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Computational study of bubble Coalescence/break-up behaviors and bubble size distribution in a 3-D pressurized bubbling gas-solid fluidized bed of Geldart A particles

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Chinese Journal of Chemical Engineering 2022年第4期35卷 485-496页

作者： Teng Wang Zihong Xia Caixia Chen Department of Energy and Chemical Engineering East China University of Science and TechnologyShanghai 200237China

A computational study was carried out on bubble dynamic behaviors and bubble size distributions in a pressurized lab-scale gas-solid fluidized bed of Geldart A particles.High-resolution 3-D numerical simulations were performed using the two-fluid model based on the kinetic theory of granular flow.A finegrid,which is in the range of 3–4 particle diameters,was utilized in order to capture bubble structures explicitly without breaking down the continuum assumption for the solid phase.A novel bubble tracking scheme was developed in combination with a 3-D detection and tracking algorithm(MS3 DATA)and applied to detect the bubble statistics,such as bubble size,location in each time frame and relative position between two adjacent time frames,from numerical simulations.The spatial coordinates and corresponding void fraction data were sampled at 100 Hz for data analyzing.The bubble Coalescence/break-up frequencies and the daughter bubble size distribution were evaluated by using the new bubble tracking algorithm.The results showed that the bubble size distributed non-uniformly over cross-sections in the bed.The equilibrium bubble diameter due to bubble break-up and Coalescence dynamics can be obtained,and the bubble rise velocity follows Davidson’s correlation closely.Good agreements were obtained between the computed results and that predicted by using the bubble break-up model proposed in our previous work.The computational bubble tracking method showed the potential of analyzing bubble motions and the Coalescence and break-up characteristics based on time series data sets of void fraction maps obtained numerically and experimentally.

关键词： Pressurized gas-solid bubbling fluidized bed Geldart A particles Bubble size distribution Coalescence Break-up Bubble tracking algorithm

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Coalescence dynamics of two droplets of different viscosities in T-junction microchannel with a funnel-typed expansion chamber

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Chinese Journal of Chemical Engineering 2021年第10期34卷 43-52页

作者： Weixi Guo Chunying Zhu Taotao Fu Youguang Ma State Key Laboratory of Chemical Engineering School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300072China

The Coalescence behavior of two droplets with different viscosities in the funnel-typed expansion chamber in T-junction microchannel was investigated experimentally and compared with droplet Coalescence of the same viscosity.Four types of Coalescence regimes were observed:contact non-Coalescence,squeeze non-Coalescence,two-droplet Coalescence and pinch-off Coalescence.For droplet Coalescence of different viscosities,the operating range of non-Coalescence becomes narrowed compared to the droplet Coalescence of same viscosity,and it shrinks with increasing viscosity ratioηof two droplets,indicating that the difference in the viscosity of two droplets is conducive to Coalescence,especially when1Coalescence of same viscosity,the relation of critical capillary number with two-phase viscosity ratio and dimensionless droplet size is Cac=0.48λ^(0.26)l^(﹣2.64),while for droplet Coalescence of different viscosities,the scaling of critical capillary number with dimensionless average droplet size,dimensionless droplet size difference and viscosity ratio of two droplets is Cac=0.11η^(﹣0.07)ls^(﹣2.23)l^(0.16)_(d).

关键词： Microchannel Droplet Coalescence Viscosity ratio Critical capillary number

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Coalescence separation of oil water emulsion on amphiphobic fluorocarbon polymer and silica nanoparticles coated fiber-bed coalescer

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Chinese Journal of Chemical Engineering 2021年第8期34卷 29-37页

作者： Qian Zhang Lei Li Lixia Cao Yanxiang Li Wangliang Li CAS Key Laboratory of Green Process and Engineering Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Innovation Academy for Green Manufacture Chinese Academy of SciencesBeijing 100190China

