Simulations of melting performance enhancement for a PCM embedded in metal periodic structures

To overcome the inherent poor thermal conductivity of most phase change materials (PCM), inserting highly thermally conductive wire nets with periodic structures into them have been proposed. Numerical simulations have been extensively conducted to determine critical cell size and the effect of cell height and interface gap thickness on the heat transfer within the PCM. In addition, predictive correlations of the effective thermal conductivity were put forward. The simulated results indicate that: for structures with the same porosity, the critical cell size gradually decreases as the thermal conductivity of the wire net (ligament material) increases. For the proposed periodic structure embedded in the considered computational domain with 0.90 porosity, the critical pores per inch (PPI) for copper ligaments is approximately 10 PPI, while for stainless steel, it is approximately 3-5 PPI; a shorter cell height with a lower porosity shortens the melting time, therefore, stacking inexpensive metal wire is considered as an interesting alternative to commercially produced metal foams. Moreover, non-brazed scenarios lead to longer melting times, more than three times, compared to a perfectly brazed case. Furthermore, the effective thermal conductivity of the proposed periodic structure has been numerically calculated, which agrees well with some models available in the literature.