow through a two-dimensional square mixing chamber. A finite volume method is used to solve the Navier-Stokes, continuity and the transport equations for the different chemical species. The steady flow fields are assumed to be independent of the chemical reaction and the composition of the fluid. In order to predict the numerical diffusion accurately a second order finite difference scheme is applied on a fine computational mesh, so that the grid Peclet number is everywhere smaller than two. The results are compared with theoretical values for ideally stirred tank reactors. In the presence of relatively strong diffusion the yield of single reactions is comparable to the one for turbulent mixing in an ideal tank reactor. The selectivity for the secondary product in a series-parallel reaction system shows the typical increase with the Damköhler number due to diffusion effects.