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Experimental study of the factors affecting the flow pattern transition in horizontal oil-water flow

EXPERIMENTAL THERMAL AND FLUID SCIENCE 2018年 98卷 534-545页

作者： Tan, Jiatong Jing, Jiaqiang Hu, Haili You, Xiangyang Southwest Petr Univ State Key Lab Oil & Gas Reservoir Geol & Exploita 8 Xindu Ave Chengdu 610500 Sichuan Peoples R China Oil & Gas Fire Protect Key Lab Sichuan Chengdu 611731 Sichuan Peoples R China

flow patterns are important for pressure gradient calculation and corrosion protection. In this study, the characteristics of oil-water flow were investigated in a horizontal acrylic pipe with an inner diameter of 14.6 mm. The effects of oil viscosity, pipe diameter, pipe material and oil type were studied. Mineral oils with viscosity values of 20, 237 and 456 mPa.s were used as the working fluids. The flow patterns were identified by a high-speed camera and pressure gradients. The size of the dispersed oil droplets increased with increasing oil viscosity. The mixture velocity required to initiate ST&MI flow from SS flow increased with increasing oil viscosity. The transition boundaries extended to high velocities with increasing pipe diameter. In large-diameter pipes, the low-viscosity oil-water flow patterns were stratified flow, dispersed flow and their transition flow, and the high-viscosity oil-water flow patterns were annular flow in addition to these other flows. In small-diameter pipes, stratified flow, dispersed flow, annular flow and intermittent flow patterns were found for both low- and high-viscosity oil-water flow.

关键词： Oil-water flow flow pattern map flow pattern transition Viscosity

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Uncertainty quantification and global sensitivity analysis of mechanistic one-dimensional models and flow pattern transition boundaries predictions for two-phase pipe flows

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INTERNATIONAL JOURNAL OF MULTIPHASE flow 2017年 90卷 64-78页

作者： Picchi, Davide Poesio, Pietro Univ Brescia Dipartimento Ingn Meccan & Ind Via Bronze 38 I-25123 Brescia Italy Tel Aviv Univ Fac Engn Sch Mech Engn IL-69978 Tel Aviv Israel

The prediction of uncertainties is a growing interest in flow assurance industrial applications, but only few works have been presented on this topic. In this work, an uncertainty quantification and a global sensitivity analysis are performed to quantify the level of confidence in predictions of one-dimensional mechanistic models considering different two-phase flow regimes. A method is proposed for this purpose accounting for the effect of several variables on pressure drop and hold-up predictions by the well-known one-dimensional two-fluid model, such as fluid flow rates, geometry (the inclination angle and the pipe diameter), and fluid properties (density and viscosity);the case of a non-Newtonian shear-thinning fluid behaviour is also considered. flow pattern transition boundaries, including the stability of the stratified flow regime, are included in this analysis. Monte Carlo simulations were used for the uncertainty quantification while different approaches for the sensitivity analysis (scatter plot, linear regression, the Morris's method, and the Sobol's Method) were used and compared to identify the best tool for this family of models. The Sobol's method appears to be the most convenient approach and a discussion is provided considering different practical cases for gas/liquid and liquid/liquid systems. The most critical input parameters in terms of uncertainty are rigorously identified case by case. A way to reduce the output uncertainty is indicated by the interpretation of the results of the global sensitivity analysis. The conclusions of this analysis gives new insights regarding the degree of uncertainties in predictions of one-dimensional mechanistic models. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Uncertainty quantification Sobol's indices Two-fluid model Confidence level Pressure drop flow pattern transition

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Two-Dimensional Numerical Simulation for flow pattern transition of Thermal-Solutal Capillary Convection in an Annular Pool

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MICROGRAVITY SCIENCE AND TECHNOLOGY 2013年第4期25卷 225-230页

作者： Li, You-Rong Zhou, Yong-Li Tang, Jing-Wen Gong, Zhen-Xing Chongqing Univ Coll Power Engn Key Lab Low Grade Energy Utilizat Technol & Syst Minist Educ Chongqing 400044 Peoples R China

