Experimental And Numerical Investigation Of Mass Transfer In Microreactors

Abstract

In this work, two types of microreactors for reactions have been studied, which were involving multiple fluid phases: liquid-liquid (immiscible liquids) phase and gas-liquid phase. Investigation of mass transfer within reacting flows in microreactors has been carried out in these two multiphase systems. For the liquid-liquid phase, a microfluidic system was designed and fabricated to generate a slug flow pattern of immiscible liquids. This system was used to demonstrate the effect of the flow pattern on mass transfer and the effect on chemical reaction rate for a simple acid-base reaction. The reaction progression was tracked by measuring the pH along the length of the microchannel. A detailed mathematical model included mass transfer and reaction kinetics was constructed and solved numerically using computational fluid dynamics software. The kinetic rate constant was determined from the experiment data using an optimization algorithm. A good match between experimental results and numerical model was obtained. For the gas-liquid studies, a microfluidic device that consists of a microporous polymer membrane and microchannels has been designed and fabricated. The device was used to test mass transfer from gas to liquid water phase for both oxygen and carbon dioxide. The correlated Sherwood number was presented for different average flow velocity. The impact of channel geometry and residence time on reaction completeness was also measured for carbon dioxide reacting with an aqueous alkaline solution. The experiment results were compared with a numerical model solved with computational fluid dynamics software. Potential application of the developed devices and their results include compact units for carbon dioxide capture from gas mixtures and portable blood oxygenators.