An experimental study on the quenching phenomena of hemispherical downward facing convex surfaces with narrow gaps

Quenching phenomena of hemispherical downward facing convex surface with narrow gaps with respect to the wall heating conditions have been investigated experimentally. Experiments employed test sections having 1 and 2 mm in gap thickness and atmospheric system pressure condition according to wall heating conditions. From interpretations of the temperature and heat flux history, the quenching phenomena were investigated. From interpretations of the temperature and the heat flux history, it was found that the quenching process was changed by wall heating conditions. If external wall was not heated, then the coolant was penetrated along the cooled external wall. However, if both internal and external wall were heated, then the quenching phenomena were more complicated as the gap thickness decreased. All quenching processes were propagated from lower to upper regions, and the flooding inside the gap was restricted by effective inlet flow area. The ratio of the maximum heat fluxes at 1mm to 2mm in gap thickness was the almost same that obtained by steady state experiments. The quenching scenario of the hemispherical downward facing surface with narrow gap was suggested, and main parameters of quenching phenomena in hemispherical narrow gaps were summarized. The experimental results, that is, the temporal temperature and the heat flux variations, will be directly applied to modelling on the quenching phenomena in hemispherical narrow gap as basic data