Fluid Flow
BERNOULLIS EQUATION
Now we can use the Extended Bernoulli equation to determine the required pump head.
z1
v2
1
2g
P1n1
gc
g
Hp
z2
v2
2
2g
P2n2
gc
g
Hf
Hp
(z2
z1)
v2
2
v2
1
2g
(P2
P1) n
gc
g
Hf
65 ft
0.178
ft
sec
2
0
ft
sec
2
2
32.17
ft lbm
lbf sec2
0 ft
2 ft
Hp
67 ft
The student should note that the solution of this example problem has a numerical value that
"makes sense" from the data given in the problem. The total head increase of 67 ft. is due
primarily to the 65 ft. evaluation increase and the 2 ft. of friction head.
Application of Bernoullis Equation to a Venturi
Many plant components, such as a venturi, may be analyzed using Bernoullis equation and the
continuity equation. A venturi is a flow measuring device that consists of a gradual contraction
followed by a gradual expansion. An example of a venturi is shown in Figure 6. By measuring
the differential pressure between the inlet of the venturi (point 1) and the throat of the venturi
(point 2), the flow velocity and mass flow rate can be determined based on Bernoullis equation.
Figure 6 Venturi Meter
Rev. 0
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HT-03