Refining the method for determining the flow rate of air entrained by freely falling polydisperse loose material

Abstract

Air entrainment by a flow of loose material is the primary cause of dust releases during handling of such materials. Computing the flow rate of air ejected by the material is a prerequisite for ventilation system design. An additional consideration is that mining industries normally handle polydisperse materials. The goal of our study is to design a method for computing the flow rate of air entrained by dry loose material while accounting for its particle-size distribution. We rely on a phenomenological method as we describe an interpenetrating continuum, “falling particles – air”. We propose a probabilistic approach for determining the aerodynamic drag coefficient for freely falling particles of polydisperse material. A differential equation is obtasined for air entrained by this material. The effect of particle-size distribution of the material being handled is considered together with methods for determining the average particle diameter on the flow rate of ejected air.