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ANSYS FLUENT will automatically include the terms needed to model mass transfer in all relevant
conservation equations. Another option to model mass transfer between phases is through the use of
user-defined sources and their inclusion in the relevant conservation equations. This approach is a
more involved but more powerful, allowing you to split the source terms according to a model of your
choice.
1. Momentum, energy, and turbulence are also transported with the mass that is transferred. ANSYS
FLUENT assumes that the reactants are mixed thoroughly before reacting together, thus the heat
and momentum transfer is based on this assumption. This assumption can be deactivated using a
text command. For more information, contact your ANSYS FLUENT support engineer.

Figure 24.2.8: The Evaporation-Condensation Model Dialog Box

8.5 Mixture Model

If you are using the mixture model, the conditions you need to specify for each type of zone are listed
below.
1. For an exhaust fan, outlet vent, or pressure outlet, there are no conditions to be specified for the
primary phase. For each secondary phase, you will need to set the volume fraction as a constant, a
profile, or a user-defined function (see the separate UDF Manual) and if applicable, the backflow
granular temperature. All other conditions are specified for the mixture.

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