Randomly packed beds of equal spheres exhibit damped oscillatory voidage variation in the near wall region. Models reported in literature were found to be lacking in their ability to relate this variation to average bed porosity. The changing mean of the voidage oscillations and deviations from sinusoidal behavior were not described well either. Experimental data and a new radial bed porosity model are presented. Improved radial bed voidage and average bed voidage predictions were demonstrated. It has further been shown that multiple stable packing configurations exist within the same packing mode, which complicates modeling at a small column to particle diameter ratio.

Voidage variation in packed beds at small column to particle diameter ratio

The influence of confining walls on the pressure drop in packed beds

Discussions in the literature about the influence of (1) the operating parameters Re 0 (Reynolds number) and D/d p (tube-to-particle-diameter ratio), and (2) the physical phenomena of wall friction and flow maldistribution on the pressure drop in packed tubes are in conflict. This influence is analyzed by applying the extended Brinkman equation to cylindrical beds of particles of nearly (but not perfectly) spherical shape and moderate-size dispersity.

Impact of tube-to-particle-diameter ratio on pressure drop in packed beds

Wall effects for the pressure drop in fixed beds

A review of computational fluid dynamics for forced-air cooling process

In their study of the linear stability limits for free convection in layers of porous media or packed beds with throughflow, others found that throughflow was generally stabilizing, but there was an exception. In the case of flow toward a porous boundary, they found that the numerically calculated Rayleigh-Darcy number initially decreased and went through a minimum as the appropriate Peclet number increased from zero. It was stated that the origin of the minimum was not completely understood, but others had eliminated numerical inaccuracy as a possible cause. Thus a small amount of throughflow can have a destabilizing effect in at least one situation. The primary purpose of this note is to explain this effect. The opportunity is taken to provide some supplementary material.

Convective instability in porous media with throughflow

Dans ce modele, on suppose qu'un milieu poreux, a l'interieur duquel la loi de Darcy est applicable, occupe toute la colonne a l'exception d'une couche mince d'epaisseur uniforme adjacente a la paroi

D. A. Nield

Papers

Convective instability in porous media with throughflow

Alternative model for wall effect in laminar flow of a fluid through a packed column