纳米流体热导率的测量

运用瞬态热线法测定了不同种类、不同体积份额配比的纳米流体的热导率,分析了纳米粒子属性、份额、尺度等因素对纳米流体热导率的影响.实验结果表明,在液体中添加纳米粒子显著增加了液体的热导率.通过对实验结果进行分析,提出了计算纳米流体热导率的关联式.     

液体热导率测量方法的研究进展

液体热导率的测量方法进展，介绍一种可测量液体和含氢油品的热导率的测量装置。     

流体热导率测量方法的研究进展

液体热导率的测量方法进展，介绍一种可测量液体和含氢油品的热导率的测量装置 。     

液体结构与热导率模型

为了深入探讨液体结构对热导率的影响,假设液体由微型晶粒和空穴组成,在有效结构理论基础上用晶体学和气体分子运动论的方法推导出一个双参数热导率模型：λ=D T^4/7Vs^2/(V-Vs)^2/7V C V-Vs/V√T/M/Vc^2/3Ωg,该模型能够较好地适用于不同液体物质热导率的关联。由关联数据定性讨论了特征参数D和C的物理意义,解释了特征参数D和物质晶胞参数间的良好定量关系。结果表明模型参数的数值和符号较好地表达了液体的结构特点和导热机理,进一步说明了该热导率模型的合理性。     

咪唑型离子液体热物理性质测量

利用自行搭建的热线法液体热导率和热扩散系数装置测试了两种咪唑型离子液体([C₆mIm][BF₄]和[C₄mIm][BF₄])在不同温度下的热导率和热扩散系数。根据文献报道的密度数据获得了样品的比热容。结果表明:两种离子液体的热导率与温度的相关性不大;两种阳离子结构相似的离子液体热扩散率相近, 热扩散率随温度的升高有明显的变化, 本文认为离子液体内部的离子动量分布与温度紧密相关, 离子间的动量交换随温度的升高而增加, 离子动量分布随温度升高逐渐趋于一致, 离子间碰撞产生的动量交换不再明显改变离子的动量, 导致热扩散率的变化随温度升高而减小。     

掺镁碳酸熔盐液体导热特性

为克服碳酸熔盐热导率较低的不足,提出通过向三元碳酸熔盐(Li2CO3-Na2CO3-K2CO3)掺杂金属镁粉来改善导热性能的新思路,采用静态熔融法制备了掺杂1%、2%掺镁碳酸熔盐复合材料。采用扫描电镜-X射线能谱、阿基米德法、差示扫描量热法(DIN比热测试标准)和激光闪光法,分别观察了掺镁碳酸熔盐形貌结构,测量了熔盐和复合熔盐液体的密度、比热容、热扩散系数,最后计算获得复合熔盐液体的热导率。研究结果表明,镁粉的加入改变了纯盐(三元碳酸熔盐)的形貌结构,熔体内形成大量的2~5μm球体颗粒,与纯盐相比,1%掺镁碳酸熔盐液体密度、热扩散系数和热导率都得到增强,液体比热容减小,复合熔盐液体的平均热导率增加了21.67%;2%掺镁碳酸熔盐液体密度、热扩散系数和热导率同样得到增强,虽然复合熔盐液体的比热容减小,但其平均热导率仍然增加了19.07%。1%掺镁碳酸熔盐具有更高的液体密度、热扩散系数和热导率,可作为传热介质在太阳能热发电传蓄热系统推广。     

掺镁碳酸熔盐液体导热特性

为克服碳酸熔盐热导率较低的不足,提出通过向三元碳酸熔盐（Li₂CO₃-Na₂CO₃-K₂CO₃）掺杂金属镁粉来改善导热性能的新思路,采用静态熔融法制备了掺杂1%、2%掺镁碳酸熔盐复合材料。采用扫描电镜-X射线能谱、阿基米德法、差示扫描量热法（DIN比热测试标准）和激光闪光法,分别观察了掺镁碳酸熔盐形貌结构,测量了熔盐和复合熔盐液体的密度、比热容、热扩散系数,最后计算获得复合熔盐液体的热导率。研究结果表明,镁粉的加入改变了纯盐（三元碳酸熔盐）的形貌结构,熔体内形成大量的2~5 μm球体颗粒,与纯盐相比,1%掺镁碳酸熔盐液体密度、热扩散系数和热导率都得到增强,液体比热容减小,复合熔盐液体的平均热导率增加了21.67%;2%掺镁碳酸熔盐液体密度、热扩散系数和热导率同样得到增强,虽然复合熔盐液体的比热容减小,但其平均热导率仍然增加了19.07%。1%掺镁碳酸熔盐具有更高的液体密度、热扩散系数和热导率,可作为传热介质在太阳能热发电传蓄热系统推广。     

