Computational fluid dynamics modelling of UR-UVGI lamp effectiveness to promote disinfection of airborne microorganisms

Abstract

This paper focuses on using computational fluid dynamics (CFD) modelling methods to study the effectiveness of upper-room ultraviolet germicidal irradiation (UR-UVGI) lamps in healthcare facilities. This work develops and uses simplifications for boundary conditions in CFD, while details of UR-UVGI lamps and microorganism characteristics were obtained from existing experimental studies. Three approximation methods were developed to implement the effects of UR-UVGI lamps on microorganism dispersion patterns represented with the Eulerian and the Lagrangian methods in CFD simulations. Then, a non-dimensional parameter, the UR-UVGI effectiveness, was introduced to study the effectiveness of UR-UVGI lamp(s) disinfection process with respect to the combined effect of UR-UVGI lamp(s) and ventilation systems. Although comparisons of results obtained from CFD simulations and experimental data show that local microorganism numbers/concentrations depend on boundary condition modelling methods, global variables such as the fraction of remaining microorganisms remain relatively unchanged and in a good agreement with the measured data.

A validated numerical investigation of the ceiling fan's role in the upper-room UVGI efficacy

“…The Eulerian method has been widely applied to performance predictions of upper room UVGI systems in a steady indoor environment in previous studies [6,18]. The method is based on the notion that microorganisms occupy a certain fraction of the air volume.…”

“…To repair this, we wrote a user-defined function to restrict the fluence rate only within the irradiated zone (Z ¼ 2.13e2.85 m) after import. The effect of fluence rate modeling representation on the predictions of UVGI efficiency was studied by Heidarinejad and Srebric [18], who found that a manual, multi-volume segregation of the fluence rate was sufficiently accurate. The direct import, used here, offers better detail and saves the effort for manually partitioning the irradiated zone.…”

“…The evaporation of droplets was not considered, and it was not included in the present study because microorganisms were nebulized and the liquid evaporated almost immediately. In previous research, particle settling and wall absorption have been found to be negligible by Heidarinejad and Srebric [18], so these transport phenomena were not included.…”

Upper room UVGI effectiveness with dispersed pathogens at different droplet sizes in spaces conditioned by chilled ceiling and mixed displacement ventilation system

“…Throughout the literature review, this model can well predict the transport and dispersion of particles and bioaerosols in indoor environments [19,20]. Pathogen-carrying droplets are simulated as inert spherical particles, 2.5 mm in diameter, with density of 1000 kg/m 3 .…”

“…Hathway et al [19] evaluated using CFD modeling the risk from the transport of infectious bioaerosols in spaces with conventional air conditioning. Heidarinijad and Srebric [20] presented different CFD modeling methods of upper room UVGI effectiveness. The obtained CFD results were then compared with existing experimental studies.…”