2 Jul
1999
2 Jul
'99
9:11 a.m.
Date: Fri, 2 Jul 1999 17:46:42 -0700 (PDT)
Reply-to: classiccmp(a)u.washington.edu
From: Dwight Elvey <elvey(a)hal.com>
To: "Discussion re-collecting of classic computers"
<classiccmp(a)u.washington.edu>
Subject: Re: PC form factor
jpero(a)cgocable.net wrote:
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. (!!).
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. 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. 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?
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