A Study of Liquid Flashing Phenomenon Under Rapid Depressurization

抄録

In order to investigate the fundamental features of the pool flashing phenomenon of superheated liquids under rapid depressurization, blowdown experiments have been carried out by quickly opening a solenoid valve of an orifice in the top of a pyrex glass vessel. A modified heterogeneous nucleation theory using the pressure relaxation time, in which the initial depressurization process is approximated by an exponential function of time, has been set up for the prediction of the limits of superheat concerning the inception of flashing nucleation. Experimental results indicate that (1) pressure variations within the vessel are characterized by sudden depressurization and subsequent pressure recovery in several patterns of time history depending upon the vaporization process, (2) the limit of superheat for flashing is estimated to be far below the value predicted by the homogeneous nucleation theory, and (3) the violence of the vapor expulsion process with and without test pieces increases inversely with the pressure relaxation time.