Evaporation and Growth of Multicomponent Droplets in Random Dense Clusters

Abstract

Interaction between evaporating (growing) droplets in binary arrays and large random clusters of droplets of different sizes is analyzed in a quasi-steady approximation using the modified method of expansion into irreducible multipoles. Evaporation and condensation of binary arrays and clusters of droplets (i) composed of volatile components and (ii) composed of a volatile and a nonvolatile component was studied. The analytical and numerical results of the investigation are presented in terms of heat and mass correction factors. Solution of the transient problem is obtained, and the evaporation rate is determined. It is shown that for droplets of ideal solution with different compositions, Nusselt and Sherwood numbers depend on the concentration of components inside each droplet. When dense cloud contains both pure droplets and droplets containing soluble nuclei, interactions between temperature and concentration fields causes growth of some droplets in a cluster and evaporation of the other droplets. It is shown that inside an evaporating large cluster of multicomponent droplets composed of volatile components, recondensation occurs whereby evaporating droplets act as mass sources and heat sinks and growing droplets act as mass sink and heat sources. The results of this study are of relevance in the analysis of dynamics of droplet size distribution in clouds, artificial modification of clouds and precipitation, in-cloud pollutants scavenging, and in the analysis of evaporation and combustion of multicomponent (blended) liquid fuels.