Measurement of mass flow rate using a vortex flowmeter

Conventional mass flow rate is derived from volumetric flow rate multiplied by fluid density. However the measurement accuracy is not satisfying because of density variation. Mass flowmeters that can directly measure mass flow rate have been studied and developed recently. But these flowmeters still have limits in practical application. Mass flow rate directly measured by a vortex flowmeter has been proposed to overcome these disadvantages. But the piezoelectric sensor widely used in vortex flowmeter is subjected to noise disturbances caused by pipe vibrations and fluid turbulence. Many efforts on the sensor structure and signal processing have been made to improve the anti-noise ability. However the results are not so satisfactory. A new method using differential pressure between upstream and downstream sides of the vortex shedder to detect the vortex shedding is presented, from which vortex frequency and pressure drop are measured simultaneously. With this method mass flow rate is obtained directly and noise disturbance is reduced.