Experimental and theoretical investigation of the mass transfer controlled regime in catalytic monoliths

Measuring velocity and turbulent diffusivity in wall-flow filters using compressed sensing magnetic resonance

“…These effects are typically modelled using empirical correlations based on flow through abrupt cross-sectional area changes [10,11] and perforated plates [12,13], but such models do not capture the complex geometry and multi-channel nature of filters. Further, most models do not consider the flow profiles inside channels and the effects of flow maldistributions in such channels on heat and mass transfer [14,15]. A small number of three-dimensional simulations have been performed to study the contraction and expansion of gas at the ends of filters, notably by Konstandopoulos et al [16] and Liu and Miller [17].…”

“…Schematic of a typical wall-flow filter (not to scale) showing the typical flow features predicted by earlier numerical simulations[8,14,15]. The plugs at the end of the channels extend 0.5 cm into the filter.…”

Effective diffusivities and pore-transport characteristics of washcoated ceramic monolith for automotive catalytic converter

“…This process gives a thin washcoat layer; however, it also results in a variation in washcoat layer thickness around the channel perimeter. Although the washcoat layer is thin, pore diffusion can affect monolith performance (Kočí et al, 2004;West et al, 2003;Mukadi and Hayes, 2002;Leung et al, 1996;Ramathan et al, 2003), and, thus, need to be included in any realistic mathematical model. Therefore, it is necessary to have reliable information on the mass transport rate in the porous medium (e.g., effective diffusivities of exhaust gases in the washcoat layer).…”

Low‐dimensional models for real time simulations of catalytic monoliths

“…These models use two modes (or two different concentrations/temperatures) and the concept of effective external heat and mass transfer coefficients between the solid and fluid to account for the transverse variations caused due to velocity gradients and diffusion of reactant species or heat in the fluid phase. Many experimental (Hawthorn4; Ullah and Waldram5; Uberoi and Pereira6; Holmgren and Andersson7; and West et al8) as well as theoretical (Shah and London9; Groppi and Tronconi10; Tronconi and Forzatti11; Hayes and Kolaczkowski12; Gupta and Balakotaiah13; and Balakotaiah and West14) correlations have been developed and validated in the literature for these effective external transfer coefficients. A major limitation of most of these classical two‐phase models is that they neglect the temperature or concentration gradients within the washcoat or assume chemical reactions occur only on the surface of the catalytic wall.…”