Synthesis, stability, and heat transfer behavior of water and graphene nanoplatelet-based nanofluid for cool thermal storage applications

Abstract

This study aims to synthesize stable nano-enhanced phase change materials (NEPCM) using deionized (DI) water and graphene nanoplatelets (GNPs) with the aid of three different surfactants (CTAB, SDBS, and GA). The study also investigates the dynamic behavior of the NEPCM during solidification and melting in a spherical encapsulation. GA-GNP dispersion showed prolonged stability based on zeta potential distribution (ZP) and UV–vis absorbance after 60 days of preparation. The effect of GNP concentration (0.25, 0.50, 0.75, and 1.00 wt%) on the heat transfer properties of the NEPCM was investigated using differential scanning calorimetry (DSC), temperature-time (T-t) profiles, and TC measurements. The maximum energy storage density decreased by 8.56 % and 15.3 % for 1.00 wt% GNPs added to DI-water during melting and crystallization, respectively, at a heating rate of 5 K/min. The thermal conductivity (TC) increased by 59.1 % and 10.8 % in the solid and fluid circumstances, correspondingly. Transient temperature results showed that GA significantly reduced super cooling (SC) by 47.6 % and eliminated it completely at a concentration of 1.00 wt% GNP-NEPCM. The maximum reduction in solidification rate was 26.4 % with 1.00 wt% GNP-NEPCM at a −7 °C constant heat transfer fluid (HTF) temperature. The melting duration was reduced by 33 % by adding 0.50 wt% GNPs, while the melting duration was prolonged at a concentration of 1.00 wt% due to the viscosity augmentation of molten layers. In conclusion, the proposed stable NEPCM formulation has great potential for use as an energy-efficient storage medium in the CTES system.