局部组成型的互扩散系数模型

根据局部组成概念建立了混合物中互扩散系数与自扩系数的关系,并以分子集团迁移的概念建立了混合物中组分的自扩散系数的预测方法,由此预测二元系的自扩散系数和互扩散系数与实验结果符合良好,比经典的Ｈａｒｔｌｅｙ模型有了很大地改进。     

数字全息干涉法测量二元溶液互扩散系数

由一维无限长扩散模型入手,建立了探测光相位与液体互扩散系数之间的数学模型,进而在现有数字全息干涉法的基础上,提出了一种新型的二元液体互扩散系数测量方法。由于该方法直接利用探测光相位求取互扩散系数,因此可有效避免外界噪声信号对实验结果的影响,从而降低了数字全息干涉法对外界光学环境的要求。该方法的互扩散系数测量相对合成不确定度为0.7%。测量了25℃下、0.33 mol/L KCl水溶液的互扩散系数,实验结果与文献值符合良好,验证了该测量方法的可行性。利用该方法,测量了甲醇/环己烷二元系在其不互溶区附近的互扩散系数,揭示了其在该区域的变化规律。依据实验数据,预测了该二元系的热力学亚稳定和非稳定区域的分界线--Spinodal曲线。     

Unsteady mass transfer around axisymmetric drops of revolution in variable diffusion coefficient liquids

Unsteady mass transfer in the continuous phase around axisymmetric drops of revolution at high Peclet numbers has been theoretically studied. The liquid is a binary system, having a variable diffusion coefficient, which depends on the solute concentration. The solution to the problem was obtained by extending the theory of Favelukis and Mudunuri, developed for a constant diffusion coefficient liquid. The procedure consists of transforming the differential mass balance, for a binary system, into a partial differential equation which has an analytical solution, and an ordinary differential equation that needs to be solved numerically. Solutions to a large number of problems can be immediately obtained with the only requirements being the shape of the drop, the tangential velocity at the surface of the drop and an expression for the variable diffusion coefficient liquid. An approximate analytical solution is also suggested which is in excellent agreement with the numerical results.     

Solubility of binary liquid mixtures in polymeric materials

Experimental data on the permeation of binary mixtures through polymeric materials show that liquid mixtures can exhibit large, positive synergistic rates. As the permeation rate depends on both solubility and the diffusion coefficient, the existence of a maximum in the steady-state permeation rate vs. the composition curve could be due to an increase in solubility and/or diffusion coefficient. In this study, a theoretical model based on the Flory-Huggins equation was developed to predict the solubility of binary liquid mixtures in polymers. The equation has four adjustable parameters that can be determined from solubilities of pure liquids in the polymer and the vapor-liquid equilibrium data for the binary liquid mixture. The model was tested for two binary liquid mixture/polymer systems. The predicted values of solubilities are close to the experimental data. © 1993 John Wiley & Sons, Inc.     

Correlations for prediction of diffusion in liquids

Based on an extensive experimental data collection (about 1925 points), empirical correlations for the estimation of binary liquid diffusion coefficients have been developed. The new correlations for organic mixtures and for aqueous solutions (including dissolved gases) require only well known and simple parameters like the viscosity of the solvent and the molar volumes of solute and solvent at the normal boiling point. They are shown to predict the limiting diffusion coefficients with the same or sometimes better accuracy than established correlations which make use of additional parameters. The concentration dependence of the mutual diffusion coefficients can be estimated from the knowledge of the two limiting diffusion coefficients and thermodynamic data. Established equations are investigated and classified for different groups of systems e.g. nonpolar + nonpolar, nonpolar + polar and polar + polar liquid mixtures.     

非电解质水溶液黏度的关联

许多化工过程的设计需要估算含水体系的黏度,但目前的黏度关联方法用于含水体系时误差较大.今以作者所在课题组近期提出的非水液体混合物黏度关联方程为基础,通过引入形状因子,得出了一个非电解质水溶液的黏度方程.该方程可用于二元非电解质水溶液黏度的关联,且能利用二元黏度得到的关联参数推算三元非电解质水溶液的黏度.该方程对54个二元非电解质水溶液体系黏度(总计2876个黏度数据点)关联的总平均相对偏差为4.60%;对7个三元非电解质水溶液体系黏度(总计352个黏度数据点)推算的总平均相对偏差为3.75%.结果表明,该方程具有较高的关联精度和推算精度.     

