Generalized corresponding states correlation for self-diffusion coefficients of fluids

The simple principle of corresponding states may be generalized to include substances that depart from strict conformality by introducing state dependent shape factors. This approach is applied to self-diffusion coefficient using a modified Enskog dense gas theory. Results are obtained for both saturated liquids and supercritical fluids and are generally within experimental error.     

Corresponding states correlation of saturated and metastable properties

A corresponding states correlation is developed for the p - v - T properties of saturated liquids. It is similar in form to a previous correlation; however it is more accurate in the low pressure, low Pitzer factor range, owing to the incorporation of new information about low Pitzer factor behavior. The problem of creating corresponding states correlations of the spinodal lines and the metastable states is also discussed in the light of new equation of state information. A partial preliminary correlation works particularly well for non-polar molecules in the range of fairly small positive Pitzer factors.     

A corresponding states model for the thermal conductivity of gases and liquids

A new model for the prediction of the thermal conductivity of pure fluids and mixtures is presented. The model is based on the corresponding states theory, and to use the model only well-known, pure component parameters plus the transport properties of a reference substance (here methane) are required. No P—V—T information is needed. The model is applied to the lower hydrocarbons (up to pentane), nitrogen, carbon dioxide, and mixtures of these at reduced temperatures between 0.6 and 3.0 and reduced densities between 0.0 and 2.7. For over 600 data points, the deviation between experimental and predicted values is typically between 2 and 5%.     

A correlation for thermal conductivity of liquid n-alkanes based on the Vogel-Tammann-Fulcher-Hesse equation

This paper demonstrates that thermal conductivity of liquid paraffin hydrocarbons of different molecular weights can be correlated properly and conveniently using the Vogel-Tammann-Fulcher-Hesse equation. This approach is advantageous for applications of practical importance because it leads to a simpler effective correlation with fewer empirically determined parameters while providing twice better accuracy than a previous empirical correlation utilizing cubic-polynomial equations. This is illustrated by analyzing and correlating the thermal conductivity data of several liquid n-alkanes.     

A simple correlation to predict thermal conductivity of supercritical carbon dioxide

Nowadays due to wide usages of supercritical fluids (SCFs) technology in different industrial fields, thermal conductivity estimation of carbon dioxide is so significant. In this study, a new correlation for the prediction of supercritical carbon dioxide (SC-CO₂) thermal conductivity based 600 data points from the literature is proposed. The simple correlation is function of density and temperature. The proposed SC-CO₂ thermal conductivity correlation has better performance (lower AARE%) and higher thermal conductivity prediction ability at wider range of temperature from 290 to 800 K and density between 1 and 1200 kg/m³ respect to Jarrahian et al. and Bahadori et al. thermal conductivity models.     

Corresponding states relationship for electrical resistivity of glassy polymers

Using the glass transition as a corresponding state for polymers, a relationship has been found between reduced electrical resistivity and reduced temperature for a large number of polymers in the glassy state. As a consequence of this relationship and the Arrhenius temperature dependence of the unreduced data, the activation energy for electrical conduction is shown to be directly proportional to the glass transition temperature and linearly related to the activation energy for the glass transition. A molecular model is proposed to explain these results in terms of the number of polymer segments involved in electrical conduction (～10) and the activation energy per segment (～4 kcal/mol).     

A generalized corresponding states method for the prediction of the thermal conductivity of liquids and liquid mixtures

We have recently developed an extension of the three parameter corresponding states principle based on the properties of two non-spherical reference fluids for the viscosity of liquids and liquid mixtures. We extend the method here to the thermal conductivity. We have tested the method for a large number of binary liquid mixtures using the two pure components in each case as our reference fluids. Good agreement between predicted and experimental thermal conductivities was obtained using only the data for the pure components. This agreement becomes excellent if a single binary interaction consta independent of temperature and composition, is used in the mixture calculations. If the pure component reference properties are not available, then the may he obtained from the properties of two similar fluids.     

Enzymatic synthesis of oleyl oleate in dense fluids

Esterification between oleic acid and oleyl alcohol, catalyzed by theMucor miehei immobilized lipase in a batch-stirred tank reactor with supercritical carbon dioxide as solvent produced higher reaction rates at supercritical conditions than in the solvent-free system. A continuous fixed-bed reactor was designed based on the results obtained from batch experiments. At 150 bar, 40°C, and with water activity 0.46% w/w, the activity of the enzyme preparation is practically unchanged when CO₂ was used as solvent. The addition of small amounts of water increases the conversion rate. The higher conversion also was observed at longer residence time. Whenn-butane was used as reaction medium, a decrease in conversion was observed.     

含油气盆地中热传导与岩石热导率研究

含油气盆地中热传导是最主要的热量传递方式,在大地热流一定的情况下制约热传导的主要因素是热导率的大小。前人对岩石热导率与温度、压力、岩石孔隙度的关系以及岩石热导率的各向异性进行了研究。本文对前人的研究成果进行了综合分析,认为下一步应该加强沉积岩平行层面方向和垂直层面方向热导率差异的研究及热导率与岩石输导性能关系的研究。     

Calorimetric thermal conductivity measurement for high-temperature materials

A K1952 instrument has been upgraded to determine the thermal conductivities of materials by the GOST 12170 stationary method. The application of that method has been extended to the determination of thermal conductivity for industrial forms of refractory materials and for research in material science, design, and thermal insulation calculation. The K1952 system has been used in testing standard specimens. It has been confirmed that the parameter measurements conform to the technical documentation for standard specimens. A certificate has been obtained to confirm the type of means of measurement RU. E.32.001.A No. 30197, which was issued by the Federal agency on technical regulation and metrology. Translated from Novye Ogneupory, No. 2, pp. 47 – 49, February, 2009.     

