Enthalpy

Ideal

In this model the enthalpy is computed from the ideal gas contribution:

For liquids, the latent heat of vaporization is subtracted from the ideal gas contribution:

Excess

This model includes the ideal enthalpy as above. In addition to that, excess enthalpy is included:

Prausnitz

The liquid enthalpy for the Prausnitz model is consistent with the liquid reference fugacity of the Prausnitz model fugacity calculations:

EOS

This model includes the ideal vapor enthalpy as above. In addition to that, the temperature derivative of the fugacity coefficients from the selected equation of state is subtracted from the ideal part:

Pressure and temperature derivatives are determined by perturbation.

Solids

For solids, currently the only enthalpy model is ideal enthalpy:

Here, the solid phase heat capacity is used (configured per compound). The solid state reference enthalpy at reference temperature is zero for solid-only compounds; these compounds have their reference state in the solid phase. This means the heat of formation - H_form as used below in enthalpyF - must also be at the solid reference state. Other solids are currently not supported.

Overall

The overall enthalpy can be calculated from summation over the available phases, taking into account the phase fractions.

EnthalpyF

EnthalpyF, as opposed to enthalpy, contains the enthalpy of formation:

For EnthalpyF, the same models are available as for Enthalpy.

EnthalpyNF

EnthalpyNF is defined as enthalpy for which enthalpy of formation is not included. In TEA it can be calculated and is treated synonymous for Enthalpy.

Excess Enthalpy

From activity coefficient

The only available excess enthalpy model is for the liquid phase: by calculation from the temperature derivatives of the activity coefficient model.

Pressure and temperature derivatives are determined by perturbation.