What is the performance or noise difference between a curved blade or straight blade electric cooling fan? I see that the straight blades put out a little more CFM...are they louder?

 

yes the straight blades are louder. Got something to do with speed of sound. I am installing 2 12" curved blade fans. The CFM is not directly related to blade shape, thats more size and speed.

 

curved blades are more efficient creating less turbulence and less noise

 

put some sidepipes on and you won't even know the difference b/w fans.

 

well, here's some morning rattle: by "curved" blade, assume varying pitch and/or curved leading edge. one would expect a varying pitch (like a propeller) and a curved blade to move more air, but it may not. As the diameter gets smaller, the less these features impact performance. when a wing, or propeller, gets below about 4" leading to trailing edge, a flat plate has as much lift as a profile wing. To make up for less diameter, the fan must turn faster. a feature like attaching a ring to the blade tips will make up some capacity for loss in tip speed; the ring also makes the fan quieter i believe. Also consider that the fans make some noise, but the motors also make a lot of noise. Generally, the more rpm required (smaller diamter fan), the more noise-fan and motor. i had a professor who was studying these design issues on small automotive fans, before CFD was "cheap", and there was a lot of trial and error. i suspect that not much has changed even with CFD. somebody doing research and design in this area would probably tear this up, but maybe this will get it started. sorry not able to give direct anwer, but as you research, you should find a pattern with the fan diameter, blade shape/profile, number of blades, noise, rpm, other design features, and capacity. Remember that fan speed or RPM impacts capacity to a point. if an advertised fan capacity falls outside an obvious pattern, it probably is too good to be true. measuring noise is a difficult science and will probalby have to depend on subjective data from members. Something like my "describe aftermarket corvette fan installation here" is quieter/louder than my "describe late model car here", would be great info. i wish i had numbers to put with this, but don't. hope someone has hard numbers. good luck. . .

 

Are you running for office?

 

well now there is some bit of meat in there!!!

i thought few would reply to thread, but when i hit submit, i was last in line!!! was just trying to add a little to a subject where Godel's theorem may apply (any mathematicians out there correct me if incorrect use of); sorry for the typing frenzy!!!
NOT running for office!!! trying harder to run from office; maybe i'm going at this all wrong . . . anyway, thanks for reading

 

 

I'd say the curved blades are quieter. Ever see the prop on a nuclear sub? They don't use straight blades, and being quiet is the name of their game.