"Static Pressure Fans" Don't Exist!

You've probably heard it said many times, and some manufacturers even give their fans this designation, but it's essentially meaningless. Axial fans are volume flow devices, and they can develop extremely low levels of static pressure when installed on heatsinks or radiators. In this video, the first of a series, I demonstrate what static pressure is and why it's silly to refer to axial fans as "Static Pressure" devices.

[@EndOfForever]

This channel was exactly what I was looking for. Air flow is difficult for me to understand, but you do an excellent job explaining.

[@FanPhys]

Thank you - I really appreciate that. Whilst fluid mechanics is a very complex domain of physics, there are some principles we can quite easily learn by testing the various aspects of PC cooling. :)

[@cukkaSG]

Why is this watched only 800? I've been looking for a video like this from 3 months. Thank you.

[@FanPhys]

You're welcome - thanks for watching!

[@ThantiK]

Maybe no 'static pressure axial fans' but squirrel-cage fans are absolutely designed for static pressure. This does actually matter in instances where you're buying datacenter GPUs for AI image generation, and they have really loooooong sets of fins, boxed in completely. If you don't have enough static pressure - i.e. by using a squirrel cage fan, then air simply doesn't manage to work through the fins and remove air at all. Meanwhile, squirrel-cage fans, have substantially lower CFM than axial fans.

[@FanPhys]

Yep I'm aware - I made a couple of videos comparing axial vs. blower fans. This series is specifically about gaming PC fans that are falsely advertised as "high static pressure fans".

[@or2kr]

I kinda felt the urge to cover some aspects of this topic as well, even though I have exactly zero experience and ideas on how to present my thoughts, so very eager to see what you will cover

[@Y4k407]

Brilliant vid, at last a good honest series on fans without all the bro science faff

[@FanPhys]

Thank you - I've felt for a long time that it's needed, and I hope I can do it justice!

[@masterTigress96]

Very good video. I subscribed and am looking forward to seeing more! Take care and happy holidays.

[@FanPhys]

Thank you very much! :)

[@ydihtty]

I left a comment that I think got marked as spam, it had a link to Noctua's "NF-A12x25: Performance comparison to NF-F12 and NF-S12A" article which seems relevant

[@FanPhys]

Thanks for the suggestion - I'll definitely include it in my next video :)

[@ArsenicShooter]

Very interesting ! Would you do a comparison of different fans by static pressure ? It's not always easy to find this information and to make sure it is accurate.

[@Hdtjdjbszh]

Ive noticed that having a sealed chamber or "tunnel" between my fans and heatsink has always yieled better noise and cooling resulted, is this related to pressure?

[@FanPhys]

Yep using a shroud can improve performance with axial fans - I'll be testing this in a future video as well. The noise attenuation is likely because of a reduction in turbulence and is especially noticeable when you move a fan a small distance from the mesh of a case panel. Ultimately, everything to do with fluid flow is related to pressure of one sort or another, but it's extremely complex! :)

[@volkanislek]

Hi Major, I built a filter for my 3D printer with HEPA Filter + Active Carbon Filter + 12mm Fan (pulls air). Fan specs says its nearly 4mm H2O static pressure which is not enough to pass air from HEPA (only a little breeze). So when I run fan, it can't suck air from filter, instead fan sucks air from center of exhaust side and blows it from blade's tips. I have a few questions if you can help. Which can give more static pressure, pulling or pushing air from fan? (I can reorder as fan (blows) + HEPA + Active Carbon if blow is better). Is there a way to prevent exhaust turbulence to increase static pressure? Any idea to increase static pressure? (low budget)

[@gadgetdeez7069]

You completely ignore pitch and the effects on flow vs pressure. It's like gear ratio on a vehicle. A low gear ratio will accelerate quickly but have a low top speed. A high gear ratio will not accelerate very well but has a much higher top speed. Fans are the same way. Yes both gear ratios make torque. But the ratio between torque and speed are different. Same for a fans capable max flow and max pressure at a given rpm. A fan capable of more static pressure at lower over all flow may be better when met with resistance as the flow is less likely to fall off. Where as a high flowing fan with little capability to generate pressure used with a restrictive setup would substancially lose airflow. Much like a person climbing a hill on a bike with a low gear may slow slightly but will climb the hill, but the same guy on a bike with a high gearing will lose substancial speed climbing the same hill and likely not even be able to make it should the setup be incorrect enough. Take each fan, dead head the box. Test all the fans at 1500 rpm and see what the "static pressure" is. Blades with more overlap typically have less "leakage" and are capable of generating more pressure. Fans with less overlap tend to leak a lot and are better for low restrictive flow. This is a major thing in automotive cooling fans as they impede airflow at speed. The more overlap the fan blades have, the more surface area they consume, the more pressure they typically will generate given that they have an acceptable pitch. In reverse they also obstruct more air as well. Which is why a lot of performance fan shrouds have flap doors to allow air to bypass the fan.

[@FanPhys]

I think it's worth clarifying that the main purpose of this video series is to demonstrate that so-called "static pressure optimised" fans are not what they claim to be. Yes there can be very minor optimisations, but these are generally not pressure or airflow optimisations at this scale and in the given RPM range of 1000-2000. I have tested all of my fans at 1600rpm and, lo and behold, the ones dubbed "high pressure" fans by the community (Gentle Typhoon & A12x25) perform the worst by a considerable margin. These fans are optimised primarily for low noise, which is why they are so popular. I'll discuss this and more in the second part of this series.

[@LogioTek]

Hey you made a wind tunnel! Did you seal the edges/seams with glue or epoxy? Might not matter for relative pressure testing but steal eliminating some leaks is a cherry on a top after making a setup like this. I guess it's all about pressure/flow at certain dBA levels. That's the real differentiator.

[@FanPhys]

Yep all the openings are sealed with epoxy, and there's a rubber gasket at the front plate because I intend to have different plates for different sized fans - 140mm in particular, but possibly 92mm as well. And you're right that tiny amounts of pressure escaping from the box won't make much difference, fractions of 1Pa, but it's always good to be thorough. Next video I will probably touch on the matter of noise/performance. :)

[@LogioTek]

@@FanPhys Awesome! Thanks! Being an engineer myself, I really enjoy these videos.

[@branchprediction9923]

@@LogioTek I enjoy them too, keep em coming FanPhys.

[@calebgrefe8922]

It feels similar to the "is it the voltage or amperage that kills you?" question. The question really just doesn't make any sense. It's like asking if it's the 3000lbs or the 60mph that kills you if you get hit by a car.

[@christophrechtlehner]

This video contains no information about your claim, there is comparison or any other kind of data for proof.

[@LordElfa]

But what's the point? Why make them when they aren't more expensive and their existence just confuses consumers? I mean you're here talking about this like it's a conspiracy but if so, it's a conspiracy for its own sake and that doesn't make sense.

[@FanPhys]

Nothing quite so serious as a conspiracy, but it is false advertising. Consumers aren't confused because broadly they just believe what's advertised and stump up the cash. I didn't produce this series to save people money... it was more to shed some light on the science behind static pressure, which is fascinating.

[@Bobis32]

what is the volume of air getting pushed through the heat sinks is the real question for whether its optimized for air flow or pressure you need to take the pressure measurement after the restriction as well to see the loss of airflow

[@FanPhys]

There's no such thing as "optimized for airflow" or "optimized for pressure"... they are marketing hooks designed to make you buy specific products. Axial fans = volume flow at low pressure. Blower fans = volume flow at high(er) pressure.

[@MakinComputers]

😎🤯