A Fundamental Equation for Calculation of the Thermodynamic Properties of Ethanol

A formulation for the thermodynamic properties of ethanol (C₂H₅OH) in the liquid, vapor, and saturation states is presented. The formulation is valid for single-phase and saturation states from 250 to 650K at pressures up to 280MPa. The formulation includes a fundamental equation and ancillary functions for the estimation of saturation properties. The experimental data used to determine the fundamental equation include pressure-density-temperature, ideal gas heat capacity, speed of sound, and vapor pressure. Saturation values computed from the ancillary functions were used to ensure thermodynamic consistency at the vapor-liquid phase boundary. Comparisons between experimental data and values computed using the fundamental equation are given to verify the uncertainties in the calculated properties. The formulation presented may be used to compute densities to within ±0.2%, heat capacities to within ±3%, and speed of sound to within ±1%. Saturation values of the vapor pressure and saturation densities are represented to within ±0.5%, except near the critical point.     

制冷系统仿真中的工质热力性质计算程序

制冷系统仿真中必然用到工质热力性质计算程序,本文针对制冷系统中常用到的9种工质进行了热力性质分析,利用VB6.0编写了其计算程序模块,并在实际的制冷仿真系统中得到了应用,最终通过动力实验平台的测试,证实计算程序是合理的.     

制冷系统仿真中的工质热力性质计算程序

制冷系统仿真中必然用到工质热力性质计算程序,本文针对制冷系统中常用到的9种工质进行了热力性质分析,利用VB6.0编写了其计算程序模块,并在实际的制冷仿真系统中得到了应用,最终通过动力实验平台的测试,证实计算程序是合理的.     

HFC-32制冷剂饱和液体热力性能参数计算模型

制冷剂简单有效的热力性能参数计算模型对制冷循环的仿真是十分必要的.提出了HFC-32制冷剂饱和液体的蒸汽压和密度关联式计算模型;在HFC-32的GMA液体状态方程基础上,利用Helmholtz偏离函数和Maxwell关系式推导出了HFC-32饱和液体的焓、熵和比热容的计算模型;上述各模型均不存在迭代,保证了模型的计算精度和稳定性.将建立的各模型在饱和液体(275 ～ 335K,0.862～4.095MPa)范围内与REFPROP7计算值进行对比,结果表明,所有热力性能参数计算模型的相对平均误差不超过0.776％,最大误差小于4.464％,证明了所建立模型的可靠性.     

First—principle Calculation of the Properties of Ti3SiC2

The electronic and structural properties for Ti3SiC2 were studied using the first-principle calculation method.By using the calculated band structure and density of states,the high electrical conductivity of Ti3SiC2 are explained ,The bonding character of Ti3SiC2 is analyzed in the map of charge density distribution.     

Crossover SAFT Equation of State and Thermodynamic Properties of Propan-1-ol

In this work we have developed a new equation of state (EOS) for propan-1-ol on the basis of the crossover modification (CR) of the statistical-associating-fluid-theory (SAFT) EOS recently developed and applied to n-alkanes. The CR SAFT EOS reproduces the nonanalytical scaling laws in the asymptotic critical region and reduces to the analytical-classical SAFT EOS far away from the critical point. Unlike the previous crossover EOS, the new CR SAFT EOS is based on the parametric sine model for the universal crossover function and is able to represent analytically connected van der Waals loops in the metastable fluid region. The CR SAFT EOS contains 10 system-dependent parameters and allows an accurate representation of the thermodynamic properties of propan-1-ol over a wide range thermodynamic states including the asymptotic singular behavior in the nearest vicinity of the critical point. The EOS was tested against experimental isochoric and isobaric specific heats, speed of sound, PVT, and VLE data in and beyond the critical region. In the one-phase region, the CR SAFT equation represents the experimental values of pressure with an average absolute deviation (AAD) of less than 1% in the critical and supercritical regions and the liquid densities with an AAD of about 1%. A corresponding states principle is used for the extension of the new CR SAFT EOS for propan-1-ol to higher n-alkanols.     

