VENTURIMETER
DEFINITION:
Venturimeter is a
device used for measuring the rate of
flow of a fluid flowing through a pipe.
It consist of three
parts,
• Converging
part
• Throat
• Diverging
part
WORKING PRINCIPLE
Venturimeter works under principle of
·
Bernoulli's equation
· Continuity
equation.
TYPES OF VENTURIMETER
1.
Horizontal venturimeter
2.
Vertical venturimeter
3.
Inclined venturimeter
VENTURI METER V/S FLOW
When a
venturimeter is placed in a pipe carrying the fluid whose flow rate is to be
measured, a pressure drop occurs between the entrance and throat of the
venturimeter. This pressure drop is measured using a differential pressure
sensor and when calibrated this pressure drop becomes a measure of flow rate.
MANOMETER
The differential pressure sensor
used here is Manometer.
Manometer is
a device to measure pressure.
A
common simple manometer consists of a U shaped tube of glass
filled with some liquid
OPERATION
The fluid whose flow rate is to be
measured enters the entry section of the venturi meter with a pressure P1.
As the fluid flows into the converging
section, its pressure keeps on reducing and attains a minimum value P2 when it
enters the throat. That is, in the throat, the fluid pressure P2 will be
minimum.
The Manometer attached between the entry
and throat section of the venturimeter records the pressure difference (P1-P2)
which becomes an indication of the flow rate of the fluid through the pipe when
calibrated.
The diverging section has been provided
to enable the fluid to regain its pressure and hence its kinetic energy. Lesser
the angle of the diverging section, greater is the recovery.
Formula
used
where ,
Q=
discharge (rate of flow)
H=
differential head
Cd=
coefficient of discharge
a1=
area of inlet section
a2=
area of throat section
g=
gravitational acceleration
n=
0.5(appr.)
APPLICATIONS
· It is used where high pressure recovery is required.
· Can be used for measuring flow rates of water, gases,
suspended solids, slurries and dirty liquids.
· Can be used to measure high flow rates in pipes having
diameters in a few meters.
ADVANTAGES
· Less
changes of getting clogged with sediments
· Coefficient
of discharge is high.
· Its
behaviour can be predicted perfectly.
· Can
be installed vertically, horizontally or inclined.
DISADVANTAGES
· Highly
expensive
· Occupies
considerable space
· Cannot
be used in pipes below 7.5cm diameter.
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