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### Diffusion mass transfer in a stationary medium

The governing equations for diffusion mass transfer are [29]

(113) |

and

(114) |

where

(115) |

and

(116) |

In these equations is the mass flux of species A, is the mass diffusivity, is the mass fraction of species A and is the density of species A. Furthermore, is the rate of increase of the mass of species A per unit volume of the mixture. Another way of formulating this is:

(117) |

and

(118) |

where

(119) |

and

(120) |

Here, is the molar flux of species A, is the mass diffusivity, is the mole fraction of species A and is the molar concentration of species A. Furthermore, is the rate of increase of the molar concentration of species A.

The resulting equation now reads

(121) |

or

(122) |

If and are constant, these equations reduce to:

(123) |

or

(124) |

Accordingly, by comparison with the heat equation, the correspondence in Table (15) arises.

**Next:**Aerodynamic Networks

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**Previous:**Stationary groundwater flow

**Contents**guido dhondt 2012-10-06