J. P. Gilliver (John) wrote:
In message , Paul
writes:
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Where the fan blows down onto the heatsink, the
dust will be near the top of the heatsink. A
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What proportion of such fans blow onto the heatsink, as opposed to
sucking off the heatsink - about 50-50, or is one type much commoner
than the other?

I know "clean box" cabinets tend to operate under positive pressure,
which is counter-intuitive (though does make sense when you think it
through), but there the concentration is on air filtration, rather than
cooling.

JPG

Most of these will blow the air downwards, which
can help cool the Vcore regulator or any other
VRM-like portions near the CPU.

Drawing air upwards has been tried, but doesn't
work quite as well. The design the OP has, has no
plenum to speak of, and a "suction" design would
need a plenum to maintain pressure.

*******

Dust in computer cases, is a function of positive
or negative pressure. And fan location makes a difference,
in terms of "stirring" the dust until the air vents
out the back. With some fan installations "dumping"
more of the dust load into the PC, than others.

Some PCs have dust filters on the front. All
that this does, is guarantee a cleaning job every
three months. And you have to position the
PC, so you can pull the washable filter out of
the computer case (at the bottom front). Without
the dust filter, the same PC can run for a year
or two, without a cleaning.

Paul