PC form factor

From: Dwight Elvey <elvey_at_hal.com>
Date: Fri Jul 2 19:46:42 1999

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.

>
> 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.

>
> > 3. Rotating air will do strange things until straightened
> > out. ( examples, air coming from a rotary fan and also
> > most air going through a single small restriction ).
>
> 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?

 Here is an experiment you can try for your self. Take a rotary
muffin type fan and place a flat piece of metal across the center
such that the air flow would be split on either side.
Use an anemometer to see where the air is going. Much to
many's surprise, the air will make an angled change and go
off to the right or left along the metal surface but not
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.

>
> Do tell your tales about this! I'm trying to design a case to do
> cooling of all drives, PSU motherboard and CPU by one large quiet
> 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
Received on Fri Jul 02 1999 - 19:46:42 BST