CFD Study of Particle Deposition in Flows in Inclined Ducts

Deposition of particles on the walls of exhaust ducts of the commercial kitchen hoods has been a concern in buildings maintenance. The slope of duct in its way to the outdoor can affect deposition of grease particles. In the present work, deposition of particles in an inclined channel with cold walls under turbulent flow regime was studied. The cases that the flow is downward and upward, and when the flow is warmer than the walls were analyzed. The V2F turbulence model was used in the computational model so that the intensity of the turbulence velocity fluctuations normal to the wall can be properly evaluated. Accurate evaluation of the airflow and velocity fluctuations close to the walls was required for evaluation of particle deposition rate. The instantaneous velocity field was generated by adding the velocity fluctuations, obtained by using the Kraichnan model to the mean flow field. The Stokes drag, lift, Brownian, gravity and thermophoretic forces were included in the particle equation of motion. Effects of temperature gradients along with turbulence fluctuations on the deposition rate of different size particles were studied. The simulation results were compared with the empirical equation and discusses.