Gas mixture

Use the GasMixture class to calculate properties of a gas mixture.

class chemics.GasMixture(gases, mole_fractions)[source]

Gas mixture class.

Parameters:

  • gases (list of Gas objects) – Gas objects representing each component of the gas mixture.

  • mole_fractions (list) – Mole fraction of each gas component.

Variables:

  • molecular_weights (list of float) – Molecular weight of each gas component in g/mol.

  • viscosities (list of float) – Viscosity of each gas component in microPoise (μP).

  • mole_fractions (list of float) – Mole fraction of each gas component.

Raises:

ValueError – If sum of mole fractions does not equal 1.

molecular_weight()[source]

Calculate molecular weight of the gas mixture as a weighted mean.

Returns:

mw_mixture (float) – Molecular weight of the gas mixture in g/mol.

Examples

>>> gas1 = cm.Gas('H2', 773)
>>> gas2 = cm.Gas('N2', 773)
>>> gas_mixture = cm.GasMixture([gas1, gas2], [0.8, 0.2])
>>> gas_mixture.molecular_weight()
7.2156...
viscosity(method='graham')[source]

Gas mixture viscosity.

Calculate viscosity of the gas mixture using Graham’s method [1] or the Herning and Zipperer method [2]. For the Graham method, Equation 1 from the Davidson report [3] is used

\[\mu_{mix} = \sum (x_i \cdot \mu_i)\]

where \(\mu_{mix}\) is viscosity of the gas mixture, \(x_i\) is mole fraction [-] of each component, and \(\mu_i\) is gas viscosity of each component. For the Herning and Zipperer method, Equation 1 from the Davidson report is used

\[\mu_{mix} = \frac{\sum (\mu_i \cdot x_i \cdot \sqrt{MW_i})}{\sum (x_i \cdot \sqrt{MW_i})}\]

where \(\mu_{mix}\) is viscosity of the gas mixture, \(x_i\) is mole fraction [-] of each component, \(\mu_i\) is gas viscosity of each component, and \(MW_i\) is the molecular weight [g/mol] of each gas component.

Parameters:

method (str) – Method for calculating the gas mixture viscosity, choose graham or herning. Default value is graham.

Returns:

mu_mixture (float) – Viscosity of the gas mixture in units of microPoise (μP).

Examples

>>> gas1 = cm.Gas('H2', 773)
>>> gas2 = cm.Gas('N2', 773)
>>> gas_mixture = cm.GasMixture([gas1, gas2], [0.85, 0.15])
>>> gas_mixture.viscosity()
207.34...

>>> gas1 = cm.Gas('H2', 773)
>>> gas2 = cm.Gas('N2', 773)
>>> gas_mixture = cm.GasMixture([gas1, gas2], [0.85, 0.15])
>>> gas_mixture.viscosity(method='herning')
252.78...

References