Wettability and Evaporation Dynamics of Sessile Oil Droplets on Heated Surfaces

The evaporation of sessile oil droplets plays an important role in several industrial applications. Fluids such as coconut, canola, and other edible oils possess distinct initial contact angle, spreading and evaporative dynamics compared to water and silicone oils and are unaddressed. In general, the oil droplets are multicomponent and undergo evaporation beyond 160 ^oC. We performed the experiments for seven different oils using a contact angle meter, thermography, and particle imaging velocimetry to understand the complete spreading and evaporation dynamics. Our results capture the effect of fluid properties and surface characteristics on the modes of evaporation and contact line dynamics. Interestingly, we observed the initial contact angle of the droplet increase with an increase in temperature on the PTFE surfaces in the order of θ ∝ Boⁿ. The exponent (n) varies for each oil. Moreover, we identified three distinct modes of evaporation (CCA, CCR, SS) over time.