Numerical analysis of the effect of a central cylindrical opening on the heat transfer of radial heat sinks for different orientations

Abstract This paper presents a numerical study aimed to improve the natural convective cooling design of radial heat sinks used for light emitting diode (LED) bulbs. The improved design utilizes a central opening on the bottom that allows an additional natural cooling flow through the center of the fin array. First, the optimum fin spacing of a standard radial heat sink was determined and used as a reference geometry to compare the degree of improvement. By comparing different heat sink orientations, it was found that the opening can improve the orientation sensitivity by reducing the maximum difference in thermal resistance from 47.1% to 22.4%. At the orientations with θ  = 0°, 90°, and 180°, the thermal resistance of the radial heat sink was reduced by up to 4.3, 30.5, and 14.3 K/W, respectively. The effect of geometric parameters was investigated revealing that a larger opening diameter and height lead to a lower thermal resistance. The numerical model was further used to visualize the natural convective cooling flow through the fin array. For the acquired data set practical Nu -correlations including dimensionless parameters accounting for the height and diameter of the opening are proposed.