运用ChemCAD计算氢气在烃类中的溶解度

运用ChemCAD闪蒸分离模块建立模拟流程,考察了8种热力学性质计算模型,结果表明API-SRK、SRK、Peng-Rob-inson 3种方法较适合研究氢气在烃中溶解度的模拟计算。氢气、间二甲苯作为进料流股组分,以进料流股组分流率比例为考察对象,流率比值在2/1～2 664/1可完成闪蒸分离平衡计算。在温度为305.15、353、393、433 K,压力为0.8～5.0 MPa条件下,分别对氢气在间二甲苯、环已烷、苯、环已烷和苯中进行闪蒸平衡分离计算,计算结果为氢气在烃类中溶解度变化规律随温度压力的升高而增大,溶解度计算值与实验值相对偏差在5%以内。以上结果表明,选择合适的热力学性质计算模型和进料流股组分流率比例,运用ChemCAD闪蒸分离模块可准确计算氢气在烃类中溶解度。

偏心因子数据的计算方法研究进展

从偏心因子(acentricfactor)的定义出发,分析了ω数据的确定方法和获取数据的手段,评述了国内外ω计算方法的近期进展,包括对应态蒸气压关联方程法、对应态基团贡献法(CSGC)、图论法及拓扑法等,指出了各种方法的优缺点及最新的计算发展方向。

连分式法在计算机辅助数值分析上的应用

本文探讨了连分式在单变量问题数值分析上的应用,以石油化工热力学性质的若干经典计算作为实例,并与经典的拉格朗日(Lagrange)多项式法和牛顿前进法等作了比较。结果表明利用连分式方法较之经典的数值分析方法具有数学运算次数少、方法简单、计算精度高和编程方便等优点。文中提出的各种函数的连分式表示方法,可以方便地编制成递归计算机程序,来解算插值计算、函数求根和极值点确定等问题。

Java-Matlab混合编程的研究

为了在Matlab环境下开发复杂的图形界面程序,本文对Java语言和Matlab语言混合编程进行了研究,提出了两种基于Java SWT图形开发技术的Matlab程序开发方法,详细说明了具体的开发步骤。以理想朗肯循环的热力学性质的计算程序的实现为例,证明了这种混合编程方法的可行性,说明将Java语言开发复杂图形界面的能力和Mat-lab优秀的数学运算和数据处理能力结合起来,能够开发出更专业和功能更强大的软件程序。

速冻装置制冷工质 R22 的替代

本文对替代速冻装置制冷剂Ｒ２２的单元工质（如Ｒ７１７、Ｒ２９０、Ｒ１３４ａ）和混合工质（如Ｒ４０７ｃ、Ｒ４０７ｄ、Ｒ４０７ｅ、Ｒ４１０ａ、Ｒ４１０ｂ、Ｒ４０４ａ、Ｒ５０７）进行了热力计算和循环分析，结果表明经过不断完善上述工质均有望成为Ｒ２２的替代工质。

Calculation and Verification for the Thermodynamic Data of 3CaO·3Al_2O_3·CaSO_4

Calcium sulfoaluminate,3CaO·3Al2O3·CaSO4,has been widely recognized in the realms of high-temperature combustion and cement chemistry.However,the lack of relevant thermodynamic data limits the progress of its research and development.Through comparative calculations using several different approaches,we obtain the thermochemical properties of 3CaO·3Al2O3·CaSO4 in this work,such as its standard formation enthalpy,Gibbs free en- ergy of formation,entropy,and molar heat capacity.With these fundamental data,thermodynamic calculations become possible for reactions involving this mineral.It is found that some reactions proposed in literature to generate this mineral may not proceed thermodynamically.

First-Principle Calculations for Elastic and Thermodynamic Properties of Diamond

The elastic constants and thermodynamic properties of diamond are investigated by using the CRYSTALO3 program. The lattice parameters, the bulk modulus, the heat capacity, the Gruneieen parameter, and the Debye temperature are obtained. The results are in good agreement with the available experimental and theoretical data. Moreover, the relationship between V/V0 and pressure, the elastic constants under high pressure are successfully obtained. Especially, the elastic constants of diamond under high pressure are firstly obtained theoretically. At the same time, the variations of the thermal expansion α with pressure P and temperature Tare obtained systematically in the ranges of 0-870 GPa and 0-1600 K.

Elasticity under pressure and thermal property of Mg2La from first-principles calculations

The elastic properties, thermodynamic and electronic structures of Mg_2La were investigated by using first-principles. The calculated results show that pressure affects the elastic constants of C_(11) more than that of C_(12) and C_(44). Specifically, higher pressure leads to greater bulk modulus(B), shear modulus(G), and elastic modulus(E). We predict B/G and anisotropy factor A based on the calculated elastic constants. The Debye temperature also increases with increasing pressure. Based on the quasi-harmonic Debye model, we examined the thermodynamic properties. These properties include the normalized volume(V/V_0), bulk modulus(B), heat capacity(C_v), thermal expansion coefficient(α), and Debye temperature(■). Finally, the electronic structures associated with the density of states(DOS) and Mulliken population are analyzed.