羧酸酯分子结构有限元分析及液体热导率估算

在化工生产中热导率是基本的热力学数据。羧酸酯类有机物是重要的化工原料,但对其热导率的估算研究较少。作者在有限元分析方法基础上,用振动力学方法求解羧酸酯分子结构固有频率,用势能最小原理求解各节点的位移矢量,用量化计算方法中的重原子集居电荷计算羧酸酯分子结构的电荷-位移参量,建立了羧酸酯类有机物液体热导率的估算模型。结果表明,用羧酸酯分子结构固有频率、电荷-位移、温度等参量建立的液体热导率估算模型,不仅对48个羧酸酯分子在不同温度下的746个液体热导率数据具有较好的相关性、显著性和稳定性,而且对训练集以外的羧酸酯分子液体热导率具有很好的预测性。估算结果与Sastri方法和Latini方法比较,不仅相对误差明显减小,而且估算条件简化,可适用的估算范围得到扩大,目标分子结构可以更为复杂。     

专利信息

一种轻质耐火砖(专利申请号: 03100439. 3)　　本发明属于耐火材料领域,特别涉及一种热导率低、寿命长的高温窑炉内衬用优质耐火材料。其特征在于本发明采用莫来石作为主晶相,钙长石作为结合相,其主要化学组成(w)为:Al2O3 54. 0% ~57. 0%,SiO2 40. 0% ~43. 0%,CaO1. 0% ~2. 0%,Fe2O30. 1% ~1. 0%,其他杂质含量为 0. 1% ~0. 7%,所有原料的细度都要符合 0. 088mm方孔筛余量≤ 5. 0%的要求。产品既保持了钙长石轻质耐火砖的低热导率和低体积密度的优点,又使其强度和使用温度有明显的提高,能取代可能致癌的硅酸铝耐火纤维类耐火内衬而用作直…     

电动汽车用低密度导热灌封胶的研制

以双组分加成型导热液体硅橡胶为基料,添加不同规格的中空玻璃微珠作为减重填料,考察了不同规格、不同含量中空玻璃微珠对材料密度、黏度及热导率的影响。结果表明,中空玻璃微珠的加入可以降低液体硅橡胶的密度,相同用量时,粒径大、密度小的A型中空玻璃微珠对密度的影响较大;中空玻璃微珠的加入会引起材料黏度上升,且对热导率高的液体硅橡胶的影响更显著;在本实验用量范围内,中空玻璃微珠对材料热导率的影响较小。     

Solubility of 4-(3,4-dichlorophenyl)-1-tetralone in eleven alcohols with the temperature range from 283K to 323K

The solubility of 4-(3,4-dichlorophenyl)-1-tetralone in eleven alcohols (methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, 2-butanol, 2-pentanol, 1,2-propanediol, 1,3-propanediol) was measured by using a laser technique with a temperature range from 283 K to 323 K, and at atmospheric pressure. For mono n-alcohols, the solubility is the lowest in methanol, increasing with the carbon chain of the alcohols. The results were correlated with a semi-empirical equation. The experimental solubility and correlation equation in this work can be used as essential data and models in the purification process of 4-(3,4-dichlorophenyl)-1-tetralone.     

