This review investigates the possible methods of maximizing the effectiveness of the extended surfaces, i.e., fins. Different researchers worked in the direction of increasing the atmospheric contact area by providing dimples, slits, perforations, etc. The review also focuses on different shapes of fins like rectangular, tree, drop-shaped and cylindrical. The effect of addition of different accessories like desiccant coating and piezoelectric fans is analyzed.

The use of extended surfaces or fins is a widely used method for increasing the heat transfer rate from a heated surface to the surroundings. These extended surfaces are typically used when the convective heat transfer rate between the surface and surroundings is low, e.g., for natural convection with gases. Different fin geometries are used depending on the application. For example, in double tube heat exchangers, rectangular fins with constant cross-sectional area are typically placed on the external surface of the interior tube to reduce the thermal resistance of this side when the fluid is a gas with low thermal conductivity or a high viscosity liquid.

2. Literature Review
2.1 Increasing Effectiveness by Geometry Changes
2.1.1 Increasing Fin Efficiency with Morphology of Fins

Nabati and Mahmoudi (2005) studied three different morphology of pin fins, viz., rectangular, circular and drop-shaped. The drop-shaped pin fins yield better treatment.

Mechanical Engineering Journal, Desiccant, Drop-shaped, Piezoelectric fan, Increasing Effectiveness, Increasing Fin Efficiency, Morphology of Fins, Geometry.