Question

Friction loss in turbulent flow Type I problem: Use Figure 6.10 to determine the head loss per 100 ft for water flowing at 60 gallons per minute in a nominal 2-inch ID commercial steel pipe (you need to find actual ID from Appendix A.2 table). Use the density and viscosity given in our text for water at 68 ?F.

Answer 1

For 2 in nominal dia

Inside dia = 2.067 in

Velocity = volumetric flow / area

= [(60 gal/min x 1min/60s x 1m3/264.172gal)] / [(3.14/4 * (2.067 in x 1m/39.37in)² ]

= 1.75 m/s

Reynolds number = diameter x velocity x density / viscosity

= (2.067 in x 1m/39.37in) x (1.75 m/s) x (1000 kg/m3) / (1 cP x 1Pa-s/1000cP)

= 91878.3

Re > 4000

Flow is turbulent

Surface roughness of steel pipe

e = 0.015 x 10^-3 m

Dia D = 0.0525 m

Relative roughness = e/D = 0.015 x 10^-3 /0.0525

= 0.0002857

Friction factor from moody_chart

f = 0.019666

From Darcy Weisbach equation

head loss

hf = 4 f L v² / D x 2g

= [4 x 0.019666 x 100 ft x 1m/3.28ft x (1.75m/s)² / (0.0525 m x 2 x 9.81 m/s2)

= 7.13 m = 23.39 ft

Head loss per 100 ft of water = 0.2339 ft