spookmineer wrote:First off, this will of course be highly dependent of what case and what components are used.
I'd like to know if there are general guidelines as for an optimal airflow, taking cooling and noise into consideration.
The first two pages are just that. Also peruse the case reviews, and see what is done with cables and fans, especially the P180, SLK3000, and SLK3700.
For example, take Ralf's cablegami mastery, here:
You don't need to manage anything near that level of perfection to get great results. The key is making sure there's plenty of open space without cables in the middle. Tucking them away and making ugly zip-tie arrangements does a perfectly good, if not picture-perfect, job.
I've got an old Thermaltake Xaser II 6000 case with 5x 80 mm fans:
2 front intake
1 side intake
2 rear exhaust
They are standard sized 80x80x25mm and will do 2000 RPM. They are rated at 32 CFM at "a quiet 21 dB(A) noise output".
True, they are not that noisy, but still audible.
Anything can be 21dBA, but they certainly are not measuring at 1m. Get a Nexus, note that there are real measurements here, and be amazed at the difference. The last time I trusted Thermaltake it nearly fried a Duron (the old Orb coolers). Everything I've heard since hasn't been any better.
For intake, the total amounts to about 96 CFM, outtake will be about the same with a reasonable PSU (or slightly less maybe).
Is 100 CFM considered to be a normal amount of airflow through a case, could it be less (sacrificing somewhat in temperatures in hardware, gaining in silence) or could it be a bit more with the correct fans?
From what I've read in different reviews and forums, 21 dB(A) is not that bad for 32 CFM, this will most probably not be the real noise of these fans though.
Nowhere close, and you're not going to get 96CFM. That's in free air.
If I were to replace these fans, should I be looking for more silent fans with the same CFM, or can I drop a bit in CFM and get even more silent ones?
With otherwise good components for quiet cooling, get Nexus fans and be done with it. With a decent case layout, you might be amazed how easy it is to cool stuff. A cramped case with cable messes and drive cages in the way of a good air path will get you nothing but trouble.
OEMs often short-cut things by having just enough cables, have them made just long enough, no extra parts, etc.. For standard PC cases, though, it takes more work, because everything has to be made with flexibility in mind, and then we must bend it to our will (sometimes forcefully, with pliers).
In the standard configuration of your case, one intake fan will have tons of static pressure relative to the other with the config you're meant to use, vibration dampening is minimal, the 3.5" drives need to be hard-mounted to aluminum
, not counting suspension options in the 5.25" bays. The PSU and rear intake are way too close together to use a PSU with a bottom fan very well (without ducting the CPU HSF to an exhaust fan, anyway). The fans will all be turbulently trying to move the same air around. Ducts help, as does using lower-speed fans.
c: there are no general guidelines as to the amount of CFM through a case should be?
Fro instance, there seems to be a consensus on the amount of RPM a heatsink fan should operate on (120 mm: 800 - 1400 for decent cooling and low noise).
No, because that's not anywhere near as much of a concern as a clean case layout, a sturdy case, dampening, low-power parts, etc.. RPM can be used better, but still not perfectly, because noise always goes up drastically with RPM, but even that's not set in stone.
If you want quieter, neaten up cables, replace the fans with Nexus ones, maybe get rid of the side fan, and mount the hard drives somewhere in the 5.25" space (or make a rig in the front-bottom and replace the cages). Getting it nice and quiet should certainly not be too hard, but it will not happen with any Tt fans in there. Their PSUs they don't make, if you've got one in it, and it could be fine. On a very bright side of things, the Dragon that your case is made from used to be one of the best cases for good cooling out there, and certainly can be made to do a decent job, quietly.
Come to think of it, you may as well try out two Nexus (or just normal opaque low-speed Yate-Loons if you can find them in 80mm) fans in the rear, no side fan, no front fans, then see if that does the job. It just might, saving you money, time, and precious dBAs. Just keep track of your temps and see how well it works. If it doesn't, you may be out $4-10 additional shipping (depending on store), but if it does, you've saved at least another $20.
You may also want to try ducting the CPU fan, if its fan points down onto the CPU, to the side intake. If looks aren't important, cardboard and duct tape should handle it well. If it's a tower-style heatsink, you could try ducting to one of the real exhaust holes.