Improving the effectiveness of ultraviolet germicidal irradiation through reflective wall coatings: Experimental and modeling based assessments

Experimental and modeling based assessments of employing reflective wall coatings towards improving the effectiveness of ultraviolet germicidal irradiation in unoccupied hospital rooms were carried out. Measurements of incident radiative fluxes on different surfaces were made in a control room as well as a room whose walls were painted with a nanostructured UV-C reflective wall coating. Employing the reflective paint resulted in up to a 20% increase in the incident radiative fluxes on some surfaces that were directly exposed to the radiation and nearly a 10-fold increase on surfaces that were not directly exposed. Spatially and directionally well-resolved simulations of radiative transfer within the rooms were carried out employing the finite volume radiation model. The measured enhancement in radiative fluxes predicted numerically agreed in general with experimental observations. The volume-averaged incident radiation increased by 60% in the presence of UV reflective walls. Ray effects or the preferential streaming of radiation in the numerical calculations was more pronounced in the control room and was minimized by increasing the angular resolution of the calculations even further. However in the room with UV reflective walls, the diffuse reflections caused the intensity distributions to become more isotropic and minimized the impacts of ray effects.