CFD Investigation of helium gas flow in sphere packed (Pebble bed) in a rectangular canister using OpenFOAM

Abstract

The lead-lithium cooled ceramic breeder uses spherical lithium titanate pebbles, which act as the breeder for generating tritium as the fuel for nuclear fusion reaction and helium as the purging gas. In this work, the flow-field of helium gas and temperature distribution inside a rectangular canister is investigated numerically, considering the pebble bed as the porous medium. In the numerical model, the local thermal non-equilibrium (LTNE) is assumed to exist between the pebbles and the purging gas, and a local porosity distribution is considered. Considering the radiation effect, a heterogeneous and LTNE based solver developed in OpenFOAM software is validated with the published results. Further, the effects of different heat generation rates, mass flow rates, and packing arrangements (random and uniform arrangements, i.e. BCC and FCC) on the flow-field and temperature profile are studied. The BCC and FCC packing arrangements have better purging behaviour than random packing. Further, the effect of inlet and outlet configuration is evaluated to find the optimal locations for uniform distributions of purging gas in the canister. With a higher value of area-weighted average velocity, the diagonally opposite inlet-outlet is the best choice for removing tritium from the packed bed.