CFD Online Discussion Forums

CFD Online Discussion Forums (
-   FLUENT (
-   -   Question about Absorption coeff. (

passer-by August 7, 2001 05:02

Question about Absorption coeff.
Did anybody experience radiation? I'm suffering from finding a value of O2 absoption coefficient. Temperature range is roughly between 1400K and 2000K.

Since I'm a novice in radiation, it's not easy to find proper references. Can anyone suggest? Anything will be appreciated.

Jin-Wook LEE August 7, 2001 06:57

Re: Question about Absorption coeff.
Theoretically, pure O2 can not absorb radiation energy. So, theoretically, the absorbtion coefficient of O2 is zero. One of my friend uses 0.01(m^-1) or less value when he is interested in the solid(surface) radiation with air as gas phase material because he wants to include the effect of small amount of radiating material, such as CO2 and H2O, in the air. Actually, there is 1~2%(volume fraction) H2O in the air according to the humidity, and some CO2.

Sincerely, Jinwook

passer-by August 7, 2001 08:57

Re: Question about Absorption coeff.
Thanks a lot for your answer. Can I ask you one more?

If a gas media in my system is only air, is it reasonable to set the absorption & scattering coeff. to zero value? As I know, composition of O2 in air is dominant and I don't have to induce an effect that your friend is interested in.

I just consider a surface radiation. I wonder what is your opinion. Thanks.

Jin-Wook LEE August 7, 2001 21:06

Re: Question about Absorption coeff.
This my personal opinion.

If I were you, I am going to set the absorption coefficient of air as zero or very small value, e.g., 1.e-05, and scattering coefficient as zero, for the gas(air) phase calculation. This is just trick to include radiation model to the heat transfer analysis for the radiating surface with non-absorbing gas phase.

Sincerely, Jinwook

All times are GMT -4. The time now is 15:37.