A Correlation Study for the Positional Dependence of Friction Factor in Dilute Phase Flows

Abstract

Results of a comprehensive study on the flow friction factor data collected on suspensions of solid granular particles of semolina, fly ash, and alumina having a size range of 75.5 µm ≤ d_p ≤ 275 µm in air are presented. The experimental study was composed of 250 separate test cases in which airflow Reynolds number Re = UD/ν and loading ratio M_p/M_a were varied systematically covering the ranges of 50,000 ≤ Re ≤ 100,000 and 5% ≤ M_p/M_a ≤ 25%. An upward flow field with variable inclinations α of 10°, 20°, and 30° with the horizontal plane and a horizontal flow field, i.e, 0° inclination, were used to determine the influence of gravitational forces. Local static pressure gradients measured along the flow field with distance x were used to determine local air-particle friction factor f_{p + a}, which was observed to be under the influence of particle type, M_p/M_a, Re, and flow line inclination, α. The proposed correlation for the variation of f_{p + a} with x/D was evaluated to reach a generalized form exhibiting interactive influence of Re, M_p/M_a, α, and particle type.

Keywords:

• air-particle flow
• local static pressure gradient
• air-particle flow friction factor
• loading ratio
• flow line inclination