CFD simulation of an air cleaner

Air cleaners have become more common after the emergence of COVID-19. Most studies have shown clear benefits in using air cleaners while some have reported no observed benefits, often due to incorrect sizing. For air cleaners to work efficiently, clean air delivery rate (CADR) -based sizing is important. For example, REHVA criterium for air cleaners​ states that air cleaner CADR should be 2 times greater than the outdoor air flow by the ventilation system in rooms with a ventilation rate more than 1 air change per hour (ACH).

The CADR of an air cleaner can be determined experimentally according to standardized methods and sizing can then be carried out based on the characteristics related to the space of interest, following guidelines. Additionally, mass balance models can be used to predict aerosol concentrations in the space accounting for various sources and the effect of both ventilation and air cleaners. However, these simulations typically exploit well-mixed assumption and do not thus account for ventilation or air purification efficiencies which are site specific and depend on ventilation design and positioning of the air cleaner, respectively. Therefore, to tackle this challenge, the current paper introduces computational fluid dynamics (CFD) approach to co-optimise ventilation and air cleaner performance.