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Ultrasonic Flowmeters

M Suresh, CRE.

m.suresh@fcriindia.com

F l u i d C o n t r o l R e s e a r c h I n s t i t u t e

Bringing Research Resources to Industry

Coverage

• Basic Requirements in Flowmeters

• Ultrasonics and its behaviour in media

• Flow measurement principles by

Ultrasound

• General Installation criteria

• Diagnostics

� High Accuracy

� High Turn-Down Ratio

� Low Cost

� Low Pressure Loss

� No Moving Parts

� Ability to Calibrate

� Easy Integration with Piping System

� Resistant to Corrosion and Erosion

� Low Sensitivity to Dirt or foreign Particles

� High Accuracy

� High Turn-Down Ratio

� Low Cost

� Low Pressure Loss

� No Moving Parts

� Ability to Calibrate

� Easy Integration with Piping System

� Resistant to Corrosion and Erosion

� Low Sensitivity to Dirt or foreign Particles

Desirable: A Flowmeter that has..

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1. Coriolis vibrating tube

2. Electro-magnetic

3. Flow Nozzles

4. Orifice plate

5. Venturi

6. Elbow Tap (Elbow Meter)

7. Pitot Tube

8. Velocity-Area Averaging

9. Positive Displacement

10. Reciprocating Piston

11. Oval Gear

12. Turbine

13. Nutating Disk

14. Rotary Vane

15. Target

16. Thermal Dispersion

17. Ultrasonic Doppler

18. Ultrasonic Transit Time

19. Variable Area

20. Vortex

21. Swirl

22. Fluidic Oscillation

(Coanda Effect)

23. Cross-Correlation Method

Flow Metering in Conduits

Ultrasonics• Ultrasound: sound of frequency > 20 kHz

• A sound wave is a pressure disturbance that

travels through a medium by means of particle-to-

particle interaction.

• Speed of wave depends upon properties of the

medium.

� inertial properties (e.g density)

� elastic properties (e.g Modulus of Elasticity)

• �����, � = λ; Speed = frequency x wavelength

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• Generated using piezo-electric materials.

• Piezo-electricity:

� Observed as occurrence of electric dipole moments

in crystalline solids

� Charge accumulates in crystal in response to

applied mechanical stress

� Conversely, applying electric potential causes

material to undergo deformation

Piezo-electricity

• First demonstrated by Pierre Curie and Jacques

Curie, 1880

• Naturally occuring materials:

� tourmaline, quartz, topaz, cane sugar, Rochelle

salt (sodium potassium tartrate tetrahydrate)

• Converse piezo-electicity: Gabriel Lippmann, 1881

• Woldemar Voigt , 1910: Lehrbuch der Kristallphysik

(Textbook on Crystal Physics)

Piezo-electric Materials

• Paul Langevin, 1917, developed ultrasonic

submarine detector

• World War II: piezoelectric constants for synthetic

materials (ferroelectrics) >> natural materials

• Piezo Ceramics e.g. barium titanate (BaTiO3), lead

metaniobate (PbNb2O3), lead zirconate titanate

(PZT), etc.

• Polymer material e.g. PVDF

Piezo-electric for Ultrasonics

Acoustic impedance

piezoelectric ceramics 2.6 × 10.7kg/m2s,

air 4.3 × 10.2kg/m2s.

Match acoustic impedance by bonding acoustic matching

layer to piezoelectric ceramics