Calculation of critical velocities to maintain solids in suspension in horizontal pipes

Abstract A simple theoretical justification of the empirical results for the flow velocities required just to suspend solid particles in horizontal pipes is deduced from turbulence theory. The new theoretical equation gives a better fit to the empirical data than does the Durand relation: it explains the maximum velocity often found at a solids concentration of 0.15 and it also predicts a velocity dependence on dp0.18, close to the mean empirical dependence on dp0.17. The sedimentation behaviour of the particles is examined in relation to the lifting velocities of various sizes of eddies, to explain the observed behaviour.