Numerical optimization on metallic foam for enhancing melting of PCM in a multi-channel thermal storage tank

Latent heat thermal storage (LHTS) systems have strategic potential for industrial waste heat recovery and utilization. However, common phase change materials (PCMs) with poor heat conduction are the bottleneck restricting the heat storage efficiency improvement of LHTS systems. Considering open-cell metal foams (MFs) have excellent conductivity, a multi-channel LHTS tank with MFs was designed to improve the heat storage efficiency of LHTS systems. A transient phase transition numerical model was developed to reveal the influence of MFs on the heat storage efficiency. The numerical predictions were in satisfactory agreement with the existing measurements. PCM-MF composites could remarkedly improve the melting rate of PCM. The complete melting time (CMT) of PCM and HTF with open-cell MF could be reduced by 77.5% compared to PCM and HTF without MF. In addition, when the equivalent porosities of MFs in PCM and heat transfer fluid (HTF) were kept constant, different porosity combinations for MFs were optimized to further reduce the CMT of PCM. The combination of 0.98–0.900 could save 10.8% of melting time compared to the combination of 0.87–0.966. Results indicated that the CMT of PCM increased by only 4.3% at most after neglecting natural convection for the combination of 0.99–0.894.