Francia, V, Martin, L, Bayly, AE orcid.org/0000-0001-6354-9015 et al. (1 more author) (2015) Influence of wall friction on flow regimes and scale-up of counter-current swirl spray dryers. Chemical Engineering Science, 134. pp. 399-413. ISSN 0009-2509
Abstract
The structure of the vortex flow in swirl spray dryers is investigated after having fouled the walls with deposits typical of detergent manufacture. The range of Re and swirl intensity Ω characteristic of industry are studied using three counter-current units of varying scale and design. The friction with the deposits increases the flow turbulence kinetic energy and causes a drastic attenuation of the swirl and as a result, the vortex breaks down in the chamber forming recirculation regions (i.e. areas of reverse flow). Three flow regimes (1) no recirculation, (2) central and (3) annular recirculation have been identified depending on the swirl intensity. New control and scale up strategies are proposed for swirl dryers based in predicting the decay and the flow regime using the unit geometry (i.e. initial swirl intensity Ω<inf>i</inf>) and experimental decay rates function of the coverage and thickness of deposits. The impact in design and numerical modelling must be stressed. Adequate prediction of the swirl is vital to study fouling and recirculation, which surely play an important part in the dispersion and aggregation of the solid phase. Current models have no means to replicate these phenomena, and yet, in this case neglecting the deposits and assuming smooth walls would result in (a) over-prediction of swirl velocity up to 40-186% (b) under-prediction of turbulent kinetic energy up to 67-85% and (c) failure to recognise recirculation areas.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2015 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). |
Keywords: | Spray drying; vortex flow; scale up; roughness; recirculation; swirl decay |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemical & Process Engineering (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 21 Aug 2015 09:55 |
Last Modified: | 27 Oct 2020 15:20 |
Published Version: | http://dx.doi.org/10.1016/j.ces.2015.04.039 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.ces.2015.04.039 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:89188 |