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The fluid mechanics of tensioned web roll coating
Shibata, Yusuke Ito, K.
Shibata, Yusuke
Ito, K.
Publication Date
2021
End of Embargo
Supervisor
Rights
© 2021 Elsevier. Reproduced in accordance with the publisher's self-archiving policy. This manuscript version is made available under the CC-BY-NC-ND 4.0 license.
Peer-Reviewed
Yes
Open Access status
openAccess
Accepted for publication
2021-03-22
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Department
Awarded
Embargo end date
Additional title
Abstract
Tensioned web-roll coating is widely used but has surprisingly received little research attention. Here, a new semi-empirical model that predicts film transfer from applicator roller to web is developed and tested against data collected from a pilot coating line. The film transfer is found to vary linearly with web to applicator speed ratio S. Flow stability investigations revealed three types of defects: rivulets, air entrainment due to dynamic wetting failure and cascade, occurring at different values of S and capillary number Ca. Rivulets occurred at Ca< 0.4 and S> 0.71-0.81, air entrainment at Ca>0.4 and S>0.71-0.83 and cascades at S>1.1 for Ca up to 6. Web speeds at which dynamic wetting failure occurred were, for the same Ca, comparatively higher than those that occur in dip coating. The data show that such hydrodynamic assistance is due to the coating bead being confined, more so with increasing web wrap angle β.
Version
Accepted manuscript
Citation
Benkreira H, Shibata, Y and Ito K (2021) The fluid mechanics of tensioned web roll coating. Chemical Engineering Science. 239: 116612.
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Type
Article