Discharging untreated oily wastewater into the environment disrupts the ecological balance,which is a global problem that requires urgent solutions.Superhydrophilic and superoleophilic fibrous medium(FM)effectively separated oil–water emulsion as it was hydrophobic underwater.But its separation efficiencies(SEs)first increased to 98.9%,then dropped to 97.6%in 10 min because of oil-fouling.To tackle this problem,FM deposited with 0%–10%silica nanoparticle(NPsFMs),then coated by fluorocarbon polymer(X-[CH_(2)CH_(2)O]nCH_(2)CH_(2)O-Y-NH-COOCH_(2)C4F9)(FCNPs FMs),was used to enhance its roughness and regulate its initial wettability to improve the anti-fouling property.FCFM and FCNPs FMs were hydrophobic and oleophobic in air and oleophobic underwater.Their water contact angles,oil contact angles and oil contact angles were 115.3°–121.1°,128.8°–136.5°,and 131.6°–136.7°,respectively,meeting the requirement of 90°–140°for Coalescence separation.FCNPs FM-5 had the best separation performance with a constant value of 99.8%in 10 min,while that of FCNPs FM-10 slightly decreased to 99.5%.Theoretical released droplet(TRD)diameter,calculated by the square root of the product of pore radius and fiber diameter,was used for the evaluation of Coalescence performance.Analyzed by two ideal models,TRD diameter and fiber diameter showed a parabola type relationship,proving that the separation efficiency was a collaborative work of wettability,pore size and fiber diameter.Also,it explained the SEs reduction from FCNPs FM-5 to FCNPs FM-10 was revelent to the three parameters.Moreover,FCNPsFMs effectively separated emulsions stabilized by cationic surfactant CTAB(SEs:97.3%–98.4%)and anionic surfactant SDBS(SEs:91.3%–93.4%).But they had an adverse effect on nonionic surfactant Tween-80 emulsion separation(SEs:94.0%–71.76%).Emulsions made by diverse oils can be effectively separated:octane(SEs:99.4%–100%),rapeseed oil(SEs:97.3%–98.8%),and diesel(SEs:95.2%–97.0%).These findings provide new insights for designing novel materials for oil–wat

关键词： Oil–water separation Fluorocarbon polymer Amphiphobic Coalescence

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Enhanced Coalescence separation of oil-in-water emulsions using electrospun PVDF nanofibers

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Chinese Journal of Chemical Engineering 2021年第10期34卷 76-83页

作者： Yujie Yang Lei Li Qian Zhang Wenwen Chen Song Lin Zaiqian Wang Wangliang Li CAS Key Laboratory of Green Process and Engineering Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China Key Laboratory of Magnetic Molecules&Magnetic Information Materials Ministry of Education The School of Chemical and Material ScienceShanxi Normal UniversityLinfen 041004China Innovation Academy for Green Manufacture Chinese Academy of SciencesBeijing 100190China Guizhou Water Fuquan Co. LtdGuiyang 550081China

A novel and high-efficiency Coalescence membrane enhanced by nano-sized polyvinylidene fluoride(PVDF)nanofibers based on polyester(PET)substrate was fabricated using electrospinning method.The properties of the electrospun nanofibers such as roughness and surface morphology greatly affected the oil droplet interception efficiency and surface wettability of the membrane.A series of Coalescence units were prepared with different layers of nanofibrous membrane and the separation efficiencies at different initial concentrations,flow rates,and oil types were tested.It is very interesting that the obtained nanofibrous membrane exhibited superoleophilicity in air but poor oleophilicity under water,which was beneficial to the Coalescence process.The Coalescence unit with four membrane layers had excellent performances under different initial concentrations and flow rates.The separation efficiency of the 4-layers unit remained above 98.2%when the initial concentration reached up to 2000 mg·L-1.Furthermore,the unit also exhibited good performance with the increasing oil density and viscosity,which is promising for large-scale oil wastewater treatment.

