高温面上の液滴衝突時の急速蒸気生成過程

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

西田 拓弥*; 光武 雄一*; 門出 政則*; 栗原 成計 

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

濡れ現象を十分に理解するため、高温面へ単一液滴を衝突させた際の蒸気生成過程を観察した。実態顕微鏡と高速度カメラを用いて、190210Cの表面に単一液滴が衝突する過程を撮影した。高温面の材質には銅及び鋼材を用い、液滴のサブクール度を1050Kの範囲で変化させた。プール沸騰での沸騰遷移のように沸騰様相は核沸騰から膜沸騰へ変化し、高温面での蒸気膜が発達する遅れ時間が写真撮影より測定された。液過熱限界温度を超える高温面への液滴接触時に、サブクール度の増加及び低温面に対する固体熱慣性の減少に伴い遅れ時間が増加した。

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.