If you built the box yourself, fan flow direction is up to you.

In the case of the PSU fan, however, which comes preassembled, I'd elect to leave that the way it was manufactured.

As for the other fan(s) in the case, my first choice would likely be to orient them in such fashion that they pressurize the interior of the case if possible.

These fans are typically designed such that their own airflow also serves to cool the fan itself. This can be critical in fans that operate from DC levels rather than AC, as those fans typically contain electronic motor control components inside them and placing the fan such that it is always pulling warmer air from the cabinet across itself may result in a shorter Mean Time Before Failure of that fan. (See what I mean about problems not being just "one-input"?)

But the realworld bottom line comes in monitoring the internal temps to see if your pc is near to overheat condx or not and if found to be, try changing the fan orientation around.

The problem with the above is that most monitoring programs are likely only going to be concerned with the CPU temp and not the other internal components. Still, we might be able to gather a bit of assumptive information from that, for example, fans in one direction might result in a lower CPU temp than when in the other.

I once read an engineering study on the subject of cooling internal electronics that showed through empirical test results that the biggest single factor in heat retention is -- the lowly "house dust". They found that house dust has an R factor higher than almost any manmade insulation known. Therefore, keeping the internals clean by doing routine blowouts is a very good thing to do for your critical computer components. Just a wee bit of house dust on fan blades can lower the efficiency of the still-spinning fan by an incredible percentage. And can also force the fan to run in an umbalanced state, which takes its toll on the tiny fan bearings.

But, really, if all is well and there are no overheat problems, likely not worth the effort to pursue, that, "If it works don't fix it" line is a good one IMHO.


--Mac

Last edited by Mac; 06/15/13 06:29 AM.
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