The Influence of Gas–Liquid Interfacial Transport Theory on Numerical Modelling of Plasma Activation of Water
J. A. Silsby, S. Šimon, James L. Walsh, M. I. Hasan
Abstract
Abstract Plasma activated water has shown great promise in a number of emerging application domains; yet the interaction between non-equilibrium plasma and liquid represents a complex multiphase process that is difficult to probe experimentally, necessitating the development of accurate numerical models. In this work, a global computational model was developed to follow the concentrations of aqueous reactive species in water treated using a surface barrier discharge in ambient air. While the two-film theory has long superseded other methods of modelling mass transfer in such areas of research as environmental and aerosol science, plasma modelling studies continue to use equilibrium and one-film theories. The transport of reactive species across the gas–liquid interface was therefore treated using the one-film and two-film theories, with the results compared to ascertain which is most appropriate for PAW modelling studies. Comparing the model-predicted concentrations to those measured, it was shown that concentrations of aqueous H + and NO 3 − ions were better represented by the two-film theory, more closely fitting experimental measurements in trend and in magnitude by a factor of ten, while HNO 2 and NO 2 − showed a slightly worse fit using this theory. This is attributed to the assumption in two-film theory of a gas-phase stagnant film which provides additional resistance to the absorption of hydrophilic species, which is absent in the one-film theory, which could be improved with a more accurate value of the Sherwood number for each species.