Mixing and chemical reactions: A contrast between fast and slow reactions

Abstract The effect of fluid mixing on chemical reactions is analyzed by means of a model which treats simultaneously the complex interactions of mechanical mix diffusion and reaction. The model assumes that reactants diffuse from adjacent sheets of fluid undergoing a stretching motion, contact one another and This stretching motion causes deformation of the intermaterial surface and is designated mechanical mixing. A history of striation thickness s ( t ) contains all information about fluid mechanical mixing. Numerical methods were employed to solve the simultaneous partial differential equations of the model for mixing and single-step irreversible reactions. A criterion is established for limits of reaction control of bimolecular reactions by mixing, including diffusion, and by chemical kinetics in terms of a single dimensionless group φ  kC B 0 S 2 / D A . The present model can be applied to reactions in both laminar and turbulent flows.