Venturi Meter: Definition, Construction, Working, Experiment, Derivation, Formula, Advantages, Application [Notes & PDF]

what is a venturi meter ?

A venturi meter is a device used to measure the flow rate of a fluid in a pipe. It consists of a converging section, a throat, and a diverging section. The converging section gradually reduces the cross-sectional area of the pipe, causing the fluid to accelerate and its pressure to decrease. At the throat, the cross-sectional area is the smallest, creating the maximum fluid velocity and lowest pressure. Finally, in the diverging section, the cross-sectional area gradually increases, causing the fluid to decelerate and its pressure to rise again.

The pressure difference between the upstream and throat sections of the venturi meter is directly related to the flow rate of the fluid. By measuring this pressure difference, the flow rate can be determined using appropriate equations or calibration curves.

Venturi meters are commonly used in various industries, such as water supply, oil and gas, and chemical processing, to measure the flow rate of liquids and gases. They offer advantages such as low pressure drop, accuracy, and reliability. However, they require careful installation and calibration to ensure accurate measurements.

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history

The history of the venturi meter dates back to the 18th century when Italian physicist Giovanni Battista Venturi made significant contributions to fluid dynamics and flow measurement. In the 1700s, Venturi conducted experiments and observations on fluid flow, particularly in relation to the principles of Bernoulli’s equation.

However, the modern venturi meter, as we know it today, was developed in the early 19th century. French engineer and physicist Henri Pitot, known for his work on fluid mechanics, made further advancements in flow measurement. He designed and introduced the Pitot tube, which utilizes the principle of pressure difference to measure fluid velocity.

Building upon Pitot’s work, French engineer Clemens Herschel further refined the concept and developed the Herschel venturi tube in the mid-19th century. Herschel’s venturi tube consisted of a tapered section that allowed for accurate flow measurement by utilizing the pressure difference between the converging and throat sections.

Over time, the venturi meter design continued to evolve, with improvements in accuracy, construction materials, and installation techniques. The venturi meter gained widespread recognition and acceptance in the field of flow measurement due to its reliability and accuracy compared to other types of flow meters.

Today, It is commonly used in various industries and applications, ranging from water supply systems, oil and gas pipelines, chemical processing plants, to HVAC systems. They have become an integral part of flow measurement technology, providing efficient and accurate measurement of fluid flow rates.

venturi meter diagram

venturi meter principle working

The venturi meter works based on the principles of fluid dynamics, specifically Bernoulli’s principle and the conservation of mass. Bernoulli’s principle states that as the speed of a fluid increases, its pressure decreases, and vice versa, when the fluid flows through a constriction.

In a venturi meter, the fluid flows through a converging section, a throat, and a diverging section. The converging section gradually narrows, causing the fluid to accelerate and its velocity to increase. According to Bernoulli’s principle, as the velocity increases, the pressure decreases. Thus, the pressure at the narrowest point, the throat, is lower than the pressure at the upstream section.

At the throat, where the cross-sectional area is the smallest, the fluid reaches its maximum velocity. This high velocity is associated with a further decrease in pressure. The pressure at the throat is the lowest point within the venturi meter.

As the fluid enters the diverging section, the cross-sectional area gradually expands, causing the fluid to decelerate. As a result, the pressure begins to rise again.

The pressure difference between the upstream section and the throat is measured using pressure taps located at these points. This pressure difference is directly related to the flow rate of the fluid passing through the meter.

By measuring the pressure difference, the flow rate through the venturi meter can be calculated using appropriate equations or calibration curves. These equations take into account the dimensions of the venturi meter, the fluid properties, and the pressure readings to determine the flow rate accurately.

Therefore, the venturi meter operates on the principle of utilising the pressure difference created by the change in cross-sectional area to measure the flow rate of a fluid.

venturi meter working step by step

The principle of operation of a venturi meter is based on the Bernoulli’s principle and the conservation of mass. It involves the measurement of the pressure difference created by the change in the cross-sectional area along the flow path. Here’s how a venturi meter works:

It is important to note that the accuracy of the flow measurement using a venturi meter relies on proper installation, calibration, and accurate measurement of the pressure difference. Additionally, the flow conditions and fluid properties should be within the operating range specified for the particular venturi meter being used.

venturi meter formula

The flow rate through a venturi meter can be calculated using the Bernoulli’s equation and the conservation of mass. The most commonly used formula for calculating the flow rate through a venturi meter is the following:

Q = C * A * sqrt(2 * ΔP / ρ)

where:
Q is the volumetric flow rate (in m³/s or ft³/s),
C is the discharge coefficient (dimensionless), which accounts for the efficiency of the venturi meter,
A is the cross-sectional area of the throat (in m² or ft²),
ΔP is the pressure difference between the upstream and throat sections (in Pa or psi),
ρ is the density of the fluid (in kg/m³ or lb/ft³).

The discharge coefficient, C, is specific to each venturi meter design and is typically provided by the manufacturer or determined through calibration. It takes into account the shape, size, and other characteristics of the venturi meter.

It’s important to note that the above formula assumes incompressible, steady-state flow conditions and neglects frictional losses and other minor effects. Additionally, the units of measurement must be consistent in the formula for accurate results.

To ensure accurate flow rate calculations, it is recommended to refer to the specific venturi meter’s documentation or consult the manufacturer’s guidelines, as they may provide additional correction factors or considerations specific to their product.

venturi meter used to measure

Venturi meters are used to measure the flow rate of fluids, both liquids and gases, in various industries and applications.

venturi meter specifications

The venturi meter specifications you provided are as follows:

These specifications provide information about the size range, accuracy, flow coefficient, and beta ratios of the venturi meter. It’s important to note that these specifications may vary depending on the manufacturer and specific model of the venturi meter. Therefore, it is recommended to consult the manufacturer’s documentation or specifications for the particular venturi meter you are considering to ensure accuracy and compatibility with your application.

applications of venturi meter

Venturi meters have several applications across different industries. Some of the common applications of venturi meters include:

Overall, the versatility, accuracy, and reliability of venturi meters make them widely used in numerous industries and applications where flow measurement is critical for efficient and safe operations.

advantages of venturi meter

Venturi meters offer several advantages that make them popular in flow measurement applications. Some of the key advantages of venturi meters are:

It is important to note that while venturi meters offer many advantages, their accuracy and performance can be affected by factors such as proper installation, calibration, and maintaining a clean and debris-free flow path. Regular inspection and maintenance are necessary to ensure optimal performance and accurate measurements.

disadvantages of venturi meter

While venturi meters offer several advantages, they also have a few limitations and disadvantages. Some of the key disadvantages of venturi meters include:

Despite these disadvantages, venturi meters remain widely used in many industries due to their overall accuracy, reliability, and versatility in flow measurement applications. It is important to carefully assess the specific requirements and limitations of a given application before selecting a flow meter, including considering alternative options if necessary.

Reference : https://whatispiping.com/venturi-meter/

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