Computational modeling of effects of thermal plume adjacent to the body on the indoor airflow and particle transport

The buoyancy driven thermal plume near a sitting, heated manikin that corresponds to the condition for a sitting human was studied. The surface mesh of an experimental manikin was integrated into a computational model for a ventilated room with a displacement air distribution system. Particular attention was given to the effect of the thermal plume on particle concentrations in the breathing zone and entrainment of particles emitted from different sources near the floor. An Eulerian approach was used for simulating the airflow field in the cubicle and the pollutant particle trajectories were evaluated with a Lagrangian method. The equation of particle motion that was used included the inertial, viscous drag, Saffman lift and gravity forces. The plane and volume averaged particle number concentrations in the breathing zone and vicinity of the thermal manikin were evaluated and the results were compared with the experimental data. The probability that entrained particles from the inlet air register and floor could be transported to the breathing zone of the manikin by the thermal plume around the body was also investigated. The simulation results showed that the thermal plume flow generated by the temperature gradient adjacent to the body can lead to a high concentration of suspended particles in the breathing zone. Furthermore, the plume plays an important role in transporting particles entrained from the floor to the breathing zone in rooms with displacement ventilation system.