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Effects of density, viscosity and surface tension on flow regimes and pressure drop of two-phase flow in horizontal pipes

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JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING 2021年 205卷

作者： AL-Dogail, Ala S. Gajbhiye, Rahul N. KFUPM Dhahran Saudi Arabia

Two-phase gas/liquid flow in pipes is a common occurrence in the petroleum, chemical, nuclear and geothermal industry. In the petroleum industry, it is encountered in the production, transportation, and processing of hydrocarbons from the oil and gas fields. In designing these systems, accurate prediction of pressure drop is imperative, which is determined from the flow pattern and flow regime map. Unfortunately, most of the flow regime maps were developed for the air-water system and widely used for the oil/gas system. Despite the practical importance, the general applicability of these maps is not addressed. In order to improve the generality of flow regime maps, it is necessary to evaluate the effect of density, viscosity, and surface tension, which differ by great magnitude on flow regime maps. Thus, this study evaluates the effect of density, viscosity, and surface tension on the flow regime map. To evaluate the effect of fluid properties, experiments were conducted using a horizontal flow loop of 9.15 m (30 ft) pipe length and 0.0254 m (1-inch) pipe diameter with a two-phase air/liquid system. The surface tension was varied using the surfactant solution, viscosity was varied with the aid of glycerin, and density was varied with the aid of calcium bromide. The superficial velocity of the liquid ranges from 0 to 3.048 m/s (0-10 ft/s) and superficial gas velocity ranges from 0 to 18.288 m/s (0-60 ft/s) respectively. The experimental data were used to generate a flow pattern map and to predict the effect of these properties on the variation in the boundaries of different flow patterns and pressure drop. The results show that the flow patterns and transition boundaries were affected by fluid properties. The boundary between the annular and slug-annular flow at high velocity, the slug flow and pseudo-slug flow at medium velocity, and inertial wave and ripple wave flow at low velocities are affected by the variation in surface tension, viscosity, and density. The dec

关键词： flow regime Viscosity Density Surface tension flow pattern transition Pressure drop

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Bubble coalescence, growth, breakup and distribution in boiling water-cooled packed bed reactor

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ANNALS OF NUCLEAR ENERGY 2021年 151卷

作者： Xu, Guangzhan Sun, Zhongning Zhang, Xiantao Wuhan Second Ship Design & Res Inst Wuhan 430064 Peoples R China Harbin Engn Univ Natl Key Discipline Lab Nucl Safety & Simulat Tec Harbin 150001 Peoples R China Wuhan Univ Sch Power & Mech Engn Wuhan 430072 Hubei Peoples R China

The flow patterns in the heated packed bed are different to those without the heated packed bed. To gain a deeper understanding of these phenomena, the bubble coalescence, breakup, and distribution in a volumetrically heated packed bed are determined through experiments, and are very important for recognizing the flow pattern transition mechanisms in boiling water-cooled packed bed reactors. A highspeed camera was used for capturing images of these bubbles to analyze their behavior. The results revealed five types of bubble coalescence are observed in our experimental study. Bubble growth plays an important role in the flow pattern transition because it enlarges the contact area between the bubbles and the particles in the heated packed bed. The portion of small bubbles significantly increased with the decrease of the inlet fluid temperature and the increase of mass flux. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： flow pattern transition Bubble coalescence Bubble breakup Packed bed

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Experimental study on air-water countercurrent flow limitation in horizontal pipes with different types of obstructions

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PROGRESS IN NUCLEAR ENERGY 2024年 169卷

作者： Zhu, Xixi Xu, Chende Gu, Mingzhou Tang, Shuai Wang, Naihua Shandong Univ Inst Thermal Sci & Technol Jinan 250061 Peoples R China China Nucl Power Engn Co Ltd State Key Lab Nucl Power Safety Monitoring Technol Shenzhen 518000 Peoples R China

