Why do fans (and propellers) have different numbers of blades? What advantage is there to more or less blades?

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An actual question my five year old asked me and I couldn’t answer, please help!

In: Physics

25 Answers

Anonymous 0 Comments

A lot of great answers here, mostly talking about super high-powered propeller setups.

I would like to add one thing though that I haven’t seen mentioned, and that’s air pressure. Sometimes, you need a lot of air moved, but moving it too fast would be bad/wasteful. Static pressure is important for Radiators, where maintaining a temperature is more important than simply pushing air through. The shape of the fan blades will tell you a lot about the function. Short, wide, and far apart? That’s meant for air flow. Long, curved, and close together? That’s for Static pressure.

You can use the wrong fan and still be fine. It’s an efficiency thing.

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