<Li> ρ (\ displaystyle \ rho) is the density of the fluid (unit in l b m f t 3 (\ displaystyle (\ frac (lb_ (m)) (ft ^ (3)))) or k g m 3 (\ displaystyle (\ frac (kg) (m ^ (3))))) </Li> <P> In particular the shear stress at the wall can, in turn, be related to the pressure loss by multiplying the wall shear stress by the wall area (2 π R L (\ displaystyle 2 \ pi RL) for a pipe with circular cross section) and dividing by the cross-sectional flow area (π R 2 (\ displaystyle \ pi R ^ (2)) for a pipe with circular cross section). Thus Δ P = f L R ρ u 2 (\ displaystyle \ Delta P = f (\ frac (L) (R)) \ rho u ^ (2)) </P> <P> This friction factor is one - fourth of the Darcy friction factor, so attention must be paid to note which one of these is meant in the "friction factor" chart or equation consulted . Of the two, the Fanning friction factor is the more commonly used by chemical engineers and those following the British convention . </P> <P> The formulas below may be used to obtain the Fanning friction factor for common applications . </P>

Difference between fanning friction factor and darcy friction factor
find me the text answering this question