# Fluid mechanics suction question

In centrifugal pumps why diameter of delivery pipe is smaller than suction pipe????

It might have to do with Bernoulli's principle , The smaller outlet will have a higher flow velocity and reduced pressure . But I am not 100% positive.

cjl
It's more to do with simple continuity. Centrifugal pumps deliver fluid at a higher velocity than they intake, so assuming incompressibility (a decent assumption for pretty much all applications with centrifugal pumps), the diameter at the outlet must be smaller than at the inlet since the volumetric flowrate is unchanged and the velocity has increased.

gmax137
... Centrifugal pumps deliver fluid at a higher velocity than they intake, ...

Well, pumps deliver at higher pressure than they intake. The outlet piping velocity will be dependent on the outlet pipe area (due to continuity), not the other way around.

The reason inlet piping is usually larger diameter than outlet piping is to minimize pressure losses upstream of the pump, in order to ensure the pump has adequate net positive suction head (to minimize cavitation in the pump).

cjl