Numerical simulation of RTD in contact tanks with Comsol Multiphysics 3.2b

The objective of this paper is to present the results of a numerical study undertaken to investigate hydrodynamics and turbulent transport and mixing inside two contact tanks, which have the same channels but with different location of the baffles. Thus, two-dimensional steady-state and time-variable numerical simulations were carried on with Multiphysics 3.2b™. Flow field was obtained using standard k-ε model. Tracer transport was analyzed in the cases of a pulse and step release using the 2D advection-diffusion equation. Transient concentration data were used to derive residence time distribution (RTD) function for both the tanks in order to evaluate and to compare their performances. In fact, RTD curves are a description of the time that different fluid elements spend inside the reactor and so are usually applied to identify tank characteristics under both steady-state and time variable conditions. Finally, dispersion coefficients were computed for the tanks