Enhanced thermohydraulic performance in helical coil heat exchangers using synthesized Cu-doped TiO2 nanofluids: An experimental approach


Sharipova A. Shafiee M. Lotfi M. Bekturganova N.Y.
February 2026Elsevier Masson s.r.l.

International Journal of Thermal Sciences
2026#220

With increasing global energy demand, environmental concerns, and the depletion of traditional resources, enhancing the efficiency of energy-intensive systems such as heat exchangers has become imperative. This study addresses this challenge by synthesizing copper-doped TiO2 nanoparticles via a sol–gel method, aiming to simultaneously improve heat transfer rates and reduce pumping power—thereby overcoming the common issue of increased flow resistance in nanofluid applications and enhancing thermohydraulic performance in helical coil heat exchangers. Three Cu-doped TiO2 samples were prepared with doping levels of 1 %, 3 %, and 5 % Cu, and characterized using FTIR, XRD, DLS, ICP-OES, and TEM analyses, confirming successful Cu2+ incorporation and improved dispersion stability. Nanofluids based on pristine TiO2 and the Cu-doped TiO2 (5 wt% in deionized water) were tested in a horizontally oriented helical copper coil (inner diameter: 9.5 mm) across a Reynolds number range of 5,000 to 17,000. Cu doping markedly improved convective heat transfer, with TiO2–Cu5 achieving 144.8 % maximum enhancement and a Synergistic Heat Transfer Enhancement of 56.5 %. While friction rose at low flow rates, drag reduction up to 24.6 % occurred at higher Reynolds numbers. Exergy efficiency also increased, peaking at 58 % for TiO2–Cu5, which reached the highest thermal–hydraulic enhancement factor of 2.25. These results demonstrate, for the first time, that Cu-doped TiO2 nanofluids can simultaneously enhance heat transfer and flow efficiency in heat exchangers. This study presents the first correlations for Nusselt number and friction factor of TiO2 and Cu-doped TiO2 nanofluids in a helical tube, covering laminar and turbulent regimes.

Convective heat transfer , Cu-doped TiO2 nanofluids , Drag reduction , Helical coil heat exchanger , Synergistic heat transfer enhancement (SHTE)

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Department of Metallurgy and Mineral Processing, Satbayev University, Almaty, Kazakhstan
Department of Mechanical Engineering, Jundi-Shapur University of Technology, Dezful, Iran
Jundi-Shapur Research Institute, Jundi-Shapur University of Technology, Dezful, Iran
Science Department, Kazakh Automobile and Road Institute Named L. Goncharov, Almaty, Kazakhstan

Department of Metallurgy and Mineral Processing
Department of Mechanical Engineering
Jundi-Shapur Research Institute
Science Department

10 лет помогаем публиковать статьи Международный издатель

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