On Sunday, May 28, 2017 at 11:35:39 AM UTC-4, wrote:


This is where I have trouble. Assuming these are regular centrifugal turbines, the outlet of the first stage is fed into the axis of the second stage. The pressure from the first-stage outlet is retained at the second-stage inlet, but from there it feeds into the whirling blades of the second stage, the outlet volume of which is LARGER than the inlet volume between any two blades.



Obviously, I'm missing something here, but I haven't yet seen what it is.

Ed Huntress

You are over thinking the situation. A multistage pump has a bunch of identical sections all turning at the same speed. Each stage increases the pressure. So you might have a 6 stage pump with each stage increasing the pressure by 10 psi. Which makes for a fairly efficient pump which will supply water at 60 psi. Google it.

In Eric's case it is a little different. He wants to circulate water. The system is pressurized to 80 psi and the pump has 80 psi on the input. The output is at 90 psi into a heating loop. and the friction of the water flow reduces the pressure so that at one end of the loop you have 90 psi and at the other end you have 80 psi. The pumps are not in series.

Dan


Consider connecting the pump to the bottom of a 180 foot tall (approx
80 psi head) tank. Will the pump be capable of pumping, at the
specified flow, to a height of 23 feet (10 psi head) or 203 feet?

Practical matters of seal design aside.



--
Ned Simmons