Dix, there were a few points i highlighted that may have not been easily grasped. sorry for saying too much here, but i'll briefly review the main points:
1) calculating CFM vs RPM is difficult, but very possible.
2) the calculations require higher education, but fundamental aerodynamic ideas that make up the calculations can still be conceptualized by the uneducated (or so i believed).
3) flow geometry around blades (angle of attack) is most important to the calculations.
4) fan blade angle of attack are designed to peak in efficiency at their rated RPM
5) running fans off of this design RPM makes fan blades operate off of the design angle of attack
6) off design angle of attack creates noise & inefficiency
7) filters & other restrictions ad the complexity of friction to the calculations (without major bluff-body obstructions, Fanno friction is insignificant & blade drag dominates)
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