Experimental study of local solid volume fraction fluctuations in a liquid fluidized bed: Particles with a wide range of stokes numbers

Abstract

In this study, the solid volume fraction fluctuations of different solid particles in a fluidized bed were measured using an Electrical Impedance Tomography system, which provides local fluctuation values. A wide range of particle Stokes numbers (122≤Stt≤3809) was tested by selecting specific particle sizes and densities. The results were compared with previous experimental studies. Since previous works measured only cross-sectional averages of the fluctuations, the local results of this study were spatially averaged for the comparison. The comparison showed an acceptable agreement in the level of RMS fluctuations. Importantly this study found that: (1) The strongest fluctuations always occurred at a narrow strip by the bed wall. Moving from the wall region towards the bed center, the magnitude of RMS fluctuations decreased. (2) The magnitude of local fluctuations was linked to the particle Stokes number (Stt), such that, at any given radial positions, the RMS fluctuations increased by increasing Stt. (3) Only limited agreement was observed among the trends of the measurements and the predictions of four existing mathematical and semiempirical models. The instantaneous local measurements conducted in this study are useful not only to examine currently available mathematical models, but they can also validate Computational Fluid Dynamics models of liquid fluidization.