Mechanically agitated reactors are widely used in variety of process industries. Traditional designs assume perfect mixing which often fails to predict the performance of large scale industrial reactors. The effect of mixing becomes pronounced when the time scales of some of the reactions are small compared to the time scale of mixing. The objective of this work is to predict the influence of mixing on the performance of stirred-tank reactors by developing a compartmental model that incorporates the flow field simulated by CFD. This enables the coupling of the flow field, turbulent mixing and kinetics in an appropriate way, and bridges the existing gap between CFD and phenomenological models. (c) 2006 American Institute of Chemical Engineers.