Analysis of Segmented Flow in Microchannel Reactors

Abstract

Mathematical model of segmented (Taylor) flow hydrodynamics in microchannels was built up on the base of fundamental approach (continuity and Navier-Stokes equations). Velocity profiles in the liquid slug, liquid film, and in the bubble (droplet), bubble velocity, pressure drop, dispersed gas, or liquid hold-up were calculated by using this model. Recently, this model was extended to the non-Newtonian fluids (with power law rheology). Three-layer Taylor flow model was created in order to simplify understanding of the inner transfer phenomena within slugs of continuous phase and the droplet of dispersed phase. It was shown that process intensification is caused by Taylor vortices both in continuous and dispersed phases. Radii of the center of Taylor vortices, by-pass, and transit films along with the slug and droplet lengths define geometry of three-layer Taylor flow. The three-layer approach allows to calculate convective transport within segmented flow quickly (compared to CFD calculations) and to analyze systematically the influence of various factors on the mass and heat transfer rates. The frequency of circulations within liquid slugs was revealed as the most important factor defining the mass transfer in segmented flow. The coincidence of the obtained theoretical results was verified by numerous experimental data available in the literature.