Solidification of Graphene-Assisted Phase Change Nanocomposites inside a Sphere for Cold Storage Applications

In this work, we experimentally investigated the solidification behavior of functionalized graphene-based phase change nanocomposites inside a sphere. The influence of graphene nanoplatelets on thermal transport and rheological characteristics of the such nanocomposites were also discussed. We adopted the covalent functionalization method to prepare highly stable phase change nanocomposites using commercially available phase change material (PCM) OM08 as the host matrix and graphene nanoplatelets (GnPs) with 0.1, 0.3, and 0.5 volume percentage as the nano inclusions. We report a maximum thermal conductivity enhancement of similar to 102 and similar to 46% with 0.5 vol% in the solid and liquid states, respectively. Rheological measurements show that the pure PCM shows Newtonian behavior, whereas the inclusion of GnPs leads to the transition to non-Newtonian behavior, especially at lower shear rates. Viscosity of the nanocomposite increases with an increase in the volume fraction of GnP. For 0.5 vol% of GnPs, maximum increase in viscosity was found to be similar to 37% at a shear rate of 1000 s(-1). Time required for complete solidification decreases with the loading of GnPs. Maximum reduction in solidification time with 0.5 vol% of GnPs was similar to 40% for bath temperature of -10 degrees C.