Numerical study of particle spatial distribution under column attachment ventilation

Column attachment ventilation mode (CAV) is a new form of air distribution based on pillars widely distributed in buildings and uses the column-based Coanda effect to efficiently transport the supply air from the top of the room to the lower occupied zone. Since CAV is essentially a down-supply ventilation mode, it may lead to the resuspension of particulate matter (PM). In this study, considering the pollutant particle size, air supply velocity (u0), and air supply temperature difference (ΔT) (including cooling and heating conditions), a numerical simulation method was used to study the PM movement and diffusion characteristics. The results indicated that the particles (<20 μm) could be suspended and carried by the airflow and have good airflow followability. The particles of 50–100 μm were mainly deposited in the airflow intersection zone. 21% of the particles can be blown up by the airflow and finally discharged through the air exhaust outlets. The concentration decay of PM 2.5 in the vertical direction decreased linearly with u0. The air supply temperature difference (ΔT) did not affect the indoor PM distribution in cooling conditions but significantly affected the heating conditions. In this study, the indoor PM concentration exceeded the Chinese standard threshold of 35 μg/m3, when the air supply temperature difference was 10 K. In the CAV mode, the airflow intersection zone between the two columns showed a larger PM mass concentration. The results of this study proved that the CAV mode can provide suitable IAQ under reasonable design parameters.