Thermal Performance Enhancement of a Corrugated Heat Exchanger Using Al₂O₃–Water Nanofluid: A CFD Study

Abstract

This research deals with a numerical study of turbulent convective flow of a nanofluid (Al₂O₃-water) circulating in a counter-current bi-tubular heat exchanger. The studied exchanger is characterised by a new design of the corrugated inner tube in elliptical shape, intended to optimize heat exchange. The aim of this research is to predict the influence of the thermophysical properties of the nanofluid and the geometric form of the inner tube on the exchanger's thermal performance. For this purpose, bidimensional numerical simulation was carried out using CFD code, with the implementation of the k-ε turbulence model. The regime examined corresponds to a range of Reynolds numbers varying between 5000 and 11000. The validity of the numerical results was verified by comparison with experimental data published by Sarmad. The obtained results reveal a significant improvement in Nusselt numbers at high nanoparticle concentrations. More specifically, the corrugated heat exchanger is more efficient than the conventional smooth-tube model, with a 33.6% increase in the Nusselt number. In addition, the adoption of geometry with a corrugated inner tube contributes to a significant improvement in the overall heat transfer coefficient, reaching values between 682.6 and 1148 W/(m²·K) for a volume fraction of 4% in Al₂O₃.