Fan Laws

[80251]

One law I follow with my Delta AFB1212SHE fans..... 1.6a with 150 cfm....

Don't get your finger near them.

I'll see your Delta AFB1212SHE and raise you one Delta FFB1312EHE 127x38mm: 2.47A and 179.75CFM to 200 CFM.

 

[Shrek]

Wouldn't reach any meaningful conclusions with those tables. The laws don't hold for different fans unless they were of the same design (i.e. same impeller shape and material), only varying in rotational speed or diameter (and quite limited int the case of the latter).

Exactly, I will work within a series

 

[Hankieroseman]

Somebody say Fans?

This fan makes too much heat though

 

[claes]

If I read the graph correcly , @ 30% PWM the fan does 1000 rpm with 30 dB(A) fan noise.
There is not an exact datapoint at 2000 rpm , it falls between datapoints @ 70% and 80% PWM.
2000 rpm is about 75% PWM , and i read the corresponding noise of 44 dB(A) on the graph.

It is not exactly 15 dB , but I think it is a fair approximation.

I think you are misreading? The first chart is in high speed mode, but kind of hard to read.

High performance mode (first chart)
1000rpm = 33dB
2000rpm = ~54dB

Scroll down a bit and you get measurements at fixed RPMs in intermediate mode in nice clean tables.

750rpm = 27.2dB
1500rpm = 36dB

 

[freeagent]

Anyone know of any good 180x38s?

 

[Jacky_BEL]

I think you are misreading? The first chart is in high speed mode, but kind of hard to read.

High performance mode (first chart)
1000rpm = 33dB
2000rpm = ~54dB

Scroll down a bit and you get measurements at fixed RPMs in intermediate mode in nice clean tables.

750rpm = 27.2dB
1500rpm = 36dB

I only looked at the 3rd graph since it is the only one with data about fan noise.

 

[claes]

I see, I misread

You can see the other measurements in the charts below

 

[Jacky_BEL]

I see what you mean.

Maybe because these are sound measurements of a fan blowing through a radiator?
Whereas the formula i had was for a fan only scenario?
And we are looking at different ranges of operation?

 

[Steevo]

Fluid flow dictates twice the flow requires 4X the pressure, air is a fluid.

 

[Jacky_BEL]

Here is another set of "fan laws" I found.
Capital N means noise, in dB I assume.
50 log(2) almost equals 15 , so +15 dB for doubling the speed.
Same as the previous speed vs noise equation I had.

This 15 dB difference when doubling RPM is a recurring theme.
It stems from "aerodynamic noise increases with the fifth power of the rotor speed".

 

[Deleted member 185158]

I'll see your Delta AFB1212SHE and raise you one Delta FFB1312EHE 127x38mm: 2.47A and 179.75CFM to 200 CFM.

But my fan header doesn't support the current draw

But I'd love them and the extra CFM.

 

[80251]

Anyone know of any good 180x38s?

The only manufacturer of 180mm fans I've come across is silverstone. The SST-AP182 is a dual ball bearing fan that has the dimensions: 180mm (L) x 180mm (W) x 32mm (H). They're somewhat expensive too.

Digikey doesn't have any 180mm DC fans listed, 172mm seems to be the closest I could find.

 

[claes]

Silverstone is on the AP184i now, too. Think they have six or so models

Fractal does, too, but imagine that’s what @freeagent is trying to replace

Edit: Ohhh forgot about enermax, too, but I don’t know if they still produce them

Double edit: thinking about it Phobya had one, too, and maybe EK? @VSG had reviewed a bunch on their old site but unfortunately it’s no longer live

 

[Deleted member 185158]

The only manufacturer of 180mm fans I've come across is silverstone. The SST-AP182 is a dual ball bearing fan that has the dimensions: 180mm (L) x 180mm (W) x 32mm (H). They're somewhat expensive too.

Digikey doesn't have any 180mm DC fans listed, 172mm seems to be the closest I could find.

If I remember right, my Antec 900 had a 200mm fan on the top.

 

[Shrek]

"aerodynamic noise increases with the fifth power of the rotor speed".

That is scary stuff

 

[1100R]

Anyone know of any good 180x38s?

I use a pair of Silverstone Air Penetrators with an Alphacool radiator

 

[Durhamranger]

How many ways to reinvent the wheel ??

 

[DeathtoGnomes]

How many ways to reinvent the wheel ??

the left wheel or the right one?

 

[Deleted member 185158]

the left wheel or the right one?

The square wheel of course. XD

 

[Shrek]

My variables for these fan laws...

Fan Law 1:
CFM = C fan Move
If CFM >= 1 = Fan is on.

Fan Law 2:
SP = Some power = is better than none.
IF SP <= 1 = more fans needed.

Fan Law 3:
HP = Half Power = CFM
IF HP =/= 1 than HP = CFM/2 = less noise.

Rinse/Repeat.

Are you saying half power gives rise to half flow rate?

 

[Vayra86]

I wonder if there is a similar law for noise production.

Yes, for decibel/sound pressure increases, especially in the bass frequencies, you need exponential power for the same increase every step of the way.

That's why in bass production bigger equals better.

Also in general:
"One decibel (0.1 bel) equals 10 times the common logarithm of the power ratio."

Decibel (dB) | Definition, Formula, & Facts | Britannica

Decibel (dB), unit for expressing the ratio between two amounts of electric or acoustic power or for measuring the relative loudness of sounds.

www.britannica.com

 

[Jacky_BEL]

Are you saying half power gives rise to half flow rate?

No , he is just pulling your feet with a load of nonsense low quality post.

 

[DeathtoGnomes]

Are you saying half power gives rise to half flow rate?

less noise actually.

No , he is just pulling your feet with a load of nonsense low quality post.

humor for smart people failed it seems.