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

• A DEM-CFD model considering contact conduction was used to study the effective thermal conductivity (ETC) of pebble beds. • The ETC predicted by the current model is consistent with experimental data in a wide range of k s / k f from 1 to 10000. • If k s / k f is larger than 20, the difference of the ETC for the contact model and the non-contact model is greater than 10%. Pebble beds are main schemes for tritium breeding zones in the solid blanket for fusion reactors. The effective thermal conductivity of pebble beds (k e f f) 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 e f f 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 e f f. [ABSTRACT FROM AUTHOR]