basic flow instrumentation

1. BASIC FLOW INSTRUMENTATION
AND VENTURIMETER
subject: Process ControlandAutomation
Aishwarya D
Madan Y N
Departmentof BiotechnologyEngineering
AcharyaInstituteof Technology
Soladevanahalli,Bengaluru 560107

2. Contents:
 Instrumentation
• Types of instrumentation
• Temperature measurements
• Flow measurements
 Venturimeter
• Introduction
• Principle
• Diagram
• Construction
• Working

3. Instrumentation
that branch of science which deals with
control and measurement of physical
properties of matter like solid liquid and gas

4. Types of Instruments:
• Mechanical
• Electrical
• Electronics
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5. Temperature measurements
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thermocouple

6. Flow measurements
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7. Introduction:
A Venturimeter is a device used for measuring
the rate of flow of a fluid flowing through a pipe.
It is also called as venturi flowmeter. It is used
to calculate the velocity of fluids running
through a pipeline. The fluid may be liquid or
gas.

8. Principle:
It is based on Bernoulli’s equation that is the velocity
head increases in an accelerated flow by reducing the
cross sectional area of the flow passage. Due to which
the pressure head is reducing at that section, a pressure
difference is created which enables to the determination
of the discharge through the pipe.

9. “
Diagram:
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10. Construction:
It has three main parts:
1.Short converging part: It is a tapered portion whose
radius decreases as we move forward.
2.Throat: It is middle portion of the venturi. Here the
velocity of the fluid increases and pressure
decreases. It possesses the least cross section area.
3.Diverging part: In this portion the fluid diverges.
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11. Working:
The venturimeter is used to measure the rate of flow of
a fluid flowing through the pipes.
1. Here we have considered two cross section, first at the
inlet and the second one is at the throat. The difference
in the pressure heads of these two sections is used to
calculate the rate of flow through venturimeter.
2. As the water enters at the inlet section i.e. in the
converging part it converges and reaches to the throat.

12. 3. The throat has the uniform cross section area and least
cross section area in the venturimeter.
4. Now there is a pressure difference of the fluid at the two
sections. At the section 1,the pressure of the fluid is
maximum and the velocity is minimum. And at the
section 2 ,the velocity of the fluid is maximum and the
pressure is minimum.
5. The pressure difference at the two section can be seen in
the manometer attached at both the section.
6. This pressure difference is used to calculate the rate flow
of a fluid flowing through a pipe.

13. Here,
a1, a2 = Area of cross-section at inlet and throat
g – Acceleration due to gravity
h – Pressure head difference
Cd = Coefficient of discharge
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14. Applications:
1.Aviation:
To measure the speed of the air around the plane.
2.Automotive:
To measure the fuel and air distribution in carburettor
3.Medical:
To measure the Volume flow of blood through vessels.
4.Chemical:
To measure the Flow rate of chemical through pipes.
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16. THANKYOU