Heat transfer and fluid flow of helium coolant in a model of the core zone of a pebble-bed nuclear reactor

Highlights: • Convective heat transfer in the core zone of a pebble-bed nuclear reactor was modeled. • k-eps RNG model of turbulence was used in simulations. • The model was successfully validated against experimental data. • Unsteady/steady-state modes of operation of the reactor core zone were studied. Using the RNG k-ε model of turbulence in the approximation for porous media, a numerical study of fluid flow and heat transfer in a model of the core zone of a pebble-bed nuclear reactor was performed. Validations of the results of simulations against experimental data (for the friction factor) and analytical solutions (for the velocity profiles) confirmed applicability of the RNG k-ε model of turbulence for the stated problem. An unsteady mode of operation with a decrease in the coolant mass flowrate at the inlet to the reactor core zone model, as well as a steady-state mode were studied. The effect of the pebble bed permeability on the dynamics of flow temperature variation was also investigated.