In order to understand the transition characteristics of the thermal-solutal capillary convection in an annular pool, a series of two-dimensional numerical simulations were conducted. The bottom of the pool is adiabatic rigid wall and the top is adiabatic and non-deformable free surface. The inner and outer cylindrical walls maintain at constant temperature and solute concentration, respectively. The thermo-capillary force is supposed to equal to the solute-capillary force, but their directions are contrary. Results show that the thermal-solutal capillary convection is steady at a small Reylonds number. When the capillary Reynolds number exceeds a critical value, the steady flow transits into unstable thermal-solutal capillary convection. The transition from the steady to oscillatory flow undergoes a Hopf bifurcation. Furthermore, the effects of the liquid layer aspect ratio, the radius ratio, the Prandtl number and the Lewis number on the onset of flow pattern transition are discussed. The physical mechanism of the unstable thermal-solutal capillary convection is also analyzed.

关键词： Thermal-solutal capillary convection flow pattern transition Annular pool Numerical simulation

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Numerical research on relationship between flow pattern transition and condensation heat transfer in microchannel

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ENGINEERING COMPUTATIONS 2014年第5期31卷 939-956页

作者： Sun, Dongliang Xu, Jinliang Ding, Peng North China Elect Power Univ State Key Lab Alternate Elect Power Syst Renewabl Beijing Peoples R China North China Elect Power Univ Beijing Key Lab Multiphase Flow & Heat Transfer L Beijing Peoples R China China Univ Petr Hua Dong Coll Storage & Transportat & Architectural Engn Qingdao Peoples R China

Purpose - Based on the numerical research on the relationship between the flow pattern transition and the condensation heat transfer in circular microchannels, the purpose of this paper is to bring forward a concept of external separation circular microchannel to regulate and control the flow pattern for enhancing the condensation heat transfer. Design/methodology/approach - The numerical research is based on the volume of fluid method and the vapor-liquid phase change model proposed by the present authors. Findings - By numerical research on the condensation process of water in a general circular microchannel, it is discovered that, with the increase of the inlet velocity and the reduction of the temperature difference between the saturation temperature and the channel wall temperature, the bubble detachment frequency is raised and the water vapor condensation length is extended, representing an exponential growth. Therefore, for the condensation process with low temperature difference and high mass flow rate, it is in urgent need to regulate and control the flow pattern. Originality/value - To prevent the flow pattern in the general circular microchannel converted from annular flow to slug flow and then to bubble flow, this paper brings forward a concept of external separation circular microchannel, which regulates and controls the flow pattern by discharging partial liquid from the annular wall opening. After regulation and control, the flow pattern is converted from original periodic annular flow/slug flow/bubble flow to current stable annular flow. Accordingly, the heat transfer performance is enhanced and the condensation length is lowered remarkably.

关键词： Condensation heat transfer flow pattern transition Microchannel VOF

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Analysis of flow pattern transition from segregated to slug flow in upward inclined pipes

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INTERNATIONAL JOURNAL OF MULTIPHASE flow 2019年 115卷 19-39页

作者： Fan, Yilin Pereyra, Eduardo Sarica, Cem Schleicher, Eckhard Hampel, Uwe Colorado Sch Mines Petr Engn Dept Golden CO 80401 USA Univ Tulsa McDougall Sch Petr Engn Tulsa OK 74104 USA HZDR Inst Fluid Dynam Dresden Germany

Segregated and slug flows are two of the most common flow patterns encountered in two-phase upward inclined pipe flow. However, the transition between them is ambiguous. Coherent and distinctive structures have been observed within the transition. These structures have been classified as pseudo-slug flow. The nature of pseudo-slug flow is not well understood due to the complexity of the structure. At low liquid loading conditions, this flow pattern can occupy a large operating region and cannot be neglected. This paper presents a detailed experimental work conducted in a facility with a valley configuration, focusing on the transition region between segregated and slug flows. Wire-mesh sensors were employed to investigate the liquid phase distribution within the flow structure. The current paper investigates the flow patterns and their transition in upward inclined pipe from different perspectives. The investigation includes analysis of images from high-speed videos, evaluation of 2-D liquid holdup axial evolution, 2-D liquid holdup distribution at pipe cross-section, 3-D interfacial structure evolution, and analysis of pressure gradient and liquid holdup measurement, flow characteristics, etc. Differences between slug and pseudo-slug flows are also presented. Three superficial liquid velocities (0.001, 0.005 and 0.01 m/s) and five inclination angles (2 degrees, 5 degrees, 10 degrees, 15 degrees, and 20 degrees) are studied. Simplified correlations are proposed for pseudo-slug structural velocity, showing fair agreement. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Pseudo-slug flow flow pattern transition Two-phase flow in inclined pipe Wire-mesh sensor Low liquid loading

