Thermal Energy Discharging Performance of Metal Foam/Paraffin Composite Phase Change Material at Pore Scale

In this research, thermal energy discharging performance of metal foam/paraffin composite phase change material (MFPC) is investigated at pore scale through direct simulation. A thermal transport model is first developed for heat discharging of MFPC by incorporating the involved effects of solidification phase transition, foam structure, and paraffin volume shrinkage. With this model, the detailed phase interface evolutions, temperature fields, and heat flux distributions of MFPC are numerically obtained and analyzed. It is found that once phase change heat discharging of MFPC begins, the solidification front of paraffin quickly forms and extends along the foam skeleton, which results in remarkably extended thermal transport interface to release latent heat as well as improved spatial synergy in phase change. The effect of local thermal nonequilibrium between porous metal foam and paraffin proves to be intrinsic and significant, providing an efficient inner driving force for enhancing latent heat discharging within MFPC. The overall energy discharging performance of MFPC unit is remarkably improved as compared with pure paraffin unit, evidenced by a large enhancement in latent heat release rate (more than three times) with only small reduction (2.6%) in heat capacity. Simultaneously, it is found that the paraffin-air interface for MFPC unit descends much faster than that for pure paraffin unit due to accelerated volume shrinkage of solidified paraffin within metal foam, resulting in a threefold enhancement in thermally driven dynamic response rate. This study can help more deeply understanding the energy discharging performance of MFPC and providing fundamental guidance for its application in miniaturized thermal systems.