Sensitivity of the turbulent Schmidt number and the turbulence models to simulate catalytic and photocatalytic processes with surface reaction limited by mass transfer

Based on CFD's simulations using RANS and SGDH (Standard Gradient Diffusion Hypothesis), this study presents an alternative to better predict turbulent catalytic systems with surface reaction limited by mass transfer selecting an optimal turbulent Schmidt number (YSct). Simulations of H2O2 degradation were performed in an annular reactor with Mn/Al oxide immobilized into the wall using the AKN, RSM and standard k-epsilon turbulence models with the Sc-t varying from 0.2 to 1.1. The numerical apparent reaction constant (k(app)) was compared with literature data to verify the prediction errors. The ideal Sc-t was applied to simulate the benzoic acid photocatalytic degradation in photocatalytic reactor coated with TiO2 for different flow rates. The results showed that the Sc-t of 0.8 for AKN, 0.7 for RSM, and 0.2 for standard k-epsilon are the best for systems with high mass transfer limitations and the Sc-t of 1.1 for AKN, 1.0 for RSM, and 0.4 for standard k-epsilon are the best for systems with low mass transfer limitations. It was concluded that all turbulence models predicted well the mass transfer when the ideal Sc-t was used and the standard-k-epsilon model could be an alternative since the prediction error was less than 6.5% with low computational cost. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.