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Experimental study on flow instability for downward flow in a narrow rectangular channel with flow pattern transition

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INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER 2020年 114卷

作者： Zhang, Xue Feng, Wenpei Zhang, Jie Guo, Simao Ding, Wenjie Chen, Hongli Univ Sci & Technol China USTC Dept Engn & Appl Phys Hefei Anhui Peoples R China China Acad Engn Phys Inst Nucl Phys & Chem Mianyang Sichuan Peoples R China

The flow instability of downward flow in a narrow rectangular channel was experimentally investigated with visualization under low pressure, low speed flow and two-side heated conditions. The onset of flow instability (OFI) was obtained by decreasing the flow rate with constant heating power and occurred at the lowest point of the pressure drop-mass flow rate curve. It was found that decreasing the inlet temperature and heating power or improving the pressure can stabilize the system. Besides, the flow pattern transition at OFI was divided into two types, the one is from the jammed gas column flow to the inverse annular flow, the other one is directly from the bubble flow to the inverse annular flow. The type of flow pattern transition with jammed gas column flow is more likely to occur for lower inlet temperature, lower heating power and higher pressure. A new empirical correlation which considering the effect of pressure was proposed to predict OFI since the empirical correlations for upward or horizontal flow don't apply downward flow, and it shows very good peformance for the present experimental data. In addition, a criterion for classifying what type of the flow pattern transition was obtained.

关键词： flow instability flow pattern transition Narrow rectangular channel Downward flow Jammed gas column flow

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flow pattern transition in gas-liquid downflow through narrow vertical tubes

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AICHE JOURNAL 2017年第2期63卷 792-800页

作者： Kumar, Amit Bhowmik, Satyabrata Ray, Subhabrata Das, Gargi Indian Inst Technol Kharagpur Dept Chem Engn Kharagpur 721302 W Bengal India

The present report studies on the flow pattern transitions during vertical air water downflow through millichannels (0.83Eotvos no.20.63). Four basic flow patterns namely falling film flow, slug flow, bubbly flow, and annular flow are observed in the range of experimental conditions studied and their range of existence has been noted to vary with tube diameter and phase velocities. Based on experimental observations, phenomenological models are proposed to predict the transition boundaries between adjacent patterns. These have been validated with experimental flow pattern maps from the present experiments. Thus the study formalizes procedure for developing a generalized flow pattern map for gas-liquid downflow in narrow tubes. (c) 2016 American Institute of Chemical Engineers AIChE J, 63: 792-800, 2017

关键词： two-phase flow downflow flow pattern transition drift flux model millichannel

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An experimental study on effects of oily content on flow pattern transition over horizontal tubes in a sewage source heat pump system

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INTERNATIONAL JOURNAL OF THERMAL SCIENCES 2022年 181卷

作者： He, Zhihao Zeng, Lin Meng, Shuangshuang Hao, Jingyu He, Tianbiao Mao, Ning China Univ Petr East China Coll Pipeline & Civil Engn Dept Gas Engn Qingdao Shandong Peoples R China Univ Tokyo Inst Ind Sci Tokyo Japan

