Heat and Mass Transfer of Droplets in a Gas Environment

A numerical simulation of the evaporation of a water droplet in dry air and superheated steam was performed, both with and without consideration of convective heat transfer in the dispersed liquid phase. It was found that during droplet evaporation in air, the thermal resistance within the droplet can be considered negligible compared to that of the continuous gas phase, whereas during droplet evaporation in superheated steam, internal heat transfer plays a decisive role in the droplet heating and cooling processes. In superheated steam, the duration of the nonequilibrium stage of evaporation or condensation is two orders of magnitude shorter than in dry air. Accordingly, the rate of evaporation or droplet growth in superheated steam is two orders of magnitude higher than in air.