SPCR's Fan Testing Methodology

[jaganath]

Would this reasoning still apply to the Noctua fan that was reviewed? Although the depth is the same, the geometry and size of the blades is quite unique.

The unique geometry of the Noctua fan actually makes it worse at providing static pressure, because the swept area is very open and the tip clearance between the frame and the blades is large.

http://www.cooling-masters.com/articles-39-6.html

Les Noctua ont très peu de pression statique disponible (0.5 et 1 mmH2O maxi), leur design très fin et très ouvert ne le permettant pas.

Roughly translated, "The Noctuas have very little static pressure available (0.5 to 1 mmH2O at most), due to their thin blades and open design."

[frankgehry]

You didn't answer the question. In a typical 120mm psu with a lot of air flow impedance, fans with higher static pressure will do better. But spcr would say that with a low impedance heatsink like a ninja, which in some applications can function adequately without a fan, the noctua may do better. Above a certain point, more static pressure won't help. This is where the testing methodology used by spcr really falls short. What's the point in doing a review of the Noctua when they are optimised for free air and very limited in real applications? The only review that may be of some help is at the madshrimps site, but the heat sink used would not be considered low impedance.

[elessar]

Please, can you measure noise form smaller distance (eg 0.5m) in the case that noise is immeasurable (noise power is under sensor sensitivity)?

example:
12V 23dBA@1m 1040RPM 28CFM 0.61W
9V 20dBA@1m 820RPM 20CFM 0.49W
7V ~18dBA@1m 650RPM 17CFM 0.41W
5V <18dBA@1m 480RPM 11CFM 0.35W
measurement from 0.5m for 5V

noise level should have been 6db greater...

Thanks.

[cmanley]

Most fans in real PC applications have to push air under resistance. Most cases have filters that resist air flow. Other devices such as hard disk enclosures usually have very small openings through which air must be sucked.
It would be nice to see silent fans tested under resistance too because there are some fans such as the NOCTUA NF-S12 SERIES that are silent but I'm sure will fail hopelessly under resistance.

I think fans which have blades with a smaller angle of attack (and therefore less CFM under no resistance) and larger surface area will be more effective. Thick fans having blades with large angles of attack are more likely to aerodynamically stall when the air is resisting flow meaning low CFM and just a swooshing of air in circles.

Knowing which fan pushes the most air under resistance with the lowest RPM is what will ultimately define the most silent fan in practical uses..