Prediction and optimization of erosion zone in pipe bends due to slurry flow

Solid-liquid mixtures are prone to erosive wear when transported using pipes with bends, causing problems in operation and leading to high maintenance costs. This work has developed a CFD coupled with RSM model to predict and optimize erosion zone of a horizontal 90° pipe bend (R/D=2.8, D=53 mm) for sand-water slurry flow. The two-phase flow field is simulated by Eulerian-Eulerian multiphase and the standard k-ε mixture turbulence model. The friction energy flux method characterises erosion zones, the fidelity of which was validated against experimental data accurately as RMSE=0.028. For the sand particles with the mean diameter of 450μm, a rotatable Central Composite Design with two independent variables; V=2.0-3.56 m/s and Cv=8.82-16.28 vol.%, was generated from 13 CFD simulation runs. The following three responses were modelled: normalised wear rate (NWR), friction energy flux (FEF), wall solids concentration. The factors that strongly affected NWR (β₁=0.607) and FEF (β₁=295.7) were flow velocity. The optimization showed the minimum erosion occurred at V=1.68 and Cv=11.76, resulting in an 69% reduction of NWR from the maximum operating velocity. Under all conditions the maximum erosion was at the outer wall near the bend exit (θ=75-90°). The results give useful suggestions for the hydraulic design of slurry pipelines.