KNOWN ISSUE: Mass transfer rates may be incorrect for evaporating wall particles (Class 3 Error)

The mass transfer rate of evaporating wall particles is computed using an incorrect transfer coefficient.

The mass transfer coefficient has the dimension [kg s^-1 m^-2] and needs to be scaled with a reference area before it can be used in the particle tracking calculation. The scaling is done correctly for heat transfer (where a transfer coefficient is also used) but not for the mass transfer. This could cause severe convergence problems (the coefficient might be too large by several orders of magnitude) and incorrect results.

No workaround is currently available.

For some cases, it may be possible to avoid the problem by setting the following expert parameter:
pt minimum wall film thickness = <real number> [m]
Setting this expert parameter to a large value forces the particle tracking calculation to treat wall particles as individual spherical particles using a different mass transfer correlation with more reasonable transfer rates.

ANSYS CFX Release 12.1. A custom executable for ANSYS CFX Release 12.0 is available on request.

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