OT fan question: suck or blow, which is best?

I'm attempting to lower my cpu temp and currently have my xp1800+
running at 1545mhz kicking out 55-60 Celsius. Case temp is 24C.

I have 4 80mm 3000rpm case fans (2 front - 2 back) and a socking great
coolermaster aluminium heatsink and fan (4200rpm) which sucks air off
the heatsink.

Is it worth my while turning the fan on the heatsink around so it
blows instead of sucking? I'm just wondering because with so much cold
air blowing through my case the heatsinks fan seems very ineffective.

On Sun, 14 Dec 2003 12:02:06 +0100, Nittaku wrote:

On my PIII/800MHz with simple cooler, the air is blown into the heatsink. So
I always thought it was the proper way. It's not??

All the CPU fans I have seen have the air blown away from the HS.
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Andrew wrote:
On Sun, 14 Dec 2003 12:02:06 +0100, Nittaku wrote:

On my PIII/800MHz with simple cooler, the air is blown into the
heatsink. So I always thought it was the proper way. It's not??

All the CPU fans I have seen have the air blown away from the HS.


Thats pretty odd since probably at least 95% of them blow onto the heatsink.

Ben
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Finned heatsinks work better with the fan blowing down, but heatsinks with a
grid of vertical pins are more efficient with the fan "sucking" up.

On this page
http://www.dansdata.com/coolercomp.htm
there is a comparison of an awful lot of heatsinks. In the section about the
Alpha PAL8045, a cooler with pins, he says...

"Incidentally, the fan should correctly be installed to suck air upwards
through the heatsink, not blow air downwards onto it. In the picture of the
assembled cooler above, the fan's upside down. Mea culpa. I tested both
arrangements and the difference between sucking and blowing is 5% at most,
but you might as well have that extra 5% as not."

Blow air in. I like the example, do you stand behind the fan or in front of
the fan to cool off.


Joltjocky

On Sun, 14 Dec 2003 14:51:15 +0100 Singing Yo-Ho-Ho and a Merry KMA
Nittaku wrote :


"Donald Witmer" wrote in message
...
Blow air in. I like the example, do you stand behind the fan or in front
of
the fan to cool off.

Very nice example

Not really ;-)



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It sucks
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"Shep©" wrote in message
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On Sun, 14 Dec 2003 14:51:15 +0100 Singing Yo-Ho-Ho and a Merry KMA
Nittaku wrote :


"Donald Witmer" wrote in message
...
Blow air in. I like the example, do you stand behind the fan or in
front
of
the fan to cool off.

Very nice example

Not really ;-)



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"Andrew" spamtrap@localhost wrote in message
...
On Sun, 14 Dec 2003 12:02:06 +0100, Nittaku wrote:

On my PIII/800MHz with simple cooler, the air is blown into the heatsink.
So
I always thought it was the proper way. It's not??

All the CPU fans I have seen have the air blown away from the HS.
--

Then all the heatsinks you have seen must be Alphas...because all the rest
blow into the HS...it really does not make much difference anyway.

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"Donald Witmer" wrote in message
...
Blow air in. I like the example, do you stand behind the fan or in front
of
the fan to cool off.


Joltjocky

Then why do some of the best heatsinks around i.e. Alphas have the fan
sucking????...As long as the air is directed over the fins (Alphas use a
shroud to achieve this) it works either way

I am in the midst of an experiment running the fans in both directions. My
initial results are pretty similar both ways. Being into electronics I can
tell you that manufacturers don't want to suck the hot air over the fan
because it will lower the fans life expectancy because the bearings run
hotter. My setup is as follows

A7N8X-deluxe Rev 1.04 1007bios
2500 Barton
SLK-800 Heatsink
Vantec Stealth 80mm fan (2000rpm) for CPU
2 Panaflow undervolted to 5v case fans

My results
Stealth Fan Sucking 44-47c average use
Stealth Fan Blowing 44-47c average use

In the above case it makes more sense to blow because the fan will last
longer.

It does however seem logical that sucking would lower temps because you are
not forcing the hot air back down toward the CPU. This may work well if you
have an ambient air supply coming directly from the exterior of the case
feeding the base of the heatsink. Shrouding to direct the airflow like this
is next on my list.
I could care less about the fan life, I just want the thing to cool
efficiently and quietly.

David

"BigBadger" wrote in message
...


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"Donald Witmer" wrote in message
...
Blow air in. I like the example, do you stand behind the fan or in front
of
the fan to cool off.


Joltjocky

Then why do some of the best heatsinks around i.e. Alphas have the fan
sucking????...As long as the air is directed over the fins (Alphas use a
shroud to achieve this) it works either way