Numerical simulation study on the flow and heat transfer characteristics of nanofluids under low pressure drop conditions

This research examined the synergistic enhancement mechanism of nanofluids and hollow single-pitch twisted tapes within heat exchange tubes through numerical simulation analysis. Thermal performance of Al₂O₃, ZnO, and CuO nanofluids under laminar flow conditions was assessed. This study focused on investigating the changes in heat transfer coefficient and friction coefficient under low Reynolds number conditions by keeping the geometric parameters of the twisted tape fixed and altering the nanofluid type, concentration, and inlet temperature. Results demonstrate raising the inlet temperature can enhance the heat exchanger's efficiency, particularly once the Reynolds number surpasses 1000, as the inlet temperature on the heat transfer coefficient. In addition, the composite enhancement structure using nanofluids significantly improves heat transfer performance. Compared with a pure water solution, the heat transfer coefficient increases substantially by 16%-31.6%. Nanofluids at high concentrations show decreased friction coefficients, however, the pressure drop is greater than with pure water with a range not exceeding 10.03%. Thus, despite heat transfer enhancement, the incurred energy efficiency loss needs to be accounted for. The novel composite enhanced heat transfer strategy proposed herein integrates nanomaterials and single-pitch twisted tape geometry. It offers theoretical support for designing optimized heat exchangers, specifically for low Reynolds number applications.