表面张力对自由落体液滴形变的影响

液滴运动过程中的形状变化对液滴的蒸发、燃烧等过程有重要影响,表面张力是影响其形状变化的因素之一。为研究表面张力对液滴形变的影响规律,采用低浓度的表面活性剂(十二烷基苯磺酸钠SDBS)配制表面张力为30~72 m N·m~(-1)的水溶液。利用不同外径的针管得到3~5 mm粒径的液滴。高速摄像机(Phantom V211,1000 pps,800×600 pixel)对这些液滴在自由落体过程中的形变规律进行了可视化实验研究,得到了关于E?tv?s数(Eo)的半经验关系式。实验结果表明,液滴在自由落体过程中会形成周期性振动形变,振动周期和振幅随表面张力增大而减小。进一步研究发现,初始时液滴形成并断裂所引起的瞬态冲量使液滴内部动量传递进而表现出周期性振动形变。     

关于表面活性剂水溶液的表面张力

本文由表面活性剂本身的化学结构和溶液表面吸附层的分子排列、构型，考查分析了表面活性剂的一个极其重要的性质——水溶液的表面张力。得出“表面活性剂水溶液表面最外层基团的本性是决定表面张力的主要因素”的结论，提供预测溶液表面张力的原理与规律。     

SDBS的表面张力对天然气水合物生成的影响

利用德国KRUSS公司生产的界面张力仪K11中的板法测定十二烷基苯磺酸钠在不同温度(5,10,20,30,35℃)和不同浓度下(100,400,800,1200,1600,2000 mg/L)的表面张力,确定有利于天然气水合物合成的最佳浓度为1 200 mg/L,这在工业应用中有着重要的参考价值,同时分析了表面活性剂加速天然气水合物生成的机理。     

不同反应条件及表面活性剂对氨水表面张力的影响研究

采用铂金板法测定了不同浓度、温度及不同表面活性剂条件下氨水溶液的表面张力值,并用高速摄像机记录铂金板浸入、脱离液体过程的浸润高度。结果表明,温度或浓度的变化均与氨水溶液的表面张力值呈现不同程度的负相关关系。在20.5～45℃范围内,不同浓度氨水的表面张力值下降幅度在9.17%～11.48%;随着氨水浓度在0～25%范围内增加,溶液表面张力值逐渐下降,降幅达15.20%;不同表面活性剂的加入可显著降低氨水的表面张力值,10%浓度的氨水表面张力值降幅最高达46.18%;所有测量结果中铂金板的浸润高度和面积值与表面张力值变化呈相反趋势。     

关于阳离子表面活性剂水溶液表面张力的测定

本文自实验结果说明,阳离子表面活性剂水溶液表面张力的测定应当采用适当的方法,否则将得出不正确的表面张力数据,从而得到错误的有关阳离表面活性剂表面活性的结论。     

非理想二元混合表面活性剂体系的表面吸附和表面张力方程

将非理想混有附理论与Ｓｚｙｓｚｋｏｗｓｋｉ方程相结合建立了二元混合活性剂体系的表面张力方程。应用于四个阴／阳离子二元表面活性剂混合体系，理论计算结果与实验结果完全符合，混合体系在表面张力降低效率方面的中 效应可以中表面有附自由能的下降和碳氢链在界面所占面积的减小来解释边四个体系是十圩醇聚氧乙醚硫酸三惭醇铵分别（１）十二烷基三甲基溴化铵，（２）十二烷基吡啶氯化物，（３）十六烷基三甲基溴化铵和（４）十     

水性集装箱涂料的动态表面张力解决方案

对水性集装箱涂料在高速施工过程进行了表面行为分析,揭示了涂料的动态表面张力在施工过程中的重要性,并通过实验验证了不同动态表面张力引起的表面缺陷。表述了动态表面张力的测试原理,并且通过动态表面张力对比测试、起泡性对比测试,找到了能够有效控制水性集装箱涂料动态表面张力的表面活性剂。     

时间效应在悬滴法测定表面张力中的影响

表面张力是流体重要的物理性质,测定表面张力的方法通常包括毛细管上升法、最大气泡压力法、拉环法、旋滴法和悬滴法等。目前,最普遍的表面张力的测定方法为国家标准推荐的平板法或拉环法。然而,悬滴法作为一项成熟的表面张力测定方法且具备静态表面张力及动态表面张力测定功能,目前使用该法测定的较少。文章使用悬滴法测定较低含量的表面活性剂溶液静态表面张力时发现结果与拉环法差异较大,而测定单组分液体及含量较大的表面活性剂溶液,悬滴法与拉环法的测定数据差异较小,这种情况的相关报道较少。另外,使用动态表面张力测定探索了静态测定时出现差异的原因,并对应用悬滴法进行表面张力测定的适用范围进行了总结。使用悬滴法测定表面张力时,应注意时间效应的影响。     

十二烷基苯磺酸钠表面张力的研究

通过表面张力的测定,研究了浓度、温度对溶液表面张力的影响,同时考察无机盐浓度对溶液表面张力的影响.结果表明:十二烷基苯磺酸钠溶液表面张力随浓度的增加、温度的升高和无机盐浓度逐渐的增大而降低,最终确定其CMC值为1.47×10-3mol/L,由于键能和水合离子半径的原因,NaCl对十二烷基苯磺酸钠表面张力的影响明显于KCl.     

