A pipe is 25 km long and 80 mm bore diameter. The mean surface roughness is 0.03 mm. It carries oil of density 825 kg/m3 at a rate of 10 kg/s. The dynamic viscosity is 0.025 N s/m2.

 A pipe is 25 km long and 80 mm bore diameter. The mean surface roughness is 0.03 mm. It carries oil of density 825 kg/m3 at a rate of 10 kg/s. The dynamic viscosity is 0.025 N s/m2.

 Determine the friction coefficient using the Moody Chart and calculate the friction head. (Ans. 3075 m.)

 Solution

Q = m/ρ = 10/825 = 0.01212 m3 /s

 um = Q/A = 0.01212/(π x 0.042 ) = 2.411 m/s

 Re = ρud/µ = 825 x 2.4114 x 0.08/0.025 = 6366

 k/D = 0.03/80 = 0.000375 

 From the Moody chart Cf = 0.0083

 hf = 4 Cf L u2 /2gd = 4 x 0.0083 x 25000 x 2.41142 /(2 x 9.91 x 0.08) = 3075 m