Interaction of convective flow generated by human body with room ventilation flow: impact on transport of pollution to the breathing zone

This study aims to investigate the interaction between the human convective boundary layer (CBL) and uniform airflow from two directions and with different velocities. The study has two objectives: first, to characterize the velocity field in the breathing zone of a thermal manikin under its interaction with opposing flow from above and assisting flow from below; and secondly, implication of such a flow interaction on the particle transport from the feet to the breathing zone is examined. The results reveal that the human body heat transports the pollution to the breathing zone and increases concentration by factor of 5.5. Downward flow of 0.175 m/s does not change airflow patterns and pollutant concentration in the breathing zone, while the velocity of 0.425 m/s offsets the thermal plume and minimizes the concentration. Since the downward flow at 0.30 m/s collides with the CBL at the forehead level, it prolongs particle dwell time and consequently, increases the concentration in the breathing zone by 106%. Adding the assisting flow dilutes the pollution and reduces the concentration compared to case of a pure CBL. Findings that the assisting flow of 0.30 m/s and above reduces the velocity in the breathing zone due to the blocking effect of the chair suggest that furniture should be carefully considered in numerical results predictions and optimal air distribution