Self- and mutual diffusion coefficient equation for pure fluids, liquid mixtures and polymeric solutions

Transport properties are important information not only for industrial equipment design but also for many research areas. While there is a well-developed theory for gases at low densities, there is no established theory to calculate diffusion coefficients for dense fluids, especially for polymeric solutions. Recently, a database of 96 self-diffusion coefficient data points were obtained from molecular dynamics (MD) simulations for freely jointed Lennard-Jones chains (LJC) with lengths of 2, 4, 8 and 16 at reduced densities ranging from 0.1 to 0.9 and in the reduced temperature interval of 1.5 to 4. These data were used to develop an equation that correlates MD self-diffusion coefficient points with an overall absolute average deviation of 15.3%. The aim of this work is to show that this equation can be used to calculate diffusivities of pure liquids and liquid mixtures, including polymeric solutions. The proposed equation is used for correlating self-diffusion coefficients for 22 pure real substances and then for predicting mutual diffusion coefficients for 12 binary liquid mixtures. The proposed equation is also used to calculate mutual diffusion coefficients for polymeric systems as: polystyrene-toluene at 110 °C, poly(vinyl acetate)-toluene at 35 °C, and poly(vinyl acetate)-chloroform at 35 and 45 °C. Results show that the model developed here seems to be a promising approach for correlating mutual diffusion coefficients not only for small-molecule systems but also for polymer-solvent systems. One advantage of the equation proposed here is that the parameters have physical meaning and most of them can be estimated without any information on binary diffusion data.     

CORRELATION AND PREDICTION OF LIQUID DIFFUSION COEFFICIENTS IN BINARY SYSTEMS

A theoretical model to correlate and predict the liquid diffusion coefficients in binary sys-tems has been developed.Based on this mode1 the diffusion coefficient of 73 binary systems have beencorrelated,the overall average deviation of the correlation for diffusion coefficients is 0.009.Forbinary systems the diffusion coefficients have been predicted from vapor liquid phase equilibrium(VLE)and vice versa.     

从液体混合物的粘度数据推算汽液平衡数据

<正>液体混合物的汽液平衡数据和粘度数据都是基本的物性数据,人们很早就开始了对它们的研究,并取得了不小的进展.对于汽液平衡的研究,人们提出了许多溶液理论和活度系数方程,例如Flory-Huggins方程,Van Laar方程,Margules方程,Wilson方程和其修正方程,NRTL方程以及UNIQUAC方程等;对于液体混合物的粘度,人们也提出了许多流体粘度理论,其中最著名的是Eyring反应速率理论.作者曾应用这一理论建立了一个新的液体混合物粘度方程,用于关联二元体系的粘度数据和推算多元体系的粘度数据,结果令人满意.     

硬球理论用于液相扩散系数的关联

<正>硬球理论的基础是Maxwell－Boltzman的统计力学理论,最早由Chapman等将该理论应用于研究稀薄气体的传递性质。在稠密流体中,必须考虑分子碰撞频率大幅度增加的影响因素。 Dymond等认为该影响与分子接触径向分布函数g(σ)有关,并以此计算了     

Diffusion of solvent from a cast cellulose acetate solution during the formation of skinned membranes

The transport of solvent out of a cast cellulose acetate (CA) solution into the coagulation bath during membrane formation is treated as a diffusion process. From the increase of solvent concentration in the bath with time (solvent leaching experiments) an overall solvent diffusion coefficient has been calculated. In size these coefficients compare well to mutual pseudo-binary solvent-non-solvent diffusion coefficients determined by means of a classical boundary broadening method applied to ternary solutions with fixed CA concentration, but with a gradient in solvent-nonsolvent composition. Since binary polymer-solvent interdiffusion coefficients are at least one order of magnitude lower, it is concluded that the diffusion of solvent into the coagulation bath is essentially a pseudo-binary solvent-non-solvent diffusion process. Combination of experimental results with model calculations for the effect of a thin dense skin on the diffusion of solvent out of the sublayer shows that the casting-leaching diffusion coefficient can be used to describe the out-diffusion of solvent from the layer under the skin provided that the relative skin resistance is not too high, or that the skin thickness is small.     

液相扩散系数与浓度的单参数关联

提出一个液相扩散系数与浓度的单参数关联方程，参数与温度关系不明显，对３８个二元体系的５８６个实验数据点关联结果较好，平均偏差为１．４２％。     

非电解质水溶液的粘度方程

在Eyring的液体粘性流动模型基础上,根据Rother等的假定和Shealy与Sand ler的水溶液过量自由焓溶质聚集模型,导出了一个双参数非电解质水溶液的粘度模型。利用该模型可由二元水溶液的2个模型参数预测多元水溶液的粘度。用该模型计算了6个体系391个不同温度和组成的二元水溶液和3个体系164个不同温度和组成的三元水溶液的粘度,计算值与实验值的总平均相对偏差分别为1.732%和2.977%,计算值与实验数据吻合很好。     

Diffusion in binary liquid mixtures at infinite dilution

A correlation is presented for the mutual diffusion coefficient in a binary liquid system at infinite dilution. It has several advantages over previous correlations, and is recommended for diffusion in organic solvents. Some special cases where empirical correlations should be used with caution are discussed briefly.     

