Local investigations of gas-liquid mass transfer around Taylor bubbles flowing in straight and meandering millimetric channels using a colorimetric method

Résumé

Compact Heat-EXchanger reactors (HEX) are an important part of process intensification technology. However, most of the existed research dealing with such type of equipment has been focused on the application of one-phase reactive flows. For gas-liquid reactions, few investigations have been out carried. This thesis aims at locally studying gas-liquid mass transfer around Taylor bubbles flowing in straight and meandering millimetric channels using a colorimetric method; this is a preliminary step essential before implementing two-phase reactive systems. Firstly, the occurrence of a possible enhancement of the gas-liquid mass transfer by the chemical reaction involved was investigated. Secondly, the gas-liquid mass transfer occurring in Taylor flows right after the bubble formation stage in a microreactor was studied. Thirdly, the gas-liquid hydrodynamics were characterized and the effects of bends on the mass transfer mechanism were locally investigated in a millimetric meandering channel. At last, a rigorous comparison could be made between the meandering and straight channels. It showed how and why the meandering geometry leads to intensify gas-liquid mass transfer. All these findings enabled to formulate a scaling law, expressed in terms of Sherwood, Graetz and Péclet numbers, able to describe the evolution of gas-liquid mass transfer as a function of axial position and operating conditions.

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