Evaporative cooling of heated solid surfaces: Two-droplet thermal interaction

Evaporative cooling represents a key subject for both academia and industry: the behavior of sessile droplets has been studied in detail over many decades and a large body of literature is currently available on heat-transfer mechanisms. The present work is focused on the thermal transient occurring as one or two water droplets are gently released (We < 30) onto a heated solid surface; moreover, the single-phase-evaporation regime is here considered. Infrared thermography has been employed to perform experimental measurements of the temperature trend at the solid-liquid interface: a suitable facility has been built to carry out measurements from below, thus introducing a fully non-intrusive approach. As the numerical task of this study, a computational code has been developed to predict the entire evaporation mechanism together with the thermal transient of the solid substrate: the three-dimensional energy-diffusion equation has been discretized through the finite-volume method and the simulations have been based on a structured non-uniform mesh. The proposed modeling has been made capable of reproducing both the single- and the multi-droplet configuration. A remarkably good agreement is shown between experimental and numerical outcomes in terms of temperature, thus resulting in a realistic simulation of droplet interaction over both the spatial domain and the time coordinate (evaporation and recovery).