Visualization of Asymmetric Solids Distribution in Horizontal Swirling Flows Using Electrical Resistance Tomography

Abstract

Efficient slurry transportation is vital to many industries. It has been proposed that helically formed pipes, which can be used to keep particulate solids in suspension, should be applied to enhance the distribution of solids in piped slurries. The use of a new in-situ measurement method based on electrical impedance tomography is proposed to assist in understanding the effect of particle suspension and as well as the effect on the wear of pipes by solid particle impingement due to the application of such a swirl-inducing pipe. In the absence of accurate predictive models for such complex flows, it is demonstrated that this method enables direct visualization of the solids concentration profiles in the pipes. Through the application of an advanced impedance image reconstruction algorithm and other analysis software, the asymmetric solids concentration distribution in horizontal swirling flows can be quantified. Particle concentration regimes are reported as a function of the water axial flow velocity and the downstream distance from the swirl-inducing pipe section. The nature of the solids distribution at a typical cross-section is reproducible and takes the form of a crescent region of a higher solids concentration, re-orientated in the direction of swirl by approximately π/2 from the normal settling position. Low concentration areas in a crescent shape appear on the opposite semi-circumference to the particle burden. These appear to develop into a ring structure as the water flow increases to a high axial velocity. At a high flow velocity, the mode of particle dispersion along the length of the pipeline appears to take the form of a group of ellipses. Larger ellipses were observed near the swirl-inducing pipe.