Half a croissant, on a plate, with a sign in front of it saying '50c'
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Efficient fan

A fan shaped like a submarine propeller
 
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Most fans that stand on the floor have three or four big, flat blades and a cover around the middle of the shaft. I can't quite see how this design moves much air. How 'bout one with, say, eight blades at a steeper pitch angle, which meet at the centre if the fan. That way, more air could be moved and the little plastic disc in the middle could be disposed of. Baisically, the same design that submarine propellers use for efficiancy and silence. I suppose it would need some more weight in the base to counteract the extra thrust though. I believe (Not sure) that the more blades it has, the fewer RPMs needed for the same volume of air, so it would be slower and quieter.
Aegis, Aug 12 2003

Reminded me of this article http://www.memagazi.../helios/helios.html
[Worldgineer, Oct 21 2004]

[link]






       What's long, hard, and filled with seamen?
DeathNinja, Aug 12 2003
  

       (-) because a propeller is designed to move water, a fan is designed to move air. More blades at a steeper angle would move more air but this is probably not done due to reasons of cost/power consumption/strength etc. In my opinion this is not really an original idea.
chud, Aug 12 2003
  

       what [chud] said, surely the fan company would have hired the services of an undergraduate engineer to do a bit of fluid dynamics ?
neilp, Aug 12 2003
  

       Ditto [chud] - sub props are designed for efficiency and reducing cavitation over a wind band of speeds. They also must generate a fairly narrow propulsion stream.   

       Fan blades are designed to shift air, not water. They are pitched for high efficiency and shaped to reduce tip vortices. The propulsion stream should be diffuse to cool a wider area.   

       Unlike marine and aviation props, efficiency is not a big selling point for domestic cooling fans. If you want to develop a better fan, work on reducing noise. You might look into feathered tips and trailing edges, or wider blades that operate at lower speeds to minimise noise at a given flow rate.   

       Also, you can make existing fans work better. Make sure your fans are helping to circulate cool/ fresh air, rather than blowing more hot stale air in your face.
FloridaManatee, Aug 12 2003
  

       i though this would be some scheme to ship all manchester united supporters to manchester.
pjd, Aug 13 2003
  

       Do a search for industrial ventilation fans, you'll find lots of fans that fit this description.
Freefall, Aug 13 2003
  

       So this isn't about rah-rah-rahing* for a favourite team, as in "RAH!" instead of rah-rah-rah(?)   

       *The "h" is still silent
thumbwax, Aug 13 2003
  
      
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