立方型状态方程在R134a热力性质计算中的研究

比较了SRK方程,PR方程,童景山方程和苏志军方程4个通用立方型状态方程用于R134a饱和气、液的体积计算准确度。计算表明,在-50~90℃的范围内,童景山方程的计算偏差最小,饱和气与饱和液体积的计算值与文献值的平均偏差为1.63%和4.12%;PR方程的计算平均偏差为1.90%和4.76%;SRK方程平均偏差最大,为3.35%和18.64%;苏志军方程的计算偏差与PR方程基本相同,为2.00%和5.21%。结果表明,对于R134a来说,童景山方程的计算结果更加精确,更适合用于R134a热力性质的工程计算。     

二氧化碳混合工质临界参数计算模型对比研究

二氧化碳(CO₂)混合工质是具有应用潜力的动力循环工质,临界参数作为CO₂混合工质的关键基础热物性,对其进行准确地计算和预测具有重要意义。采用4种不同类型的计算模型,分别针对CO₂+HFC、CO₂+HFO和CO₂+HC三类二元混合工质的临界温度和临界压力进行了推算,并与公开发表的实验数据和REFPROP数据库计算结果进行对比,分析讨论了各种计算方法对各类CO₂混合工质的适用性。结果表明,Li方法形式简单,混合物临界温度的计算式仅与纯质组分的临界温度及临界体积有关,可用于CO₂+HFC和CO₂+HFO混合工质临界温度的快速推算。对于CO₂+HC混合工质,RK方法计算偏差最小,该类混合物临界参数实验数据点数和套数较多,因此可直接通过RK方法回归得到关联式进行应用。     

基于多种状态方程模型的冷凝法油气回收对比

冷凝法回收油气过程的模拟计算采用何种状态方程尚无定论,建立油气混合物相平衡模型和组分热物理参数模型,进行油气回收过程模拟的对比。相平衡模型主要由状态方程、物质的量平衡方程、热力学平衡条件方程和模型迭代步骤组成,状态方程包括SRK方程、PR方程、TJS方程和理想气体方程。模拟结果表明：状态方程选用SRK、PR和TJS方程,经实验数据验证,满足精度要求;将油气视为理想气体时,计算结果与实际气体状态方程的模拟结果相差较大,冷凝温度越高,偏差越大,油气混合物在冷凝过程中不能视为理想气体;SRK、PR、TJS和Aspen Plus的模拟结果比较一致,相平衡计算应优先选用SRK或TJS方程。     

基于多种状态方程模型的冷凝法油气回收对比

冷凝法回收油气过程的模拟计算采用何种状态方程尚无定论,建立油气混合物相平衡模型和组分热物理参数模型,进行油气回收过程模拟的对比。相平衡模型主要由状态方程、物质的量平衡方程、热力学平衡条件方程和模型迭代步骤组成,状态方程包括SRK方程、PR方程、TJS方程和理想气体方程。模拟结果表明:状态方程选用SRK、PR和TJS方程,经实验数据验证,满足精度要求;将油气视为理想气体时,计算结果与实际气体状态方程的模拟结果相差较大,冷凝温度越高,偏差越大,油气混合物在冷凝过程中不能视为理想气体;SRK、PR、TJS和Aspen Plus的模拟结果比较一致,相平衡计算应优先选用SRK或TJS方程。     

基于PR状态方程的二元体系临界性质计算中不同混合规则对比

基于PR状态方程,结合四种不同混合规则,利用Heidemann和Khalil的临界性质计算方法,关联了二十一种不同二元体系的临界温度并预测了其临界压力,其中包括非极性、极性和缔合三类体系.对临界温度的关联结果表明,四种混合规则对所有体系均适用.对临界压力的预测结果表明,四种混合规则中van der及Waals-1 Panagiotopoulos-Reid混合规则对非极性-极性(四偶极)体系的估算精度高,而van der Waals-2和Sadus van der Waals-2混合规则更适用于非极性-非极性体系及极性-极性(四偶极)体系.对于缔合体系,随着组分缔合能力的增强,四种混合规则的预测误差均增大,除含1-丁醇及苯组分的体系外有待于寻找更合适的状态方程及混合规则.     

