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jason November 6, 2003 14:04

where to get absorption coefficient
 
HI,

Do you know where I can get the absorption coefficent of gases (such as N2)? I totally have no idea on those reference database. Thanks

David November 6, 2003 14:11

Re: where to get absorption coefficient
 
hi,

The coefficient is not fixed for N2,fixed for Argon etc.

It depends on certain factors.

There is an equation based on integrals for the absorption coefficient as well as for emissivity, transmissivity etc.

Otherwise you can find it in tables and abaqus, depending on the wave length and temperature.

Any good book on radiative heat transfer would give you some more useful informations.

I hope this helps

David


jason November 6, 2003 16:18

Re: where to get absorption coefficient
 
Can you give me a rought estimation of that coefficient for N2 and NH3 about 1000 oC. 0.01, 0.1, or 1?

Thanks.

›zzet Karabay November 6, 2003 19:32

Re: where to get absorption coefficient
 
I am studing methane decomposition. I need methane, hydrogen and carbon absorbtion functions. Functions is directly related temperature. Temperature 500-2200 K

David November 13, 2003 08:56

Re: where to get absorption coefficient
 
hi,

sorry for the delay. I'm afraid not to be able to give you a straightforward answer at this stage.

However you can go to: http://www.iet.auc.dk/courses/face8/Advanced%20Heat%20Transfer%20-%201st%20part.pdf which would give very useful informations about radiation modeling and the absorption coefficients in gases.

I hope this helps

David

Volker Pawlik November 26, 2003 04:15

Re: where to get absorption coefficient
 
Most gases are more or less diathermal, i.e. they do not absorb radiation only in very small bands. (e.g. N2 is such an element, NH3 unfortunately not!)

Take a good book about gas radiation and certainly aou'll find some advice (or see the citations in the fluent users's guide concerning the wsggm (weighted sum gray gas model)



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