Seamless scale‐up of tube‐in‐tube millireactors by annular structure and feed method design: Micromixing, residence time distribution and heat transfer

Abstract Flow chemistry is widely valued for its enhanced transport properties and safety, but scaling up while maintaining the advantages of the microenvironment in small‐scale systems remains challenging. We addressed this by developing a novel tube‐in‐tube millireactor with a multi‐hole jet inlet and deflectors, designed to maintain consistent flow regimes and optimize micromixing, residence time distribution ( RTD ), and heat transfer at various scales. The reactor increases flux by enlarging tube diameters and incorporating micro‐holes and deflectors, all while maintaining a constant annular space. This design, validated through both CFD modeling and experimental results, maintains consistent fluid flow and excellent transfer properties, achieving micromixing time below 2 ms at Re h > 2000, a plug‐flow‐like RTD profile, and a heat transfer capacity up to 12.4 times greater than conventional designs. This study presents a simple, scalable approach to millireactor design, combining “number‐up” and “size‐up” strategies, offering a cost‐effective solution for industrial applications.