Subject: Re: OT: case fans
From: Christopher Erickson (cerickson@gci.net)
Date: Fri Dec 28 2001 - 11:13:26 AKST
When computer cases are designed, air flow is an important component of that
design.
Most cases use the power supply fan for removing air from the case and vent
holes at the far corner from the power supply fan. There may be additional
ventilation holes as well.
The general intention is to move air across the heat-producing components inside
the case.
Installing a secondary cooling fan backwards from the intent of the case
designer may result in an airflow that bypasses a large part of the components
in the case, or causes a cancellation of air flow if there are no other case
vents.
Some case designs need the secondary fan pulling air into the case for proper
cooling. These are usually located on the opposite end of the case from the
power supply fan. These fans are usually mounted medium to low in the case as
well.
Other case designs require that the secondary fan pull air from the case, just
like the power supply fan is doing. These cases usually don't have the
secondary fan located at the opposite end of the case. They usually have enough
passive vent-area located low in the case to more than match the area of the two
cooling fans combined. These fans are usually mounted medium to high in the
case as well.
Years ago I would find import cases with improper cooling designs once in a
while. I have not seen these problems in cases less than five years old.
-Christopher Erickson, Engineer
Mike Tibor wrote:
>
> On Fri, 28 Dec 2001, Bryan Medsker wrote:
>
> > Also, if the power supply fan is blowing out of the case, doesn't
> > it make sense for the secondary fan to be blowing into the case?
> > Or is there a situation where it makes sense for both to be blowing
> > out?
>
> I can't think of any case I've ever seen where it would be a good thing to
> have all fans trying to exhaust air out of the case. All this would do is
> create a vacuum in the case, with little or no airflow. You generally want
> intake and exhaust air to be equal in volume. For example, with the power
> supply fan exhausting hot air out of the case, installing a secondary fan
> at the lower front (for most cases anyhow) to pull air into the case would
> be very helpful.
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