Study of Film Collapse Behavior during Vapor Explosion.

Abstract

Fundamental experiments were conducted to clarify the collapse conditions of film boiling on a high temperature solid ball surface, which simulated the pre-mixing condition of film boiling on high temperature molten materials coarsely mixing in low boiling point liquid. In the present experiment, surface temperature on the ball and pressure transient around the ball are simultaneously measured. As the results of the present experiments, surface temperature on the ball sharply decreased when the pressure wave passed through the film boiling on the ball surface. The steam film thickness established from the heat flux calculated by the heat conduction calculation decreases at the time of the sharp temperature decrease. The present study shows that the film boiling collapse behavior could be categorized into three types in case of stainless steel ball from the characteristics of heat release, surface temperature and pressure transients. The established heat flux at the minimum film thickness is much higher than the critical heat flux at the atmospheric pressure. This result indicates that the special consideration is needed to change the heat transfer mode at the trigger in the calculation by the detonation mode.