THE INITIAL THERMO-FLUIDDYNAMIC PROCESSES OF BOILING PHENOMENA IN HE-II

A systematic study on a series of thermo-fluiddynamic phenomena in the initial stage leading to boiling in He II is conducted with the aid o f visualization methods and with a superconductive temperature sensor. Following the onset of a stepwise heating, a compression (first sound ) wave and a second sound wave which develops into a thermal shock wav e are emitted. Then high density quantized vortices are generated and accumulate near the heater which cause formation of a thermal boundary layer adjacent to the heater. Finally film boiling starts on the heat er surface following precursory spotwise boiling. It is emphasized in the present study that such visualization methods as laser holographic interferometry and shadowgraph method, and a superconductive temperat ure sensor are complementarily utilized to investigate the thermo-flui ddynamic phenomena which result from a stepwise heating at a rather la rge heat flux from a planer heater.