ENHANCEMENT OF FILM MASS-TRANSFER BY FORCED CONVECTIVE FLOW PERPENDICULAR TO A HETEROGENEOUS SURFACE

The enhancement of intraparticle mass transport by intraparticle force d convective flow has been recognized in numerous past studies when '' large-pore'' materials are used in the presence of large pressure drop s. However, the enhancement of film mass transfer by forced convective flow perpendicular to the ''heterogeneous'' surface has not been prev iously studied. In this study, a ''unit cell'' model is used which des cribes the steady-state mass transfer in the concentration boundary la yer for the case where forced convective flows parallel and perpendicu lar to a heterogeneous surface are present. The perpendicular flow fie ld in the momentum boundary layer is determined using the Navier-Stoke s and continuity equations. The mass balance equations are solved by t he method of collocation on finite elements. The minimum enhancement o f film mass transport to the heterogeneous surface, measured by the Sh erwood number ([Sh] = k/k) due to the forced convective flow perpendi cular to the surface, given by the Peclet number, Pe(y), is assessed. When Pe(y) < 0.5, [Sh] is nearly independent of Pe(y), and when Pe(y) is larger than 5, [Sh] almost-equal-to Pe(y)/2, i.e., k almost-equal-t o upsilon(o)/2, so that D = upsilon(o)delta/2.