Airflow deflectors of external windowsto induce ventilation: Towards COVID-19 prevention and control.

Since the Corona Virus Disease 2019 (COVID-19) outbreak, the normalization of the epidemic has posed great challenge to epidemic prevention and control in indoor environment. Ventilation systems are commonly used to prevent and control indoor transmission of disease. However, most naturally ventilated rooms are not efficient to prevent the spread of virus, i.e., classrooms. The goal of this work is to effectively adopt forced interference strategies (e.g., airflow deflector) applied to external windows to strengthen airflow diffusion performance (ADP) of natural ventilation. So far, no systematic study has been done to investigate the effectiveness of such airflow deflectors on its influence on natural ventilation and effectiveness of preventing the disease transmission in indoor environment. In this work, a case study was conducted based on cross-ventilated classrooms. Different settings of airflow deflectors (i.e., size and installation angle) were applied to the external windows. Air Diffusion Performance Index (ADPI) was utilized to evaluated airflow diffusion performance under different settings of the airflow deflectors. Then, the Wells-Riley model was applied to evaluate infection risk. According to the results, the infection risk can be reduced by 19.29% when infection source is located at the center of classroom and 17.47% when source is located near the side walls. This work would provide guidance for the design of classrooms ventilated with induced natural wind for epidemic prevention and control.