Visualization of defluidization phenomena caused by gas switching in a two-dimensional fluidized bed

Transient defluidization occurs when fluidizing gas is switched from a lower density gas to a higher density gas. The intensity of this phenomenon increases with decreasing particle size and with increasing difference between gas densities. In order to investigate the mechanism of this effect, images of the transient phenomenon were captured using a video camera and visualized using digital image conversion. Gray-scale pictures were obtained based on the transmittance of back light through the emulsion phase in a thin two-dimensional fluidized bed. The gray-scale pictures were transferred into pictures with a color gradation. The generation, expansion, and elimination of defluidization after switching of the fluidizing gas can clearly be seen by observing the reconstructed color movies.

Transient defluidization occurs when fluidizing gas is switched from a lower density gas to a higher density gas. Images of the transient phenomenon were captured using a video camera and visualized using digital image conversion. This enabled us to observe the generation, expansion, and elimination of defluidization after switching of the fluidizing gas.Figure optionsDownload as PowerPoint slideHighlights
► Transient defluidization occurs after gas switching from low to high density gases.
► The phenomenon in a 2D fluidized bed is visualized by reconstructed color movies.
► Defluidized region is first formed at the bottom of the bed.
► Mechanism of the growth of defluidized region is affected by gas adsorption.
► Fluidization is restored as the defluidized region is eroded by gas and particles.