Prediction of Fluid Mixture Transport Properties by Molecular Dynamics

Equilibrium molecular dynamics simulations of mixtures of n-decane with methane, ethane, and carbon dioxide and of the mixture carbon dioxide–ethane were performed using the anisotropic united atoms model for n-decane and one-and two-center Lennard–Jones models for the light components. The Green–Kubo relations were used to calculate the viscosity, thermal conductivity, and inter- and intradiffusion. Viscosities are predicted with a maximum deviation of 30% at low gas concentrations and less than 10% deviation at high gas concentrations. The viscosity and thermal conductivity are less sensitive to the cross interactions than the diffusion coefficients, which exhibit deviations between models and with experiments of up to 60%.     

液态Pb-Cu合金结构与扩散性质的分子动力学模拟

通过分子动力学方法模拟液态Pb-Cu合金的熔体结构,得到液态合金的对相关函数曲线、配位数和相关半径,并用于分析合金熔体内部的结构。同时将NRTL方程与分子动力学方法结合,提出一种计算合金互扩散系数的新方法,使用该方法计算得到了Pb-Cu合金的自扩散与互扩散系数,并分析了熔体结构对合金扩散性质的影响。     

饱和液态制冷剂氨的热物理性质的分子动力学模拟

运用分子动力学方法模拟了制冷剂氨的饱和液态热物理性质。采用典型的site-site势能模型模拟了制冷剂氨的饱和液态密度和比焓,将模拟结果与美国国家标准研究所(NIST)数据库的值进行了对比,最大相对偏差分别在1.5%(密度)以内和3.2%(比焓)以内。对比结果表明:采用合理的势能模型和参数,运用该模拟方法预测单一组分工质的热物理性质是可行的。     

Transport Properties of Undercooled Liquid Copper: A Molecular Dynamics Study

By using the embedded-atom method (EAM), a series of molecular dynamics (MD) simulations are carried out to calculate the viscosity and self-diffusion coefficient of liquid copper from the normal to the undercooled states. The simulated results are in reasonable agreement with the experimental values available above the melting temperature that is also predicted from a solid–liquid–solid sandwich structure. The relationship between the viscosity and the self-diffusion coefficient is evaluated. It is found that the Stokes–Einstein and Sutherland–Einstein relations qualitatively describe this relationship within the simulation temperature range. However, the predicted constant from MD simulation is close to 1/(3π), which is larger than the constants of the Stokes–Einstein and Sutherland–Einstein relations.     

Thermodynamic and Transport Properties of Binary Mixtures Containing 1,3-Dioxolane

This paper reports density and viscosity measurements for the binary mixtures of cyclopentane or cyclohexane or benzene with 1,3-dioxolane at 283.15, 298.15, and 313.15 K. From the experimental data, excess volumes and excess viscosities were calculated and the results were fitted to a Redlich–Kister-type equation. The results are discussed in terms of molecular interactions. The Prigogine–Flory–Patterson and Blomfield–Dewan theories were used to analyze the results at 298.15 K.     

Liquid Viscosity of Binary Mixtures of Methanol with Ethanol and 1-Propanol from 273.15 to 333.15 K

The liquid viscosities and densities of two binary mixtures of methanol with ethanol and 1-propanol were measured in the temperature range from 273.15 to 333.15 K with a capillary viscometer and a glass pycnometer, respectively. The uncertainties in the measured viscosities were estimated to be smaller than 1.3%. The experimental viscosity values could be fitted to the Mertsch and Wolf equation within 2%.     

Thermodynamic and Transport Properties of Liquid HFC-227ea

The thermal conductivity and heat capacity of liquid 1,1,1,2,3,3,3-hepta-fluoropropane (HFC-227ea) have been studied by a high-frequency thermal-wave method over the temperature range of 294 to 345 K at pressures up to 2.8 MPa. The purity of the samples used throughout the measurements is 99.99 mol%. The experimental uncertainties of the thermal conductivity and heat capacity measurements were estimated to be within ±1.5 and ±2%, respectively. The thermal conductivity of HFC-227ea in the liquid phase decreases as temperature increases, while the pressure has an opposite effect.     

