The point of the "Static Pressure" spec?

[niels007]

Hey all,

While ordering some parts to silence a friends pc, I saw the site also sells those 16 blade turbine 120mm fans. The specs say that the static pressure is 0.035 inch H2O. That's all well, but the Papst catalogue shows the 4412 fan to have about 0.08 inch H2O static pressure, but thats 1600rpm, so at 950 (the speed of the turbine fans) it would be 0.0475.
Now, the turbine fans are advertised with 'high static pressure', but its considerably less than the 7 blade Papst!

Does anyone know the static pressure of a Nexus or Yate Loon fan? Perhaps more importantly, how important is this value? Does it have significant meaning when blowing on a tightly finned heatsink? Is it relevant for the direction the fan is blowing at, or does it apply to the suck in side as well?

[mathias]

I would assume that the point of it is to give marketing something to bullshit about, just like with other manufacturer's specs.

Papsts are said to have better static pressure even if all other things(ie blade number, thickness and speed) are equal. But I don't know if that's enough to beat a 16 blade fan.

It is important in highly restrictive environments.

[cpemma]

The specs say that the static pressure is 0.035 inch H2O. That's all well, but the Papst catalogue shows the 4412 fan to have about 0.08 inch H2O static pressure, but thats 1600rpm, so at 950 (the speed of the turbine fans) it would be 0.0475.

It's not a linear relationship with RPM. Pressure varies with the square of the speed ratio, so half speed gives quarter pressure. The Papst will be around 0.028" @ 950rpm.

[niels007]

Doh! of course 'pressure' should've made me realize that an area is involved.. So it does have a higher static pressure. The main reason for asking is that I have this Thermal<censored> Sonic Tower here, which seems to work best with the fan sandwiched between the two towers, for which extra static pressure might help considerably..

[ckolivas]

Assuming you use the same RPMs from one fan to the other, then yes the extra static pressure would be helpful. That's exactly the point of showing that measurement.

[datapappan]

Since we're into silence here, what's the SPL spec? Normally, Papst fans are very quiet for the equivalent flow rate/static pressure spec.

/datapappan

[ckolivas]

From the sounds of the description he's probably talking about the aerocool turbine fan which I have 2 of.
http://www.aerocool.com.tw/p-accessory/ ... %20fan.htm

For what the spec is worth the claim is Noise: 19.66 dBA at top speed of 950 rpm.

Having owned quite a few fans... I can say this probably not far from the truth. I tend to use them at about 300-600rpm though.

Their major disadvantage is they tend not to blow in a nice stream so if you try to direct their airflow at something it isn't very good unless it is flush against it. As case and PSU fans they work great though.

[niels007]

Its still hard to get an idea of the amount of effect that this value has..

For example, sandwiched between a Thermaltake Sonic tower, with intake and output restrictions, try a Papst, Nexus and Turbine all at exactly the same RPM and see if there is a considerable cooling difference..