Modeling Large-Particle Deposition in Bends of Exhuast Ventilation Systems

A new model is presented to describe particle deposition in 90◦ bends of exhaust ventilation systems. This model accounts for nonStokes particle motion and for variable deposition patterns as a function of particle Stokes number. Estimates made with the new model and with two models previously published were compared to measurements of deposition in bends with geometries, particle characteristics, and airflow conditions similar to those found in industry—large duct diameters (15.4 and 20.3 cm), large particle sizes (19–140 μm), and turbulent airflow (Re = 203,000 and Re = 368,000). Whereas the two models published previously explain 30% or less of the variability in the data, the new model explains 85%. The mean residual with the new model, 0.6%, is nearer to zero than that of the two other models, 3.6% and 9.8%. The new model is applicable to mists and to solid particles that stick to bend walls.