用密度泛函理论研究二元体系的液液界面张力

应用密度泛函理论和统计缔合流体理论建立了二元液液界面的状态方程 ,通过纯流体汽液平衡时的压力数据和液相密度数据回归了非极性流体和极性流体的链节参数 .将界面分层 ,使用已建立的状态方程和回归的纯流体链节参数 ,根据界面各微层达到相平衡时化学势相等的原则计算了液液界面层的厚度和液液界面中的密度分布 ,预测了 16个水 -有机溶剂二元体系的液液界面张力 .计算结果与实验值符合情况良好 .     

液液界面传质过程的激光干涉法研究

为了研究液液传质过程的界面现象及传质特征,采用实时激光全息干涉技术,根据不同初始浓度时乙醇通过油水界面传质过程的全息干涉图,得到了传质过程水相侧的浓度分布,据此求出了近界面浓度和基于浓度的传质系数,并关联了近界面浓度与主体相溶质浓度的关系。建立了界面能随溶质浓度改变的函数关系,计算结果与实验值吻合良好。研究结果表明,液液静止界面传质过程基本符合双膜理论,溶质的加入能改变界面性能,传质过程界面处于非平衡状态。     

固液界面高分子吸附研究(Ⅰ)──模型的建立和检验

从常用密堆积格子模型导出了高分子溶液中自由高分子链节的几率表达式，在此基础上，通过类比的方法，建立了固液界面层中自由高分子链节的几率表达式，与DiMarzio-Rubin的高分子统计矩阵方法相结合，从而建立了基于密堆积格子的固液界面吸附模型．模型预测的高分子在界面层中的浓度分布与MC计算机模拟结果进行了比较，表明基于RevisedFreed和Guggenheim模型的固液界面吸附模型的计算结果比基于Flory-Huggins理论的模型计算结果，更接近于MC模拟值．     

固液界面高分子吸附研究(Ⅰ)──模型的建立和检验

从常用密堆积格子模型导出了高分子溶液中自由高分子链节的几率表达式,在此基础上,通过类比的方法,建立了固液界面层中自由高分子链节的几率表达式,与DiMarzio-Rubin的高分子统计矩阵方法相结合,从而建立了基于密堆积格子的固液界面吸附模型．模型预测的高分子在界面层中的浓度分布与MC计算机模拟结果进行了比较,表明基于RevisedFreed和Guggenheim模型的固液界面吸附模型的计算结果比基于Flory-Huggins理论的模型计算结果,更接近于MC模拟值．     

界面性质对气液传质的影响

界面性质对气液传质有重要影响。分子通过界面时需克服界面自由能，界面两侧的浓度不一致。本文导出了两者之间的关系     

液液界面法测超滤膜孔径及孔径分布

本采用液液界面法，利用毛细管现象测定了截留分子量为２×１０＾４和５×１０＾４聚砜超滤膜ＰＳ－２，ＰＳ－５的孔径及孔径分布。结果表明，利用水－正丁醇体系能测定超滤膜的孔径及孔径分布，并且具有操作简便，测试压力接近膜工作压力的优点，对于ＰＳ－２超滤膜，测试压力达０．５ＭＰａ即能得到膜完整的孔径分布曲线。     

液液自动分离装置在间歇生产工艺中应用探析

对液液自动分离系统进行了理论计算，并分析讨论了该装置应用于间歇生产中时，两相分界面移动的原因及设计时应注意的问题。     

表面活性剂在液固界面吸附的热力学

对已有的表面活性剂液固界面吸附等温线进行了系统的分类,并提出了非均匀表面两阶段吸附模型．用此模型导出的吸附等温方程式能很好地描述各种类型的吸附等温线.     

百时香酚兰的液液界面电化学研究

用循环伏安法研究了百里香酚兰在水／硝基苯界面的离子转移行为。根据百里香酚兰在溶液听 离解平衡和电化学性质，讨论了界面离子转移机理，并计算了转移离子的标准转移电位△0^Wψ^0和标准吉布斯转移能△0^WG^0。实验所测半波电位△0^Wψ1／2－pH曲线与理论公式相符。     

界面湍动对气液传质的影响

气液传质过程中经常伴有界面湍动。界面湍动由传质的不均匀性引起,反过来又极大地促进传质。介绍了界面湍动的产生机理和形成条件,对4种不同Ra和Ma准数的情况分别进行了分析。讨论了界面湍动强度对气液传质系数的影响关系。传质系数与Man成正比,其中n随着Marangoni对流胞类型的不同而在1/3和1之间变化。在气液系统中,液相与气相阻力比越大,由界面湍动引起的传质的增强效应越显著。     

小气泡或小液滴之间的聚并

对2个小气泡或小液滴之间的聚并进行了动力学分析,并考虑范德华力的影响,得到了界面无切向运动时气泡或液滴聚并所需时间与气泡直径、流体主体和界面性质的关系。     

表面粘度对小气泡聚并的影响

对2个小气泡间的聚并过程进行了动力学分析,着重考虑界面粘度的影响,得到气泡聚并所需时间与气泡直径、流体主体和界面性质的关系。     

COALESCENCE BETWEEN SMALL BUBBLES: EFFECTS OF SURFACE TENSION GRADIENT

1 INTRODUCTIONThe rate of coalescence between bubbles is important to the stability of foams,the mo-bility control in tertiary oil recovery,and a broad class of operations in which gas orvapor is the dispersed phase.Therefore,it is very important that the mechanism of thecoalescence process be understood,so that the effects of the physical properties oncoalescence can be assessed.     

