3.4. Selection of fins
In any application, selection of a particular fin configuration may depend on space, weight, manufacturing, and cost consideration, as well as on the extent to which the fins reduce the surface convection coefficient and increase the pressure drop associated with flow over the fins [8]. Theoretically, fins are used to increase the heat transfer from a surface by increasing the effective surface area. However, the fin itself represents a conduction resistance to heat transfer from the original surface. In addition, the
significant potential improvements in convective heat transfer can be offset by the increased amount of
energy that is stored, and subsequently removed from the mold. For these reasons, there is no assurance that the heat transfer rate will be increased through the use of fins. Fin effectiveness can be enhanced by the choice of a material of high thermal conductivity. Aluminum alloys and copper come to mind. However, although copper is superior from the standpoint of thermal conductivity, aluminum alloys are the more common choice because of additional benefits related to lower cost and weight. Fin effectiveness is also enhanced by increasing the ratio of the perimeter to the cross-sectional area. For this reason the use of thin, but closed spaced fins is preferred, with the proviso that the fin gap not be reduced to a value for which flow between the fins is severely impeded, thereby reducing the convection
coefficient [9].