Martin,
I started the thread by asking about black paint on heat sinks. I think,
along with the other great educational info I've seen in this thread, you have
answered any remaining questions that may be un-anwered. I think a "titanium
white" anodizing would be the answer if such a thing exists. In my case, I have
overdesigned the cooling capacity by sheer size of the radiator assembly and
huge fan motor.
Since asking about this origional question, I found out about and received
my CP15 cooling plate for my project from Lytron. I will probably use both the
cooling plate with the copper heat spreader in the middle and the heat sink on
the other side. The heat spreader will connect to the side of the cooling
plate that has the tubes. Now that I've found a great cold plate, the heat sink
will be overkill but used anyways.
VY 73,
Mike KE6CVH/JA6WIY
Martin AA6E <aa6e@ewing.homedns.org> wrote:
Will Matney wrote:
> All,
>
> I had to brush up a little on this as it's been a long time since I took any
> thermodynamics ,,,
>
This is an interesting thread. The one point that has not been
mentioned is that the visible color (black or bare aluminum or whatever)
has little to do with heat radiation. Unless you're talking about very
high temperatures (red hot and beyond), the radiation that matters is in
the infrared. You want a surface that is "black" in the infrared.
(Black means that it absorbs all radiation that falls on it. Physics
tells you that a black surface is also the most efficient heat radiator
at any given wavelength.)
The reason that bare steel or aluminum gets very hot in the sun is that
its surface is "blacker" in the visible sunlight than it is in the
infrared, so the absorbed visible light energy from the sun can't easily
radiate in the infrared. We used TiO2-based white paint to minimize the
problem on radioastronomy dishes-- it reflects in the visible, but is
"black" in the infrared. This is not the usual heat sink problem, but
it indicates that painting your heat sinks "Titanium white" might not be
such a bad idea! -- especially if your equipment needs to work in
direct sunlight.
I agree that convection and conduction are the most important ways to
dump heat at low or moderate temperatures, and any paint is likely to
insulate more than it helps.
73 Martin AA6E
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