Predicting precipitate breakage during turbulent flow through different flow geometries

It has been observed that significant aggregate breakage occurs along a pipeline under turbulent flow conditions. Experimental results coupled with CFD simulations suggest that particle break-up occurs along the entire length of the pipe and not only in the sharp pipe diameter contraction region as has been previously suggested by other researchers.Two different pipe diameter contraction types were tested, a sharp contraction and a smoother one which has a progressive pipe diameter reduction at 45° to the pipe axis. Both pipe diameter transitions lead to different particle break-up at the same mass flow rate. More aggregate breakage was observed at the sharp contraction; this is due to the high degree of turbulence produced in that region. Precipitate breakage was also measured in different flow geometries including elbow, bend and straight pipes of diverse lengths. The results show that the breakage is a function of the complexity of the flow, its intensity and the residence time of the particle within the pipe. The experimental results were explained based on the variation of the turbulence eddy dissipation rate (ɛ) along the pipelines. A breakage model based on ɛ was proposed and validated by successfully predicting the final particle size for different exposure times and flow geometries.