Estimation of the critical velocity in pipeline flow of slurries

Abstract

A detailed examination of the critical velocity in pipeline flow of non-colloidal slurries was carried out. Published critical velocity correlations were collected and were recast into a standard form so that they could be compared with each other, and they were also tested against a broad collection of experimental critical velocity data. Altogether, a total collection of 864 experimental critical velocity data, representing a broad variety of solid materials and pertaining to wide ranges of the variables involved, were used in these tests. This rather substantial body of experimental data was also used as the basis for developing a set of improved critical velocity correlations, which were established by fitting the data to various forms of the standard equation. Among the principal results of this work are the following: The dependence of the critical velocity on pipe diameter is very nearly equal to D 1 2 , while its dependence on particle size, for slurries of non-colloidal particles, is very nearly equal to d 0. The analytical result due to Oroskar and Turian indicates that υ c depends on pipe diameter as D 0.6, and on particle size as d 0, while the best empirical fits to the data suggest that the dependence on pipe diameter is approximately D 0.5, and that on particle size is at most d 0.06. In addition, both the newly established empirical correlations and the analytical correlation due to Oroskar and Turian predict a maximum in the υ c vs. C curve, the maximum occurring at solids volume concentration of 0.25 to 0.30. The comparisons with experimental data further established that the analytical result by Oroskar and Turian, and the empirical correlations developed in this work, do a superior overall job of predicting the data than other published correlations.