A pump draws water from a well and discharges it to a water tank as shown at
Question:
A pump draws water from a well and discharges it to a water tank as shown at the rate of 9m3/h or2.5 × 10−3m3/s. The pump is installed on a platform 10 m into the well. The platform is hs = 2m from the water level. The end of the inlet pipe extends hi = 4m from the water level into the water. The minor loss coefficient at the foot of the inlet pipe is 10 due to a filter. The length of the pipe from the outlet of the pump and the entrance to the tank is 150 m. The discharge pipe opens into the base of water tank which is Hd = 42m from the ground level and contains Ht = 6m of water. Minor loss coefficient due to exit into the tank is 1. The diameters of both the suction and discharge pipes are 50 mm. Ignore all other minor losses. Assume the pipe is smooth (surface roughness = 0).
(a) The pump head required.
(b) The power supplied to the pump assuming pump efficiency of 90%.
(c) NPSH available. Neglect minor losses in the bend in the inlet line.
(d) Use the same friction factor from above to obtain the equation for the system curve of the form Hs = Hs0 + βQ2.
(e) The attached document on Page 14 shows the specification for a pump. Determine the equation of the pump curve of the form Hp = H0 − αQ2for the 150/150 impeller of the NMD 25/190 pump operating at 3450 rpm.
(f) Determine the operating point, the efficiency, the power consumed by the pump and the NPSH required (you can read the last three of the pump chart. The efficiency is in dotted lines in the top chart, the power required is in the middle chart and the NPSH required is in the bottom chart).
Relevant values for water at 30oC: Dynamic viscosity: µ = 8 × 10−4Pa s, Vapor pressure: 4.2 kPa (absolute). Use the following approximation for the friction factor for turbulent flow in pipes. f =0.25/[ log10 (ε/D)/3.7 + 5.74Re^0.9]^2 where f is the friction factor, Re is Reynold’s number, ε is the surface roughness, and d is the diameter of the pipe. Friction factor for laminar flow is f = 64/Re
Fundamentals of Hydraulic Engineering Systems
ISBN: 978-0136016380
4th edition
Authors: Robert J. Houghtalen, A. Osman H. Akan, Ned H. C. Hwang