1. Function and Fabrication of Fins
Fins are the fundamental components of a radiator, and heat transfer is mainly achieved by fins. There are two primary forming processes for fins: stamping forming and roll forming. In production, roll forming (fin rolling machine) is generally used for fins with low fin height and large wave pitch. Stamping forming (corrugating machine) is adopted for fins with high fin height and small wave pitch. Stamping forming delivers lower productivity, while roll forming features high productivity. Common aluminum foil thicknesses include 0.12 mm, 0.15 mm, 0.17 mm, 0.2 mm and 0.3 mm. For fin dies, the fin height is adjustable as required, whereas the pitch is fixed.
2. Classification of Fins
Fins are available in various structural types such as offset strip (serrated) fin, plain fin and perforated fin. The suitable fin type can be selected according to different operating conditions. The heat exchange capacity is determined by the extended surface area of fins and their ability to disturb the fluid flow. Characteristics of plain fin: it is a long rectangular fin with smooth walls. Its heat transfer and flow characteristics are similar to those of fluid flowing in long circular tubes. See Figure 1.
Characteristics of Offset Strip (Serrated) Fin: The fluid passages are stamped into an uneven profile to increase fluid turbulence and enhance heat transfer. It is known as a high-efficiency fin. See Figure 2.
Wavy Fin: Certain corrugations are pressed on plain fins to promote fluid turbulence. The denser the corrugations and the larger the wave amplitude, the better the heat transfer performance.
Perforated Fin: It is formed by stamping numerous holes on plain fins. It is commonly used at inlet and outlet distribution sections and locations where fluid phase change occurs.
Triangular Fin: Triangular fins feature good structural rigidity. They disturb airflow to enhance heat transfer and are lightweight. Suitable for plate-fin radiators, they are easy to form and can improve heat dissipation efficiency. However, due to line contact, they impose high requirements on brazing. If the fin height exceeds tolerance, insufficient pressure resistance may easily occur.
