Sun Xiaoyan, Fang Yao, Zhao Wenying, Xiang Shuguang
Faculty of Chemical Engineering, Qingdao University of Science & Technology, Qingdao 266042, People's Republic of China.
Faculty of Chemistry and Chemical Engineering, Qilu Normal University, Jinan 250200, People's Republic of China.
ACS Omega. 2022 Feb 4;7(6):5332-5339. doi: 10.1021/acsomega.1c06519. eCollection 2022 Feb 15.
The alpha function is an important part of the attractive term of cubic equation of state (EoS), which affected the predictive accuracy of thermodynamic properties. In this paper, four new alpha functions (Alpha Function-1 to Alpha Function-4) were proposed for the Peng-Robinson (PR) EoS. The proposed alpha functions and their derivatives satisfied the requirements of the thermodynamic consistency test. The four alpha functions with PR EoS were used to predict the thermodynamic properties of 11 kinds of compounds, the average relative deviation (ARD) of Alpha Function-1 and Alpha Function-2 for the prediction of vapor pressures was 0.57%, and the ARDs of Alpha Function-3 and Alpha Function-4 were 0.44 and 0.38%, respectively. The ARDs of Alpha Function-4 for the estimation of enthalpy of vaporization, liquid volume, and liquid isobaric heat capacity of seven kinds of compounds were 1.46, 7.54, and 7.59%, respectively. The proposed three-parameter alpha functions were more accurate than the two-parameter function for the prediction the vapor pressure and enthalpy of vaporization of pure compounds. However, any alpha function used in the attractive term of PR EoS had great deviations for the estimation of liquid volume and isobaric heat capacity.
α函数是立方型状态方程（EoS）吸引项的重要组成部分，它影响热力学性质的预测精度。本文针对Peng-Robinson（PR）状态方程提出了四个新的α函数（α函数-1至α函数-4）。所提出的α函数及其导数满足热力学一致性检验的要求。将这四个α函数与PR状态方程一起用于预测11种化合物的热力学性质，α函数-1和α函数-2预测蒸气压的平均相对偏差（ARD）为0.57%，α函数-3和α函数-4的ARD分别为0.44%和0.38%。α函数-4估算七种化合物汽化焓、液体体积和液体等压热容的ARD分别为1.46%、7.54%和7.59%。所提出的三参数α函数在预测纯化合物蒸气压和汽化焓方面比两参数函数更准确。然而，PR状态方程吸引项中使用的任何α函数在估算液体体积和等压热容方面都有很大偏差。
