Re: FW: 1221B cooling (and zaprabbit stereo)

[Colin Dedman <cjd121@rsphy1.anu.edu.au>]

Mark Hanson wrote:

> I've measured the "Black body radiator" that is repeated incorrectly. Black
> absorbs heat better but DOES NOT radiate any better, the best is raw
> aluminum or copper, not coated with anything.

Hi,

I didn't see the previous postings on this topic (if there were any) so maybe I
misunderstand what you are saying here. What I can tell you is that the
radiated heat from a surface is proportional to the 4th power of the absolute
temperature, and the "emissivity" of the surface. Defining a perfect black-body
radiator to have an E=1, typical values other surfaces are 0.05 for polished
aluminium or copper, 0.2 for highly oxidised aluminium or copper, 0.9 for black
paint, and 0.96 for lamp black. Thus it is fair to say in general that black
DOES radiate heat better. In practice though, heat loss through convection,
natural or forced, usually contributes more than radiation unless the surface
is really hot.