Enhancing thermophysical properties of phase change material via alumina and copper nanoparticles

Summary The usage of phase change materials (PCMs) in thermal energy storage (TES) systems has been a promising approach in recent years. An accurate estimation of their thermophysical properties is a key factor in their optimal and efficient performance in TES systems. In this study, aluminum oxide (Al2O3) and copper (Cu) nanoparticles were incorporated in paraffin wax as a PCM to enhance its thermophysical properties. The effects of the nanoparticle type, mass fraction, and its size on the specific heat, density, thermal conductivity, and TES density of the nanocomposites, were investigated. A field emission scanning electron microscope (FESEM) was used to study their morphology. The experiments were based on three factors, nanoparticle type (Al2O3 and Cu), nanoparticle mass fraction (1%, 3%, and 6%), and nanoparticle size (30, 70, and 110 nm), while pure paraffin wax was applied as the control sample. The addition of nanoparticles to paraffin has been proven to be a promising technique. The results showed that the specific heat changes of the NePCMs have not been influenced by the factors under consideration. Also, higher mass fractions and smaller sizes of nanoparticles resulted in higher densities in NePCMs. Moreover, the thermal energy storage density of NePCMs increased at higher loading and smaller size of the nanoparticles. The improvement in thermal conductivity is especially significant if the smallest nanoparticle size with mass fractions of 3% and 6% is used. An improvement in thermal conductivity of up to 72% has been achieved at a mass fraction of 6% of 30 nm copper nanoparticles. Finally, the NePCM containing 6% mass fraction and 30 nm size of the nanoparticle (A6S and C6S) were selected as optimal NePCMs. NePCMs were prepared by adding Al2O3 and Cu nanoparticles to paraffin and the effects of nanoparticle type, mass fraction, and size were investigated. Specific heat and TES density were slightly higher as compared with paraffin. Not only an improvement of up to 72% in the thermal conductivity was achieved but also smaller sizes and higher mass fraction improved the thermal conductivity of NePCMs.