形状因子对应态原理预测流体的热力学性质

采用形状因子对应态原理,由纯流体的蒸汽压和饱和汽液相密度方程得到的保形参数,由此推算其它区域内的Ｐ－Ｖ－Ｔ性质、第二ｖｉｒｉａｌ系数、焓、熵、热容和混合物的汽液平衡等热力学性质,计算结果与文献值符合较一致     

实际流体的微扰理论状态方程研究

在微扰理论和硬球链状态方程基础上,对链状分子间中的氢键作用采用了一种新的处理方法,提出一个新的三参数的实际流体状态方程。将此方程用于关联３３个纯液体的饱和蒸汽压和液体密度,并由所得到的参数预测了汽相的密度。此状态方程比ＡＰＡＣＴ和ＳＡＦＴ状态方程简单,而计算的精确度则相当     

立方型转子链状态方程及其应用(一)

本方程应用于非极性系统热力学性质(特别是液相密度)及相平衡的预测,一般优于目前应用很广的Soave和Peng-Robinson方程,对45种纯极性物质拟合蒸汽压数据的平均误差为0.49％,应用于关联低压和高压强极性混合物的汽液平衡数据也取得良好结果,对前者一般可达到(或超过)Wilson活度系数模型关联的精确度。     

乙二醇和乙二醇二乙酸酯二元混合物热力学性质研究

在自制的减压汽-液平衡装置上测量了减压条件下乙二醇和乙二醇二乙酸酯的纯组分饱和蒸汽压以及由其组成的二元混合物的汽-液平衡(VLE)数据,并分别用Antoine(安托尼)方程和NRTL热力学模型拟合了饱和蒸汽压和二元VLE的实验结果,得到了乙二醇和乙二醇二乙酸酯的二元相互作用参数。进一步测量了常压和温度为313.15～333.15 K条件下二元混合物的密度及表面张力,获得了该二元混合体系的摩尔体积、超额摩尔体积和表面热力学性质。得到的实验数据和拟合结果可为乙二醇酯化反应系统的设计和优化提供基础数据。     

HFO类工质立方型容积平移状态方程

为了更加准确地描述制冷工质纯组分的热力学行为,文中通过拟合HFO类制冷工质的热物性实验数据,回归得到立方型容积平移状态方程的2个可调参数,并将方程的2个可调参数普遍化为关于临界压缩因子的函数。对计算结果进行了分析讨论,分析立方型容积平移状态方程纯流体饱和液相密度和高压液体密度的计算精度。研究结果表明：与原始的PR状态方程和SRK状态方程相比,立方型容积平移状态方程对饱和液相密度和单相液体密度改进显著。以R1234ze(E)为例,验证了文中所建立的立方型容积平移状态方程。VTPR状态方程计算饱和液相密度的平均绝对相对偏差为1.42%,计算高压液相密度的平均绝对相对偏差为0.82%;VTSRK状态方程计算饱和液相密度的平均绝对相对偏差分别为3.58%,计算高压液相密度的平均相对偏差为2.00%。     

一组适合炼厂水蒸汽参数的快速计算方程

本文以IAPWS-IF97为基础,参考有关文献,提出一组水和水蒸汽热力性质计算的简明方程,包括饱和蒸汽压、饱和液密度、饱和汽密度、饱和液焓、饱和汽焓、汽化潜热6个方程,并以IAPW S-IF97的计算结果拟合了方程中的常数。所提出的6个方程,形式简单,使用方便,具有良好的计算精度,完全覆盖石化、炼油企业所用蒸汽参数范围。     

应用分子聚集理论计算金属熔体的热力学性质

首先导出聚集硬球分子模型状态方程,并应用该方程计算五种金属熔体饱和气的密度,取得满意的结果。还应用克拉贝龙方程,蒸汽压方程和状态方程计算了金属熔体的汽化潜热,所得结果与实验数据符合良好。     

甲基烯丙醇饱和蒸汽压的测定与关联

采用静态法测定了甲基烯丙醇在335.05~388.29 K温度区间的饱和蒸汽压数据,并用Antoine方程lnps=AB/(T+C)进行了关联,获得Antoine常数A、B、C分别为15.0499、3020.65和-98.10。Antoine方程计算得到的饱和蒸汽压值与实验数据吻合较好,平均相对误差为0.86%。通过Clausius-Clapeyron方程计算得到甲基烯丙醇在335.05~388.29 K范围内的平均摩尔蒸发热为46.47 kJ·mol-1。实验所得饱和蒸汽压方程对甲基烯丙醇的精馏分离过程设计具有重要意义。     

