3D investigations of microscale mixing in helically coiled capillaries

Abstract

In capillary reactors, improving radial mixing and narrowing the residence time distribution is of great importance for high selectivity and reaction performance. A well-known approach is inducing secondary flow patterns by coiling the capillary around a cylinder. To increase understanding of transport phenomena in helically coiled capillaries non-invasive 3D imaging approaches are required. In this perspective paper, we introduce X-ray-based micro-computed tomography for the investigation of dispersion of iodide in a helically coiled tube. The methodology presented here allows for the direct evaluation of radial concentration fields. By varying Dean number $$Dn$$ D n and modified torsion parameter $${T}^{*}$$ T ∗ , the effect of torsion and curvature on the radial concentration profile can be identified. Detailed knowledge of local radial mixing in helically coiled capillaries will help the precise prediction of reaction progress and selectivity. Graphical abstract

X‐Ray‐Based Tomographic Imaging for the Investigation of Laminar Mixing in Capillaries

“…Recently, Kova ´ts et al applied laser-induced fluorescence to visualize concentration fields of a fluorescent dye at different angles of revolution [21]. So far, studies on X-raybased computed tomography for the investigation of processes on the milli-to micro-scale are still rare [22] and only very few studies concern the direct investigation of mass transfer [23][24][25].…”

Chemical and Process Engineering

“…A recent example of this type of research is a work of Kováts et al (2020), who studied mixing in different coil flow inverters using a fluorescent dye and concluded that an early flow redirection speeds up mixing. On the other hand, Schuler et al (2021) used X-ray based microcomputed tomography to identify the effect of torsion and curvature of a helical capillary on the evolution of radial concentration profiles of iodine tracer. Studies using mixing sensitive chemical probes are not as popular as the passive tracer methods, but they can provide valuable data on mixing at the molecular scales.…”