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Unread 03-26-2003, 11:42 AM   #79
Graystar
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Join Date: Mar 2003
Location: Brooklyn, NY
Posts: 112
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Quote:
Originally posted by bigben2k
Hum...

so if cross section is irrelevant, the water would be raised/lowered by 30 mm, no matter what the diameter...

...but if the diameter is say, 1 meter, the volume of water moved would be 0.024 cubic meters, which is 24 liters, which weighs 24 kg.

If the diameter was 2 cm, then the volume of water would be 0.0000094248 cubic meters, which is 0.009425 liters, which weighs 0.009425 kg, aka 9.4 grams.

Given that the fan will produce a fixed amount of force, the diameter very much makes a difference.

Am I wrong?
I think you're just having a temporary short in your brain, 'cause you know this already

Pressure is not dependent on volume. Your 100 PSI air pump will fill a truck tire to 100 PSI just like it will fill a bicycle tire to 100 PSI. Just takes a lot more pumping!

That little pump will fill the city pool up to 30mm deep. It may take a couple years, but it will do it. That is the nature of centrifugal pumps. These pumps maintain a constant pressure, regardless of flow rate. That's in direct contrast to displacement pumps, which move specific volumes of water regardless of pressure (to a point, of course.)
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