For turbulent flow (NRe > 2100) of low viscosity fluid (μ > 20cp) in steel pipes, the optimum inside pipe diameter is given by (where, Q = fluid flow rate, ft<sup>3</sup>/sec.ρ = fluid density, lb/ft<sup>3</sup>.μ = fluid viscosity, centipoise D<sub>i</sub> = optimum inside pipe diameter, inches)
Correct Answer: D<sub>i, opt</sub> = 3.9 Q<sup>0.45</sup>.ρ<sup>0.13</sup>