A NUMERICAL STUDY OF DISPERSION AND LOCAL EXHAUST CAPTURE OF AEROSOLSGENERATED FROM A VARIETY OF SOURCES AND AIR-FLOW CONDITIONS

Focus is put on aerosol source parameters and their influence on aeros ol dispersion and capture by a local exhaust. The studied parameters w ere particle diameter, density, and initial velocity. included in the study was the influence of obstacles and airflow patterns. Direct capt ure efficiency of an exhaust above the contaminant source was used to compare the influence of the studied parameters. The study was based o n a numerical model that computes the particle trajectories, taking in ertia, drag forces, gravity, and turbulence into account. The relevanc e of particle relaxation time, aerodynamic diameter, and slopping dist ance is discussed. It is concluded that local exhaust capture of passi vely emitted particles can be described by particle relaxation time an d the vertical air velocity al the emission point. The influence on di rect capture efficiency from particle initial velocity is limited comp ared to imposed airflow patterns as jets and cross drafts. A table und erneath the contaminant source may improve capture efficiency. The num erical model proved to be a useful tool to handle the complexity of co ntaminant sources in the industrial environment.