Effect of filling configurations on melting heat transfer characteristic of phase change materials partially filled with metal foam

Abstract

Metal foam embedded in phase change materials (PCM) has been shown to significantly improve the storage of latent heat thermal energy. Nonetheless the presence of metal foam also reduces natural convection, energy storage and increases cost. To address this issue, we modelled the internal flow of heat transfer in a PCM, paraffin wax, filled with metal foam at the top or the bottom, with filling height ratio ξ of 0.25, 0.5 and 0.75. The liquid-solid phase transition was studied by numerical simulations. Results show that natural convection in the pure paraffin wax area is higher, and melting time is shorter, in the bottom-filled than in the top-filled configuration. These differences increase with filling height ratio. By contrast, in metal foam-paraffin composite region, melting time is longer in the bottom-filled configuration due to heat loss. Interestingly, we observed significant changes in the interface shape of liquid-solid PCM at the junction of the pure paraffin and the metal foam-paraffin composite region. The liquid fraction formulas for different metal foam filled configurations are established as the function of Fourier number, Rayleigh number and filling height ratio.