Measurement,correlation and prediction of binary vapor-liquid equilibria for alcohol-tetrachloroethene systems

Experimental isobaric vapor-liquid equilibria of binary mixtures of tetrachloroethene with ethanol, 2-propanol, 2-butanol and 2-pentanol have been measured at 101.08 kPa. The UNIFAC (Fredenslund et al., 1975), a group contribution model and the activity coefficient models of Margules and Van Laar (as presented by Carlson and Colburn, 1942), Wilson (1964), NRTL (Renon and Prausnitz, 1968) and UNIQUAC (Abrams and Prausnitz, 1975) have been used to predict the vapor composition from measured T-x data of ten binary mixtures of alcohol-tetrachloroethene including these four systems. The average absolute deviation between the experimental and the predicted vapor composition with the UNIFAC model ranges from 0.006 to 0.023 mole fraction and that with the activity coefficient models ranges from 0.003 to 0.038. The maximum deviation in both the cases occurred in the data of 1-propanol (Venkateswara Rao et al., 1980).     

Measurement and correlation for solubility of diosgenin in some mixed solvents简

The solubility data of diosgenin in mixed systems of ethanol ＋ 1-propanol （1 ： 1）, ethanol ＋ 1-butanol （1 ： 1）, ethanol ＋ isobutyl alcohol （1 ： 1）, methanol ＋ isobutyl alcohol （1 ： 1）, methanol ＋ isobutyl alcohol （1 ： 4）, ethanol ＋ 1-pentanol （1 ： 1） and carbon tetrachloride were measured over the temperature range from 289.15 K to 334.15 K by a laser monitoring observation technique at atmospheric pressure, with all mixtures mixed by volume ratio. The Apelblat equation, the ideal solution model, and the 2h equation are used to correlate the solubility data. The results show that the three models agree well with the experimental data, providing essential support for industrial design and further theoretical study.     

A generalized corresponding states method for predicting the limits of superheat of mixtures: Application to the normal alcohols

The limits of superheat of the normal alcohols from methanol to octanol and of ethanol/n-propanol, n-propanol/n-butanol, and n-butanol/n-pentanol mixture were measured at atmospheric pressure. The results were predicted using a new method based on the generalized corresponding states principle (GCSP) in which properties of two reference substances were used to predict the superheat limits of the fluids studied. Ethanol and n-butanol, and the two components of each mixture studied, were used as reference fluids for predicting the superheat limits of the pure alcohols and mixtures respectively.Results showed that it is possible to predict superheat limits to well within the accuracy of measured values ( < 1%). The method requires only accurate vapor pressure correlations and acentric factors of the reference fluids, and an accurate method for predicting the variation of the true critical mixture temperature with composition. It is shown that the GCSP reduces to an expression for the superheat limit of a mixture which is a mole fraction weighted average of the limits of superheat of the individual components in solution when the mixture and its components satisfies certain conditions. In the general case, both linear and nonlinear variations of mixture superheat limit with mole fraction can be predicted with the proposed method.Considerable simpiflication using the GCSP over the approach based on classical homogeneous nucleation theory is derived from the fact that no mixture surface tension or bubble point pressure data are required.     

Solvent optimization for efficient enzymatic monoacylglycerol production based on a glycerolysis reaction

This study was aimed at screening solvent systems of varying polarities to identify suitable solvents for efficient and practical enzymatic glycerolysis. Several pure solvents and solvent mixtures were screened in a batch reaction system consisting of glycerol, sunflower oil, and Novozym^® 435 lipase. Out of 13 solvents tested, tert-butanol and tert-pentanol were the only pure solvents suitable for a fast glycerolysis reaction with an acceptably high formation of MAG. In these systems, MAG contents of 68–82% were achieved within a few hours. Mixtures of tert-butanol/hexane, tert-pentanol/hexane, and tert-butanol/tert-pentanol in varying ratios also gave high MAG contents (58–78%). The tertiary alcohols tert-butanol and tert-pentanol, or mixtures of one of them with hexane, seemed to be the best choice among the solvents tested with respect to reaction efficiency, practical industrial applications, and steric hydroxyl group hindrance, which suppresses the ester formation with FA.     

Measurement of vapor-liquid equilibria using a semi-continuous total pressure static equilibrium still

The total pressure static equilibrium still designed by Gibbs and Van Ness has been modified to increase its accuracy. It was tested by comparing calculated vapor compositions and excess Gibbs free energies with literature data for mixtures of ethanol and n-heptane at 30°C. Experimental data are presented for 1-pentanol/n-hexane mixtures at 30° and 50°C, for 1-pentanol/n-pentane mixtures at 30°C, and for 1-butanol/n-pentane mixtures at 30°C.     

