HD350-EU-EN V3.1 07/13
15
Useful Equations
Calculating the Area for rectangular or square ducts
Rectangle: Area (A) = Height (b) x Width (a)
Circle: Area (A)
=
x
r
2
(Where
=
3.14
and r
2
=
radius x radius)
Cubic equations
CFM (ft
3
/min) = Air Velocity (ft/min) x Area (ft
2
)
CMM (m
3
/min) = Air Velocity (m/sec) x Area (m
2
) x 60
NOTE:
Measurements made in
inches
must be converted to
feet
or
meters
.
a
b
r
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