PTV and PIV Based Dispersed Phase Velocity Measurements in a pseudo-2D Turbulent Fluidized Bed

Fluidized beds are used in a wide variety of industrial applications ranging from power generation to chemical industry. In a fluidized bed pressurised gas is blown from the bottom of the bed to a solid mass consisting of small particles. The drag force between the gas and the particles causes the bed become fluidized. Fluidized beds can be roughly categorized as bubbling, turbulent, or circulating fluidized beds with increasing fluidization air velocity. In this study, particle velocities and sizes are measured using Particle Tracking Velocimetry (PTV) combined with Particle Image Velocimetry (PIV) in near the top of a turbulent fluidized bed containing two particle populations. In this region the suspension is typically dilute and thus the dispersed phase behaviour is mostly determined by fluid-particle interactions. The dispersed phase velocity measurements were used to compute the time averaged velocity fluctuations and Reynolds stresses. The velocities were categorized by horizontal position, and by measured mass averaged mean fluidization air velocity. The results were compared to few circulating and bubbling fluidized bed studies. The particle velocity profile near the wall was similar to profiles observed in the circulating fluidized bed studies. It was also noticed that the large particles exited the upward flow before smaller particles which lead to differences in comparison to circulating fluidized bed studies. The approach of using a combination of PIV and PTV to handle the varying particle densities was found out to be effective when dealing with flows of highly variable particle densities. In a test case, it was found out that the PIV velocity estimates are slightly less than the corresponding PTV estimated velocities