Calculation of the Viscosity of Simple Fluids Based on the Rainwater‐Friend Theory

Viscosities of noble gases have been calculated over a wide temperature‐pressure range. Simple and accurate Tang‐Toennies potential of the noble gases are used in the Chapman‐Enskog calculation of the zero density viscosity and in the Rainwater‐Friend theory to determine the initial density dependence of the viscosity. At densities beyond the range of the theory (up to 46 mol.dm^?3), a variant of the residual viscosity is developed. A correlation function for the calculation of viscosity over the whole range of density is presented. A comparison of the calculated and experimental values of the viscosity yields an average absolute deviation of 1.5%.     

传递性质的自由体积模型对方阱流体的应用

对简单分子构成的稀薄气体的传递性质已有较严格的分子动力学理论，但对稠密流体，尤其是液体，严格的理论方法尚难以解决实际问题词．实用中仍以经验或半经验模型为主．半经验模型以Eyring的绝对反应速率理论[1，2]和自由体积理论[3-11]为典型代表．由于自由体积模型可以同时反映温度和压力的影响，其应用潜力更大，值得进一步研究．对理论模型的检验一般用实际物系的测定数据．这种检验虽然直接可靠，但往往受到实验条件的限制，例如高温高压；近年来迅速发展的计算机分子模拟为建立和验证理论模型提供了一个有效手段．由于计算机模拟数…     

Influence of the Excited States of Atomic Nitrogen N(<Superscript>2</Superscript>D) and N(<Superscript>2</Superscript>P) on the Transport Properties of Nitrogen. Part I: Atomic Nitrogen Properties

In this paper, calculated values of the viscosity and thermal conductivity of atomic nitrogen, taking into account three species (the ground and two excited states), are presented. The calculations, which assume that the temperature dependent probability of occupation of the states is given by the Boltzmann factor, are performed for atmospheric-pressure in the temperature range from 1,000 to 20,000 K. Six collision integrals are used in calculating the transport coefficients and we have introduced new averaged collision integrals where the weight associated at each interacting species pair is the probable collision frequency. The influence of the collision integral values and energy transfer between two different species is studied. These results are compared which those of published theoretical studies.     

Influence of the Excited States of Atomic Nitrogen N(<Superscript>2</Superscript>D), N(<Superscript>2</Superscript>P) and N(R) on the Transport Properties of Nitrogen. Part II: Nitrogen Plasma Properties

In this paper, the calculated values of the viscosity and thermal conductivity of nitrogen plasma are presented taking into account five (e, N, N⁺, N₂ and N₂⁺) or eight (e, N(⁴S), N(²P), N(²D), N(R), N⁺, N₂ and N₂⁺) species. The calculations are based on the supposition that the temperature dependent probability of occupation of the states is given by the Boltzmann factor. The domain for which the calculations are performed, is for p = 1 and 10 atm in the temperature range from 5,000 K to 15,000 K. Classical collision integrals are used in calculating the transport coefficients and we have introduced new averaged collision integrals where the weight associated at each interacting species pair is the probable collision frequency. The influence of the collision integral values and energy transfer between two different species is studied. These results are compared which those of published theoretical studies.     

Transport Properties of Monatomic Insulating Liquids and Liquid Alkali Metals from a Cage Model

A cage model is used to calculate the shear viscosity m s and the thermal conductivity s for insulating monatomic liquids and for liquid alkali metals. Three empirical laws: (i) $ eta_s , propto , (1/sqrt T ) $ for liquid alkalis; (ii) s / m s ～ constant for Rb and Cs respectively; (iii) $ ({gamma / {eta _s }})sim sqrt {{{k_B T_m } / M}} $ for liquid alkalis at the melting temperature T m , where n is the surface tension and M the ionic mass, are naturally explained.     

Transport Coefficients of Ag–SiO<Subscript>2</Subscript> Plasmas

Calculated values of viscosity, thermal and electrical conductivities of plasma formed in mixtures of silver (Ag) and silica (SiO₂) are presented. The calculations, which assume local thermodynamic equilibrium, are performed for three pressures (1, 10 and 30 atm) in the temperature range from 4,000 to 30,000 K. All the data for the potential interactions and the necessary formulations to obtain values of transport coefficients are given in details. For atmospheric pressure, five mixtures (100% Ag, 75% Ag and 25% SiO₂, 50% Ag and 50% SiO₂, 25% Ag and 75% SiO₂, 100% SiO₂) in weight percentage are studied. In order to analyse the pressure influence on the transport coefficients, three samples of Ag–SiO₂ mixtures (100% Ag, 50% Ag and 50% SiO₂, 100% SiO₂) in weight percentage are discussed for pressures of 1, 10 and 30 atm. In addition for the test case of oxygen plasma, we compare the computation code results with values obtained by other authors: discrepancies are found and explained.      