Predicting the vapor-liquid equilibrium of carbon dioxide+alkanol systems by using an artificial neural network

A multi-layer feed-forward artificial neural network has been presented for accurate prediction of the vapor liquid equilibrium (VLE) of CO₂+alkanol mixtures. Different types of alkanols namely, 1-propaol, 2-propanol, 1-butanol, 1-pentanol, 2-pentanol, 1-hexanol and 1-heptanol, are used in this study. The proposed network is trained using the Levenberg-Marquardt back propagation algorithm, and the tan-sigmoid activation function is applied to calculate the output values of the neurons of the hidden layers. According to the network’s training, validation and testing results, a six layer neural network is selected as the best architecture. The presented model is very accurate over wide ranges of experimental pressure and temperatures. Comparison of the suggested neural network model with the most important thermodynamic correlations shows that the proposed neuromorphic model outperforms the other available alternatives. The predicted equilibrium pressure and vapor phase CO₂ mole fraction are in good agreement with experimental data suggesting the accuracy of the proposed neural network model for process design.     

Experimental and predicted enthalpies of mixing of mixtures formed from alcohols and sunflower oil at 298.15 K

The enthalpies of mixing of systems formed from alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol) and sunflower oil at 298.15 K are presented. Enthalpies were measured in the composition range in which the compounds were miscible. From the experimental measurements, we calculated the heat capacities of the mixtures. Several group contribution models were applied to estimate the enthalpies of mixing of these mixtures. The average deviations varied from 10 to 60%, depending on the model and compound. The best prediction in all cases was the Nitta model, with average deviations from 10 to 30%. The novelty of the work is that models of this type have not been applied previously to predict enthalpies of such large molecules, and the results of the estimates are of the same order as other types of compounds (pure compounds of small size).     

Orientation effect on sign and magnitude of excess thermodynamic functions of non electrolyte solutions at different temperatures (303.15 K, 308.15 K,and 313.15K)

Experimental values of the density and viscosity have been measured for binary mixtures of N-ethylaniline with isomeric butanols (1-butanol, 2-butanol, 2-methyl-1-propanol and 2-methyl-2-propanol) at 303.15, 308.15 and 313.15 K over the entire mole fraction range. These data, the excess molar volumes, and deviation viscosity for the binary systems at the above-mentioned temperatures were calculated and fitted to Redlich-Kister equation to determine the fitting parameters and the root-mean-square deviations. The excess molar volumes, deviation viscosity and excess Gibbs energy of activation of viscous flow have been analyzed in terms of acid-base interactions, hydrogen bond, and dipole-dipole interaction between unlike molecules. The results obtained for dynamic viscosity of binary mixtures were used to test the semi-empirical relations of Grunberg-Nissan, Katti-Chaudhri, and Hind et al. equations.     

Density, ultrasonic velocity, viscosity and their excess parameters of the binary mixtures of N,N-dimethylaniline+1-alkanols (C3-C5), +2-alkanols (C3-C4), +2-methyl-1-propanol, +2-methyl-2-propanol at 303.15K

The density, ultrasonic velocity of sound and viscosity of binary mixtures of N,N-dimethyl aniline (N,NDMA) with 1-propanol, +2-propanol, +1-butanol, +2-butanol, +1-pentanol, +2-methyl-1-propanol, +2-methyl-2-propanol were measured at 303.15 K. These experimental data have been used to calculate excess volume V ^E , excess ultrasonic speeds u ^E , excess intermolecular free length L _f ^E , excess acoustic impedance Z ^E , excess isentropic compressibility κ _s ^E , deviation in viscosity Δη and excess Gibbs free energy of activation of viscous flow (G* ^E ). The values of L _f ^E and κ _s ^E are negative over the wide range of composition for all the binary mixtures, while the values of Z ^E are positive. These results have been used to discuss the nature of interaction between unlike molecules in terms of hydrogen bonding, dipole-dipole interaction, proton-acceptor interaction and dispersive forces. The viscosity data have been correlated using three equations: Grunberg and Nissan, Katti & Chaudhri and Hind et al. The excess/deviations were fitted by a Redlich-Kister equation and the results were analyzed in terms of specific interactions present in these mixtures.