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Oscillatory fluid motion unlocks plug flow operation in helical tube reactors at lower Reynolds numbers (Re ≤ 10)

Lookup NU author(s): Dr Jonathan McDonough, Dr Richard Law, Professor Adam Harvey

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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).


Abstract

Flow in helical tubes exhibits plug flow characteristics above a critical flow rate due to the formation of Dean vortices. In this study, we report the novel use of oscillatory flow inside coiled tubes to achieve high degrees of plug flow at lower flow rates. The plug flow enhancement appeared to ‘switch-on’ then ‘switch-off’ as the oscillation intensity was increased, corresponding to ‘oscillatory Dean numbers’ of Deo = 70–200, where secondary instabilities are expected. It is believed that oscillatory motion leads to the periodic formation and unravelling of Dean vortices. For a 5 mm tube diameter, the effects of radius of curvature (12.5–32.5 mm), tube pitch (7.5–12.5 mm), net flow rate (Ren = 10–50), oscillation frequency (2–8 Hz) and oscillation amplitude (1–8 mm) were studied. The prototype helical coil reactors were rapidly manufactured using 3D printing. The optimal conditions for plug flow corresponded to Deo/Ren = 2–8, at Strouhal numbers in the range St = 1–2. Plug flow was observed at net flow Reynolds numbers at least as low as Ren = 10, compared to Ren = 70–300 in the literature for coiled tubes subjected to steady flows.


Publication metadata

Author(s): McDonough JR, Murta S, Law R, Harvey AP

Publication type: Article

Publication status: Published

Journal: Chemical Engineering Journal

Year: 2018

Volume: 358

Pages: 643-657

Print publication date: 15/02/2019

Online publication date: 09/10/2018

Acceptance date: 07/10/2018

Date deposited: 11/10/2018

ISSN (print): 1385-8947

ISSN (electronic): 1873-3212

Publisher: Elsevier BV

URL: https://doi.org/10.1016/j.cej.2018.10.054

DOI: 10.1016/j.cej.2018.10.054


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