MH状态方程使用DDLC混合规则计算混合物临界轨迹

Calculation of Critical Loci of Mixtures by MH Equation of State with DDLC Mixing Rule

一、引 言状态方程能否精确地描述流体混合物热力学性质,建立合适的混合规则是一个重要因素.近十年来,许多研究者把局部组成概念引入立方型状态方程,建立了与密度有关的局部组成(DDLC)混合规则,将两类重要的热力学模型——状态方程和活度系数方程联系起来,大大地改善了状态方程应用于高密度区时的柔软性,改进了状态方程描述极性一非极性、含超临界组分等高度非对称体系的精确度.作者将局部组成概念引入多参数的MH状态方程,椎导了MH方程的DDLC混合规则,用于计算高压汽液平衡和二元混合物临界轨迹.本文将介绍后者的计算情况.

The DDLC mixing rule has been developed for MH equation of state on the basis of two-fluid theory and the local mole fraction expression of a generalized NRTL model. It can be used to correlate the properties of most fluids under high pressure. The critical loci of 7 binary hydrocarbon mixtures and 17 typical binary systems, including polar-polar and nonpolar-polar system, are calculated by using the new mixing rule and the criteria for the critical point of a mixture suggested by Heidemann and Khalil. The accuracy is better than or comparable to commonly used cubic equation of state, and the improvement of evaluating Vc is most remarkable.