Improving thermal conductivity phase change materials-A study of paraffin nanomagnetite composites

Paraffin is a common organic phase change material (PCM) that finds many applications in thermal energy storage (TES) systems. One common characteristic of organic PCMs is their low thermal conductivities. This - in turn - causes a slow thermal response when paraffin is used in high power applications. In this study, paraffin-nanomagnetite (Fe3O4) composites (PNMC) were prepared by a dispersion technique to enhance their thermal properties. Nano magnetite prepared using the cost-effective sol-gel method was mixed into paraffin at two different mass fractions: 10% and 20%. Scanning electron microscope (SEM) was used to observe the morphologies of nanomagnetite and PNMCs during different stages of the composite production process. SEM analysis results showed that nanomagnetite particles of 40-75 nm in size were homogeneously distributed in the paraffin structure. The latent heat storage capacity of PNMC, measured by differential scanning calorimetry (DSC) at 1 degrees C/min, was found to be 8% higher than paraffin alone. Thermal conductivities and diffusivities of paraffin and PNMCs were determined by the DICO method. For 10% and 20% by weight PNMCs, the thermal conductivities were increased by 48% and 60%, respectively. These results clearly indicate that the addition of Fe3O4 nanoparticles is an efficient and cost effective method to enhance the heat transfer properties of paraffin, when they are incorporated into latent heat storage systems. (C) 2015 Elsevier B.V. All rights reserved.