关键词： Coalescence Electrospinning Nanofibrous membrane Oil-in-water emulsions

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Coalescence-dominated microstructure evolution during solidification of 20SiMn steel

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Journal of Iron and Steel Research(International) 2020年第5期27卷 506-516页

作者： Xiao-ping Ma Dian-zhong Li Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016LiaoningChina

The evolution of microstructures during the solidification of 20SiMn steel was investigated.The dominant role of Coalescence was revealed by analyzing the quenched microstructures and the solute distribution.In the parameter range investigated,including the slow solidification,the fast solidification and the directional solidification,the Coalescence can happen at multiple solidification stages and on multi-scales.During the directional solidification,the ternary and fourth dendritic arms coalesce into the secondary dendritic arms,and the secondary dendritic arms further coalesce to produce the cellular crystals.The cellular crystals become coarse through further Coalescence.During the non-directional solidification,the initial microstructures are discrete crystals without the dendritic pattern.Both the dendritic arms and dendritic stems appearing in the later solidification stage are produced by the Coalescence on multi-scales.The Coalescence is more significant in the later solidification stage.The mechanism of Coalescence is attributed to different melt compositions in different local domains and the reduction of the interface energy.

关键词： Solidification Microstructure Coalescence Steel Microsegregation

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Bubble Coalescence efficiency near multi-orifice plate

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Chinese Journal of Chemical Engineering 2019年第8期27卷 1765-1776页

作者： Jiming Wen Qiunan Sun Zhongning Sun Haifeng Gu Fundamental Science on Nuclear Safety and Simulation Technology Laboratory Harbin Engineering University

Bubble Coalescence reduces specific area and weakens the work performance of bubble column. The bubble Coalescence near gas sparger which is caused mainly by bubble growing is different from the ones occurring in major liquid. Bubble Coalescence efficiency near gas sparger is influenced by many factors including sparger configuration, gas flow rate, bubble deformation, solution composition, etc. This work has conducted a set of visual experiments to study the Coalescence characteristics near multi-orifice plate. The experiment parameters cover a wide range of conditions including large scope of gas flow rate,different kinds of solution and orifice configurations. The experimental results suggest that Coalescence time is applicable to reflect the influence of the pitch of orifices and gas flow rate on bubble Coalescence efficiency. As the number of orifices increases, bubble Coalescence efficiency is reduced by the disturbance from the bubbles at adjacent orifices. A hindering coefficient is used to consider the hindering effect of additives on bubble Coalescence efficiency. Finally a new calculation expression is established to predict bubble Coalescence efficiency near multi-orifice plate whose fundamental form is based on the logistic curve of binary response. The calculated values that refer to this calculation expression are well consistent with the experimental results.

关键词： Bubble column Bubble Coalescence efficiency Multi-orifice plate Coalescence time

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Complete Coalescence, Partial Bounce and Rebound: Different Regimes Resulting from the Interaction of a Free Falling Drop with a Target Fluid

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Fluid Dynamics & Materials Processing 2020年第4期16卷 801-811页

作者： Yuli D.Chashechkin Andrey Y.Ilinykh Ishlinsky Institute for Problems in Mechanics of the Russian Academy of Sciences Moscow119526Russia

The interaction of a falling drop(diluted aqueous solution of ink in various concentrations)with a target fluid(partially degassed tap water)has been tracked by means of high-resolution video recording and photography.The experimental setup has carefully been prepared in order to preserve the axial symmetry of initial conditions.Three regimes of interaction have been identified accordingly(depending on the drop velocity as controlled by the distance of fall):rapid droplet Coalescence,rebound with the conservation of the drop volume and shape,and partial Coalescence.Previous findings are recovered and confirmed,and enriched with heretofore unseen observations of complex partial Coalescence.An extensive set of data is reported to support understanding of the observed dynamics and their repeatability and reproducibility.The overall study has been carried out with the express intent to spur the future development of detailed mathematical models and numerical methods suited for this kind of problems.

关键词： Drop Coalescence bounce spray transport of matter miscible fluids

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Wetting and Coalescence of the liquid metal on the metal substrate

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Chinese Physics B 2017年第8期26卷 140-146页

作者：赵珍阳李涛段云瑞王志超李辉 Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials Ministry of EducationShandong UniversityJinan 250061China

Molecular dynamics （MD） simulations are performed to investigate the wettability of liquid metal on the metal sub- strate. Results show that there exists different wettability on the different metal substrates, which is mainly determined by the interaction between the liquid and the substrate. The liquid metal is more likely to wet the same kind of metal substrate, which attracts the liquid metal to one side on the hybrid substrate. Exchanging the liquid metal and substrate metal has no effect on the wettability between these two metals. Moreover, the study of metal drop coalescing indicates that the metal substrate can significantly affect the Coalescence behavior, in which the changeable wettability of liquid metal plays a predominant role. These studies demonstrate that the wetting behavior of liquid metal can be controlled by choosing the suitable metal substrate.

