Mechanism of Rewetting Initiation of Hot Dry Surface in Saturated and Subcooled Film Boiling

Abstract

The behavior of rewetting on high superheated surface, focusing on rewetting temperature during collapse of saturated and subcooled film boiling was investigated experimentally and analytically. Saturated and subcooled film-boiling experiments were conducted by using a Silicon wafer with 20 mm length, 20 mm width and 0.5 mm thickness and pure water at atmospheric condition. Both pool boiling and impingement jet experiments were preformed in the present study. Then, the present experimental results were examined by using hydrodynamics instability on liquid-vapor interface (Rayleigth-Tayor instability) and a heat conduction model (rewetting model under a falling-flow of a liquid layer). Some physical parameters on Rayleigh-Taylor instability, for example released period of bubble from vapor film on a heater, generated volume rate of vapor and so on, were estimated by using Two-Phase Boundary Layer theory of saturated and subcooled film boiling. The present analytical results showed that as the liquid subcooling was high, MHF temperature was higher. Namely, the predictions agreed with the present experimental results and Dhir-Purohit’s correlation.