Fluidized beds are common equipment in many process industries. Knowledge of the hydrodynamics within a fluidized bed on the local scale is important for the improvement of scale-up and process efficiencies. This knowledge is lacking due to limited observational technologies at the local scale. This paper uses X-ray computed tomography (CT) imaging to describe the local time-average gas holdup differences of annular hydrodynamic structures that arise through axisymmetric annular flow in a 10.2 cm and 15.2 cm diameter cold flow fluidized bed. The aeration scheme used is similar to that provided by a porous plate and hydrodynamic results can be directly compared. Geldart type B glass bead, ground walnut shell, and crushed corncob particles were studied at various superficial gas velocities. Assuming axisymmetry, the local 3D time-average gas holdup data acquired through X-ray CT imaging was averaged over concentric annuli, resulting in a 2D annular and time-average gas holdup map. These gas holdup maps show that four different types of annular hydrodynamic structures occur in the fluidized beds of this study: zones of (1) aeration jetting, (2) bubble coalescence, (3) bubble rise, and (4) particle shear. Changes in the superficial gas velocities, bed diameters, and bed material densities display changes in these zones. The 2D gas holdup maps provide a benchmark that can be used by computational fluid dynamic (CFD) users for the direct comparisons of 2D models, assuming axisymmetric annular flow.
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August 2012
Multiphase Flows
Comparisons of Annular Hydrodynamic Structures in 3D Fluidized Beds Using X-Ray Computed Tomography Imaging
Joshua B. Drake,
Joshua B. Drake
Department of Mechanical Engineering,
e-mail: jdrake@iastate.edu
Iowa State University
, Ames, IA 50011
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Theodore J. Heindel
Theodore J. Heindel
Department of Mechanical Engineering,
Iowa State University
, Ames, IA 50011
Search for other works by this author on:
Joshua B. Drake
Department of Mechanical Engineering,
Iowa State University
, Ames, IA 50011e-mail: jdrake@iastate.edu
Theodore J. Heindel
Department of Mechanical Engineering,
Iowa State University
, Ames, IA 50011J. Fluids Eng. Aug 2012, 134(8): 081305 (8 pages)
Published Online: August 9, 2012
Article history
Received:
October 14, 2011
Revised:
June 11, 2012
Online:
August 9, 2012
Published:
August 9, 2012
Citation
Drake, J. B., and Heindel, T. J. (August 9, 2012). "Comparisons of Annular Hydrodynamic Structures in 3D Fluidized Beds Using X-Ray Computed Tomography Imaging." ASME. J. Fluids Eng. August 2012; 134(8): 081305. https://doi.org/10.1115/1.4007119
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