Fluidization and packed bed behaviour in capillary tubes

Abstract

Packed and fluidised beds in microfluidic devices offer the potential of enhanced heat and mass transfer capability at a scale where the process can be closely controlled. The knowledge of hydrodynamics of packed and fluidized beds in capillary tubes is essential for the design and optimization of such devices. This study experimentally examines the hydrodynamics of packed and fluidized beds in terms of pressure drop, bed expansion and minimum fluidization velocity in tube sizes with inner diameters of 0.8, 1.2 and 17.1 mm. Specifically the effect of particle-wall interaction on the hydrodynamic characteristics of the beds was examined by changing the tube-to-particle diameter ratio. It was found that as the tube diameter reduces the bed voidage sharply increases leading to a reduction in the pressure drop across the bed. Also a distinctive rise in pressure drop was observed at lower tube-to-particle diameter ratios which are found to be associated with the particle-wall interaction