Foo - Quiet case fans
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02-17-07, 02:07 PM
So I've been looking online, searching for a good deal on two 120mm case fans for an electronics enclosure I've got. I need a good bit of air flowing through there, so 120mm is a must. I see a lot of these fans that advertise themselves as quiet. But looking at the specs, their RPM and CFM is half that of the normal. That would make sense if you wanted to silence a fan a bit more. But, is that all there is too these "quiet fans"? It seems to me that they are charging more for a weaker motor. Am I missing anything?
02-17-07, 03:03 PM
Thats a good question, I spent some time looking for quieter fans but as of right now I have adjusted the fans to a slower speed to reduce the noise. I'd imagine the type of bearings used might affect sound, as will the shape and material of the blades, and how they are mounted, but is it worth it, I dunno. And just so you know, the dB levels some manufacturers say their fans produce are usually inaccurate.
Hopefully Danno will come along and clear this up
02-17-07, 03:15 PM
I could supply half the voltage to the fan, and have it be much quieter, for the same cost.
I don't really need the silent fans, it just was there so I was puzzled is all. The sound of my milling machine far overpowers the sound of loud fans :).
02-17-07, 03:28 PM
Most quiet fans are that. Some like the Panaflo L1A, actually have a slightly different dispersion pattern that makes them more suitable for use in a shrouded application.
And others have high static pressure numbers....those are the ones to get. A fan with a low static pressure number will often fail to produce anythinfg near rated flow rates unless in optimal conditions. A high static pressure fan will have less airflow losses in the same conditions.
If noise is of no concern, just buy some Vantec Tornados....they are technically axial blowers (and finger-choppers)....insane airflow and even more insane static pressure figures.....but at hairdryer noise levels.
02-17-07, 03:42 PM
Ooops, forgot to mention noise.
Case fans will make two kinds of noise, mechanical noise (friction or vibrational), and air turbulance.
The mechanical noise can be fixed in a few ways: better motors (smooth out the peaks and dips in it's torque throughout each revolution), better bearings, and anti-vibrational mounting.
The turbulance noise can be fixed in only one way: reduce turbulence. In this case it's the rotating fan blades causing the turbulence. One answer is to use a larger, lower rotational speed fan if the case can handle it.
The ideal way to quiet down a computer is to increase heatsink efficiency, and then design the case to have a equal intake/exhaust forces on the case, to properly exchange hot air for cool air. I use a hybrid forced/convection setup in my current computer. The design is outdated by almost 2 years now (designed around an athlon XP2500/radeon x800xtpe setup, now running an A64 X2 4600/7800gt sli setup), but is still holding on fine.
The easiest way to increase heatsink efficiency is to use copper heatsinks. Copper is a far superior thermal conductor than aluminum, and will also transfer that heat into the air faster.
The next step up is to use heatpipes to a quasi-radiator (that's what I use, but aluminum based, so the weight of it doesn't rip my heatsink mounting lugs off). This is obscenely effiecient since the quasi-radiator design allows for a far greater dissipative surface, and then allows for use of a larger fan (92mm in this case), which is capable of more airflow at a lower noise level.
Final level, for those that must have the coolest operation with the lowest possible noise levels is of course watercooling....and depending on method used, you can have as little as 0 fans....but the maintenance is high. I used to run water, and it was the most silent machine I have ever built....simply amazing.
Just pick your poision.
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