Thermal Patterns and Hydrothermal Waves (HTWs) in Volatile Drops

Experimental measurements of temperature and heat flux at the liquid-wall interface during the evaporation of sessile FC-72 droplets have been reported for the first time using infrared (IR) thermography. Simultaneous high-speed imaging of the evaporating drop was carried out to monitor the drop profile. The study demonstrates that recently evidenced hydrothermal waves are actually bulk waves that extend across the entire droplet volume. More importantly, thermal patterns occurring in the bulk of the drop affect the temperature and heat-flux distributions on the solid substrate and ultimately influence the droplet evaporation rate. These effects were found to be increasingly pronounced as the substrate temperature was raised. The implications for heat-transfer mechanisms and energy transport are discussed.