1. ENTC-303Dr. Alvarado1 Flow Measuring Devices

2. ENTC-303Dr. Alvarado2 Flowmeters Devices used to measure flow rate: –Venturi (based on pressure difference) –Orifice Plate (based on pressure difference) –Rotameter (based on drag forces) –Coriolis (measure mass flow rate) –Magnetic (magnetic field is used to measure flow rate) –Ultrasonic (ultrasonic waves are used to measure flow rate)

3. ENTC 303PROF. ALVARADO3 Manometers The height of a liquid column or difference of height of two columns is used to measured the pressure:

4. Venturi Effect The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section of pipe. -The Venturi effect is a jet effect; as with an (air) funnel, or a thumb on a garden hose, the velocity of the fluid increases as the cross sectional area decreases, with the static pressure correspondingly decreasing. ENTC-303Dr. Alvarado4

5. ENTC-303Dr. Alvarado5 Venturi Meter

6. Orifice Plate An orifice plate is a device used for measuring the volumetric flow rate. It uses the same principle as a Venturi nozzle, namely Bernoulli’s principle which states that there is a relationship between the pressure of the fluid and the velocity of the fluid. When the velocity increases, the pressure decreases and vice versa. ENTC-303Dr. Alvarado6

7. ENTC-303Dr. Alvarado7 Orifice Meter

8. ENTC-303Dr. Alvarado8 Rotameter -Pressure difference is constant in the rotameter -Peripheral velocity is constant -To maintain a constant velocity, the cross sectional area must vary -This variation of cross sectional area occurs as the float moves up and down the rotameter.

9. Rotameter (cm) A (mm)B (mm)C (mm)E (mm)F (mm) Time to Fill (s) Mass Flow(kg/s) CvCv CdCd 18 16 14 12 10 Average: Rotameter (cm) Calculated Venturi m (kg/s) Calculated Orifice m (kg/s) Error Venturi Error Orifice H L Venturi (mm) H L Orifice (mm) 18 16 14 12 10

10. ENTC-303Dr. Alvarado10 References en.wikipedia.org/wiki/Venturi_effect en.wikipedia.org/wiki/Orifice_plate www.orificeplates.com www.omega.com