PC form factor

From: jpero_at_cgocable.net <(jpero_at_cgocable.net)>
Date: Fri Jul 2 16:11:19 1999

> Date: Fri, 2 Jul 1999 17:46:42 -0700 (PDT)
> Reply-to: classiccmp_at_u.washington.edu
> From: Dwight Elvey <elvey_at_hal.com>
> To: "Discussion re-collecting of classic computers" <classiccmp_at_u.washington.edu>
> Subject: Re: PC form factor

> jpero_at_cgocable.net wrote:
> > > 1. Fast moving air in an open space will find a surface
> > > and run along it.
> >
> > I append: Air likes least resistance paths. Suppose: bunch of
> > short cards with space above it and space front of it. Most of air
> > will not go into it, it will bypass it.
> >
> > > 2. The only way to make uniform air flow is with restriction.
>
> Also, if you have a flat surface near this air flow, it will
> swing to the side and follow that surface. The rest of the volume
> may even have slight counter flow.

True, sometimes I noticed that. I remembered doing a experiment
blowing into narrow end of funnel and only air races across surface
and air do DRAWS in middle. (!!).

> > In other words: ducts and shrounds?
>
> No, ducts and shrouds only help to get the air to an area.
> What I mean is that is you want nice uniform air flow,
> you need to make something that provides a uniform resistance
> to air flow across the air flow. Screens and meshes are
> what I mean.

Thanks, keep in mind about this. I was thinking how I get even
airflow thru series of slots and holes cut along certain length of
a duct. The series of holes is appox length of 8 cards in length for
that application so I could cool all cards by negative pressure thru
that duct to a exhausting fan to outside.

> > Tell me about this "rotating air will do strange thing till
> > straightened out" what it do strange thing? And how is done to
> > straighten it out?
>
Snip!
> straight out as one would expect. This is why people that
> are serious about cooling will usually us a squirrel cage
> fan over a bunch of muffin type fans. Squirrel cage
> fans output a mostly non-rotating air flow.

Oh, I know about that because I can tell it blows rotating air in a
cone shaped flow due to "flinging" air outwards because of rotation,
but I was asking u why it's would do strange things and what is the
_method_ to straighten it out properly? My comments: Rotary fans
mounted on heatsinks have a dead spot about 20% more than the area of
the fan motor and very inefficient! Blowers is not that easy to
obtain except from electronic supplier at greater cost.

> > fan and ducts/shrounds. Isssues: noise and reliablity from too many
> > fans.
> >
>
>
> The best solution is to provide impingement cooling where
> cooling is needed and an air extraction system.
> Dwight

Dwight, exactly, I forgot to say that I'm PULLING air from heat
producing components via shrouds around heatsinks and ducts to draw
out hot air from cards and PSU. Like vacuuming up hot air and keep
it seperated from cooler air till exhausted outside.

Wizard
Received on Fri Jul 02 1999 - 16:11:19 BST