INTERNAL RECIRCULATION FLOW STRUCTURE IN VERTICAL UPFLOW GAS-SOLIDS SUSPENSIONS .1. A CORE-ANNULUS MODEL

A comprehensive, predictive two-region model has been developed to describe the core-annular internal recirculation flow structure in vertical gas-solids upward flowing suspensions. This new model is more flexible by allowing axial variations of the core radius and the gas and particle velocities in both the core and the annular regions. The validity of the model has been confirmed by good agreement between the predicted values and the various experimental measurements reported in the literature, including the radius of core region, voidage in the core region, solids recirculation ratio and deposition coefficient.