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Characterisation and modelling of Taylor flow in small circular channels for the purpose of sequential screening

Salman, W'el; (2005) Characterisation and modelling of Taylor flow in small circular channels for the purpose of sequential screening. Doctoral thesis , UCL (University College London). Green open access

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Abstract

This work focuses on the characterisation of a commonly encountered flow pattern, Taylor flow, for the purpose of using it in high throughput experimentation (HTE). Taylor flow consists of elongated gas bubbles of equivalent diameter larger than the tube diameter separated by liquid slugs. The bubbles adopt a characteristic capsular shape almost entirely filling the channel cross section. This configuration enhances the mixing within the liquid slugs and significantly decreases axial mixing along the liquid compared to single phase liquid flow. In this work, the characterisation of a Taylor flow reactor was divided into three parts: The first part deals with the hydrodynamics of the flow, identifying the dimensionless parameter governing Taylor flow and the size of forming bubbles in a coaxial inlet arrangement. One of the findings was that a minimum channel size 100 mum exists below which the Taylor flow may becomes non-periodic or unstable. The experimentally observed mechanisms of Taylor bubble formation are reported and a simple model is provided for predicting the most common of the mechanisms. In the second part, two models were developed which enable the prediction of axial mixing and the residence time distribution curves of the Taylor flow reactor. The first model is applicable when Peclet numbers Pe 100. It was used to evaluate existing literature models and then for determining the rate of mixture injection in HTE. The second model is a special extension of the first applicable when Pe 1000 and accounts for forward as well as back mixing. In the third part a model was developed for identifying the flow rates and channel and slug lengths in the Taylor reactor which allow its use for determining kinetics of chemical reactions. An important finding from both axial and the kinetics models is that the slug lengths should be kept to the minimum possible size for best reactor performance.

Type: Thesis (Doctoral)
Title: Characterisation and modelling of Taylor flow in small circular channels for the purpose of sequential screening
Identifier: PQ ETD:602701
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering
URI: http://discovery.ucl.ac.uk/id/eprint/1446770
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