volume concentration

sucjun · September 27, 2010, 00:40

I have some queation using CFX.
Dispersion problem.
rectangle box.
initial condition : air in rectangle box
boundary condition : inlet(Hydrogen mass flow), openning

1. I can not fine volume concentration in CFX-post.
(just mass concentration, mass fraction)

2. How conversion to volume concentration.

ghorrocks · September 27, 2010, 06:33

You can calculate it from the mass fraction and molar masses of the components. I will leave the derivation of the equation up to you from there.

sucjun · September 27, 2010, 07:03

Thank you for your comment.
But I don't know conversion equation.

ghorrocks · September 27, 2010, 07:11

http://en.wikipedia.org/wiki/Molar_volume

sucjun · September 27, 2010, 07:27

I need to Hydrogen Volume Concentration (Vol %).
(Time series value on sensor(points))

Hydrogen density : 0.09
Air density : 1.205

If the sample is a mixture containing N components, the molar volume is calculated using ~~~/

what is the Xi?

mvoss · September 30, 2010, 03:42

hi

if V is m3/mol and M is mol what could possibly x_i be?
It is Mass_i/Total_Mass (MassFraction), and if you sum up over i components you end up in a weighted Molar Mass. This divided by the weighted Density of the Mixture is the Molar Volume.

$\frac{\sum\frac{Mass_{i}}{Total_{Mass}}*\frac{Mol_{i}}{Mass_{i}}}{\frac{Total_{Mass}}{Total_{Volume}}}=\frac{\frac{Mol}{Mass}}{\frac{Mass}{Volume}}=\frac{Volume}{Mol}$

neewbie

P.S.: next time i´ll find the Latex button in the beginning.

papatel · May 13, 2021, 07:44

Quote:

Originally Posted by sucjun

I have some queation using CFX.
Dispersion problem.
rectangle box.
initial condition : air in rectangle box
boundary condition : inlet(Hydrogen mass flow), openning

1. I can not fine volume concentration in CFX-post.
(just mass concentration, mass fraction)

2. How conversion to volume concentration.

Hello dear,
I have same case. However, I am using fluent. How did you find mass concentration there?

Gert-Jan · May 14, 2021, 03:42

Possibly fluent can do it for you.
After running the case in the menu "Run Calculation", you can find the button "Data File Quantities" with which you can control the variables that are written to the dat-file.
Isn't the variable you're looking for present in the long list?

papatel · May 14, 2021, 08:49

Quote:

Originally Posted by Gert-Jan

Possibly fluent can do it for you.
After running the case in the menu "Run Calculation", you can find the button "Data File Quantities" with which you can control the variables that are written to the dat-file.
Isn't the variable you're looking for present in the long list?

Dear Gert,
Thank you for your response. I checked Data File Quantities. They have a molar concentration in mol/m3. However, I need it in percentage. I checked online a lot. But equations are too confusing. I am getting 40 mol/m3 H2 molar concentration. Can you please help to convert it into a percentage?

September 27, 2010, 00:40	volume concentration	#1
sucjun New Member seok jun Join Date: Sep 2010 Posts: 3 Rep Power: 15	I have some queation using CFX. Dispersion problem. rectangle box. initial condition : air in rectangle box boundary condition : inlet(Hydrogen mass flow), openning 1. I can not fine volume concentration in CFX-post. (just mass concentration, mass fraction) 2. How conversion to volume concentration.

September 30, 2010, 03:42		#6
mvoss Senior Member Matthias Voß Join Date: Mar 2009 Location: Berlin, Germany Posts: 449 Rep Power: 20	hi if V is m3/mol and M is mol what could possibly x_i be? It is Mass_i/Total_Mass (MassFraction), and if you sum up over i components you end up in a weighted Molar Mass. This divided by the weighted Density of the Mixture is the Molar Volume. $\frac{\sum\frac{Mass_{i}}{Total_{Mass}}\frac{Mol_{i}}{Mass_{i}}}{\frac{Total_{Mass}}{Total_{Volume}}}=\frac{\frac{Mol}{Mass}}{\frac{Mass}{Volume}}=\frac{Volume}{Mol}$ neewbie P.S.: next time i´ll find the Latex button in the beginning. Last edited by mvoss; September 30, 2010 at 08:06.*

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September 27, 2010, 06:33		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,697 Rep Power: 143	You can calculate it from the mass fraction and molar masses of the components. I will leave the derivation of the equation up to you from there.

September 27, 2010, 07:03		#3
sucjun New Member seok jun Join Date: Sep 2010 Posts: 3 Rep Power: 15	Thank you for your comment. But I don't know conversion equation.

September 27, 2010, 07:11		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,697 Rep Power: 143	http://en.wikipedia.org/wiki/Molar_volume

September 27, 2010, 07:27		#5
sucjun New Member seok jun Join Date: Sep 2010 Posts: 3 Rep Power: 15	I need to Hydrogen Volume Concentration (Vol %). (Time series value on sensor(points)) Hydrogen density : 0.09 Air density : 1.205 If the sample is a mixture containing N components, the molar volume is calculated using ~~~/ what is the Xi?

May 14, 2021, 03:42		#8
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,827 Rep Power: 27	Possibly fluent can do it for you. After running the case in the menu "Run Calculation", you can find the button "Data File Quantities" with which you can control the variables that are written to the dat-file. Isn't the variable you're looking for present in the long list?