Home made fan shroud.

Cope said

Hummm.

I would think the paint would act like a barrier and slow the heat transfer?

I know bare aluminum transfers heat like crazy because when I cut it it's hot as hell all the way at the other end of the 4x10 sheet...

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1. No. In heat transfer by radiation, black surface color is best.
2. You are talking about heat transfer by conduction and aluminum is excellent and copper is an even better conductor.
The third type of heat transfer is convection _ transferring heat from a material to moving air or gas. Here the most effective is a fin.