Lookup NU author(s): Andrew Tait,
Dr Jonathan Lee,
Professor Gary Montague
This is the authors' accepted manuscript of an article that has been published in its final definitive form by Institution of Chemical Engineers, 2019.
For re-use rights please refer to the publisher's terms and conditions.
© 2019 Institution of Chemical Engineers The freezing of a stream of free-falling monodispersed droplets was simulated through the development of numerical models in this work. Prediction of the freezing time and temperature transition of a single droplet is beneficial for optimisation of novel continuous spray freeze drying (cSFD) processes. Estimations of the vertical free-falling distance of the droplets in a slip stream and predictions of the chances of droplet coalescence greatly enhance process understanding and can be leveraged to direct equipment design and process development. A design space of droplet diameters in the range from 100 μm to 400 μm and ambient temperatures from −120 °C to −40 °C was explored. The rate of supercooling within the design space was predicted to range from 48 to 830 °C s −1 depending on the ambient temperature and droplet size. A comparison of the vertical free-falling distances of solitary droplets and streams of droplets at different temperatures showed that the terminal velocity of a vertically falling stream of droplets is always in excess of the terminal velocity of a solitary droplet of the same size. A difference of 1.35 m was predicted for the free-falling distance of a 400 μm droplet compared to a stream of droplets at −42 °C. A comparison between flow rates for consecutively generated 100 μm droplets showed that droplet coalescence was predicted at 0.05 Lh −1 , whilst at 0.02 Lh −1 a separation distance of 23 μm was maintained thus preventing coalescence.
Author(s): Tait A, Lee JGM, Williams BR, Montague GA
Publication type: Article
Publication status: Published
Journal: Food and Bioproducts Processing
Print publication date: 01/07/2019
Online publication date: 27/04/2019
Acceptance date: 22/04/2019
Date deposited: 04/07/2019
ISSN (electronic): 0960-3085
Publisher: Institution of Chemical Engineers
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