基于PR方程的碳酸二甲酯摩擦理论黏度模型

在对文献中发表的碳酸二甲酯黏度实验数据进行全面收集的基础上,将摩擦理论与工程上常用的Peng-Rob inson状态方程(PR方程)结合建立了碳酸二甲酯的液相黏度模型,通过最小二乘法回归得到了模型中的各系数。结果表明:在拟合范围内,碳酸二甲酯黏度模型的计算值与实验数据绝对平均偏差和最大偏差分别为1.78%和6.34%。所建立的黏度模型适用的温度范围为283—383 K,压力范围为饱和压力接近于100 MPa,文章为碳酸二甲酯作为替代燃料等的进一步深入研究和工程应用提供了黏度计算模型。     

甲醇和乙醇的水溶液粘度、密度和导热系数的估算

根据作者导出的非电解质水溶液的粘度模型,提出了估算低压下甲醇和乙醇水溶液粘度的估算式,并根据对实验数据的回归分析,提出了甲醇和乙醇水溶液的密度和导热系数估算式。利用这些计算式计算了不同温度和组成下的甲醇水溶液和乙醇水溶液的132个粘度数据、130个密度数据和32个导热系数数据,计算值与实验值的平均计算偏差分别为1.888%、0.540%和0.969%;计算了不同温度和组成下的甲醇-乙醇-水三元溶液的115个粘度数据和116个密度数据,计算值与实验值的平均相对偏差分别为2.556%和0.351%。计算结果表明,计算值与实验数据吻合很好。     

Temperature dependence of viscosity of polyurethane polyol solutions: Application of rheological models

Polyurethane polyols were synthesized by reacting the diols with polyisocyanates. Viscosity of their 50% (w/w) solutions in various solvents has been determined at different temperatures by using Haake Roto Visco RV12 Rotational Viscometer. The temperature dependence of viscosity data was solved by Levenberg Marquardt's algorithm by using nonlinear regression models based on WLF, Vogel, and Arrhenius equations. The T_g values obtained from WLF and Vogel equation are comparable to each other and these equations can be satisfactorily used for the analysis of temperature dependence of viscosity data of oligomer solutions. The residuals are random and the absolute average percentage error in analyzing the viscosity data by these equations is minimum. The values of constants in WLF equation are found to be system dependent and adjustable parameters. The predicted In η values obtained from WLF and Vogel equations fit well with the plots of experimental In η values as a function of temperature. © 1996 John Wiley & Sons, Inc.     

Thermal conductivity and viscosity measurements of ethylene glycol-based Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanofluids

The dispersion and stability of nanofluids obtained by dispersing Al₂O₃ nanoparticles in ethylene glycol have been analyzed at several concentrations up to 25% in mass fraction. The thermal conductivity and viscosity were experimentally determined at temperatures ranging from 283.15 K to 323.15 K using an apparatus based on the hot-wire method and a rotational viscometer, respectively. It has been found that both thermal conductivity and viscosity increase with the concentration of nanoparticles, whereas when the temperature increases the viscosity diminishes and the thermal conductivity rises. Measured enhancements on thermal conductivity (up to 19%) compare well with literature values when available. New viscosity experimental data yield values more than twice larger than the base fluid. The influence of particle size on viscosity has been also studied, finding large differences that must be taken into account for any practical application. These experimental results were compared with some theoretical models, as those of Maxwell-Hamilton and Crosser for thermal conductivity and Krieger and Dougherty for viscosity.     

Voltammetry in viscous poly(ethylene glycol) solutions at microelectrodes

Voltammetric currents of the ferrocenyl derivative in highly viscous poly(ethylene glycol) solution (PEG) at microelectrodes were independent of their viscosity, contrary to the prediction from the diffusion-controlled current combined with the Stokes–Einstein equation. The usage of microelectrodes generally prevents deformation of voltammograms by poor conductivity. However, the voltammograms even at the disk electrode 10 μm in diameter and slow scan rates exhibited hysteresis, because the diffusion coefficient in PEG was smaller than in water owing to high viscosity of the solution. The diffusion coefficients evaluated from the peak current through the diffusion equation at microelectrode were of the order of 10⁻⁷ cm² s⁻¹ for the viscosity ranging from 0.1 to 160 Pa s. They are at most by 1000 times larger than the values calculated from the viscosities by the Stokes–Einstein equation. A practical significance of this result is to suggest a possibility of using highly viscous PEG as solid-like solvents without large restriction of mass transport. A possible diffusion model is that the redox species diffuses through lowly viscous local domains, avoiding collision with the backbone of the polymer network.     

