Characteristic quantities of divided solids. Powder classification
Fluidized beds - General characterization and applications

The physical quantities, representative of monodisperse divided solids, are essentially their true density, i.e. ρ_s, and their diameter d_p.

• In the case of non-spherical particles, we define d_p as the diameter of an equivalent sphere, having the same volume as that of the particle under consideration. We then introduce a sphericity factor Φ_s, defined as the ratio between the surface area of a sphere of the same volume as the particle, to its true external surface areaS_p$\left({\Phi }_{\text{s}}⩽1\right)$, i.e. :