On bed porosity of multisized spheroidal particles.

Abstract

In numerous instances of engineering the problem to quantify the porosity of polydisperse systems arises. Despite its great importance, the theoretical predictability of the bed porosity is still problematic. In the field of ceramics, classically, Furnas' studies on porosity are quoted, where he has studied void fraction resulting from blending two distinct particle sizes in various proportions. Less often, ternary diagrams plotting porosity isovalues for spherical particles beds are used to characterize ternary mixtures of distinct monosized particulate systems (usually in ceramics industry). Although similar studies using polydisperse systems have been conducted, a lot of improvement is yet to be achieved. This article falls in this context and aims at contributing to this field of technical and economic impact. Synthetic samples with controlled particle size distribution were used. The resulting porosity of those glass beads random packs (mimicking several size distributions described by Rosin–Rammler equation) has been experimentally determined under a standardized compaction level. The main result was to obtain an equation for the porosity forecast for bead beds inside spheroidal containers, as a function of the sharpness parameter, n, from Rosin–Rammler distribution. An accurate extrapolation to systems well described by the Whiten sigmoidal distribution was achieved as well. A generalization of the Ergun equation is presented at the end of the article, as an application example.