检索结果-内蒙古大学图书馆

flow pattern transition and destabilization mechanism of thermocapillary convection for low Prandtl number fluid in a deep annular pool with surface heat dissipation

引用

INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2018年第PartB期126卷 118-127页

作者： Zhang, Li Li, You-Rong Wu, Chun-Mei Liu, Qiu-Sheng Chongqing Univ Coll Power Engn Key Lab Low Grade Energy Utilizat Technol & Syst Minist Educ Chongqing 400044 Peoples R China Sichuan Int Studies Univ Chongqing Nanfang Translators Coll Chongqing 401120 Peoples R China Chinese Acad Sci Inst Mech Key Lab Micrograv Natl Micrograv Lab Beijing 100190 Peoples R China

In order to understand clearly the flow pattern transition and the destabilization mechanism of thermocapillary convection for low Prandtl number fluids in a deep annular pool with surface heat dissipation, we carried out a series of three-dimensional numerical simulations by using the finite volume method. The radius ratio and the aspect ratio of an annular pool are respectively fixed at 0.5 and 1.0. Prandtl number of the working fluid is 0.011. Because the total heat dissipation coefficient on the free surface for low Prandtl fluids is small, Biot number is varied from 0 to 1.0. Results indicate that thermocapillary convection experiences the transitions from axisymmetric steady state flow into three dimensional steady flow and then into three-dimensional oscillation flow with the increase of Marangoni number. The critical Marangoni number of flow pattern transition decreases slightly with the increase of Biot number, and the maximum temperature and velocity fluctuations appear near the lower part of outer wall. The azimuthal temperature fluctuation on the free surface gradually shrinks to the inner wall, and the temperature fluctuation region decreases. However, it remains almost unchanged near the bottom of the annular pool, but the fluctuation amplitude increases. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： Thermocapillary convection Low Prandtl number fluid Surface heat dissipation flow pattern transition Annular pool

来源：评论

学校读者我要写书评

暂无评论

flow pattern transition and coal beneficiation in gas solid fluidized bed with novel secondary distributor

引用

ADVANCED POWDER TECHNOLOGY 2018年第5期29卷 1255-1264页

作者： Fan, Xuchen Zhou, Chenyang Zhao, Yuemin Duan, Chenlong Liu, Qingxia China Univ Min & Technol Minist Educ Key Lab Coal Proc & Efficient Utilizat Xuzhou 221116 Peoples R China China Univ Min & Technol Sch Chem Engn & Technol Xuzhou 221116 Peoples R China Univ Alberta Canadian Ctr Clean Coal Carbon & Mineral Proc Tec Edmonton AB T6G 2R3 Canada

Gas solid fluidized bed (GSFB) is an effective method of dry coal separation. In this study, porous sponge was introduced into a typical gas solid fluidized bed as secondary air distribution layer (PSFB) to stabilize the fluidized bed layer. The difference between PSFB and GSFB in flow pattern transition process was studied. Compared with GSFB, the minimum gas velocity and bed density fluctuation decreased while bed expansion ratio increased in PSFB. Furthermore, the distribution of bubble phase and emulsion phase were more homogeneous in PSFB. Under the operational conditions, the results of coal preparation in a PSFB showed that the ash content of clean coal was 10.25%. The probable error (E) was 0.095 g/cm(3), indicating that PSFB could provide a novel way for a good performance of dry coking coal beneficiation. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

关键词： flow pattern transition Fluidized bed Coal beneficiation Secondary distributor

来源：评论

学校读者我要写书评

暂无评论

CFD research on the influence of geometry characteristic on flow pattern and the transition mechanism in Rushton turbine stirred vessels

引用

INTERNATIONAL JOURNAL OF CHEMICAL REACTOR ENGINEERING 2022年第2期20卷 141-152页

作者： Wang, Yinghui Hao, Lin Zhu, Zhenxing Xu, Jinjie Wei, Hongyuan Tianjin Univ Sch Chem Engn & Technol Tianjin 300350 Peoples R China Sinopec Res Inst Petr Proc Dept Proc Engn Beijing 100083 Peoples R China

In this paper, the transient MRF approach coupled with the standard k-epsilon and SST k-omega turbulence models was employed to study the effect of bottom shape, impeller diameter (D-J) and bottom height (H-2) on critical impeller off-bottom clearance (C). It was found the bottom shape and bottom height (H-2) have obvious influence on the flow pattern transition from double-loop to single-loop of RT impeller. The flow pattern transition mechanism was inferred to relate to the relationship between the space required by the lower circulation zone and the actual space. The boundary conditions of critical C were further concluded to help distinguish the flow pattern and receive the expected one in the stirred vessel design.