R1234yf+CO_2和R1234ze (E)+CO_2二元混合物的比容平移Soave-Redlich-Kwong方程

采用温度相关比容平移项的比容平移Soave-Redlich-Kwong(VTSRK)方程计算新工质R1234yf和R1234ze(E)的热力学性质以及两种物质与CO_2的二元混合物性质,混合物计算采用van der Waals混合规则,二元交互作用系数由密度数据拟合得到。对纯净物计算与专用状态方程进行对比,VTSRK方程比SRK方程显著改善了液相密度表征效果。对混合物的密度计算结果与实验数据进行对比,对于R1234yf+CO_2二元混合体系方程与实验数据相对均方根偏差为1.17%,对于R1234ze(E)+CO_2二元混合体系相对均方根偏差为0.82%。结果显示,采用温度相关比容平移项的VTSRK方程应用于R1234yf和R1234ze(E)纯流体以及R1234yf+CO_2和R1234ze(E)+CO_2密度性质计算,可获得较高精度。     

HFO-1336mzz(Z)环保制冷工质的PC-SAFT状态方程研究

以新型环保制冷工质HFO-1336mzz(Z)作为研究对象,采用链扰动统计缔合流体理论(PC-SAFT)状态方程,通过关联文献中的PVT数据,回归得到了HFO-1336mzz(Z)制冷工质的PC-SAFT状态方程参数。在此基础上,使用MATLAB软件编制了工质的PC-SAFT状态方程计算程序,得到了较为全面的HFO-1336mzz(Z)PVT数据。研究结果表明:PC-SAFT方程关联得到的饱和蒸汽压及饱和液体密度与文献值的平均相对偏差分别为0.40%和0.92%;同时,方程预测得到的压力及密度与文献值的平均相对偏差在超临界区分别为0.96%和1.35%,在液相区偏差分别为1.06%和1.67%。     

Improving the simplified‐perturbed‐hard‐chain theory equation of state using a new non‐attracting hard‐sphere equation

In this research a new simple non‐attracting hard‐sphere equation is introduced. The equation meets the ideal gas and close‐packed limits and is in accordance with computer simulation data with reasonable accuracy. When this equation is used with the simpli‐fied‐perturbed‐hard‐chain theory equation of state, improvements on the calculation of vapour pressure and saturated liquid density of pure compounds are observed. For 35 pure compounds of different classes, the averages of absolute error are 3.31% and 4.20% for the calculation of vapour pressure and saturated liquid density, respectively. The respected errors for the original equation of state are 3.53% and 4.96%, respectively. Moreover, the use of the new hard‐sphere equation in place of the Carnahan‐Starling equation in the simplified‐perturbed‐hard‐chain theory equation of state, does not have any appreciable effect on the prediction of K factors in VLE calculations.     

A practical equation of state for non‐spherical and asymmetric systems for application at high pressures. Part 1: Development of the pure component model

A practical, mathematically and computationally simple, equation of state (EOS) has been developed to accurately describe pure component phase behaviour of spherical and chain‐like molecules. The EOS consists of a newly developed hard sphere model and a perturbation term based on the Barker and Henderson approach using the Chen and Kreglewski intermolecular potential model and a double constrained summation as a mathematical expression thereof. The perturbed hard chain theory (PHCT) approach is used to extend the EOS to non‐spherical molecules. The EOS compares well with other more complex models such as the simplified perturbed hard chain theory (SPHCT) and statistically associating fluid theory (SAFT) models and will be extended to describe mixtures in Part 2 of this series. © 2011 Canadian Society for Chemical Engineering     

An analytical equation of state for water and alkanols

An analytical equation of state extended from statistical associating fluid theory (SAFT) is modified to describe the thermodynamic properties of fluids with high polarity such as water and alkanols up to the region close to the critical point. Five terms are used in the equation of state: the term for hard convex body, the term for dispersion energy, the term for the chain formation of hard convex body, the term for the change of the dispersion energy because of chain formation, and the term for dipole-dipole interaction. This equation of state is still called SAFT-CP (across critical points). Six fluids water, methanol, ethanol, 1-propanol, 1-butanol and 1-pentanol are used as examples. The new equation of state reproduces saturated pressures and densities in vapor-liquid equilibrium, critical properties (as temperature, pressure and density), and densities in the one-phase region with rational accuracies. The comparison of the calculated critical exponent β with the experimental one for methanol shows the improvement up to the region only with 20 K difference of temperature to the critical point. The result coincides with the estimation of the critical region on the basis of Ginzburg number and also with the available opinion that crossover methods and renormalization theories are necessary in the near-critical region.     

