Permeability as a function of gas

[drir]

Hi,

Can someone tell me why the permeability of a porous material is greater for nitrogen than for air?

Thanks

 

[PEDARRIN2]

Maybe it is due to the size of the molecules, but I would wonder to what extent.

Air is mostly nitrogen (~79%), but also contains ~20% oxygen, with some carbon dioxide and other trace molecules making up the difference.

Both oxygen and carbon dioxide are larger molecules so they are less likely to be able to fit through the "pores" of the porous materials.

 

[zdas04]

What are you basing the question on? I've never seen a lab analysis that laid out a rel perm for air and re-did the experiment for nitrogen. I'm usually doing good to get a rel per for "gas" without any details at all.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"