二元真实气体混合物剩余焓和剩余熵的计算

The Calculations of Residual Enthalpy and Residual Entropy for a Binary Mixture of Real Gases at Low to Moderate Pressures

混合物流体热力学性质的计算是化工热力学中的一类重要计算。但现有教材中没有给出关于混合物剩余焓和剩余熵的计算公式,缺失了流体热力学性质计算的系统性。本文通过纯气体的剩余焓和剩余熵的计算公式,采用Prausnitz混合规则或Kay混合规则,推导出R-K方程、virial方程,以及普遍化关联法计算二元真实气体混合物剩余焓和剩余熵的公式,并用于具体实例的计算。结果表明,在中、低压下,采用所推导出的三种方法计算二元真实气体混合物剩余焓和剩余熵时,能够得到比较相近的结果,这三种方法是正确可靠的;在高压下,R-K方程和普遍化关联法仍可采用,而virial方程则不再适用。每种方法计算过程繁简不一,但步骤简捷明了,利于学生更好地理解混合物热力学性质的计算过程。

The calculations of thermodynamic properties of mixtures are important in Chemical Engineering Thermodynamics.However,the present textbook doesn＇t give any description on the calculations of residual enthalpy and residual entropy for a real gas mixture,resulting in the incompleteness in the calculation methodology.In this paper,we derived residual enthalpy and residual entropy calculation formulas for a binary mixture of real gases at low to moderate pressures by R-K equation,virial equation and generalized correlations based on those for a pure gas,with Prausnitz mixing rule or Kay rule.Furthermore,the derived formulas were applied to an example.The results show that at low to moderate pressures,the approximate results can be obtained by these three derived methods showing that they are correct and reliable.When to high pressure,R-K equation and generalized correlations are still available,while virial equation is not.Although these three methods are complex or simple for use,they enable the calculation process simple and intuitive,and help students to understand the calculation procedures better.