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CPU FAN DIRECTION?

F

FFactory0x

Diamond Member
Hey guys, i was ready some interesting debates on cpu fan direction. Want some input. I had my ys-tek on my sk-7 pulling air away from heatsink for 2 months. As of now I had 11x200 on 2100+ under load 39-41c.
I just turned it around to push air onto it and an getting around same temps. Whats the difference???? Should it push or pull?
 
whichever works best - normally blowing air onto the heatsink is the idea, except for a few like the Alpha PAL8045
 
Originally posted by: Davegod
whichever works best - normally blowing air onto the heatsink is the idea, except for a few like the Alpha PAL8045
Click to expand...

This is really the bes idea.

One day i was doing somthing inside my case when i realized that i must have put the cpu fan on wrong. So i switch it back and then my temps when up! I don remember doing it, but i must have tested both and found which is better!
 
You provoked me into trying reversing the fans on a couple of HSs.The test was done out of the case with the mobo on a box.


On the el cheapo SVC GC68 (3700 rpm 80mm fan) the temp under load (prime95) went up 14 C

On an SK6 (7000rpm 60mm fan) the temp under load went up 11 C.

So basically for mine, reversing the fan turns a quite nice heatsink into a poor one. Its much worse than I expected. Too bad. The reason seems to be that not much air is drawn in at the bottom of the HS when pulling. The air blowing out the top is quite impressive though, especially on the 7000 rpm. It blows air way away from the HS. That could be the advantage of reversing the fan. A shroud or duct around the HS like some Alphas could probably help a lot. I'm trying to think how I could do that.

How about a link to the fan direction debates?
 
I actualy found somthing really weird about my heatsink. i recently purchased another of the one i use on my AthyXP and in one case it works better one way, and in the other, the other way.

 
I think it all comes down to whether or not you have positive or negative air pressure inside the case...I think if you have more air blowing inside the case from the outside it's better to have the fan blowing on the the heat sink...but theres also air circulation to consider. If you have dead zones where air doesn't move it probably doesn't matter which way you mount the fan. Maxium PC had a good article on the Alpha Pal about mounting the fan opposite of the manufactures recommendations. Alpha Pal said to mount the fan so that it was blowing on the heat sink, Maxium PC said they had better temps sucking air across the heatsink. If you have a side mounted fan blowing air into the case(moving air from outside to the inside, onto the motherboard) I would mount the cpu heatsink fan to also blow unto the heatsink. You don't want fans to be fighting each other...
AMBIENT OUTSIDE AIR----->AIR FLOW<-----CPU HEATSINK FAN = BAD...but as Davegod said, whatever works best....
 
Experiment.... Normally it varies with different fans. Always make sure your air flow is going out of the case though never make it cycle around!
 
One school of thought says 'leave it as the manufacturer intended', but then I have experimented with it, with mixed results.

 
Shouldn't the fan be mounted not on the top, but on the side of the heat spreader, so that it blows the hot air towards the top of the case, rather than down onto the heat spreader?

That way, the air would be removed directly from the heat spreader, plus it would avoid the dead spot in the centre of the fan?

Michael.
 
i have a pal 8045 so it's obviously set to suck, not blow. ^_^ I've seen some tests done with thermalright heatsinks and they perform better when the fan is blowing onto the heatsink.
 
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