Question

A multistage pump is required to deliver water to a head of 50 m at flow rate of 0.1 m^3/s. A motor rotating at 1800 rpm is available. Determine the optimal number of stages for the pump.

Answer 1

Answer:

number of stages for the pump is 4

Explanation:

given data

water head Hm = 50 m

flow rate r = 0.1 m³/s

rotating N = 1800 rpm

to find out

optimal number of stages for the pump.

solution

we consider here specific speed does not exceed more than 82

so Ns formula will be

Ns = $\frac{N\sqrt{r} }{H^{3/4}}$

here Ns id 82 and N is rotating and r is flow rate

so

82 = $\frac{1800\sqrt{0.1} }{H^{3/4}}$

so H = 13.23 m

so

number of stage n is

nH = Hm

n = $\frac{50}{13.23}$

n = 3.77 ≈ 4

so number of stages for the pump is 4