Structure-controlled thermal performance of phase change material composites enhanced by discrete array and monolithic perforated copper foam

Paraffin-based phase change materials are promising for latent heat thermal energy storage, but their low thermal conductivity causes slow heat charging and, more critically, sluggish heat release during solidification. This study experimentally investigates the thermal performance of PCM composites enhanced by two copper-foam architectures with the same volumetric filling ratio: a discrete 6 × 6 CF array and a monolithic 6 × 6 perforated copper foam. The aim is to clarify how structural discontinuity and continuity affect the competition between natural convection during melting and conduction during solidification. The results show that the discrete array is more favorable during melting, completing the phase transition in 72 min because its macroscopic channels facilitate liquid PCM circulation. In contrast, the monolithic perforated copper foam exhibits superior solidification performance, reducing the complete solidification time to 68 min and achieving a time-averaged discharging power of 37.1 W, which is 4.5 times that of the Pure PCM. The monolithic structure also increases the time-averaged discharging heat flux density to 92.8 W/m 2 , 12.6% higher than that of the discrete array, while maintaining a maximum monitored temperature difference of only 1.9 °C. These improvements are achieved with only a 6.9% reduction in theoretical energy storage capacity. The findings indicate that discrete foam structures are suitable for convection-assisted charging, whereas monolithic 6 × 6 Perforated-CF is more effective for rapid and stable heat release. This work provides practical design guidance for PCM-based thermal storage units requiring high discharging power, such as solar thermal utilization, building heating, domestic hot-water supply, and industrial waste heat recovery systems.