Phase transition, thermodynamic and elastic properties of ZrC

First principles calculation and quasi-harmonic Debye model were used to obtain more physical properties of zirconium carbide under high temperature and high pressure.The results show that the B1structure of ZrC is energetically more favorable with lower heat of formation than the B2structure,and that mechanical instability and positive heat of formation induce the inexistence of the B2structure at normal pressure.It is also found that the B1structure would transform to the B2structure under high pressure below the critical point of V/V0=0.570.In addition,various thermodynamic and elastic properties of ZrC are obtained within the temperature range of0-3000K and the pressure range of0-100GPa.The calculated results not only are discussed and understood in terms of electronic structures,but also agree well with corresponding experimental data in the literature.

Study of Thermodynamics of Liquid Noble-Metals Alloys Through a Pseudopotential Theory

The Gibbs-Bogoliubov （GB） inequality is applied to investigate the thermodynamic properties of some equiatomic noble metal alloys in liquid phase such as Au-Cu, Ag-Cu, and Ag-Au using well recognized pseudopotential formalism. For description of the structure, well known Percus-Yevick （PY） hard sphere model is used as a reference system. By applying a variation method the best hard core diameters have been found which correspond to minimum free energy. With this procedure the thermodynamic properties such as entropy and heat of mixing have been computed. The influence of local field correction function viz; Hartree （H）, Taylor （T）, lehimaru-Utsumi （IU）, Farid et al. （F）, and Sarkar et al. （S） is also investigated. The computed results of the excess entropy compares favourably in the case of liquid alloys while the agreement with experiment is poor in the case of heats of mixing. This may be due to the sensitivity of the heats of mixing with the potential parameters and the dielectric function.

First-principles calculation of structural and thermodynamic properties of titanium boride

The equilibrium lattice parameters, electronic structure, bulk modulus, Debye temperature, heat capacity and Gibbs energy of TiB and TiB2 were investigated using the pseudopotential plane-wave method based on density functional theory (DFT) and the improved quasi-harmonic Debye method. The results show that the total density of states (DOS) of TiB2 is mainly provided by the orbit hybridization of Ti-3d and B-2p states, and the total DOS of TiB is mainly provided by the hybrids bond of Ti-3d and B-2p below the Fermi level and Ti—Ti bond up to the Fermi level. The Ti—B hybrid bond in TiB2 is stronger than that in TiB. Finally, the enthalpy of formation at 0 K, heat capacity and Gibbs free energy of formation at various temperatures were determined. The calculated results are in excellent agreement with the available experimental data.

Thermodynamics properties and thermal conductivity of Mg_2Pb at high pressure

The thermodynamics properties and thermal conductivity of Mg2Pb at high pressures have been calculated by first-principles.The enthalpy of formation and heat capacity obtained at 0 GPa are in good agreement with the experiments and other theoretical results.The thermal conductivity and coefficient of thermal expansion of Mg2 Pb at high pressure were evaluated.The thermal conductivity presents a second-order polynomial with pressure.The calculated thermal conductivity of Mg2Pb indicates that it is suitable to be used as thermal conductor at 0 K.

Elastic and thermodynamic properties of TiC from first-principles calculations

Using the pseudopotential plane-wave method, we investigate the elastic constants and thermodynamic properties of the rocksalt structure Titanium Carbide (TiC). The obtained lattice parameters, bulk modulus and elastic constants are in very good agreement with the available experimental data and other theoretical results. The thermodynamic properties of the cubic TiC are predicted by using the quasi-harmonic Debye model. The normalized volume V/V 0 , bulk modulus B, thermal expansion , heat capacity C V , Grüneisen parameter and Debye temperature dependence on the pressure and temperature are obtained successfully. At low temperature and low pressure, thermal expansion coefficient increases rapidly with temperature. At high temperature and high pressure, the increasing trend becomes tender. At low temperatures, C V is proportional to T 3 , and C V tends to the Dulong-Petit limit at higher temperatures.

Lattice Dynamics Study of Magnesium Chalcogenides

First-principles calculations,which are based on the plane-wave pseudopotential approach to density functional perturbation theory within the local density approximation,have been performed to investigate the structural,lattice dynamical and thermodynamic properties of zinc blende(B3) structure magnesium chalcogenides:MgS,MgSe and MgTe.The results of ground state parameters and phonon dispersion are compared and agree well with the experimental data available and other calculations.We obtain the change of Born effective charge and LO-TO splitting under hydrostatic pressure.Finally,by the calculations of phonon frequencies,some thermodynamic properties such as the entropy,heat capacity,internal energy,and free energy are also successfully obtained.