An Investigation of the Evaporation Dynamics of Water Droplets and Na-Cl Water Droplets Suspended in Air by Acoustic Levitation
Evaporation of liquid droplets is ubiquitous in nature and has been used across several industrial processes. Many evaporation studies of supported droplets have been done through time, starting with investigations of sessile droplets on solid surfaces, to droplets hanging on thin filaments, to droplets supported on superhydrophobic materials. An emerging method to study free droplets is by using acoustic levitation, a tool that has allowed for investigations of evaporation and crystallization of true free droplets. In the first part of the study, the evaporation of pure water is first investigated and compared to a novel theory for droplet evaporation which includes both diffusive transport away from the system and thermal conduction into it. The results demonstrate that the major control on the evaporation rate is diffusion. In the second part of the study, the evaporation and crystallization dynamics of NaCl water solution droplets is examined with different concentrations. Qualitative results describe the crystallization process and the ‘cup’ shape produced for NaCl concentration ranging from 225-300 g/L. Higher concentration (325 g/L) yield a crystal sphere around the droplet. Quantitative findings compared to theory shows that the NaCl solutions require an enhanced diffusion coefficient to better match the experimental data.
Acoustic levitation, Water evaporation, Droplet evaporation, water droplet, contactless processing, NaCl-water droplet, Salt Crystallization
Bunio, L. (2020). An Investigation of the Evaporation Dynamics of Water Droplets and Na-Cl Water Droplets Suspended in Air by Acoustic Levitation (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.