Rheological study of mixing in molten polymers: 1-mixing of low viscous additives

A new mixing device has been designed and developed in order to investigate complex mixing situations encountered in polymer blends and formulations. This mixing device called here rheo-mixer has been adapted on a classical rheometer and calibrated in terms of shear/stress that both permanent and dynamic regimes may be quantitatively run. The ability of the mixer to bring interesting information about complex polymeric systems was demonstrated by following the process of incorporation of a miscible liquid or partially miscible into a high viscosity polymer. As examples, EVA/diethyl 2-hexyl phtalate, poly(ε-caprolactone)/ε-caprolactone, and EVA/ε-caprolactone systems were tested.It was demonstrated that the viscosity ratio is not the predominant parameter for mixing process control because the mixing is mainly controlled by the diffusion for these low viscosity ratio systems (λ<10⁻⁵) as miscible systems (EVA/DOP and PCL/ε-CL) and partially miscible systems (EVA/ε-CL) are concerned. Actually, the mixing efficiency of these fluids is poor because the shear migration diminishes the rate of mixing due to a decrease of the deformation in the high viscous media. The mixing by thick striation is only effective when the viscosity ratio becomes, by the diffusion process, typically higher than 10⁻³. Furthermore, the discussion based on the mutual diffusion coefficient agrees well with the experimental finding, at least qualitatively.     

新的液相扩散系数模型

根据统计力学理论与Eyring绝对速率理论,建立了描述液相扩散系数的理论模型。该模型反映了温度、压力及组成对液相扩散系数的影响。基于此模型,建立了关联高压液相自扩散系数与密度关系的模型方程;导出了二元溶液相互扩散系数与浓度关系的计算方程;建立了计算无限稀释扩散系数的方程。通过对实际物系的验证计算,本文所导出的各方程均能很好地关联计算液相扩散系数,并优于文献方程。     

液体非电解质水溶液粘度的关联

在Teju-Rice液体混合物模型的基础上,对常用的液体混合物粘度关联式进行了分析和比较,导出了适用于二元和多元水溶液的粘度模型。用该模型计算了6个体系388个不同温度和组成的三元水溶液的粘度,计算值对文献实验数据的总平均相对偏差分别为6.09%和5.54%,计算值准确性优于Teju-Rice模型。     

Competitive adsorption of two dissolved organics onto activated carbon—III: Adsorption kinetics in fixed beds

Adsorption breakthrough curves for bisolute systems of dissolved organics on activated carbon are measured in fixed beds.Results for strongly adsorbable species indicate that at low liquid concentrations (X<0.1 mmol/l.) only external mass transfer resistance is rate determining.However, at higher liquid concentrations internal mass transfer becomes increasingly significant. Breakthrough behaviour is predicted using alternatively three different models with different assumptions about diffusion in the liquid filled pores and diffusion on the surface in series with external film diffusion.Multi-solute adsorption equilibria are predicted from single-solute data using the ideal adsorbed solution theory developed by Myers and Prausnitz, while the single-solute equilibria are represented by Freundlich isotherms. The external mass transfer coefficient for each component is calculated by a general correlation for heat and mass transfer in fixed beds. The internal diffusion coefficient for each component is determined in batch reactor tests with the single-solute system.Systematic deviations between measured breakthrough curves and those calculated from different models using only single-solute data are observed in all experiments with mixed solutes if there is significant internal diffusional resistance and marked displacement of one component inside the carbon particles. The deviations may be due to mutual interference of diffusing molecules. A better agreement between calculated and observed breakthrough curves can be obtained using an extended model in which mixture data are required.     

Estimating the self-diffusion and mutual diffusion coefficients of binary mixtures on the basis of a modified van der Waals model

The previously proposed model is used to determine the values of the self-diffusion coefficient of He, Ne, Ar, Kr, Xe, H₂, D₂, N₂, O2, CO₂, NH₃, and CH₄ in the liquid and dense gaseous states, which were compared with the experimental data obtained at a pressure of ≈200 MPa and a temperature of ≈500 K. The calculations are carried out with the use of the equation of state of these substances in the form of a modified van der Waals model. The self-diffusion model was generalized for the case of mutual diffusion in binary mixtures, which is based on the modified model of the van der Waals state equation for mixtures. The modeled coefficient of mutual diffusion for a great number of binary mixtures of the above-mentioned individual substances is determined, and the results are compared with the known data. Without special calibration for the experiment, the model correctly predicts the relationship of the self-diffusion and mutual diffusion coefficients (with their variation by several orders of magnitude in the case where the density changes from gaseous to liquid) with both pressure and temperature. For most substances considered in the paper, the maximum deviations of calculations from the experiment do not exceed 30–50%.     

液体非电解质水溶液粘度的预测

在Teju-Rice液体混合物粘度模型的基础上,对常用的液体混合物粘度关联式进行了分析和比较;导出了适用于二元和多元非电解质水溶液的粘度模型;结合实际数据导出的水溶液二元作用参数的估算式可进行水溶液粘度的预测。用该模型计算了7个体系398个不同温度和组成的二元水溶液和4个体系189个不同温度和组成的三元水溶液的粘度,结果表明,计算值对实验数据的总平均相对偏差分别为6.848%和5.043%,本文水溶液粘度估算式的计算准确性优于Teju-Rice法。