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Old Jun 02, 2011, 12:14 AM
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The hole thru the nose of the impeller will cause air to "leak" from the high pressure side (downstream) to the low pressure side. So I think this will actually draw air thru the back of the motor, over the windings, through the slots in the bearing hub, and back into the input side of the fan, providing internal cooling (reverse flow) air, but at the cost of power and efficiency. I wonder how these fans would rate with this hole blocked ... and also whether blocking the hole would cause an appreciable increase in motor temp (the motor is externally cooled by the flow of air so it may not need "internal" cooling). Bear in mind, the motor consumes as much energy as 2 60W bulbs, of which most is lost as heat although not clear how much heat is generated inside the motor vs in the compression of the air (as Dr Kiwi shows not too much is converted to thrust, ie kinetic energy of the air). That is a lot of heat in a small (plastic) space. So perhaps the motor would get fried without the vents. For $28, it's worth a try though.
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