[plug] that Netway Computers board...

[Onno Benschop]

On Thu, 2003-08-28 at 09:09, Scott Middleton wrote:
> Heat is always an issue with these though. Cupboards and modern
> computers don't go too well together. Remember the days  when CPU's were
> big and heat sinks were not. I remember running the old P133 without a
> fan on it at all. In-fact one day i crossed the fan wires wrong and i
> was actually heating up the CPU and it still ran.

Uhm, AFAIK, unless you're actively adding heat, you're not heating the
CPU at all. 

There is an argument that supports sucking air away from a CPU attracts
cool air from a diffuse source around the CPU. Similarly, there is an
opposite and equally plausible argument that says that blowing lots of
air onto the CPU from a diffuse source above the fan achieves the same.
The only real important thing is that the air moves - in what ever way
you can make that happen.

The biggest challenge in cooling is to ensure that you are not making a
"shortcut" for the air. Another way of illustrating this is by imagining
an inlet fan and an outlet fan next to each other. The air will simply
come in one and leave out the other without actually cooling anything
else in the case.

As a matter of some fun, as some of you know I'm travelling around Oz
with a satellite dish. The electronics (the modem etc.) are normally
found inside the house with two big RF cables heading back to the dish.
For many reasons outside the scope of this forum, I needed to eliminate
those leads. As a result, I have bolted the equipment to the bottom of
the dish.

While I was in Dunsborough, close to the ocean with 53 days straight
rain, water and salt caused corrosion in the electronics - because I
planned for a nice dry environment like the one I'm in now - Kununurra.
The box has active fans blowing into the box, and a passive outlet,
letting the air leave. I now need to make the box water-proof, because
humidity here will rise to 90% in the next few months.

Soooo....

The solution for me is to actively circulate the air inside the box with
fans across a cooling fin, which in turn is connected to an external
cooling fin which is also actively fan forced. A fan costs a few bucks,
so I expect to change fans regularly on the outside.

The point I'm getting to - in a long winded fashion admittedly - is that
the best cooling I can hope to achieve inside the box, is for all of the
air to be the same temperature. I dump heat through the cooling fin
interface to the world, but only to the point that inside and outside
are the same temperature. To assist in making the outside temperature
better, I shade the whole thing under a tarpaulin.

You might at this point talk about peltier devices, water cooling, etc,
but the problem remains that if the outside temp is lower than the
inside temp, there is cooling, if not, there isn't.

Besides, if it gets to be 80 degrees C outside, I've got other problems
:-)

Onno Benschop 

Connected via Optus B3 at S15:51'18" - E128:45'05" (Crossing Falls, Kununurra, WA)
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