In the name of better WoWing for her, I did some pretty significant upgrades to my girlfriend’s PC this weekend, not the least of which was that I added a second case fan. She’s got a really nice case, but I felt it could use a wee bit more ventilation so I added a 80mm Vantec Stealth fan up front to help it breathe. (Turns out I’m going to wind up replacing the one in the back as well, because it’s the source of about 90% of the noise this thing produces.)
Here’s the thing: when I installed the fan, I noticed two orientation arrows on it. One, obviously, indicated the airflow direction, as it was parallel to the axis of the fan. The other was perpendicular to the other and I could only guess was meant as a “this way up” indicator.
Try as I might, though, I can’t for the life of me figure out why it would matter which way was up to the fan. Am I missing something obvious?
:smack: You know, that certainly qualifies as both something obvious and something I didn’t consider. I guess since one arrow indicates airflow direction, I figured that was all I really needed to know. And now that I think about it, I still don’t know why I’d need to know rotation direction other than to figure out airflow direction.
In general, does one want to push air into a hot space, or suck air away from a hot space?
I set my microprocessor mini-fan to suck air away from the heat sink - it seemed like the logical thing to do. But I also installed a fan to blow onto my C and D drives, because they don’t have any kind of structure to direct the flow.
Normally for computer fans, you want any fans in the front of the computer to pull air into the computer, fans in the rear of the computer to blow out of the computer, and the heat sink fan to blow down towards the heat sink.
The goal is to provide good air flow so that the front fans bring cool (or cooler) air into the computer, hot air rises, so it enters the front bottom, and then travels up the motherboard getting hotter, till it is exhausted through the back fans out of the computer. As for the heat sink, you want to be blowing cooler air onto the heat sink, so that when it leaves through all those metal fins it takes the hotness from the metal into the exiting air.
As to flow direction on a heatsink, the issue is unsettled. While I think like Hirka T’Bawa on this, there have been tests done that have had results go both ways.
Note that the power supply is a big source of heat so you definitely don’t want to pull air out of it into the case or otherwise make it’s fan less efficient. So an airflow going from far side of the case towards the PS is a good idea. One common mistake is to have fans on the same side of the case blowing in opposite directions. (Setting up a “U” flow.) E.g., a fan on the back side near the PS blowing towards the cpu is a bad thing. Turn it around. You definitely want as close to a straight-thru flow as possible.
