Heating and cooling conditions effects on the kinetic of phase change of PCM embedded in metal foam

Phase change materials (PCM) are attractive candidates for energy storage. They can store large quantities of energy in small volumes at nearly constant temperatures. Despite their advantage, their thermal conductivity is very low with a high-volume change during the melting and solidification process. One way to increase their poor thermal conductivity is to embed them into open cell metallic foams. In this paper, a numerical study is conducted on the effect of the heating and cooling conditions on phase change kinetics of paraffin embedded in a metal foam. Constant heating and sinusoidal heating are similarly investigated. For the constant heat flux, a step function ranging from +1800 W/m(2) to 1800 W/m(2) is considered, while for the variable heat flux, a sinusoidal function having a similar area as step function is considered at one wall of the container to provide heating and cooling of the PCM/Metal foam composite. A new mathematical model based on the Brinkmann-Forchheimer-extended Darcy equation and the local thermal nonequilibrium model (LTNE) is proposed by applying a two-energy equation. The paraffin phase change is modeled using the enthalpy-porosity method. The numerical results are validated by comparing them with the experimental data. The results showed that at the time of melting it has reduced with sinusoidal heating. The results also showed that the heat losses on the boundary have a greater effect in a sinusoidal heat flux case than in constant heat flux case and this effect is more important on the solidification than on the melting process of the paraffin.