A numerical study of the aspiration efficiency of a thin-walled sampler in subisokinetic sampling

In this paper the efficiency of a subisokinetic thin-walled sampling tube facing the moving air is investigated with three-dimensional numerical model. Continuity and Navier-Stokes equations are solved to find the flow field around and inside of the sampler probe. Momentum equations are discretized using the control volume approach. Governing equations for particles’ motion are solved in a lagrangian reference frame. Having the particles’ paths, aspiration efficiency of the sampler is determined. Three particle sizes, characterized by aerodynamic diameter of 13, 34 and 89.5 µm, were considered. Then, in order to validate the numerical results, present work is compared with the previous experimental and numerical works. The previous numerical works for prediction of the sampling efficiency were not accurate at high values of velocity ratios. The results of this work show that the viscous effects play an important role on modeling of the sampler performance and the aspiration efficiency is affected by the gravitational effects.

Keywords:

Aerosol sampling , Aspiration efficiency , Numerical model