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FLOW MEASUREMENT DEVICES

FLOW MEASUREMENT DEVICES. VENTURIMETER. VENTURIMETER. INTRODUCTION. In this meter the fluid is accelerated on expense of static pressure by its passage through a converging cone of angle 15-20 degree.

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FLOW MEASUREMENT DEVICES

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  1. FLOW MEASUREMENT DEVICES

  2. VENTURIMETER

  3. VENTURIMETER

  4. INTRODUCTION • In this meter the fluid is accelerated on expense of static pressure by its passage through a converging cone of angle 15-20 degree. • The pressure difference between the upstream end of the converging cone and the throat (minimum area section) is measured. • Throat length = throat diameter • The fluid is then retarded in a cone of smaller angle 5-7 degree in which large proportion of kinetic energy is converted back to pressure energy.

  5. VENTURIMETER

  6. PRINCIPLE USED Bernoulli's Principle same as orifice meter P↓ = V ↑

  7. DISADVANTAGES • Highly expensive in installation & replacement • Space requirement is more

  8. ADVANTAGES • High pressure recovery • Less possibility of becoming clogged due to smooth surface • Suited for large water flow • High coefficient of discharge

  9. VENTURIMETER SECTIONS • CONVERGING CONICAL SECTION • THROAT • DIVERGING SECTION

  10. CONVERGING CONICAL SECTION • Angle of converging conical section is about 21 ± 2 degree. • Velocity ↑ and static pressure ↓

  11. THROAT • Cylindrical section of Minimum Area • At this section V = MAX and P = MIN • Throat diameter = 0.25 – 0.5 of inlet diameter

  12. DIVERGING SECTION • Change of stream area back to the entrance area • Kinetic energy is converted into pressure rise in this section • Angle of diverging section is about 5-7 degree • Angle is kept less to having least tendency of flow separation from boundary of this section • With small angle length and cost ↑

  13. INTERESTING REASONING QUES. Why mercury is preferred as manometric fluid? • Good conductor of heat • Shining quality provide clear visibility • Mercury does not evaporate easily • Mercury's freezing point is much lower(-38.72 deg C) • More sensitive than water to the changes in the atmospheric pressure • Mercury is relatively denser than water • Does not stick on the walls of the tube of manometer, resulting in accurate measurements • Large temperature expansion coefficient

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