This Demonstration shows a calculation of heat transfer through a single fin (either a rectangular or a pin fin) mounted on a heat sink. Use the sliders to vary the fin length and the ambient air temperature. Select the fin material from the drop-down menu. The temperature distribution is shown on the fin surface using a color scale (red is hottest, blue is coolest), and the temperature of the fin tip is shown on the right along with the temperature legend. The thickness of the rectangular fin and the diameter of the pin fin are both 1.5 mm. The heat transfer rate through the fin is calculated and displayed above the fin, as well as the fin effectiveness—the ratio of the fin heat transfer rate to the heat transfer rate without the fin. The fin tip is assumed to be adiabatic and the air flow laminar.