Derivation of memory function from its equation of motion

A new form of Memory Function (MF) appearing in the Mori's formalism has been derived using plausible approximations. In addition to the fact that present form of MF satisfies sum-rules upto sixth order, it has special characteristic of presence of one more adjustable parameter. It is also found that the present form of MF behaves as sech ^v (bt) under suitable conditions. The utility of the present MF is exemplified by studying time evolution of velocity auto correlation function and transport coefficients of Lennard–Jones fluids.     

Thermal performance of stable SiO2 nanofluids and regression correlations to estimate their thermophysical properties

The present work investigates the best mix ratio of Glycerol in Water as a medium to prepare a stable nanofluid. Increasing the proportion of glycerol enhances the aqueous mix's dynamic viscosity and improves the prepared nanofluid's stability. The thermal conductivity and viscosity of the Glycerol and Water mixtures determination were undertaken at various Glycerol ratios. The best percentage of glycerol in the mixture is found to have the least amount of thermal conductivity loss and the optimum viscosity gain. Silica (SiO₂) nanofluid of 0.25%, 0.5%, 1%, and 1.5% weight concentrations was prepared with this optimal mixture of Glycerol and Water. The stability of these SiO₂ nanofluids is evaluated by determining the zeta potential at different time intervals. The nanofluids prepared were observed to be stable for one month. The thermal conductivity and viscosity of the nanofluids are measured between the temperature limits of 30°–70°C. A peak increment of 32.1%and 46.3% in thermal conductivity and viscosity is observed. Furthermore, when the percentage enhancement ratio (PER) and Mouromtseff ratio of these nanofluids is examined, it is observed that they have more excellent thermal performance at higher temperatures. Regression correlations are developed to estimate the thermal conductivity and viscosity of the prepared nanofluids with a maximum deviation of 9%.     

The Current‐Potential Characteristics for Simple Surface Electrode Reactions

A treatment based on equations for the Convention II activity coefficients of the components of two‐dimensional solutions in combination with the transition state theory has been developed. As a result, two types of current‐potential characteristics have been derived for quasi‐reversible simple surface electrode reactions. The molecular features of the surface solutions to which each current‐potential relation applies have been established. The current‐potential characteristics obtained in this work coincide with those derived by Laviron using a less straigth and general treatment.     

汽液共存相的粘度及导热系数间的关系

粘度和导热系数是石油、化工等工业过程设计中必需的两种主要传递性质，对它们的实验测定和理论预测或关联研究一直受到人们的广泛关注．对传递性质的研究有以下特点：在理论上，对气体，尤其是稀薄气体有较成功的动力学理论，但对稠密流体，尤其是液体，尚无严格的理论方法，实用中多为经验或半经验的模型；在实验测定方面，对液体的测定相对容易，已积累了大量数据，尤其是液体的粘度和导热系数．另外，在一些工业生产过程中，往往处理呈平衡（饱和）的汽、液两相。质，需要知道各种操作条件下两相工质的传递性质，因此，研究汽（气）、液…     

Rg-HX分子间势的精确从头计算研究

在用非迭代的三重激发项来校正CCSD的CCSD(T)理论水平下,采用aug cc pVQZ基函数对He HF的分子间势进行了系统的研究.结果表明：He HF以线型结构存在.在极限基的情况下,复合物两种线型极小点结构He H F和He F H势阱深分别为46.614 cm－1和25.026 cm－1,对应He原子到HF分子质心的距离Rm分别为0.3149 nm和0.3012 nm.讨论了不同的基函数和理论方法在研究此类弱束缚态复合物的分子间势时的可靠性及其对结果的影响,并研究了HF分子中H－F键长的改变对势能的影响,同时也给出了势函数的解析形式.     

A State-dependent Division Scheme for the Potential of Simple Fluids

Abstract

A new division scheme for the pair potential into long-range and short-range parts is presented, which takes account of the dependence on the density and makes possible the extraction of the bridge function B(r) in the core region. The calculation of the correlation functions is carried out with the hybridized mean spherical approximation (HMSA). As attested by the comparison with the simulation results, HMSA used with this potential separation is suitable to produce accurate bridge function and pair correlation function for the Lennard-Jones fluid.     

Temperature diffusivity and heat conductivity of Langmuir–Blodgett–Kuhn and thin spun-on polymer films

The temperature diffusivity β and heat conductivity κ of thin polymer films were measured at room temperature. Temperature waves were excited at one side of the film and detected at the other side with a pyroelectric foil (PVDF). The dependence of β and κ on chemical and structural parameters have been studied. For the first time, Langmuir–Blodgett–Kuhn multilayer assemblies prepared from “hairy rod” polymers were characterized: μm thin films of stiff polyamides prepared by spincoating exhibit heat conductivities an order of magnitude larger than “classical” polymers.     

