Thermal performance improvement of spherical encapsulated phase-change material by the metal fins

Spherical capsules filled with Phase-Change Material (PCM) have received significant attention in many latent- thermal-energy-storage (LTES) systems. The poor thermal conductivity limits the thermal efficiency of LTES systems obviously. To overcome this problem, spherical capsules filled with composite fins are proposed. This study built four spherical capsules, including No-Fin (no-fin spherical capsule), 1-Fin (single-fin spherical capsule), 2-Fins (2-fin spherical capsule), and 3-Fins (3-fin spherical capsule). The thermal performance of the spherical capsules with different fin numbers was numerically compared, including the temperature response rate, the full melting and solidification times, the thermal efficiency and the fin efficiency. The experimental results show adding metal fins can enhance the thermal performance of spherical encapsulated PCM and the more fin number has the higher enhancement efficiency in increasing temperature response rate, enhancing thermal release and storage capacities and improving thermal efficiency. Compared to No-Fin, the thermal storage and release capacities are increased by 27.8 % & 51.1 %, 74.6 % & 97.8 %, and 108.4 % & 151.1 % for 1Fin, 2-Fins, and 3-Fins, respectively, while their thermal efficiencies are also increased by 8.3 %, 13.2 % and 20.4 % for 1-Fin, 2-Fins, and 3-Fins. Moreover, the fin efficiency is higher by up to 25 % in the thermal discharge process than in the thermal charge process.