Experimental Investigation to Study Surface Quenching Behavior

Study of surface quenching is of interest particular in the context of emergency core cooling of a nuclear reactor under LOCA conditions. Rewetting is a phenomenon which occurs during the quenching of hot surfaces of high temperature. Rewetting of surface occurs at minimum film boiling point where liquid established direct contact with a hot dry surface. The present investigation deals with experimental investigations on the quenching behavior of a hot horizontal stainless steel surface of 0.25 mm thickness with water jet of 22ºC temperature. Initially, test surface is heated up to 800ºC and water jet is injected through a straight tubes nozzle of 2.5 mm diameter. The observations are made up to 16 mm downstream locations away from the stagnation point. The nozzle exit to surface spacing is kept in the range of 4-16 times of nozzle diameter and Reynolds number in the range of 5000-24000. Rewetting temperature, rewetting velocity and wetting delay are some of the parameters over which rewetting phenomenon has been investigated. During quenching initially, a wet patch was observed at the stagnation point, which progress in downstream direction only when the surface was cooled up to the rewetting temperature. The Rewetting temperature, rewetting velocity both increases with the rise in Reynolds number, however, the wetting delay reduces. This effect is more pronounced for downstream locations away from the stagnation point.