运用立方型方程预测超高压下气体的压缩因子

通过vdW方程、RK方程、SRK方程和PR方程预测氮气、二氧化碳和甲烷气体在超高压情况下的压缩因子,此外进一步运用PR方程预测空气在压强为1000~2000 MPa的压缩因子,并与文献值进行比较,发现PR方程在超高压下计算气体压缩因子时有较宽的适应范围和较好的精度。     

R1234yf+CO2和R1234ze (E)+CO2二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CO₂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+CO₂二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）+CO₂二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+CO₂和R1234ze（E）+CO₂密度性质计算,可获得较高精度。     

PR方程结合vdW混合法则推算二元及三元HFC/HC混合工质

以PR方程结合vdW混合法则,利用建立的二元相互作用系数kij差值关联模型,对11组二元HFC/HC混合工质及5组三元HFC/HC混合工质（HFC32 / HFC125 / HFC134a,HC290 / HC600a / HFC32,HFC125 / HFC143a / HFC134a,HFC32 / HC290 / HFC227ea,HFC32 / HFC125 / HC290）气液相平衡性质进行了推算,并与文献实验数据比较,对压力计算的平均相对偏差分别为2.225%、8.317%、1.433%、0.403%、1.71%,对气相组分计算的平均绝对偏差分别为0.0086、0.0132、0.0054、0.0071、0.0089。结果表明该方法可用于推算二元及三元HFC/HC混合工质气液相平衡性质。     

无限接近临界点的克拉佩龙方程和临界参数计算

本文将无限接近临界状态的克拉佩龙（Ｂ．Ｐ．Ｅ．Ｃｌａｐｅｙｒｏｎ）方程与安托因（Ｃ．Ａｎｔｏｉｎｅ）公式相结合，导出了纯物质的临界温度计算公式，并以有机同系物直链烷烃为例，计算了乙烷～庚烷的临界参数（临界温度Ｔ_ｃ、临界压力Ｐ_ｃ和临界体积Ｖ_（ｍ，ｃ））。     

含HFO二元混合工质汽液相平衡性质研究

为了提高环保替代混合制冷工质相平衡数据的计算精度,文中收集了公开发表的7种HFOs/HFCs及6种HFOs/HCs 2类二元混合工质的气液相平衡性质实验数据,分别采用PR方程+VDW混合法则、PR方程+MHV1混合法则+Wilson模型对2类混合工质的气液相平衡性质进行了非线性优化,结果表明:对于HFOs/HFCs,PR+MHV1+Wilson模型计算值与实验结果的压力平均相对偏差为0. 28%,汽相组分的平均绝对偏差为0. 003 5,PR+VDW模型的结果分别为0. 30%和0. 003 6;对于HFOs/HCs,PR+MHV1+Wilson模型计算值与实验结果的压力平均相对偏差为0. 25%,汽相组分的平均绝对偏差为0. 003 7,PR+VDW模型的结果分别为0. 55%和0. 004 8。可见:相比于PR+VDW模型,PR+MHV1+Wilson模型对HFOs/HFCs混合工质的汽液相平衡性质计算精度提升有限,对HFOs/HCs类工质则可显著提升计算精度。     

利用扩展Tao-Mason状态方程预测天然气混合物容积特性(p-V-T)

A statistical-mechanical-based equation of state(EOS)for pure substances,the Tao-Mason equation of state,is successfully extended to prediction of the(p-v-T)properties of fourteen natural gas mixtures at temperatures from 225 K to 483 K and pressures up to 60.5 MPa.This work shows that the Tao-Mason equation of state for multicomponent natural gas is predictable with minimal input information,namely critical temperature,critical pressure,and the Pitzer acentric factor.The calculated results agree well with the experimental data.From a total of 963 data of density and 330 data of compressibility factor for natural gases examined in this work,the average absolute deviations(AAD)are 1.704%and 1.344%,respectively.The present EOS is further assessed through the comparisons with Peng-Robinson(PR)equation of state.For the all of mixtures Tao-Mason(TM)EOS outperforms the PR EOS.     

