On the performance of melting features in a thermal energy storage unit: Metal foam argumentation

Thermal energy storage has been attracting more and more attentions due mainly to its distinctive features on peak-load shifting capability for systems with renewable energy involved. To further improve the overall thermal efficiency for charging/discharging processes, heat transfer techniques to enhance phase change heat transfer are typically employed. This paper introduced a novel concept of partially-filling ratio of metal foam into PCM. The melting heat transfer can be expected to be further enhanced with partially filled metal foams. To this aim, an axisymmetric two-dimensional computational model was established. A series of numerical simulations were carried out to study the effect of filling ratio of metal foam on the melting performance of a TES tube. Good agreement was achieved through the comparison of temperatures obtained from simulation and experimental measurements. Based on the results, it can be concluded as follows: if the goal was to enhance heat transfer simultaneously to save material cost, the suggested filling ratio was 0.90; if saving material cost was the aim, the filling ratio can be further reduced to 0.85. The proposed novel TES unit with partially-filled metal foam outperformed other competing heat transfer technique.