CONICET | Buscador de Institutos y Recursos Humanos

The wall of the tube or cylindrical vessel imposes a physical restriction on the free accomodation of particles in random packed beds. The primary effect is the building of a highly ordered layer of particles against the wall. this firs layer induces the formation of sybsequent layers, which show a decreasing degree of order. This pattern introduces systematic radial voidage profiles. the practical importance of these radial variations is the change of transport properties of the packing itself and of luid flowing through the bed. The revision of the experimental works devoted to characterise radial voidages profiles reveals the variety of techniques employed and significant differences in scope. Although some general trends can be outlined for packing other than mono-sized spheres, the scarcity of experimental data make uncertain the possibility of quantitative estimations. Instead, the experimental data gathered for spheres of the same size have been made possible the development of predictive tools introducing the effect of the main variable, the ratio between vessel and particle sizes. A survey of both models describing the radial voidage distribution and models for the radial distribution of particle centers, is given here. Reasonably accurate results can be obtained by employing some of them. Finally, some efforts intended to model the whole assemblage of a bed of spheres are discussed.

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