简化空穴理论状态方程在链状分子及有机溶剂液体中的应用

基于不完全晶体的热缺陷统计理论,将液体晶格中被占座席分率表示为对比温度的指数函数,推出了一个适用于聚合物,链状大分子及有机溶剂的液体状态方程。将此简化了的状态方程用于17种大分子链烃及10种常见的有机溶剂P-V-T计算,结果与实验值十分相符。与Simha和Somcynsky的空穴理论状态方程式相比较,计算大为简化且精度相当,易于应用至混合物体系。     

基于黏滞球模型的CPA状态方程应用于醇胺系统相平衡的计算

考虑到醇胺及其混合物中分子间存在缔合作用的事实,结合立方型PR状态方程,通过引入基于黏滞球模型(SSM)发展起来的缔合流体的分子热力学模型,建立了一个新的CPA(cubic-plus-association)状态方程,即CPA-SSM,并将方程应用到醇胺系统相平衡的计算中。通过关联对比温度0.55～0.90范围下醇胺流体的实验饱和蒸气压和液相体积得到了8种醇胺流体的分子参数。结果表明,CPA-SSM方程可满意地计算出醇胺饱和蒸气压和液体密度,总平均误差分别只有0.57%和1.80%。对醇胺混合物,无论是恒压还是恒温系统,只需引入一个与温度无关的可调参数,CPA-SSM方程即可满意关联二元系统的汽液平衡数据,并可进一步预测多元混合物的汽液平衡。     

利用正则配分函数计算实际流体的热力学性质及汽液平衡——(Ⅰ)纯流体的热力学性质

通过修改普遍化van der Waals正则配分函数的引力项,发展了一个修正的状态方程式.将表征分子间引力参数α修正为不仅依赖于温度而且与密度有关.用新的状态方程式计算纯气体、饱和蒸汽与饱和液体的压力与逸度系数的结果与实验结果符合较好.     

CALCULATION OF THERMODYNAMIC PROPERTIES OF REAL FLUIDS AND VAPOR-LIQUID EQUILIBRIA BY USING A CANONICAL PARTITION FUNCTION (Ⅰ) THERMODYNAMIC PROPERTIES OF PURE FLUIDS

The Anderson-Prausnitz equation of state has been improved by modifying the attractive term of the generalized van der Waals canonical partition function.In this modification, the parameter characterizing the intermolecular attractive forces is considered to depend not only on temperature but also on density.By this new equation of state the calculated results for pressure and fugacity coefficient of pure gases have slightly better accuracy than those by the original Anderson-Prausnitz equation, and those for saturated vapor pressure are in good agreement with observed results.     

SIMPLIFIED HARD-SPHERE AND HARD-SPHERE CHAIN EQUATIONS OF STATE FOR ENGINEERING APPLICATIONS

A simple hard-sphere equation of state is proposed. This hard-sphere equation is a ratio of second-order polynomials that meets the ideal gas and close-packed density limits. It predicts the compressibility of hard-sphere fluids at low and medium densities to within a degree of quality similar to the widely used Carnahan-Starling equation. In addition, the proposed equation performs better at high densities, particularly near the close-packed density. An expression is also derived to relate the site-site correlation function at contact for hard dimers with the site-site correlation function at contact for hard spheres. With this relationship, the thermodynamic perturbation-dimer theory (TPT-D) of hard-sphere chains is simplified. The new theory performs comparably with the TPT-D when the compressibility factors of hard-sphere chain fluids containing up to 201-mer are predicted, however, it has the advantages of both simplicity and accuracy. From a practical perspective, this theory can be used to construct equations of state for polymer solutions or fluid systems containing short- and long-chain molecules.     

SIMPLIFIED HARD-SPHERE AND HARD-SPHERE CHAIN EQUATIONS OF STATE FOR ENGINEERING APPLICATIONS

A simple hard-sphere equation of state is proposed. This hard-sphere equation is a ratio of second-order polynomials that meets the ideal gas and close-packed density limits. It predicts the compressibility of hard-sphere fluids at low and medium densities to within a degree of quality similar to the widely used Carnahan-Starling equation. In addition, the proposed equation performs better at high densities, particularly near the close-packed density. An expression is also derived to relate the site-site correlation function at contact for hard dimers with the site-site correlation function at contact for hard spheres. With this relationship, the thermodynamic perturbation-dimer theory (TPT-D) of hard-sphere chains is simplified. The new theory performs comparably with the TPT-D when the compressibility factors of hard-sphere chain fluids containing up to 201-mer are predicted, however, it has the advantages of both simplicity and accuracy. From a practical perspective, this theory can be used to construct equations of state for polymer solutions or fluid systems containing short- and long-chain molecules.