Evripidou, Nikola;
(2024)
Semi-Empirical Modelling of Separating Dispersed Pipe Flows.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
This thesis introduces a one-dimensional semi-empirical model predicting flow pattern transitions in separating dispersed liquid-liquid horizontal pipe flows. Based on the mechanisms of drop settling, drop-interface coalescence, and drop-drop coalescence, the model captures the evolution of distinct layers and the drop growth in oil-in-water and water-in-oil systems. Model validation uses experimental data for oil-in-water dispersions from a pilot scale two-phase flow facility. The separation dynamics were influenced by drop settling and coalescence rates. Oil-in-water dispersions separated faster than water-in-oil dispersions, higher mixture velocities increased the separation length, while smaller drops led to dense-packed layer depletion and longer separation lengths. A comparative analysis of two coalescence models, the asymmetric film drainage model (Henschke et al. 2002) and the interfacial mobility film drainage model (Jeelani and Hartland 1994), is carried out. Parameter estimates for the asymmetric film drainage model exhibit sufficient precision and good agreement with experimental measurements. In contrast, the interfacial mobility film drainage model exhibits dependency on mixture velocity, with substantial discrepancies between model predictions and experimental data when parameter estimates obtained at lower mixture velocity are used for higher mixture velocities. Consequently, the asymmetric film drainage model emerges as the preferred choice. Parameter estimation, parametric sensitivity analysis (PSA) and model-based design of experiments (MBDoE) are carried out to acquire precise parameter estimates and propose optimal experimental conditions, thereby enhancing the accuracy of the model. These studies utilize experimental data from Pereyra et al. (2013). PSA reveals regions of high sensitivity of the model outputs to uncertain parameters, which correspond to favourable sampling locations. Manipulating mixture velocity, dispersed phase fraction, and layer heights at the inlet, influences these sensitive regions. Clustered measurements around highly sensitive regions enhance the information content they provide. MBDoE demonstrates that A-, D-, or E-optimal experimental design criteria improve the expected parameter precision.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Semi-Empirical Modelling of Separating Dispersed Pipe Flows |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2024. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10187667 |
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