Fin effectiveness is a better performance indicator than fin efficiency

The effectiveness is a direct measure of the heat flow through a fin, whereas the fin efficiency is an idealisation. The maximum fin effectiveness comes from the mathematical description of the problem, and is the upper bound on the effectiveness. A design chart is presented, which permits the prediction of the effectiveness in terms of a performance ratio, the fin aspect ratio and the maximum effectiveness, or the effectiveness can be calculated by appropriate mathematical expressions, Details are included on how to use the effectiveness to evaluate the heat flow from a primary surface and also the product of the overall heat transfer coefficient and transfer area for an exchanger.