Flow Measurement · Glossary

What is a Venturi Tube?

DP flow elementFlow Measurement

A venturi tube is a DP flow element with a smooth converging inlet, a throat and a diverging outlet that recovers most of the pressure.

Venturi Tube Explained

Fluid accelerates through the converging cone into the throat, where pressure is lowest. The long diverging cone slows it down again and recovers most of the pressure.

Venturis have low pressure loss, good resistance to wear and a stable coefficient, but they are long and expensive. They are common on large water lines and air ducts.

Venturi Tube: Typical Values

Convergent angle (ISO 5167-4)	21° ± 1°
Divergent angle	7° to 15°
Pressure loss	about 5 to 20 % of DP

Calculators for Venturi Tube

CalculatorVenturi Flow CalculatorFree online calculator with formula and worked example.CalculatorOrifice Pressure Loss CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is a Venturi Tube?

A venturi tube is a DP flow element with a smooth converging inlet, a throat and a diverging outlet that recovers most of the pressure.

Why choose a venturi over an orifice?

For low pressure loss on large lines, for dirty fluids that would wear an orifice edge, or where the energy cost of loss matters.

Is a venturi more accurate?

Its coefficient is close to 1 and stable, but uncertainty is similar to a well installed orifice unless it is flow calibrated.

Learn more on the blog

Mistakes in DP flow measurement

A practical guide on instrumentationblog.in with more detail on venturi tube and how it is applied on real plants.

Read Full Article

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