Mechanical Operation: Sphericity

Sphericity is a shape factor used to find the resemblance shape of irregular particles with a spherical particles. A spherical particle is symmetrical and has no orientation issue. there are correlations which can be used for a spherical particles like pressure drop in fluidised bed. In order to use the correlation for irregular shape particle, sphericity is used. 

Sphericity is defined as surface-volume ratio for a sphere of diameter Dp divided by the surface-volume ratio for the particle whose nominal size is Dp. The nominal diameter of the particle is generally found from screen analysis and the diameter of sphere is calculated by equating the volume of particle equal to sphere. The maximum value of sphericity is 1, because a sphere has minimum surface area for a given volume among all shape.