Thermal and mass transfer resistance at a liquid-gas interface of an evaporating droplet: A molecular dynamics study

JG Plascencia and E Bird and Z Liang, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 192, 122867 (2022).

DOI: 10.1016/j.ijheatmasstransfer.2022.122867

Thermal and mass transfer resistance at a liquid-gas interface could strongly affect the evaporation of a micro/nanodroplet. One of the challenges in the investigation of heat and mass transfer across liquid- gas interfaces is that there are two heat transfer modes, namely, evaporation and heat conduction, at an evaporating liquid surface. Interfacial heat conduction was often overlooked in the analysis of evaporation of a liquid droplet. In this work, we derive the analytical expressions for the resistance to the heat and mass flow across a liquid-gas interface of an evaporating droplet from the kinetic theory of gases and verify the theoretical predictions by comparing them to molecular dynamics simulation results. The modeling results show that the temperature jump across the evaporating droplet surface is mainly associated with interfacial heat conduction rather than evaporation, and the vapor density near the liquid-gas interface is determined by the resistance to mass transfer, i.e., evaporation, at the interface. Using the expressions for interfacial thermal and mass transfer resistance, we formulate the temperature jump and vapor density boundary conditions at an evaporating droplet surface and determine the scenario under which the conventional assumptions of continuous temperature profile and saturated vapor at the liquid-gas interface become invalid.

Return to Publications page