A Vortex flow meter measures flows of liquids, gases and steam by sending the frequency at which vortices are alternately shed from a bluff body. The frequency at which the vortices are alternately shed is directly proportional to the flow velocity.
What is a Vortex Flow Meter?
The vortices are present either side of the bluff body and are carried away by the flowing fluid. Zones of high or low pressure now appear downstream and thus create a phenomenon that is known as the Karman vortex street. These differences in pressure exactly match the frequency of the passing vortices and are precisely registered by the mechanical sensor shown in the video in slow motion.
This sensor is unique because it is so well balanced that high amounts of pipe borne vibrations, pressure surges and temperature shocks have no effect whatsoever on the measurement. The distance between two consecutive vortices corresponds to a defined volume of fluid. Therefore, total flow can be calculated by counting the vortices that pass. The higher the flow velocity, the higher the measured frequency of vortices. In some applications, the velocity is too low for perceptible vortices to form.
However, the velocity can be increased simply installing a vortex meter that has a reduced cross section and this modification does not affect the measuring accuracy. Functionality can be enhanced by incorporating optional temperature measurement into the sensor. A configuration as such, together with a built-in flow computer can calculate temperature dependant mass or energy flow important in certain industrial processes involving saturated steam or gases.