A fundamental analysis of the influence of the geometrical properties on the effective thermal conductivity of open-cell foams

Structured catalysts have been proposed as a suitable solution for the efficient management of strongly exo- and endothermic processes. Among these structures, open-cell foams are considered as one of the most promising candidates as catalyst supports. In this work, we investigated the heat transfer in the solid matrix of open-cell foams by means of 3D numerical simulations carried out on virtually reconstructed structures. The totally interconnected solid matrix promotes high heat transfer rates because the conduction in the solid matrix is the main contribution to the heat transport. Our analysis reveals that the void fraction is the controlling parameter for the performances of the structures. An engineering correlation for the effective solid thermal conductivity has been derived, enabling a rational design of the foam geometry. Moreover, we analyzed the effect of the ratio between the node and strut diameters. We found that it has a strong influence on the heat conduction performance. High ratios penalize the heat transfer due to the reduced strut cross-section area at fixed porosity. On the other hand, an advanced design with a node-to-strut diameter ratio close to one can enhance the effective heat conductivity of open-cell foams up to 30%, improving the reactor performances compared to conventional open cell foams.