Flexural wave externally-attached mass flowmeter for two-phase fluids in small-diameter tubing, 1-mm ID to 16-mm ID

A way of measuring mass flow rate noninvasively in a metal conduit of small inner diameter (ID), so far 16 mm and 1 mm, was demonstrated with a few air/water mixtures. The method uses flexural waves, which at 100 kHz propagate at an average phase velocity that is a function of conduit parameters and the average density of the fluid inside the conduit. Using externally attached transducers, the flexural pulse transit time t_f in the conduit is measured in two zones whose centers are axially displaced by a distance L. The cross-correlation time τ between the jittery flexural propagation signatures observed in the first zone and later in the second zone was also measured. Fluid density ρ is obtained from t_f , flow velocity V from τ, and the mass flow rate M from the ρV product. If ρ changes slowly and only V changes rapidly, it may be preferable to abandon the tag method in favor of either contrapropagation or a reflection method that exploits the small reflections that occur at density inhomogeneities