静电势能模型对类水滑石结构与性能的理论研究

The electrostatic potential energy model of hydrotalcites was based on the theory of crystallography. The anionic potential energy of MgAl-hydrotalcites, with 20 layers and 2107 anions per layer, was calculated, and the anionic stability of the hydrotalcites was investigated. The charge density of the layer and the distance between the adjacent anions varied with the molar ratio of Al3+/(Mg2+ +Al3+). Anionic potential energy depended on the charge and size of the anions. Calculation results remained consistent with thermal stability and the ion exchange ability reported. This model is able to predict anionic stability of the hydrotalcites.     

A TD‐DFT Study on the Effect of Intermolecular Hydrogen Bonding on the Photophysical Properties of N‐Methyl‐1,8‐naphthalimide

The effect of intermolecular hydrogen bonding on the photophysical properties of N‐methyl‐1,8‐naphthalimide ( 2 ) has been investigated by time‐dependent density functional theory (TD‐DFT) method. The UV and IR spectra of 2 monomer and its hydrogen‐bonded complexes formed with 2,2,2‐trifluoroethanol (TFE) 2 +TFE and 2 +2TFE have been calculated, which confirm the presence of intermolecular hydrogen bonding interactions between the carbonyl groups of the aromatic imide and the hydroxyl group of the polyfluorinated alcohol. The absorption and fluorescence intensities going from 2 monomer via hydrogen‐bonded complex 2 +TFE to 2 +2TFE were found to be gradually enhanced with the wavelength gradually red‐shifted. The enhancements of the fluorescence intensities from 2 monomer to hydrogen‐bonded complexes 2 +TFE and 2 +2TFE were attributed to the decrease of the intersystem crossing (ISC) efficiency from the first excited singlet state S₁ ¹(ππ*) to the second excited triplet state T₂ ³(nπ*), whose energy was increased relative to its ground state due to the intermolecular hydrogen bonding interactions.     

由L-J流体的FMSA状态方程计算流体的PVT性质

运用Tang等提出的Lennard-Jones (L-J)流体两参数的一阶平均球形近似(FMSA)状态方程, 计算了流体的汽液共存相图和饱和蒸汽压曲线, 以及非饱和区的PVT性质, 并与文献数据进行比较. L-J参数由Tr＜0.95的汽液相共存数据回归得到. 计算结果表明, 对于分子较接近球形的流体, 除临界点附近外, 该方程可以在较大的温度和压力范围内计算真实流体的PVT性质, 结果满意. 对于球形分子, 该方程的精确度随分子尺寸的变大基本保持稳定. 该方程不适用于强极性物质. 在高密度区, 该方程的计算结果明显优于P-R方程. 对于分子偏离球形较远的流体, 该方程的适用性变差, 此时要考虑分子形状的影响, 可采用三参数的FMSA状态方程进行计算.     

Scaling of the segmental relaxation times of polymers and its relation to the thermal expansivity

Segmental relaxation times of polymers measured at various temperatures and pressures can be superposed as a function of temperature, using a shift factor equal to the specific volume raised to a power. The material-specific scaling exponent can be linked to the nature of the intermolecular repulsive potential for the material. We show the relationship of this scaling exponent to the thermal expansivity of the material, and how it can be used to sort out the different contributions to the temperature dependence of the local dynamics.     

在确定的热力学状态下测量气体导热系数与黏度

气体的导热系数和黏度是重要的热物性参数,其数值大小取决于所处的热力学状态。在目前的导热系数和黏度主要测量方法中,待测工质在测量时需经历非定常的过程或处于具有物性梯度的非平衡态之下,使得待测工质的物性在时间或者空间上不处于一个确定的热力学状态。本文利用圆柱定程干涉法,通过分析气体导热系数和黏度导致的声波能量耗散,结合气体输运理论中对稀疏气体的描述,探索了在确定的热力学状态下同时测量气体导热系数和黏度的方法,并以氩(Ar)为例进行了实验验证。测量结果与已有文献一致性较好,初步证实了方法的可行性。     

Viscosity Prediction for Oxygen,Nitrogen and Their Mixtures at Zero and Moderately Dense Regimes via Semi‐Empirically Based Assessment

The viscosity coefficients for the gaseous states of N₂ and O₂ and their mixtures are determined at zero and moderately density regimes. The Lennard‐Jones 12–6 (LJ 12–6) potential energy function is used as the initial model potential required y the technique. The interaction potential energies from the inversion procedure reproduce the viscosity commensurate to the best measurements. The initial density dependence of gaseous viscosity coefficient according to the Rainwater‐Friend theory, which was given by Najafi et al., has been considered for pure N₂ and pure O₂.