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Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
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Third Virial Coefficient for Air-Water Vapor Mixtures
R W Hyland1,2, E A Mason2
1Institute for Basic Standards, National Bureau of Standards, Washington, D.C. 20234.
Summary
This study estimates the third interaction virial coefficient for air-water vapor mixtures using molecular association. Results show this coefficient
Area of Science:
- Thermodynamics
- Physical Chemistry
- Atmospheric Science
Background:
- Understanding the equation of state for air-water vapor mixtures is crucial for atmospheric and thermodynamic applications.
- Accurate virial coefficients are essential for precise thermodynamic modeling.
- Previous estimations of interaction coefficients and pure component virial coefficients exist.
Purpose of the Study:
- To estimate the third interaction virial coefficient (C3) for air-water vapor mixtures.
- To provide a quantitative description of the equation of state for these mixtures.
- To assess the contribution of interaction virial coefficients to the compressibility factor.
Main Methods:
- An approximate method based on molecular association was employed.
- The estimation covered the temperature range of 0 to 100 °C.
- Results were validated against known coefficients and extrapolated for specific conditions.
Main Results:
- The third interaction virial coefficient (C3) for air-water vapor mixtures was estimated.
- The results are considered accurate within a factor of two.
- The combined contribution of C3 and another interaction coefficient (C3) to the compressibility factor is minimal (order of 10-4) up to 100 °C and 100 atm.
Conclusions:
- The estimated C3 allows for a complete third virial coefficient description of air-water vapor mixtures.
- The influence of interaction virial coefficients on the compressibility factor is negligible under typical atmospheric conditions.
- Extrapolation indicates an even smaller contribution at lower temperatures (-50 °C).
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