Spray cooling heat transfer enhancement using graphene nanofluids: An experimental approach

Abstract

This study experimentally investigates the thermal performance of graphene–water nanofluids for spray cooling applications under high-heat-flux conditions. Five nanoparticle volume concentrations (0.01%–0.2%) were systematically analyzed to determine the optimal formulation for enhanced heat transfer. Experiments were conducted on a square copper substrate (10 mm²) using a full-cone pressure-swirl nozzle (0.4 mm orifice diameter) at volumetric fluxes ranging from 0.83 to 2.5 cm³ cm⁻² s⁻¹. The results reveal a pronounced dependence of cooling performance on nanoparticle concentration, with a peak enhancement observed at 0.1 vol% graphene loading. At this optimal condition, the nanofluid achieved a 43% increase in average heat transfer coefficient, reaching 4.5 W cm⁻² K⁻¹, and a 66% improvement in critical heat flux (CHF), attaining 450 W cm⁻² compared with pure water. Further increases in concentration beyond 0.1 vol% led to marginal performance degradation due to nanoparticle agglomeration and partial surface fouling. The findings confirm that graphene nanofluids, owing to their superior thermal conductivity, high surface area, and colloidal stability, represent a promising class of next-generation coolants for spray-based thermal management systems in electronics, aerospace, and renewable energy applications.