Loughborough University
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A factorial approach to understanding the effect of inner geometry of baffled meso-scale tubes on solids suspension and axial dispersion in continuous, oscillatory liquid-solid plug flows

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journal contribution
posted on 2016-09-29, 10:24 authored by Louisa Ejim, Stephanie Yerdelen, Thomas McGlone, Iyke Onyemelukwe, Blair Johnston, Alastair J. Florence, Nuno Reis
Oscillatory flow reactors (OFRs) are a new generation of tubular mixing and reaction equipment uniquely capable of combining continuous near plug flow with homogeneous particle suspension, yet the design of OFRs for liquid-solid and multi-phase flow processes relies on rules established during the past two decades from single, liquid-phase studies. A Design of Experiment (DoE) approach was herein implemented for establishing the relationship between four key geometrical parameters of the inner tube baffles and both the suspension of particles and the axial dispersion for liquid-solid continuous flows in 10 mm internal diameter (d) meso-scale tubes with periodic baffles. The parameters evaluated were the orifice open diameter, do = 0.35d–0.50d; the open cross section, a = 0.12d–0.25d, constriction spacing, l = 1.5d–3.0d, and baffle shape (sharp vs smooth edged). A total of ten tubes were tested, five consisting of smooth periodic constrictions (SPC) and the other five of sharp edged periodic constrictions (SEPC) according to a complete 2×2 factorial design with 1 central point. Each tube was experimentally evaluated via optical imaging of suspended monodispersed polyvinyl chloride (PVC) particles. Both SPC and SEPC meso-tubes were capable of delivering a near plug behaviour and the values of axial dispersion coefficient (Dc) estimated for the solids were in the range of 1.0–2.2×10-4 m2 s-1. In contrast, the minimum (critical) fluid oscillation conditions required for full suspension of particles varied significantly, in general with the SPC tubes requiring up to 50 % lower amplitude for full particles suspension. Overall, a revealed the dominant parameter in controlling solids backmixing and, and the inner tube geometry requiring the lowest energy input for homogenous particle suspension and minimum Dc (i.e. sharpest residence time distribution) presented a l/d = 3, do = 0.35d, a = 12 % and SPC design. This study is believed to support the future design of optimised meso-scale OFR systems for continuous screening and manufacturing of value-added liquid-solid and multi-phase systems, such as catalytic and crystallisation processes.


This work was supported under EPSRC awards EP/I0334 59/1 (Centre for Innovative Manufacturing in Continuous Manufacturing and Crystallisation) and EP/K503289/1 (Doctoral Training Centre in Continuous Manufacturing & Crystallisation. These are in association with a UKRPIF (UK Research Partnership Institute Fund) capital award from the Higher Education Funding Council for England (HEFCE).



  • Aeronautical, Automotive, Chemical and Materials Engineering


  • Chemical Engineering

Published in

Chemical Engineering Journal


EJIM, L.N. ...et al., 2017. A factorial approach to understanding the effect of inner geometry of baffled meso-scale tubes on solids suspension and axial dispersion in continuous, oscillatory liquid-solid plug flows. Chemical Engineering Journal, 308, pp.669-682


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This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

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This paper was accepted for publication in the journal Chemical Engineering Journal and the definitive published version us available at http://dx.doi.org/10.1016/j.cej.2016.09.013.




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