Chemical Engineering Science, Vol.52, No.19, 3277-3286, 1997
A Lattice-Gas Study of Dispersion in Alveolated Channels
Axial dispersion in alveolated channels was studied via lattice-gas automata(LGA), for both slug and step-change inlet conditions. There was good agreement between the effective diffusion coefficient (D*) calculated by the LGA method, and the D* predicted by the ’stagnant pocket’ formalism developed by Aris, Turner, and Tsuda et al. The enhancement of D* was dependent on the ratio of alveolar volume to central channel volume and the Peclet number. For Pe greater than or equal to 5, D* was substantially greater than the Taylor-Aris prediction for flow between parallel flat plates. For Pe < 3, D* was less than the molecular diffusion coefficient, D-m. In the absence of buoyancy, inlet conditions (pulse vs step-change) had little effect on the calculated D* (less than or equal to 3%). The effect of buoyancy, however, depends on the inlet condition; for an LGA corresponding to 1 mol% SF6 tracer gas in air, D* was increased up to 20% for the step-change, and decreased up to 6% for the slug.