Levelset方法数值模拟单液滴传质中的Marangoni效应

用Levelset方法捕获界面建立了数值模拟变形单液滴萃取传质过程中Marangoni效应的控制方程。将浓度场和流场相耦合计算,数值模拟了变形单液滴传质中的Marangoni效应,描述了Marangoni效应的发生和发展过程,结果同Sternling ＆ Scriven的经典理论分析和前期数值模拟相吻合。     

Marangoni效应与液膜振荡*

本文系统地总结了Marangoni效应的形成、发展及其与液膜振荡现象的关系,用Marangoni效应定量分析讨论了3种不同的液膜振荡体系,给出了有关数学公式,并与液膜振荡的化学本质学说作了对比。     

界面现象与液滴聚并

报导了一个受溶质Marangoni效应影响的液滴聚结的迟缓现象．采用示踪液滴法，对滴加在正戊醇水溶液表面、受自发界而流控制的硝基乙烷液滴的运动和存在状态进行了研究．结果显示，在一定体系中溶质Marangoni效应可导致液滴的悬浮态，并对液滴的聚并产生显著影响．由于界面状态的不同，示踪液滴也表现出完全不同的动力学特征．基于以上认识对液滴运动速率的计算得到了合理的结果．     

《分子发射光谱分析》

正本书集成了分子发射光谱分析光物理基础领域新进展和作者多年的研究成果,是一部具有理论创新、对学科发展和科技人才培养有重要作用的系统性理论著作。主要内容包括:荧光光物理基础,分子结构与发射辐射光物理过程,溶剂效应和溶剂化动力学与发射辐射光物理过程,质子转移、温度和黏度与发射辐射光物理过程,电荷转移跃迁,溶液和     

分子工程和化学工程

分子工程从分子水平研究产品的设计和开发以及过程的设计和开发问题,在化学工程领域中,是一个活跃的前沿。它的重要基础是分子结构与热力学性质、传递性质以及反应动力学性质之间的定量关系。研究这些关系分别是分子热力学、分子传递现象和分子反应动力学的任务。本文着重讨论它们的进展。     

化工传递过程中的类似性

通过分析化工过程中的传递现象 ,总结了动量传递、热量传递和质量传递过程的一些类似性 ,并且讨论了这些类似性的理论和应用价值。     

气候变化中的化学问题

气候变化是一个复杂体系中的科学问题。探讨大气中化学组分及化学过程的气候效应是目前这一研究的活跃领域。大气氧化剂和颗粒物是我国城市和区域大气中的关键污染物,在气候变化中也具有不容忽视的作用,分析和估算其直接和间接的气候效应,有助于丰富和完善对气候变化过程的科学认识。     

旋转填充床的流体力学特性与传递过程的理论研究进展

旋转填充床(RPB)是一种高效的强化传递过程设备，亦是一种高效的混合与多相反应设备，在化工、材料、冶金、能源、环保等领域有着广泛的应用前景。本文概要地介绍了近年来对该类装置的流体力学特性和传递过程的理论研究进展。     

两性离子聚合物的生物应用

两性离子聚合物具有亲水的阴、阳离子基团,能够高度水化从而具有独特的抗生物污染性能,即能够阻抗非特异性蛋白质的吸附、细菌黏附和生物膜的形成,这种特性使得此类材料在生物医学等相关领域得到越来越多的应用。本文概略介绍了现有两性离子聚合物的抗生物污染机理——空间排斥效应和水化理论。基于抗生物污染性质,两性离子聚合物可用于防污涂层、抗菌涂层、抗凝血材料、生物医学诊断、药物传输、基因传递载体、分离膜以及船体涂料中。本文综述了两性离子聚合物的应用进展,分析了当前研究中需要解决的问题以及发展趋势,并展望了其应用前景。     

超疏水模型及其机理

超疏水表面是指具有非常高的水接触角,且水滴能轻易流动的表面。由于超疏水表面具有自清洁、防黏附、防雪黏等功能,在许多领域中用途广泛,有关超疏水表面制备和理论研究成为研究的热点。特别是有关超疏水表面的理论,由于涉及表面结构的优化设计,更受到了广泛的关注。本文综述了近年来超疏水理论的新进展,重点归纳了一些具有代表性的理论,如经典的Wenzel理论和Cassie理论、过渡态的产生及如何避免过渡态的问题、接触线理论、多尺度效应等,对各个理论的优缺点进行了系统地比较和评价,另外,对一些热点关注问题也进行了综述,并对超疏水理论的未来发展方向进行了展望。     

