Formulae for fan spec calculation

Computer Hardware and electronics in general.
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reparto
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Joined: 27 May 2013, 11:30
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Formulae for fan spec calculation

Post by reparto »

Doing some research work with some fans and came across these formulae in a book:

Airflow law:
Fan airflow is proportional to its RPM
Airflow1/Airflow2 = RPM1/RPM2

Static pressure law:
Static pressure is proportional to the RPM squared
SP1/SP2 = (RPM1/RPM2)^2

Horse power law (the book was old enough that horse power was still a thing :D):
HP1/HP2 = (RPM1/RPM2)^3

I know the first one is correct, I haven't had the chance to verify the others but I have been assured they are generally correct. Note that this only works if you use the same fan, you can't use different fan rpms and airflows.

Using this you should be able to calculate the specs of fans outside of whatever values they give and whether or not they are lying on the packaging.
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