表面张力对传质过程的影响

表面张力对传质过程的影响主要是影响传质界面积,当物系为正物系时,对板式塔有较小较稳定的汽泡,对填料塔和湿壁塔,有较稳定的液膜,结果使二者均有较大的传质界面积,传质效果较好;负物系的情况相反。当液体混合物的平均表面张力较小时,也有利于形成较小较稳定的汽泡,从而有利于传质。表面张力对传质过程的影响机理相当复杂,这方面的研究工作有待深入开展。     

The effect of surfactants on deformation of falling non‐Newtonian drops in a Newtonian liquid

Deformation of settling non‐Newtonian ellipsoidal drops in a Newtonian liquid was experimentally observed. Corn oil was used as the Newtonian phase and solutions of polyacrylamide in aqueous glycerine as the non‐Newtonian phase. The shear‐thinning behaviour of the drops fluid was controlled by the amount of polymer dissolved, while the effect of interfacial tension was examined using different concentrations of sodium dodecyl sulphate (SDS). In the range of 1 < E < 2.9, 0.2 < Eo, < 23, and 0 < Ma < 17.2, drop eccentricity increased linearly with a modified Eötvös number taking into account the effect of surfactants. For the range of experimental conditions tested, drop deformation was mainly controlled by viscous and interfacial tension forces, while shear‐thinning and inertia effects were negligible.     

Interfacial tension from the height and diameter of sessile drops and captive bubbles with an arbitrary contact angle

A method has been developed to calculate the interfacial tension of sessile drops and captive bubbles of arbitrary contact angle by measuring the drop diameter and vertical distance to the apex at arbitrary horizontal planes within the drop. The procedure works in theory for any contact angle with an accuracy on the order of 0.1%. However, practical limitations reduce the range of angles to roughly 50°–180° but do not restrict the range of interfacial tensions (at least 0.01 mJ/m² to 72.0 mJ/m²). The optimal strategy is to use the method at several points on a single drop and to calculate the mean and standard deviation of the resulting interfacial tensions.     

The effect of viscosity on surface tension measurements by the drop weight method

Viscosity is one of the parameters affecting the measured surface tension, as fluid mechanics affects the measurement process using conventional methods. Several methods including the selected planes (SPM) and WDSM which combines the weight drop method (WDM) and SPM, are applied to surface tension measurement of high viscous liquids. Yet, none of them treats the viscosity effect separately. The current publication presents a simple, easy to apply empirical approach of satisfactory accuracy, for evaluation of surface tension of liquids having wide range of viscosities up to 10 Pa s. The proposed method is based on Tate's law and the “drop weight” method using calibration curves of known liquids having similar surface tensions but different viscosities. Drop weight of liquids having viscosity ≥0.05 Pa s, was found to be significantly affected by the liquid viscosity. The shape factor, f, of high viscosity liquids was found to correlate linearly with the logarithm of viscosity, pointing the importance of viscosity correction. The experimental correlation presented in the current work can be used as a tool for the evaluation of surface tension for high viscosity liquids such as prepolymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Simulation of SO2 absorption by falling water drops

The experimental data of Walcek et al. (1981) for SO₂ absorption by falling water drops of 600 μm dia. at 13-15°C and 1-50 vol% SO₂ in air can be well predicted by a model which ignores the effect of internal circulation and considers the diffusion of both SO₂H₂O and HSO₃ and the accompanying equilibrium dissociation reaction of SO₂.H₂O within the drop. The data can also be described by the analytical solution obtained by simplifying the rigorous model with the assumption that the gas phase mass transfer resistance is negligible and that the difhtsivities of sulfur species are equal.     

Numerical simulation on wave behaviour and flow dynamics of laminar‐wavy falling films: Effect of surface tension and viscosity

Numerical simulation has been made on wave behaviour and flow dynamics of falling films of aqueous lithium bromide solution along a vertical wall in the present study. Volume of fluid model is used to track the free surfaces and continuum surface force model is used for dynamic boundary conditions considering the effect of surface tension. A small amplitude forcing perturbation is introduced at the inlet of the flow boundary. Effect of surface tension and viscosity on wave behaviour and flow dynamics has been investigated. The simulation results indicate that wave peak height decreases with increasing surface tension and the number of capillary waves in front of a large wave increases. With the decrease of viscosity wave shape changes from the sinusoidal shape to the solitary one. Furthermore, the flow dynamics underneath the typical waves are analysed, especially the pattern of backflow. © 2011 Canadian Society for Chemical Engineering     

不混溶液体表面上蒸发液滴的动力学特性

针对不混溶均匀受热液体表面上蒸发液滴的动力学过程,基于润滑理论推导出了无量纲方程组。采用数值模拟方法,探究了蒸发液滴的动力学特性。结果表明,蒸发液滴的演化过程分为两个阶段:由"铺展主导"的液滴前进阶段和由"蒸发主导"的持续脉动振荡的后退阶段。液滴在低黏度比下的流动性更强,导致铺展更加迅速,黏度比的增加会导致铺展和收缩速率的降低。蒸发通过影响液滴界面的温度分布进而影响界面张力以及液滴铺展。相较于固体表面液滴蒸发出现的钉扎现象,蒸发液滴在不混溶液体表面上的铺展是去钉扎的,并且伴有液体基底的明显变形。     

表面活性剂动态表面张力研究

利用动态表面张力研究方法,对不同质量比的烷基苯磺酸胺盐和椰子油二乙醇酰胺进了行研究,并利用2种数学模型对动态吸附数据进行分析,结果表明将吸附过程分成不同时区的数学模型能更好的体现表面活性剂的动态吸附过程,为表面活性剂在实际应用中的表现提供预测和参考。