3 Hydrodynamics
195
Storage well
1-1
0
0
Suction
pipe
Water
pump
Pressure
piping
Piezometric head
line
water
tower
4-4
z s
z
2-2
3-3
Fig. 3.22 Water pump system
datum
p a
γ
= z s +
p 2
γ
+
α 2 V 2
2
2g
+ h w1−2
z s =
p a − p 2
γ
−
α 2 + λ
L
d
+
ξ
V 2
2
2g
Because the vacuum degree at the front section 2-2 of the pump cannot
be greater than the allowable vacuum value h v of the pump, the maximum
installation height z s of the pump is
z s ≤ h v −
α 2 + λ
L
d
+
ξ
V 2
2
2g
The hydraulic calculation of the pressure pipeline mainly determines the
lift and installed capacity of the water pump. The diameter of the pressure
pipe is determined by the economic speed. Now, the energy equation between
section 1-1 and section 4-4 is established
H P = z + h w1−4 = z + h w1−2 + h w3−4