Dispersion in pulsed systems—III: Comparison between theory and experiments for packed beds

Abstract The theoretical development put forth in Part II of this paper is applied to several two-dimensional, spatially periodic porous media in order to determine components of the dispersion tensor for Peclet numbers ranging from 1 to 104. The calculated longitudinal dispersion coefficients show reasonable agreement with experimental data for a packed bed of spheres in a cubic array. This provides support for the theory developed in Part II; however, for randomly packed beds the experimental values of the longitudinal dispersion coefficient are smaller than those predicted using the spatially periodic model. In addition, the functional dependence on the Peclet number for the experimental data differs considerably from that predicted by the theory. The dependence of the dispersion coefficient on distance is discussed from the point of view of the results presented in Part I, and some recent experimental observations and calculated results for the effect of particle size distribution are given. In addition, our calculated values for the lateral dispersion coefficient are compared with experimental values and are found to be too small by about three orders of magnitude at a Peclet number of 103.