CF4和惰性气体混合物的输运性质的计算

The present work is concerned with determining the viscosity, diffusion, thermal diffusion factor and thermal conductivity of five equimolar binary gas mixtures including: CF4-He, CF4-Ne, CF4-Ar, CF4-Kr, CF4-Xe from the principle of corresponding states of viscosity by the inversion technique. The Lennard-Jones (12-6) model potential is used as the initial model potential. The calculated interaction potential energies obtained from the inversion procedure is employed to reproduce the viscosities, diffusions, thermal diffusion factors, and thermal conductivities. The accuracies of the calculated viscosity and diffusion coefficients were 1% and 4%, respectively.     

由状态方程计算混合物的临界性质

混合物的临界性质(T_c,P_c和V_c)在高压相态及分离过程计算中具有重要意义.由于实验测定的困难,文献与手册中有关混合物临界性质的数据(与混合物组成有关)极少,如何通过计算确定这些性质成为热力学界所关心的问题之一.混合物的临界性质一般可通过以下三种方法进行估算:(1)通过相包线计算间接确定;(2)由经验或半经验关联式计算;(3)基于严格的临界状态的热力学准则应用状态方程直接计算.第一种方法过于繁琐;而第二种方法普适性较差,且缺乏与汽液平衡计算的热力学一致性;第三种直接计算法可消除上述缺点,因而近年来受到较大重视.Heidemann和Khalil(1980)以及Peng和Robinson(1977)所提出的直接计算法已成功地应用于烃类非极性混合物临界性质的预测.本文的目的主要是将直接法扩充应用至极性混合物临界性质的计算,并改进前人对临界比容的预测.在前阶段工作(徐东海和郭天民,1989)基础上,本文作了较大扩充与修改.按Heidemann和Khalil由Helmholtz自由能导出的下列临界状态判别准则Q△n=0,△n~T△n=1(1)及偏导数矩阵Q中的元素q_(ij)与三次式中三阶偏导数的表达式结合状态方程(可导出逸度f_i表达式)联解方程式(l)和(2)便可求得组成指定的混合物的临界性质.为将直接法扩展应用至极性混合物,作者选用了Leet等(1986)提     

联苯混合物的性质

联苯醚及联苯的低共熔混合物称为联苯混合物,由联苯醚73.5％和联苯26、5％混合而成此时熔点为12℃)我们日常通称为联苯,它已广泛地应用在合成纤维工业中作为一种载热体。     

混合物临界温度的计算

将混合物组成表示为,混合物临界温度由式计算。本文用理想气体热容多项式计算F_i,对208个混合物系共计1523个临界温度进行计算,误差在1.04％以内。     

混合物临界性质的预测

本文基于Heidemann和Khalil的临界状态判别准则,对混合物临界性质进行了预测。为了扩展应用到极性混合物并提高预测质量(尤其是预测临界体积的准确度),本文应用了最近提出的立方型转子链(CCOR)状态方程及局部组成型的CCOR状态方程。按以上二模型及SRK和PR模型对十六组极性和非极性二元及三元混合物计算了临界性质。计算结果表明:CCOR模型应用于极性和非极性体系均能获得良好效果,尤其对临界体积(Vc)的预测,其准碓性较之SRK和PR模型有显著的提高。     

色层热谱法分离氢、一氧化碳、甲烷和惰性气体混合物

氢、一氧化碳、甲烷和惰性气体的分离测定,对石油工业、化学工业、真空电器工业等许多部门都很重要。在应用色层热谱分析法时,氢和一氧化碳将带着甲烷一起放出,因此必须再把含有氢和一氧化碳的部分在ВТИ仪器中作补充分析。现在的测定惰性气体的方法,都不外乎在液态氮的低温下,把多余的成分吸附在活性炭上,用以分出氦和部分的氖。关於用色层分析法分离上述气体的问题,最近已在耶纳克(Janak)的工作中加以论述。他指出了用色层法分析惰性气体混合物、一氧化碳和氢的可能性,但耶纳克所采用的方法是以CO_2作为显谱剂,放出的气体用滴定管测定其容积;这方     

高压下Fe3O4纳米粉的电输运性质

利用高压X射线衍射和高压原位Hall效应方法研究了高压下Fe_3O_4纳米粉的结构和电输运性质的变化。研究结果表明:在17.2 GPa时,Fe_3O_4纳米粉发生了从反尖晶石相到高压相的结构相变。Fe_3O_4纳米粉的电阻率随压力的增加而逐渐减小,但在6.0 GPa处发生了明显的不连续变化,此不连续变化是由压致半金属到金属的相变导致的。金属化相变前,电阻率减小是由于载流子浓度的快速增大。金属化相变后,载流子浓度增长变缓,直到11.0 GPa时趋于饱和。11.0 GPa之后,由于电子-声子的耦合常量随压力增加而减小,散射减小,此时载流子迁移率的增大成为电阻率减小的主要因素。     