Numerical simulation of Marangoni effects of single drops induced by interphase mass transfer in liquid-liquid extraction systems by the level set method

The mathematical model of mass transfer-induced Marangoni effect is formulated. The drop surface evolution is captured by the level set method, in which the interface is represented by the embedded set of zero level of a scalar distance function defined in the whole computational domain. Numerical simulation of the Marangoni effect induced by interphase mass transfer to/from deformable single drops in unsteady motion in liquid-liquid extraction systems is performed in a Eulerian axisymmetric reference frame. The occurrence and development of the Marangoni effect are simulated, and the re- sults are in good agreement with the classical theoretical analysis and previous simulation.     

添加剂对LiBr溶液吸收蒸汽过程中的强化机理

The surface tensions of aqueous lithium bromide（LiBr）with additive（2-ethyl-1-hexanol and 1-Octanol）have been measured by using a Wihelmy plate method,and the enhancement effect of the additives on the absorption of steam into aqueous LiBr in a static pool has been studied by a real-time type laser holographic visualization method. The experimental results show that both of liquid additive and vapor additive can decrease the surface tensions of aqueous LiBr significantly,vapor additive not only can trigger the Marangoni convection at the absorption interface just like the liquid additive,but can bring about better enhancement effect on the absorption performance than that liquid additive can. The enhancement mechanism of additive on absorption has been concluded that both liquid additive and vapor additive can be adsorbed by aqueous LiBr at the liquid-vapor-interface from the liquid side and the vapor side respectively,which result in surface tension gradient,and then cause Marangoni convection at the interface which enhances the heat and mass transfer performance during the absorption process.     

Mass transfer model of triethylamine across the n-decane/water interface derived from dynamic interfacial tension experiments

This publication presents a detailed experimental and theoretical study of mass transfer of triethylamine (TEA) across the n-decane/water interface. In preliminary investigations, the partition of TEA between n-decane and water is determined. Based on the experimental finding that the dissociation of TEA takes place in the aqueous and in the organic phase, we assume that the interfacial mass transfer is mainly affected by adsorption and desorption of ionized TEA molecules at the liquid/liquid interface. Due to the amphiphilic structure of the dissociated TEA molecules, a dynamic interfacial tension measurement technique can be used to experimentally determine the interfacial mass transport. A model-based approach, which accounts for diffusive mass transport in the finite liquid bulk phases and for adsorption and desorption of ionized TEA molecules at the interface, is employed to analyze the experimental data. In the equilibrium state, the interfacial tension of dissociated TEA at the n-decane/water interface can be adequately described by the Langmuir isotherm. The comparison between the theoretical and the experimental dynamic interfacial tension data reveals that an additional activation energy barrier for adsorption and desorption at the interface has to be regarded to accurately describe the mass transport of TEA from the n-decane phase into the aqueous phase. Corresponding adsorption rate constants can be obtained by fitting the theoretical predictions to the experimental data. Interfacial tension measurements of mass transfer from the aqueous into the organic phase are characterized by interfacial instabilities caused by Marangoni convection, which result in an enhancement of the transfer rate across the interface.     

Effects of experimental sample mass on the calorimetric study of thermoset resins

It is known that experimental parameters may affect peak characteristics in DSC studies. Kinetic parameters calculated from isothermal and dynamic runs, can also be affected by the choice of experimental conditions.The sample mass can affect the determination of reaction parameters because of the heat transport and the self-insulating properties of large masses.In the curing process of thermoset resins like unsaturated polyester crosslinked by styrene, the exothermal heat results from the reaction advance but it also produces an autocatalytic process that induces an increase in the reaction rate. The sample mass, in this kind of experiments, can influence the determination of reaction parameters not only through the effect of heat transport or thermal lag on the calorimetric results but also through the action that the sample mass exerts on the exothermal heat, and consequently, on the autocatalytic process.In this paper we intend to present the results obtained in the study of the curing kinetics of thermoset resins by DSC technique using different sample masses. We will point out that the reaction heat determined by dynamic measurement was found to be independent of the sample mass. We have obtained differences in the kinetic parameters like the reaction order, activation energy and preexponential factor when the sample mass was changed.The research reported was supported by CICYT under Grant no. MAT89-377-C02-02.     

