A new design approach for the established flow region of vertical, dilute-phase pneumatic conveyors

Abstract

An analysis has been completed for a comprehensive set of vertical, dilute-phase pneumatic conveying pressure drop data from an investigation by Flatow. The data were collected in the established flow region for eight different materials conveyed in 0.05-, 0.10-, 0.20-m internal diameter, 20-m tall steel risers. Particle velocities derived from the pressure drop data were used to develop an equation of motion that includes terms for pipe diameter, terminal velocity, coefficient of restitution, and particle shape. The best data fit was achieved using the actual gas density and the actual gas velocity adjusted for voidage. Adjusting the terminal velocity for voidage, an approach recommended by many investigators, did not improve the fit for reasons identified by the present research.Using the equation of motion, particle velocities were predicted and used to calculate total pressure drops that are within ±15% of the measured values. The calculated values also produce the characteristic trough-shaped total pressure drop curves allowing the minimum pressure drop gas velocity to be determined without recourse to a separate correlation. A comparison with other studies using shorter risers indicates that data from these studies likely include acceleration effects. A separate study will investigate this observation further.