Numerical and experimental studies of particle deposition in a tube with a conical contraction-Laminar flow regime

Particle deposition in a tube with a conical contraction was studied numerically and experimentally. In the numerical study, an axisymmetric laminar flow field in a tube was obtained by solving the Navier-Stokes equations in cylindrical coordinates with the control volume method and the SIMPLER algorithm of Patankar (1982, Numerical Heat Transfer and Fluid Flow. Hemisphere, New York). Particle deposition efficiencies on the conical surfaces were calculated by tracing the particle trajectories in the flow field. The mechanisms considered for particle deposition included inertial impaction and interception. Through a parametric study, a general equation, giving a relative deposition efficiency as a function of the modified Stokes number, was obtained to characterize particle deposition in a conical contraction with an angle of smaller than 60°. For contraction angle larger than 75°, the results coincided with those of Ye and Pui (1990, J. Aerosol Sci. 21, 29). The numerical results were validated by experimental results. In the experimental study, the vibrating orifice aerosol generator was used to produce monodisperse oleic acid test aerosols tagged with uranine tracer. Deposition efficiencies were determined by recovering the deposited particles and measuring the uranine concentration using a fluorometer. The experimental deposition efficiencies give good agreement with the numerical results.