气液界面传质机理

提出了气液相际传质的推动力来源于界面不平衡的概念.针对气体吸收过程, 以普遍化的化学势推动力方程为基础, 导出了在有传质通量存在下的两相界面处的浓度关系,并针对不同情况进行了求解.提出了一个反映液相侧动力学状况的量纲1数Yo ,Yo越大界面处两相越偏离平衡.界面浓度是与Yo和液相主体浓度密切相关的.为验证本文模型, 作者采用显微激光全息干涉技术对甲醇、乙醇、正丙醇静止吸收CO₂时的界面浓度进行了测定, 实验结果表明了本文模型的正确性.     

吸收过程的界面非平衡传质机理

针对气体吸收过程,以分子热力学为基础,结合普遍化的化学势推动力通量方程,导出了传质存在时两相界面处的浓度关系,并针对不同情况进行了求解.提出了一个反映液相侧动力学状况的无因次数群Biot数Yo,Yo数越大界面处两相越偏离平衡.界面浓度是与Yo和液相主体浓度密切相关的.对于气相阻力可以忽略的吸收过程,两相传质速率的大小主要取决于液相的溶质界面浓度和液膜厚度.采用激光显微全息干涉技术对甲醇,乙醇,正丙醇静止吸收CO2时的界面浓度进行了测定,试验结果表明了本研究模型的正确性.     

气液传质过程的界面湍动

界面湍动对相际传质具有重要影响。利用显微激光全息干涉技术研究了 CO2 在乙醇 -水溶液中吸收过程的界面湍动情况 ,实验观察了界面湍动强度与溶液浓度的关系 ,结果表明 ,乙醇浓度越高 ,界面湍动强度越大 ,文中对此进行了分析和讨论。     

吸收过程的界面传质机理

以分子热力学为基础 ,对气体吸收过程进行了理论分析 ,导出了传质通量的数学表达式。根据该文分析 ,气液界面传质的源动力来自界面处气液两相的不平衡 ,即只要有传质发生 ,液相界面处的浓度就不会达到与气相呈平衡的浓度。对于气相阻力可以忽略的吸收过程 ,两相传质速率的大小主要取决于液相的溶质界面浓度和液膜厚度 ,影响溶质界面浓度和液膜厚度的主要因素是近界面液相侧的流场分布。利用近界面浓度与液膜厚度的激光测定结果 ,计算了甲醇、乙醇及正丙醇吸收CO2 气泡的传质通量 ,计算结果与实验值吻合良好     

气泡传质过程近界面非稳态特性及热力学研究

利用实时显微激光全息干涉测试技术 ,对运动气泡传质过程近界面的非稳态特性及浓度分布进行了实验测定 ,讨论了近界面湍动性质、稳态性质、非平衡性质及其关系 ,考察了流速、泡径、温度等因素对气泡传质过程的影响     

全息干涉法对气液流动浓度边界层的实验观测

引言 早期的界面浓度分布观测多采用加入示踪剂的方法[1-4].但由于示踪剂的加入对传质会造成干扰,影响了测量的可靠性.     

单泡吸收过程的界面传质机理

This paper focuses on the mechanism of interfacial mass transfer of a single bubble, based on the chemical potential driving force, an approach for calculating interfacial concentration in practical process is proposed. The absorption processes of bubble under both quiescent and mobile conditions are analyzed and discussed respectively. For a stationary absorption, only in the case of liquid bulk concentration near saturated value, the interfacial concentration could close to the equilibrium value ; For a moving bubble, under ordinary operating condition （Yo〉l）, the interfacial concentration is far from its equilibrium. Only under bulk concentration near saturated value or a smaller Yo（Yo〈0.1） which may involve the complication of additional resistance at interface induced by surface contamination or surfactant added, the interfacial concentration could be approximate to equilibrium value. The interfacial concentration close to the interface on liquid side for a single CO2 bubble absorbed by methanol is measured using a modern optical instrumentation in which the laser holographic interference method is adopted with a real-time and amplification technique. Experimental results show that the interfacial concentration decreases significantly with increasing Re and is far from the equilibrium one in a larger Re range. Experiments validate the proposed model.     

吸收过程的界面传质机理

Based on the method of molecular thermodynamics ,the mass transfer mechanism at gas-liquid interface is studied theoretically,and a nowe mathematical model is proposed,Using laser holographic interference technique,the hydrodynamics and mass transfer characteristics of CO2 absorption are measured,It is shown that the calculated results are in good agreement with the experimental data.     

自由界面气液传质系数的旋涡作用模型

在单涡模型的基础上 ,根据各向同性湍流的能谱函数 ,考虑不同尺度的旋涡对气液传质的影响 ,建立了气液自由界面传质系数模型 .模型计算结果与管道流及搅拌反应釜的实验结果吻合较好.     

