Modelling of the interaction between a falling n-heptane droplet and hot solid surface

Abstract

Accurate prediction of the interactions between evaporating liquid droplets and solids are critical for many industrially important processes. A model based on coupled Level Set-Volume of Fluid approach was developed to simulate the interaction of evaporating liquid droplets with hot solid surfaces. The model incorporates appropriate source terms in the multiphase calculations to account for the heat and mass transfer. Accurate and stable numerical procedure was developed and incorporated in open source solver OpenFOAM. A brief discussion on the model development along with several key issues that are associated with this process was presented.The resulting numerical model was validated through the experimental data of Chandra and Avedisian (Chandra, S., Avedisian, C.T., 1991. Proc. R. Soc. Lond., Ser. A 432, 13–41). Although some discrepancies were found between the numerical results and experimental data, the model was found to be capable of reproducing the reduced droplet spreading rate as the temperature of the surface is increased away from the saturation temperature. The decrease in rate of surface wetting results from the combined effects of surface tension, viscous forces and evaporation at the liquid-solid-vapour contact line. Further, the effects of increased pressure at the solid-liquid interface resulting from the rapid evaporation of the liquid, which in some cases can be quite severe such that the liquid gets lifted-off from the surface, were also captured, in good agreement with experimental observations. Finally, the effects of the solid temperature on the evaporation and heat transfer rates of the droplets were presented and analysed.