Metal foam/PCM melting evolution analysis: Orientation and morphology effects

Abstract

Phase Change Materials (PCM) are promising materials for thermal energy storage systems. Since they present a relatively low thermal conductivity, they are often embedded in an open cell a metallic foam to enhance the overall thermal conductivity. In this paper, both experimental and numerical results on PCMs coupled with aluminum foams under different heat fluxes, porosities, number of Pores Per Inch (PPIs) and orientation are presented. The test cell is equipped with a Zincum Selenide window that allows to capture the whole temperature distribution by means of a IR camera. The melting front position in time is tracked by means of a MATLAB® algorithm based on IR camera images that are useful for a more robust tracking of melting front. Numerical simulations are performed with references to the porous media volume-averaged approach, under the assumption of local thermal non-equilibrium between the two phases. The most updated correlations for the porous media closing coefficients are taken from the literature. All the experiments are compared with numerical simulations, showing a very good agreement. After showing the effects of the different input parameters on melting front evolution, an analysis in terms of different convective heat losses to the environment and melting temperature range is presented to appreciate how these two variables affect the melting front position. Finally, total melting front evolution has been compared between experiments and simulations, showing a good agreement. This has been evaluated for different conditions, showing that a decrease in the porosity drastically reduces the melting time, while PPI has no relevant effect and small effects can be observed from orientation.