Venturi meters use a restriction in a pipe to measure fluid flow rates. They have a converging section that narrows to a throat and then diverges again. This creates a pressure difference that can be used to calculate flow rate. Venturi meters have no moving parts, a small head loss, and do not easily clog. They work by applying Bernoulli's theorem between the inlet and throat, where the flow velocity increases and pressure decreases in the throat. Venturi meters can measure flow rates of various liquids and gases and are useful for high flow rates in large pipes, though they are large in size.

1. VENTURI METER
Presented By:
•Ateeb Ahmed
•Syed Ali Ikram
•M. Iqbal Awais
•M.Waleed Mushtaq
1

2. Flow measuring devices:
 The measurement of fluid flow is important in
applications ranging from measurements of blood-
flow rates in human artery to the measurement of
liquid oxygen in a rocket.
 Some sort of restriction is placed in the pipe or duct
carrying the fluid. This flow restriction causes a
pressure drop that varies with the flow rate.
2

3. Venturi Meter:
 A venturi meter is a variable head meter, which is used
for measuring the flow rate of a fluid through a pipe.
 In this meter, the fluid is gradually accelerated to a
throat and then gradually retarded in diverging section
where the flow channel expands to the pipe size.
 Venturi meters have only a small head loss, no moving
parts and do not clog easily.
3

4. Working principle:
 By reducing the cross-sectional area of the flow passage,
a pressure difference is created and the measurement of
the pressure difference enables the estimation of the
flow rate through the pipe.
4

5. Oggy and the cockroaches
5

6. Construction:
A venturi meter consists of following three parts:
1. A short converging conical part
2. Throat and
3. Diverging conical part
6

7. 7

8. 8
= density of fluid
A1 = area of inlet pipe
A2=area of throat section


9. 9

10. Coefficient of discharge:
 Ratio of Actual mass or volumetric flow rate to
theoretical mass or volumetric rate .
 It encompasses all the energy losses taking place
during flow through venturi meter.
 Its value depends upon the reynolds number and
ranges from 0.95 to 0.98
10

11. Working equation for venturi
meter:
G = Cd ρC ́
Where
Cd= coefficient of discharge
ρ = density of the fluid
and
C ́ is constant for a meter and is equal to 2
2
2
1
21
AA
AA

By applying Bernoulli’s theorem at the inlet and throat
sections, the relation for flow rate can be dervied as:
02gh
11

12. Applications:
 It is used where we are working
with small pressure head.
 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.
 It doesn’t clogs easily.
12

13. 13

14. Limitations:
 They are large in size and hence where space is limited,
they cannot be used.
 Expensive initial cost, installation and maintenance.
 Cannot be used in pipes below 7.5cm diameter.
 Cannot be altered for measuring flow rate upto a wide
range.
14

15. References:
 Unit Operations of Chemical Engineering -7e by
Mccabe
 industrial instrumentation and control by sk singh
 Coulson & Richardson's Chemical Engineering
Fluid flow, heat transfer and mass transfer.
Volume 1
 And our very own
www.google.com
15

16. Any Queries ?
16