[Tfug] Cooling

[Bexley Hall]

--- "Eric M. Gearhart" <eric at nixwizard.net> wrote:

> It's fun when you read it if you emphasize all the
> words in asterisks with the voice in your head :) 

<grin>  That's the point  :>  Sorry, I write a lot
using SGML, etc. so being *stuck* with a single
typeface/font feels quite crippling...  :<
 
> Just joking around btw... please don't take it
> seriously Bexley :) 
> 
> Eric 
> 
> ----- Original Message ----- 
> From: "Bowie J. Poag" <bpoag at comcast.net> 
> To: "Tucson Free Unix Group" <tfug at tfug.org> 
> Sent: Sunday, November 25, 2007 6:51:13 AM
> (GMT-0700) America/Phoenix 
> Subject: Re: [Tfug] Cooling 
> 
> I'm going to report you for *asterisk* abuse. 
> 
> 
> Bexley Hall 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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