The Effect of Fin Height on Heat Exchangers

Fins are one of the core components of finned heat exchangers, and their structure and dimensions have a crucial impact on heat transfer performance. Fin height is one of the most critical geometric parameters in the design of finned tubes and heat exchangers. Changing the fin height directly affects heat transfer performance, pressure drop, manufacturing costs, and overall system efficiency.

Fin height refers to the distance from the tube surface to the fins' outer edge, typically 19-55 mm. The selection of fin height requires consideration of both the heat transfer area and airflow resistance. Higher fins increase the heat transfer area and improve heat transfer efficiency, but they also increase air flow resistance. Lower fins reduce air flow resistance, but the heat transfer area may decrease.

During design, the appropriate fin height should be selected based on specific operating conditions and requirements. For example, in refrigeration systems, the fin height of the evaporator is generally 20-30 mm, while the fin height of the condenser is 25-35 mm.

As shown in the diagram above, the temperature decreases with increasing fin height. This is because the heat transfer surface area from the radiator to the air also increases, thus lowering the radiator's temperature.

However, as the fin height continues to increase, the temperature decrease gradually slows down because heat transfer at the lower part of the fins is already complete. Further increasing the fin height will not enhance convective heat transfer.

Choosing the optimal fin height depends on the specific application; the key is to ensure a balance between improved heat transfer performance and increased pressure drop. The following are recommended fin heights for specific applications:

1. HVAC Systems

• Low pressure drop should be prioritized in HVAC systems to save energy. Increasing fin height from 8 mm to 12 mm can achieve a gain of approximately 10-20%; exceeding this will increase fan energy consumption.
• Recommended Height: 8–12 mm

2. Petrochemical Industry

• In the petrochemical and refinery sectors, G-type, L-type, or welded spiral fins are commonly used. Higher fins can improve the air-side performance of high-temperature fluids.
• Recommended Height: 12–20 mm

3. High-Temperature Boilers

• In boilers, economizers, and waste heat recovery steam generators, excessively high fins increase pressure drop and easily trap fouling.
• Recommended Height: 8–12 mm

4. Marine Heat Exchangers

• In humid and high-salt environments, corrosion is a concern; fins exceeding 16 mm have poor salt spray resistance.
• Recommended Height: 10–16 mm

Designing a finned heat exchanger is a complex and meticulous process, requiring consideration of multiple factors beyond fin height, including fin spacing, fin thickness, fin material, and other parameters. Only through scientific and rational parameter selection and optimized design can the heat exchanger achieve high efficiency, energy saving, and reliability in practical applications. TORICH offers various fin types, including G-type, L/LL/KL-type, extruded type, and welded type, providing customized solutions for customers.