Two-fluid hydrodynamics of a fluidized bed
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Prior to the formulation of specific problems on the motion or processes of transport in a fluidized bed it is necessary to answer two fundamental questions, without the satisfactory resolution of which consistent theoretical study of the fluidized bed is quite impossible. The first question is related to the formulation of the governing equations-the equations of motion of the fluidized bed as a two-phase continuous medium-the second question is concerned with the construction of some model of the interaction of the fluidized bed with the solid surfaces bounding the bed and the consideration of the boundary conditions which must be imposed on the solution of these equations.
The present study attempts to solve both of these problems. Equations are presented which describe the motion of the fluidized bed as a continuum with account for the relative slip of the phases, where one group of equations concerns the motion of a ficticious liquid porous medium consisting of particles and a liquid phase “frozen” in these particles, while the second group describes the “filtration” of a liquid phase in this porous medium. The influence of the solid walls on the motion of the fluidized bed is described with the aid of concepts on the existence near the walls of a region in which transport of momentum by the liquid phase takes place. The model developed is illustrated using the problem of flow past a solid sphere mounted in an unbounded fluidized bed. This problem also makes it possible to clarify certain unique qualitative features of the motion in a fluidized bed.
KeywordsBoundary Condition Filtration Liquid Phase Porous Medium Solid Surface
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