Mass transfer enhancement in microchannel reactors by reorientation of fluid interfaces and stretching

The poor mixing in microchannel reactors, most especially in liquid-phase reactions, primarily due to the inherently diffusion-dominated laminar flow characteristic of microreactors has attracted the attention of many researchers. The aim of this research study is to investigate mass transfer enhancement in microchannel reactors, through a theoretical mixing study of the currently utilized standard, single-channel T-junction configuration as well as four proposed multi-channel, microreactor configurations. The mass transfer enhancement in the proposed configurations is achieved via 'reorientation and stretching of fluid interfaces' by imposing some geometric constraints on these microreactor configurations. These configurations are studied for their mixing performance by performing computational fluid dynamics (CFD) simulations of pulse tracer and flow visualization experiments, and using residence time distribution (RTD) and species mass fraction distribution (SMFD) as mixing characterization measures, respectively. Based on the criteria of low pressure drop as well as high mixing performance, the best enhanced-mixing configuration is identified and subsequently optimized. This theoretical study on laminar mixing problem in micromixers/reactors shows CFD simulations as a very useful tool for the design and optimization of micromixing/reaction configurations.