Friction loss in pipelines is a function of which factors?

• A. Pipe diameter
• B. All of the above
• C. Pipe length
• D. Roughness and velocity

Answer: (B)

Friction loss in a pipe is influenced by several interacting factors that determine how much energy is lost as water flows. Larger diameter pipes reduce losses because, for the same flow, the water velocity is lower and wall shear is smaller, and the discharge path is easier to push water through. The longer the pipe, the more distance there is for energy to be dissipated by friction, so head loss increases proportionally with length. Rougher pipe interior increases the friction factor, causing more resistance to flow and higher losses. And higher velocity means more shear at the pipe wall and greater turbulence, which boosts energy loss; in common formulas friction loss rises with velocity (or flow rate) as velocity increases.

Since all of these factors play a role, the best answer is that all of the above contribute to friction loss.