Plate-fin heat exchanger process - 5 types of fins

Fins play a crucial role in plate-fin heat exchangers, carrying out the primary function of heat transfer. These fins are typically made from type 3003 aluminum foil, with thicknesses ranging approximately from 0.15 to 0.3 millimeters, effectively providing additional surface area for the exchanger, thereby enhancing the efficiency of heat exchange. Brazing technology ensures a tight connection between the fins and the partition plates, allowing heat to be transferred efficiently through the fins to the cold carrier, that is, the medium being cooled. Since this mode of heat transfer is not direct, the fins are sometimes referred to as "secondary surfaces."

Moreover, the fins enhance the structural strength between partition plates. Despite the fragility of the material, the design allows them to withstand higher pressures, which is particularly crucial in high-pressure applications. By choosing suitable materials, thicknesses, and structural designs, the fins are capable of optimizing heat exchange performance while maintaining high strength.

Plain fin

Flat fins, due to their simple structure, indeed have relatively lower fluid flow resistance and heat transfer coefficients, which makes them very common in engineering applications, especially in systems with lower requirements on flow resistance. Due to their large surface area, they can effectively enhance the turbulence of fluid over the fin surface, thereby promoting heat transfer. At the same time, because of their high heat transfer efficiency, particularly during liquid-side heat transfer or phase-change processes (such as condensation or evaporation), flat fins can absorb or release heat more effectively.

When liquid flows, since the heat capacity of liquids is generally greater than that of gases, the application of flat fins on the liquid side can achieve efficient heat exchange. Moreover, during phase-change heat exchange processes, such as in evaporators or condensers, where phase change occurs on the surface of the fins, this process is accompanied by the absorption or release of latent heat, which can greatly enhance the heat exchange efficiency. Therefore, the use of flat fins in these situations can ensure good heat transfer performance while controlling the pressure loss of the fluid.

Offset fin

The sawtooth fin design indeed enhances heat transfer efficiency by increasing the turbulence of the fluid, thereby intensifying heat exchange. Since these short segments are arranged discontinuously, they can effectively disrupt the thermal boundary layer, which reduces thermal resistance and makes heat transfer more efficient. However, this design also leads to an increase in flow resistance, as the fluid encounters more resistance when passing through these irregular fins.

Since sawtooth fins can significantly improve heat transfer performance, they are often used in situations where very high heat exchange is required. Especially in the gas-side and oil-side heat transfer processes, high-efficiency heat exchangers can significantly improve the performance of the entire system. When designing such heat exchangers, a delicate consideration must be made between efficiency and pressure drop to ensure the overall performance of the system is optimized.

Perforated fin

Porous fins are a type of heat exchanger fins manufactured by perforating the fin material and then forming it through stamping. The small holes on the surface of these fins can effectively disrupt the thermal boundary layer, thereby increasing the turbulence of the fluid and enhancing heat transfer efficiency. The presence of these tiny holes not only helps in the uniform distribution of fluid on the fin surface, further optimizing heat transfer, but also promotes phase change processes, making heat transfer more efficient. However, the holes also lead to a reduction in the effective heat transfer area of the fins and a decrease in the overall strength of the fins.

Due to their unique characteristics, porous fins are often used as guide vanes to improve the uniformity of fluid distribution inside heat exchangers or to utilize their enhanced phase change heat transfer capabilities in phase change heat exchangers. At the same time, while ensuring high heat transfer efficiency, they can also maintain a moderate level of flow resistance, making porous fins suitable for applications like intercoolers, which require a balance between efficient heat exchange and moderate flow pressure drops. In design, a comprehensive consideration of heat transfer performance and fin strength is necessary to ensure that the heat exchanger can operate safely while achieving good heat exchange effects.

Wavy fin

Corrugated fins, with their unique stamped waveform design, enhance heat transfer performance while providing excellent self-cleaning functionality. This waveform design alters the path of fluid flow, causing constant changes in the fluid direction within the channels, which significantly promotes the formation of turbulence, increases fluid kinetic energy, and thereby effectively disrupts the thermal resistance boundary layer, improving heat transfer.

The density and height of the corrugations directly determine the intensity of heat transfer. The denser and taller the corrugations, the more opportunities there are for the formation of vortices and the higher the turbulence, which in turn increases heat transfer efficiency. Based on the information you provided, corrugated fins can compete with sawtooth fins in terms of heat transfer performance, with both being designs of highly efficient heat exchanger fins.

In addition, the structure of corrugated fins is not easily clogged by debris, and even in the event of clogs, the debris is relatively easy to remove. This feature is particularly valuable in the maintenance and cleaning of heat exchangers, as it can reduce downtime and improve equipment availability and reliability. The advantages of corrugated fins are particularly prominent in handling fluids with a high content of impurities or in dirty environments. When designing heat exchangers, opting for corrugated fins can not only achieve good heat exchange effects but can also reduce the maintenance costs of long-term operation.

Louvered fin

The design principle of louvre fins is aimed at forming fin shapes with a larger surface area for heat exchange, thereby improving heat transfer efficiency. By cutting the fins to create gaps similar to louvre blinds, it allows the fluid to generate relatively large turbulence while passing through the fins. This design increases the chances of heat exchange surface coming into contact with the fluid, thus enhancing heat transfer efficiency.

However, this louvre-like design also means that the cut areas are more prone to accumulate dust and other debris, which can clog the passages, restrict airflow excessively, thereby affecting the heat transfer capability and possibly leading to decreased equipment operation efficiency. For this reason, departments or applications that place a special emphasis on equipment cleanliness and maintainability, such as the Atlas Oilfree department, may specify not using this type of fin design.

Despite the potential risk of clogging, louvre fins have significant advantages in terms of manufacturing efficiency. In the production process, these fins can be rapidly produced through a fin rolling machine, making louvre fins particularly suitable for mass production, especially in the manufacturing of automotive industry heat exchangers. This type of heat exchanger is economical and practical in situations where a large number of standardized products are needed with specific heat transfer performance requirements. Considering heat transfer efficiency, production cost, and ease of cleaning, louvre fins present both challenges and undeniable advantages in specific applications.

In Summary

Each fin type has its uniqueness and provides optimized solutions for different industrial needs. Straight fins are widely used due to their economic reliability; sawtooth fins are suitable for spaces with limited room that require high heat transfer performance; porous fins show particular advantages in phase change heat exchange; corrugated fins hold an advantage in avoiding clogging and maintenance; while louvre fins with high manufacturing efficiency are suitable for consumer-level mass production. The design principles and functional characteristics of these five types of fins undoubtedly offer a variety of choices for creating more efficient and cost-effective heat exchange systems. Through precise design and application, they each demonstrate their unique value and importance in the field of heat exchange technology.