Influence of fin inclination on natural convection heat transfer in radial heat sinks with axisymmetric triangular fins: A combined CFD and experimental investigation

Natural convection in radial heat sinks is a fundamental paradigm for passive thermal management, yet the coupled effects of fin inclination and non-conventional geometries remain insufficiently explored. This study investigates the influence of fin inclination and fin density on the natural convection heat transfer and hydraulic performance of a radial heat sink featuring axisymmetric triangular fins. A combined conjugate computational fluid dynamic (CFD) and experimental methodology was employed, evaluating three inclination angles ( θ = 0°, 30°, 45°) across fin counts of N = 8, 16, and 24 under discrete heat inputs ranging from 92.15 to 652.80 W (1.34×10 7 ≤ Ra ≤ 2.08×10 8 ). Numerical predictions were rigorously validated against physical measurements across the operating envelope, exhibiting a maximum base-temperature deviation within ±4.6%. Findings reveal that while the vertical configuration ( θ = 0°) yields the highest axial core velocity ( u max = 2.38 m/s) and a symmetric chimney plume, it allows continuous boundary-layer growth that impedes convection dissipation. Increasing fin density from N = 8–24 substantially mitigates conductive construction resistance, expanding wetted surface area by 167% and reducing peak base temperatures by over 110° C. Inclined orientations ( θ = 30°, 45°) introduce lateral fluid entrainment and plume deflection, which actively disrupt boundary-layer development. Quantitatively, the moderate 30° inclination consistently achieved the highest average Nusselt number, yielding a 4.5 –6.8% heat transfer enhancement over the vertical baseline at elevated Rayleigh numbers while concurrently reducing the apparent Darcy friction factor across all operating conditions ( Re ≤ 925). These results demonstrate that a strategic 30° reorientation can significantly enhance heat dissipation without additional material or energy costs, offering a practical design pathway for the thermal optimization of compact electronics, LED modules, and battery systems.