制冷工质R22热力性质的一种快速算法

制冷工质热物性的计算是数值模拟技术非常重要的一个环节，开展这一工作的研究且有重要的价值。本文在结合Martin-Hou方程的基础上提出了制冷工质热力性质的一种快速算法，经实例验证，该算法具有精度高、适应范围广、稳定性好等特点，可供制冷工质热物性算法设计的初学者作参考。     

Calculation of Phase Equilibria Based on the Levenberg-Marquardt Method

The Levenberg-Marquardt method, the best algorithm to obtain the least-square solution of nonlinear equations, is applied to calculate the stable phase equilibria. It can get the best combination between robustness and speed of the calculations. Its application to ternary AI-Si-Mg system is executed in detail. The calculated phase equilibria agree well with the experimental results. Furthermore, the Levenberg-Marquardt method is not sensitive to the initial values.     

基于Pandat的Ti-Al系相图计算及热力学评估

基于相图计算理论,用Pandat 2016热力学计算软件、最新的钛合金数据库和热力学模型,计算研究了Ti-Al二元系相图。从相律、相图的特殊点、各相存在的范围、相变点等方面对其进行了详细的热力学评估。计算结果表明:计算相图和实验相图吻合得较好,其相对误差基本都在5%以内,为推广到三元或更高元体系相图奠定了基础。随后提出了一个新的计算Ti-Al二元系中(α+β)/β相变点的公式,其置信度为99.982%,与经验计算公式相比,计算更为准确,具有一定的参考价值和学术交流意义。     

发展高稳定性718合金的热力学模拟计算

利用Thermo-Calc热力学计算软件和与之相应的镍基高温合会数据库,计算了碳、铝、钛、铌和钨成分改变时对718合金中平衡相的析出规律影响,并预测了平衡相的化学成分,以期为发展高稳定性718合金提供理论依据.     

二元微合金碳氮化物化学组成与固溶度的热力学计算以及钢材化学成分的影响规律

采用热力学计算方法推导出二元微合金碳氮化物的化学组成及有关元素在奥氏体中的固溶度的理论计算式,由此从理论上深入分析讨论了钢材化学成分对二元微合金碳氮化物化学组成的影响规律并导出一些重要的结论。     

An Assessment of Thermodynamic Models for HFC Refrigerant Mixtures Through the Critical-Point Calculation

An assessment of thermodynamic models for HFC refrigerant mixtures based on Helmholtz energy equations of state was made through critical-point calculations for ternary and quaternary mixtures. The calculations were performed using critical-point criteria expressed in terms of the Helmholtz free energy. For three ternary mixtures: difluoromethane (R-32) + pentafluoroethane (R-125) + 1,1,1,2-tetrafluoroethane (R-134a), R-125 + R-134a + 1,1,1-trifluoroethane (R-143a), and carbon dioxide (CO₂) + R-32 + R-134a, and one quaternary mixture, R-32 + R-125 + R-134a + R-143a, calculated critical points were compared with experimental values, and the capability of the mixture models for representing the critical behavior was discussed.     

多边法坐标测量系统中解算方式对测量精度的影响研究

为了研究多边法坐标测量系统中解算方式对测量精度的影响,建立了多边法坐标测量模型,分析了两种目标点坐标解算方式的差异,并针对典型的4台测站多边法坐标测量系统进行了两种解算方式的仿真测量实验。仿真结果表明:预先准确标定系统参数方式能有效提升测量精度,测量精度依次改善了69.5%、64.6%、46.3%。进行了坐标测量精度验证实验,实验结果表明:与同步解算方式相比较,预先准确标定系统参数取模后的3组实验平均测量误差由203.0μm降至23.8μm,且3组实验的测量误差与测量距离的平均相关系数由99.8%降至37.8%,验证了仿真实验结果。     

