Modelling of radiation and flow fields in in-duct ultraviolet germicidal irradiation systems with and without ribs

In-duct ultraviolet germicidal irradiation systems (ID-UVs) is a promising technology for the development of biosecure buildings. This study explored the Computational Fluid Dynamics (CFD) method for accurately predicting the inactivation efficiency of ID-UVs. The results showed that the setting of ‘Divisions’ is crucial to the accuracy of radiation field modelling, and 15 × 15 was considered to be a reasonable value in this study. In addition, residence time and deposition ratio are two crucial parameters determining the average UV dose (AD) received by microbial particles, thereby influencing the inactivation efficiency. For ID-UVs without ribs, the Renormalization Group (RNG) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>k</mml:mi> <mml:mo>‐</mml:mo> <mml:mi>ε</mml:mi> </mml:mrow> </mml:math> model largely overestimated these two parameters, while the Reynolds Stress Model (RSM) with correcting fluctuation velocity improved the predictive accuracy of AD by 10.0%. For ID-UVs with ribs, the RNG <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>k</mml:mi> <mml:mo>‐</mml:mo> <mml:mi>ε</mml:mi> </mml:mrow> </mml:math> model overestimated the eddy size and AD by 28.6% and 12.0%, respectively. The RSM model provided results closer to the Large Eddy Simulation. Adding 0.10 H (H: duct height) ribs increased the inactivation efficiency for MS2 Bacteriophage by 19.0%–64.3%, with an additional pressure drop of only 3.3 Pa. These findings contributed to a reliable CFD framework and provided novel ideas for improving inactivation efficiency.