热致性液晶聚芳酯的相对分子质量控制与性能

用对苯二甲酸(TPA)作为相对分子质量调节剂,将6-乙酰氧基-2-萘甲酸和对乙酰氧基苯甲酸通过熔融酯交换和固相缩聚两步法,合成了数均相对分子质量约为5619~12264的热致液晶聚芳酯(PAT)。采用傅里叶变换红外光谱、核磁共振波谱仪、偏光显微镜、热失重分析和差示扫描量热分析等手段对单体和聚合物进行了结构与性能表征。结果表明,所制备的聚合物结构与实验设计相符,其热稳定性随着聚合物相对分子质量的增加而提高,在高温下保持向列型液晶相,因此在高温下可以与其他聚合物复合加工。当聚合物发生固相缩聚以后,聚合物的相对分子质量变大,结晶性能变好,热稳定性也明显提高。     

Prediction of Thermodynamic Properties of Liquid Air

In this work, a simple equation of state (EoS) has been used to predict some thermodynamic properties of air as a pseudo-pure fluid; as a ternary mixture of nitrogen, oxygen, and argon; and as a binary mixture of nitrogen and oxygen at different temperatures and pressures. A comparison with literature tabulated values has been made. The agreement of calculated densities with corresponding tabulated values is good for which the average absolute deviations are better than 0.06% if we assume air as a pseudo-pure fluid, and 0.9% and 1.2% if we consider air as a ternary mixture and as a binary mixture, respectively. To show the ability of this equation of state to predict density, the calculated densities of air have been compared with those computed by other methods.     

Diverging Thermodynamic Derivatives Associated with Heterogeneous Chemical Equilibrium in a Binary Liquid Mixture with a Consolute Point

The solubilities of tin(II) oxide, copper(II) oxide, and cobalt(II) oxide have been determined in the liquid mixture, isobutyric acid + water, along the critical isopleth. When plotted in van’t Hoff form with \(\ln s\) versus \(1/T\) , the solubility measurements, \(s\) , lie on a straight line for values of the temperature, \(T\) , which are sufficiently in excess of the critical solution temperature, \(T_\mathrm{c}.\) In the case of SnO, the dissolution reaction is exothermic, and the slope of the van’t Hoff plot diverges toward positive infinity as \(T\rightarrow T_\mathrm{c} .\) In the case of both CuO and CoO, the dissolution reaction is endothermic, and the slope of the van’t Hoff plot diverges toward negative infinity as \(T\rightarrow T_\mathrm{c} .\) Analysis of these ternary, heterogeneous equilibria using finite dimensional vector space stoichiometry theory shows that each contains two linearly independent components. According to the Gibbs phase rule, two-phase equilibria of this type can be described by two fixed, intensive variables, which are accounted for by the temperature and the pressure, respectively. The Gibbs–Helmholtz equation and the principle of critical-point universality can be combined to predict under conditions of fixed temperature and pressure that when dissolution is exothermic, \((\partial \ln s/\partial (1/T))\) should diverge toward positive infinity in the critical region, while when dissolution is endothermic, \((\partial \ln s/\partial (1/T))\) should diverge toward negative infinity. Our experiments include examples confirming both these predictions.     

The Calculation of Thermodynamic Properties of Ga-Sb Binary Liquid Alloys

In this paper, the activities of componentsof Ga-Sb system have been calculated from itsphase diagram by using computer program CABPD(calculating activities from binary phasediagrams) presented by us in previous paper.The excess free energy of liquid solution canbe expressed as:ΔG_m=X_(Ga)X_(Sb)(4392+17022X_(Sb)-15138X_(Sb)) J/mol In order to verify the reliability ofcalculated results, a discriminant has beenproposed.     

Braiding Simulation and Prediction of Mechanical Properties

Rotary braiding is a cost effective method to manufacture near net shaped preforms that generally have a closed section and may have an arbitrary shape if braiding is performed over a shaped mandrel. The reinforcement architecture can be varied by the number and spacing of active bobbins, and by the speeds used to ‘take-up’ the braid and move the circumferential bobbins. Analytical methods are available that can reliably predict yarn paths and the final braid meso-structure for simple regular sections, and further analytical methods have been proposed to estimate composite braid elastic mechanical properties. A full simulation chain using the explicit Finite Element (FE) technique is presented for composite braid manufacture and mechanical stiffness prediction of the final composite. First simulation of the braiding process provides detailed information on yarns paths and braid meso-structure, from which Representative Volume Elements (RVE) of the braid may be constructed for analysis of stiffness properties. The techniques are general and can be applied to any braid geometry. A specific problem of meshing the yarn structure and interspersed resin volumes is overcome using conventional solid elements for the yarns and Smooth Particle Hydrodynamics for the resin, with link element to join the two constituents. Details of the background theory, braid simulation methods, meso- model analysis and validation again analytical and test measurements are presented.     

