Porous Model for distributor
 

Hi,
I'm working on a distributor of a boiler: it should distribute the mix air+gas from the fan the to the heat exchanger (after have gone through a certain circuit).
Since the distributor is a very dense metallic web (1 mm thick), I prefer use porous model (to avoid a mesh too heavy).
I think that in this case it's better the Porous Zone rather than Porous jump because the distributor isn't plane but a little curved and the flow (turbolent) isn't perpendicular to it. Am I right?
Above all I need some advice to define Inertial & Viscous Resistances: is possible to calculate them without experiments?
From Fluent Manual I haven't found a good help (sometimes only C2 is calculated,ecc...)
Please help me :)

(excuse me for my horrible english)