Computational investigation on the flow of high concentration fly ash slurries through converging-diverging bends

High concentration slurry disposal pipelines are now being increasingly preferred for the transportation of coal ash slurries in the thermal power plants. Thus, the focus of the present paper is to establish the effect of area ratio on the pressure drop across wear-resistive converging-diverging pipe bends at high concentrations (C_w≥ 60% by weight) so as to optimize the bend geometry for such flows. The distribution of solids is assumed to be homogeneous with a strong non-Newtonian character having Bingham fluid type of behavior. Numerical simulation at high concentration (60–68% by weight) through pipe bend has been carried out using the commercially available CFD software FLUENT. Based on our earlier studies, K-ω (SST) model for turbulent flow and Bingham Plastic model for laminar flow are adopted. Pressure drops for five different converging-diverging 90° bends with different area ratios in the range 1–3 have been computed for different concentrations in the range of 60–68% by weight. On the basis of the study, the optimum value of the radius ratio is found to be 1 for laminar flows and 1.5 for turbulent flows.