A new mathematical model for irradiance field prediction of upper-room ultraviolet germicidal systems

Highlights: → We propose a new mathematical model to evaluate the irradiance filed of upper-room UVGI systems. → The model prediction agrees well with experiment measurements at different louver configurations. → Ignoring the reflector by bare lamp model gives an 25% under-prediction of the UV intensity. → The louver and fixture sidewall also have great influence on the irradiance field. - Abstract: There has been an increasing interest in the use of upper-room ultraviolet germicidal irradiation (UVGI) system because of its proven disinfection effect for airborne microorganisms. To better design and explore further potential applications of UVGI systems, it is of critical importance to predict the spatial UV intensity in enclosures. In this paper, we developed a new mathematical model to predict spatial radiation intensity for upper-room ultraviolet germicidal irradiation systems. The detail geometries of the lamp and the reflector were removed and replaced by introducing a fictitious irradiation surface near louver slots. The view factor approach was applied to evaluate the UV irradiance in a three-dimensional space with different louver configurations. With this approach no detail meshing of the fixture is required and this leads to significant simplification of the entire systems from modeling perspectives. To validate the model, experiments were performed in a full-scale environmental controlled chamber in which one UVGI fixture was mounted on a sidewall. The UV irradiance was measured by a radiometer. The results predicted by the present model agree very well with the experimental measurements. Factors affect the accuracy of the model was also discussed.