关键词： computational fluid dynamics (CFD) flow pattern transition geometry structure impeller clearance Rushton turbine

来源：评论

学校读者我要写书评

暂无评论

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

引用

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

来源：评论

学校读者我要写书评

暂无评论

flow pattern transition during condensation of R134a and R1234ze(E) in microchannel arrays

引用

APPLIED THERMAL ENGINEERING 2017年 115卷 244-255页

作者： Wang, Ji Li, Jun Ming Hwang, Yunho Tsinghua Univ Minist Educ Dept Thermal Engn Key Lab Thermal Sci & Power Engn Beijing 100084 Peoples R China Univ Maryland Dept Mech Engn Ctr Energy Environm Engn College Pk MD 20740 USA

Two-phase flow pattern transition during the condensation of R134a and R1234ze(E) was experimentally investigated in a microchannel array made of borosilicate glass cooled symmetrically on the top and bottom by forced convection of water. The microchannel array consisted of 50 channels with the aspect ratio of 2.46, the hydraulic diameter of 301.6 mu M and the length of 50 mm. Saturation temperatures are 20-25 degrees C with mass fluxes varying from 6 to 50 kg/m(2)/s. Observed patterns are annular flow, steady injection flow, quasi-symmetric wave flow and slug/bubbly flow. In addition, three flow pattern transition modes including steady injection, wave-coalescence injection, and liquid bridging were observed and mapped in terms of liquid Webb number versus condensation number. The steady injection transition was more studied in detail by measuring the bubble length variation and the moving velocity of bubbles and slugs with different mass fluxes of R134a and R1234ze(E). The transition mechanism of injection flow was identified by analyzing the force balance based on the experimental results. The flow pattern transition locations and frequencies were measured and compared with the prediction correlations in the previous investigations. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Two-phase flow Condensation flow pattern transition Microchannel arrays R134a R1234ze(E)

来源：评论

学校读者我要写书评

暂无评论

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

引用

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

来源：评论

学校读者我要写书评

暂无评论

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

引用

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

来源：评论

学校读者我要写书评

暂无评论

Application of orthogonal design to optimize flow pattern transition conditions

引用

SENSOR REVIEW 2015年第4期35卷 425-431页

作者： Hou, Hailing Yue, Shihong Huang, Xiaoguang Wang, Huaxiang Tianjin Univ Sch Elect Engn & Automat Tianjin 300072 Peoples R China Tianjin Univ Sci & Techonol Coll Elect Informat & Automat Tianjin Peoples R China

Purpose - This paper aims to discuss flow pattern transition (FPT) as an important factor in multiple-phase flow measurements. Several methods have been proposed to control FPT, but those methods fail to address the many issues in complex flow conditions that can affect flow patterns. Design/methodology/approach - In this paper, a non-intrusive sensor instrumentation is applied to extract measurable data under different flow conditions. Using these data, a simple theoretical-mathematical method along with an orthogonal design is applied to FPT optimization. Orthogonal experiments are designed and carried out according to theoretical guidelines. Three selected process parameters - phase fraction, gas pressure in the initial independent process and liquid speed - are optimized for FPT results to produce a minimum FPT time. Findings - The following results are obtained: the phase fraction in the initial independent process can lead to significant reductions in FPT time, gas pressure plays an important role and liquid speed has no apparent effect on FPT results. Under optimized conditions, FPT time can be shortened to 0.3-0.6 times by controlling the above three parameters compared with normal conditions. Originality/value - The proposed method is simple, rapid and efficient for evaluating an FPT process and lays the foundation for further FPT applications.

关键词： Two-phase flow flow pattern flow pattern transition Orthogonal design

来源：评论

学校读者我要写书评

暂无评论

flow pattern transitions and liquid mass transfer resistance of binary zeotropic mixtures during flow boiling

引用

INTERNATIONAL JOURNAL OF THERMAL SCIENCES 2023年第1期194卷

作者： Qi, Zhuoling Jia, Li Dang, Chao Yin, Liaofei Beijing Jiaotong Univ Beijing Key Lab Flow & Heat Transfer Phase Changin Beijing 100044 Peoples R China

flow boiling visualization experiments were performed on the binary zeotropic mixtures in a rectangular channel with a cross-sectional area of 8 mm x 8 mm. R134a/R245fa binary mixtures with three mass ratios (20/80, 37/ 63, and 52/48 wt %) were selected for this study. Encapsulation probe sampling and gas chromatography (GC) techniques were used to measure the liquid mass fraction. The flow patterns, heat transfer, and liquid mass transfer resistances of the zeotropic binary mixtures were studied, with emphasis on the variation of liquid mass transfer resistance during the transition process of the flow patterns. The heat and mass flux were set in the range of 4-21 kW/m2 and 15-150 kg/m2 s, respectively. A wave-stratified to stratified bubble flow pattern transition criterion was proposed based on the experimental conditions, temperature glide and thermophysical properties. The liquid mass transfer resistances were related to the mass fraction of the higher volatile component, temperature glide, and vapor quality. The liquid mass transfer resistance increased during the transition process of the flow patterns dominated by the convective evaporation. The liquid mass transfer resistance decreased at firstly and then increased during the flow pattern dominated by the convective evaporation transitioned to the flow pattern dominated by the nucleate boiling. The stratified bubble flow exhibited better heat transfer performance, while the liquid mass transfer resistance remained unchanged with vapor quality.

关键词： flow boiling Liquid mass transfer resistance flow pattern transition Mass fraction Zeotropic mixtures

来源：评论

学校读者我要写书评

暂无评论

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

引用

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

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：