THE EFFECT OF VARIOUS TYPES OF EQUATIONS OF STATE ON DRIVING FORCE CALCULATION AND GAS CONSUMPTION PREDICTION IN SIMPLE AND DOUBLE HYDRATE FORMATION WITH OR WITHOUT THE PRESENCE OF KINETIC INHIBITORS IN BATCH SYSTEMS

This article compares the effects of using various types of equations of state (Peng-Robinson, PR; Soave-Redlich-Kwong, SRK; Esmaeilzadeh-Roshanfekr, ER; Patel-Teja, PT; and Valderrama-Patel-Teja, VPT) on the calculated driving force and rate of gas consumption based on the Kashchiev model in simple and double-gas hydrate formation for methane, ethane, and their mixtures with 1130 experimental published data points with or without the presence of kinetic inhibitors at various pressures and temperatures. For the prediction of gas consumption rate in double-gas hydrate formation, the rate equation based on the Kashchiev model for simple gas hydrate formation was developed using the calculation of gas mole fraction in hydrate phase and then prediction of gas hydrate formation rate for each component in gaseous mixture. The total average absolute deviation was found to be 8.72%, 10.34%, 8.84%, 11.04%, and 14.16% for the PR, ER, SRK, VPT, and PT equations of state for calculating gas consumption in simple and double hydrate formation, respectively.     

应用PSRK状态方程预测高压汽液平衡

为预测高压汽液平衡,将过量吉布斯自由能混合规则和UNIFAC活度系数模型与SRK状态方程相结合,建立基团贡献状态方程PSRK。利用该状态方程对5个体系在不同压力和温度下的汽液平衡数据进行了关联实验测定的汽相压力和汽相组成与计算结果相比所得的相对平均偏差分别为2．16％和1．01％。结果表明,PSRK状态方程可以成功地预测高压下汽液平衡,其精度高于MHV1和MHV2模型。     

Statistical mechanics and artificial intelligence to model the thermodynamic properties of pure and mixture of ionic liquids

In this paper, the volumetric properties of pure and mixture of ionic liquids are predicted using the developed statistical mechanical equation of state in different temperatures, pressures and mole fractions. The temperature dependent parameters of the equation of state have been calculated using corresponding state correlation based on only the density at 298.15 K as scaling constants. The obtained mean of deviations of modified equation of state for density of al pure ionic liquids for 1662 data points was 0.25%. In addition, the performance of the arti-ficial neural network (ANN) with principle component analysis (PCA) based on back propagation training with 28 neurons in hidden layer for predicting of behavior of binary mixtures of ionic liquids was investigated. The AADs of a col ection of 568 data points for al binary systems using the EOS and the ANN at various temperatures and mole fractions are 1.03%and 0.68%, respectively. Moreover, the excess molar volume of all binary mixtures is predicted using obtained densities of EOS and ANN, and the results show that these properties have good agree-ment with literature.     

Orientation effect on sign and magnitude of excess thermodynamic functions of non electrolyte solutions at different temperatures (303.15 K, 308.15 K,and 313.15K)

Experimental values of the density and viscosity have been measured for binary mixtures of N-ethylaniline with isomeric butanols (1-butanol, 2-butanol, 2-methyl-1-propanol and 2-methyl-2-propanol) at 303.15, 308.15 and 313.15 K over the entire mole fraction range. These data, the excess molar volumes, and deviation viscosity for the binary systems at the above-mentioned temperatures were calculated and fitted to Redlich-Kister equation to determine the fitting parameters and the root-mean-square deviations. The excess molar volumes, deviation viscosity and excess Gibbs energy of activation of viscous flow have been analyzed in terms of acid-base interactions, hydrogen bond, and dipole-dipole interaction between unlike molecules. The results obtained for dynamic viscosity of binary mixtures were used to test the semi-empirical relations of Grunberg-Nissan, Katti-Chaudhri, and Hind et al. equations.     

