Predicting spatial distribution of ultraviolet irradiance and disinfection of exhaled bioaerosols with a modified irradiance model

Abstract

The transmission of airborne infectious diseases in indoor environments has become a major public health concern. Ultraviolet C lights are effective in inactivating bioaerosols to reduce infection risks. To facilitate the design and application of UVC systems, this study developed a modified irradiance model for calculating the spatial irradiance distribution when unstructured meshes are used for arbitrary reflective surfaces. With the modified irradiance model, the computational fluid dynamics (CFD)-Eulerian model was used to predict the dispersion and UV disinfection of bioaerosols. The proposed model was first preliminarily validated using measured data for in-duct ultraviolet germicidal lamps from the literature. For further validation of the proposed model in a relatively complex environment, experimental measurements of the detailed spatial irradiance distribution and bioaerosol concentration exhaled from a manikin in a ventilated chamber with a far UVC lamp were compared with calculated results. It was found that the proposed modified irradiance model can predict the spatial irradiance distribution reasonably well when unstructured meshes are used for arbitrary reflective surfaces. Furthermore, the modified irradiance model with the CFD-Eulerian model can predict the dispersion and UV disinfection of exhaled bioaerosols in indoor environments reasonably well. Finally, the validated model was used to predict person-to-person influenza A virus transport in a room with a ventilation rate of 3 ACH and a far UVC lamp with an effective output power of 0.34 W. The results show that the far UVC lamp can effectively reduce the receptor's exposure to influenza A virus by 65%.