Experimental measurements and modeling of liquid-liquid Taylor flow in mini-scale tubing

Adrugi, Wesam (2019) Experimental measurements and modeling of liquid-liquid Taylor flow in mini-scale tubing. Doctoral (PhD) thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (4MB)

Abstract

Immiscible two-phase segmented flow in a mini / micro scale channel is a promising area for heat transfer enhancement. A segmented flow, also known as a slug flow, plug flow or Taylor flow is a series of moving liquid segments separated by a liquid medium. A literature review of the research reveals large gaps in the knowledge base of liquid-liquid Taylor flows and calls for further investigation. Earlier studies have reported that introducing two immiscible liquids into mini / micro scale channels significantly increases heat transfer rate. The main focus of this research is on modeling liquid-liquid Taylor flows using an experimental approach based on the concept of the internal fluid flow and a dimensionless analysis for reducing experimental data. The purpose of this study is to investigate the fluid dynamic and thermal characteristics of liquid-liquid Taylor flows in small-scale tubes that will lead to better understanding on this process. Therefore, the heat transfer and pressure drop in two-phase liquid-liquid Taylor flows inside mini-scale tubing have been examined using a wide range of geometrical and operational parameters such as Capillary number, Prandtl number and minichannel geometries. Proposed models for each of these geometries have been developed to predict the heat transfer behaviors and pressure drop for low Reynolds number flow conditions. The effect of internal circulation and boundary layer renewal within the flow components is clearly presented. Namely, it is shown that cause significant thermal enhancement. The intensity of these circulations is a function of different parameters, including the flow conditions, channel geometry, and liquids employed. The effects of all of these parameters on heat transfer and pressure drop have been studied experimentally and are presented in this dissertation. Furthermore, this study demonstrates how heat transfer enhancement results due to varying the slug lengths of each phase in the liquid-liquid Taylor flow. New experimental data for liquid-liquid Taylor flows in straight, curved, and coiled mini scale tubes were obtained using low viscosity silicone oils segmented by water at varying volume fractions. The results of this thesis are of fundamental and practical relevance for the analysis and design of small systems and devices incorporating liquid-liquid Taylor flow regimes. The novel results were obtained with carefully controlled flow cell slug lengths and volume fractions, which show a significant impact on the rate of laminar heat transfer and pressure drop. Analytical models for each of these geometries have been developed. Dimensionless heat transfer rate and pressure drop results show good agreement with proposed analytical models. The proposed models’ predictions for the heat transfer and pressure drop agree with the new experimental data within ± 20% or less.Liquid-Liquid Taylor Flow

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