Question

5.9.2.A pump delivers water at 20°C between a reservoir and a water tank 20 m higher. The suction side contains an entrance strainer (Kstrainer = 2.5), three of 90° bends with R/D = 2 (see pg 57 of Chap 3 slides for minor loss coefficient for bend), and a ductile-iron pipe with 10 m length and 25 cm diameter. The discharge side includes a 160-m-long, ductile-iron pipe, 20 cm in diameter, and a gate valve. The friction factor (f) for the whole pipeline is 0.02,the net positive suction head is given as 7.5 m, and the design discharge is 170 L/sec. Determine the allowable elevation difference between the pump and the reservoir water surface to avoid cavitation. [12]

Fig: 1