Spraying ozonated water: mass transfer characterization from the atomizing liquid film to the cloud of droplets
Résumé
The present work proposes a fully characterization of the mass transfer occurring in a spray. First, a global method that relies on the collection and the titration of the sprayed liquid along the spray is presented. Ozone desorption and dioxygen absorption rates are determined and found to be equal. Moreover, for both solutes, most of the mass transfer (≈70%) occurred in the atomizing liquid film that form the droplets at the direct exit of the nozzle. General correlations allowed to predict the desorption occurring in the already formed droplets, but not during their formation in the liquid film. Then, an original local method based on light absorption through a dioxygen sensitive dye (resazurin) has been developed to locally assess the mass transfer in this atomizing liquid film. Measurements confirmed that the transfer occurring in the small region is quite strong. From the complementarity of both the global and local approaches, the mass transfer of ozone can be fully predicted, from the direct exit of the nozzle (2-3cm) to the cloud of droplets (80cm-1m) produced by a spray. This understanding allows to prepare adequate ozone doses for plants treatments and would allow propositions of technical solutions to create anti-desorption devices for the spraying of OW.
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