液体混合物比热的估算和简捷计算

在化工设计中经常遇到液体混合或溶液的比热计算问题。而液体混合物或溶液的种类繁多,除极少数液体混合物有实测的比热数据外,极大多数情况都采用估算的方法解决。特别对一些新产品的过程开发和中试规模的装置设计中更是如此。其一般方法是根据混合物内各纯物质的比热数据和组成进行计算。对理想溶液的比热可以按各组分的加和性进行计算,而非理想溶液的比热,则用     

用BWR方程计算低温轻烃混合物的热力学性质和油田气系统的相态特性

用有低温校正的BWR状态方程来计算含H_2、N_2、CO_2、Ar等轻烃混合物的气液平衡和诸热力学性质,在100°K以上能够得到满意的结果,并可用于工程设计计算。对于含He和NH_3的轻烃混合物在一定的条件下也能得到较为满意的结果。本文并对某油田气系统的相态特性作了初步探讨。     

液体混合物密度的计算

求取液体密度的经典式为: 式中: ρ、ρ_c——饱和液的密度,临界密度[克/毫升] V、V_c——饱和液克分子比容,临界克分子比容[升/克分子] α、β——(1)式的系数 T_r——对比温度(T_r=T/(T_c))     

稀四氟化碳气体混合物传递性质的确定(英文)

In our previous work, we calculated transport properties of pure gaseous polyatomic carbon tetrafluoride (CF4) and five equimolar binary gas mixtures of CF4 with noble gases through inversion technique. The present work is a continuation of our studies on determining the transport properties of binary gas mixtures CF4 with some gases including three diatomic molecules CO, N2, and O2, a linear polyatomic CO2, and two non-linear polyatomic molecules SF6 and CH4. The Chapman-Enskog and Vesovic-Wakeham methods as well as inversion procedure are used to determine the viscosities, diffusivities, and thermal conductivities, which deviates from the literature values within 1%, 4%, and 5%, respectively.     

由各向同性双势能测定含有CO2的稀二元混合物的传输性质简

The present work is concerned with extracting information about intermolecular potential energies of binary mixtures of CO2 with C2H6, C3H8, n-C4Hlo and iso-C4Hlo, by the usage of the inversion method, and then predicting the dilute gas transport properties of the mixtures. Using the inverted pair potential energies, the Chap- man-Enskog version of the kinetic theory was applied to calculate transport properties, except thermal conductivity of mixtures. The calculation of thermal conductivity through the methods of Schreiber et al. and Uribe et al. was discussed. Calculations were performed over a wide temperature range and equimolar composition. Rather accurate correlations for the viscosity coefficients of the mixtures in the temperature range were reproduced from the pre- sent unlike intermolecular potential energies. Our estimated accuracies for the viscosity are within ±2%. Acceptable agreement between the predicted values of the viscosity and thermal conductivity with the literature values demon- strates the predictive power of the inversion scheme. In the case of thermal conductivity our results are in favor of the preference of Uribe et al.＇s method over Schreiber et al.＇s scheme.     

基于半经验反转理论的二甲醚传递性质计算

采用半经验反转理论获得了二甲醚的通用新势能函数,在此基础上,得到了新势能的碰撞积分和特征参数。利用新的势能参数,根据分子动力学理论与WCUB修正,计算了二甲醚在零密度时的气相黏度、导热系数、热扩散系数以及热扩散因子等传递性质,计算的温度范围为273.15—973.15 K。对二甲醚的气相黏度和导热系数的计算值与实验值进行了对比分析,结果表明计算结果具有较高的精度。黏度、导热系数和热扩散系数计算的精度分别在4%,5%和10%以内,可以满足实际工程的需要,为相关领域的科学研究和实际应用提供了基础数据。     

Effect of Hofmeister Ions on Transport Properties of Aqueous Solutions of Sodium Hyaluronate

Tracer diffusion coefficients obtained from the Taylor dispersion technique at 25.0 °C were measured to study the influence of sodium, ammonium and magnesium salts at 0.01 and 0.1 mol dm⁻³ on the transport behavior of sodium hyaluronate (NaHy, 0.1%). The selection of these salts was based on their position in Hofmeister series, which describe the specific influence of different ions (cations and anions) on some physicochemical properties of a system that can be interpreted as a salting-in or salting-out effect. In our case, in general, an increase in the ionic strength (i.e., concentrations at 0.01 mol dm⁻³) led to a significant decrease in the limiting diffusion coefficient of the NaHy 0.1%, indicating, in those circumstances, the presence of salting-in effects. However, the opposite effect (salting-out) was verified with the increase in concentration of some salts, mainly for NH₄SCN at 0.1 mol dm⁻³. In this particular salt, the cation is weakly hydrated and, consequently, its presence does not favor interactions between NaHy and water molecules, promoting, in those circumstances, less resistance to the movement of NaHy and thus to the increase of its diffusion (19%). These data, complemented by viscosity measurements, permit us to have a better understanding about the effect of these salts on the transport behaviour of NaHy.     

