Prediction of flow characteristics and energy balance for a variety of downflow impellers

A computational fluid dynamics (CFD) model has been developed for predictio n of the flow characteristics based on the forces generated on the impeller blades. A good agreement between the CFD predictions and the experimental measurements at several locations in the vessel has been observed. The mode l has been validated for a wide variety of axial downflow impellers. An edd y identification scheme has been proposed to estimate the values of the tur bulent length scales, eddy diffusivity, and turbulent energy dissipation ra te. The impeller power number has been calculated by three methods: (i) the integration of local values of epsilon predicted from CFD, (ii) a method b ased on the forces acting on the impeller blades, and (iii) the outflow of angular momentum from the impeller zone. A good agreement has been observed between the predicted values of the power number by the previous three met hods and reported values for a wide variety of axial flow impellers.