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-   -   Thermal conductivity in porous materiale II (http://www.cfd-online.com/Forums/cfx/20439-thermal-conductivity-porous-materiale-ii.html)

Andrea June 16, 2004 08:28

Thermal conductivity in porous materiale II
 
Cfx 4.4 - Steady state

In my domain I have a gas in a channel and a fraction of the channel is porous (graphite).

In porous zone I'm using porosity weighted conductivity.

Porosity=0.6

th_cond_gas=0.5W/(m*K)

th_cond_solid=125W/(m*K)

I calculated

th_cond_eff=125W/(m*K)

If I set 125W/(m*K)(using USRCND) in porous zone, but gas temperature increase abnormally in this zone (about 430C instead 353C expected).

Why?

Thanks

Andrea


Jeff June 17, 2004 22:44

Re: Thermal conductivity in porous materiale II
 
If I use porosity weighting with your numbers, I get 50.3 W/m-K. But I don't think even an error in conductivity should increase the final temperature, only get it there faster. If there are heat sources somewhere else in the model, this heat will only be conducted "faster" through the media, resulting in a higher penetration into the media as well. Still the peak temp. shouldn't change. Do you have some sources somewhere that are unaccounted for?

Jeff

Andrea June 21, 2004 04:18

Re: Thermal conductivity in porous materiale II
 
I'm using 50W/m-K (but I made a mistake in the previous message)

I don't have heat sources but I have (in a zone of the porous material) a mass source of one of the mass fraction...

Can this source cause a sensitive temperature change?

Andrea


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