A simulation model has been developed to model drop populations in a stirred tank. A multiblock stirred tank model has been used with the drop population balance equations developed in the literature. The stirred tank is modeled separately so that local turbulent energy dissipation values and fluid flows are used in the drop breakage and coalescence functions. This model has several attractive features, e.g. it can predict the inhomogenity of dispersions and some scale-up phenomena. Because local conditions can be used in the drop rate functions needed in the population balances, it is possible to take these fundamental processes into closer examination. It seems that the parameter values in the drop breakage and coalescence models depend on flow and turbulence averaging for the vessel. This proposes that for "intrinsic" drop breakage and coalescence rates, a multiblock model for the stirred tank is needed in parameter estimation as well. The stirred tank flow model may be obtained from measurements or from computational fluid dynamics simulations in a straightforward manner.