Effects of Thermal Treatment on Gas Transport Through Porous Silica Membranes

Abstract

The effects of thermal treatment from 180°C to 1150°C on the gas transport properties of porous silica membranes were systematically studied for various gases. The permeance of all gases, except for CO₂, has a maximum at 800°C. The CO₂ permeance was constant from 180°C to 600°C and then decreased monotonically. Membranes thermally treated at 1150°C did not exhibit any gas permeation because of pore collapse. The gas transport behavior follows a combination of Knudsen diffusion and surface diffusion for all gases tested except for carbon dioxide. The permeation of carbon dioxide is strongly affected by capillary condensation. We propose a new transport model composed of two components; that is, the Knudsen diffusion factor, α, and the surface diffusion factor, β. A transition was observed for α and β at around 800–900°C, which is close to the strain point of the membrane. This transition treatment temperature can be correlated with the changes in gas permeance. The model allows qualitative evaluation of gas transport through porous membranes regardless of their actual microporous structures.     

Speed of sound of ionic liquids: Database,estimation, and its application for thermal conductivity prediction

Speed of sound is an important thermodynamic property of ionic liquids (ILs) and always chosen as a source to determine other properties. A database for the speed of sound of pure ILs created by collecting experimental data from literature covering the period from 2005 to 2013 is presented. The effects of temperature and the alkyl chain length on the speed of sound are discussed and a second‐order corresponding states group contribution method is developed to estimate the speed of sound. An average absolute deviation (AAD) of 2.34% has been obtained. This method offers a simple but reliable approach to estimate the speed of sound of new ILs. Finally, the speed of sound is used to determine the thermal conductivity of ILs based on the Bridgman theory. The calculated values of thermal conductivity show a good agreement with the experimental ones with an AAD of 3.91%. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1120–1131, 2014     

A new fragment contribution‐corresponding states method for physicochemical properties prediction of ionic liquids

A new fragment contribution‐corresponding states (FC—CS) method based on the group contribution method and the corresponding states principle is developed to predict critical properties of ionic liquids (ILs). There are 46 fragments specially classified for ILs considering the ionic features of ILs, and the corresponding fragment increments are determined using the experimental density data. The accuracy of the developed method is verified indirectly via predicting density and surface tension of ILs. The results show that the FC—CS method is reasonable with an average absolute relative deviation less than 4%. With the calculated critical properties, corresponding states heat capacity (CSHC) and corresponding states thermal conductivity (CSTC) correlations are proposed to predict heat capacity and thermal conductivity of ILs, respectively. The predicted results agreed well with the experimental data. The proposed FC—CS method and the two corresponding states correlations are important for design, simulation, and analysis of new ionic liquid processes. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1348–1359, 2013     

A prediction of the thermodynamic,thermophysical, and mechanical properties of CrTaO4 from first principles

It is reported that the self-forming CrTaO₄ oxide scale can protect refractory high-entropy alloys from oxidation, superior to Cr₂O₃. In this paper, the phase stability, mechanical, and thermal properties of three polymorphous phases of CrTaO₄ are systematically investigated from first-principles density functional theory calculations. The mechanical properties predicted using the strain–energy methods indicated that all three phases are mechanically stable. The temperature dependence of elastic constants and polycrystalline moduli of three phases demonstrated the thermal softening as temperature increase. The Helmholtz-free energies as a function of volume and temperature are derived from phonon dispersions within the quasi-harmonic approximation at six strained volumes. The calculated apparent bulk coefficients of thermal expansion of these three phases are evaluated, the highest value approximately 13.4× 10⁻⁶ K⁻¹ within a temperature range of 500–2000 K for the rutile I4₁md phase. The lattice thermal conductivity calculated by the Debye–Callaway model suggested that the rutile type I4₁md phase has the lowest value of approximately 2.1 W/m/K at 1800 K. The other two phases, C2/m and P2/c, exhibit higher values due to relatively lower Grüneisen parameters and larger phonon velocities. The melting point of CrTaO₄ is predicted to be between 1975 and 2449 K using ab initio molecular dynamics simulations. This work provides a comprehensive theoretical understanding of the thermodynamic, mechanical, and thermal properties for the new material CrTaO₄ and serves as an example of a viable computational design strategy for improved oxidation resistance of refractory alloys at high temperatures.     

立方型状态方程结合Eyring理论在液体混合物黏度计算中的应用

Cubic equations of state (EOS) have been combined with the absolute rate theory of Eyring to calculate viscosities of liquid mixtures. A modified Huron Vidal gE-mixing rule is employed in the calculation and in comparison with the van Laar and the Redlich-Kister-type mixing rule. The EOS method gives an accurate correlation of liquid viscosities with an overall average deviation less than 1% for 67 binary systems including aqueous solutions. It is also successful in extrapolating viscosity data over a certain temperature range using parameters obtained from the isotherm at a given temperature and in predicting viscosities of ternary solutions from binary parameters for either polar or associated systems.