Computational Fluid Dynamics Simulations of Aerosol Behavior in a High Speed (Heubach) Rotating Drum Dustiness Tester.

Potential exposure from hazardous dusts may be assessed by evaluating the dustiness of the powders being handled. Dustiness is the tendency of a powder to aerosolize with a given input of energy. We have previously used computational fluid dynamics (CFD) to numerically investigate the flow inside the European Standard (EN15051) Rotating Drum dustiness tester during its operation. The present work extends those CFD studies to the widely used Heubach Rotating Drum. Air flow characteristics are investigated within the Abe-Kondoh-Nagano k-epsilon turbulence model; the aerosol is incorporated via a Euler-Lagrangian multiphase approach. The air flow inside these drums consists of a well-defined axial jet penetrating relatively quiescent air. The spreading of the Heubach jet results in a fraction of the jet recirculating as back-flow along the drum walls; at high rotation rates, the axial jet becomes unstable. This flow behavior qualitatively differs from the stable EN15051 flow pattern. The aerodynamic instability promotes efficient mixing within the Heubach drum, resulting in higher particle capture efficiencies for particle sizes < 80 μm.