Somewhen back in the early 1970's (showing my age!) there was an article in one
of the professional UK electronics magazines (long defunct). The people had
done work on heat transfer from heat sinks. The main points I remember were:
1. Because the majority of heat loss is convection, radiation doesn't do a lot
for normal (< 50 degC) temperature rises
2. Painting black doesn't help, because of the insulating effect of the paint,
although a thin layer doesn't hurt too much. Anodising is a good method of
providing a reasonable degree of corrosion resistance without adding to thermal
resistance. Colour doesn't make a lot of odds because the main heat transfer is
by convection.
3. Wide spaced deep fins were best, rather than lots of narrow spaced shallow
fins
4. Turbulent air flow, using fan assistance, really helped.
My advice is to see if there's a local shop will anodise it, otherwise don't
bother, unless for aesthetic reasons, plain aluminium won't do. If you need to
improve the looks of plain aluminium after drilling, dip it in a caustic soda
(sodium hydroxide, or lye) solution. Outdoors, 'cos the fizzing is hydrogen, so
no sparks. After about 10 to 20 minutes, depending on the strength of the
solution, remove. Ideally, soak for a few seconds (it doesn't need more) in a
20% nitric acid solution. Without nitric acid to dip it in, and less dodgy to
use, a swab over with a cloth well soaked in vinegar, or even dip in vinegar. I
don't recommend using the vinegar for culinary purposes afterwards, although it
should be OK. The caustic dip gives a nice finish for a clear lacquer spray, or
is not bad for a 'key' for the primer paint ot stick to.
73
Peter G3RZP
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|