Generalized correlation for effective thermal conductivity of high porosity architectured materials and metal foams

Abstract

This paper presents a numerical study on the effective thermal conductivity (keff) of architectured materials typically realized through additive manufacturing. Four different unit cell topologies- Cube, Octet, Face-diagonal Cube, and Tetrakaidecahedron, were simulated for a range of porosity values, and both solid- and fluid-phase thermal conductivities. Numerically predicted keff values were validated against the in-house experiments carried out on single-cell thick 5 × 5 unit cell arrangement samples. These simulations led to a correlation for keff as a function of lattice porosity and thermal conductivities of solid- and fluid-phase materials. For the solid-to-fluid thermal conductivity ratio (ks/kf) greater than 300, the keff showed dependence on only the solid thermal conductivity for any given porosity and unit cell topology. The proposed correlation for the keff of architectured materials is applicable to all the four unit cell topologies with porosities > 0.8, and ks/kf ranging from 102 to 104. For these parameters, the correlation can also predict the keff of high-porosity metal foams obtained via foaming process with an accuracy of ±10%.