Shear-thinning fluids flow in fixed and fluidised beds

In the paper the results of experimental studies directed on the effect of liquids' properties (aqueous solutions of polymers and surfactants) on resistance of the flow through porous and fluidised beds, are presented. It was shown that the determination of the values of minimal fluidisation velocity on the basis of an analysis of pressure drop related to the current two-phase system height gives the more accurate values than the method based on the initial bed height. Independently of the Newtonian or shear-thinning properties of the liquid flowing through motionless or fluidised bed, the relation of the friction factor on well-defined Reynolds number (related to real rheological parameters of a liquid studied) is analogous. It has been shown that the diagram proposed by Koziol et al. can be stated as the generalized one, not only for the determination of the solid particles motion in Newtonian fluids, but for the shear-thinning liquids too. In the last case it should be taken into account that the critical value of porosity cannot be taken equal to 0.4, but should be appropriate to the real porosity in the critical conditions for a given system solid particle-liquid. The generalization of both, the map of Bi and Grace related to the characteristic fluidisation ranges and the diagram of the classification of particles fluidised proposed by Goossens for gas-fluidisation, on any systems of solid particles-power law fluids, has been proposed. (C) 2007 Elsevier Ltd. All rights reserved.