[Amps] making sinks black

[S. J. Blackwell]

Tom,
I agree with your statements below. The color has very little to do with 
heat sinks that we deal with.

Most heat sinks now days have relatively tall closely spaced fins. For 
practical porposes the heat sink, from a radiation stand point, could be 
looked at as a block of material the length, width and height that would not 
include the fins. The only radiation heat loss for all practical purposes 
would be from top, bottom and sides. Little radiation loss from the fins as 
they face each other. They are clearly designed for an air flow over the 
fins. Paint, in my veiw, would impede cooling, no matter what color. Anodize 
is another matter. Anyone for black anodized bottom, pink fins except the 
outside surfaces of the first and last fins and the fin edges? Arrange the 
heat sink for good convection, if that is not sufficient, then blow it, pink 
or not. It doesen't matter. For all practical purposes the black body does 
not include the fins.

73
Sam, W5LU


>From: "Tom W8JI" <w8ji at w8ji.com>
>To: "slifamily" <slifamily at earthlink.net>,"'Amps Reflector'" 
><amps at contesting.com>
>Subject: Re: [Amps] making sinks black
>Date: Sat, 22 Jul 2006 17:00:47 -0400
>
> >>  Black bodies radiate and absorb heat many times
> >> more efficiently than a white or shiny body.
> >
> > I have heard it said that this is largely true at extreme
> > temperatures.  Might be nice to have someone dissipate a
> > "real world" amount of power (say 100 watts) in a heat
> > sink of raw aluminum and do it again with an identical
> > sink that is black.  I have a hunch that the heatsinks
> > will
> > have similar temperatures
>
>That might be true. Very often the largest portion of
>cooling is through contact with moving air.
>
>This is the same as several others have said, but it might
>be useful to repeat it anyway in different words....
>
>The only advantage to a dark color is when the heatsink is
>surrounded by cooler objects and a substantial portion of
>cooling is through infrared radiation and not through
>cooling by contact with a moving airstream.
>
>If we force air cool or convection cool a heatsink that has
>a "view" of hotter surfaces, things are generally better
>with a clear surface.
>
>73 Tom
>
>
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