High Airflow vs Static Pressure

[Qu9ke]

So I've read on here that one of the conditions for choosing high static pressure fans is if said fan is directly adjacent to a heat source. I plan on installing 2 120mm fans and 1 140mm close to my cpu for exhaust. Does that mean they should be high static pressure? Speaking of which, what numerical value is high for static pressure anyways?

Also... my case is the thermaltake core v21, and my fans will have to pull/push air through mesh. Is that a sign I need high static pressure?

 

[Sedivy]

Whatever fan you decide on, keep in mind by default pwm header might be set on PWM in which case if you've got DC fans, you have to set it to DC in the bios first or else they'll constantly run at 12V (max speed). 3 pin header should be DC by default but just double check in bios. Your board is new so it should definitely support variable voltage for the fans.

 

[Karadjgne]

The only fan header that's dedicated pwm on any modern board is the cpu fan. The only dedicated DC header that's 4pin on some modern motherboards (usually lower end) is cpu_aux or cpu_pump etc. Every other 4pin will be either dc or pwm or combo, depending on bios. Neither one of my pc's has a bios that has pwm/dc switch, the header just runs whatever is connected automatically.

 

[chegalhavara]

Just my contribution to this post. Why does no one talk about the Corsair ML Series? They are expensive, I know, but they are awesome..

 

[Sedivy]

They're good, mainly due to their magnetic levitation system that makes them durable but on the other hand other fans are very durable too, way past the longevity of most systems so it's not that relevant.
They're good fans but not great fans. Here's a comparison:
http://www.overclockers.com/pwm-fan-roundup-twenty-four-120-mm-case-fans-tested/
Look at ML120 and its performance through the radiators (these are fan comparisons meant for cpu coolers) vs decibels. Now compare it to something like gentle typhoon which not only pushes more air through at 200 rpm less but is also 6 decibels quieter which on a logarithmic scale of decibels is a lot. For a case though you don't need that high a performance (or decibels), so there are better price/performance alternatives, than corsair. Better than noctua for that matter.

 

[chegalhavara]

I was actually thinking of the ML140, but just rechecked and he means to buy 120mm. My bad.
Anyway thats is a really good comparison.

 

[Karadjgne]

Regardless of what actual posted stats are, Phanteks makes the best overall performance fans right now, but it really takes benchmarks to tell any difference. The only quantification an end user can tell is audible differences, and that only happens at high enough rpm to make any sound. The MLs are good fans, as are Noctua, Phanteks, Nzxt, Fractal Design, BeQuiet etc all within a few °C ability, cfm, sp of each other. At that level of performance ability, unless there is a need for max rpm and minimal db(A), the only difference is looks.

All my fans in both cases are capable of over 1000rpm. They never go over 700rpm unless stress testing and are capped by fan curve at 900rpm. So maximum rpm db(A) is really a moot point.

Get quality fans, get ones that appeal to the build. No worries about exact performance or stats.

 

[Sedivy]

Well but you can get away with 900 rpm max by probably having very good airflow and many fans, likely combined with liquid cooling. It's a bit of unfair comparison. On dinky cases with a single intake front fan, crappy cooling and such that are floating around, you will likely need (and want) it to ramp up when temperatures get really high. A lot of aio users end up asking on the forums what to replace their fans with so they are more efficient and less noisy, and how to improve case cooling and in such cases, fan performance may make a difference, though granted, they'll never need to hit the performance of benchmarks so sticking to the major brands is probably enough distinction. The price will be a determining factor though.

 

[Karadjgne]

I use 4 fans in a fractal design R5 (supposedly has limited airflow due to a door blocking front intake fans). Yes, I use a kraken x61. Currently, it's setup front load pull (fans inside behind the radiator and dust filter) and the 2x stock FD fans as exhaust, that's it. Prior, was top mount rad with push exhaust, factory 2x as intakes. In my wife's pc CM 690 II Advanced case, 3x fans. Stock 140mm in front, Noctua NF-F12 on Corsair H55 at top rear mount (pull, fan on top) and the stock exhaust moved from rear to mid-top as exhaust. Pretty basic setups.

Moving air in Gale force inside a case is not needed, the air just has to 'move!' It's the entire principal of evaporation, air absorbs heat energy, gets moved and replaced in a continuous cycle. What's important is the ability of the air to absorb the heat energy, nothing else. Cooler air is denser, absorbs more energy than hotter air, so air flow is king, not volume or speed. Stagnant air, recycled air, circulated air etc has a lower ability to absorb heat energy, as it's already reaching its max, it's not an instant thing, it takes a minute, but cruddy airflow will raise temps of everything, and it's not a linear process, the hotter the case air, the faster it heats up. Provide any regular airflow that'll replace energy laden air, problem solved.

 

[Sedivy]

Yes I don't disagree with any of that. But when the question is what fans to buy to get good performance, longevity, sound and price, there is a ranking, with diminishing returns at higher values sure. I always think ultimately price will drive the choice among popular brands, followed by aesthetics and relative desperation for every bit of extra cooling to be squeezed into the case at low price.

 

[amtseung]

Unless crazy static pressure, space constraints, or aesthetics are of concern, can't go wrong with all purpose, dirt cheap multi fan packs like this one. Provided the fan bearing is of sufficient quality and you're not spinning them "to wang", I doubt much consideration past overall cost needs to be placed in selecting the right fan.

Depending on the restriction, static pressure isn't all that important after all. I decided to experiment when I was reworking my loop yesterday, so I strapped a Corsair AF120 fan to an XSPC EX120 rad and it's working just fine moving air through it at 1100 RPM (60% duty cycle). Not as effectively as Gentle Typhoons at 1100 RPM, but good enough. The same AF120's as an intake in my S340 with the front panel on though, moved no air at all. It just continuously recycled the air from the front half of the case. Replacing them with GT's fixed the issue, with less fan RPM.

From my own personal experiences, relative desperation for every bit of extra cooling tends to come from not enough static pressure and/or not enough heat dissipation surface area, which really can't be properly fixed by spinning fans to wang and back to provide gale force winds.

Just, y'know, IMO.