from the conferences organized by TANGER Ltd.
A composite chiller consisting of graphite foam infiltrated with pure zinc as a phase change material (PCM) and enclosed within a steel container was used to enhance heat transfer and accelerate the solidification of an Al-4.5 wt% Cu alloy. Cooling performance was evaluated using numerical simulation based on temperature-time diagrams, along with calculations of thermal gradient (G) and growth rate of the solidification front (R). The results were validated through comparison with available experimental data related to pure zinc as PCM and to conventional steel chillers. The results indicate that the porous foam structure increased the effective surface area and reduced the volume-to-surface ratio, enabling earlier melting of zinc and improving its heat absorption from the molten alloy. The Zn-graphite foam composite enhanced heat extraction during the early stages of solidification, reducing the solidification time compared to the other types of chillers. This promoted an ideal temperature distribution within the completely filled mould cavity, making the subsequent cooling path favourable to feeding. Higher thermal gradients were observed near the composite chiller. In all configurations, G/R decreased from the chiller toward the runner, indicating the potential for a columnar-to-equiaxed transition (CET); however, this reduction was more abrupt in the composite case, suggesting shorter columnar growth and accelerated CET. Consequently, a more equiaxed microstructure with reduced shrinkage defects is expected. Despite using less zinc, the high thermal conductivity of the graphite foam compensated for this reduction, demonstrating the superior efficiency of the Zn-graphite foam composite chiller.
Keywords: Phase Change Material, Composite chiller, Thermal gradient, Cooling rate, Controlled solidified structure© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.