A method to measure mass and volume flow rates of two-phase flows

Abstract

The present paper describes a method to measure simultaneously the individual mass and volume flow rates of a particulate two-phase fluid flowing through ducts. A mass flow meter, based on Coriolis force measurements, and an inductive volume flow rate meter were employed in sequence and measured the total (volume and mass) flow rates v ̇ tot and m ̇ tot of a fluid-solid two-phase flow. The individual volume and mass flow rates were computed from them and from the known densities of the components. Arguments are presented for and experimental information is given to support the fact that the Coriolis flow meter is able to measure the total mass flow rate of a particulate two-phase flow, if one takes care that the particles in the flow follow the oscillations of the measuring instrument (and the fluid). The inductive volume flow rate instrument is argued to give in a particulate flow, under conditions of homogeneity and suitable limitations on the mean relative velocity between the phases, a good measurement of the total volume flow rate. This is confirmed experimentally in a water flow loaded with sand. It is shown that the possible (relative) error of the volume flow rate in such a flow is bounded by the relative velocity; in the natural flow limits of the water-sand system this error turns out to be one order of magnitude smaller than the relative velocity. The relative velocity can be estimated and the level of accuracy required for the measurements then determines the lower limit of the range of flow rates accessible within it. Accuracy considerations are presented in the appendix.