Analytic Solution of Diffusion‐Reaction in Spherical Porous Catalyst

The model for coupled diffusion and nt^h‐order reaction in a spherical catalyst pellet, which is a strong nonlinear differential equation with boundary values, is solved using the Adomian decomposition method. The explicit solutions for concentration profiles and effectiveness factors, for the model equation, are obtained and compared with the solutions obtained by a finite difference numerical method. For reaction orders less than 1.0, the Adomian polynomial series solution with 4 terms gives comparable results to those obtained with a finite difference numerical procedure. For reaction orders greater than 1.0, series solutions with more than 6 terms, are required for good accuracy.     

Modelling of microporous diffusion of n-paraffins in zeolite 5A

Sorptive liquid-phase diffusion of two n-paraffins, C₁₀H₂₂ and C₁₁H₂₄, dissolved in isooctane, onto micropore of 5A zeolite was studied to assess multicomponent diffusion and competitive effects. Diffusion coefficients for adsorbing components are determined from experimental batch reactor data. The experimental data indicate that diffusion through the microporous zeolite crystals is the primary diffusional resistance. A mathematical model of the rate of adsorption of a solute from a liquid by micropore adsorbent in a batch system was developed. The equation describing the mass transport by diffusion in a micropore adsorbent has been solved in order to obtain theoretical uptake curves for systems when the adsorption equilibrium isotherm is the favourable and nonlinear one. A computer simulation of the microporous diffusion is performed by use of the ISIM-Interactive Simulation Language. The effect of main term and cross-term coefficients of micropore diffusion for the system considered is investigated.     

风机叶片用环氧树脂体系流变性能研究

本文对风机叶片用环氧树脂体系的流变性能进行了研究,在粘度实验的基础上,依据双阿累尼乌斯方程建立了与实验数据较为吻合的流变模型。结果表明,两种树脂体系的粘度随温度变化情况基本一致,在23～50℃范围内,其粘度都低于300mPa.s,且低粘度保持时间大于30min,符合风机叶片真空成型对树脂低粘度的要求。所建立的粘度模型可有效预测和模拟树脂体系在不同工艺条件下的粘度行为,揭示树脂体系的优化工艺参数和低粘度平台工艺窗口,为合理拟订工艺参数和保证产品质量提供必要的科学依据。     

TANGENTIAL VELOCITY CHANGE WITH TIME OF POLYACRYLAMIDE SOLUTION IN A CONCENTRIC ANNULUS

Tangential velocity change with time of polyacrylamide solution, which had not only viscosity but also elasticity, in a concentric annulus after step motion of the inner cylinder was measured by using a LDV method. By adapting a conception of a second order lag control system which had a feedback connection, an equation for estimating the velocity change with time was presented. Each parameter in the equation was determined based on the experimental results, and the relationships between each parameter and viscosity or elasticity of the solutions was made clear. By using this equation, the tangential velocity change with time of a viscoelastic liquid in the annulus can be estimated when the viscosity and elasticity of the liquid and the rotational speed of the inner cylinder are given. Additionally, it was confirmed that the equation was applicable to the case of polyethyleneoxide solution, which had different ranges of the viscosity and elasticity from those of the test solutions described above.     

N,N-二甲基甲酰胺+醇二元混合物的黏度测定与关联

在288.15~313.15 K和常压下,利用乌氏黏度计测定了N,N-二甲基甲酰胺（DMF）分别与乙醇、丙醇、乙二醇和1,2-丙二醇组成的二元系全浓度范围内的黏度,计算了过量黏度△η和过量流动活化自由能△G^*E。用Redlich-Kister方程对过量黏度进行了关联;用黏度模型如Frenkel方程,Grunberg-Nissan方程,Katti-Chaudhari方程和McAllister方程对实验黏度数据进行了关联和预测,并利用Eyring理论方法计算了流动活化自由能、活化焓和活化熵等热力学函数。结果表明,4个二元系的过量黏度和过量流动活化自由能均为负值,且都随温度降低而偏差增大。过量黏度最低值均发生在DMF摩尔分数约为0.3处。McAllister模型对黏度数据的关联结果最好,预测值与实验值的平均相对偏差最小。比较并分析了DMF与一元醇和二元醇之间分子相互作用的差异。。     