在爆破设计中基于组合优化的一个新的计算公式

基于超图的性质,提出了一个在爆破设计中由经验公式和经验数据组成的通用的计算公式。当一个目标函数值可由许多公式估算时,它可以选出最好的几个分配问题的模型被用来做更准确地分析,新公式在爆破块度分布的计算中被验证。     

Calculation of the Velocity of Second-Order Thermal Slip Using the Model Kinetic Equation with a Variable Collision Frequency

The problem on the calculation of the second-order thermal slip velocity is solved. For this purpose, an exact solution of an inhomogeneous model Boltzmann kinetic equation with the collision operator in the form corresponding to the BGK model with the collision frequency proportional to the module of intrinsic velocity of gas molecules is constructed. Comparison with the available results is performed.     

Review of the Thermodynamic Properties of Hydrogen Based on Existing Equations of State

Currently available equations of state (EOSs) for hydrogen are reviewed, and the data for the critical point, normal boiling point, and triple point are summarized. Through comparisons of PVT, saturated properties, heat capacity, and speed of sound among the latest EOSs for hydrogen, their features are discussed. The proper use of the EOSs, including a consideration of the nuclear isomers (ortho- and parahydrogen), is of great importance, especially for saturated properties, heat capacity, and speed of sound because these properties are different between the nuclear isomers. The present review concludes with recommendations for use of the EOSs for hydrogen.     

二元金属类水滑石的合成及其作为前驱体对NOx的吸附性能研究

用共沉淀法合成了多种二元金属类水滑石化合物,对其进行了XRD、IR表征,并测试了焙烧产物对NOx的吸附性能.结果表明,合成的样品都具有典型的水滑石层状结构;二元金属类水滑石化合物MAl-HTlcs(M=Cu,Mg,Zn,Co,Ni)对NOx均具有良好的吸附性能,其中锌铝型类水滑石(摩尔比Zn/Al=3)对NOx的吸附速率及饱和吸附量最大,饱和吸附量为1851mg/g.     

The Correlation between the Thermodynamic Functions of Molten Binary Systems of Alkali Metals

Differential thermodynamic equations are used to reveal, in the general form, the correlation between some excess thermodynamic functions of liquid solutions. It is demonstrated that a certain correlation is observed in wide ranges of temperature and concentrations between the calculation and experimental data on excess molar enthalpy and specific volume of molten Na-K and K-Cs systems.     

基于微扰理论的静电电子透镜的缺陷电场计算

研究了用于计算电子光学系统的缺陷电场和容差的微扰理论。基于微抗原理，推导了计算静电电子透镜由于电极偏心、倾斜和加工不圆造成的电场变化及其旁轴多极场展开函数的九点有限差分公式，编制了计算软件。建立了两个电场解析模型，通过该模型的解析解与数值计算结果的对比，证实了算法及软件的正确性，并据此讨论了微扰理论用于容差计算的适用范围。计算了几个静电电子透镜的例子，给出了不同电极缺陷的电位分布和微扰多极场分布。     

An Equation of State for the Hard-Sphere Chain Fluid Based on the Thermodynamic Perturbation Theory of Sequential Polymerization

New equations of state for freely jointed hard-sphere chain fluids are developed. The equations of state are based on the thermodynamic perturbation theory. The new equations of state use the contact values of the radial distribution function (RDF) for monomer–dimer mixtures, which is derived from the multidensity Ornstein–Zernike theory. These RDFs are composed of a monomer reference term, the Carnahan–Starling or the Percus–Yevick expression, and an additional bond contribution. These equations of state are then extended to real fluids. To calculate the phase equilibrium properties of nonassociating chain fluids, a dispersion contribution is added to the repulsive hard-chain reference term. With the new equations of state of chain fluids supplemented with the dispersion term, the vapor pressures and the coexisting densities of several real fluids are calculated.