Rapid vapor generation during contact of a liquid droplet with a hot surface

Nishida, Takuya*; Mitsutake, Yuichi*; Monde, Masanori*; Kurihara, Akikazu 

Rapid vapor generation during impact of a single ethanol droplet on a hot surface was observed for well understanding of wetting phenomena. Photographs during a single droplet impacting on a surface at 190-210 C were taken by a high speed digital camera with a microscope. Copper and carbon steel were used for the surface material. The liquid subcooling was varied from 10 to 50 K. The boiling situation changes from nucleate boiling to film boiling like as the boiling transition in pool boiling. Delay time to develop vapor film on the hot surface was measured from the observations. While the delay time increases with increase of subcooling and decrease of thermal inertia of the soild for the lower surface temperature, it shows constant for the higher surface temperature above the superheat limit of liquid.