Prediction of fresh concrete flow behavior based on analytical model for mixture proportioning

Large number of experimental techniques and models has been developed recently in an attempt to link the parameters of Bingham equation to concrete composition. On the other hand, concrete mixture proportioning methods based on rheological approach usually do not provide direct input of a measurable rheological parameter(s) into the proportioning expression. In this study, series of concrete mixtures have been proportioned by the use of a theoretical model. The experimental results were compared with the predicted rheological quantity by the model. The evaluation of concrete flow parameters has been performed using a newly developed tube viscometer for concrete. The discussion presents a comparison between the model calculated apparent viscosity and the measured plastic viscosity of fresh mixes as function of volume fraction of solids, normalized with respect to their maximum packing values.     

离子液体[C4mim][PF6]与N, N-二甲基甲酰胺二元混合物在298.15 K～318.15 K的密度和粘度

Viscosities and densities for 1-butyl-3-methylimidazolium hexafluorophosphate （[C4mim][PF6]） and N, N-dimethylformamide （DMF） binary mixtures have been measured at the temperature range from 293.15 K to 318.15 K. It is shown that the viscosities and densities decrease monotonously with temperature and the content of DMF. Various correlation methods including Arrhenius-like equation, Sedclon et al.＇s equation, Redlich-Kister equation with four parameters, and other empirical equations were applied to evaluate these experimental data. A model based on an equation of state Ior estimating the viscosity of mixtures containing ionic liquids were proposed by coupling with the excess Gibbs free energy model of viscosity, which can synchronously calculate the viscosity and the molar volume. The results show that the model gives a deviation of 8.29% for the viscosity, and a deviation of 1.05% for the molar volume when only one temperature-independent adjustable parameter is adopted. The correlation accuracy is further improved when two parameters or one temperature-dependent parameter is used.     

Transient behavior of a zeolite membrane under non-linear conditions

A simplified mathematical model is proposed to provide an analytic solution for the transient behavior of a Langmuirian zeolite membrane subjected to a step increase in sorbate pressure at the upstream surface at time zero. The concentration profiles derived from the simplified model agree with those calculated by numerical solution of the governing partial differential equation. The model is used to investigate the validity of the classical time-delay method of measuring diffusion in the adsorbed phase. Under non-linear conditions the time delay depends on the degree of non-linearity as well as on the diffusional time constant. Under highly non-linear conditions application of the classical linear model yields apparent diffusivity values that are about four times larger than the limiting value (D₀).The new model is used to reanalyze experimental permeation diffusivity data for p-xylene in a single crystal zeolite membrane. The resulting D₀ values are shown to be consistent with the values determined by other experimental techniques.     

The flow of non-Newtonian solutions through packed beds

The rheological behavior of aqueous solutions of Separan AP-30®, polymethylcellulose, and polyvinylpyrrolidone was studied experimentally. These solutions exhibit non-Newtonian flow behavior in simple shear, and are characterized by one of several 2, 3, or 4 parameter rheological equations. The equations used included the power law, the Ellis model, Spriggs equation, the Herschel-Bulkley equation, and Meter's model. The power law model fits the data for each of the solutions over a limited range of shear rates, whereas the other models, which include either a lower shear rate limiting Newtonian viscosity, and/or an upper shear rate limiting Newtonian viscosity, or a yield stress, fit the data well over a wide range of shear rates from 0.00675 to 1076 sec^?1. The pressure drop-flow rate data for the same aqueous solutions flowing through packed beds were correlated well by the Ergun equation using the various rheological models applied in this work to evaluate a modified fluid viscosity. In each case it was found that the rheological model which best fit the viscometric data also gave the best packed bed friction factor correlation, and that no one model, such as the powerlaw, or the Ellis model, is the best one to use in all cases for all solutions. For polyvinylpyrrolidone solutions large deviations between experimental values of friction factor and those from the Ergun equation occurred for modified Reynolds numbers greater than one. A pseudo viscoelastic parameter was used to improve the friction factor correlation empirically at high Reynolds numbers.     

