activity_coefficients

class thermosteam.equilibrium.activity_coefficients.ActivityCoefficients

Abstract class for the estimation of activity coefficients. Non-abstract subclasses should implement the following methods:

__init__(self, chemicals: Iterable[Chemicals]):

Should use pure component data from chemicals to setup future calculations of activity coefficients.

__call__(self, x: 1d array, T: float):

Should accept an array of liquid molar compositions x, and temperature T (in Kelvin), and return an array of activity coefficients. Note that the molar compositions must be in the same order as the chemicals defined when creating the ActivityCoefficients object.

property chemicals

tuple[Chemical] All chemicals involved in the calculation of activity coefficients.

class thermosteam.equilibrium.activity_coefficients.IdealActivityCoefficients(chemicals)

Create an IdealActivityCoefficients object that estimates all activity coefficients to be 1 when called with a composition and a temperature (K).

Parameters

chemicals (Iterable[Chemical]) –

__call__(xs, T)

Call self as a function.

class thermosteam.equilibrium.activity_coefficients.GroupActivityCoefficients(chemicals)

Abstract class for the estimation of activity coefficients using group contribution methods.

Parameters

chemicals (Iterable[Chemical]) –

activity_coefficients(x, T)

Return activity coefficients of chemicals with defined functional groups.

Parameters

• x (array_like) – Molar fractions

• T (float) – Temperature [K]

__call__(x, T)

Return activity coefficients.

Parameters

• x (array_like) – Molar fractions

• T (float) – Temperature [K]

Notes

Activity coefficients of chemicals with missing groups are default to 1.

class thermosteam.equilibrium.activity_coefficients.DortmundActivityCoefficients(chemicals)

Create a DortmundActivityCoefficients that estimates activity coefficients using the Dortmund UNIFAC group contribution method when called with a composition and a temperature (K).

Parameters

chemicals (Iterable[Chemical]) –

Examples

>>> import thermosteam as tmo
>>> chemicals = tmo.Chemicals(['Water', 'Ethanol'], cache=True)
>>> Gamma = tmo.equilibrium.DortmundActivityCoefficients(chemicals)
>>> composition = [0.5, 0.5]
>>> T = 350.
>>> Gamma(composition, T)
array([1.475, 1.242])

>>> chemicals = tmo.Chemicals(['Dodecane', 'Tridecane'], cache=True)
>>> Gamma = tmo.equilibrium.DortmundActivityCoefficients(chemicals)
>>> # Note how both hydrocarbons have similar lenghts and structure,
>>> # so activities should be very close
>>> Gamma([0.5, 0.5], 350.)
array([1., 1.])

>>> chemicals = tmo.Chemicals(['Water', 'O2'], cache=True)
>>> Gamma = tmo.equilibrium.DortmundActivityCoefficients(chemicals)
>>> # The following warning is issued because O2 does not have Dortmund groups
>>> # RuntimeWarning: O2 has no defined Dortmund groups;
>>> # functional group interactions are ignored
>>> Gamma([0.5, 0.5], 350.)
array([1., 1.])

class thermosteam.equilibrium.activity_coefficients.UNIFACActivityCoefficients(chemicals)

Create a UNIFACActivityCoefficients that estimates activity coefficients using the UNIFAC group contribution method when called with a composition and a temperature (K).

Parameters

chemicals (Iterable[Chemical]) –