Innovative dual-PCM approach for energy storage enhancement during thermocapillary-driven PCM melting in microgravity

The application of thermocapillary convection in enhancing heat transfer under microgravity conditions has a significant potential for thermal management in space. Transport of heat under microgravity is typically dominated by thermal diffusion. However, in environments with interfacial thermal gradients, thermocapillary convection maybe utilized to induce localized fluid flow and convective transport. The present work aims to improve the thermocapillary-driven melting of a phase change material (PCM) within a two-dimensional rectangular container under microgravity conditions. A novel dual-PCM approach is proposed and numerically investigated to maximize the energy storage capacity while minimally affecting the total melting time. The rectangular container geometry is strategically modified into trapezoidal and triangular geometries to investigate the effectiveness of the dual-PCM combining n-octadecane as the primary PCM and gallium as the secondary PCM. The study provides a detailed comparative assessment of the improvements achieved in the rate of heat transfer and overall energy storage capacity for container geometries with varying wall inclinations (0(degrees) < alpha < alpha( lim)) and aspect ratios (Gamma= 2.25, 12). The results highlight how the dual-PCM approach is capable of optimizing the heat storage capacity and melting time simultaneously. The use of triangular geometries for both PCMs is found to be optimal in enhancing the energy storage capacity with minimal impact on the total melting time. Compared to rectangular containers, the melting time reduces up to 88% and 71% for containers of aspect ratios 2.25 and 12, respectively, while the total energy storage capacity exhibits a 44% increase. Overall, the present analysis demonstrates that the proposed dual-PCM approach can bean attractive passive technique for improving the performance of thermocapillary-enhanced PCMs in microgravity environments.