Abstract

Graphene-water nanofluids have emerged as a promising coolant in jet impingement applications, offering remarkable enhancements in heat transfer due to their exceptional thermal conductivity and stability. This study systematically investigates the influence of target plate material properties on the convective heat transfer performance of graphene-water nanofluid jet impingements. Experiments were performed using graphene-water nanofluids with volume fractions of 0.1%, 0.15%, and 0.2% in a free multiple-jet impingement setup. Key parameters such as Reynolds number (held constant at 5000), jet impact angle (90°), and nozzle-to-plate distance (Z/D = 3) were controlled to isolate the effect of plate material. Thermal conductivity of the nanofluids was measured using the hot wire method, showing an increase from 0.6 (base fluid) to 0.75 W m?1 K?1 at 0.2% volume fraction. Viscosity measurements indicated a slight increase with nanoparticle concentration, remaining within practical limits for flow. The study revealed that plates made from aluminum showed up to a 20% higher convective heat transfer coefficient compared to stainless steel plates under identical conditions, demonstrating the significant impact of thermal conductivity and surface properties of the target plate. A novel heat transfer correlation was developed incorporating nanoparticle concentration, Reynolds number, and plate thermal conductivity, with an R2 value of 0.96, confirming strong predictive capability. The results indicate an optimal nanoparticle volume fraction of 0.2%, beyond which no significant heat transfer improvement was observed, likely due to increased viscosity effects. This research addresses the critical knowledge gap regarding plate material selection in nanofluid jet impingement systems and provides practical guidelines for enhancing cooling efficiency in industrial thermal management. Future investigations will explore hybrid nanoparticles and advanced coating techniques to maximize heat exchanger performance. © Akadémiai Kiadó Zrt 2025.