Effect of dispersion on the diffusion zone in two-phase laminar flows in microchannels

Aim of the present work is to investigate the reaction–diffusion process of a two species system under laminar flow in a T-shaped microchannel. A zone formed at the interface between the aqueous solutions of these two species is affected by advection and diffusion. Through theoretical analyses and experimental results, the effect of dispersion has been shown to influence this diffusion zone. We have defined a parameter called effective diffusivity, to account for the dispersion effects and observed it to be a function of the channel Peclet number. In the limiting case of low Peclet number, this parameter is constant and turns out to be equal to the molecular diffusivity. We have also related effective diffusivity and the dispersion coefficient through scaling estimates.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Interdiffusion zone of two reacting liquids in laminar flow in a microchannel. ► Effect of dispersion. ► Modelling of the near wall zone and evaluation of dispersion coefficient. ► Introduction of effective diffusivity to account for dispersion. ► Dependence of effective diffusivity on channel Peclet number.