Mass Fraction and Mole Fraction don't tie up

KieranHegarty · September 21, 2012, 12:39

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

September 21, 2012, 12:39	Mass Fraction and Mole Fraction don't tie up	#1
KieranHegarty New Member Kieran Hegarty Join Date: Sep 2012 Posts: 1 Rep Power: 0	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

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February 28, 2015, 11:22		#2
hazwani fatihah New Member hazwani Join Date: Nov 2014 Posts: 15 Rep Power: 12	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