Effect of a triple contact line on the thermokinetics of dropwise condensation on an immiscible liquid surface

Abstract

Within the framework of classical nucleation theory, a thermokinetic model is developed for the line-tension-associated condensation on an immiscible liquid substrate considering both interfacial and peripheral molecular transport. Along with the free energy minimization principle, a modified classical theory, based on detailed balance analysis, has been employed to determine relevant thermokinetic parameters for heterogeneous nucleation of water droplets as a function of the pseudo-contact angle, submergence angle, and equivalent Young's contact angle. A triple contact line is found to have a considerable effect on both thermodynamics with the associated line tension and kinetics with the related peripheral molecular transport. The growth rate of the formed droplet increases for lower values of the pseudo-contact angle and submergence angle. Besides, positive line tension increases for higher values of the pseudo-contact angle and submergence angle and lower values of the equivalent Young's contact angle, while negative line tension exhibits a reverse trend. With decreasing pseudo-contact angle and submergence angle and increasing equivalent Young's contact angle, the free energy barrier decreases appreciably. Subsequently, the rate of nucleation increases which, in turn, suggests the possibility of condensation enhancement under such conditions. Using the heterogeneous nucleation experimental data, the present thermokinetic formulation is capable of estimating the values of microscopic contact angles and line tension of a given lenticular three-phase system.