Chaos and recurrence analyses of pressure signals from bubbling fluidized beds

Results from non-linear analysis of bubbling fluidized beds are presented in this study. The experiments were performed in cylindrical columns having internal diameters of 2.5 inches, 4 inches and 6 inches while operating conditions, material properties and static bed height were held constant. Superficial velocity of air at the inlet was varied from 2.97 to 5.35 times minimum fluidization velocity in each column. The test procedure involved randomization and replication to estimate measurement uncertainty and identify bias if present. The columns were split into regions based on dominant physical mechanisms occurring within. Fractal parameters were evaluated from differential pressure data which confirm deterministic chaos. These measures represent a broad range of spatial and temporal scales and were used to elucidate multiphase dynamics in different sections of these columns. Fractal analysis is hence shown to provide more intuition particularly when a true scale-up study based on non-dimensional groups becomes prohibitive.