四元体系汽液平衡的热力学一致性逐点检验

<正> 1 引言 以往用于多元体系汽液平衡的热力学一致性逐点检验的算法大多是有限差分法,对三元体系变成求解10~4～10~6量级的非线性方程组,收敛速度极慢,计算不稳定,难以实际应用。以后不同作者提出不同方法使多元体系热力学一致性逐点检验得到相应的改善。本文将加权残差法的特例——最小二乘法,用于四元体系恒温及恒压的汽液平衡的热力学一致性逐点检验。     

含盐体系汽液平衡的热力学一致性检验

将拟二元方法与Barker法相结合可从三元含盐体系的P-T-x数据推算相应的平衡汽相组成,逐点比较其推算值与实测值,即可检验汽液平衡数据的热力学一致性.具体地对醇(乙醇、异丙醇)-水-盐(氯化钙、醋酸钾)体系的等压汽液平衡数据进行了热力学一致性检验,所得结果满意.含盐溶液P-T-x推算汽相组成的成功,为改进含盐溶液汽液平衡的测试手段创造了条件.     

甲苯-苯甲醛-苯甲酸体系汽液平衡的研究

本文在600×1.333×10~2Pa和400×1.333×10~2Pa压力下分别测定了甲苯-苯甲醛-苯甲酸三元体系及其三个二元体系的汽液平衡数据。用点检验法对二元数据进行了热力学一致性检验,并用Margules、wilson、NRTL和UNIQUAC方程作热力学关联。预测了三元汽液平衡关系,与实测值吻合结果令人满意。     

碳酸二甲酯-苯甲醇体系汽液平衡的研究

试验测定了碳酸二甲酯-苯甲醇体系在常压下的汽液平衡数据,采用Herrington法对数据进行了热力学一致性检验,结果表明所测数据符合热力学一致性。同时依据测定的汽液平衡数据计算出碳酸二甲酯及苯甲醇的无限稀释活度系数,求出Wilson活度系数模型参数,并计算了该体系于413.15 K的汽液平衡数据。     

常压下环己烯-环己酮二元体系汽液平衡研究

H2O2氧化环己烯合成环氧环己烷有很多副产物生成,如环己酮、环己醇等,为了获得较纯的环氧环己烷需采用精馏提纯的方法将副产物分离出来.而精馏提纯需要相关体系的汽液平衡数据,为此用改进的Rose汽液平衡釜测定常压下环己烯-环己酮二元体系汽液平衡数据,并对数据进行热力学一致性检验,结果表明实验数据符合热力学一致性.以汽相组成...     

常压下叔丁醇-水-乙二醇体系汽液平衡测定与关联

在常压(101.3 kPa)下,采用改进的Othmer汽液平衡釜测定了叔丁醇-乙二醇体系的汽液平衡数据,对所测得的数据进行热力学一致性检验,结果表明实验数据符合热力学一致性。用NRTL模型对叔丁醇-乙二醇体系的汽液平衡数据进行关联,得到二元交互作用参数,并用这些参数计算汽相组成及平衡温度,计算结果与实验数据吻合。测定了叔丁醇-水-乙二醇三元体系的汽液平衡数据,乙二醇存在下,叔丁醇-水体系的相对挥发度大幅提高,证明乙二醇是萃取精馏分离叔丁醇-水体系的优良溶剂。     

环氧乙烷—乙醛—水三元体系汽液平衡

本工作采用恒温流通法测定了环氧乙烷—乙醛、环氧乙烷—水、乙醛—水三组二元体系及环氧乙烷—乙醛—水三元体系在10℃条件下的汽液平衡数据。用Wilson方程对测得的汽液平衡数据进行热力学关联,确定了三对Wilson能量参数。所测三对二元数据与文献值基本相符,三元体系的计算值与实测值一致。用面积法对上述汽液平衡数据进行热力学一致性检验,结果令人满意。     

苯-噻吩-DMF体系汽液平衡的研究(Ⅰ)——用鼓泡平衡釜及双柱法测定大沸点差体系汽液平衡数据

用鼓泡平衡釜分别在不同温度下测定了苯-噻吩-DMF(N,N-二甲基甲酰胺)体系的汽液平衡数据,一种新的分析方法—双柱法被用于具有大沸点差的二元和三元体系汽液相样的组成分析,测得的汽液平衡数据经热力学一致性检验及多种模型的关联,其结果令人满意。     

正戊醇、正己醇与二甘醇二元体系汽液相平衡测定

以双循环平衡釜测定了120×1.333×10~2Pa下正戊醇-二甘醇和正己醇-二甘醇二元体系的汽液相平衡组成,数据用微分法检验其热力学一致性,并以常用活度系数方程作了关联。     

