Abstract
The difficulties in predicting the frictional energy gradient for pipeline flow of settling slurries are well known. Whenever possible, it is desirable to carry out tests on a representative sample of the material to be conveyed, and scale the results to other pipe sizes. This paper presents a mechanistic approach to scaling tests results, based on the physical processes of solid trnapsort identified in the work of Newitt, Shook and Wilson. A basic distinction is drawn between solids conveyed in pseudo-homogeneous suspension, and solids stratified at higher concentration in the lower part of the pipe. The suspended and non-suspended solids are assumed to contribute independently to the friction gradient, in a fashion characterised by material constants which depend on the slurry under consideration. The proportion of solids conveyed as stratified load is taken to vary with mixture velocity in the general manner proposed by Wilson. The tests were designed to determine the material constants which describe the variation of pressure drop with mixture velocity in heterogeneous flow. The approach is illustrated by results obtained for three settling slurries of foundry sand, masonry sand and crusted granite, in horizontal pipes of diameter 0.20 m and 0.44 m (8 inch and 18 inch nominal). In each case, the validity of the scaling method is demonstrated. (A)