Effect of diffusion interactions between droplets on gas absorption of highly soluble gases in sprays and droplet clusters

We investigate mass transfer during absorption of highly soluble gases such as HNO₃, H₂O₂by droplets in clusters and sprays in the presence of inert admixtures. Diffusion interactions between droplets, caused by the overlap of depleted of soluble gas regions around the neighboring droplets, are taken into account in the approximation of a cellular model of a gas-droplet suspension whereby a suspension is viewed as a periodic structure consisting of the identical spherical cells with periodic boundary conditions at the cell boundary. Using this model we determined temporal and spatial dependencies of the concentration of the soluble gas in a gaseous phase and in a droplet. The suggested model was also extended for describing gas absorption by atmospheric cloud droplets. We found that scavenging coefficient for gas absorption by cloud droplets remains constant and sharply decreases only at the final stage of absorption. In the calculations we employed a Monte Carlo method and assumed gamma size distribution of cloud droplets. It was shown that despite of the comparable values of Henry's law constants for the hydrogen peroxide (H₂O₂) and the nitric acid (HNO₃), the nitric acid is scavenged more effectively by cloud droplets than the hydrogen peroxide due to a major affect of the dissociation reaction on HNO₃scavenging.