I have been tasked with finding a suitable replacement for: FD-FAN-VENT-HF14-WT
The specifications are really throwing me though, the airflow being 118.2 CFM or 200.8 m3/h at 1200RPM. Nothing that I can find in other manufacturers ranges (Corsair, bequiet!, Noctua) even compares at 1200 RPM to this fan.
Is it that the airflow value changes at different static pressures? For example the Noctua NF-P14s has a higher static pressure of 1.29 mm H2O thus a low airflow reading. Where as Fractal have a static presure of 0.95 mm H2O.
Or am I completely misreading this?
Any help would be greatly appreciated.
Kind regards,
Tim Earl
I tried to include links to the manufacturers product pages for ease but the forum system wouldn’t allow me.
Usually on sales sites for consumer type fans the following is reported:
max static pressure at 0 airflow
max airflow at 0 static pressure
Yes the airflow changes with the static pressure. Imagine you hold your hand to block a tube where air comes out. You have have zero airflow but the pressure rises.
I recently bought some delta fan and there the manufacturer gives some diagram between static pressure and airflow.
@gysi nailed it. The pressure/flow numbers are given at the extremes. You should be able to take these 2 points, and plot a line, but it’s been a long time since high school math…
y = -0.00475x + 0.95
or
x = ( y - 0.95 ) / -0.00475
Fans are usually pushing against something, so lets assume a 0.5 mm H2O pressure drop. Do some math and you get these flows at that pressure drop.
A14: 106 m^3/h
HF14: 95 m^3/h
At 0.25 mm H2O they flip.
A14: 123 m^3/h
HF14: 147 m3^3/h
So what’s actually the best performing fan is going to depend a lot on variables you probably can’t even measure. 1 mm H2O is less than a 10,000th of standard sea level air pressure. Basically none of this matters, computer fans are wimpy as hell.
Do not focus on the speed too much, different fan impellers have different performance and noise. Generally speaking, few flatter wider fan blades can spin faster for the same noise level and they are more geared towards building pressure. This is just a general rule of thumb though. and of course, a given fan blade gets noisier as it spins faster.
As explained before, the published static pressure is at 0 flow and the published airflow is at 0 pressure. Any grill, heatsink or radiator will bring you some resistance (i.e. necessitate some pressure to pass through) and based on the amount of resistance you will reach a working point for each fan. The fan with the highest published airflow is not necessarily the best. The performance curve (also called P/Q Curve) mentioned before is what you need, though to be honest, you would need the P/Q curve of your resistance (i.e. whatever you put in the airflow and try to get air passing through) and this is hard to get.
For the speed, although it gives you a general idea, it can not be compared from one fan to another, for instance, ARCTIC F12 at 1300 RPM is noisier than its brother ARCTIC P12 at 1800 RPM. Performance is generally better for the P12 except when you have no resistance.
A P14 (or equivalent) would be a perfect replacement for your case.
By the way, the performance curves of the ARCTIC’s fans are in the website with the manual https://support.arctic.de/p12/docs (called P/Q Curve)
That’s cool as hell, I didn’t know Arctic published any of that data. Giving me data that I can evaluate to make an informed decision is how you win me as a customer.
