Controlling gas–liquid segment length in microchannels using a high-speed valve

Abstract

Segmented flow, one of the most important flow patterns in microchannels, has been widely employed in gas–liquid microreactor systems because it enhances mass transfer through the biphasic interface. The segment length is determined by the channel parameters (e.g., size, material type), fluid flow rate, and fluid properties. Thus, it is difficult to manipulate the gas–liquid segment length without affecting the residence time of the fluid. In this work we successfully achieved regularly segment length control by introducing a high-speed valve into a gas–liquid microchannel system while varying the frequency of the valve installed in the gas-phase tube to allow gas and liquid segment lengths to be controlled within a large range. In contrast, the segment lengths were almost constant under the same conditions without the high-speed valve. Furthermore, a gas/liquid flow rate ratio in the range of 0.7–1.2 was deemed necessary for steady segmented flow. Finally, a correlation was proposed to predict the segment length using parameters such as valve frequency and fluid flow rate, and it matched the experimental data well. This segment length control strategy will improve the performance of gas–liquid reactions in microreactors and advance the design of microreactor systems.