A comparative study of the performance of lattice structures embedded with phase change materials as thermal conductivity enhancers

Phase Change Materials (PCMs) are increasingly recognized as a viable alternative for passive thermal management, serving as substitutes for traditional heat sinks due to their exceptional thermal properties, particularly their high latent heat capacity. However, their low thermal conductivity presents a significant challenge, specifically in the microgravity environment, where there is only thermal conduction heat transfer. To mitigate this issue, PCMs have been integrated with porous materials, such as open-cell metal foams, which act as Thermal Conductivity Enhancers (TCEs). Lattice structures have emerged as a promising alternative to conventional open-cellular metal foams as TCEs, offering a regularly organized periodic structure that facilitates improved manufacturing. This study investigates four PCM-embedded lattice sandwich panels: Simple, Octa, Octet, and V-cube structures, utilizing the Computational Fluid Dynamics (CFD) method. All these configurations are manufactured with the same total volume and strut diameter. However, considering the pore-scale characteristics of the lattice structures, it is observed that the Octa configuration has the highest porosity value, while the Simple configuration has the lowest. This results in the highest and lowest PCM ratios of 1.07 and unity, respectively. Consequently, these differences lead to the highest and lowest time-to-steady ratios of 1.35 and unity, respectively. The results indicate that the Simple structure achieved the highest PCM transition rate and energy ratio of unity, highlighting its significant capacity for energy absorption. Conversely, the Octa structure exhibited the lowest PCM transition rate and energy ratio of 0.79 and 0.89, respectively. However, the Octa structure demonstrated the highest PCM efficacy of 87%, compared to 73% for the Simple structure, as it has the highest PCM ratio. All structures significantly improve effective thermal conductivity compared to pure PCM. Specifically, the Octet exhibits an enhancement exceeding 27 times that of pure PCM, which is attributable to its surface-to-volume ratio being more than twofold of alternative configurations.