Mathematical model based on the radiosity method for estimating the efficiency of in-duct UVGI systems

The article describes a model for calculating the killing ratio of different pathogens with an in-duct ultraviolet (UV) device. The model is based on the radiosity method adapted for the UV radiation range and can be used for analyzing any lamp distribution. The paper provides the necessary view factors and the influence of environmental variables (temperature, humidity and air velocity) in the analysis. The model has been validated using the results of four commercial equipment certificates issued by the US Environmental Protection Agency (EPA). The model results show a high precision on the test results, with a maximum deviation of 9%. In all cases, the model results are lower than that of the test, which allows being on the side of safety in the design. The model has been programmed in software used by Steril-Air for designing its equipment. Finally, an example of calculating the SARS-CoV-2 killing ratio with a 4 x 2 lamps arrangement is shown.