On the estimation of effectiveness factor in metallic monoliths presenting non-uniform coatings

Abstract

The one dimensional two-zone model (1D-2Z) to estimate effectiveness factor in non-uniform coatings of metallic monolith channels with sinusoidal cross-section is thoroughly tested in this contribution. The model relies on the idea of splitting the cross-section of the coating in two zones that can be modelled independently taking into account the diffusion and simultaneous reaction in a single direction (1D). One of the zones is considered as a slab, while the previously developed variable diffusivity model (1D-VD) is applied to the other. The predictive capabilities of the 1D-2Z model is assessed for three kinetic expressions: a first order reaction and two more challenging cases defined by Langmuir-Hinshelwood-Hougen-Watson expressions: one of them with a moderate self-inhibition effect and the other with a strong self-inhibition effect, close to the onset of the multiple steady states behaviour. Simultaneously, different degrees of non-uniform coatings are considered. The 1D-2Z model allows obtaining a remarkable precision in the estimation of the effectiveness factors for the complete range of Thiele modulus with maximum errors below 5.6%.