### 1.14.3. Specification of Secondary Fluxes

Strictly speaking, it is necessary for you to specify only secondary fluxes for incoming boundary mass sources. For this model of wall condensation, the corresponding boundary mass sources are outgoing. The solver implementation of the wall condensation model exploits the boundary mass source machinery. All secondary fluxes are computed using the local solution values of variables, with the single exception of component mass sources to the mass fraction equations. Consequently, for this model, all secondary source information is automatically included.

It is possible in principal to define other boundary mass sources in addition to the condensation sinks, provided that they are consistent with the internal options used for the wall condensation term. However, in the current implementation, additional mass sources on wall condensation boundaries are disallowed.

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