CFD Modeling of Room Air Flow Effects on Inactivation of Aerosol SARS-CoV-2 by an Upper Room Ultraviolet Germicidal Irradiation (UVGI) System

Ultraviolet germicidal irradiation (UVGI) inactivates viral aerosols in indoor environments. Upper room UVGI systems use wall or ceiling mounted fixtures to create a disinfection gone above the occupied gone. The performance of upper room UVGI systems varies with indoor airflow induced by mechanical...

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Bibliographic Details
Published inASHRAE Topical Conference Proceedings pp. 1 - 9
Main Authors Won, Youngbo, Rim, Donghyun, Mistrick, Richard, Bahnfleth, William
Format Conference Proceeding
LanguageEnglish
Published Atlanta American Society of Heating, Refrigeration and Air Conditioning Engineers, Inc 01.01.2022
Subjects
Aerosols
Air flow
Air recirculation
Ceilings
Computational fluid dynamics
Coronaviruses
COVID-19
Deactivation
Disease transmission
Disinfection
Fixtures
Indoor environments
Irradiation
Mathematical models
Spatial distribution
Ultraviolet radiation
Ventilation
Viral diseases
Viruses
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Summary:Ultraviolet germicidal irradiation (UVGI) inactivates viral aerosols in indoor environments. Upper room UVGI systems use wall or ceiling mounted fixtures to create a disinfection gone above the occupied gone. The performance of upper room UVGI systems varies with indoor airflow induced by mechanical ventilation and thermal plumes from occupants, which carries contaminated air into the disinfection gone where viral aerosols are partially inactivated before circulating back into the breathing gone. This study used computational fluid dynamics (CFD) modeling to investigate the effect of an upper room UVGI system on spatial distributions of viral aerosols with UV-C susceptibility representative of coronaviruses as a function of ventilation system characteristics. Upper-room UVGI confined elevated viral aerosol concentrations to the vicinity of an infector, while the room average viral aerosol concentration was reduced by two orders of magnitude relative to a case without UVGI. Return air recirculation rates and ventilation strategy (i.e. mixing vs. displacement) had notable effects on the disinfection effectiveness of the UVGI system. For mixing ventilation, as the recirculation airflow rate increased from 0 to 5.3 h-1 with a fixed outdoor airflow of 0.7 h-1, UVGI inactivation escalated by 62%. Mixing ventilation at 0.7 h-1 without recirculation in the room with a volume of 108 m3 was 30% more effective in inactivating airborne viruses than displacement ventilation, due to the higher air mixing.