The spray sewage heat exchanger is better used for sewage source heat pump systems due to its simple structure and good anti-blocking characteristics. To maintain high heat transfer efficiency of using oilfield wastewater, an experimental sewage source heat pump system is built and experimental studies are carried out to investigate the falling film flow patterns of oily wastewater over the horizontal tubes of spray sewage heat exchanger and effects of oily content. The critical spray density for flow pattern transition is clarified based on visualization by highspeed camera, and the influence of spray temperature and oily content are further analyzed. It is found the flow pattern transition is delayed with the critical spray density increased by 3%-12% when the oily content is raised from 0% to 20%, due to the higher temperature reduces the viscosity of the fluid. The critical spray density of flow pattern transition is also influenced by the spray temperature, which reduce the critical spray density from column flow to column-sheet flow from 0.0828 kg m-1 s-1 at 46 degrees C to 0.0782 kg m-1 s-1 at 65 degrees C for wastewater of 15% oily content. The tube surface temperature is further analyzed, and different high heat transfer performance regions are specified with a higher range of spray density for oily wastewater.

关键词： flow pattern transition Oily water Falling film Heat transfer Horizontal tube

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Numerical simulation on shell-side flow pattern transition and heat transfer of non-azeotropic refrigerant mixture

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APPLIED THERMAL ENGINEERING 2022年 214卷

作者： He, Xuejing Wang, Ji Li, Zhenlin Wan, Ran Hu, Jie Yang, Zhaoming China Univ Petr Coll Mech & Transportat Engn Beijing 102249 Peoples R China Syst Engn Res Inst Beijing 100094 Peoples R China

The non-azeotropic hydrocarbon refrigerant mixture flowing across shell-side of spiral wound heat exchanger is widely used in liquefied natural gas production industry. However, the phase-change heat transfer mechanism is still lack of thorough understanding. A numerical model is presented for simulating evaporation heat transfer of non-azeotropic hydrocarbon refrigerant mixture, CH4/C2H6, across multiple spiral wound tubes. Volume of Fluid model (VOF) was used to obtain liquid-vapor interface. The heat and mass transfer rates for each component were given as source terms. Thermophysical properties of the mixture were given using mixing laws in the literature. A flow pattern map was developed based on simulation results. The flow pattern transition and heat transfer were analyzed for the mixture with several component mixing ratios. With increasing vapor quality, pure ethane and methane-ethane mixture appear different flow patterns. The pure ethane has smoother liquid film on the tube wall than the methane-ethane mixture. The increasing of methane promotes the flow pattern transition. With vapor quality of 0.2-0.3, falling film flow transfers to shear flow. Shear flow transfers to spray flow for vapor quality of 0.7-0.8, where the heat transfer coefficient starts to decrease for methane-ethane mixture. For falling film flow, the heat transfer coefficient of pure ethane is higher than the methane-ethane mixture. The outcomes may help spiral wound heat exchanger design and evaluation for liquefied natural gas production.

关键词： Non-azeotropic mixture flow pattern transition Heat transfer Two-phase flow Numerical simulation

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Effect of high pressure on severe slugging and multiphase flow pattern transition in a long pipeline-riser system

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 2023年 148卷

作者： Zhao, Xiangyuan Xu, Qiang Wu, Quanhong Chang, Yingjie Cao, Yeqi Zou, Suifeng Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Severe slugging poses an enormous threat to the safe operation of high-pressure long petroleum pipelines. However, most published studies are conducted in short pipelines under atmospheric pressure. In this work, the gas-liquid two-phase flow experiment is conducted in the pipeline-riser system of 380 m long and 75 mm inner diameter under the separator pressure from atmospheric pressure to high pressure (10 MPa), and flow pattern maps are established. Under high-pressure conditions, liquid fallback and second blowout of severe slugging disappear. In the flow pattern maps, flow pattern types reduce, and severe slugging region shrinks. The boundary between stable flow and severe slugging appears on the left side of the flow pattern map and moves in the direction of higher superficial gas velocity. Increasing separator pressure leads to the increase in the severe slugging period. A correlation equation applicable to predicting the severe slugging period for different pressures (0, 1 and 5 MPa) is proposed, and the average error is less than & PLUSMN;7.9%. Due to the inhibition of high pressure, the amplitude of the riser differential pressure decreases at most working points and increases only at a few working points where flow pattern transition occurs.

关键词： Severe slugging flow pattern map Pipeline-riser flow pattern transition High pressure

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