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.
This work aimed to study the recovery of three types of waste by the process of pyrolysis: biomass, plastics and used tyres. The effects of experimental conditions in products yield and composition were studied. The increase of reaction time increased alkane content both in gas phase from 53% to 70% v/v and in liquid fraction from 48% to 60% w/w. The rise of reaction temperature led to a decrease of liquid yield (from 82% to 73% w/w), which was followed by the increase of solids and gases. The increase of reaction temperature also allowed the increase of the alkane content in gas phase from 39% to 70% v/v. The increase of initial pressure did not lead to appreciable variations in product yields or composition. The parameter that most affected products yield and composition was plastics content on the wastes initial mixture. The enhancement of this parameter increased liquids yield from 33% to 92% w/w, at the expenses of solids and gases contents and also decreased aromatics contents from 52% to 28% w/w.
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