基于改进的SRK方程计算碱金属的热力学性质

摘要

基于SRK方程,通过对Na、K、Rb、Cs的PVT数据非线性拟合,提出了α函数改进形式,得到了k1、k2参数,与对应元素偏心因子关联获得碱金属的α函数,改进后的α函数值与PVT数据拟合得到的α函数值平均相对偏差为0.52％.通过改进的SRK方程求解了碱金属气体在不同温度压力下的摩尔体积,以及600～3 000 K温度范围内不同压力(1～1 000k Pa)下的压缩因子,与文献报道的压缩因子比较,平均绝对偏差小于4.4％.此外,还计算了碱金属气体在600～3 000 K温度范围的第二维里系数,与文献值吻合较好.改进后的SRK方程可以计算碱金属气体的热力学性质,并能为其他金属气体热力学性质计算提供方法指导.%The improved form of α function is proposed by nonlinearly fitting of the PVT data of Na, K, Rb and Cs based on the SRK equation.The k1 and k2 parameters are obtained, and the α function of the alkali metals is obtained in association with the acentric factor.The average relative deviation of the α-function values obtained by fitting the PVT data with the modified α function values is 0.52％.Through the improved SRK equation, the molar volumes of alkali metals gas are calculated under different temperature and pressure.The compressibility factors at different pressures (1-1 000 k Pa) in the temperature range of 600-3 000 K are calculated and compared with the compressibility factor reported in the literature, the average absolute deviation is less than 4.4％.In addition, the second virial coefficient of alkali metals gas in the temperature range from 600 K to 3 000 K is calculated, which is in good agreement with the literature values.The improved SRK equation can calculate the thermodynamic properties of alkali metals gas and provide guidance for the calculation of the thermodynamic properties of other metal gases.