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Numerical analysis of in-flight freezing droplets: Application to novel particle engineering technology

Lookup NU author(s): Andrew Tait, Dr Jonathan Lee, Professor Gary Montague

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This is the authors' accepted manuscript of an article that has been published in its final definitive form by Institution of Chemical Engineers, 2019.

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Abstract

© 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.


Publication metadata

Author(s): Tait A, Lee JGM, Williams BR, Montague GA

Publication type: Article

Publication status: Published

Journal: Food and Bioproducts Processing

Year: 2019

Volume: 116

Pages: 30-40

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

URL: https://doi.org/10.1016/j.fbp.2019.04.009

DOI: 10.1016/j.fbp.2019.04.009


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