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An equation of state for gas mixtures
Author(s) -
Othmer Donald F.,
Chen Hung Tsung
Publication year - 1966
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690120318
Subject(s) - compressibility factor , thermodynamics , compressibility , chemistry , equation of state , volume (thermodynamics) , reduced properties , function (biology) , constant (computer programming) , physics , evolutionary biology , computer science , biology , programming language
A pressure‐volume‐temperature equation for mixtures of two or more gases has been developed using the “reference substance” technique of comparing the properties of one substance with those of a standard under the same conditions. The compressibility factor is a function of temperature and pressure, with the variation from one substance to another being determined by the forces of attraction and repulsion between molecules. Thus, if the Lennard‐Jones 6‐12 potential function is used to describe the molecular interaction, the change in the compressiblity function reflects the different force constants, which in turn are functions of the critical constants. A mixture of gases is assumed to have the same thermodynamic properties as some hypothetical or pseudo gas which would have the same force constants existing between each pair of molecules in the mixture. The force constants of the pseudo gas may be evaluated from pseudo critical constants, which may be evaluated from the critical constants of individual components of the mixture. With the resultant force constants, there can be calculated the ratio of the compressibility factors of the gas mixture to those of a pure gas, nitrogen, taken as a reference substance, all values taken at the same reduced temperature and pressure. The compressibility factor of the mixture may be calculated from this ratio and the compressibility factor of the reference substance; and the PVT relations are immediately determinable. A comprehensive survey of the literature for PVT data of gas mixtures was made. More than 1,000 experimental values of PVT data for thirty‐four binary systems and four ternary systems have been studied. The proposed method showed an average deviation from experimental data, representing all published work, of 2.3%.