Measurement of airflow is critical in many industries including furnace control, fume extraction, heating and ventilation.
This article seeks to explain some methods of doing this. More often than not, other parameters are measured and from this, actual flow rate is derived.
Volumetric flow (such as m3 per minute, standard cubic feet per hour (SCFH) or litres per second) is the most common requirement and this can be measured or derived from….
Mechanical ‘sail’ switches
Variable Area Flowmeters
If one knows the velocity of a gas, and one knows the cross-sectional diameter or rectangular dimensions of a pipe, it’s a relatively simple job to calculate flow volume. There are many on-line calculators to convert velocity to volume. In the example below we have selected a pipe diameter of 500 mm and entered a flow velocity of 20 metres per second.
Illustrated below are some examples of velocity instruments suitable for ducts etc.