有机物混合液导热系数的预测

文章根据液体物质的导热系数与密度的关系,导出了估算有机物混合液导热系数的计算模型。利用该模型计算了53个体系369个数据点的二元有机物混合液导热系数,计算值与实验值的总平均相对偏差为1.434%,计算值与实验数据吻合较好,计算准确性优于文献方法;文章方法简单方便,只需要混合液各组分的临界温度、临界体积和导热系数数据,就可以直接预测各种温度和组成的有机物混合液的导热系数。     

激光导热仪在橡胶导热性能研究中的应用

简要介绍了激光导热仪的测试原理以及测试工作的注意事项等,详细介绍了如何使用激光导热仪测试炭黑／橡胶复合材料的导热性能,并对测试结果作了恰当的分析。     

Electrokinetic mixing of two fluids with equivalent conductivity

Electrokinetic (EK) micromixers have been widely studied in the past decade for biochemical applications, biological and chemical analysis, etc. Unfortunately, almost all EK mixers require different electrical conductivity between the two fluids to be mixed, which has greatly limited their wide applications, in cases where the two streams to be mixed have equivalent electrical conductivity. Here we show that mixing enhancement between two fluids with identical conductivity can be achieved in an EK micromixer with conductive sidewalls, where the electric field is in transverse direction of the flow. The results revealed that the mixing became stronger with increased conductivity value. This mixing method provides a novel and convenient strategy for mixing two liquids with the same or similar electrical conductivity in microfluidic systems, and could potentially serves as a powerful tool for sample preparation in applications such as liquid biopsy, and environmental monitoring, etc.     

用激光导热仪测定炭黑填充橡胶的导热系数

用激光导热仪测定了5种填充不同量炭黑N 220的胶料在30～140℃时的导热系数,分析了导热系数随温度和炭黑填充量变化的关系,发现胶料的导热系数均随着温度的升高呈线性增大趋势,随炭黑填充量的增加也逐渐增大.将导热系数与温度和炭黑填充量进行了关联,得到了线性回归方程式,进而确立了适合于计算不同温度和不同炭黑N 220填充量胶料导热系数的关联方程A=0.133 77 2.008 74×10-4t 0.001 64 X.将用该方程计算的结果与实验值进行比较,60个数据点的平均相对误差仪为0.93%.     

High-Temperature tests of heat-insulating refractory materials for thermal conductivity

Specialists of D. I. Mendeleev Russian University of Chemical Engineering have created an installation for determining the thermal conductivity of heat-insulating refractory materials in the range of 20–1000°C using a measuring cross. The data obtained for materials tested by the steady-flow method and the hot-wire method (ISO 8894-1:1987 (E)) differ by no more than 12%.     

二氧化硅气凝胶的气相热导率模型分析

气凝胶是一种超级隔热材料,具有极低的整体热导率。气凝胶的纳米多孔网络结构极大限制了气体分子热运动,使得气凝胶中的气相热导率低于自由气体的气相热导率。本文介绍并讨论了气凝胶气相热导率的基本理论和模型,考察了孔径尺度和气凝胶固相骨架对气相热导率的影响。结果表明,气凝胶气相热导率随气压和孔径的减小而迅速降低,随气凝胶密度的增大而降低。当压力极低时,气凝胶的气相热导率远低于常压下大空间的静止空气。气凝胶纳米固体网格对气相热导率存在重要影响,在(0.01～100)×10⁵ Pa的压力范围内影响尤其显著。     

Toward nanofluids of ultra-high thermal conductivity

The assessment of proposed origins for thermal conductivity enhancement in nanofluids signifies the importance of particle morphology and coupled transport in determining nanofluid heat conduction and thermal conductivity. The success of developing nanofluids of superior conductivity depends thus very much on our understanding and manipulation of the morphology and the coupled transport. Nanofluids with conductivity of upper Hashin-Shtrikman (H-S) bound can be obtained by manipulating particles into an interconnected configuration that disperses the base fluid and thus significantly enhancing the particle-fluid interfacial energy transport. Nanofluids with conductivity higher than the upper H-S bound could also be developed by manipulating the coupled transport among various transport processes, and thus the nature of heat conduction in nanofluids. While the direct contributions of ordered liquid layer and particle Brownian motion to the nanofluid conductivity are negligible, their indirect effects can be significant via their influence on the particle morphology and/or the coupled transport.     

The thermal conductivity of oils sands

Measurements have been made of the effective thermal conductivity of some samples of Athabasca oil sands using a steady state method over the temperature range 20°C – 120°C. The bitumen content of the samples was altered from its natural value by mixing with additional sand and the resulting values of the thermal conductivity were found to increase with increasing the oil content. Moreover, the effective thermal conductivity values were found to decrease with increasing temperature.