Krat0s

Distinguished
May 11, 2005
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Hi. I have a doubt. I've bought a new heatsink and i've removed the old cooler and replaced it by this new one. When i had to put the fan at the top of the heatsink i got a doubt. The function of the fan is to put air to inside the heatsink and to the processor or it has to pull out the air from inside the heatsink and processor? I think the answer is the 2nd example i've put here but even so tell me something about this mater.
Thanks
 
Wrong.

Air should be pushing onto the Heatsink.

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pat

Expert
The fan is there to have the air moving around the cooler fins. To understand which way is better, you have to understand how the cooling in your case is going and where the air is the coolest. On most computer, the tower case is the most used. Hot air is always going to raise up. So, you can expect hotter air closer to the motherboard. That's why you don't want to suck already hot air into the cooler. By taking cooler air near the side of the case, and sometime external cool air pushed by a fan on the case's side, you are pushing cool air into the heat sink, which is definitively better..

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endyen

Splendid
With air being sucked through the heatsink, it will take the most direct path to the fan. This tends to leave dead air in the center of the heatsink, and closest to the chip.
 

Crashman

Polypheme
Former Staff
Fans pull from the side, not the center, so only the upper edges of the fins would get significant airflow. I know this to be true and can use a real life example: Many "weekend warrior" racers have tried to clean up their engine compartment and ease the replacement of belts by leaving off their fan shroud, only to find it caused the car to overheat.

Alpha actually made shrouded CPU coolers that would pull air all the way from the bottom because of the shroud, but they still pulled air from the sides, not the center.

A blowing fan will cool everything except the "dead spot" under the bearing. It will in fact cool right down to the base, as air hits the base, swirls, and is mixed with other air that's being exhausted.

Another problem with Alpha's design was that it pulled IN all the heat from the chipset and VRM components, since it pulled air from close to the board. Many people pointed to the cooler's performance to vindicate the design, but those coolers only gave good performance because of things like surface area and copper bases (unusual at the time), even with the shroud testers found that turning their fan around (to make it blow like normal coolers) gave them a temperature improvement!

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