The evaluation of the effective thermal conductivity of metal-foam loaded phase change materials

Abstract

Phase Change Materials (PCMs) are suitable materials to be included in Latent Thermal Energy Storage Systems (LTESS) to enhance the storage capacity per unit of volume. In order to increase their typical low thermal conductivity, PCMs are often loaded with high-porosity open-cell metal foams. Several correlations have been proposed in the literature to evaluate the effective thermal properties of the composite medium made of PCM and metal foam. However, the values of the effective thermal conductivity (keff) predicted by the different relationships can be very different from each other, with a consequent strong impact on the results of numerical simulations. In this work, a critical overview of the accuracy of the most used literature correlations for the evaluation of the effective thermal conductivity of open-cell metal-foam loaded PCMs is made: the temperature distribution obtained through a numerical model using different correlations is compared with the experimental values measured by testing different commercial paraffins loaded with copper or aluminum foams, subjected to complete melting. Since no correlation proves to yield accurate results for all the composite PCMs tested in this work, a new method for the calculation of the effective thermal conductivity of the PCM-metal foam medium is suggested.