flow calcs

It will depend on what your aim is:

max dP, max velocity is just two obvious criteria

When you have choosen than then you must select a design value (eg. 0.5 bar/100 m or max. velocity 1 m/sec)

Best Regards

Morten

If you are looking for an equation that relates Q to dP/L then combine the following found in Crane TP-410

Q = 236*d^2*sqrt[dP/(K*p)] and K = (f*L)/d
or
Q = 236*sqrt[(dP/L)*{d^5/(f*p)}]

where
Q gpm
dP delta Pressure psi
L length ft
d diameter inch
f friction factor, dimentionless, per Moody chart or from Crane TP-410 chart for turbulent flow.
p specific weight lbs/ft^3