Thermal energy storage has proven great potential in energy-saving and the reduction of environmental pollution. Technologies based on phase change materials (PCMs), absorbing latent heat during melting transition, and releasing such thermal energy during the solidification process are considered among the most effective strategies for energy storage [1]. However, the possible utilization of large-scale latent heat approaches relies on their appropriate integration in thermal facilities. In this sense, nano-phase change material emulsions (NPCEs) have emerged as a promising option that creates a higher heat transfer rate due to the large surface-to-volume ratio of the dispersed phase on very small scales and combines the good heat transfer properties of conventional carrier fluids with the better energy storage density of phase change materials [2, 3]. In the present study, novel NPCEs were designed and characterized as possible storage and heat transfer media for thermal applications. Aqueous- based nanoemulsions with fine droplets of commercial paraffin RT42 (with a melting temperature of ~48 ℃) were stabilized using Sodium dodecyl sulfate (SDS) as the emulsifier and the sonication method. The characterization and thermal properties of the obtained nanoemulsions with various paraffin volume fractions varying from 10 to 30% were analyzed by transmission electron microscopy (TEM), particle size analyzer, and differential scanning calorimeter (DSC). It was found that the paraffin sphere-like droplets have been well dispersed in water with effective diameters ranging from 110 nm to 132 nm. Thermal analysis by DSC indicated that the supercooling degree of the NPCEs decreased with the droplet size growth as a result of the increase in the volume fraction. The supercooling degree of 10 vol% NPCE was about 13 ℃ which decreases to 10 ℃ for 30 vol% NPCE. The rheological studies show that the liquid-like nanoemulsions transform into viscoelastic gels at a volume fraction of
