Libraries at University of Nebraska-Lincoln


Document Type


Date of this Version



Thesis (M.S.)—University of Nebraska—Lincoln, 1965. Department of Chemical Engineering.


Copyright 1965, the author. Used by permission.


The flow of fluids through packed beds is a field of science and technology which has developed rapidly during recent years. Major developments have occurred in the area commonly referred to as diffusional operations; in fact, there is hardly a chemical process today which does not ultimately involve one or several steps that are commonly included in this area. Although no general theory exists, knowledge of turbulent diffusion in packed beds is of interest in the technology of catalytic reactors, packed tube heaters, and absorbers.

In this work, mass transfer rates in the radial direction in the dispersed phase for two phase flow in a packed bed were experimentally determined. A column packed with half-inch graphite Raschig rings in which air and water were contacted counter-currently was used. The column was operated so that the water was the dispersed phase with which a continuous “point source” dye stream was injected at the top of the packing.

Capillary tubes placed at a cross-section within the bed enabled liquid phase samples to be withdrawn from various radial positions. These samples were analyzed for dye concentration with a spectrophotometer. From the resulting radial concentration profile a pseudo diffusion coefficient is presented in terms of the dimensionless group commonly called the modified Peclet number

Pe =

where dp is the particle diameter and u is the mean point condition velocity in the axial direction.

Results indicate that an increase in the Reynolds number of either phase will improve mixing in the radial direction in the dispersed phase as evidenced by a decrease in the Peclet number. A satisfactory correlation of this behavior over the range of variables studied is presented along with suggestions for further work in this area

Advisor: Richard E. Gilbert