COLLISION DYNAMICS OF A WATER DROPLET IMPINGING ON A RIGID SURFACE ABOVE THE LEIDENFROST TEMPERATURE

The collision dynamics of a water droplet impinging on a rigid surface above the Leidenfrost temperature are described from an experimental point of view. Emphasis is placed upon the collision of relatively small droplets in the range from 300 to 600 mu m with the surface. The surface temperature is fixed at 500 degrees C. The first purpose of the present study is to examine whether or not the prior empirical rules obtained by using droplets of 2 to 3 mm give an applicability to the case where the droplet size is much smaller. The second is to clarify the relation between the Weber number and the coefficient of restitution, when the droplet rebounds from the hot surface without disintegrating into a number of particles. Also, the maximum value of the diameter of droplet which can spread on the surface and the resident time are examined and discussed by comparing the result obtained here with the prior empirical formulae proposed by a few researchers.