Flow measurement


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Flow measurement

  1. 1. Flow measurement Manojkumar Maurya ME – 13906 Heat power engg.
  2. 2. Introduction • 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. • The selection of the proper instrument for a particular application is governed by many variables, including cost. • Flow-rate-measurement devices frequently require accurate pressure and temperature measurements in order to calculate the output of the instrument. • The most widely used flow metering principle involves placing a fixed area flow restriction of some type in the pipe or duct carrying the fluid. This flow restriction causes a pressure drop that varies with the flow rate. • Thus, measurement of the pressure drop by means of a suitable differential-pressure pick up allows flow rate measurement.
  3. 3. Flowmeters • Devices used to measure flow rate: – Venturi meter (based on pressure difference) – Orifice meter (based on pressure difference) – Rotameter (based on drag forces) – Pitot tube – Magnetic (magnetic field is used to measure flow rate) – Ultrasonic (ultrasonic waves are used to measure flow rate) – Turbine flow meter
  4. 4. Venturimeter
  5. 5. Continued… • The venturi flow meter is an obstruction flow meter due to which pressure drop occurs • Pressure drop is given by : • Discharge is given by: • C  discharge co-efficient
  6. 6. Orifice Meter • Using bernoullis principle we have,
  7. 7. • Volume flowrate is given as:
  8. 8. Rotameter • Rotameters are devices for direct measuring of the flow of moving fluid • The main elements of its construction are a transparent conic pipe 1 and a float , made of a conic tip 2, a cylindrical body 3 and a board 4 • The value of the quantity measured is defined by the height of float going up. • The rotameters have found wide application in practice due to their simple construction, distinct indications along a linear scale, possibility to measure small flows of fluids and gases,including aggressive ones, sufficiently wide range of measuring, etc
  9. 9. Pitot tube • The Pitot tube is a simple device that allows for the measurement of the flow pressure in a moving fluid • It also works on Bernoulli’s principle
  10. 10. • Applying Bernoulli's equation we get: • Now from above equation we get, • We can calculate the velocity and multiplying it with the area will give the flow rate
  11. 11. Magnetic flow-meter
  12. 12. • It is based on Faraday’s law of electromagnetic induction • An electrical current (I) is applied to a coil package inside the flowmeter • As a result, a magnetic field (B) is created across the metering pipe • When a conductive liquid flows through the magnetic field, a small voltage (u) is induced • This voltage is proportional to the velocity of the flow and is accurately measured by two stainless steel electrodes mounted opposite each other inside the metering pipe • The two electrodes are connected to an advanced electronic input circuitry which processes the signal and in turn feeds it to the a microprocessor inside the electronics module • The microprocessor then calculates the volumetric flow and controls the various outputs on the terminal board
  13. 13. Thank you