A vertical laminar airflow system to prevent aerosol transmission of SARS-CoV-2 in building space: Computational fluid dynamics (CFD) and experimental approach

Respiratory aerosol particles carrying the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) are a primary cause of the long-distance infection, and insufficient ventilation systems make building occupants highly prone to the coronavirus disease-2019 (COVID-19). As a preventive measure of the aerosolized viable SARS-CoV-2 suspension in building space, we seek to propose an optimal design of the upper-room/drop-ceiling aeration grid system generating vertical laminar airflow (VLAF) as an aerosol barrier. On a test plan (6.1 x 4.7 m) representing the standard hospital patient room in South Korea (a 2.7 m-height room of 77.4 m(3) in volume), we investigated the air-terminal size, spacing and air speed that shape uniform downflow of fresh air, minimizing horizontal spread. Our simulation results using the Taguchi method and computational fluid dynamics (CFD) in presence of indoor human expiration indicated that a steady vertical air supply of 0.3 m/s through 0.04m-diameter air diffusers deployed by 0.5 m spacing is the most effective to form VLAF. Physical particle detection tests at the height of 1.5 m in mockup setting of the optimal system design, revealed that expiratory aerosols produced by a single person were almost entirely removable in 20 s. Investigations also confirmed that the proposed design could minimize stagnant airflow regions and would potentially satisfy the indoor air-speed condition for occupant thermal comfort.