Multi-objective engineering optimization of nanofluid coolants in compact slotted pin-fin heat exchangers

Nanofluid-cooled compact heat sinks are essential for thermal management of dense electronic and laboratory hardware operating under tight power-constrained pumping. Slotted pin-fin geometries are beneficial under limited pump capacity because they promote surface renewal and mixing while remaining compatible with laminar flow and reduced spatial requirement. The study addresses the lack of a property-consistent, experimentally anchored framework that couples slot length, effective Reynolds number, and nanofluid loading for laminar slotted pin-fin heat sinks under constant pumping power. The objective of the investigation is to establish engineering correlations and operating maps for oxide–water nanofluids in compact slotted pin-fin arrays based on a constant-power performance evaluation criterion. Experiments and CFD-anchored response-surface modelling were carried out in a closed-loop laminar rig using Al₂O₃-, SiO₂-, and CuO–water nanofluids, with slot length, effective Reynolds number, and nanoparticle volume fraction varied systematically and analyzed through a quadratic response surface fitted to Nusselt number, pressure drop, and a performance evaluation criterion. Experiments with Al₂O₃ loadings of about 0.6–0.7 vol% at Reynolds numbers near 1200–1500 and slot lengths of 9–11 mm yielded Nusselt number increases of 14–18% and pressure-drop rises of 7–9%; these quantified changes are interpreted as performance evaluation criteria up to about 1.08–1.09 relative to water. Across the design space, practical optima fell within a corridor of 0.4–0.8 vol% and intermediate slot lengths, and the associated parity plots exhibited coefficients of determination above 0.99 for Nusselt number and pressure drop, indicating that the surrogate model is statistically robust. These findings provide a quantitative basis for selecting coolant composition, flow rate, and slot geometry in laminar nanofluid-cooled slotted pin-fin heat sinks to enhance energy efficiency and thermal reliability under constant pumping-power constraints. The framework also defines a roadmap for future optimization of hybrid nanofluids, alternative interrupted-fin concepts, and long-term stability assessment of nanofluid suspensions.