Experimental and numerical analysis of hydrothermal behavior for different nanofluids in a shallowly dimpled tube heat exchanger

Heat exchangers require improved thermal efficiency for power generation, chemical processing, and electronics cooling applications. While dimpled surfaces and nanofluids have been studied separately, their combined implementation and synergistic mechanisms remain poorly understood. This study experimentally and numerically investigates aluminum oxide, copper oxide, and titanium dioxide nanofluids at 0.5%–2.0% concentrations in shallowly dimpled copper tubes. Hemispherical dimples with depth‐to‐diameter ratios of 0.1–0.3, diameters of 4–8 mm, and pitch‐to‐diameter ratios of 0.8–1.6 were tested across Reynolds numbers of 4000–20,000. Copper oxide nanofluid at 1.5% concentration in optimally configured dimpled tubes achieved 85.3% heat transfer enhancement compared to water in smooth tubes, with a thermal performance factor of 1.83. This substantially exceeded individual contributions of 34% for nanofluids alone and 38% for dimpled tubes alone, confirming strong synergistic effects. Flow visualization revealed dimple‐generated vortices intensify nanoparticle microscale transport through simultaneous boundary layer disruption and enhanced thermal conductivity. Optimal configurations maintained 52% pressure penalties while nearly doubling heat transfer rates. Empirical correlations from 180 data points predicted performance within 7% accuracy. This research quantifies synergistic effects between geometric enhancement and nanofluid technology, provides validated design correlations, and elucidates underlying mechanisms, enabling next‐generation compact heat exchangers for energy‐intensive applications.