Dynamic characteristics of molten droplets and hot particles falling in liquid pool

Abstract

The dynamic characteristics of molten droplets and hot particles at the very beginning of their fall into coolant pools are presented. The falling course of a single droplet or a single hot particle was recorded by a highspeed camera and a curve of velocity vs. time was obtained. Emphasis was placed on the effects of the droplet's size and temperature, the coolant's temperature and properties, and the droplet's physical properties on the moving behavior. The results for the all cases showed that the velocity of a falling droplet/particle decreased rapidly but rebounded shortly, at the beginning of droplet/particle falling in the coolant. Following such a V-shaped evolution in velocity, the droplet/particle slows down gradually to a comparatively steady velocity. An increase in either coolant temperature or droplet temperature results in a larger velocity variation in the "J-region", but a smaller deceleration when it moves out of the "J-region". The elevated volatility of a coolant leads to a steeper deceleration in the "J-region" and beyond. The bigger size of a particle leads to a greater velocity variation in the "J-region" and terminal velocity. A high melting point and thermal conductivity as well as lower heat capacity contribute to dramatic variation in the "J-region" and low terminal velocity.