Ionic liquid-based stable nanofluids containing gold nanoparticles

A one-phase and/or two-phase method were used to prepare the stable ionic liquid-based nanofluids containing same volume fraction but different sizes or surface states of gold nanoparticles (Au NPs) and their thermal conductivities were investigated in more detail. Five significant experiment parameters, i.e. temperature, dispersion condition, particle size and surface state, and viscosity of base liquid, were evaluated to supply experimental explanations for heat transport mechanisms. The conspicuously temperature-dependent and greatly enhanced thermal conductivity under high temperatures verify that Brownian motion should be one key effect factor in the heat transport processes of ionic liquid-based gold nanofluids. While the positive influences of proper aggregation and the optimized particle size on their thermal conductivity enhancements under some specific conditions demonstrate that clustering may be another critical effect factor in heat transport processes. Moreover, the remarkable difference of the thermal conductivity enhancements of the nanofluids containing Au NPs with different surface states could be attributed to the surface state which has a strong correlation with not only Brownian motion but also clustering. Whilst the close relationship between their thermal conductivity enhancements and the viscosity of base liquid further indicate Brownian motion must occupy the leading position among various influencing factors. Finally, a promisingly synergistic effect of Brownian motion and clustering based on experimental clues and theoretical analyses was first proposed, justifying different mechanisms are sure related. The results may shed lights on comprehensive understanding of heat transport mechanisms in nanofluids.     

Peristaltic activity in blood flow of Casson nanoliquid with irreversibility aspects in vertical non-uniform channel

Due to the illuminating function of nanoliquids in several technological and medicinal domains, particularly in liquid transport processes known as peristalsis, inquisitive researchers have investigated the flow of peristaltic nanofluids. Consequently, the current study investigates the entropy production and magnetic influence on the peristaltic transport of heat and mass transport of Casson nanofluid in a non-uniform channel under convective circumstances. Utilizing the perturbation approach, fields of concentration, temperature, and velocity are derived from non-linear coupled partial differential equations (PDE). Entropy generation studies have been done. In addition, the influence of associated factors via specific physical terms, including the Sherwood number, the skin-friction coefficient, and the Nusselt number, for both Casson and Newtonian liquids, as well as the trapping phenomena, is visually examined.     

Membranes and theoretical modeling of membrane distillation: a review

Membrane distillation (MD) is one of the non-isothermal membrane separation processes used in various applications such desalination, environmental/waste cleanup, food, etc. It is known since 1963 and is still being developed at laboratory stage for different purposes and not fully implemented in industry. An abrupt increase in the number of papers on MD membrane engineering (i.e. design, fabrication and testing in MD) is seen since only 6 years ago. The present paper offers a comprehensive MD state-of-the-art review covering a wide range of commercial membranes, MD membrane engineering, their MD performance, transport mechanisms, experimental and theoretical modeling of different MD configurations as well as recent developments in MD. Improved MD membranes with specific morphology, micro- and nano-structures are highly demanded. Membranes with different pore sizes, porosities, thicknesses and materials as well as novel structures are required in order to carry out systematic MD studies for better understanding mass transport in different MD configurations, thereby improving the MD performance and looking for MD industrialization.     

An Insoluble Surfactant Model for a Vertical Draining Free Film

A mathematical model is constructed to study the evolution of a vertically oriented thin liquid film draining under gravity when there is an insoluble surfactant with finite surface viscosity on its free surface. Lubrication theory for this free film results in three coupled nonlinear partial differential equations describing the free surface shape, the surface velocity, and the surfactant transport at leading order. We will show that in the limit of large surface viscosity, the evolution of the free surface is that obtained for the tangentially immobile case. For mobile films with small surface viscosity, transition from a mobile to an essentially immobile film is observed for large Marangoni effects. It is verified that increasing surface viscosity and the Marangoni effect retard drainage, thereby enhancing film stability. The theoretical results are compared with experiment; the purpose of both is to act as a model problem to evaluate the effectiveness of surfactants for potential use in foam-fabrication processes. Copyright 2000 Academic Press.     

锂离子电池多孔电极理论的回顾与新思考

本文总结了Newman多孔电极理论的基本内容,提出若干改进思路. 提出基于离子-空穴耦合传输机制描述浓电解质中的离子输运过程,在此基础上引入离子-电子耦合转移反应的思想处理电极材料中的离子传输问题,并通过计算嵌锂材料的离子扩散系数验证其合理性. 总结了描述多孔电极多尺度结构的相关理论和技术,表明均质化方法和基于结构重建的介观模拟方法均能给出比较合理的有效输运参数,从而提高多孔电极理论模拟结果的准确性.