Convective Heat Transfer Characteristics and Microscopic Mechanisms of Polycarboxylate-Modified 3D Graphene Aqueous Nanofluids in Mini-Channels

To overcome graphene aggregation in aqueous nanofluids, polycarboxylate-modified structural graphene (PSG) was synthesized via surface functionalization. Characterizations indicate that the modification preserves the 3D hierarchical porous framework while ensuring exceptional dispersion stability through steric hindrance and enhanced hydrophilicity. Convective heat transfer evaluations demonstrated remarkable enhancement; notably, the 0.1 wt% PSG nanofluid achieved a 46% increase in the heat transfer coefficient over pure water at Re = 4000. Molecular dynamics simulations further revealed the underlying interfacial mechanisms. The surface-anchored oxygen-containing groups induce a dense, hydrogen-bonded hydration layer that restricts local water diffusion. This highly ordered interfacial structure may facilitate vibrational energy exchange across the solid–liquid boundary. Together with the intrinsic high-conductivity 3D skeleton, these microscopic interactions are likely to contribute to the enhanced macroscopic thermal performance, providing a promising framework for designing advanced graphene-based thermal management fluids.