Brian Last-Name wrote:
> A fan is just a device that creates a pressure differential. If you
A fan is a device which creates a certain air flow. The rated
capacities of fans is not pressure differential, it is air flow
in (in the USA) CFM (cubic feet per minute). Any given fan produces
not more than its rated air flow. Each fan is capable of providing
only up to some pressure differential. The rated air flow is at
ZERO pressure differential. As the pressure differential increases,
the actual airflow produced decreases.
When a fan is mounted on a case, it attempts to produce the rated
air flow. As it does so, restrictions in the air flow into the
case result in a pressure differential. The pressure differential
increases until either the maximum rated air flow of the fan is
reached, or its maximum pressure differential is reached.
When one increases the restriction, the pressure differential
also increases, but the air flow does not decrease much at first.
After a point, the pressure differential rises sharply, and the
actual air flow decreases sharply as well.
Adding another fan to push air into a case will not increase
significantly the airflow, unless in so doing one has reduced
the restriction, like by punching another hole. Adding a fan
to a hole which already exists will not increase air flow much.
It will increase it some, since a hole with a fan in it has
zero pressure differential across it (up to the air flow
capacity of the fan), but a 4 inch hole has, at normal case
air flows, negligible pressure differential across it, anyway.
> place a fan in one direction on your computer, and there is not
> enough flow through the case, the fan will just drop/increase the
> pressure in the case up to the fan's capability. You will only flow
> the ammount of air that the case can suck in or blow out natrually.
Depending on what you mean by "naturally", this part is correct.
> More fans in one direction, after a certain point, will not make a
> difference. The best bet is to have one fan blowing in and one
> blowing out. Instead of pressurizing/depressurizing the case, you
> are now inducing airflow, which is the only thing that will get your
> heat sinks cooler.
Having two identical fans, one blowing in and one blowing out,
will not increase the air flow, except as noted above.
Mike
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