Enhancing latent heat storage devices: A thermodynamic and thermo-economic assessment into metal fins, metal foam, and expanded graphite

Enhancing the thermal storage power and reducing the storage duration are vital for latent heat storage (LHS) systems. Although various solutions exist, a comprehensive comparison based on final applications is lacking. In this study, the thermodynamic performance of a cubic finned-tube LHS device using three enhancement methods: metal fins, metal foam, and expanded graphite (EG) powder are investigated. The individual and combined effects of the three approaches are comparatively analyzed by controlling the volume fraction. Based on the existing experimental data, the melting process, heat charging power, and cumulative thermal storage capacity of the device under various enhancement schemes are obtained through numerical simulations. Additionally, the investment cost and enhancement effects of each scheme are analyzed from a thermo-economic perspective. The results indicate that among the single enhancement methods, 15 vol% EG offers the best thermal storage performance, reducing the melting duration by 73.5 % and increasing the heat charging power by 269.6 % compared with the prototype device. For the combined method, the optimal performance of the device is achieved with 27 fins and 10 vol% EG, enhancing the heat charging power by 325 % and reducing melting time by 76.6 %. In contrast, replacing fins with metal foam in the central area decreases enhancement effects, regardless of the combination. Moreover, thermo-economic analysis reveals that the device with 15 vol% expanded graphite achieves the highest specific energy, reaching 68.9 Wh/kg. With the adoption of EG, each dollar invested yields a 10.61 % power increase, whereas metal foam is the least cost-effective enhancement method. These findings may provide guidelines for the enhanced design of LHS devices.