Experimental and numerical investigation on the influence of wall deformations on mixing quality of a Multifunctional Heat Exchanger/Reactor (MHER)

This study focuses on the mixing performance enhancement in laminar flow equipment by investigating the generation of chaotic advection using wall deformations in annular geometries. The results presented concern the mixing quality in two different geometries, one with a deformed sinusoidal wall "DT" (Deformed Tube), and the other with a combination of deformed sinusoidal external wall and a swirled core "DETSC" (Deformed External Tube and Swirled Internal Core). The goal is to evaluate the influence of the swirled core on the mixing, and to determine if this combination of wall deformations could improve the mixing quality for Reynolds numbers ranging from 800 to 2000. To provide a comprehensive analyse, the evaluation is conducted based on two aspects: the process engineering aspect, through experimental Residence Time Distribution (RTD) to gain an overview of the dispersion of fluid particles in the reactors, and the fluid mechanics aspect, using various numerical tools such as the mixing rate, Poincare sections, and particle trajectories to better analyse the secondary flows resulting from wall deformations and assess the mixing in terms of concentration. These two aspects allow to characterize the mixture globally and locally. The findings demonstrated that the combined geometry induced chaotic advection, resulting in a perfect mixing rate of 100% across the entire range of Reynolds numbers studied, compared to the DT configuration where the maximum achieved mixing rate reaches 70% at Re = 2000.