SCALING OF PERMEABILITIES AND FRICTION FACTORS OF HOMOGENEOUSLY EXPANDING GAS-SOLIDS FLUIDIZED BEDS (Geldart's A powders and magnetically stabilized beds)

Abstract

The concept of a variable friction factor of fluid-driven deformable powder beds undergoing fluidization is discussed. The special problem discussed addresses the friction factor and bed permeability relationships of Geldart's A powders and magnetically stabilized beds in axial fields. Governing equations and scaling relationships are developed through three approaches: (1) Minimization of the pressure drop with respect to the fluid velocity employing the Darcy-Forchheimer equation to gether with the Richardson-Zaki scaling law, (2) Minimization of the pressure drop across an equivalent-channel replacing the actual packed beds by a straight pipe with bed-equivalent obstacle of a simple geometry, and (3) Entropy minimization method applied in cases of the Darcy-Forchheimer equation and the equivalent-channel model. Bed-to-surface heat transfer coefficients are commented in the context of the porosity/length scale relationships developed. Both the pressure drop curves develop ments and phase diagram designs are illustrated by applications of the intersection of asymptotes technique to beds exhibiting certain degree of cohesion.

Keywords

Dates

  • Submission Date2004-12-02
  • Revision Date2005-02-04
  • Acceptance Date2006-02-13

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Volume 10, Issue 1, Pages19 -44