液滴の蒸発過程に及ぼす表面被覆層の影響

抄録

An experimental study was conducted to investigate the process of evaporation of water droplets on hot metals (silver or stainless steel) whose heat transfer surface was coated with a low thermal conductivity material. The coating thickness was varied from 0 to 0.13mm. The initial diameter and temperature of a droplet were 2.70±0.05mm and 20±3°C, respectively. The coating widened the range of the surface temperature, in which the lifetime of the droplet was shorter than 1 s and also increased the Leidenfrost temperature. This tendency was more accentuated with thicker coating. The better wettability of the coating spread the boiling droplet more widely on the heated surface and caused the lifetime of the droplet shorter. In the superficial nucleate boiling region, the time-averaged heat flux from the heated surface to a droplet increased with superheating of the heated surface. The maximum time-averaged heat flux was observed in a higher temperature region with increasing coating thickness, but its value was approximately 10⁷W/m² for every coating thickness.