A DEM-CFD numerical model for the prediction of the effective thermal conductivity of pebble beds with contact conduction

Pebble beds are main schemes for tritium breeding zones in the solid blanket for fusion reactors. The effective thermal conductivity of pebble beds (k(eff)) is an important thermal property used in the thermal hydraulic design of solid blankets. In this study, a 3D DEM-CFD one-way coupling method considering contact conduction is applied to analyze the influence of solid contact conduction and solid-fluid-solid conduction on the effective thermal conductivity of pebble beds. The current numerical model gives a k(eff) consistent with experimental data in a wide range of solid-to-fluid conductivity ratio k(s)/k(f) from 1 to 10,000. It can be concluded that when the k(s)/k(f) is more than 20, contact conduction should be taken into account to make a good prediction for k(eff).