[Tfug] Cooling

[Sean Warburton]

if there are no identifiable hotspots, then as long as air is being
pulled/pushed over the unit, area, whatever, it should be good, right?
I would imagine it would be best to use the properties of air
temperatures to your advantage, whatever the case may be. Intake near
the bottom, exhaust near top (hot air rises, cold air lowers,
therefore intake should be lower and thus cooler), unless, of course,
you have a hotspot, like a cpu or something. Computer cases are taking
advantage of this I think, because mine and many others i have seen
have a couple fans near the bottom of the side, front and rear panels,
and exhaust ports on the top and the one the power supply has. I think
the idea is that cold air comes in low and rushes over your video
cards, CPU, hard drives, and then goes out the top. Cant really say
much more than that, sorry. Maybe somebody else knows of a law or
something you were alluding to...
     Sean

On Nov 24, 2007 11:05 AM, Bexley Hall <bexley401 at yahoo.com> wrote:
> Hi,
>
> I suspect this one is a bit harder to get a
> *definitive* answer -- in the general case.   :<
> *But*, who knows, maybe somebody out there
> actually *does* this sort of thing for a living!
>
> I had to replace the fan in one of my tape
> drives (noisey).  Of course, fans exhibit
> *loads* of symmetry (i.e., there are 8 ways
> you can mount one -- though, ralistically, the
> choices boil down to exactly TWO!)  So, since
> I didn't make a deliberate note of the original
> fan's orientation, I had to think this one
> through...
>
> Fortunately, the fan had a filter on it -- which
> makes the choice easy (you don't need to filter
> EXHAUST air)!  So, the fan should be oriented to
> blow air *into* the enclosure.
>
> This makes sense for a tape device since it helps
> keep crud from getting into the mechanism.  Same
> principle as maintaining positive pressure in sterile
> environments, etc.
>
> But, beyond this, any "rules" for air flow seem to
> be pretty vague... "ad hoc", almost.
>
> In the past, ME's et al. have made these decisions
> in product designs in which I've been involved.
> And, I've never been able to infer any *real* rules
> as to "which is better" (and in which circumstances).
>
> A common approach is to exhaust air from things like
> power supplies.  This makes sense if there are other
> fans in the device that can move the heated air
> generated by other components in the assembly.  Note
> that exhausting air pulled directly from a CPU's
> heatsink fits this same class -- the heat source is
> concentrated and, as such, you can readily pull air
> directly from it.
>
> But, what about devices that don't have these nice
> identifiable hotspots?  Are there any rules as to
> why or when it is best to pull vs. push air?  I
> know the turbulence created by obstructions greatly
> affects the cooling ability of the air flow.  But,
> does the turbulence differ if the is air being
> *pushed*
> into that region vs. *pulled* though it?
>
> (yeah, it's one of those questions that I can -- and
> probably *will* -- die without knowing but it *is*
> puzzling!)
>
> Thx,
> --don
>
>
>
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