Optimum pin-fin spacing of branching radial heat sinks under natural convection for LED cooling

The performance of Light Emitting Diodes (LEDs) experiences a significant degradation at elevated temperatures due to inefficient heat dissipation. Passive heat sinks, such as fins, are an effective solution for managing the heat generated by LEDs. The design of fins is critical for ensuring high rates of heat removal as well as lower mass. This study conducts a numerical investigation of radial heat sinks with branching pin fins under natural convection. The primary objective is to obtain an optimum design of the branching pin fins. A parametric study is conducted to observe the effect of fin height (15 mm $<H<$ 30 mm), fin number ($5<n<20$), and pin-fin spacing ($2\text{mm}<L_s<10\text{mm}$) on the heat transfer performance of the heat sink arrays. A heat transfer enhancement factor based on the thermal resistance and mass of the heat sink is used to calculate the increase in the heat transfer performance of the current design over the branching plate fin radial heat sinks. Due to the branching pin fins, the mass of the heat sinks reduces by 23 %–33 % for fin heights of 15 mm and 30 mm while providing similar thermal performance as branching plate-fin heat sinks. From the current study, an optimum pin-fin spacing of 4 mm yields the lowest mass and thermal resistance among the other pin fin-spacings for fin arrays with $n>20$ and $H=21.3$ mm.