Novel personalized chair-ventilation design integrated with displacement ventilation for cross-contamination mitigation in classrooms

Abstract

This work investigates the performance of a novel chair-ventilation design integrating ductless personalized ventilation (PV) and personalized exhaust (PE) in a classroom conditioned by displacement ventilation (DV). The aim is to protect seated students and restrict contaminants' transport in high-density classroom where students are seated at a typical separating distance of 0.4 m. A 3-D computational fluid dynamics model was developed and experimentally validated in a climatic chamber including a prototype of the proposed ventilation system. The cross-contamination was assessed using the inhaled intake fraction (iF) index, which is the ratio of the contaminants’ mass inhaled by an exposed person to that exhaled by an infected person. The proposed system effectiveness was assessed via an exposure reduction index (ER) when compared to “no chair ventilation” case at the same separating distance of 0.4 m, as well as a “large distancing” case at separating distance of 2 m in a room that is only ventilated via DV. It was found that the proposed chair system protected exposed occupants against cross-contamination. The chair system, compared to the no chair ventilation case, was able to reduce the exposure level of students due to the combined protective roles of the dilution of breathing zone (BZ) by the PV flow and the shielding effect of the PE flow. By comparing the proposed system to the large separating distance case, it was still able to provide similar and even higher protection levels for all students when both PV/PE systems operated at flowrates higher than 6 l/s. © 2022 Elsevier Ltd