Critical properties and acentric factors of ionic liquids

Since most ionic liquids (ILs) decompose before reaching their critical state, the experimental measurement of their critical properties are not possible. In this study, the critical temperatures, critical pressures and acentric factors of ten commonly investigated ILs were determined by making an optimum fit of the calculated vapor-liquid equilibrium data of binary mixtures of CO₂+IL to the experimental values found in literature. For this purpose, the Peng-Robinson equation of state (PR EoS) and the differential evolution optimization method were used. The ILs considered were 1-ethyl-3-methylimidazolium hexafluorophosphate ([emim][PF₆]), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([emim][Tf₂N]), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]), 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([bmim][Tf₂N]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim][BF₄]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF₆]), 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([hmim][Tf₂N]), 1-octyl-3-methylimidazolium tetrafluoroborate ([omim][BF₄]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([omim][PF₆]). To evaluate the ability of the determined parameters in predicting the phase behavior of systems other than the systems that were used for parameter optimization, both sets of parameters obtained in this work and that of Valderrama et al. were used to predict bubble-point pressures of CHF₃+[bmim][PF₆] (by using the PR EoS and the Soave-Redlich-Kwong equation of state. The bubble-point pressures of CO₂+IL systems optimized in this study by the PR EoS were also determined using the Soave-Redlich-Kwong equation of state (SRK EoS). In addition, liquid densities of pure ILs were predicted using a generalized correlation proposed by Valderrama and Abu-Shark. In all cases, the various predicted properties of these ten ILs, were in better agreement with the experimental data, using the critical properties and acentric factor obtained in this study, compared to the values suggested by Valderrama et al.     

SRK方程α的改进及其在汽-液相平衡预测中的应用

Based on results of saturated vapor pressures of pure substances calculated by SRK equation of state, the factor a in attractive pressure term was modified. Vapor-liquid equilibria of mixtures were calculated by original and modified SRK equation of state combined with MHV1 mixing rule and UNIFAC model, respectively. For 1447 saturated pressure points of 37 substance including alkanes; organics containing chlorine, fluorine, and oxygen; inorganic gases and water, the original SRK equation of state predicted pressure with an average deviation of 2.521% and modified one 1.673%. Binary vapor-liquid equilibria of alcohols containing mixtures and water containing mixtures also indicated that the SRK equation of state with the modified a had a better precision than that with the original one.     

SRK方程α的改进及其在汽-液相平衡预测中的应用

Based on results of saturated vapor pressures of pure substances calculated by SRK equation of state,the factor α in attractive pressure term was modified. Vapor-liquid equilibria of mixtures were calculated by original and modified SRK equation of state combined with MHV1 mixing rule and UNIFAC model, respectively. For 1447 saturated pressure points of 37 substance including alkanes; organics containing chlorine, fluorine, and oxygen; inorganic gases and water, the original SRK equation of state predicted pressure with an average deviation of 2.521% and modified one 1.673%. Binary vapor-liquid equilibria of alcohols containing mixtures and water containing mixtures also indicated that the SRK equation of state with the modified α had a better precision than that with the original one.     

Excess molar volume of acetone, water and ethylene glycol mixture

The excess molar volumes for binary acetone+ethylene glycol and acetone+water mixtures whose components represent strong polarity and association were measured at temperatures 283.15 K and 293.15 K, by using a vibrating tube densitometer. Those of ternary mixtures composed of each component were also obtained at the same temperatures and compared with the calculated values from regression by utilizing the Redlich-Kister polynomial equation.     

Equation of state modeling of high-pressure, high-temperature hydrocarbon density data

Experimental densities are reported for n-pentane, n-octane, cyclooctane, 2,2,4-trimethylpentane, n-decane, and toluene to ∼280 MPa and ∼250 °C. These densities are in good agreement with available literature data that typically cover lower pressure and temperature ranges than those reported here. The data are modeled with the Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) cubic equations, the temperature-dependent, volume-translated SRK equation, the temperature- and density-dependent SRK equation, and the SAFT and PC-SAFT equations. Mean absolute percentage deviation (MAPD) values between densities calculated with the PR equation and literature data are 4.55 for n-pentane, 2.91 for n-octane, 3.68 for cyclooctane, 3.98 for 2,2,4-trimethylpentane, 5.58 for n-decane, and 1.99 for toluene. With the exception of 2,2,4-trimethylpentane, these MAPD values are substantially better than those obtained with the SRK and modified SRK equations. Although both SAFT-based models have MAPD values significantly lower than those with the PR equation, the PC-SAFT equation provides the lowest MAPD values.