乙苯或二甲苯和异丙醇二元体系等压汽液相平衡

用经E llis汽液平衡釜验证的自制汽液平衡釜测定了异丙醇+乙苯及异丙醇+邻二甲苯、间二甲苯、对二甲苯4个二元液系在压力为99.80 kPa时的等压汽液平衡数据,并进行了热力学一致性检验。用UNIQUAC模型处理了实验数据,得出了二元体系的混合自由能。这不仅为二元液系混合体系充实了实验数据,还为二元液系的热力学研究丰富了理论依据。     

正常沸点下液体汽化热的计算

本文从修正Clapeyron方程出发,提出一个新的计算正常沸点下液体汽化热的方程。并提出一个校正沸点的方法。用本文方法对160种物质汽化热进行计算,经同文献方法比较,本方法计算误差为最小。     

浮头法兰计算方法讨论

按照目前我国压力容器设计标准中所给出的浮头法兰厚度计算公式进行计算时,会出现前后两次的厚度计算不一致的问题,压力容器计算软件SW6－1998的现版本在计算中采用叠代方法以避这个问题,为了避开出现死循环的现象,软件以循环中的最大值输出,本文对标准中公式的来源进行了分析,找出了出现以上问题的原因,然后,对标准中给出的公式形式和软件可采用的合适计算方法进行了讨论。     

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     

FIXED POINT METHOD IN STEADY STATE ANALYSIS. APPLICATION TO CATALYST PELLETS

An integral equation method is proposed for evaluating concentration distributions inside catalyst pellets. For low Thiele moduli this method is proved to be strictly contractive. For high Thiele numbers a regularization procedure is discussed. Numerically, the implementation of the algorithm reduces to an iterative procedure which is algorithmically simple and accurate. The problem of the multiplicity of steady states can be treated within the framework of the present method. Some examples of application are developed.     

Numerical modeling and analysis of strength properties in glass

This paper describes the methods for calculating strength properties of glass plates, such as deflection and stresses arising when static load is applied to glass. The specifics of various methods for calculating deflection and stresses are discussed. The problem is posed mathematically and the results of numerical solution of the corresponding boundary problem for a fourth-order partial differential equation (known as the biharmonic equation) are given. The numerical results are obtained with the use of the grid method developed by the authors.     

Improved Equation of the Continuous Particle Size Distribution for Dense Packing

The Furnas model describes the discrete particle size distribution for densest packing. Using a model that considers a continuous particle size distribution for the densest packing to be a mixture of infinite Furnas discrete particle size groups, an equation for the cumulative particle size distribution providing the densest packing was derived. Monosize particles with different shapes have a different packing pore fraction. One parameter in the equation is the pore fraction of packed monosize particles; the particle size distribution for achieving densest packing is a function of this pore fraction. A reduced form of this equation is also presented as a working equation. The equation derived here is compared to the modified Andreasen equation for dense packing. An equation and the correlated graph for calculating theoretically the geometric mean particle size and an equation for calculating the specific surface area of the particle size distribution of the improved equation are also derived.     

求解对流扩散问题的积分方程法

提出了一种求解对流扩散问题的积分方程法。在这一方法中,首先利用Laplace方程的级数形式的格林函数将对流扩散方程转化为积分方程,然后利用级数的正交性质,把积分方程进一步简化为代数方程组,求解该方程组即可得到对流扩散方程的级数形式的近似解。最后,分别利用Chebyshev多项式和Fourier级数求解了3个典型的一维和二维对流扩散问题。该方法和有限体积法、有限元法和迎风差分法相比,展现出非常高的精度并且避免了由解的不连续性造成的虚假振荡。     

Cone calorimeter — an alternative calibration constant calculation

This paper focuses on an alternative method of calculating the calibration constant, C, used in the cone calorimeter. The alternative method is derived from the principles of thermochemistry. It is based on carbon dioxide measurements and implicit knowledge of water vapour and fuel mass loss and is independent of the oxygen concentration. In the final form, the equation for the alternative calibration constant is much simpler than the standard equation. An uncertainty analysis of the alternative technique is also presented in this paper and the alternative method was found to a have marginally lower uncertainty than the Standard method. Notwithstanding these advantages, the Standard method remains the preferred technique for calculating the calibration constant as it is based on the operating principle of the apparatus and includes an oxygen measurement term. However, the alternative method can be easily incorporated into software and act as a means for checkin/troubleshooting the cone calorimeter. Copyright © 2000 John Wiley & Sons Ltd.     

A new method for calculating and correcting molecular weight distributions from gel permeation chromatography

A new method for calculating and correcting molecular weight distributions of polymer samples from GPC chromatograms is presented. The integral equation which relates the true molecular weight distribution of polymer sample to the chromatogram is reformulated into an equivalent variational problem of quadratic functional. The method of steepest descent in the function space is then applied to the minimization problem to obtain the true molecular weight distribution. This method is efficient and reduces some of the oscillation problems encountered in the previous methods. Examples are given.