Browsing by Author "Yeung, H."
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Item Open Access The application of signal analysis techniques based on chaos theory to flow regime identification.(1996-12) Rawes, W; Yeung, H.The aim of the research presented in this thesis has been to develop an objective measurement technique to improve the detection of flow patterns in closed ducts. This activity is important for the safe and efficient running of many processes, particularly within the oil production, nuclear power, chemical and process industries. Signal analysis techniques based on nonlinear dynamic (chaos) theory have been applied to simulated and experimental transducer signals measuring properties of gas-liquid (air-water) flows in horizontal and vertical pipes. The techniques provide a method of measuring properties of the signals that are related to patterns within the signals. Signals from various non-invasive transducers (including differential pressure transducers, an electrical conductance transducer, a light attenuation transducer, an ultrasonic transducer and a gamma-ray densitometer) have been analysed. Signal analysis techniques include the use of singular value decomposition, the correlation integral and power spectra analysis. The results of signal analysis on the simulated signals illustrate their potential for flow regime identification. When applied to experimental signals it is shown that changes in some of the signal characteristics correlate well with changes in the flow regimes. Discernment between horizontal stratified-wavy, plug and slug and vertical slug and bubbly flow regimes has been achieved. The most successful analysis technique (using singular value composition) is more robust than previously used techniques and can be computed much more efficiently.Item Open Access Estimating slug liquid holdup in high viscosity oil-gas two-phase flow(Elsevier, 2018-10-29) Archibong-Eso, Archibong; Okeke, Nonso Evaristus; Baba, Yahaya D.; Aliyu, Abdulkabir; Lao, Liyun; Yeung, H.Slug flow is one of the most critical and often encountered flow patterns in the oil and gas industry. It is characterised by intermittency which results in large fluctuations in liquid holdup and pressure gradient. A proper understanding of its parameters (such as slug holdup) is essential in the design of transport facilities (e.g. pipelines) and process equipment (slug catchers, separators etc.). In this paper, experimental investigation of slug liquid holdup (defined as the liquid volume fraction in the slug body of a slug unit) is performed. Mineral oil with viscosity, μ=−0.0043T3+0.0389T2−1.4174T+18.141 and air were used as test fluids. A 0.0254 m and 0.0762 m pipe internal diameters facilities with pipe lengths of 5.5 and 17 m respectively were used in the study. Electrical Capacitance Tomography was used for slug holdup measurements. Results obtained in the study shows that slug liquid holdup varied directly as the viscosity and inversely as the gas input fraction. Existing slug holdup correlations and models in literature did not sufficiently predict present experimental results. A new empirical predictive correlation for estimating slug liquid holdup was derived from present experimental databank and from data obtained in literature. The databank's liquid viscosity ranges from 0.189 – 8.0 Pa.s. Statistical analysis of the new correlation vis-à-vis existing ones showed that the present correlation gave the best performance with an average percent error, E1; absolute average percent error, E2 and standard deviation, E3 of 0.001, 0.05 and 0.07 respectively, when tested on the high viscosity liquid–gas databank.Item Open Access Interfacial friction in upward annular gas–liquid two-phase flow in pipes(Elsevier, 2017-02-17) Aliyu, A. M.; Baba, Yahaya D.; Lao, Liyun; Yeung, H.; Kim, K. C.Accurate prediction of interfacial friction between the gas and liquid in annular two-phase flow in pipes is essential for the proper modelling of pressure drop and heat transfer coefficient in pipeline systems. Many empirical relationships have been obtained over the last half century. However, they are restricted to limited superficial liquid and gas velocity ranges, essentially apply to atmospheric pressures, and the relationships are only relevant for pipes with inner diameters between 10 and 50 mm. In this study, we carried out experiments in a large diameter flow loop of 101.6 mm internal diameter with the superficial gas and liquid ranges of 11–29 m/s and 0.1–1.0 m/s respectively. An examination of published interfacial friction factor correlations was carried out using a diverse database which was collected from the open literature for vertical annular flow. The database includes measurements in pipes of 16–127 mm inner diameter for the liquid film thickness, interfacial shear stress, and pressure gradient for air-water, air-water/glycerol, and argon-water flows. Eleven studies are represented with experimental pressures of up to 6 bar. Significant discrepancies were found between many of the published correlations and the large pipe data, primarily in the thick film region at low interfacial shear stress. A correlation for the interfacial friction factor was hence derived using the extensive database. The correlation includes dimensionless numbers for the effect of the diameter across pipe scales to be better represented and better fit the wide range of experimental conditions, fluid properties, and operating pressures.Item Open Access Investigation and prediction of slug flow characteristics in highly viscous liquid and gas flows in horizontal pipes(Elsevier, 2015-06-18) Zhao, Y.; Lao, Liyun; Yeung, H.Slug flow characteristics in highly viscous liquid and gas flow are studied experimentally in a horizontal pipe with 0.074 m ID and 17 m length. Results of flow regime map, liquid holdup and pressure gradient are discussed and liquid viscosity effects are investigated. Applicable correlations which are developed to predict liquid holdup in slug body for low viscosity flow are assessed with high viscosity liquids. Furthermore, a mechanistic model is developed for predicting the characteristics of slug flows of highly viscous liquid in horizontal pipes. A control volume is drawn around the slug body and slug film in a slug unit. Momentum equations with a momentum source term representing the significant momentum exchange between film zone and slug body are applied. Liquid viscosity effects are considered in closure relations. The mechanistic model is validated by comparing available pressure gradient and mean slug liquid holdup data produced in the present study and those obtained from literature, showing satisfactory capabilities over a large range of liquid viscosity.