转盘式萃取塔有效扩散系数的预测及其在设计中的应用

A rotating disc column (RDC) with inner diameter 68 mm and 28 compartments is used in this study. Parameters including Sauter mean diameter, hold-up and mass transfer coefficient are measured experimentally under different operating conditions. The correlations in literature for molecular diffusion and enhancement factor equation including eddy diffusion, circulation and oscillation of drops are evaluated. A new equation for the effective diffusion coefficient as a function of Reynolds number is proposed. The calculated values of mass transfer co-efficient and column height from the previous equations and present equation are compared with the experimental data. The results from the present equation are in very good agreement with the experimental results, which may be used in designing RDC columns.     

非牛顿流体中的两并行运动气泡周围流场及气泡间相互作用的PIV研究

The flow fields surrounding two parallel moving bubbles rising from two identical orifices submerged in non-Newtonian fluid of carboxymethylcellulose (CMC) solution of three different mass concentration were measured experimentally by the use of particle image velocimetry (PIV). The influences of gas flowrate, solution mass concentration, orifice interval and the angle between two bubble centers line and vertical direction on the flow field surrounding bubbles were discussed respectively by analyzing the velocity vector, velocity contours as well as individual velocity components. The results show that the liquid velocity both in front of two bubbles and behind increases with gas flowrate duo to shear-thinning effect of previous bubbles, whereas decreases with the increase of CMC concentration due to the increase of drag force acting on bubbles. The effect of the orifice interval on the flow field around two moving bubbles becomes gradually obvious as the interval becomes closer. Moreover, two adjacent side-by-side bubbles repulse each other during rising, leading to the practical interval between them increased somewhat above the orifice interval. When the distance between bubbles is less than the orifice interval l0 mm, the interaction between two neighboring bubbles changed from mutual repellence to attraction with the decrease of the angle of the line of linking two bubble centers to the vertical direction.     

在同心和偏心圆环中有屈服应力的黏塑性流体流动的模型和数值模拟(英文)

Numerical solution of yield viscoplastic fluid flow is hindered by the singularity inherent to the Herschel-Bulkley model.A finite difference method over the boundary-fitted orthogonal coordinate system is util-ized to investigate numerically the fully developed steady flow of non-Newtonian yield viscoplastic fluid through concentric and eccentric annuli.The fluid rheology is described with the Herschel-Bulkley model.The numerical simulation based on a continuous viscoplastic approach to the Herschel-Bulkley model is found in poor accordance with the experimental data on volumetric flow rate of a bentonite suspension.A strict mathematical model for Herschel-Bulkley fluid flow is established and the corresponding numerical procedures are proposed.However,only the case of flow of a Herschel-Bulkley fluid in a concentric annulus is resolved based on the presumed flow structure by using the common optimization technique.Possible flow structures in an eccentric annulus are pre-sumed,and further challenges in numerical simulation of the Herschel-Bulkley fluid flow are suggested.     

空气在二甲基硅油和液压油中扩散系数的测量

A piston-cylinder apparatus was established to measure the solubility and diffusivity of air in dimethyl silicone oils and in hydraulic oils based on the PVT state equation of air and the solution of unsteady one-dimensional diffusion equation. The measured diffusivity-temperature relation can be well fitted by the Arrhenius equation for engineering applications. The correlation between the solute diffusivity D and solvent viscosity  is examined. In terms of Eyring’s activation theory, the activation in the air-silicone-oil diffusion process is quite different from that in the momentum transport of the silicone oil: the activation entropy of the former is positive while that of latter is negative. However, the activation enthalpies of the two processes are in the same order of magnitude, which leads to the observation that D/T is roughly constant.     

非牛顿流体非等温充模过程的Level Set方法模拟(英文)

A non-isothermal injection molding process for a non-Newtonian viscous pseudoplastic fluid is simulated. A conservative interface capturing technique and the flow field solving method are coupled to perform a dynamic simulation. The validity of the numerical method is verified by a benchmark problem. The melt interface evolution versus time is captured and the physical quantities such as temperature, velocity and pressure at each time step are obtained with corresponding analysis. A “frozen skin” layer with the thickness increasing versus time during the injection process is found. The fact that the “frozen skin” layer can be reduced by increasing the injection velocity is numerically verified. The fountain flow phenomenon near the melt interface is also captured. Moreover, comparisons with the non-isothermal Newtonian case show that the curvatures of the interface arcs and the pressure con-tours near the horizontal mid-line of the cavity for the non-Newtonian pseudoplastic case is larger than that for the Newtonian case. The velocity profiles are different at different positions for the non-Newtonian pseudoplastic case, while in the case of Newtonian flow the velocity profiles are parabolic and almost the same at different positions.     