The Experimental Observation and Modelling of Film Thinning and Film Retraction during the Interfacial Coalescence of Biodiesel and Glycerol Droplets

This paper is concerned with the way interfacial coalescence of a single drop of biodiesel or glycerol occurs at a glycerol/biodiesel interface. Two stages of interfacial coalescence were studied: the thinning of the trapped liquid film between the rising or falling droplet and bulk fluid interface, and the retraction of the film after the film had ruptured. Unexpectedly, the thinning time for the high viscosity glycerol film around a rising biodiesel droplet was found to be much shorter than that for a low viscosity biodiesel film around a sedimenting glycerol droplet. Squeeze flow modelling showed that the film of glycerol around a biodiesel droplet was bounded by relatively inviscid biodiesel and therefore flowed with high slip at its interfaces, resulting in rapid film thinning. The biodiesel film around a glycerol droplet was bounded by highly viscous glycerol and flowed with little slip at the interfaces, resulting in slower film thinning. After rupture, film retraction was found to be much faster for biodiesel droplets than for glycerol droplets. The drag exerted by the fluid surrounding the film was found to control the retraction kinetics. The results are of particular relevance to the separation of glycerol from biodiesel and of general relevance to coalescence kinetics for immiscible drops at an interface.     

An experimental study of factors which promote coalescence of two colliding drops suspended in water-I

The factors which determine whether two colliding drops will coalesce or rebound have been studied experimentally for 3.4 mm dia. anisole drops in water, using an apparatus designed to permit control of drop size, impact velocity and collision angle. Analysis of high speed movies showed that for relative approach velocities of 1.9–11.2 cm/sec, the apparent drop contact time was less than 70 msec. The probability of coalescence during this short time interval was a function of the phase and amplitude of the drop oscillations at moment of contact. The results have been analyzed using a modification of the conventional Stefan-Reynolds type film thinning equation derived for rigid interfaces. This relationship, although indicating more thinning for coalescences than rebounds, fails to predict fast enough thinning rates to validate the model. Part II gives detailed derivations for a thinning model in which interfaces are free to move, and shows how the results given in Part I can be explained by film thinning.     

液滴在斜板层膜上聚结时间的计算

在对聚结过程和分离界面处液滴与层膜流体力学特性分析的基础上,建立了单个液滴在斜板层膜上聚结时间模型,模型计算值与BlassE等人报道的实验结果误差小于10％。     

The behaviour of large gas bubbles at a liquid-liquid interface. Part 2: Liquid entrainment

The roles played by large gas bubbles in the generation and coalescence of liquid drops at a liquid-liquid interface are elucidated. The amount of lower liquid entrained by individual bubbles and the resulting drop size distributions in the upper liquid phase are quantified for the three phase system: sunflower oil + 50 wt % decane, water + 50 wt % sugar, air, and qualitative theoretical models are presented. Drops settling to the interface were found to coalesce rapidly and bubble flux had no apparent effect on the rate of drop coalescence at the liquid-liquid interface.     

RAPID COALESCENCE OF MERCURY DROPS AT PLANAR MERCURY-LIQUID INTERFACES

Two modes of coalescence were observed following impact of a mercury drop with a planar mercury interface in immiscible liquid-liquid systems. At low impact velocities slow stagewise coalescence occurred in the manner observed in many previous studies, while at high velocities coalescence occurred rapidly, within 0.05 seconds following impact. The probability of rapid coalescence increased from zero to one over a narrow velocity range. The critical velocity at which the rapid coalescence probability became 0.5 decreased with increasing drop diameter and decreasing continuous phase viscosity and was affected by drop oscillation for the largest viscosity continuous phase liquid studied.     

RAPID COALESCENCE OF MERCURY DROPS AT PLANAR MERCURY-LIQUID INTERFACES

Two modes of coalescence were observed following impact of a mercury drop with a planar mercury interface in immiscible liquid-liquid systems. At low impact velocities slow stagewise coalescence occurred in the manner observed in many previous studies, while at high velocities coalescence occurred rapidly, within 0.05 seconds following impact. The probability of rapid coalescence increased from zero to one over a narrow velocity range. The critical velocity at which the rapid coalescence probability became 0.5 decreased with increasing drop diameter and decreasing continuous phase viscosity and was affected by drop oscillation for the largest viscosity continuous phase liquid studied.     

Effect of geometrical arrangement and interdrop forces on coalescence time

According to the Reynolds' equation the time taken for a thin film to reach a critical thickness at which rupture occurs is a function of the film area and applied force. It follows that the coalescence time of a liquid drop is greatly affected by its geometrical configuration. If the drop is unconstrained the coalescence time increases when a vertical force is applied to the drop, but if the drop is constrained by the presence of surrounding drops its coalescence time decreases as the applied force increases. This explains why the rate of coalescence at the disengaging interface of a close-packed dispersion increases with the dispersion height. The coalescence time for a planar film is usually less than for the spherical film formed between a drop and its homophase which explains why near-horizontal surfaces inserted into close-packed dispersion increase the rate of coalescence. The coalescence time of a drop in a close-packed dispersion decreases as it approaches the disengaging interface. This means that the volume rate of coalescence at the interface may equal the disperse phase throughout without the necessity for interdrop coalescence. When the applied pressure is much greater than the van der Waals pressure, as in a close-packed dispersion, the critical film thickness is itself a function of the film area and applied force, but this has little effect on the above conclusions. When the applied pressure is much less than the van der Waals pressure, as in a loose-packed dispersion, the critical film thickness is only a function of the film area and the affect of the applied force on the coalescence time is then increased.