Experimental analysis of flow and convective heat transfer in the water-cooled packed pebble bed nuclear reactor core

A randomly packed pebble bed test facility is set up to study the flow and convective heat transfer in the water-cooled pebble-bed type nuclear reactor core. Water is used as the test fluid. The electrical induction heating system provides internal heat source for the packed pebble bed. The effects of input power, porosity, fluid velocity and inlet temperature are studied on the flow resistance and convective heat transfer coefficients. A new correlation is proposed to predict the pressure drop in the random packed pebble bed. The correlations given by Wakao et al. and KTA agree well with the experimental convective heat transfer coefficients in the high-velocity and low-velocity conditions respectively. A new correlation is presented based on the trend similarity between the Colburn j factor and friction factor, to predict the pebble bed convective heat transfer characteristics, with a discrepancy no more than 10%.