Rewetting and Boiling in Water Jet Impingement on High Temperature Steel Surface

Abstract

For the first time, high-speed imaging (20 kfps) from the boiling phenomenon within water jet impingement zone during quenching of a high temperature (300°C-900°C) steel plate was observed. The inverse heat conduction method gave the heat flux and the temperature at the plate surface from temperatures measured with thermocouples inserted into the plate. Surprisingly, gas bubbles, from a degassing process, on top of a thin vapor film have been observed. Surface roughness induces the occurrence of rewetting on surface temperatures above the critical point of water. For an initial surface temperature of 300°C, rewetting phenomenon took place without occurrence of vapor film, but for surfaces at or above 450°C, even in very high jet subcooling of 80K, vapor film formation was observed. In spite of high subcooling and velocity of jet, an intense vapor bubble activity was observed within wet region and ceased at surface temperature of 246°C for subcooling of 80K. Temperature and time of rewetting are strongly affected by the initial surface temperature and jet subcooling and, less intensely, by jet velocity.