Influence of hydrodynamics on liquid mixing during Taylor flow in a microchannel

Abstract

in Wiley Online Library (wileyonlinelibrary.com).The miscible liquid-liquid two phases based on Taylor flow in microchannels was investigated by high-speed imaging techniques and Villermaux/Dushman reaction. The mixing based on Taylor flow was much better compared with that without introducing gas in microchannels, even the ideal micromixing performance could be obtained under optimized superficial gas and liquid velocities. In the mixing process based on Taylor flow, the superficial gas and liquid velocities affected the lengths and the velocities of Taylor bubble and liquid slug, and finally the micromixing performance. The formation process of Taylor flow in the inlets, the initial uniform distribution of reactants and the internal circulations in the liquid slug, and the thin liquid films all improved the mixing performance. Furthermore, a modified Peclet number that represented the relative importance of diffusion and convection in the mixing process was proposed for explaining and anticipating micromixing efficiency.

Energy‐Efficient Solar Photochemistry with Luminescent Solar Concentrator Based Photomicroreactors

“…[17,18] We commenced by adapting the reaction to continuous-flow,using phenylboronic acid as am odel substrate.T he oxygen balloon employed in the original literature report for abatch reaction was replaced by ap ure oxygen stream, resulting in ag as/liquid slug flow regime.The adoption of aslug flow regime increases the mass transfer between the gas and the liquid phase and results in an acceleration of the apparent reaction kinetics. [19] Ideally,t his acceleration can extend the point where the light input becomes al imiting factor,t hus providing the maximum attainable productivity under solar conditions.I ndeed, the reaction was accelerated from the 6hours required in the original report to only 5minutes in the LSC-PM under AM Angewandte Chemie Forschungsartikel 1.5G solar conditions.Notably,the reaction kinetics were now partly light-limited, as shown by the fact that the LSC-PM provided as ubstantial acceleration compared to as imple capillary irradiated under similar conditions (Figure 2A). While the observed acceleration by af actor of two is impressive,i td oes not compare to the fivefold acceleration predicted by the Monte Carlo simulations for the device (see the Supporting Information).…”

A compact photomicroreactor design for kinetic studies of gas‐liquid photocatalytic transformations

“…In the following study of reaction kinetics, the operational zone without the mass transfer limitation (cf., Zone 1 in Figure b) and the volumetric flow rate of gas to liquid phase of 3 were chosen where V c is the volume of capillary microreactor, Q G,in and Q G,out are the inlet and outlet volumetric flow rates of gas phase based on the atmospheric pressure, P in and P out are the inlet and outlet pressures in the capillary microreactor, and Q L is the volumetric flow rate of liquid phase, is the original concentration of thiophenol in the reaction mixture, R is the gas constant, and T is the reaction temperature. Based on the knowledge of hydrodynamics and mass transfer for Taylor flow in microchannels or in capillaries and the physical properties (e.g., , diffusivity of oxygen in ethanol), we can approximately calculate the concentration of oxygen in the liquid phase in this photocatalytic process. For example, the liquid side volumetric mass transfer coefficient ( k L a ) is about 1 s −1 when the flow rates of gas and liquid phase are 900 μL/min and 300 μL/min ( t = 58 s) respectively.…”

Continuous synthesis of tetraalkylammonium‐Based ethyl sulphate ionic liquid and its kinetic study in microreactors

“…The calculated value of Pe varied from 1.06 × 10 3 to 2.38 × 10 4 when the volumetric flow rate was in the range of 0.156–2.34 mL/min with the temperature ranging from 40 °C to 90 °C, illustrating that the molecular diffusion dominated the mass transport compared to the convection under most of involved operational conditions ( Pe < 10 4 ). However, Pe increased with the increase in the flow velocity and in particular the viscosity of the reaction mixture raised significantly, and thus the mixing became more convection‐dominated ( Pe > 10 4 ) . Meanwhile, the Bodenstein number ( Bo ) describes the ratio of the convective transport rate to the axial diffusion rate in a dispersion model.…”