The role of porosity gradient distribution on the heat transfer characteristics of copper foam/paraffin composite phase change material

In this paper, the thermophysical properties of copper foam/paraffin composite PCM during the melting process were numerically investigated by using the finite element analysis (FEA) method. Based on the unit tetrakaidecahedron model with different porosity, six copper foam/paraffin composite PCM with different gradient porosity distributions were designed, and three-dimensional direct numerical simulations were carried out for the copper foam/paraffin composite PCM models with different gradient distributions. The veracity of the analytical model and the numerical method had been validated, and a high degree of concordance had been observed. The phase field distributions and temperature changes of the PCMs with different porosity gradient distributions during the melting process and their effects on the heat storage performance were investigated. The results show that the heat transfer performance and heat storage capacity of the PCMs can be significantly improved by changing the porosity distribution. The L-shaped distribution (82.06 % on the left) could maximize the heat transfer rate of the composite PCM while maintaining a better heat storage capacity. The phase change time was reduced by 16 s and the heat storage rate was increased by 5.7 % compared with the 89.03 % uniform porosity PCM. The results of this study provide new insights into the study of heat transfer properties of pore structure-enhanced composite PCM.