Explain briefly the significance of the "specific speed" of a centrifugal or axial-flow pump. A pump is designed to be driven at 10Hz and to operate at a maximum efficiency when delivering 0.4m3/s of water against a head of 20m. Calculate the specific speed. What type of pump does this value suggest? A pump built for these operating conditions has a measured overall efficiency of 70%. The same pump is now required to deliver water at 30m head. At what speed should the pump be driven if it is to operate at maximum efficiency? What will be the new rate of delivery and the power required? marks) 16 Question Three A pump developing a pressure of 800kN/m2 is used to pump water through a 150mm pipe 300m long to a reservoir 60m higher. With the valves fully open, the flowrate obtained is 0.05m3/s. As a result of corrosion and scaling the effective absolute roughness of the pipe surface increases by a factor of 10. By what percentage is the flowrate reduced? Viscosity of water =1mNs/m2. (13 marks)