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-   -   Mass Fraction and Mole Fraction don't tie up (http://www.cfd-online.com/Forums/fluent/107253-mass-fraction-mole-fraction-dont-tie-up.html)

KieranHegarty September 21, 2012 11:39

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

hazwani fatihah February 28, 2015 11:22

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


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