Absorption coefficient for aluminium???

Thomas

Hello,

does anyone know the absorption coefficient for aluminium? I am modelling radiation with the discrete ordinate modell. I have got an incident solar radiation from the exterior into my system. The radiation should heat up the solid material in my system. when it gets heatend a free convetion should be established. I didn´t find any hint which value I should take for the absorption.

I have got double sided walls at the solid-fluid boundaries. What is the "right" "diffuse fraction" for a solid material