Problem 6.24

6.25 Water pump pumps water into two tanks, as shown in Fig.6-42, elevations of the water pool and water tank are H1=2m and H2＝4m respectively, inner diameter of the pipe is d1＝d2=20cm, pipe lengths are l1＝40m, l2=45m, friction factors are ?1=?2=0.02, pump’s head of delivery is Hp=20m, and neglect minor loss. Find: (1) pump’s discharge; (2) when the overall efficiency of the pump is ?=70%, how much is the power which is transmitted to the pump by the motor driving the pump?

如图6－42所示，泵将水池中的水打入两水箱，水池与水箱水面的高度各为H1=2m，H2＝4m，圆管内径d1＝d2=20cm，管长l1＝40m，l2=45m，沿程

损失系数?1=?2=0.02，泵的扬程Hp=20m，不计局部损失。试求 (1) 泵的排水量；

(2) 当泵的总效率?=70%时，带动泵的电动机输给泵的功率应为多少？ Fig.6-42 Problem 6.25

((1) 0.57m3/s (2) 159.6kW)