Choosing the Right Tube Fin heat exchanger

All air-cooled heat exchangers require fin tubes to efficiently transfer process heat to the atmosphere (air). Choosing the right fin tube is essential for optimal performance, as different types of fin tubes have different properties that can affect the performance of the heat exchanger. Let’s discuss the various types of fin tubes and their characteristics so that you can make an informed decision when selecting the right fin tube for your air-cooled heat exchanger.

Fin Tube Types

There are three main types of Fins used in air-cooled heat exchangers.

1. Wrap-On Fins (L-Fins):

Wrap-on fins (aka L-fins) are fins that are wrapped around the outside of the tube walls. This type of fin is the most economical fin tube. However, wrap-on fins are limited to operating temperatures below 130°C (266°F).

2 Embedded Fins:

Embedded fins are fins that are embedded into the surface of the tube walls. This type of fin is effective at higher temperatures than L-Fins, as the fins are mechanically attached to the tube wall. The downside of embedded fins is that they require a more complex manufacturing process, and are thus more expensive than wrapped L-fins. Embedded fins are suitable for operating temperatures up to 400°C (750°F)

3. Extruded Fins:

Extruded fins are fins that are extruded from an aluminum sleeve that completely envelopes the surface of the base tube. This type of fin tube is the most expensive option due to its construction and materials., However, extruded fins can be used in situations where embedded and wrap-on fins are not suitable – such as in corrosive environments like marine and coastal regions where sea salt can attack the base tubing metallurgy on both embedded and L-fin tube types. Extruded fin-tubes are suitable up to 300°C (572°F).

Considering Size and Geometry

When selecting the fin tube for your air-cooled heat exchanger, you will also need to consider the size and geometry of the fin tube. Typically, we use 10 fins per inch as these are commonly available.  They are easier for our customers to clean than 11 fins per inch (which would otherwise have a slight increase in performance due to overall surface area).  1” OD x 14 BWG min-wall SA-179 tubes are the most common tubes used.  Tubing pitch is typically 2.5”, but this is adjusted based on tube OD and/or to adjust the number of tubes per row.  Further, the pitch is adjusted to affect the airflow and static pressure, which impacts fan and motor selection.  

How Extruded Fin Tube Design Enhances Heat Transfer Efficiency

Superior Thermal Contact and Durability

Among various fin types, the extruded fin tube stands out for its exceptional bond between the fin and base tube. In this process, a thick aluminum sleeve is extruded and pressure-locked onto the base tube, forming a solid, continuous metal-to-metal contact. This construction enhances heat transfer by reducing thermal resistance between the fin and tube surface. According to Thermofin, extruded fins deliver up to 20% better performance compared to mechanically wrapped fins, particularly under high thermal cycling and corrosive environments.

Ideal for Air-Cooled Heat Exchangers

In finned tube heat exchanger applications where air is the cooling medium, extruded fins offer a high-performance solution with excellent resistance to vibration, fouling, and salt spray corrosion. This makes them particularly suitable for offshore platforms, petrochemical plants, and demanding HVAC systems. Although they may come at a higher manufacturing cost, their long-term reliability and thermal performance justify the investment in systems where downtime and maintenance costs are critical.

Optimizing Tube Pitch in Finned Tube Heat Exchangers

Balancing Thermal Efficiency and Airflow

In a finned tube heat exchanger, the tube pitch—the spacing between adjacent tubes- plays a pivotal role in overall system efficiency. When designing for air-side heat transfer, a tighter pitch increases fin density and surface area, boosting thermal output. However, this comes with trade-offs: reduced airflow and increased pressure drop can lead to higher fan energy consumption. A wider pitch improves airflow and cleanability but may reduce the heat transfer rate. Finding the optimal balance is key, especially in high-dust or outdoor environments.

Pitch Guidelines for Air-Cooled Systems

According to Thermal Fluids Central, the typical transverse pitch ranges from 1.25 to 2 times the tube diameter for finned tube configurations. Engineers must consider factors such as fin efficiency, face velocity, and required duty when finalizing the layout. Proper pitch selection ensures the exchanger meets thermal requirements without excessive energy penalties, making it a vital element in fin tube system design.

Select the Right Fin Tubes for Your Air Cooled Heat Exchanger With Altex

As the leading manufacturer of air-cooled heat exchangers in Canada, Altex has the expertise and the experience to help you select the right fin tube for your air-cooled heat exchanger. Our team of engineers and technicians can help you determine the optimal fin tube size and type for your specific application. With Altex, you can rest assured that your air-cooled heat exchanger will be performing at its best.

Contact us today to learn more about how we can help you find the perfect fin tubes.