Entry mass transfer in axial flows through randomly packed fiber bundles

Abstract

AbstractAn analysis of the effects of nonuniform fiber packing on external mass‐transfer coefficients for axial flows through bundles of parallel, axially oriented fibers is presented in the entry mass‐transfer limit. In this limit, one can obtain an analytic solution to the mass‐transfer boundary‐layer equations in terms of the velocity gradient on the fiber surface for either a constant wall flux or constant wall concentration. To explicitly calculate mass‐transfer coefficients, a numerical approximation for the velocity gradient is obtained from the conservation of momentum equations using the boundary‐element method. Results indicate that the effective mass‐transfer coefficient depends strongly on fiber packing. Regions of higher fiber packing have lower flows and lower mass‐transfer coefficients than regions of lower packing. The net effect is a dramatic decrease in overall mass‐transfer coefficient relative to mass‐transfer coefficients in regularly packed fiber bundles.