探讨求解Van der waals方程程序设计

求解van der waals方程涉及到求一元三次方程的解,手工计算比较复杂,该文提出了用计算机程序求解实际气体摩尔体积van der waals方程的程序设计方法。     

1,2-丙二醇+丁醇/戊醇/己醇二元系的过量体积和黏度

常压下测定了1,2-丙二醇分别与丁醇、戊醇和己醇组成的二元系在293.15~318.15 K下的密度和黏度,建立了混合液密度和黏度随温度和组成变化的方程。计算了过量摩尔体积VE,黏度偏差Δη和过量流动活化自由能ΔG*E。结果表明,三个二元系的过量摩尔体积在全浓度范围内均为正值,随温度升高,偏差增大,但发生最大偏差时的溶液组成不同;过量摩尔体积值按丁醇-戊醇-己醇顺序逐渐增大;黏度偏差和过量流动活化自由能三个体系显示了相同的变化关系,均为负值,且都随温度降低而偏差增大。利用Redlich-Kister方程对过量性质进行了关联。分析和讨论了分子间相互作用。     

乙酸乙酯-异丙醇混合液的密度和折光率

常压下测定了乙酸乙酯-异丙醇二元混合液在293.15—318.15 K下的密度和折光率,建立了该二元混合液密度与组成和温度关系的计算方程。计算了过量摩尔体积、折光率偏差,分别用Redlich-Kister方程进行了关联。过量摩尔体积在全摩尔分数范围内为正值,而折光率偏差为负值,且均随温度升高而偏差增大。利用Lorentz-Lorenz关系式计算了二元体系的摩尔折光率和摩尔折光率偏差,偏差亦随温度升高而增大。     

用拓扑学方法研究烷烃的化学

用拓外学方法建立分子结构与性能的关系一直是化学工作者在基础理论研究中的重要课题之一.1947年,Wiener最先提出了分子的两个拓扑指数,并用它对分子的沸点,汽化热进行了研究.以后,又有不同的研究者探讨了Wiener指数与烷烃分子的摩尔折射率,摩尔体积,标准熵,密度等关系.1975年Randic提出了一个新的拓扑指数即分支指数,简称R指数.梅平等曾关联了烷烃的标准生成焓,标准燃烧焓,标准熵等物质的13种现代性质与R指数的关系.在Randic方法的基础上,Kier和Hall又提出了分子连接性指数的概念及其计算方法.     

[Bmim]BF4离子液体在甲醇中的体积和黏度性质

在298.15 K和常压下,测定了1-丁基-3-甲基咪唑四氟硼酸([Bmim]BF4)离子液体+甲醇体系的密度和黏度。由密度计算了体系的表观摩尔体积,并采用Redlich-Mayer方程关联了体系的表观摩尔体积与组成的关系,得到了[Bmim]BF4在甲醇中的标准偏摩尔体积。由Jones-Dole方程对体系的黏度随组成的变化进行了拟合,获得了[Bmim]BF4在甲醇中的黏度B系数。结果表明:[Bmim]BF4+甲醇体系的表观摩尔体积和黏度均随[Bmim]BF4浓度的增加而增加,[Bmim]BF4在甲醇中的标准偏摩尔体积和黏度B系数分别为155.72×10-6m3/mol和0.282 9。     

预估火炸药寿命的数学模型及其计算

评论了预估火炸药及其制品的安全贮存寿命、使用寿命和可靠贮存寿命的数学模型和计算方法,包括常用的Arrhenius方程、Berthelot方程和温度系数方程及修正的Arrhenius方程、加速因子方程、多应力因素的Eyring方程、交变老化温度的累积损伤模型、BP神经网络法、结构寿命和可靠寿命的预估方法等。提出了简单快速的点斜法和单温度定时法,认为可以通过失效概率的所谓界限模型计算火炸药及其制品的可靠性和可靠贮存寿命。比较了一些计算方法,给出了Arrhenius方程和Berthelot方程预估寿命相等的条件,指出了这些方法或方程的使用范围,并举例说明了一些模型和计算方法的实际应用。附参考文献30篇。     

正常沸点下液体蒸发焓的基团贡献计算法

用分子热力学方法建立了纯物质汽液平衡的推广vanderWaals模型 ,并据此得到了一个计算正常沸点下液体蒸发焓的方程 .它只含有一个与分子大小有关的参数 .这个参数的值与正常沸点下液体的摩尔体积成正比 ,且具有基团加和性 .为此 ,用 484个有机物回归得到了 45个基团增量 .对这些有机物的蒸发焓计算结果表明 ,与实验值的平均绝对偏差 (AAD)为 1.39% ,优于文献发表的其他方法     

