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The turbine metre, the orifice metre, the rotameter, and the venturi metre are just some metres often used to gauge fluid movement. Each metre works by altering a physical characteristic of the fluid motion and then allowing this modification to be measured. The flow is again matched to the observed change. The fluid’s rate of flow via a conduit is measured using venturi metres. Bernoulli’s principle is used in this scenario. The equation is used in the Venturi metre hypothesis, which states, “when the pressure lowers, velocity will also rise.” Venturi metre works on the principle of Bernoulli’s Theorem.
Who invented the venturi metre?
Giovanni Battista Venturi formulated the theory of the Venturi metre in 1797. Clemen Herschel invented the device in 1899.
Venturi metre Construction
The section of the larynx, as well as the deviation, are made up of three components. These three sections are arranged in a logical sequence. An entrance section, also known as a converging zone, is the first. The cross-section comes inside a conical form for connection with the neck area in this location. The cross-sectional area reduces from the start to the end of this segment—an input pipe along one side and a cylindrical neck on the other end link this part. The convergence angle is usually 20.5 to 22.5 degrees. The addition is a larynx that is cylindrical. This is the venturi metre’s main segment. After switching to the convergence section, the fluid traverses via a cylindrical pipe in the venturi metre.
The neck does have a diameter that is usually 1/2 of the pipe. Across its span, the neck thickness remains constant. The final step is to spin the portion. Here the venturi metre has come to an end. It connects to the venturi metre’s neck, and on the other end, it connects to the pipe. The slight deflection angle is primarily used to prevent stream separation from the boundaries. The diverging part does have a 5 degrees to 15 degrees. So because the deflection cone is longer than the converging cone, the divergence angle is smaller than the converging angle.
Expression for venturi metre is
P1: Inlet pressure
P2: pressure at narrower region
ρ: Density of fluid
V1: Inlet velocity
V2: velocity at the narrower part
How does Venturi metre work, and how to use it?
The venturi metre operates on the premise of Bernoulli’s equation, which states that as velocity rises, the pressure falls. The neck’s cross-section is smaller than the cross-section of the input tube. The speed of the liquid’s flow increases as the cross-section from the input pipe lowers towards the throat, and therefore the pressure drops. Differential pressure is generated between the intake pipe and the neck of the venturi metre due to the pressure drop. The differential pressure can be monitored using a split manometer or dual instruments on the entrance and throat sections. After determining the rate of flow, the differential pressure via the pipeline is computed.
Advantages and Disadvantages of Venturi metre
Advantages
This gadget is simple to use.
Wherever a tiny head is accessible, it can be employed.
The energy loss is minimal.
It is a popular choice for high-volume applications (high discharge).
In large flow ranges, accuracy is higher.
The venturi metre has a more significant coefficient of discharge
High level of repeatability.
It could also be used for a compressed fluid that is incompatible.
Disadvantages
While servicing, there are several challenges.
This would be the 150,000 Reynolds number upper limit.
It is pricey and a little hefty.
A venturi metre has a high cost of installation.
The orifice metre takes significantly less room than this arrangement.
This gadget is not suitable for pipes with less than 76-millimetre diametres.
Applications of Venturi metre
The movement of chemicals through pipes.
Sometimes used in medicine to determine the amount of blood flow through the vessels.
The velocity of the flow of liquids released via pipes is calculated.
Often used in the manufacturing industry to calculate the pressure of an amount of gas or fluid inside a pipeline.
It is commonly utilised in sewage treatment when more extraordinary capacity tubes are required.
When high-pressure recovery is necessary, it is also employed. For example, in the carburettors of automobiles, especially in petrol engines.
Conclusion
Although several electronic devices measure fluid pressure dip inside a pipeline, venturi metres are still commonly employed in the industry. The venturi metre is based on Bernoulli’s equation, which asserts that pressure decreases as velocity increases. It is possible that the accuracy level will not be as great as desired. However, it is simple to use and may be used in various situations. The expense is also modest compared to any current electronic equipment that detects fluid ejection and pressure drop. Therefore, with its excellent precision and accuracy, it is frequently employed.
