Noctua working on a better 12cm fan

RaptorZX3 · Post by **RaptorZX3** » Sat Aug 11, 2007 3:25 am

ok i asked the Noctua employee and he said they are working on a "better" 12cm fan that will create more air pressure, this fan will be better for CPU heatsink with tight fins and PSU fan replacement.

this one won't be as silent as the NF-S12 series, but it'll have more air pressure. so it'll be perfect for a PSU that need more air pressure.

s_xero · Post by **s_xero** » Sat Aug 11, 2007 5:11 am

Well, it would be stupid if it's more noisy...

Why the hell should that be the case?!

bonestonne · Post by **bonestonne** » Sat Aug 11, 2007 10:26 am

actually, that will be great, because at lower speeds it will be perfect.

do you know if it'll produce more pressure at all speeds, or just 12v?

if the air pressure is a constant [as in always more than current fans] at any speed, then it would work much better.

Felger Carbon · Post by **Felger Carbon** » Sat Aug 11, 2007 11:26 am

bonestonne wrote:if the air pressure is a constant [as in always more than current fans] at any speed, then it would work much better.

There is this thing called conservation of energy that has to be observed. Now, we all know by now that the energy in the airflow thru the fan is proportional to the cube of the air velocity.

What the fan does is produce pressure and airflow. The pressure is maximum at zero airflow, and the airflow is maximum at zero pressure (which means all the pressure created by the fan blades is used to accelerate the air from stationary to moving, with nothing left over for any other air resistances (or airflow impediments, if you prefer).

Work is pressure time movement, in this case airflow. Now, CFM (airflow) is linear with RPM to a first order approximation. The energy of the moving air is directly proportional to the cube of the CFM, for a given fan. What's missing is an RPM squared component to conserve energy.

How lucky for us that the pressure of a given fan is proportional to the RPM squared! It makes all the numbers balance, and energy is conserved (as we all knew must be what happens).

Alas, pressure is not independent of RPM. In fact, it's proportional to the RPM squared.

RaptorZX3 · Post by **RaptorZX3** » Sat Aug 11, 2007 11:50 am

before i talked about this to the Noctua employee, i was asking him if the company would team-up with another to make a silent PSU with their 12cm fan, like Seasonic and Noctua.

maybe they took my idea and decided to make a 12cm fan that would do better cooling for a PSU and tighter-fins heatsinks.

since a PSU need a fan more like the Nexus-type with more air pressure and airflow...

cpemma · Post by **cpemma** » Thu Aug 16, 2007 5:50 am

Felger Carbon wrote:Alas, pressure is not independent of RPM. In fact, it's proportional to the RPM squared.

For a given fan, but isn't the pressure problem with the current Noctua largely "the unusually wide clearance between the blade tip and the frame â€” intended to reduce turbulence noise" (SPCR review), which I can see also reducing its ability to generate the pressure of a more conventional design. So by the Law of No Free Lunch, they can get more pressure at the expense of more noise.

Felger Carbon · Post by **Felger Carbon** » Thu Aug 16, 2007 8:49 am

cpemma wrote:
Felger Carbon wrote:Alas, pressure is not independent of RPM. In fact, it's proportional to the RPM squared.
For a given fan...

Right. I was posting about conventional fans, over 95% (99%?) of which have surprisingly similar blade pitch. The Noctua 120mm fan is an outlier in that it has a very high pitch; the 13-blade "big fan" is an outlier with a very low pitch.

According to reports I've read, the Noctua works very well pushing lots of air in open, low-resistance (to airflow) environments. Put it in a case with some serious airflow resistance and it fails miserably. The 13-blade "big fan" is specifically designed to deal with higher airflow resistance and so does a very good job in real-world case environments, while the 7-blade "big fan" considerably outperforms it in a completely open, caseless environment.

To the best of my knowledge, my comment about pressure being proportional to the RPM squared is, to the first order, applicable to all fans including the outliers. It's just that other things then grab your undivided attention...