Particle Deposition in Cyclic Converging Tube Flow

Abstract

Deposition efficiency (DE) of aerosol particles in a converging tube was determined experimentally under cyclic flow conditions with frequencies of 16, 30, and 50 cycles/min. Two flow models with different converging angles from two daughter branches (θ = 30° and 45°) were used. Monodispersed oleic acid droplets (5 and 7 μm in diameter) tagged with uranine were used as test aerosols and sampled through the model tube at a mean Reynolds number (Re) of 906–4586. Mean Stokes number (Stk) was between 0.038 and 0.37. It was found that particle deposition occurs mainly in the parent tube near the flow junction. DE increased monotonically with increasing Stk and branching angle. DE could be unified as a single function of a parameter, √Stk sin θ. There was no change in DE with cyclic frequency between 16 and 50 cycles/min. However, DE was higher by ∼25% with cyclic flows when compared with those with constant flow at the same level of mean flow rate.