Need explanation of heat transfer from metal surface
Need explanation of heat transfer from metal surface
(OP)
Am I correct in assuming that I can get maximum heat transfer from a metal object (through convection and radiation) by having a rough, black, matte surface? I know black radiates best, but I've heard people suggest painting an object black to increase heat radiated (vs shiny silvery surface.) However, ordinary paint would also act as a slight thermal barrier. Ideally, the bare metal surface should be treated somehow to be black and rough without any coatings. Except maybe for a coating of very high surface area metal (appears black due to very tiny particles) bonded to the base hot metal object (good metal to metal heat transfer.) Right?





RE: Need explanation of heat transfer from metal surface
Best Regards
Morten
RE: Need explanation of heat transfer from metal surface
RE: Need explanation of heat transfer from metal surface
RE: Need explanation of heat transfer from metal surface
TTFN
RE: Need explanation of heat transfer from metal surface
RE: Need explanation of heat transfer from metal surface
I messed with radiating surfaces and coatings years ago.
What I remembered was that ALL paints are nearly black in the far infrared. Here is a link to a commercial site, the same outfit with those nasty pop-up ads, BTW. But the table is fairly complete.
http://www.x20.org/library/thermal/emissivity.htm
You will notice from the chart that most white paint is about as emmisive as black paint.
At ~400+ deg K ( engine heat ) the peak wavelength will be aprox 7 - 10 uM, a long way from visible.
At these temps, radiation cooling is fairly weak compared to forced air cooling.
RE: Need explanation of heat transfer from metal surface
When you hood is closed, the blackbody behavior reaches equilibrium, since everything is enclosed, particularly if the hood is insulated. This means that the only real paths for heat exchange is air flow into the compartment and airflow across the hood. That's why turbos have ports and fins sticking out of the hood, to catch the airflow.
TTFN
RE: Need explanation of heat transfer from metal surface
Thanks guys, you've helped a lot. I have a better perspective now.
RE: Need explanation of heat transfer from metal surface