Direction of Airflow with HSF

[FunkyCowie]

Why do heatsink fans draw air out of the heat sinks? Sounds crazy... let me start again...

As most people have their heat sinks on sideways in their tower cases, would it not be more logical to blow cooler air onto the heat sinks forcing out the warm air that it already going out of the top of the heat sink as the heat rises?

Drawing air from the side when it is already trying to travel upwards surely is counter productive?

Or does it not really matter whether it draws air out or blows air in?

 

[MikeTimbers]

It matters a lot. Most sinks are built with long pins/fins. If the fan pulls air through the sink then the air will be having most effect at the fan end of the pins/fins and little air will move at the base of the pins particularly in the center of the base directly over the cpu. This results in poor cooling.

With the fan blowing, the air travels down the pins to then hit the base increasing the cooling.

The only company that consistently made heatsinks designed for pulling air where Alpha who put a shroud around the top of the sink which forced the air to travel over more of the pins.

 

[FunkyCowie]

Ah I got it the wrong way round... so they are supposed to push air in... strange my old Globalwin ones definately were drawing air out yet they had pretty long fins... seems strange why they were set up that way... unless the person I had the computer made by had a brain fart...