In a nuclear power plant, gas-liquid countercurrent flow limitation (CCFL) may occur in the liquid level measurement system where an orifice obstruction is installed in the horizontal pipeline, which will introduce errors into the system and affect the reliable operation of the system. The investigations on the CCFL phenomenon in the flow channel with obstruction are important for nuclear reactor safety. In this work, we aim to experimentally investigate the air-water countercurrent flow behaviors and CCFL characteristics in horizontal pipes with different types of obstructions. Visualization experiments are carried out and three test sections with different types of obstructions are studied. An image-processing technique and statistical treatments are implemented to investigate the interfacial behavior of the two-phase flow. During the experiment, we observed two kinds of flow pattern transitions from stratified flow to slug flow. The flow pattern transition is due to the formation of the obstruction slug inside the orifice in the test pipe containing tapered structures on the two sides (Type-A). While in the test pipes containing a sudden contraction and a sudden expansion (Type-B), obstruction slug does not happen and the pipe slug leads to a flow pattern transition. As liquid velocity increases, the average of the liquid holdup increases while the standard deviation tends to decrease. The closer to the water inlet of the pipe, the higher the average of the liquid holdup. The dominant frequencies of the liquid holdup are below 1 Hz. The wavelet analysis reveals that the frequency band with the largest wavelet energy is the approximation (A5), which ranges from 0 to 0.78125 Hz.

关键词： Countercurrent flow limitation Orifice obstruction Image processing flow pattern transition Statistical treatments CCFL characteristics

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Numerical Simulation of Sub-cooled flow Boiling in a Vertical Annulus Channel Under Near Atmospheric Pressure Conditions

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NUCLEAR SCIENCE AND ENGINEERING 2023年第6期197卷 1038-1070页

作者： Tom, Sachin Mangarjuna Rao, P. Venkatraman, B. Raghupathy, S. Homi Bhabha Natl Inst Training Sch Complex Mumbai 400094 India Indira Gandhi Ctr Atom Res Reactor Design & Techno Kalpakkam Tamil Nadu India

In the present study, a Eulerian-Eulerian two-fluid model is developed to analyze the flow boiling phenomena under near-atmospheric pressure conditions. The required constitutive correlations for the two-fluid model are provided as flow regime dependent within the algebraic interfacial area density framework. The two-fluid model developed with Rensselaer Polytechnic Institute (RPI) wall heat flux partitioning is used to analyze the subcooled nucleate boiling of water at low pressure in three vertical annulus channels of different heated lengths over a wide range of inlet mass flux, wall heat flux, and inlet subcooling *** subcooled water enters the heated annulus channel from the bottom end and is heated to near-saturation temperature. Upon reaching the saturation temperature, the wall boiling generates dispersed vapor bubbles near the heated wall. Farther along the heated length, larger bubbles can be formed by coalescence and evaporation, and the bubbles move on to the channel core region with increased vapor fraction so the flow regime changes from bubbly to transition regime. Farther along, it may turn to an annular flow regime. The benchmark experimental cases chosen are used to validate the model capability in predicting the bubbly flow and transition flow regime (slug flow regime) characteristics with the proposed methodology. Further, the low-pressure boiling model developed is successfully extended to predict the liquid sodium boiling in flow channels similar to sodium-cooled fast reactor fuel subchannels using suitable interfacial correlations.

关键词： Low-pressure flow boiling subcooled boiling flow pattern transition sodium boiling reactor safety

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EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER IN TWO-PHASE flow BOILING

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EXPERIMENTAL HEAT TRANSFER 2015年第1期28卷 23-36页

作者： Lim, T-W You, S-S Choi, J-H Kim, H-S Korea Maritime Univ Div Marine Syst Engn Pusan 606791 South Korea Korea Maritime Univ Div Mech & Energy Syst Engn Pusan 606791 South Korea Korea Maritime Univ Div Logist Syst Engn Pusan 606791 South Korea

In this article, an experimental investigation is performed to measure the boiling heat transfer coefficient of water flow in a microchannel with a hydraulic diameter of 500 mu m. Experimental tests are conducted with heat fluxes ranging from 100 to 400 kW/m(2), vapor quality from 0 to 0.2, and mass fluxes of 200, 400, and 600 kg/m(2)s. Also, this study has modified the liquid Froude number to present a flow pattern transition toward an annular flow. Experimental results show that the flow boiling heat transfer coefficient is not dependent on mass flux and vapor quality but on heat flux to a certain degree. The measured heat transfer coefficient is compared with a few available correlations proposed for macroscales, and it is found that previous correlations have overestimated the flow boiling heat transfer coefficient for the test conditions considered in this work. This article proposes a new correlation model regarding the boiling heat transfer coefficient in mini-and microchannels using boiling number, Reynolds number, and modified Froude number.