液液传质界面扰动现象的全息实时记录

本文介绍了实时记录液液传质界面扰动现象全息图的方法，两相界面更新进发的周期及影响全息图实时记录质量的因素，为深入研究液液传质界面扰动现象的规律及机理开辟了一条新的途径。     

Studies on the liquid-liquid interfacial mass transfer process using holographic interferometry

This paper aims at the interfacial phenomena of liquid-liquid mass transfer and its characteristic. By using the real-time holographic technique, the concentration distributions on the aqueous side were obtained according to holographic diagrams of mass transfer of ethanol through the interface of oil and water at different initial concentrations. Furthermore, the concentrations near the interface and the mass transfer coefficients were attained. A correlation of concentration near the interface to the concentration of the solute in the oil side was proposed. An approach of interfacial energy with solute concentration was established, and the calculated results are at good agreement with the experimental data. It is indicated that the liquid-liquid mass transfer process is approximately in accordance with two-film theory, the interfacial performance may be changed by the addition of the solute, and the interface of liquid-liquid is nonequilibrium thermodynamically during the mass transfer process. __________ Translated from Chemical Engineering (China), 2007, 35(6): 1–3 [译自: 化学工程]     

Studies on the liquid-liquid interfacial mass transfer process using holographic interferometry

This paper aims at the interfacial phenomena of liquid-liquid mass transfer and its characteristic. By using the real-time holographic technique, the concentration distributions on the aqueous side were obtained according to holographic diagrams of mass transfer of ethanol through the interface of oil and water at different initial concentrations. Furthermore, the concentrations near the interface and the mass transfer coefficients were attained. A correlation of concentration near the interface to the concentration of the solute in the oil side was proposed. An approach of interfacial energy with solute concentration was established, and the calculated results are at good agreement with the experimental data. It is indicated that the liquid-liquid mass transfer process is approximately in accordance with two-film theory, the interfacial performance may be changed by the addition of the solute, and the interface of liquid-liquid is non-equilibrium thermodynamically during the mass transfer process.     

基于浓度/速度场测量的吸收过程液相传质系数

针对矩形流道内气、液流体的并流吸收传质过程,分别应用实时激光全息干涉术和激光多普勒速度仪对不同气、液流速下液相内近界面浓度分布与速度分布进行了实验观测.结果表明,边界层内浓度分布呈指数下降,流速越大梯度越陡,且速度边界层厚度要大于浓度边界层厚度.建立了通过物料衡算求算液相传质系数的方法.得到了不同条件下平均液相传质系数,并与Whiteman’s双膜理论的计算结果进行了比较.     

Interfacial mass transfer in stripping of phenylalanine in a liquid-liquid extraction process

Stripping of L-phenylalanine from organic phase containing ALIQUAT 336 (tri-octyl-methyl-ammonium chloride) as complexing agent was studied using a stirred transfer cell. The study investigated the effects of concentration of the stripping agent, potassium chloride, in strip solution and temperature on mass transfer rates. A two-film model based on organic and aqueous phases mass transfer resistances was proposed to estimate mass transfer coefficients and it predicted adequately the experimental time-concentration data at different conditions studied. A comparison of mass transfer coefficients for stripping and previously published results on extraction for the same system was made.     

Determination of dynamic interfacial tension in a pulsed column under mass transfer condition

Interfacial tension is an essential physical property in two-phase flow, and it changes due to the mass transfer. The measurement of dynamic interfacial tension (DIFT) in such a condition is a difficult problem. In the previous study (Zhou et al., Chem Eng Sci. 2019; 197:172–183), we presented the quantitative relation between the droplet breakup frequency function (DBFF) and interfacial tension. It is found that the DBFF is highly depended on interfacial tension. Therefore, the DBFF is a suitable parameter to quantitatively characterize the interfacial tension. Based on this concept, the DIFT in the column is determined by regression method after the DBFF under mass transfer condition is measured. It is found that the DIFT is smaller than the static interfacial tension. This result indicates that interphase mass transfer leads to decreasing of the interfacial tension. The decreasing extent of the DIFT has a positive correlation with the mass transfer flux.     

基于全息术的水平偏置椭圆管自然对流换热

采用全息术实验研究水平偏置椭圆管层流自然对流换热,分析了长轴从水平方向到竖直方向不同角度的换热规律,记录了无限大空间水平椭圆管偏置角为0°~90°的干涉图,通过反演椭圆管周围的温度场得到了椭圆管表面的局部和平均Nusselt数。实验结果表明,长轴从水平位置偏置到竖直位置时,换热逐渐增强;长轴位于水平位置和竖直位置时,换热最小值均位于椭圆管上方,最大值则位于椭圆管长轴附近。研究结果与文献中已有的数值和实验结果吻合较好,可为今后热管换热器的设计提供优化方向,也可为工程应用提供检测方法。     

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。     

Study on the transient interfacial tension in a microfluidic droplet formation coupling interphase mass transfer process

In two‐phase dispersion coupling interphase mass transfer process, the variation of interfacial tension is an important factor affecting the dispersion. In this study, we described a microfluidic method for the determination of the transient interfacial tension (TIFT). The method has the advantage of determining TIFT during the whole droplet formation process, rather than only at the rupture moment as reported in previous studies. The TIFTs of several systems were determined. In certain systems, it has been found that the droplet size decreased with the increase of the dispersed phase flow rate, which is obviously different from the constant interfacial tension system. It has also been found that TIFT was mainly affected by two‐phase flow rates, solute type and concentration, and droplet size. A semiempirical equation was finally established to predict TIFT. It has the potential to be used in a variety of industrial equipment with dispersion–mass transfer coupling process. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2542–2549, 2016