Title: Evaporation Model and Analysis for Sessile Drops
Students: Joe Chen and Daniel Villamizar (Spring 2013); Taylor Piske (Summer 2015)
Advisors: Dr. Peter Kelly-Zion, Dr. Chris Pursell and Dr. Hoa Nguyen
Abstract:
Evaporation is an important phenomenon in a great many applications including cooling, coating and painting, preparing fuel for combustion, and remediating toxic spills. The study of the evaporation of a sessile drop, which is a drop resting on a solid substrate as shown in Fig. 1, is important not only because of the important physics that can be learned but also because of the potential for sessile drop evaporation to have a key role in important emerging applications such as DNA stretching and depositing, self-assembly and patterning, and nano-wire fabrication.
In general, the evaporation of a sessile drop involves mass and thermal energy transport in both the liquid and vapor phases, and the transport may occur by diffusion (a molecular-scale process) and/or convection (a bulk process). Thermal transport by radiation can also be important, depending on the ambient conditions. Because of the complexities caused by the interdependencies of the transport equations, an analytical solution for the rate of evaporation does not exist except for the much simplified case of the evaporation of a circular drop in which the vapor transport by diffusion dominates all of the other transport processes so that the others can be neglected. This simple case has been shown to be applicable for the evaporation of a sessile water drop under ambient conditions but not for volatile hydrocarbon drops, for which convection of the vapor, in addition to diffusion, has been shown to be important.
The interaction of diffusion and convection in the vapor phase and their effects on the evaporation rate are a focus of ongoing research at Trinity. To support this research, a numerical model of the evaporation process will be beneficial. Eventually, all of the important transport processes will be incorporated into the model, but initially the model will contain only diffusive vapor transport. The geometry of the drop also will be simplified as a disk for the initial model. The goal is to develop the initial, diffusion-limited numerical model and to demonstrate that it accurately computes: 1) the overall evaporation rate, 2) the distribution of the evaporative flux along the surface of the drop (disk), and 3) the distribution of the vapor concentration above the drop.
Student Final Presentation (Spring 2013)
Student Final Report (Spring 2013)
Student Final Presentation (Summer 2015)