关键词： boiling heat transfer flow pattern transition Froude number microchannel

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Gas-liquid downward flow through narrow vertical conduits: effect of angle of entry and tube-diameter on flow patterns

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INTERNATIONAL JOURNAL OF CHEMICAL REACTOR ENGINEERING 2021年第7期19卷 655-662页

作者： Kumar, Amit Das, Gargi Ray, Subhabrata Jha, Jay Mant Thakur, Amit K. Panda, Swapna Rekha Nirma Univ Ahmedabad Inst Technol Dept Chem Engn Ahmadabad Gujarat India Indian Inst Technol Kharagpur Dept Chem Engn Kharagpur W Bengal India MANIT Bhopal Dept Chem Engn Bhopal India Univ Petr & Energy Studies Dept Chem Engn Dehra Dun Uttarakhand India SRICT Dept Chem Engn Bharuch Gujarat India

The present study investigates the flow pattern characteristics of air-water co-current down-flow in millichannels. The experiments have been performed in glass tube of diameter 0.0042 and 0.008 m. The fluids are injected through Y entry the included angle between the Y arms being 45 degrees, 90 degrees, 135 degrees, and 180 degrees (T Entry). The investigation reveals that the flow patterns are function of tube-diameter, and angle of fluid entry. Interestingly, stratified flow has been observed for steeper Y entry section at low liquid flow rates.

关键词： downflow entry effect flow pattern transition millichannel stratified flow two-phase flow

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Study of oblique granular impingement flow through CFD-DEM simulations and energy consumption statistics

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POWDER TECHNOLOGY 2024年 446卷

作者： Bi, Lei Chen, Jianhua Liu, Chunjiang Ge, Wei Tianjin Univ Sch Chem Engn & Technol Tianjin 300072 Peoples R China Chinese Acad Sci Inst Proc Engn State Key Lab Mesosci & Engn POB 353 Beijing 100190 Peoples R China Univ Chinese Acad Sci Sch Chem Engn Beijing 100049 Peoples R China

This paper investigates an experimental granular impingement flow system through simulations and energy consumption statistics. With the increase of solid concentration, flow patterns undergo cross flow (dense edge and dilute center), dispersed flow, and mixed-jet flow (dilute edge and dense center) in turn. The influence of gas phase on the flow pattern was investigated. According to the analysis of force and time-averaged velocity, it is revealed that gas-solid interaction will cause energy dissipation of granular flow, which cannot be ignored in specific cases. Then, a flow map is proposed according to both the Archimedes number and solid concentration. In addition, the flow pattern transition and local structure variations can be reflected by energy consumption statistics. Based on the simulations and methods developed in this work, it is promising to deepen the understanding and study of granular impingement flow from the viewpoints of energy consumption and new-type flow map.

关键词： Granular impingement flow Energy consumption statistics flow pattern transition flow map CFD-DEM

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Experimental investigation on flow boiling heat transfer characteristics of water and circumferential wall temperature inhomogeneity in a helically coiled tube

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CHEMICAL ENGINEERING SCIENCE 2023年 272卷

作者： Chang, Fucheng Liu, Yeming Lou, Jiacheng Shang, Yuhao Hu, He Li, Huixiong Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Helically coiled tubes (HCTs) have been widely used in chemical industry and nuclear engineering because of its compact structure and excellent heat transfer performance. This paper designed and built an experimental platform to study the flow boiling heat transfer (FBHT) of subcritical water with high temperature and high pressure in an HCT. The results showed that the wall temperature on the inner side is higher and it gradually decreases when moving to the outer side along the circumferential direction. The variation law of circumferential wall temperature inhomogeneity (CWTI) under different pressures, mass velocities, heat fluxes and vapour qualities was obtained. The distribution of circumferential wall temperature varies greatly in the single-phase region while it varies slightly and is relatively uniform in the two-phase boiling region. As the vapour quality increases, the CWTI decreases first, and maintains at a low value when the vapour quality is about 0.0 ti 0.9. When the vapour quality reaches about 0.9, the CWTI increases rapidly. When the vapour quality is less than 0.5, the heat flux and mass velocity have little effect on the CWTI. When the vapour quality is larger than 0.5, reducing the heat flux or increasing the mass velocity can effectively reduce the CWTI. In addition, the flow pattern of two-phase boiling flow in the HCT is divided into four regions, namely bubble flow, slug flow, annular flow and mist flow, and the transition vapour quality xt1 = 0.2, xt2 = 0.5 and xt3 = 0.93 are respectively selected according to the sud-den abrupt change of the wall temperature or the differential pressure. Finally, the existing FBHT corre-lations are collected and evaluated and the calculation accuracy needs to be improved for more accurate calculation. Therefore, a new FBHT correlation with better accuracy is proposed for calculating the heat transfer coefficient of two-phase flow boiling in the HCT.(c) 2023 Elsevier Ltd. All rights reserved.

