AXIAL-DISPERSION IN PACKED FIBER BEDS

The application of fibrous sorbent materials in gas and liquid separations as an alternative to conventional granular sorbents has attracted increased attention over the last decade. Though axial dispersion of flow in granular beds has been investigated extensively, published experimental data concerning the dispersion phenomena in porous fiber beds are sparse. The study presented involves the experimental determination of axial dispersion for water flow in packed beds of randomly aligned fibers, using a tracer pulse response technique. The influence of the bed properties (fiber diameter, bed void fraction) and the flow velocity on the dispersion coefficient was determined. The measured Bodenstein numbers vary between 0.001 and 0.1. the experimental results are compared with predicted values obtained from a theoretical model, based on isotropic fiber structures, showing substantial disagreement between the experimental and predicted values attributed to inhomogeneities of the fiber structure. The effect of inhomogeneities is similar for various types of random fiber structure. An empirical correlation for the axial dispersion coefficient for water flow in random fiber structures is presented.