乙酸乙酯/四氯化碳二元混合体系的体积性质

常压下测定了乙酸乙酯与四氯化碳二元体系在288.15-323.15 K内全摩尔分数范围的密度,分别建立了该二元体系密度与组成和温度的计算方程.在此基础上,计算了该二元体系的超额摩尔体积,结果表明:该二元体系的超额摩尔体积在所测定温度和全摩尔分数范围内均呈正偏差,且均随温度的升高而偏差增大,并利用Redlich-Kist...     

pH值对双甘肽体积性质影响的研究

使用石英振荡管密度计精确测定了298.15 K温度下双甘肽在不同pH值的磷酸钠缓冲溶液中的密度,计算得到双甘肽的表观摩尔体积V,线性拟合得到极限偏摩尔体积和实验斜率Sv。结果表明,pH值对双甘肽的体积性质有明显影响。从溶质与溶剂分子间相互作用及溶质与溶质分子间相互作用对体积性质的变化规律进行了讨论。     

1,3-丙二醇与水、乙醇二元混合体系超额体积

测定了常压下1,3-丙二醇-水和1,3-丙二醇-乙醇两个二元混合体系纯组分及混合液在328.15～348.15 K温度内全浓度范围的密度,计算了体系的超额摩尔体积等性质。两个二元混合体系的超额摩尔体积在所测定的温度和全浓度范围内均呈负偏差。体积数据说明1,3-丙二醇-水、乙醇混合体系中不同分子间的交叉缔合强于同分子间的自缔合,同时组分间分子大小的不对称产生填充效应。     

CFD predictions for hazardous area classification

This study aimed to describe a Computational Fluid Dynamics(CFD) procedure using the ANSYS CFX software 16.1 and Design of Experiments for the determination of volume and extension of explosive atmospheres due to fugitive emissions of flammable gases.The multidimensional statistical sampling technique Latin Hypercube was used, which defined 100 simulations of random methane gas leak conditions.The CFD model proved to be robust in predicting the extension and volume of the explosive atmosphere for orifice diameters from 0.1 to2.5 mm, pressure from 0.1 MPa to 12 MPa and temperatures from 0 ℃ to 400 ℃.It was found that the calculation domain must be parameterized 8 m in length for each millimeter of the diameter of the source of release to ensure the predictions.In order not to lose precision for very small diameters, the mesh was parameterized with 50 elements along the orifice diameter.It was proved that gravity does not influence the extension and volume of the explosive atmosphere at sonic emissions.The deviation from the ideal gas behavior in the reservoir,achieved by applying the Soave–Redlich–Kwong equation of state, also has not significantly influenced the extension and volume of the explosive atmosphere.The results showed that the size of the explosive atmosphere varies directly with the diameter of the source emission and reservoir pressure, and inversely with the temperature of the reservoir.The diameter of the source is the parameter that has the major effect on the extension of the explosive atmosphere, followed by the pressure and lastly the temperature of the reservoir.     

Kinetic interpretation of influence of sodium chloride concentration and temperature on xanthan gum dispersion flow model

The present study derives a fixed‐concentration (0.4%) xanthan gum dispersion flow model for different molar concentrations of sodium chloride (0–0.25M) and different temperatures (20–70°C). The Ostwald–de Waele model is used in all cases. A temperature rise reduces the shear‐thinning characteristics of the systems, although the power law index is much less sensitive to changes in temperature when NaCl is added, even in very small amounts. The lowest consistency values correspond to the dispersions formulated in the absence of salt, the highest values are observed for molar values of ≥0.15, and there are decreases in consistency upon raising the temperature in all cases. The viscous behavior of the dispersions is interpreted using the Eyring equation. The activation energy and the free volume decrease when the shear rate is increased. The addition of NaCl, regardless of the molar concentration involved, provokes an important decrease of the activation energy. The free volume is independent of the molar concentration of NaCl for molar values >0.025. These results are related to the structure of the dispersions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 332–339, 2002     

Volumetric expansion and vapour–liquid equilibria of α-methylstyrene and cumene with carbon dioxide at elevated pressure

Volumetric expansion data and vapour-liquid equilibria (VLE) for α-methylstyrene (AMS) with CO₂ are reported at temperatures of 308 and 323 K and pressures approaching the mixture critical point. Similar data are reported for the mixture of carbon dioxide and cumene at a temperature of 323 K. It is shown that the volumetric expansion data for the various systems coincide when plotted as a function of the solubility of CO₂ in the liquid phase. A procedure is described for calculating the molar volume of the liquid phase from the phase compositions and volumetric expansion data. The experimental VLE data are correlated with the Peng-Robinson (PR) equation of state and the interaction parameter for each binary system is obtained by regression. The interaction parameter is subsequently used to predict the liquid molar volume for each binary system. The use of a single interaction parameter with the PR equation of state provides a satisfactory correlation of the liquid molar volume.     

