Effect of the Re number on heat and mass transport in a catalytic monolith

The numerical investigation of interphase heat transfer in a catalytic combustor, under laminar flow regime at different values of the Re number, is performed by means of a 2D axy-symmetric model of a single monolith channel. Numerical results highlight that axial diffusion comes to play an important role in the ignition region also at high convective fluxes (high Re) due to the strong flow perturbation accompanying light-off, with the consequences that: (a) the ignition position is not a linear function of contact time, as it would be expected at high Re; (b) the heat and mass transfer between surface and bulk gas phase are non-linearly affected by Re, especially in the entrance and in the ignition regions. A previously developed correlation for Nu and Sh is hence extended to include the effect of the Re number on heat and mass fluxes, enabling the prediction of the local value of Nu and Sh in the main features, and in particular the enhancement in the ignition region and the dependence on Re.