Experimental and Numerical Investigation of the Effect of Pin Fins on the Melting Time of Phase Change Material

A key challenge in employing phase-change materials (PCMs) for energy storage is their inherently low thermal conductivity. A practical approach to addressing this issue is the incorporation of expanded surfaces or fins within the PCM to enhance its thermal conductivity. This study, both numerical and experimental, evaluates the impact of inserting pin fins into phase-change materials on the melting time and the energy storage rate. The phase change materials are located in an enclosure with dimensions of 480 mm length, 240 mm width, and 60 mm height, and cylindrical pin fins with a diameter of 10 mm in two heights of 42 and 56 mm and three numbers of 21, 35, and 49 are installed inside the phase change material enclosure. At 80°C, high-temperature water flows beneath the enclosure, initiating heat transfer that leads to PCM melting. The pin fins and the interface plate between the water and PCM are made from St37 material. The results revealed a strong alignment between the numerical simulations and the experimental data. Across all designs, experimental melting times slightly exceed numerical predictions, with a maximum difference of 6.9%. Adding pin fins within the phase change material's enclosure decreases the melting time compared to configurations without fins. The results showed that the melting time of 1 kg of the phase change material can be reduced from 21% up to 44%, and the higher the number and height of pin fins, the greater the decrease in melting time, with the explanation that the effect of increasing the number of pin fins is greater than the effect of increasing their height. The reduction in melting time in finned designs is attributed to the enhanced heat transfer. This improvement in heat transfer is due to both the increased surface area for heat exchange and the formation of flow vortices within the phase change material.