Effects of porosity and domain size on the thermal behavior of PCM melting embedded in Kelvin cell metal foam

Abstract

The low thermal conductivity of Phase Change Materials (PCMs) limits their use in thermal energy storage systems. Embedding PCMs within metal foams is an effective method to improve their thermal conductivity and energy storage capacity by creating a fast energy-absorbing zone with low thermal resistance. This study presents a pore-scale numerical analysis of the melting behavior of PCM embedded in Kelvin cell-structured aluminum foams. Three cubic domains of different sizes (small: 25.4 mm, medium: 50.8 mm, and large: 101.6 mm) were analyzed, along with four porosity levels (s = 0.875, 0.914, 0.930, and 0.956), at a constant Cell Per Length (CPL = 6). The enthalpy-porosity method was used to simulate the phase change process. Results show that lower porosity improves heat conduction and leads to faster melting. For instance, at s = 0.875, the melting time was almost 50 % shorter compared to s = 0.956. As porosity increases, the complete melting time becomes approximately 2.24 times longer. When the domain size increases from small to large, the complete melting duration increases by about 10 times. It was also observed that as domain size increases, heat transfer shifts from being conduction-dominated to convection-dominated. Lower porosity promotes a more uniform temperature distribution and faster phase change, while higher porosity increases the influence of natural convection and creates non-uniform melting fronts.