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1D fluid model of the interaction between helium APPJ and deionized water

Atmospheric pressure plasma jets (APPJs) are widely used for the treatment of water-containing substances such as human tissue, leading to a necessity of understanding the interaction between APPJs and water solutions for the development of plasma biomedicine. The reported two- or three-dimensional fluid models are shown to be an effective method for this study. However, owing to the complex chemistry in APPJ-water interaction, little of them could provide a quantitative estimation of reactive species, which are difficult to be measured but of much interest in the applications. In this paper, a one-dimensional fluid model is developed to simulate the interaction between a helium APPJ and deionized water, which incorporates a relatively comprehensive chemistry both in gas and liquid phases but with a moderate computational load. The composition and distribution of reactive species are quantified during a plasma treatment time of 6 min, which is typical in practice. By considering the sidewise loss inside the quartz tube, the air mixing outside the quartz tube, the conductivity of deionized water, and the chlorine evolution reaction, the simulation results agree well with the experiments. It is found that the plasma could be divided into three regions with much different physicochemical properties, mainly due to the sidewise loss, the air mixing and the water evaporation. In plasma-activated water, H2O2aq and HNO2aq/NO2aq − are the dominant reactive species, and OHaq is the key intermediate species for the transformation among other reactive species. Finally, the chemical pathways for the production of aqueous reactive species are elucidated.