Anniina Kittilä, ETH Zürich, Institute of Geophysics, Geothermische Energie u. Geofluide. Sonneggstrasse 5, 8092 Zürich, Switzerland e-mail: anniina.kittila(at)erdw.ethz.ch
Description of the method
Venturi meters are connected to pipes, usually in industrial facilities, in order to measure the rate of flow in the pipes. Venturi meters are pressure devices that consist of a convergent cone section, cylindrical bore, and a divergent cone section. Inflowing water is accelerated through the converging cone, which causes an increase in its velocity and a decrease in its pressure according to Bernoulli’s equation. The pressure change can be measured between the upstream side of the cone and the cylindrical throat section, which relates to the flow rate. As the fluid exits the throat section, its pressure recovers almost completely in the divergent section (Emerson 2015, Lenntech 2015).
Appropriate applications and performance
The material of the venturi meters (tubes) can be chosen based on the required application, so they are corrosion resistant and require very few to virtually no maintenance. This also means that the devices have very long service life. The accuracy of the venturi meters is high, and the pressure losses are low. The total cost is also low, except for the initial purchase of the device (ABB 2015, Emerson 2015, Solartron ISA 2015). Venturi meters are suitable for industrial scale piping networks, where long product life and continuous measurements are desirable, but for open channel or temporary flow rate measurements other methods are recommended to be used.
Design and usage of venturi meters is supported by ISO 5167-4 standard, and the variety of different size meters is good, ranging from 50 mm to 1200 mm (ABB 2015, Emerson 2015) or from 25 mm to 1800 mm and greater (Solartron ISA 2015). Because the method is based on simple Bernoulli’s equation and the technology is proven through standard, it is well developed and proven in use.
ABB 2015. Classical Venturi Tube VTC. Site visited 18.4.2015. http://new.abb.com/products/measurement-products/flow/differential-pressure-flowmeters/vtc-calssical-venturi-tube
Emerson 2015. Daniel Venturi Tubes. Site visited 18.4.2015. http://www2.emersonprocess.com/en-US/brands/daniel/Flow/differential-pressure-flowmeter/Pages/Venturi-tube.aspx
ISO 5167-4:2003. Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full – Part 4: Venturi tubes. International Organization for Standardization.
Lenntech 2015. Venturi. Site visited 18.4.2015. http://www.lenntech.com/venturi.htm
Solartron ISA 2015. Flowstream Venturi Tubes. Site visited 18.4.2015. http://www.solartronisa.com/Products/venturitubes.aspx