Newtonian and non-Newtonian two-phase flow in complex pipelines

Ben Rajeb, Faraj Ali (2024) Newtonian and non-Newtonian two-phase flow in complex pipelines. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Two-phase gas/non-Newtonian fluid flow through pipes commonly occurs in many industrial applications, such as in the chemical industry and oil and gas refineries. Many fluids used in oil and gas industries display non-Newtonian behaviour. Their rheology strongly affects pressure drop, flow structure, interface fluctuation, void fraction, heat transfer, and other flow features. In fact, non-Newtonian systems are not governed by the Newtonian law of viscosity. However, little experimental work has been devoted to studying non-Newtonian flow behaviour. This present work has conducted an experimental investigation to understand the fundamental physics of non-Newtonian two-phase (gas/ liquid) flow through pipes. In the experiments, several concentrations of Xanthan Gum were used as the non-Newtonian liquid, and both compressed air and carbon dioxide were used as gases. The flow rate and pressure of liquid and gas are changed by using a pump placed ahead of the mixing point. Pressure values are recorded by pressure sensors fixed at specific points along the pipe loop, and more than 10,000 experimental data points have been collected. The Experimental data analysis went through four categories. The first part is to calibrate all pressure sensors. The second step was applying rheology tests on our non-Newtonian Fluid to define the fluid behaviour and estimate the fluid properties. The third goal is to develop a new model for estimating pressure drop for the gas/non-Newtonian flow. The last part of the experiments is void fraction measurements. Pressure drop is one of the most challenging concerns related to industrial process design. In fact, multiphase flow process design depends on a better understanding of multiphase flow regimes. Numerous research has been done on gas/Newtonian liquid flow in horizontal and vertical pipes in the past few decades. Still, only a few research studies have been carried out to identify gas/non-Newtonian flow regimes. [1]. Creating a new model to estimate void fraction for gas-non-Newtonian flow is another objective done in the present work. The void fraction is considered one of the most important flow parameters used to describe two-phase flows in tubes. Void fraction is an important process variable for the volume and mass calculation required to transport gas-liquid mixture in pipelines, storage in tanks, metering, and custody transfer. Furthermore, it is important to determine other flow parameters such as two-phase density and viscosity or the average velocities of gas and liquid mixture. In addition, it plays a significant role in estimating and modelling two-phase pressure drop and flow pattern transitions. The created void fraction model is used to determine constants of general form posted by Butterworth[2]. Both developed void fraction models give a good estimation for the void fraction with about 5% percent errors compared with our experimental results and other available literature experimental results.

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