Finite element simulation of mass transfer in laminar swirling decaying flow induced by means of a tangential inlet in an annulus

This work is devoted to the numerical modeling of mass transfer on both cyl inders of an annular cell subjected to swirling laminar decaying flow induc ed by means of a single tangential inlet greater in diameter, phi (e), = 12 .5 mm, than the annular gap thickness, e = 7 mm. The complete diffusion-con vection equation has been solved in a three-dimensional frame by means of t he FIDAP finite element package using the velocity fields previously predic ted by the same numerical technique. As for the Row-field, we have shown th at a correct prediction of mass transfer coefficients in such a flow is str ongly linked to an adequate mesh generation, especially when mass transfer occurs on the inner wall of the annulus, near which recirculating eddies ex ist. Numerical results have been found to be in good agreement with experim ental data previously obtained on both cylinders of the annulus. A simulati on study of the influence of the Schmidt number on the overall mass transfe r on the outer cylinder has shown that the mean Sherwood number varies as S c-0.44 Even for forced convection, the numerical simulation of mass transfe r is not directly obtained from the simulation of the dynamics of the flow. Due to the difference in mass and momentum boundary layer thicknesses, the mesh refinement has to be adapted to Schmidt number, (C) 2001 Elsevier Sci ence B.V. All rights reserved.