Pressure Losses in Pneumatic Transport. A Model Based on Particle-Wall Interactions and Particle Density Distribution

摘要

An experimentally verified model which calculates pressure losses originating from dilute phase pneumatic transport of coarse particles in the horizontal stationary flow regime is presented. The model is based on the balance of drag and frictional forces on particles. The particles are characterized by their terminal velocity, the particle-wall sliding friction coefficient and the coefficient of restitution between particles and wall. The influence of the inhomogeneous particle distribution in the pipe is taken into account, by a particle density distribution, which resembles the barometric height formula. A Froude number, based on the mean square value of the radial particle-velocity component, is used as an empirical parameter. This number increases with increasing average air velocity, but perhaps depends on pipe diameter and solids-mass flow. The assumption of a linear relationship between the Froude number and the average air velocity provides scaling and predicting possibilities for pressure losses.