Study of slip velocity and application of drift-flux model to slip velocity in a liquid–solid circulating fluidized bed

The increasing applications of liquid–solid circulating fluidized bed in chemical/biochemical industries require a better understanding of hydrodynamics of such system. This work aims to experimentally investigate the slip between the phases in a LSCFB. The variation of slip velocity with superficial liquid velocity, solids velocity, bed voidage and particle size and density is discussed. The apparent slip velocity of the phases is higher than the particle terminal velocity of a single particle. The R–Z equation developed based on the homogenous flow characteristics underpredicts the slip velocity in a LSCFB. The drift-flux model which considers the radial non-uniformity and slip between the phases was applied to the data of the present study. The predicted value by the model agreed with the apparent slip velocity well. The study also proposed an empirical correlation to predict the slip velocity. The empirical correlations aggress well with the experimental data.