| Popis: |
Transported Newtonian settling slurries (mixtures of solid particles and carrying liquid) tend to stratify in a slurry pipeline and the degree of their stratification significantly affects the frictional head loss in a pipeline system. Solid particles can span a broad range of sizes from those typical for fine sand to those typical for coarse gravel. Different fractions of solids have different properties and form different flow patterns. The different patterns are associated with different dominating particle support mechanisms and friction mechanisms in slurry flow. Hence, there are different models describing and predicting the frictional head loss in pipe flows of different settling slurries. In the presented work, we focus on friction-loss models for heterogeneous (partially-stratified) flow (V50-model), and for fully-stratified flow (Vsm-model). The models can serve as tools to scale up information on frictional head loss in flow of specific slurry obtained experimentally in a small laboratory pipe to larger pipes of industrial sizes. So far, the reliability of the scale up has been difficult to verify as an availability of coarse particle experimental data was restricted to small laboratory pipes (an internal diameter of a pipe typically not larger than 100 mm) and data from larger pipes were extremely scarce. In 2016 and 2019, extensive experimental campaigns were conducted in the GIW Hydraulic Laboratory (Grovetown, GA, U.S.A.) testing flows of Newtonian settling slurries in pipes of 3 very different sizes (103 mm, 203 mm, and 489 mm). We exploit the experimental data to evaluate the pipe-size scale-up ability of the heterogeneous V50-model and the stratified Vsm-model. The evaluation includes an analysis of the pipe-size effect on the characteristic velocities of the models: the suspension velocity V50 and the deposition-limit velocity Vsm. |
