Fugacity

EOS

Fugacities are calculated from the selected equation of state. This model is recommended for mixtures of hydrocarbons and light gases (hydrogen, carbon dioxide, nitrogen, etc.) at low and high pressures. It is not recommended for non-ideal chemical mixtures at low pressures.

From Activity Coefficient

Liquid fugacity is calculated from

where PF_i is the Poynting correction for compound i, P_i^* is the saturated vapor pressure for compound i and φ_i^* is the fugacity coefficient of the vapor phase for compound i at liquid composition and liquid temperature and saturated vapor pressure.

This option should be used when dealing with non-ideal fluid mixtures. It is not suitable for high pressures.

DECHEMA

Liquid fugacity is calculated from

This is a simplified form of the complete "From Activity Coefficient" model in which the Poynting correction factor is assumed equal to unity.

This is the form of the K-value model used in the DECHEMA compilations of equilibrium data when used with the Ideal gas equation of state and the Antoine equation for vapor pressure.

Prausnitz

Liquid fugacity is calculated from

The saturated vapor fugacity, Poynting factor and vapor pressure are all combined into a liquid reference fugacity f_i⁰. Values of the reference fugacity are calculated using a temperature dependent function for which the shape is equal to the Extended Antoine equation:

The parameters A through G must be supplied by the user; this can be done by editing the compound in the TEA package configuration dialog. For a number of chemicals, the parameter values are given by the data file prausnitz_e_antoine.lib in the data sub folder of the COCO installation folder. Parameter values for the compounds in this file will be automatically loaded.