关键词： Helically coiled tube flow boiling heat transfer Circumferential wall temperature inhomogeneity flow pattern transition Heat transfer correlation

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Numerical analysis of the effects of different outlet sizes on pebble flows in HTR-10 pebble beds

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NUCLEAR ENGINEERING AND DESIGN 2022年 387卷

作者： Wu, Mengqi Gui, Nan Liu, Xu Yang, Xingtuan Tu, Jiyuan Jiang, Shengyao Tsinghua Univ Inst Nucl & New Energy Technol Collaborat Innovat Ctr Adv Nucl Energy Technol Minist EducKey Lab Adv Reactor Engn & Safety Beijing 100084 Peoples R China RMIT Univ Sch Engn Bundoora Vic 3083 Australia

The effects of outlet size on the flow characteristics in the pebble bed are studied by means of Discrete Element Method (DEM). Two ways of changing the outlet are considered: fixed hopper angle ('D' cases) and fixed hopper height ('d' cases). The pebble flow inside pebble beds shows the characteristics of mass flow in the upper part and funnel flow in the lower part, therefore, the changes in the flow pattern are studied first to find out the special transition region by critical time and critical height. Results show that the transition of flow pattern will occur earlier when the opening is smaller, and the critical height of transition increases with the decrease of outlet size for 'd' cases. By contrast, there is almost no difference in the critical time and height in 'D' cases, indicating that the hopper angle is an important factor affecting the overall flow pattern rather than the hopper height. In the second part, from the perspective of core safety, the influences of outlet size on the retention, flow uniformity and velocity characteristics inside the core are analyzed. The increase of outlet size can improve both the retention and flow uniformity. Changing the outlet by adjusting the hopper angle has a more significant influence on the flow performance. From the analysis of pebbles in different radial positions, it can be found that although pebbles in the middle region flow out slower when the opening is larger, it is opposite in terms of pebbles near the wall, where less retention is observed. Overall, a larger proportion of pebbles are in motion with relatively small but similar speed, showing a more uniform movement. Interestingly, simply changing the hopper height to adjust the opening has no effect on the flow of pebbles within 1d range from the wall.

关键词： Pebble flow flow pattern transition flow uniformity Retention Reactor design

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An investigation of transition processes from transient gas-liquid plug to slug flow in horizontal pipe: Experiment and Cost-based recurrence analysis

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NUCLEAR ENGINEERING AND DESIGN 2021年 379卷

作者： Zhai, Lusheng Yang, Jie Wang, Yuqing Tianjin Univ Sch Elect & Informat Engn Tianjin 300072 Peoples R China

Transient gas-liquid two-phase flows are often encountered in nuclear industries. Investigating the dynamics of the transient gas-liquid flows is of significance for optimizing the reaction processes and predicting the thermal-hydraulic phenomena relevant to the performance of nuclear reactors. In this study, a multi-nozzle gas inlet was designed to mimic the transient gas-liquid flows in a horizontal pipe. A conductance wire-mesh sensor (WMS) was used to visualize the phase distribution at the pipe cross-section. Based on the WMS data, a cost-based recurrence analysis (CBRP) was developed to reveal the dynamics of transient gas-liquid flows. Different transition processes from plug flow to slug flow were observed in the experiment and explored by the determinism (DET) of the CBRP. Note that special flow structures, i.e., wave bridge and pseudo slug, were encountered during the flow pattern transition, and their generation mechanisms were uncovered. The processes of the flow pattern transition were also characterized by the slug frequency and the probability density function of the water holdup, which presented a good agreement with the CBRP results.

关键词： Transient gas-liquid flows Wire-mesh sensor Cost-based recurrence analysis flow pattern transition flow dynamics

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