A packed bed of uniform spherical particles of diameter, d= 2.5
mm, density ρs= 4000 kg/m3 , and voidage e= 0.45 is fluidised by
means of a liquid of viscosity μ= 1 mN s/m2 and density ρ= 900
kg/m3 . (a) Starting from Carman’s and Ergun’s equations reported
in the attached equations sheet, derive the corresponding
expressions for the minimum fluidising velocity, umf, for both
equations and explain their meaning.