Dispersed powder flow through vertical pipes

In this study a novel transducer, based on an electrical capacitance principle, was used to measure the instantaneous volume-averaged in situ particle fraction and thereby determine the volume-averaged particle velocities. It was clear that the 450 μm diameter sand particles were being accelerated to a terminal slip velocity with respect to the gas phase. The static pressure drop over the same length was also measured and interpreted by means of a one-dimensional, two-phase model. The contributions to the overall pressure drop of gravitational forces on the particle, acceleration of gas and particles and the coupling force between gas and particles were calculated. The gas—particle drag coefficients were within 30% of those of single particles. A predictive model was also developed which yielded good results with the experimental data.