The Thermal Performance of The Plate-fin Heat Sink under Natural Convection at Different Power Levels and Ambient Temperatures

The thermal performance of a flat heat sink and a plate-fin heat sink was experimentally compared under natural convection conditions at thermal powers of 16.5 W and 33 W and ambient temperatures of 30°C and 40°C. For the same heating powers, surface and junction temperatures increased as the ambient temperature rose from 30°C to 40°C, but the increase was not as much as the ambient temperature change. For the flat heat sink, the increase in junction temperature was 5°C at 16.5 W and 6.68°C at 33 W. For the plate-fin heat sink, the increase in junction temperature was 3.55°C at 16.5 W and 4.47°C at 33 W. The increase in surface temperature for the flat heat sink was 5.35°C at 16.5 W and 5.91°C at 33 W, while for the plate-fin heat sink, the surface temperature increase was 4.76°C at 16.5 W and 2.22°C at 33 W. The thermal resistance of the flat heat sink was around 4 K/W, while for the plate-fin heat sink, it ranged between 2-2.5 K/W, providing approximately twice the advantage in thermal resistance for the plate-fin model compared to the flat model. Under all conditions, the Rayleigh number (Ra) significantly decreased with the increase in ambient temperature but increased with the applied thermal power. Thus, the increase in Rayleigh number with power was more pronounced in the plate-fin model, indicating a more significant effect. In the plate-fin model, the fin efficiency slightly decreased with the increase in ambient temperature, from 0.63 to 0.62 at 16.5 W and from 0.65 to 0.64 at 33 W.