Influence of Particle Hardness on the Discharge through Orifices

Eleven types of polyethylene particles are used to examine the influence of particle properties on the gravity flow through an orifice located on a flat bottom of a vessel. The density of particles is varied from 825 to 945kg/m3 and four of them are mixed with a slipping agent to improve the surface properties. Orifice size is changed from 20 to 27mm with an increment of one mm. As a result, when Duro-hardness becomes small, the mass flow rate of particles decrease whereas the wall friction coefficient against an acrylic plate and the angle of repose increase. Although the contraction coefficient increases with a decrease in Duro-hardness, the flow coefficient of the Beverloos' correlation equation is lowered. The particles with slipping agent show a decrease in the wall friction coefficient.