[wateraction]

Hi, everyone! My model is easy:
Air(300 degree C) running through a duct with a catalyst layer.
and I got two quetions as follows:
1. about "Material":
If I open "energy" option, and in the inlet boundary I set the "temperature" as 573K(300 degree C), will fluent adjust the material parameters like density and viscous according to my temperature setting, or do I have to edit those parameters myself in the "Materials" setting.

2. about "pressure drop" in "surface integrals":
In postprocess, I wanner report the pressure drop of the catalyst layer in "surface integrals", and I'm confused by the net value reported by fluent(plz see the picture).

http://dl.dropbox.com/u/28013317/Pressure_Drop.png
We can see that cata_in is -1134.6866 Pa, and cata_out is -1362.1039 Pa ,how does fluent get the net value as -1248.3953 Pa? I think the right value should be 227.4173 Pa(inlet value minus outlet value).

Thank you for your time!

[byronsmith]

Hai Joe,
if you want temperature dependent properties, when selecting the material, in the properties, use the correlation instead of constant values and then depending on the temp, the properties will change. as for the negative sign in the post processing it denotes the direction and has no physical significance.

hope this helps

with regards
byron

[wateraction]

Originally Posted by byronsmith

Hai Joe,
if you want temperature dependent properties, when selecting the material, in the properties, use the correlation instead of constant values and then depending on the temp, the properties will change. as for the negative sign in the post processing it denotes the direction and has no physical significance.

hope this helps

with regards
byron

Thanks, byron, but I still feel confused.
For the 1st question, You mean I should input a correlation myself instead of selecting constant value for various properties during material setting. However, I wonder if Fluent has a database for each listed material such as air, including density or viscosity at different temperature, then when I select, for example, kinectic theroy or other option except constant value, will fluent adjust the properties depending on the temperature I set?

For the 2nd question, I know the negtive sign denotes the flow direction, but the net value(I think net value should be obtained by "cata_in minus cata_out") is wrong according to the data reported by fluent. I mean 1134.6866-(-1362.1039) can never equals to 1248.3953. I think the right value should be 227.4173.

with regards,

--Joe