To analyze the parameters which influence the fin's effectiveness, we will consider the case of a very long fin. Let's define the fin effectiveness formula and then specifically define fin effectiveness for long fin.
Now from the above equation to have high effectiveness of the fin,
The thermal conductivity K of the fin material should be as high as possible. Hence fins are usually made from copper, aluminum, and iron.
The ratio of the perimeter to the cross-sectional area of the fin p/Ac should be as high as possible.
The use of a fin is most effective in applications involving a low convection heat transfer coefficient. For example, fins are put towards the side of the liquid-gas heat exchanger because usually, the heat transfer coefficient is lower on the gas side compared to the liquid side.