Mass Fraction and Mole Fraction don't tie up
 

Hi guys
I have a case where a small amount of O2 (3e-10kg/s) is flowing into a system containing mainly air, the same amount of O2 is being sucked out of the system at another location. I am looking for the mole fraction of the O2 at yet another point in the system.
The model converges fine and if I display a mass fraction contour plot everything looks OK, i.e. I can see my mass fraction of O2 at the entry point is 1.
If however I try to display the mole fraction contour plot, the maximum value is approx 0.21, even at the entry where I know the mole fraction should be 1.

Has anyone got any ideas why the contour plots may not tie up and what I could try to solve this issue.

Appreciate your help.

Kieran

Hi guys,

how to determine mole and mass fraction in species part in boundary condition?
In my case, reaction between methane and air. I got the concentration value %vol/vol but I do not know how to convert it in term of mole and mass fraction.

Has anyone got any ideas? Thank you