An effective thermal conductivity model for architected phase change material enhancer: theoretical and experimental investigations
Résumé
Phase Change Materials (pcm) have been widely used for thermal energy storage due to their high latent heat of fusion. However, PCMs suffer from their very low thermal conductivity which limits heat spreading around the heat source. Without proper thermal conductivity enhancement, melting would occur mainly around the heat source and heat would be conducted too slowly for the device to be efficient. It is especially true when dealing with high power densities. Metallic foams are usually used as thermal conductivity enhancer, yet recent progress in additive manufacturing have allowed architected structures to be used and optimized. We present here an analytical investigation of the Effective Thermal Conductivity (etc) of porous architected structures and emphasize is made on the effect of thermal constriction at the interface with a heat spreader in contact with the heat source. To confirm the efficiency of the model, it is compared to simulation data as well as experimental data obtained using flash laser method. Flash laser method data processing had to be modified to adapt to the porous media being characterized. For that purpose, a 1D finite difference model has been developed to solve the heat equation under flash laser conditions and derive the porous material effective properties. Using this model, architected structure were proven to have an ETC up to 75% higher than the one of foam for similar porosity in particular direction of space. The validity of the above mentioned model where proven through simulation, giving an almost perfect match and experiments detailed in this paper,which showed a maximum deviation of 11%.
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