Numerical investigation on conjugate heat transfer of evaporating thin film in a sessile droplet

The conjugate heat transfer in the evaporating thin films of sessile water droplets with different radii (R = 0.0707, 0.1414, and 0.707 mm, respectively) is numerically investigated based on an augmented Young-Laplace model and the kinetic theory-based expression for mass transport across a liquid-vapor interface by considering the evaporation at the liquid-vapor interface, vapor transport in air, and the liquid domain. The results show that the percentage contribution of the thin film region to the overall heat transfer increases significantly with decreasing droplet size. The thin film contribution becomes somewhat smaller when increasing the superheats that are smaller than 10 K, although the variation of the thin film contribution seems to be less sensitive to superheat than droplet size. Meanwhile, the thin film contribution increases when the surface wettability improves, and its variation is relatively less sensitive to wettability than both droplet size and superheat. This work is helpful for further understanding of the mechanisms influencing the heat transfer in the thin films of liquid droplets.