Learning Forum

[sjohn]

What happens when a species get transfered from a mixture to a fluid? Do the properties of the fluid change or does it remain the same? By properties, I mean molecular weight, thermal conductivity, viscosity, density, etc.

In my exmaple below, 3 species are transferred from phase 1 to phase air at a constant rate. Phase 1 is a mixture (with species), while phase air is a fluid (no species). 

[Rob]

There should be a mixture/species & properties for each phase. So, if you have N2 in a liquid phase (for example) with suitable properties and N2 in air you may well need to check your material definitions. Fluent may not check as the phase interactions don't always need to maintain balance in molecular weight etc: doesn't mean you shouldn't define correctly though! 

[sjohn]

There is no N2 in air since it is a fluid material with no species. 

[Rob]

Yes, which would imply that the molecular weight isn't checked. And so you may need to exercise some caution depending on how much mass is changing phase as the volumes may not add up.