Final answer:
The typical shape of a pin fin is cylindrical, chosen for its heat dissipation efficiency and ease of manufacturing.
Step-by-step explanation:
The shape of the pin fin is typically cylindrical. Pin fins are used in heat exchange applications to increase the surface area for heat transfer. They extend outward from a surface to enhance heat dissipation to the surrounding medium, whether it be air or a liquid. The choice of a cylindrical shape for pin fins is mainly due to the efficient way it allows for heat to be conducted away from the object they are attached to, and also because it is relatively simple to manufacture. The cylindrical geometry also has a uniform cross-sectional area and exhibits cylindrical symmetry which is helpful in facilitating a uniform distribution of temperatures across the fin.