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

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 111620-111620页

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 111253-111253页

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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Modeling of transition boundary from stratified to non-stratified liquid-liquid flows in small diameter pipe

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INTERNATIONAL JOURNAL OF MULTIPHASE flow 2024年 171卷

作者： Zhai, Lusheng Meng, Xinyu Zhang, Hongxin Jin, Ningde Tianjin Univ Sch Elect & Informat Engn Tianjin 300072 Peoples R China Tianjin Univ Technol & Educ Sch Automat & Elect Engn Tianjin 300222 Peoples R China

Modeling the instability of the interfacial wave in stratified liquid-liquid flows is a popular topic and attracts the interest of scholars. In this study, an experimental study is implemented in horizontal and +5 degrees inclined pipes with an inner diameter of 20 mm. A planar laser-induced fluorescence-60 (PLIF-60) system is utilized to visualize the flow structures at the pipe radial section, such as the curved interface and the droplet entrainment. Image processing is used to correct the PLIF-60 flow images and reconstruct quasi-3D flow structures. flow pattern maps for horizontal and inclined flows are drawn to indicate the transition boundary between stratified and nonstratified flows. Young-Laplace equation with dynamic contact angle is developed to predict the interface configuration. The predicted interface configuration shows a good agreement with that detected by the PLIF-60 system. In view of the fact that the interface configuration is partly associated with the stratified/non-stratified flow transition, a modified model for the transition boundary is established based on Kelvin-Helmholtz (KH) stability. Comparisons of the proposed transitional criteria with experimental data and available data in liquidliquid systems show reasonable agreement in small diameter pipes. Additionally, the proposed model with the consideration of interface configuration is basically not dependent on the wave parameters, such as wave amplitude and wavelength, providing a new way for predicting the transition boundary from stratified to nonstratified liquid-liquid flows in small diameter pipe.

关键词： Liquid-liquid flow PLIF Interface configuration KH stability flow pattern transition Interfacial wave

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Airlift pumps characteristics for shear-thinning non-Newtonian fluids: An experimental investigation on liquid viscosity impact

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 2023年第1期149卷

作者： Fadlalla, Dana Rosettani, Joshua Holagh, Shahriyar Ghazanfari Ahmed, Wael H. Univ Guelph Sch Engn 50 Stone Rd East Guelph ON Canada FloNergia Inc 5500 N Serv Rd 101 Burlington ON Canada

Shear-thinning non-Newtonian fluids are applied in a variety of chemical processing, wastewater, and food industries. However, handling and pumping these fluids, often possessing high viscosities, present significant challenges in these industrial settings. One effective solution to alleviate difficulties of pumping such fluids is through utilizing airlift pump technology. However, the use of this technology for these applications has not been sufficiently evaluated in the literature. In the present study, the operational performance of airlift pumps handling non-Newtonian fluids is experimentally investigated. A series of experiments is conducted using an airlift pump with a size of 31.75 mm to pump Xanthan Gum-water solutions with different concentrations of XG between 0.05 and 0.60 wt% (corresponding to viscosities ranging between 10 and 1000 cP) at a wide range of inlet air flow rates (6-140 SLPM). The impact of viscosity changes on the delivered liquid flow rate and pump efficiency is analyzed. In this analysis, high-speed imaging and capacitance sensor are used to evaluate the flow patterns and the instantaneous void fraction data needed to characterize the two-phase flow hydrodynamics. The effect of liquid viscosity on the time-series and the time-averaged void fraction data, their PDF distributions, flow pattern transition, and bubbles dynamic behavior is discussed. The results show that, on average, as liquid viscosity increases from 10.0 to 1000.0 cP, both delivered liquid flow rate and pumping efficiency reduce by 64.60% and 64.79%, respectively. However, the optimum performance points (i.e., maximum delivered liquid flow rate and pump efficiency) were found to occur around the same inlet air flow rates (in churn and slug flow patterns, respectively) regardless of the increase in liquid viscosity. Moreover, increasing the viscosity is found to significantly affect the instantaneous void fraction distributions and accelerate the slug-to-churn transition. L

关键词： Airlift pump Non-Newtonian fluids Shear-thinning behavior flow pattern transition Viscosity effect Bubbles dynamic behavior

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Study on the characteristics of interfacial waves in annular flow by image analysis

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CHEMICAL ENGINEERING SCIENCE 2020年 212卷

作者： Lin, Ruinan Wang, Ke Liu, Li Zhang, Yongxue Dong, Shaohua China Univ Petr Beijing Key Lab Proc Fluid Filtrat & Separat Beijing Peoples R China Shanghai Jiao Tong Univ Sch Nucl Sci & Engn Shanghai Peoples R China China Univ Petr Pipeline Res Ctr Beijing Peoples R China

Various scales of interfacial waves in length and amplitude are usually present at the gas-liquid interface. Complete knowledge of the interfacial waves is of great importance for the characterization of mass, momentum and energy exchange in annular flow. In this paper, an image analysis approach for interfacial wave recognition by detecting the spatiotemporal evolution of liquid film is introduced. Based on the image analysis, the identification and the characteristics of the interfacial waves are carefully investigated. The results indicate that the flow patterns identification and the pressure gradient are related to the characteristics and behaviors of interfacial waves. Remarkably, the analysis reveals that the orientation of interfacial waves is the significant criteria in flow patterns identification, and disturbance waves play the dominant role in pressure gradient. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Interfacial wave Image analysis Annular flow flow pattern transition

