What is a venturi meter and how does it work

What is a venturi meter and where is it used

A venturi meter is a device that can be used to measure the fluid flow in a pipeline. The flow velocity of the fluid can also be increased by using a venturi meter. A venturi meter can increase the velocity and decrease the pressure of the fluid. Venturi tubes are flow meters that are used in the place where the permanent pressure loss is needed and they are also used when maximum accuracy is needed in case of high viscous liquids. The structure of the venturi meter is like two conical plates. This device is a variable head meter. It can also be used to check the flow rates of slurries, gases, water, suspended solids, and dirty liquids. This device can also be used to measure high flow rates.

What are the parts of a venturi meter and how venturi meters are constructed? What is throat in venturi meter

A venturi meter is mostly manufactured by using aluminum, and it has three major parts, they are a short converging part, throat, and a diverging part. The short converging part would make the fluid converge and throat is situated between the converging and diverging part and the throat is a small section of a circular pipe and it is the middle part of the venturi meter and the cross-sectional area is very small when compared to the other two. The diameter of the throat remains the same through its entire length the throat diameter must be kept in a suitable value if its diameter is very low then it will decrease the pressure and because of this cavitation could happen. The diverging part is the last part of the device and it is connected to the outlet pipe. The angle of the diverging part is less than the converging part and because of this, the diverging cone is larger than the converging cone. Because of the small diverging angle, it can minimize or prevent certain loss of energy due to the flow separation of walls and eddies

How does a venturi meter work and their operating principle


The operation of the venturi meter is based on Bernoulli’s equation. It states that the flow of an incompressible fluid has constant energy at any point. So when velocity increases the pressure decreases, so the flow velocity can be increased by using venturi meter and that is why venturi meter is constructed in a certain way so that it can increase the velocity. As explained earlier the throats cross-sectional area is less than that of the inlet and it would increase the flow velocity through the throat so the pressure will be reduced, so there is a pressure difference between the inlet and the throat of the venturi meter and this pressure difference is measured the measurement can be done by using a differential manometer. By measuring the pressure difference between the inlet and port we can calculate the flow rate of the pipe.

What does a venturi meter do

This meter will measure the fluid flow and it narrows the flow of the fluid and measures the pressure of the fluid before narrowing and also at the narrowing time too. The meter checks the pressure difference between the two readings. So the fluid flow can be calculated.

What is the difference between venturi meter and orifice meter

  • Different flow rates can be achieved by using orifice plate but in case of venturi meter it is not possible because of fixed throat diameter
  • There is no energy loss in venturi meter because of its shape while in orifice meter pressure drop is high
  • Orifice meter is cheap and can be easily installed, while the venturi meter is expensive and maintenance is hard
  • The orifice head loss is greater than venturi meter, and the power loss of the orifice will be high when used for pipelines which carry fluid for a long time, so because of this orifice is used for testing purposes
  • There is power loss while using orifice meter but it is still used because it can be altered. But in the case of venturi meter, it is not possible so venturi meters are only used for permanent installations.

How should we select a flow meter

  • It should be selected according to the fluid type
  • According to the viscosity and fluid temperature
  • Pressure drop
  • According to the type of flow
  • Maximum and minimum flow rate

What are the advantages of venturi meter

  • It has a low-pressure loss
  • The recovery of pressure is really good than orifice meter
  • Venturi tubes can be used for certain dirty and slurry applications
  • The effect of viscosity is high
  • High discharge coefficient
  • It can be installed as we like, vertically, inclined or horizontally
  • This flow meter is more accurate
  • It can be easily operated

What are the disadvantages of venturi meter

  • High cost
  • It is difficult to inspect
  • It cannot be used below 76.2mm pipe size
  • It takes more space so it can be used in less space
  • Maintenance is very hard

What are the applications of venturi meter

  • It is used in the robotic fueling system
  • It is used in pressure tanks
  • It can be used with small pressure heads
  • It can measure the flow rate of water, slurries, gases, and slurries
  • It can measure high flow rates in pipelines
  • It is used in the medical field, to measure the rate of flow in the arteries
  • It is used in carburetors
  • In medical oxygen therapy venture masks are used
  • Compressed air operated industrial vacuum cleaner
  • Plumping
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