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The effect of particle diameter on fluidization under vibration was studied. Glass beads with diameters ranging from 6 to 100 μm and pertaining to the Geldart groups C and A, were used as fluidizing medium. In order to examine the effect of vibration on the fluidization characteristics of the particles, minimum fluidization velocity ( u mf ), void fraction ( e mf ) at u mf and flow patterns in the bed were measured. For group C powders, u mf decreased with increasing the vibration strength, while for group A powders, u mf remained almost constant. With vibration, the flow patterns in the bed were changed, especially in the case of group C powders. For larger powders of 30 μm, channels and cracks were not observed in the bed. However, for smaller powders than 20 μm, stable channels and cracks were observed under no vibration and they disappeared by vibration. The lower limit of the gas velocity at which the channeling in the bed was not observed was lowered as the vibration strength increases. For smaller powders, the flow pattern in the bed becomes complex as various sizes of agglomerates occur and thus makes vibration difficult to propagate in the bed. |
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