Originally Posted by Artikbot
Static pressure is the force the fan applies onto the surface the air is directed to.
Generally speaking, the static pressure only matters when moving air thru a heatsink or a radiator, since the more force it applies, the deeper the air can reach, and the faster it will reach.
If the fan is just for ventilation, then you only need CFMs, since you don't care how strong the air column is, but you do care on how much air is moved.
Ok... On the above, this was part of my thought process but needed confirmation.
And no, more pressure doesn't mean less speed. What gives the pressure is the pitch of the fan blades, in other words, the thicker the fan, the higher the pressure. Some blade designs, like Scythe's Gentle Typhoon outperform by far other fans of its size in pressure, because the GT's blade design picks air from the center, compresses it pretty hard, and then sends it to the blade tips, which increase its speed. That makes a pretty high static pressure for a common 25mm fan.
Ok... this helps me understand the why of higher pricing on better SP'ed fans. Better engineering basically.
The Ultra Kazes, also from Scythe, have a very high static pressure value because they pick air and compress it all along the blade, which has got a very high pitch grade. It is also thicker than normal fans (38mm).
And generally, when fans are placed very close to their target equipment (such as fans in a radiator), what determines their performance is the tip stall spressure value. Yep, more or less like a propeller in an airplane.
If your fan moves shizloads of air, but it stalls on high pressures, it won't be any good for a radiator, since once the blade stalls, the fan moves zero air. And if the tip has stalled, the whole blade will stall unless the center of the fan still picks air, in that case more air will be sent to the tips and therefore the fan will not stall.
Let me see if I understand this correctly then... a low static pressured fan would have it's "airflow" bounced back at it by a radiator negating the initial flow of air causing the fan to stall? A high static pressured fan would just push through (not at 100% obviously) the radiator fins.
Returning to the Ultra Kazes, those ones are very good for radiators (also VERY loud) because they need massive pressures for their tips to stall, basically because the motor has got craploads of torque, and because the blades are thick and short (less friction ergo less power wasted in moving air from center to blade tips).
-Heatsinks: High pressure average air volume.
-Case fans: Low pressure high air volume.
This seems to sum it up for me basically... Thanks.
Remember that higher the pressure higher the noise, so you have to find the balance between those.