Question 4
For the pumping system shown, the pressure gauge in the discharge pipe (which has negligible
length) reads 40 kPa when cavitation is about to begin at the inlet of the pump. The barometric
pressure is 100 kPa, and water temperature is 20°C.
(a) Determine the water flow rate, assuming negligible losses in the discharge pipe and exit nozzle.
(b) Calculate the length of the pipe from the reservoir to the pump for this operating condition, if
the losses due to friction in this pipe can be expressed as (0.035 L / D)[$V^2$ / (2 g)], where L is
pipe length, D its diameter, and V is the flow velocity, and other losses (in pipe fittings, entrance,
nozzle, etc.) are negligible.
(c) Calculate the required pump power.
170 mm-diameter pipe
nozzle
50 mm
pump
5 m
110 mm-diameter
discharge pipe
Reservoir
Water at 20°C
