Question

A pump curve provided by a manufacturer is given by h = 20[1 − (Q/100)2] where h is the head provided by the pump in meters and Q is the discharge in liters per minute. The system curve for a pumping application is

h= 5+0.002Q2 (Q in liters per minute).Find the Operating point (Q) for

•           one pump

•           two pumps connected in series

•           two pumps connected in parallel

Answer 1

Operating Point is calculated at the intersection of head curve and system curve.

h = 20[1 − (Q/100)2] ................ (1)

h= 5+0.002Q ................ (2)

Equating (1) and (2)

20[1 − (Q/100)2] = 5+0.002Q .............. (3)

Q = 250/7

1. Operating point (Q) for one pump

Q = 250/7

2. Operating point (Q) for two pumps in series

Qtotal = Q1 = Q2  ; Htotal = H1 + H2

Q = 250/7

3. Operating point (Q) for two pumps in parallel

Qtotal = Q1 + Q2  ; Htotal = H1 = H2

Q = 250/7 + 250/7 => 500/7