Effect of Turbulence on Ultraviolet Germicidal Irradiation

Abstract

It is shown that in ultraviolet germicidal irradiation (UVGI) systems for air disinfection, where turbulence completely mixes the flow in the directions perpendicular to the net flow direction, turbulence can also act to reduce the effectiveness of the system. This occurs when the longitudinal diffusion coefficient resulting from the turbulence is large enough to reduce the effective transit time of the air through the ultraviolet irradiation zone. At the same time, depending on the radiation fluence, UV kill rate parameter, diffusion coefficient, and flow rate, the longitudinal turbulent diffusion can also increase the effectiveness of the UVGI system. The appropriate combination of parameters for ascertaining whether turbulence reduces or increases UVGI effectiveness is derived.