Effects of Hybrid Nanofluids on Boosting Heat Transfer within Curved Helical Tubes: A Computational Investigation

Abstract

This study numerically investigates the thermal performance of a heat exchanger featuring a curved helical tube and hybrid nanofluids using water as the base fluid. The simulations are conducted using a Computational Fluid Dynamics (CFD) code based on the Finite Volume Method (FVM). Three working fluids—pure water, Water/Ag-MgO, and Water/Al₂O₃-CuO—are examined across a range of Reynolds numbers (Re = 500–2000), under steady, laminar, Newtonian, and three-dimensional flow conditions. Results indicate that hybrid nanofluids exhibit higher pressure drops compared to pure water across all volume fractions and Reynolds numbers. Notably, Water/Ag-MgO with higher volume fractions shows the greatest pressure drop. As volume fraction increases, differences in performance become more pronounced. The thermal efficiency for certain volume fractions of Water/Ag-MgO and Water/Al₂O₃-CuO exceeds one, indicating improved thermal performance over pure water, while lower fractions yield efficiencies below one. Therefore, the selection of an appropriate volume fraction is critical. As the Reynolds number increases up to 1000, thermal efficiency improves significantly; beyond this point, the growth rate slows. The maximum efficiency is achieved with Water/Ag-MgO at Re = 2000. © 2025 Elsevier B.V.