Orientation effect of a radial heat sink with a chimney for LED downlights

The orientation effect of a radial heat sink with a chimney was investigated in an attempt to design safer cooling systems for LED downlights. The natural convective and radiative heat transfer were simulated with a numerical model to analyze the heat transfer and flow around the cooling system, and the model was experimentally validated. The causes of the orientation effect were determined by analyzing the numerical results. The influence of the geometric parameters of the cooling system on the orientation effect was analyzed. A parametric study was conducted to select the three geometric parameters that have the largest influence on the orientation effect. The numerical analysis was carried out on the design points, which were selected according to the design of experiments. A correlation was obtained that can predict the orientation effect factor depending on the geometric factors and installation angle of the cooling system.