Modeling the Hydrodynamics of Downers by Cluster-Based Approach

Cluster formation in the downers has been supported by experimental works of different investigators. A new model has been developed in this work based on the force balance over a cluster moving along the axial length of the downer. The clusters are considered to be spherical with constant diameter. Axial profiles of cluster velocity, solid holdup, and pressure in downer have been obtained by this model. Comparison between the results of the model and the experimental data found in the literature showed that the model is able to predict the experimental data satisfactorily. Also, a correlation has been proposed for equivalent diameter of clusters in the downer as a function of the superficial gas velocity and the solids circulation rate.