二苯并呋喃在活性炭床层中的吸附动力学

The adsorption of dibenzofuran （DBF） on three commercial granular activated carbons （GAC） was investigated to correlate the adsorption equilibrium and kinetics with the morphological characteristics of activated carbons. Breakthrough experiment was conducted to determine the isotherm and kinetics of dibenzofuran on the activated carbons. All-the experiment runs were performed in a fixed bed with a process temperature of 368 K. The effects of adsorbent morphological properties on the kinetics of the adsorption process were studied. The equilibrium data are found satisfactory fitted to the Langmuir isotherm. An intraparticle diffusion model based on the obtained Langmuir isotherm was＇developed for predicting the fixed bed adsorption of dibenzofuran. The result indicated that this model fit all the breakthrough curves well. The surface diffusion coefficients of dibenzofuran on the activated carbon are calculated, and a relationship with the microporosity is found. As it was expected, the dibenzofuran molecule finds more kinetic restrictions for the diffusion in those carbons with narrower pore diameter.     

非牛顿流体中的气泡行为

非牛顿流体广泛存在于各学科领域（如化工、食品和生物医学等）,也与许多工业过程及人类的生命过程密切相关。非牛顿流体中的气泡行为直接影响流体传质、传热及化学过程的快慢。因此,了解和研究非牛顿流体中的气泡行为具有重要意义。本文分别从气泡生成、聚并和破裂3个方面对非牛顿流体中气泡行为的研究进展进行评述。     

从超音速蒸汽喷嘴到过冷水直接接触冷凝的数值模拟(英文)

The phenomenon of direct-contact condensation,used in steam driven jet injectors,nuclear reactor emergency core cooling systems and direct-contact heat exchangers,was investigated computationally by introducing a thermal equilibrium model for direct-contact condensation of steam in subcooled water.The condensation model presented was a two resistance model which takes care of the heat transfer process on both sides of the interface and uses a variable steam bubble diameter.The injection of supersonic steam jet in subcooled water tank was simulated using the Euler-Euler multiphase flow model of Fluent 6.3 code with the condensation model incorporated. The findings of the computational fluid dynamics(CFD) simulations were compared with the published experimental data and fairly good agreement was observed between the two,thus validating the condensation model.The results of CFD simulations for dimensionless penetration length of steam plume varies from 2.73-7.33,while the condensation heat transfer coefficient varies from 0.75-0.917 MW·(m 2 ·K) -1 for water temperature in the range of 293-343 K.     

氨基酸在非牛顿流体中的扩散

The amino acids are necessarily nutritious components, their diffusions in body fluid and blood that belong to typical non-Newtonian fluid are of virtual importance to control the diffusive process and help clinical treatment. In this article, a holographic interferometer has been adopted to measure the diffusivity of amino acids in non-Newtonian fluid with the use of real-time holographic interference technique. In order to prove the reliability of the experimental instrument, the diffusivities of sucrose aqueous solution at 298.15K were determined. The meas- ured result displays a satisfactory accuracy of the apparatus used. Furthermore, the diffusion coefficients of glynine, L-serine, L-threonine and L-valine in polyacrylamide （PAM） aqueous solution at 298.15K were measured, respec- tively. The experimental data were fitted by a newly proposed correlation equation based on Li＇s predictive model. The calculating results by the present model are at considerably good agreement with experimental values, and the maximum average deviation is only 0.5%.     

