"The Standard Handbook of Engineering Calculations "
gives the Poiseuille formula for head loss in pipes with laminar flow.
If I correctly interpret the figures given in brackets as the metric formula
Pd = 10^-4 x l x u x G / d^4
Pd is pressure drop (kPa ) l is pipe length, ( ? ) U is absolute viscosity ( Pa s ) G is flow rate ( l / s ) d is pipe diameter ( cm )
Is this correct, and should the pipe length be in meters ?
What is the conversion factor from cP ( centipoise ) to Pa s ( Pascal seconds ) ? I think 1000 cP = 1 Pa s but I'm not sure.
to further confuse me :-) the "Handbook of Chemistry and Physics " ( aka, the rubber handbook ) gives Poiseuille as
V = ( (Pi) x p x r^4 ) / ( 8 x l x ( Eta) )
V = volume flow ( cm^3 / s ) l = pipe length ( cm ) r = pipe radius ( cm ) p = pressure loss ( dynes / cm^2 ) ( Eta ) = viscosity ( Poise = dyne s / cm^2 )
What I really want is the formula in SI units.
I'm prity certain I have got a factor that's a fraction of (Pi)^4 missing from the first equation.