Multiscale modeling of microdroplet evaporation and single pulse spray cooling

This work provides a multiscale model for accurate descriptions of the heat and mass transport during single microdroplet evaporation and single pulse spray cooling on a heated semi-infinite solid. The temperature drop from a high-pressure spray pulse is captured through thermocouples and an infrared camera for initial substrate temperatures ranging from negative to positive superheats. A representative average diameter is estimated using high-speed cameras and the droplet size distribution statistics. The model can correctly predict the wall heat flux and evaporation rates from room temperature to positive superheats up to 10 K. At superheats beyond 20 K the model breaks down due to presumably boiling and microlayer evaporation effects. The results highlight the validity of coupling lubrication theory with kinetically-limited and diffusion-limited evaporation over a wide range of temperatures, using the vapor temperature and vapor pressure as the key mediating properties for bridging the molecular-scale forces with continuum-scale thermal physics.