Effect of geometrical design on the latent heat cooling properties of a lightweight two-phase composite

Abstract

Latent heat storage materials undergo phase changes to maintain a constant temperature environment and are fast emerging as a passive “green” technology for thermal management. Phase-change materials (PCMs) typically have poor thermal conductivities; however, their response to rapid fluctuations in temperature can be sluggish. Here, we explore the feasibility of adding various aluminum alloy (AlSi10Mg) structures to speed up the thermal response. The cooling performance of various geometries with the same mass density was first investigated, and the best performing geometries were then further optimized to investigate the possible weight savings. Our results indicate that, for unidirectional heat flux, designs with 3D periodicity, such as triply periodic minimal surfaces, do not perform as well as those with 1D (parallel plates) and 2D (honeycombs) periodicity. Furthermore, a strong correlation was found between the cooling performance and the interfacial area density. An expanding melt front, which leads to an increase in the interfacial area for heat transfer over time, and even heat distribution were also observed to be advantageous. After optimization, the honeycomb design with tapered triangular rods surrounded by the PCM matrix was able to achieve greatest weight savings for a given performance requirement. Compared to a thermal management panel consisting solely of the PCM, it was able to keep a heated surface cooler by 90% and also outperformed a pure Al panel despite being more than 40% lighter.