Modeling the Thermal Conductivity of Pure and Mixed Heavy n-Alkanes Suitable for the Design of Phase Change Materials

Recent interest in the use of paraffin waxes is related to energy management provided by phase change materials (PCMs) where a tunable melting temperature range is used to store or release latent heat by means of the solid–liquid phase change. Thermal conductivity is an essential property for the correct design of these new materials, with applications as different as household heating and insulation, clothes for athletes and campers, or solar energy storage. As the interest in most of these heavier n-alkanes was small until recently, the available data are particularly limited. The purpose of this work was to develop a simple and accurate model to estimate the liquid thermal conductivity of heavy n-alkanes suitable for the design of efficient PCMs. Corresponding states theory was selected, based on previous improvements for equilibrium and transport properties of pure and mixed heavy n-alkanes, using a second-order perturbation model on the Pitzer acentric factor. Results for the n-alkane series show that this new model is able to predict thermal conductivities in a broad temperature and pressure range with a deviation of 3%, whereas common deviations using a linear perturbation model are close to 16%. Results for one ternary and five binary mixtures indicate that the extension to mixtures is straightforward with the best results obtained using a mixing rule previously proposed for viscosity.