Rethinking different ventilation strategies in a post-pandemic era: a CFD assessment

The world has experienced the devastating nature of airborne transmitted diseases through the COVID-19 pandemic. Significant actions were taken in order to reduce the number of new infections, such as quarantines, social distancing, mask wearing, frequent hand washing and surface disinfection. However, all these measures have proven insufficient to eradicate short and long-range infections, confirming the need for engineering tools to control the indoor air quality. Although the role of ventilation design in the minimization of indoor pollutants has been widely discussed, its performance has been linked to energy efficiency. General-volume ventilation strategies have been predominant. However, in a dynamic indoor environment, airflow patterns increase or decrease the risk of airborne transmission at local points, making this consideration an unsuitable option to provide clean air in the breathing zone. The present research demonstrates the purging efficiency of breathing-zone-volume ventilation against the traditional general-volume choice by comparing mixing, stratum and impinging jet ventilation. CFD has been used to predict indoor airflow, simple thermal sensation through draught discomfort and purging efficiency through age of air in a general-purpose building applying RANS modelling. Results show that breathing-zone-volume strategies significantly improve the age of air under cooling mode and sustain or slightly improve it under heating mode. However, draught sensation slightly increases in all the cases. In conclusion, a balance must be reached in this post-pandemic era to satisfy the design triad: purging efficiency, thermal comfort and energy efficiency without sacrificing one of these three elements.