全息激光干涉技术测定气体的液相扩散系数

介绍了一种测定液相扩散系数的实时激光全息干涉系统。通过该系统得到清晰表征浓度场分布的实时全息干涉条纹图,利用全息干涉原理及相应的数学关系处理干涉条纹,得到液相扩散系数。利用该方法测定了CO2在乙醇、正丙醇中的扩散系数,结果与文献值非常接近。该方法具有实时、快速、简单和准确等优点,它是一种发展前景很好的液相扩散系数测定方法。     

氨基酸在水溶液中的扩散系数

There are still limited experimental data of liquid diffusion coefficients in literature. Therefore, the experimental investigation and prediction model are of practical and theoretical significance. The diffusion coefficients of L-serine, L-threonine, L-arginine, in aqueous solution at 298. 15 K were measured respectively by holographic interferometer. The affecting factors of molecular structure and polarity were analyzed and discussed. Finally, a modified semi-empirical model for correlating the diffusion coefficients of solid organic compounds in aqueous solutions at 298. 15 K was proposed with an adjustable parameter added. The average deviation between model prediction values and experimental ones is less than 0.2%, which shows a considerably satisfactory accuracy.     

激光全息干涉法测量甘氨酸、L-丙氨酸、L-缬氨酸和异亮氨酸液相扩散系数的研究

The diffusion coefficients of aqueous solutions ofglycine, L-alanine, L-valine and L-isoleucine at 298.15 K were determined by holographic interferometry with accuracy and promptness while without disturbance. The density and viscosity of these solutions were also determined. According to original Gordon model, a model for correlating the diffusion coefficients of amino acids in aqueous solutions was developed and applied. The results showed that this model provided significant convenience in correlation of diffusion coefficients for amino acids system.     

非牛顿流体中组合桨氧传递性能的研究

对两层组合桨在黄原胶水溶液中的混合性能进行了研究,采用能反映微观混合状态的容积传氧系数对多种组合桨进行了比较。结果表明双折叶圆盘涡轮—六叶布鲁马金组合桨有利于获得高的容积传氧系数;加大底层桨直径更有利于非牛顿流体的混合。     

Correlations for liquid-phase mass transfer coefficients in bubble column reactors with newtonian and non-newtonian fluids

The earlier work of Calderbank and Moo-Young (1961) dealing with the liquid-phase mass transfer coefficient in gas-liquid dispersions is examined. Their well-known empirical correlations for small and large bubbles which are free to move under gravity are theoretically derived. The analyses are based on the approach for natural convection mass transfer, and include the case where the fluid is non-Newtonian. The predictions of the models are compared with reported experimental data and correlations.     

液相扩散系数测定方法的近期研究进展

由于液相扩散系数的理论预测和各种估算方法还不够成熟和完善,因此其实验测定的方法尤其受到人们的关注和重视。本文对一些常用的液相扩散系数的测定方法进行了介绍;并着重介绍了一种新型的现代光学测量方法－－激光全息干涉法。     

聚丙烯酰胺压裂液流变行为影响因素研究

通过考察聚丙烯酰胺(PAM)压裂液质量分数,温度,pH及金属离子研究了聚丙烯酰胺压裂液的黏度。结果表明,增加PAM质量分数,压裂液黏度上升,非牛顿性增强,质量分数1.0%PAM压裂液黏度可达到施工要求;温度升高,压裂液黏度下降,非牛顿性减弱;改变PAM压裂液的pH环境也可造成黏度下降;金属离子对PAM黏度影响从大到小顺序依次为Mg2+>Ca2+>Na+>K+,符合扩散电层理论。静态悬砂实验表明,聚丙烯酰胺压裂液在质量分数为1.0%及60℃时,悬砂沉降速度达14.88 min/cm,能满足压裂液携砂标准。     

非牛顿流体搅拌流场的数值模拟研究进展

对非牛顿流体搅拌流场数值模拟过程中的控制方程、旋转桨叶的处理以及数值计算方法三个方面进行了综合论述。阐述了广义牛顿流体模型形式简单、计算量低,在非牛顿流体搅拌流场数值模拟过程中应用广泛;黏弹性流体本构方程具有高度的非线性,采用计算流体力学(CFD)方法对其搅拌流场进行数值模拟难度较高,目前仍处于起步阶段;通过合理简化黏弹性流体本构方程以及采用恰当的数值离散方法,有助于在黏弹性流体的搅拌流场数值模拟中取得进展。