On the role of energy dissipation in a dynamically structured fluidized bed

Abstract

This work explores the effect of interparticle friction on the stability of a structured bubble flow in gas–solid fluidized beds. We provide a detailed quantification of the evolution of bubble properties at varying frequency, comparing experiments with CFD-DEM (computational fluid dynamics – discrete element modeling) simulations. Friction plays a key role. It creates intermittent solid-like regions that restrict the mobility of solids and endow the flow with enough memory to correlate consecutive nucleation events. As friction decreases, solid-like regions widen, allowing the circulation of solids; simultaneously, bubbles grow, move apart and ultimately break up the structure. CFD-DEM reproduces this phenomenon well in a small bed, but shows qualitative differences in bubble shape and acceleration. These deviations propagate into substantial errors at higher frequency or larger domains displaying multiple bubble rows, which stresses the need for further research to understand the effects of other particle properties, polydispersity and the domain size.