Minimum Fluidization Velocity and Expansion Behavior of Spherical Particle Beds Fluidized with Inelastic and Viscoelastic Fluids

Experimental investigations depicting the effect of pseudoplasticity and fluid elasticity on the minimum fluidization velocity and bed expansion behavior of spherical particles are presented. Experiments have been carried out to fluidize the beds of spherical particles using different types of fluids, viz. Newtonian fluid (NF), inelastic fluid, viscoelastic (shear-thinning) fluid (VEF), and Boger (almost constant viscosity) fluid (BF) , covering a wide range of conditions: 0.002 < Re-t < 4163; 0.48 < n <= 1; 0.42 <= lambda <= 2.07 s. Based on the experimental data and pictorial representation, it is observed that the course of bed expansion follows nonhomogeneous fluidization behavior along with channeling for VEFs, which is predominant in shear-thinning VEFs compared to BFs. Further, the minimum fluidization velocity decreases as the elasticity and shear thinning of the fluid increase. This reduction in minimum fluidization velocity represented as a function of elasticity number (E) follows asymptotic behavior, which shows the dominance of viscous forces over elastic forces at a higher Reynolds number. A simple form of corrective elasticity number function f(E) is proposed to extend the use of the equation proposed by Bena, applicable for NFs, for predicting the minimum fluidization velocity in the case of VEFs as well as BFs. Further, the equation proposed by Garside and Al-Dibouni, applicable for NFs, has also been extended to predict bed expansion behavior for VEFs and BFs.