Particle normal stress distribution around a rising bubble in a fluidized bed

The classical hydrodynamic approach has been examined regarding the issue of particle pressure in fluidized beds. The particle-pressure distribution around an isolated Davidson's bubble is derived for the constant-voidage case. It is found that the bed expansion stress appears in the upper region and the bed compression in the lower half region around a bubble. The maximum particle pressure is (5/4)rho(p)(1 - epsilon(mf))gR(b) for a 2D bubble and (3/2)rho(p)(1 - epsilon(mf))gR(b) for a 3D bubble. The negative pressure region which exists right above a bubble has a maximum pressure of (-1)rho(p)(1 - epsilon(mf))gR(b) for a 2D bubble and (-0.843)rho(p)(1 - epsilon(mf))gR(b) for a 3D bubble. The theoretical prediction is successfully validated experimentally by a particle-pressure probe developed in the present work. (C) 1998 Elsevier Science S.A. All rights reserved.