Experimental Investigation of Freezing and Melting Characteristics of Graphene-Based Phase Change Nanocomposite for Cold Thermal Energy Storage Applications

In the present work, the freezing and melting characteristics of water seeded with chemically functionalized graphene nanoplatelets in a vertical cylindrical capsule were experimentally studied. The volume percentage of functionalized graphene nanoplatelets varied from 0.1% to 0.5% with an interval of 0.1%. The stability of the synthesized samples was measured using zeta potential analyzer. The thermal conductivity of the nanocomposite samples was experimentally measured using the transient hot wire method. A similar to 24% (maximum) increase in the thermal conductivity was observed for the 0.5% volume percentage in the liquid state, while a similar to 53% enhancement was observed in the solid state. The freezing and melting behavior of water dispersed with graphene nanoplatelets was assessed using a cylindrical stainless steel capsule in a constant temperature bath. The bath temperatures considered for studying the freezing characteristics were -6 degrees C and -10 degrees C, while to study the melting characteristics the bath temperature was set as 31 degrees C and 36 degrees C. The freezing and melting time decreased for all the test conditions when the volume percentage of GnP increased. The freezing rate was enhanced by similar to 43% and similar to 32% for the bath temperatures of -6 degrees C and -10 degrees C, respectively, at 0.5 vol % of graphene loading. The melting rate was enhanced by similar to 42% and similar to 63% for the bath temperatures of 31 degrees C and 36 degrees C, respectively, at 0.5 vol % of graphene loading.