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Numerical study on flow pattern transition, liquid film and heat transfer for R1233zd/FC72 mixtures across tube bundles

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APPLIED THERMAL ENGINEERING 2025年 260卷

作者： Wang, Ji He, Xuejing Li, Zhenlin Anton, Javier Munoz China Univ Petr Coll Mech & Transportat Engn Beijing 102249 Peoples R China Univ Politecn Madrid Escuela Tecn Super Ingn Ind C Jose Gutierrez Abascal 2 Madrid 28006 Spain

The non-azeotropic mixtures phase-change flow across tube bundles is widely used in the refrigeration industry. A simulation model of R1233zd/FC72 mixtures is presented to study flow pattern transition and heat transfer across tube bundles. Volume of Fluid (VOF) model is used to determine the flow pattern. An experiment is conducted to validate the simulation model with average deviation of 8.97%. The results showed that the flow pattern transition appears for various conditions. In addition, the liquid film thickness and heat transfer are analyzed, focusing particularly on the impact of various mixture components. With increasing vapor quality, the flow pattern transfers from sheet flow to semi-annular flow and then to droplet flow. Sheet to semi-annular flow transition occurs for a vapor quality of 0.4-0.6, and semi-annular flow transfers to droplet flow for a vapor quality of 0.7-0.8. For sheet flow, the local heat transfer coefficient on the tube surface is the highest at 90 degrees (circumferential angle) from the summit point of the cross-sectional tube circle due to the thinnest liquid film. The liquid film turns thinner with increasing mass fraction of R1233zd and vapor quality. Increasing the mass fraction of R1233zd and vapor quality promotes heat transfer. However, the flow pattern transfers from sheet flow to the other ones, the heat transfer coefficient starts to decrease. The heat transfer coefficient is the highest for a vapor quality of around 0.4-0.5 and a mass fraction of R1233zd of around 0.7-0.9.

关键词： Non-azeotropic mixture flow pattern transition Heat transfer Film thickness

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Study on liquid film velocity and flow pattern transition in gas-liquid cylindrical cyclone (GLCC)

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CHEMICAL ENGINEERING RESEARCH & DESIGN 2025年 217卷 267-282页

作者： Zhou, Yuhang Chen, Jianyi Li, Ziqing Wang, Ruikang Li, Sen 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 CNOOC Res Inst Co Ltd Beijing 100028 Peoples R China

The gas-liquid cylindrical cyclone (GLCC) is a compact and efficient oil and gas separation device. The separation performance of GLCC is directly related to the flow pattern of its USLF, and the velocity distribution and determination of the flow pattern transition of USLF depends on the accurate calculation of the wall-friction and gas-liquid interfacial factors. Air and water were used as the media and the tangential velocity and axial velocity distribution of the USLF measured using an image velocimetry system. The liquid film swirl angle was obtained and the liquid-film velocity distribution correlation established. A semi-empirical formula for wall friction and gas-liquid interfacial factors, represented by the liquid film swirl angle, were obtained. The criterion for flow-pattern transition was established and a generalized correlation formula for flow-pattern transition between annular and churn flows was proposed. The results provided new insights for further understanding of USLF and flow-pattern transition.

关键词： Gas-liquid cylindrical cyclone (GLCC) Separation performance Liquid film velocity flow pattern transition Swirl number PIV

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

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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

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

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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)

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flow pattern transition instability during flow boiling in a single microchannel

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2007年第5-6期50卷 1049-1060页

作者： Huh, Cheol Kim, Jeongbae Kim, Moo Hwan Pohang Univ Sci & Technol Dept Mech Engn Pohang 790784 Koungbuk South Korea KIER New & Renewable Energy Res Dept Taejon 305343 South Korea

