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

Abstract

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 ~102 and ~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 ~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 ~40% for bath temperature of −10°C.

The Impact of Additives on the Main Properties of Phase Change Materials

“…Viscosity influences the behavior of NEPCMs, for example, high viscosity might suppress natural convection during the melting process. The viscosity of NEPCMs increases as the mass fraction of the nanoparticles increases [45,50,60]. In studies carried out by Águila et al [50] the viscosity of NEPCM increased by 61%, compared to pure PCM.…”

“…A more practical approach to investigate the thermal properties of NEPCMs is an analysis of their phase change time, which was reported in [41,44,52,57,60]. Phase change time of NEPCMs depends mainly on their thermal conductivity and latent heat.…”

“…Nevertheless, in research carried out by Soni et al [44], the solidification time of PCM with Cu, Al, SiO 2 , and TiO 2 nanoparticles, including both convection and conduction, was shorter by 9.7%, 6.8%, 2.1%, and 5.2% respectively, compared to pure PCM. Prabakaran et al [60] reported that the solidification time of PCM/GNP composite was reduced by 39.21%, compared to pure PCM. Similar results were obtained experimentally by Choi et al [52], who concluded that the heat transfer rate during solidification increased with increasing concentration of graphite (average thickness of 5 µm), and graphene (average thickness of 7 nm) in the NEPCMs.…”

Critical Review on Internal and External Battery Thermal Management Systems for Fast Charging Applications

“…Carbonaceous NPs are abundantly available and have excellent thermophysical properties, such as a high thermal conductivity and specific surface area. [172][173][174][175] Owing to their higher aspect ratio, sp 2 hybridized carbon or graphitic structures, which have long, thin particles, can overcome the percolation threshold more rapidly than the 3D symmetric elements. Therefore, even low mass fractions of these structures are sufficient for attaining similar improvements in the thermal conductivity, particularly in a preferred direction.…”