1. A centrifugal pump has the following characteristics
|
Q (m'/min)
|
0
|
7
|
14
|
21
|
28
|
35
|
42
|
49
|
56
|
|
H (m)
|
40.0
|
40.6
|
40.4
|
39.3
|
38
|
33.6
|
25.6
|
14.5
|
0
|
|
11 CA)
|
0
|
41
|
60
|
74
|
83
|
83
|
74
|
51
|
0
|
This pump is used to pump water from one reservoir to another through a pipe of length 125 m, diameter 40 cm, and friction factor 0.0054. The difference in height of the water levels in the reservoirs is 20 m. Neglecting separation losses,
(i) Find the flow rate and head delivered by the pump.
(ii) Find the power supplied by the motor driving the pump
2. A centrifugal pump recorded the following performance for pump tests run at l500rev/tnin.
|
Water flow, Oh
|
0,075
|
0,150
|
0,200
|
0,250
|
0,300
|
|
Head, m
|
70
|
68
|
64
|
53
|
49
|
|
Input power, kW
|
97
|
127
|
147
|
163
|
170
|
|
|
The pump was lrnown to perform well at the high heads and low flow rates required with a previous application. The pump is now to be uscd with much lower head conditions and higher flow-rates. The user is concerned about power consumption and efficiency. When used to pump water at these new conditions the centre-line of the pump is 4m vertically above the lower waterreservoir and 30 vertically below the upper water level ro which it pumps. The piping used has f= 0,006, is 0,3m internal diameter throughout and is of length 20m and 200m on the suction and delivery sides respectively.
Using graphical means, determine the delivery flow rate and head of the pump at its rated speed of 1500r/min
what speed the pump should operate at to keep the power just below 200 kW and what the overall efficiency is at this speed.