CPU Fan direction

Lee H

Hi

Am I right in asuming that the direction of a CPU fan blows away from the heat sink, thus drawing away the heat from the CPU, it seems odd that putting it in reverse can in some cases make the CPU cooler

Has anyone done this?

tomahawkeer

That would be correct.

tiersten

Its generally better to blow air onto a heatsink but the difference is normally small. The design of the heatsink and fan e.g. shrouded are what determine the direction of the airflow. You should just do whatever the heatsink manufacturer tells you to do.

Devilsbane

There shouldn't be much difference. Blowing air onto it is going to displace air off of it and pulling air off of it is going to displace air onto it. I think it mostly depends on where the relation of the fan is to the heat sink which is going to be more preferred.

SteveLord

Mine (Tuniq Tower 120mm) blows it toward the rear of the case. The fan itself is inserted into the middle of the heatsink.

MentholMoose

Most HSF designs push air toward or across the heatsink. Every HSF I've received with retail Intel and AMD CPUs I've ever purchased has had this design. For the typical HSF with the fan parallel with the motherboard, even if the airflow is at the same rate for both push and pull designs, a pull design will be pulling air from close to the motherboard which will tend to be warmer relative to the air away from the motherboard and will therefore be worse at cooling. A lot of cases now have air vents and guides in the side panel of the case (see attached image), so the HSF can pull more cool air from outside of the case.

Nowadays, quite a few HSF designs have the fan perpendicular to the motherboard. These HSFs typically work equally well with the fan configured to push or pull. Typically cases have an intake fan in the front, and an exhaust fan in the rear, so you will want to have the HSF arranged so that it is pushing or pulling cool air from the front.