Melting of phase change materials inside periodic cellular structures fabricated by additive manufacturing: Experimental results and numerical simulations

An experimental and numerical study of the solid–liquid phase change process of three paraffin waxes, having different characteristic melting temperatures (42, 55, and 64 °C) embedded in two different cellular periodic aluminium structures fabricated by additive manufacturing, thought of as passive heat sinks, is reported. The aluminium solid media are composed of repeating elementary cells derived from the body-centred cubic (BCC) model and have a porosity of 87%. The samples were tested in an upright position and laterally heated by applying three different heat fluxes (10, 15, and 20 kW m−2). The experimental results showed the effects of the heat flux, melting temperature, and size of the metal cells on the temperature of the heated surface. Numerical simulations were performed to validate a simplified model for the thermal analysis of the test modules using reduced domains. Owing to the characteristics of the experimental melting front, which is almost parallel to the heated side, suggesting a negligible effect of natural convection, the numerical simulations performed with ANSYS Fluent could be conducted on computational domains that represent only small repetitive portions of the test modules, thus allowing substantial savings in the computational time. This simplified method has been proven to yield results that are in good agreement with the experimental data. Based on the numerical results, when the metal structure is finer, the evolution is faster, and the time required to completely melt the phase change material (PCM) is shorter. This numerical model may be confidently used by thermal engineers to design PCM-based heat sinks for electronics cooling. Finally, an empirical model previously developed for paraffin embedded in metal foams was applied to the present paraffin-BCC composite structures.