Numerical study of the effects of human body heat on particle transport and inhalation in indoor environment

The inhalation of micron particles by a manikin standing in a ventilated indoor environment was numerically investigated using Computational Fluid Dynamics (CFD). Computations were conducted with various combinations of the free stream velocity (0.05-0.25 m/s representing typical indoor wind speeds.), occupant orientation relative to the free stream (back-to-the-wind or facing-the-wind) and heat transfer (isothermal or thermal flow). It was found that the body heat has a significant impact on the airflow field in the vicinity of the manikin by causing an upwards airflow on the downstream side of the manikin. It was also found that the effect of body heat on particle inhalation depends on the manikin orientation relative to the free stream. When the manikin is facing-the-wind, body heat has a little effect on particle inhalation and can be neglected. However for a back-to-the-wind orientation, the situation is much more complicated as the source height of inhaled particles depends on the speed of free stream. When the wind speed is low (0.05 m/s), the critical area is located near the floor level. The central height of the critical area then increases with increasing free stream speed until it reaches the nose height when the wind speed rises up to 0.25 m/s. This indicates that the body heat is an important consideration when investigating contaminant inhalation by human occupants in low-speed (typically less than 0.2 m/s) indoor environment