CALCULATION OF WALL MASS-TRANSFER RATES IN SEPARATED AQUEOUS FLOW USING A LOW REYNOLDS-NUMBER K-EPSILON MODEL

Mass transfer in aqueous, turbulent flow through a sudden pipe expansion is simulated with a low Reynolds number (LRN) k-epsilon-eddy viscosity model. The predicted wall mass transfer rates are tested against experimental data, obtained with electrochemical measurements (Re = 2.1-13 x 10(4) and Sc = 1460). LRN modifications to the turbulence model in the near-wall regions, coupled with the turbulent Schmidt number concept, enable successful predictions of wall mass transfer rates to be obtained. For the specific case of a high Schmidt number fluid, the mass transfer boundary layer is much thinner than the hydrodynamic boundary layer. Furthermore, even low levels of turbulence in the near-wall region are shown to have significant influence on the overall wall-mass transport.