Do processor fans blow ON the heatsink or away from it?

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Whipsmack

Gawd
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Oct 17, 2005
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Dumb Q I suppose. But when I put my hand over my CPU fan, I can't feel any air, I feel a slight breeze as if its sucking onto the heatsink rather than blowing...

My case is ultra crappy with airflow so i've been doing some experiments, I set a normal 80mm fan ontop of my video card so that its blowing directly on the motherboard heatsink. The case door is open also. It has reduced my mobo temp by 10c and my processor temp by 5 or 6c... It has also reduced my case noise as I got rid of all the other case fans...lol go figure.

Anyways, the new case designs that have the fan on the side for the processor, does that blow in or out? I'm just curious.

Thanks!
 
the majority of cpu coolers blow air DOWN onto the heatsink.

Places like dell, tend to suck air over and off of te CPU and out the back.
 
Yep, almost all heatsinks nowadays blow ONTO the heatsink, pushing air down to it, rather than sucking it away and outweard.
 
Last time I looked into this, I think you gain maybe 1-2C by blowing air down on the heatsink as opposed to pulling air up through it.
 
(Mildly inappropriate) jokes aside, its better for your motherboard to have air blowing on it
 
If you want to maximize heat transfer between heatsink and air. its best to push "turbulent air" over the heatsink thus its a best to blow into the heatsink.
 
jebo_4jc said:
(Mildly inappropriate) jokes aside, its better for your motherboard to have air blowing on it
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hey hey - easy now... you're the one bringing mothers into this.


:rolleyes: I know - corny. sorry.
 
Woah. I always thought it was better if the fans blew the air away from the heatsink, because it was removing the hot air...
 
It also depends on how the fan mounts onto the heatsink with respect to the motherboard. Not all fans lie parallel to the mobo. If the fan mounts perpendicular, you might be better off sucking air though the heatsink than blowing air into it.
 
holli4pirating said:
It also depends on how the fan mounts onto the heatsink with respect to the motherboard. Not all fans lie parallel to the mobo. If the fan mounts perpendicular, you might be better off sucking air though the heatsink than blowing air into it.
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troof.

imo - air blowing parallel to mobo > air blowing perpendicular to mobo.

for cpu heatsinks because of push/pull potential
 
General Crespin said:
Woah. I always thought it was better if the fans blew the air away from the heatsink, because it was removing the hot air...
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Well, if you have some sort of direct exhaust (like a duct directly from outside air to the CPU fan) then sucking may be better than blowing *snicker* now I understand why this thread went where it did. This type of setup would ensure the overall case temps stayed as low as possible.
However, if you have a "traditional" setup with the nearest exhaust fan blowing out the back of your case, the heat that is sucked away from the CPU is likely diffused into other parts of the case, which wouldn't be much different than cooler air being blown down onto the heatsink.
 
stormshadow said:
troof.

imo - air blowing parallel to mobo > air blowing perpendicular to mobo.

for cpu heatsinks because of push/pull potential
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It's true you can probably shave a few degrees off your CPU temp with a sideways orientation, but it's best for your motherboard to have the air blowing down on it.
 
kirbyrj said:
Last time I looked into this, I think you gain maybe 1-2C by blowing air down on the heatsink as opposed to pulling air up through it.
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A little more Mfrom the heatsink is exchanged with the air temperature blown onto the heatsink. But when sucked off, the fan depends on the air around the heatsink to get to the heatsink quickly so that the heat will be exchanged (this happens at a much slower rate) fast enough for the fan to pull it off. Blowing air on the heatsink decreases temperatures dramatically compared to sucking it off the heatsink.

In conclusion the best setup would be to have one fan push cold air onto the heatsink while another pulls the hot air off the heatsink. But for someone that has a fan like the CNPS9500 (here here), this is automatically done as the cold air goes thru and pushes the hot air out all-in-one.
 
This all really depends on what heat sink you’re using and how you have your case set up.

An example would be the alpha I use on my old K7. It is designed to suck so I set the case up with that in mind.
 
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