Heat transfer enhancement mechanism and structural optimisation of curved elliptical protuberant fins based on field synergy principle and entropy generation minimisation method

Under the guidance of the “dual carbon” strategic goals, air-cooled heat exchangers, as key equipment for improving energy utilization efficiency and reducing carbon emissions, are of great significance to industrial energy saving and carbon reduction. To strengthen the heat transfer performance on the fin side of air-cooled heat exchangers, a novel flat fin structure with curved elliptical protrusions is proposed in this paper. A numerical simulation method is adopted to investigate the effects of the long semi-axis (3.2–4.6 mm), short semi-axis (1.0–2.0 mm) and rotation angle (30° – 80°) of elliptical protrusions on heat transfer characteristics, flow resistance, field synergy degree and entropy generation characteristics. The results indicate that curved elliptical protrusions can effectively improve the synergy between the velocity field and temperature gradient field, thin the thermal boundary layer, suppress the flow separation behind the tube, and substantially enhance the heat transfer performance, with taking the conventional plain fin as the benchmark. The contributions of structural parameters to heat transfer enhancement are ranked as short semi-axis, long semi-axis and rotation angle in descending order. The maximum enhancement ratios of the Nusselt number reach 41%, 38% and 34%, respectively. This research is of great significance for improving the heat transfer performance of air-cooled heat exchangers and promoting the implementation of energy conservation and emission reduction strategies.