The influence of nanoparticle loading and surfactant on the viscosity of nanoenhanced energy storage materials

Solid-liquid phase change materials (PCMs) can be used as a transient thermal management technique due to their ability to store significant amounts of heat through the solid liquid phase change. It is common to improve the low thermal conductivity of PCMs by adding nanoparticles, however, this addition changes some of the physical properties of the material, including viscosity, possibly hindering convection currents seen in the liquid state. The dynamic viscosity of nano-enhanced materials is examined in this paper as a function of shear rate and temperature. The materials used are paraffin wax enhanced with herringbone style graphite nanofibers (HGNFs) in 0.1% and 0.5% volume fractions with and without oleic acid. The nano-enhanced materials are found to be Newtonian in nature and to decrease in viscosity as temperature increases.