venturi_meter ppt(2)

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: A short converging conical part Throat and Diverging conical part 6

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8. 8 = density of fluid A 1 = area of inlet pipe A 2 =area of throat section

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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 = C d ρ C ́ Where C d = coefficient of discharge ρ = density of the fluid and C ́ is constant for a meter and is equal to By applying Bernoulli’s theorem at the inlet and throat sections, the relation for flow rate can be dervied as: 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

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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