PARTICULATE PRESSURE IN MONODISPERSE FLUIDIZED-BEDS

The main objective of this paper is to consider random pseudo-turbulen t particle velocity fluctuations in a homogeneous fluidized bed (or in the dense phase of an inhomogeneous fluidized bed). As shown previous ly, these fluctuations are caused when the relative fluid flow interac ts with random fluctuations of particle concentration. Bed particles a re assumed to exchange their fluctuation energy and momentum through d irect collisions. This being the case, and if particle concentration i s sufficiently high, the particle velocity fluctuations are likely to be nearly isotropic, and so they can be characterized by a single scal ar parameter. We introduce the doubled mean energy that is related to one translational degree of particle freedom in the capacity of just s uch a scalar parameter, and ii plays substantially the same role as te mperature plays in molecular gases. However, in contrast to temperatur e. this energy cannot be regarded as an independent variable, but rath er represents a function of mean particle concentration and of physica l parameters. We then formulate the equation of stale which describes the particulate pressure that is caused by particle velocity fluctuati ons and is influenced by the conductivity of momentum during collision s. Thus defined, this pressure is successfully employed (1) to model t he particle distribution that establishes itself to the fore of a bubb le rising in a macroscopically uniform fluidized bed, and (2) to study the hydrodynamic stability of gas-fluidized beds with respect to infi nitesimal one-dimensional disturbances. Copyright (C) 1996 Elsevier Sc ience Ltd