Inactivation of airborne bacteria by cold plasma in air duct flow

This paper developed a numerical model for predicting bacteria inactivation by cold plasma tube. The bulk air velocity, ion mobility, electric field and ion diffusion were considered in the model to obtain the distribution of negative ions. The sink term appeared in the model was determined by a semi-empirical approach through experiment. A 9-m long, 200 mm square duct was used for carrying out experiments. Negative ion concentration along the duct and inactivation rate of E. coli was measured. Based on the inactivation rate, the sink term was estimated and fed to the model. Three different device installation scenarios were investigated: single plasma unit, two plasma tubes arranged in horizontal and finally two plasma arranged in vertical orientations. The simulation results were agreed well with site measurement of ion intensities as well as pathogen inactivation experiments, an application of cold plasma in a single hospital ward was discussed. The developed model can be applied to advanced disinfection technologies in HVAC systems, besides, the method for modeling the bacteria can be expanded to other microorganisms. Limitations of the model are also discussed.