混合工质热力参数特性与脉动热管适应性研究

以PR状态方程、逸度系数方程、混合法则、相平衡方程组为基础,求解出混合工质特定压力下的泡点温度和露点温度,从而绘制出二元混合工质在特定压力下的气液相平衡图。分析了二元混合工质的露点温度或泡点温度与工质的种类、配比、压力之间的关系。以选取适合脉动热管传热特性的二元混合工质热力参数为例,得到选取混合工质的相应方法及注意事项。     

Prediction of Kinematic Viscosities for Binary and Ternary Liquid Mixtures with an ASOG-VISCO Group Contribution Method

The kinematic viscosities for 273 binary and 11 ternary systems were predicted with a new model (ASOG-VISCO) developed by combining the ASOG group contribution method and Eyrings theory of absolute reaction rates. The ASOG-VISCO group pair parameters were determined from literature kinematic viscosity data for group pairs of CH₂, ArCH, CyCH, OH, H₂O, CO, COO, CCl₃, and CCl₄ in the temperature range of 283.15 to 333.15 K. The overall average deviations between experimental and predicted kinematic viscosities for the binary and ternary systems were 4.15 and 5.03%, respectively. The predicted results using ASOG-VISCO were better than those determined with the UNIFAC-VISCO group contribution method.Paper presented at the Sixteenth European Conference on Thermophysical Properties, September 1–4, 2002, London, United Kingdom.     

液态金属电子输运性质的理论研究

液体的许多重要物理性质及结构稳定性都直接或间接与价电子状态有关,电子输运性质的研究因较直接揭示液体中价电子的变化而倍受重视。主要介绍液态金属电阻率和电势的理论研究现状,分析了获得其中关键参数熔体结构因子及原子间作用势的途径。     

二元有机物体系相变的分子动力学模拟

采用分子动力学模拟(MD)和NTP系综方法对十七烷、十五烷及十七烷/十五烷混合体系的相变行为进行了模拟研究.根据体系自扩散系数和比体积随温度的突变关系,获得的十七烷、十五烷相变温度值与文献中的实验结果吻合较好,并确定了不同混合体系的相变温度.二元混合体系的相变温度可根据组分比例进行调节,可满足一定温度下相变储能的应用要求.通过分析熔化过程中十七烷分子二面角的变化获得了十七烷分子微观结构变化的特征.在熔化过程中十七烷分子有序度降低.     

Sound Propagation and Transport Properties of Liquid 3He in Aerogel

Superfluid ³ He confined in aerogel offers a unique chance to study the effects of a short mean free path on the properties of a well defined superfluid Fermi liquid with anisotropic pairing. Transport coefficients and collective excitations, e.g. longitudinal sound, are expected to react sensitively to a short mean free path and to offer the possibility for testing recently developed models for quasiparticle scattering at aerogel strands. Sound experiments, together with a theoretical analysis based on Fermi liquid theory for systems with short mean free paths, should give valuable insights into the interaction between superfluid ³ He and aerogel.     

Transport Properties and Viscosity of Liquid CdTe Doped with In, Ge, and Sn

Data are presented on the high-temperature electrical conductivity, thermoelectric power (up to 1825 K), and viscosity (up to 1400 K) of undoped and doped (In, Ge, and Sn) CdTe melts. All of the materials were found to retain semiconducting properties upon melting, with a gradual increase in the contribution of metallic bonding, especially pronounced for the CdTe + 2 mol % Sn melt. The results are interpreted in terms of the double-structured melt model, which considers the coexistence of densely packed metallic regions and crystal-like CdTe clusters. The transition to metallic behavior of conductivity is accounted for by a gradual increase in the volume fraction of the densely packed, metallic phase. The doping effects on the conductivity and thermoelectric power of liquid CdTe are interpreted in terms of s–p hybridization.     

DIPPR Project 882: Transport Properties and Related Thermodynamic Data for Binary Mixtures

DIPPR Project 882 was organized to develop a computerized databank of selected and evaluated physical, thermodynamic, and transport properties for mixtures of primarily organic compounds. The properties include: liquid viscosities, liquid thermal conductivities, mutual diffusion coefficients, excess volumes and densities, surface tensions, critical temperatures, critical pressures and densities, and solubilities of sparingly soluble organic compounds. The collection is not complete. It is estimated that the complete collection covers about 90% of the mixture classes, contains about 85% of the binary systems published, references about 80% of the data sources, and is a repository for about 85% of all the data published (these estimates exclude density and solubility where the coverage was not intended to be comprehensive). Exhaustive literature searches were made. The data from the original literature were assessed and differences from the pure component values derived from the DIPPR Project 801 and other reliable evaluated data sources for pure compounds were noted. In cases where the differences were excessive, the data sets were rejected. The total collection consists of about 2140 mixture/property pairs covering 361 mixture classes. The results of the project are distributed as five books in the series Transport Properties and Related Thermodynamic Data of Binary Mixtures published by the American Institute of Chemical Engineers and in electronic form as the DIPMIX Database on Transport Properties and Related Thermodynamic Data for Binary Mixtures distributed by the Thermodynamics Research Center.