We studied the unique characteristics of flow boiling in a single microchannel, including the periodic pressure drop, mass flow rate, and temperature fluctuations, in terms of a long time period. Experiments were conducted using a single horizontal microchannel and deionized water to study boiling instabilities at very small mass and heat flow rate conditions. A Polydimethylsiloxane (PDMS) rectangular single microchannel had a hydraulic diameter of 103.5 mu m and a length of 40 mm. A series of piecewise serpentine platinum micro-heaters were fabricated on the inner bottom wall of the rectangular microchannel to supply thermal energy to the test fluid. Real-time flow visualizations of the flow pattern inside the microchannel were performed simultaneously with measurements of the experimental parameters. Tests were performed for mass fluxes of 170 and 360 kg/m(2) s and heat fluxes of 200-530 kW/m(2). The test results showed that the heated wall temperature, pressure drop, and mass flux all fluctuated with a long period and large amplitude. These periodic fluctuations exactly matched the transition of two alternating flow patterns inside the microchannel: a bubbly/slug flow and an elongated slug/semi-annular flow. Therefore, the flow pattern transition instability in the single microchannel caused a cyclic behavior of the wall temperature, pressure drop, and mass flux, and this behavior had a very long period (100-200 s) and large amplitude. (c) 2006 Elsevier Ltd. All rights reserved.

关键词： two-phase instability microchannel two-phase flow flow pattern transition flow boiling

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

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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

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Numerical analysis of flow pattern transition in a conical silo with ellipsoid particles

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ADVANCED POWDER TECHNOLOGY 2019年第9期30卷 1870-1881页

作者： Han, Yanlong Jia, Fuguo Li, Gengrun Liu, Hanru Li, Jiming Chen, Peiyu Northeast Agr Univ Coll Engn Harbin 150030 Heilongjiang Peoples R China

Gravity-driven discharge flow in conical silos is ubiquitous in manufacturing processes for numerous industries such as food, pharmaceutical and chemical industries, wherein flow pattern is the key topic to be studied. In this work, discrete element method was used to study discharge flow behaviors in a special conical silo. This work aims to understand the dynamic evolution of discharge flow pattern and establish methods for regional determination of flow pattern transition. The results indicated that both mass flow and funnel flow patterns coexist in the silo at the initial stage of discharge, and there is a definite transition process from mass flow to funnel flow. Furthermore, the flow pattern transition is revealed by the change in discharge flow characteristics. Specifically, the change in force acting on particles leads to the change of particle orientation and particle velocity field, macroscopically resulting in the flow pattern transition. Finally, based on the kinetic stress field and shear rate, the height and radial region of flow pattern transition were determined, respectively. Understanding of the flow pattern transition is useful to the design, scale-up and optimization of silos and similar structural devices. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

关键词： Discrete element method Ellipsoid particles Conical silo flow pattern transition

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A mechanistic model for the prediction of swirling annular flow pattern transition

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CHEMICAL ENGINEERING SCIENCE 2019年 199卷 405-416页

作者： Liu, Li Bai, Bofeng Shanghai Jiao Tong Univ Sch Nucl Sci & Engn Shanghai 200240 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The accurate prediction of flow patterns and their transition is extremely important for proper design, operation and optimization of two-phase flow systems, since the parameters such as pressure loss and heat and mass transfer are strongly dependent on the flow pattern. So far, the non-swirling gas-liquid flow in straight pipes have been widely studied and various mechanisms that lead to flow pattern transition have been clarified and modeled. However, the dynamics of gas-liquid flow under swirling condition are not well understood, and no detailed models are available for the prediction of swirling flow pattern transition. To address this, in our previous work (Liu and Bai, 2018), a visualization experiment aimed at classifying flow regimes in swirling gas-liquid flow was presented and three typical swirling flow regimes, i.e., swirling gas column flow, swirling intermittent flow and swirling annular flow were classified and defined, respectively. As the swirling annular flow can be regarded as a special case of conventional annular flow (i.e., when tangential velocity does not equal zero), in present paper, a mechanistic model for the prediction of the swirling annular flow pattern transition was developed considering its physical interest and great practical significance. Two physical mechanisms that lead to the transition from swirling annular flow to other flow patterns were revealed and modeled, respectively. The model was evaluated against a wide range of swirling and non-swirling experimental data and based on this model, the effects of different parameters (e.g., hydraulic diameter, working pressure and swirl angle) on the boundary of flow pattern transition were presented. Results revealed that the range of swirling annular flow enlarges with the increase of the working pressure and swirl angle but narrows with the hydraulic diameter. Taking these influencing factors into account, a generalized formula for the prediction of the swirling annular flow patte

关键词： Gas-liquid flow Swirling annular flow flow pattern transition Mechanistic model

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Application of orthogonal design to optimize flow pattern transition conditions

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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

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