Fin geometries and densities that create turbulent flow and improve performance also increase pressure drop, which is a critical requirement in most high performance applications. The optimum fin geometry and fin density combination is then a compromise of performance, pressure drop, weight, and size. A figure-of-merit comparison based on performance, pressure drop, weight, and size among common fin types is described in “Air Cooled Compact Heat Exchanger Design for Electronics Cooling.”
Aside from fin geometry, parameters such as thickness, height, pitch, and spacing can also be altered to improve performance. Typically, fin thicknesses vary from 0.004 in. (0.1 mm) to 0.012 in. (0.3 mm), heights vary from 0.035 in. (0.89 mm) to 0.6 in. (15.24 mm), and densities vary from 8 to 30 FPI (Fins Per Inch).
In most high performance applications, fins are made of copper or aluminum. Aluminum fins are preferred in aircraft electronic liquid cooling applications due to their lighter weight. Copper fins are mostly used in applications where weight is not an important factor but compatibility with other cooling loop materials is.
There are many different fin geometries used in heat transfer applications. Some of the most commonly used are louvered, lanced offset, straight, and wavy fins. (See Figure 1.)