Friction loss in water systems primarily occurs due to what factor?

Friction loss in water systems primarily occurs due to contact with surfaces. As water moves through pipes, it interacts with the surfaces of those pipes. This interaction leads to resistance against the flow, creating friction loss. The roughness of the internal surface of the pipes, along with the length of the pipe and the velocity of the water, contributes significantly to how much friction loss will occur. Therefore, the contact that the fluid has with the pipe surfaces plays a crucial role in determining the overall friction loss experienced in a water system.

While factors like water temperature, pipe diameter, and fluid viscosity can also influence the behavior of the fluid and, indirectly, the friction loss, they do so in a more nuanced manner. Water temperature affects viscosity, pipe diameter changes the cross-sectional area through which water flows, and fluid viscosity describes the thickness of the liquid; however, it is ultimately the interaction and contact between the water and surfaces of the pipes that is the primary cause of friction loss.