CPU cooling mystery

[Dalis]

Hi all – I've always been dumbfounded by CPU cooling fan setups. They seem like they're oriented wrong, like they're pointed down onto the PCB instead of blowing directly across the CPU.

Like this setup from the STH article on a QNAP server. Can someone explain where the air is flowing there? Which direction? Why are the fans horizontal, pointing down (from the perspective of the board, not the photo angle), rather than vertical, blowing across the CPU?

When fans are oriented like this, pointing down against the board, where are they getting their air? And those outlets on the right side – that's enough to get the air flowing that way? But why aren't the fans oriented that way then, if that's where we want the air to move? Why are the fans pointed down against a solid, flat object, when we want the air to go sideways, parallel to that flat object (the board)?

Thanks.

 

[BlueFox]

Those are centrifugal fans and they are pointing towards the rear of the case. You should look at some photos of what they look like internally compared to axial fans.

 

[TXAG26]

That's a neat looking system, do you have a link to the manufacturer's page for it?

 

[rafale77]

I have one of these. This is a QNAP TVS 1282. The way it works is indeed that it is sucking air from the front through the front grill then down bellow the centrifugal fan between the MB and the fan itself and then pushes the air through the side opening of the fan towards the back of the unit. The lower fan pushes the air through the CPU cooler and then out the case through the rear grill.