For non-spherical particles Haider and Levenspiel [227] developed the correlation

(12–52)

where

(12–53)

The shape factor, , is defined as

(12–54)

where is the surface area of a sphere having the same volume as the particle, and is the actual surface area of the particle. For the purposes of calculating particle mass, drag force, and , the particle size should be the diameter of a sphere having the same volume.