Hybrid Enhancement of Heat Exchanger Efficiency via Geometric Modifications and Nanofluid-Induced Thermal Property Improvement
نویسندگان
1 Department of Mechanical Engineering, Urmia University of Technology, Urmia, I.R. IRAN
2 Renewable Energy Research Center- Kirkuk, Northern Technical University, Kirkuk, IRAQ
3 Department of Mechanical Engineering, Urmia University of Technology, Urmia, I.R. IRAN
doi
10.30492/ijcce.2025.2063613.7153چکیده
This study numerically investigates the combined heat transfer and fluid flow behavior in a double-pipe heat exchanger enhanced with spring-shaped turbulators and Al₂O₃ nanofluids. Four configurations are analyzed: circular turbulators (Case A), elliptical turbulators (Case B), circular turbulators with nanofluids (Case C), and elliptical turbulators with nanofluids (Case D), all compared against a smooth-pipe baseline. A validated 3D CFD (Computational Fluid Dynamics) model implementing the realizable k-ε turbulence model (y+ ≈ 1) and second-order discretization evaluates key parameters, Nusselt number, friction factor, and thermal performance across Reynolds numbers (3,000 ≤ Re ≤ 20,000). Results demonstrate that elliptical turbulators (Case B) outperform circular designs by 12–45% in heat transfer enhancement, with peak improvements (48.7%) at Re = 3,000, attributed to stronger secondary flows. Nanofluid addition further augments performance, particularly in laminar-transitional regimes, with Case D achieving the highest thermal efficiency. However, enhancements diminish at higher Re (>13,100) as natural turbulence dominates. Pressure drops, penalties increase by up to 211.46 Pa (Case D at Re = 20,000), highlighting a critical trade-off between heat transfer and hydraulic losses. 3D thermal contours reveal that elliptical turbulators create 25–30% larger high-efficiency zones, while nanofluids reduce radial temperature gradients by 35–40%. Streamline analysis shows negligible global flow differences, confirming that improvements stem from localized near-wall effects. Exergy analysis indicates 24% higher irreversibility for Case D at low Re, emphasizing thermodynamic trade-offs. For industrial applications, Case D is recommended for low-flow systems (Re < 6,200), while simpler designs suffice at higher Re. This work provides actionable insights for optimizing heat exchanger performance through combined geometric and nanofluid enhancements, validated by rigorous numerical and experimental benchmarks.
