Effect of shell-side flows on the performance of hollow-fiber gas separation modules

A theoretical analysis of shell-side flow effects on the performance of hol low-fiber gas separation modules is presented. The theory uses Darcy's law to relate fiber packing, pressure fields, and velocity fields within the sh ell. The resulting shell conservation equations are coupled to the lumen co nservation equations through the permeation relationship. This two-dimensio nal (2-D) analysis quantifies the performance penalty associated with gas d istribution across the fiber bundle at the shell inlet and outlet. Theoreti cal predictions for the production of nitrogen from air in a commercial she ll-fed module are closer to experimental data than predictions obtained ass uming one-dimensional (1-D) plug flow. Fluid flows primarily across fibers near the inlet and outlet ports, and along fibers between ports. Nitrogen c omposition increases along fluid streamlines, which leads to axial and radi al concentration variations within the fiber bundle. Diffusional contributi ons to shell mass transfer are small for the modules considered here. (C) 2 002 Elsevier Science B.V. All rights reserved.