标准氢的黏度方程

在广泛搜集标准氢（25%仲氢）黏度实验数据的基础上,运用单纯形算法拟合了标准氢的黏度计算方程,方程计算值与实验数据的偏差一般在2.0%以内。方程的适用范围为温度100～500 K,压力不超过200 MPa的区域。方程的不确定度为2.0%。方程具有一定的外推性,可以用于标准氢三相点温度到100 K以及500～1000 K,压力不超过500 MPa的区域;100 K以下,除临界区和气相区,方程的不确定度为3.0%,500 K相似文献   

EVALUATION OF THE MOONEY VISCOSITY/CONCENTRATION EQUATION FOR LIQUID-LIQUID EMULSIONS

Mooney's viscosity equation, originally proposed for concentrated solids in liquid suspensions, has been tested for stable liquid in liquid emulsions. Nine different emulsion systems have been considered. In none of the cases considered, Mooney's equation is found to adequately describe the viscosity/concentration behavior. However, the modified form of the Mooney's equation η_r = exp[K₁φ/(1—K₂φ)]& is found to fit the data quite well. The K₁ varies from 2.2 to 5.0 depending on the emulsion system; the K₂ varies from 0.6 to 2.1.     

Nonlinear rheological behavior of a novel oil displacing agent

In this work, the shear and elongational rheologies have been investigated for a newly developed oil displacing agent, polymeric surfactant‐PSf. It was found that the PSf solutions exhibited Newtonian, shear‐thinning, and shear‐thickening behavior, respectively, depending on the polymer concentration and shear rate, and Cox–Merz rule was not applicable to these systems. The first normal stress difference (N₁) versus shear rate plots for PSf were complicated, which varied with the composition of the solutions. The uniaxial elongation in capillary breakup experimental results indicated that Exponential model could be used to fit the experimental data of the PSf solutions at lower polymer concentrations. In addition, it was found that PSf was more effective in improving shear viscosity than partially hydrolyzed polyacrylamide, but not in the case of elongational viscosity. The experimental results indicated that the microstructural mechanisms are responsible for the rheological behavior of the polymers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40813.     

Viscosity-structure relationship of dilute triglycerides’ solutions correlation to retention time in reversed-phase liquid chromatography

The dynamic viscosity (η) of dilute solutions of the trigly-cerides triolein, trilinolein, trimyristin, tristearin and tripalmitin in benzene at temperatures in the range of 25–37°C can be expressed in terms of the viscosity of the solvent (η₀), the triglycerides’ concentration (C) and structural characteristics, such as the length of the carbon chains (CN) and the number of double bonds (DB). The simple empirical equation ln η=k₀+k₁ ln η₀+k₂ CN+k₃ DB+k₄ C satisfactorily describes (within the experimental error of 0.002 cp) the solution viscosity of triglycerides inp-xylene when using the coefficients derived from the benzene solutions. In addition, a relation is derived extending the application of the above-mentioned empirical equation to multicomponent dilute solutions. This last one describes the dilute solution viscosity of natural oils in benzene and agrees with the experimental values. Furthermore, the triglycerides that have equal partition numbers in reversed-phase liquid chromatography (RPLC) exhibit equal values for the solution viscosity. This relationship is similar to the equation expressing the retention time of RPLC in terms of the structure of the solute. Hence, it is suggested that the shape of the solute, which is a significant factor for the solution viscosity of triglycerides, also plays an important role in the retention mechanism of RPLC.     

用改进的Tait方程关联烷烃、芳香烃和乙醇在高压下的黏度

A new model was proposed to calculate the viscosity of fluids under the pressure ranging from 0.1 to 110MPa by improving the Tait equation, in which the viscosity μ of liquids was linked with activation volume V. The model with two adjustable parameters a and fl was applied in calculating viscosities for alkane, aromatic and alcohol family at high pressure. Results show that calculated values of viscosity are in good agreement with the experimental ones, and the average relative deviations for alkanes, aromatics and alcohols are 0.56%, 0.31% and 0.66%, respectively. Besides, the errors correlated by the model proposed in this paper were equivalent to the ones from the pure empirical Tait equation, and obviously superior to those from Eyring equation.     

ON THE RHEOLOGICAL BEHAVIOUR OF FILLED POLYMER MELTS†

The viscosity of polymer melts increases when adding fillers. Experiments were conducted with styrene—acrylonitrile copolymers filled with various amounts of glass beads and short glass fibres on a rotational and a capillary rheometer. Further from literature some representative equations have been compiled describing the influence of fillers on the viscosity. Applied to the experimental results it was found that the relative viscosity (R, i.e. the ratio of the viscosities of the filled and unfilled melts, shows a pronounced dependence on the shear rate ? but not on the shear stress t.