变阱宽方阱链流体状态方程模拟制冷剂的汽液平衡

应用作者先前基于二阶微扰理论和PY2近似积分方程建立的可变阱宽方阱链流体状态方程模拟了纯制冷剂及其混合体系的汽液平衡。通过关联不同温度下制冷剂的饱和蒸气压和液体体积得到了18种纯制冷剂的分子参数,新方程计算的饱和蒸气压和液体体积总的平均偏差分别为1.11％和0.92％。结合简单混合规则,将此方程扩展到混合体系。研究发现,建立的方程可满意预测制冷剂二元混合体系除临界区附近外的汽液平衡,对两个三元体系汽液平衡的预测也取得了满意的效果,当引入一个与温度无关的可调参数时,关联精度大为提高,预示着新的方程可模拟制冷剂的汽液平衡。     

Prediction of adsorption equilibrium using a modified D-R equation: pure organic compounds on BPL carbon

A method for predicting adsorption equilibrium using a modified Dubinin-Radushkevich (D-R) equation is presented in this paper. We focus on adsorption of pure organic compounds on BPL-activated carbon. We introduce a new variable k_v, a volume adjusting coefficient, and simply use V_b, the constant molar volume of the adsorbate at its normal boiling temperature, instead of V_m, the temperature-dependent molar volume of the adsorbate at the adsorption temperature. The model parameters in the modified D-R equation for an adsorbate are predicted from V_b. Overall, the modified D-R equation gives more accurate results than the traditional one.     

离子液体[C4mim][PF6]与N, N-二甲基甲酰胺二元混合物在298.15 K～318.15 K的密度和粘度

Viscosities and densities for 1-butyl-3-methylimidazolium hexafluorophosphate （[C4mim][PF6]） and N, N-dimethylformamide （DMF） binary mixtures have been measured at the temperature range from 293.15 K to 318.15 K. It is shown that the viscosities and densities decrease monotonously with temperature and the content of DMF. Various correlation methods including Arrhenius-like equation, Sedclon et al.＇s equation, Redlich-Kister equation with four parameters, and other empirical equations were applied to evaluate these experimental data. A model based on an equation of state Ior estimating the viscosity of mixtures containing ionic liquids were proposed by coupling with the excess Gibbs free energy model of viscosity, which can synchronously calculate the viscosity and the molar volume. The results show that the model gives a deviation of 8.29% for the viscosity, and a deviation of 1.05% for the molar volume when only one temperature-independent adjustable parameter is adopted. The correlation accuracy is further improved when two parameters or one temperature-dependent parameter is used.     

A method for determination of thermodynamics and solubility parameters of polymers in dilute solutions from critical volume fractions

An equation using the critical volume fraction and segment number of polymer was proposed for the partial molar entropy change of a polymer for mixing in dilute solution. The partial molar enthalpy change of polymer for mixing was determined from the thermodynamic equilibrium property of two polymer phases at the critical temperature. The solubility or cohesion parameter of a polymer fraction at the critical temperature was calculated by using the partial molar enthalpy change and repeat unit volume of the polymer. The solubility parameter of high molar mass polymer at the theta temperature was determined by extrapolating solubility parameter values of the polymer fractions to high molar mass by using the solubility parameter-segment number relation of polymer fraction. This relation gives good straight line. The solubility parameter of the polymer at the theta temperature and the exchange energy parameter for polymer-solvent pair were obtained directly from the intercept and the slope of this line, respectively. These equations were applied to the critical point data of polystyrene (PS) in methylcyclohexane (MCH) and in cyclohexane (CH) solutions. The results obtained in this study coincide with the literature values for the solubility parameter of PS and exchange energy parameter for PS in CH solution. It was also found that the partial molar entropy change of a polymer for mixing at theta temperatures has about a constant value.     

活性炭上吸附平衡的三种预测方法比较

在用三种方法(摩尔体积、分子等张比容及摩尔电子极化度)计算亲和系数β的基础上,用polanyi-Dubinin方程预计了25℃下八种有机蒸汽以及25、40和60℃下另两种有机蒸气在活性炭上的吸附等温线.相应的实验数据用重量法测定.预计的和实验的数据对比表明:(1)对于优化的预计,参照物应与被预计吸附质有相似的极性;(2)选择适宜的参照物后,三种预计方法在精度上无明显差异;(3)对不同温度下的预计,摩尔体积法更为简便、实用.     

无TNT铵脲炸药配方和爆炸性能的关系

研究了AN-UN、AN-UN-A l两种无TNT铵脲炸药的配方和爆炸性能关系。结果表明,对于AN-UN炸药,随着硝酸脲含量由10%增至40%,炸药的爆热Qv减少16%,比容Vo增加2%,QvVo的乘积下降12.5%。因此,在不含其它成分的情况下,UN含量以10%~20%为宜,基本满足爆炸要求。对于AN-UN-A l炸药,在氧平衡为零的情况下,铝粉的加入能提高炸药爆热,但比容有所下降,QvVo的乘积增加。在铝粉含量10%不变的情况下,AN或UN含量的改变对炸药爆炸性能影响不大。