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Measurement of thickness and analysis on flow characteristics of upper swirling liquid film in gas-liquid cylindrical cyclone

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 2021年 123卷 110331-110331页

作者： Wang, Ya-An Chen, Jian-Yi Yue, Ti Yang, Yang Han, Ming-Shan Yan, Chao-Yu China Univ Petr State Key Lab Heavy Oil Proc Beijing 102249 Peoples R China Beijing Key Lab Proc Fluid Filtrat & Separat Beijing 102249 Peoples R China

The gas-liquid cylindrical cyclone (GLCC) is a device used to separate gas from liquid in offshore or subsea oil and gas production systems. The liquid film swirling along the upper cylinder wall in the GLCC is referred to as "upper swirling liquid film" (USLF). The flow patterns of USLF have a great influence on GLCC's separation performance. However, the dynamics of the gas-liquid flow in a GLCC, especially the USLF characteristics, have not been well understood. In this study, experiments were conducted to investigate flow characteristics of USLF in a GLCC. The range of gas and liquid Reynolds numbers, Re-g and Re-l, was 27,869 <= Re-g <= 68,120 and 2,881 <= Re-l <= 14,335 respectively. The USLF's thickness was measured using button electrodes. The results showed that the liquid film became thinner after leaving the inlet and the circumferential fluctuation of the thickness was not significant. The gas-liquid velocities had significant influences on film thickness, which increased almost linearly as liquid velocity increased, while presented a roughly S-shaped distribution as gas velocity increased. The friction factors of GLCC were determined based on the measured liquid film thickness and pressure drop. Additionally, the USLF's flow patterns include swirling annular flow and swirling churn flow. Finally, a judgment criterion for flow pattern transition was established under the minimum gas-liquid interfacial stress theory. The model could accurately predict the transition condition. This work may provide a basis for comprehensive understanding of USLF characteristics.

关键词： Gas-liquid cylindrical cyclone (GLCC) Upper swirling liquid film (USLF) Liquid film thickness Swirling friction factors flow pattern transition

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Multiphase flow Production Enhancement Using Drag Reducing Polymers

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POLYMERS 2023年第5期15卷 1108-1108页

作者： Alsarkhi, Abdelsalam Salah, Mustafa King Fahd Univ Petr & Minerals Ctr Integrat Petr Res Dept Mech Engn Dhahran 31261 Saudi Arabia

This paper presents a comprehensive experimental investigation concerning the effect of drag reducing polymers (DRP) on enhancing the throughput and reducing the pressure drop for a horizontal pipe carrying two-phase flow of air and water mixture. Moreover, the ability of these polymer entanglements to damp turbulence waves and changing the flow regime has been tested at various conditions, and a clear observation showed that the maximum drag reduction always occurs when the highly fluctuated waves were reduced effectively by DRP (and that, accordingly, phase transition (flow regime changed) appeared. This may also help in improving the separation process and enhancing the separator performance. The present experimental set-up has been constructed using a test section of 1.016-cm ID;an acrylic tube section was used to enable visual observations of the flow patterns. A new injection technique has been utilized and, with the use of different injection rates of DRP, the results have shown that the reduction in pressure drop occurred in all flow configurations. Furthermore, different empirical correlations have been developed which improve the ability to predict the pressure drop after the addition of DRP. The correlations showed low discrepancy for a wide range of water and air flow rates.

关键词： drag reducing polymers multiphase flow production enhancement flow pattern transition disturbance waves

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Stratified-to-annular gas-liquid flow patterns transition in a horizontal pipe

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 2022年 132卷 1页

作者： Cherdantsev, Andrey, V Zdornikov, Semyon A. Cherdantsev, Mikhail, V Isaenkov, Sergey, V Markovich, Dmitry M. Kutateladze Inst Thermophys Novosibirsk Russia Novosibirsk State Univ Novosibirsk Russia

Air-water flow in a 20 mm horizontal pipe is studied using side-view visualization with a background image and Brightness-Based Laser-Induced Fluorescence technique. The investigation is focused on the transition from stratified to annular flow patterns. Stratified flow is organized at the pipe inlet, and the dynamics of liquid lifting up the pipe walls is investigated. During the transition to annular flow, the liquid film is spread over the pipe walls in a stable and gradual manner;the spreading begins before the disturbance waves are formed. Two transition regimes are identified. At large gas and low liquid flow rates, the film is spread up the pipe walls reaching a stable height unaffected by the passing waves. At low gas and large liquid flow rates, the liquid can be lifted by the large-scale waves, but it promptly drains downwards between the waves. Secondary flow in the gas phase is considered the main mechanism of liquid lifting and the only mechanism able to create a stable annular film. The processes of formation and development of disturbance waves are qualitatively the same as previously observed in vertical pipes. Namely, the disturbance waves are formed due to the coalescence of high-frequency initial waves appearing near the inlet;the disturbance waves undergo coalescence and grow in amplitude and speed. Quantitatively, the disturbance wave formation occurs at larger distances from the inlet compared to the vertical flow, and the acceleration rate is much lower. An estimation of circumferential shear stress due to secondary flow is made based on the roughness of the liquid film surface at the bottom of the pipe. An increase in this shear stress increases the height of the liquid film on the pipe walls.

关键词： Annular flow Stratified flow flow pattern transition flow development Disturbance waves Laser-induced fluorescence

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