Study on heat transfer characteristics during rewetting of a hot vertical narrow channel part II-the effect of outer wall heat capacity

In the present study, heat transfer characteristics in narrow gaps were analyzed by boiling curves obtained from quenching experiments using annular channels with a narrow gap between inner and outer tubes at the atmospheric pressure. The emphasis was put on discussing the effect of heat capacity of the outer wall on the heat transfer characteristics in gap cooling. The inner rod of the channel was made of stainless steel, and two kinds of outer tubes, quartz glass and stainless steel tubes were used. The gap clearances ranged from 1.0mm to 4.0mm, and the initial temperatures of the wall surface were 800degC. Using measured temperature histories of the inner tube during the rewetting of the narrow channel, local boiling curves of the gap cooling were calculated solving reverse heat conduction problems. The heat transfer characteristics were analyzed by comparing the calculated boiling curves with existing correlations. The effect of heat capacity of the outer tube on the rewetting process in narrow channel was discussed by comparing both boiling curves obtained with quartz glass and stainless steel outer tubes conditions respectively. It was pointed out that for gap 1.0mm condition, the heat capacity of the outer tube on the heat transfer characteristics of rewetting in narrow channel was obvious. (author)