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Quiet PCs, Ducting Air from Case Fan to Heatsink?
Milo_Mindbender asks: "While listening to the whine of my heatsink fan I was wondering. It seems like a good way to get quiet cooling for the CPU would be to mount a fan in the back of my case and run a duct of some kind (folded sheet metal or some kind of hose) from the back of the fan directly onto the top of a fan-less CPU heatsink. You should be able to get the same amount of airflow with a large slow (quiet) case fan as you do with a little noisy cpu fan...and the air being blown onto the heatsink would be cooler as well. This seems like a fairly obvious idea so I'm wondering if there's some reason why it wouldn't work, or if anyone has tried it and could tell us how it turned out." Yeah, but what about the heat in the rest of the system? Depending on the size of your enclosure (and what's in it), you may or may not need more than one fan. Has anyone tried something like this and can comment on how well it worked?
I'm glad people are actually starting to care about noise reduction in PCs. People tend to get a little defensive when the new fan they bought keeps the people in the next apartment awake, just so they can hold onto the few extra MHz they were able to squeeze out.
More on topic, back in my tech days I remember seeing a setup something like this in an IBM case. I don't think the processor had as much need for cooling as the current bleeding edge of speed (it was maybe a Celeron 300 or so) but the heatsink on the CPU was cooled by the fan in the power supply.
I'm no expert but it seems like ducts could work just fine especially if you had a fan the size of the side of your case. Maybe I'll strap a house fan on my box and just set it to low, I hope the magnets don't erase my hard drive.
I just blew out about 100 dells (low end of my current job, an air compressor, a shitload of computers, and a whole lot of dust), and the labs that had the dells (24 total per lab) when compared to the labs of the others (non-dells) are a good deal more quite, quite enough to the point of where we can acctually Sleep there. On that note, and I don't know if it's connected or not to the use of ducting, the dells have alot less dust in there then all of the rest.
(Score:0, Interesting)
Speaking of aircompressors, careful when blowing out computers. If you spin the little fans beyond their normal speed you can kill the little sleeve bearings... I've did this a couple times years ago before I learned better. If you must clean the fan, stop it from spinning with a screwdriver or something. Also, make sure you have a water trap on your air line or you can end up spraying a fine mist of water all over the inside of your computer.
Back on topic, lots of commercial machines / servers have this ducting. My compaq servers had it over the ram and CPU's and rather than blowing in from the out side, it sucked the air out. Your big heat generators are your RAM, CPU, and diskdrives.
My homebrew tower actually has one big-mother fan that takes up 3 5-1/4" drive bay slots (sits in the front of the opening) to cool the drives behind it in addition to the 2 other case fans, and power supply fans. With dual processors, 2G ram, 4 36G 10Krpm scsi drives, it would get bloody hot in there without all those fans.
While I haven't played with it much, the lmsensors package on linux can tell you temps of various things on the motherboard which could be useful in playing with cooling.
In trying to keep the noise out of the house, I built a cabinet in the garage for my servers and ran a duct from my central airconditioner to the cabinet. I run the furnace fan continually and the thermostat is never set over 75, so it keeps things nice (note that I have a thermostat controlled damper that shuts the vent when the heat kicks on.) I'm mentioning this because you have to keep in mind that you can have that you can have nice airflow in your case, but if your machines in a 95 degree room it's not gonna do much good.
Many high-performance heatsinks have incredibly powerful, incredibly noisy 60mm high-RPM fans. The best and the loudest are made by Delta. 54 dBa is not unheard of for their top-of-the-line models. That's way above anything I can stand, however.
Ducts and passive cooling are options, but they are not exactly optimal. A better solution is to use a larger-but-slower fan with equivalent airflow. To push the exact same airflow as a 60mm fan, an 80mm fan can spin *much* slower, thus producing lower noise. And with more space to work with, the fanblade tips can be shielded a little better on the outside rim, lowering noise dramatically. (It's the tips that make the most noise.)
But please don't use a fan adaptor on a 60mm heatsink. You need something designed to accomodate 80mm fans. For AMD socket chips, the Alpha PAL8492 is *wonderful*. Put some Arctic Silver and a lowspeed fan on that baby, and get better cooling than almost any noisemaker I've ever come across. I'm sure there are similar alternatives for Intel CPUs.