How to calculate NOX values in CFD-Post or Fluent in units of ppmv on a DRY BASIS, th

Yarne · November 23, 2022, 13:28

In a Fluent simulation I would like to check the number of NOx particles in parts per million volume dry (ppmvd). Does somebody know what type of expression I can use to calculate this?

LuckyTran · November 23, 2022, 15:16

Fluent gives you the mass fraction but sometimes you can select the mole fraction as well. Convert these to ppm using the molecular weights and then convert that to the corrected dry conditions using the correction.

You can do it in Fluent/CFD post by defining custom fields or externally.

Or are you asking for an example calculation by hand to convert wet to dry values and/or corrected NOx?

Yarne · November 23, 2022, 15:36

I know you can get the mass and mole fractions out of Fluent.
I am more interested in how you can calculate the ppmv of dry NOx.
I found a formula for ppmd NOx, but this is parts per million (mole) and I need parts per million (volume).

LuckyTran · November 23, 2022, 15:42

Mole ratios and volume fractions are the same thing due to Avogadro's law unless we are talking about subatomic particles, but NOx are molecules. The only difference is if you know how to move the decimal point over enough spaces.

Yarne · November 23, 2022, 15:47

I have used this formula to calculate the ppmd NOx

NO.Mole Fraction* 10^6 /(1 – H2O.Mole Fraction)

Is this formula thus also equal to ppvd NOx? Since you say that mole ratios and volume fractions are equal to each other?

November 23, 2022, 13:28	How to calculate NOX values in CFD-Post or Fluent in units of ppmv on a DRY BASIS, th	#1
Yarne New Member Yarne Schlosser Join Date: Nov 2022 Posts: 3 Rep Power: 3	In a Fluent simulation I would like to check the number of NOx particles in parts per million volume dry (ppmvd). Does somebody know what type of expression I can use to calculate this?

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November 23, 2022, 15:16		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,750 Rep Power: 66	Fluent gives you the mass fraction but sometimes you can select the mole fraction as well. Convert these to ppm using the molecular weights and then convert that to the corrected dry conditions using the correction. You can do it in Fluent/CFD post by defining custom fields or externally. Or are you asking for an example calculation by hand to convert wet to dry values and/or corrected NOx?

November 23, 2022, 15:36		#3
Yarne New Member Yarne Schlosser Join Date: Nov 2022 Posts: 3 Rep Power: 3	I know you can get the mass and mole fractions out of Fluent. I am more interested in how you can calculate the ppmv of dry NOx. I found a formula for ppmd NOx, but this is parts per million (mole) and I need parts per million (volume).

November 23, 2022, 15:42		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,750 Rep Power: 66	Mole ratios and volume fractions are the same thing due to Avogadro's law unless we are talking about subatomic particles, but NOx are molecules. The only difference is if you know how to move the decimal point over enough spaces.

November 23, 2022, 15:47		#5
Yarne New Member Yarne Schlosser Join Date: Nov 2022 Posts: 3 Rep Power: 3	I have used this formula to calculate the ppmd NOx NO.Mole Fraction* 10^6 /(1 – H2O.Mole Fraction) Is this formula thus also equal to ppvd NOx? Since you say that mole ratios and volume fractions are equal to each other?