In this research, the influence of the diameter and speed of the mixer in a continuous stirred tank reactor (CSTR) was investigated using the Computational Fluid Dynamics (CFD). The mixing behavior was measured and predicted in terms of age distribution function, I(Ɵ). This approche was used by the impeller swept volume method for CSTR in the presence of impeller and baffle. KCl as a tracer was injected into the water inside the tank and the mass fraction of KCl at the outlet of the tank was considered as one of the investigated criteria for deviation or closeness to ideal mixing. Using the computational fluid dynamics simulation results, the velocity distribution was investigated for two different diameters of the stirrer. The results showed a very important effect of the stirrer size on the fluid movement pattern inside the reactor. Moreover, a good agreement of the results with the experimental data indicated the validity of the CFD model.
