Are there rules for fan air flow direction

[Dunc]

When adding fans beyond what is supplied as standard are there any rules-of-thumb to suggest airflow direction? Should it be equal volume in-out, case positive pressure (more fans blowing in than out) or case negative pressure?

When adding additional fans to a case (cutting openings) assuming that there is adequate space should additions be prioritized to the side(s), top, or bottom? Inlets towards the bottom & outlets near the top (heat rises)?

Is there a science to this or is it pretty much luck?

[Lpfan4ever]

I think most people aim for positive pressure, or at least equal. Positive means less dust.

As for new fans, I'd say imagine the case was cut in half from to the top of the front to the bottom of the back. Anything in the half closest to the front would be intake, other half out. If you were to cut a hole in the side panel for the video card though, I'd probably do that as intake if your card has a cooler that expells heat out of the back. If it spills the heat into the case, I would probably say exhaust just to get the heat out of there quicker and not have it effect the rest of the components.

[ilya]

Originally Posted by Dunc

When adding fans beyond what is supplied as standard are there any rules-of-thumb to suggest airflow direction? Should it be equal volume in-out, case positive pressure (more fans blowing in than out) or case negative pressure?

Positive case pressure is usually better, however there are a few scenarios where negative pressure is more beneficial.

Originally Posted by Dunc

When adding additional fans to a case (cutting openings) assuming that there is adequate space should additions be prioritized to the side(s), top, or bottom? Inlets towards the bottom & outlets near the top (heat rises)?

Side fans generally pose more of an acoustic liability, but a side intake can drastically reduce GPU temps depending on configuration.

I would still prioritize top and bottom holes over a side fan though. But it would also depend on your case.

Originally Posted by Dunc

Is there a science to this or is it pretty much luck?

Not much science, not much luck, more like trial and error. Which is sort of like science I guess.

[Flemminr]

Generally speaking, any case fans on the front, bottom, and left side panel (if facing the front of the case) you'll want to have in taking cool air, and any fans on the rear, top, and right side panel (if facing the front of the case) you'll want to have exhausting hot air. That said, you should always try to balance the number of fans in-taking against those exhausting.

[_dangtx_]

what case you got again?

lately ive favoured more exiting than intaking

[Snarl]

I've always figured Positive Pressure - less Dust, Negative pressure - Slightly better Cooling (The 'ol low pressure temperature drop). lpfan4ever's cut the case in half scenario is very well put and dead on IMHO.

[TheRealHeids]

I have always tried to keep the airflow In/Out pretty close, but slightly positive. Also make sure that you have your case wiring as neat as possible to prevent airflow blockages.