purpose of a Fin

The purpose of fins is to improve heat dissipation from a surface to surroundings. Fins are widely used in engineering heat transfer
equipment's  Electrical apparatus like transformers and motors in which
the generated heat should be efficiently transferred, are provided with fins on the outside surface. Similarly fins are provided on the cylinders of air cooled LC. engines (like that of a motor cycle) and on a large variety of heat ex changer.
various types of fins:

The fins are designed and manufactured in many shapes and forms. These

are mainly of following types.

(i) Straight fin : It is an extended surface attached to a plane wall. It may be of uniform cross sectional area, or its cross sectional area may vary along its length to form a triangular, parabolic or trapezoidal shape.

(ii) Annular fin : This is a fin circumferentially attached to a cylinder and its cross section varies with radius from centre line of cylinder.

(iii)Pin Fin or spine : These fins are of circular cross section whose diameter is much smaller than its length. The pin fins may also be of uniform or non-uniform cross section.