Thermal Migration of Liquid Droplets through Solids

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Abstract
A transparent solid and liquid were chosen to study the thermomigration of liquid droplets through solids. Irreversible processes associated with the transfer of atoms between the solid and the liquid phases at the solid‐liquid interface of the droplet were found to have a profound influence on the migration behavior of the liquid droplets. For large droplets, these interface kinetics cause the droplet to disintegrate in a thermal gradient. In smaller droplets where the containing effects of surface tension are relatively greater, the droplets experience a prolonged transient period of thermomigration during which there is a monotonic increase in the velocity of the droplet and a gradual distortion of the droplet shape. Following this transient period, the smaller drops enter a steady‐state period during which both their shape and velocity remain constant. The steady‐state velocity of droplets in this region decreases with decreasing droplet volume and falls to zero below a critical droplet size. This variation of droplet velocity with size produces an increased rate of collision and coalescence of droplets during thermomigration.