关键词： molecular dynamics （MD） simulations liquid metal wettability Coalescence

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On cubic Hermite Coalescence hidden variable fractal interpolation functions

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Applied Mathematics(A Journal of Chinese Universities) 2015年第1期30卷 55-76页

作者： Puthan Veedu Viswanathan Arya Kumar Bedabrata Chand Department of Mathematics Indian Institute of Technology Madras

Hermite interpolation is a very important tool in approximation theory and nu- merical analysis, and provides a popular method for modeling in the area of computer aided geometric design. However, the classical Hermite interpolant is unique for a prescribed data set, and hence lacks freedom for the choice of an interpolating curve, which is a crucial requirement in design environment. Even though there is a rather well developed fractal theory for Hermite interpolation that offers a large flexibility in the choice of interpolants, it also has the short- coming that the functions that can be well approximated are highly restricted to the class of self-affine functions. The primary objective of this paper is to suggest a gl-cubic Hermite in- terpolation scheme using a fractal methodology, namely, the Coalescence hidden variable fractal interpolation, which works equally well for the approximation of a self-affine and non-self-affine data generating functions. The uniform error bound for the proposed fractal interpolant is established to demonstrate that the convergence properties are similar to that of the classical Hermite interpolant. For the Hermite interpolation problem, if the derivative values are not actually prescribed at the knots, then we assign these values so that the interpolant gains global G2-continuity. Consequently, the procedure culminates with the construction of cubic spline Coalescence hidden variable fractal interpolants. Thus, the present article also provides an al- ternative to the construction of cubic spline Coalescence hidden variable fractal interpolation functions through moments proposed by Chand and Kapoor [Fractals, 15（1）（2007）, pp. 41-53].

关键词： cubic Hermite interpolant cubic spline fractal interpolation function Coalescence hidden vari-able convergence.

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Studies on Droplet Size Distributions during Coalescence in Immiscible Polymer Blends Filled with Silica Nanoparticles

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Chinese Journal of Polymer Science 2014年第3期32卷 255-255,256-267页

作者： Zhi-ming Zou 孙昭艳 Li-jia AnState Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of Sciences

The effect of silica nanoparticles on the morphology of （10/90 wt%） PDMS/PBD blends during the shear induced Coalescence of droplets of the minor phase at low shear rate was investigated systematically in situ by using an optical shear technique. Two blending procedures were used： silica nanoparticles were introduced to the blends by pre-blending silica particles first in PDMS dispersed phase （procedure 1） or in PBD matrix phase （procedure 2）. Bimodal or unimodal droplet size distributions were observed for the filled blends during Coalescence, which depend not so much on the surface characteristics of silica but mainly on blending procedure. For pure （10/90 wt%） PDMS/PBD blend, the droplet size distribution exhibits bimodality during the early Coalescence. When silica nanoparticles （hydrophobic and hydrophilic） were added to the blends with procedure l, bimodal droplet size distributions disappear and unimodal droplet size distributions can be maintained during Coalescence; the shape of the different peaks is invariably Gaussian. Simultaneously, Coalescence of the PDMS droplets was suppressed efficiently by the silica nanoparticles. It was proposed that with this blending procedure the nanoparticles should be mainly kinetically trapped at the interface or in the PDMS dispersed phase, which provides an efficient steric barrier against Coalescence of the PDMS dispersed phase. However, bimodal droplet size distributions in the early stage of Coalescence still occur when incorporating silica nanoparticles into the blends with procedure 2, and then Coalescence of the PDMS droplets cannot be suppressed efficiently by the silica nanoparticles. It was proposed that with this blending protocol the nanoparticles should be mainly located in the PBD matrix phase, which leads to an inefficient steric barrier against Coalescence of the PDMS dispersed phase; thus the morphology evolution in these filled blends is similar to that in pure blend and bimodal droplet size distributions can be observed during the early Coalescence.

关键词： Droplet size distribution Immiscible polymer blends Coalescence Silica nanoparticles.

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