Plate Fin vs Annular Fin

Industrial Heat Exchangers www.deltathx.com Plate Fin vs Annular Fin Historically most industrial finned tube heat exchangers installed in North America were constructed using annular fins and plate fin coils were relegated to mostly commercial or light industrial applications. This was mostly driven by industry preference and manufacturing capabilities. Several years ago plate fin manufactures developed more rugged and more versatile finning capabilities and, as a result, plate fin is well suited (and sometimes better suited) in many industrial applications. Brief Description of Construction Plate Fin: Tube holes are pressed in thin sheets of metal, where tubes are inserted and then expanded. This highly efficient fin type provides a very large surface area that helps evenly distribute heat. The fins run continuously across the face and depth of the coils so every tube is bonded together with the fins and the coil bundle becomes one unit. Annular Fin: Fins are applied to the outside of each individual tube and mechanically bonded to the tube to allow for heat transfer. The finned tubes are installed in the coil allowing each tube to operate as an individual unit. There are many types of annular fins designated by the method by which the fin is attached to the tube. The more common fin types used in industrial finned tube heat exchangers are; • • • •

Tension Wound Fin ‘L’ Footed Fin Overlapped ‘L’ Fin Solder Coated Fin

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Embedded Fin Extruded Fin Root Brazed Fin Weld-on Fin

For a complete description of fin types click here For a comparison of fin types click here Replacing Annular Fin Coils with Plate Fin design Mechanical Comparison Since there is such a variety in the size, geometry and attachment type of annual finned tubes it is difficult to compare line for line against plate fin. There is enough flexibility in the materials, geometry and fin thickness of plate fin designs that they can replace annular fins in most common coil applications. Good engineering principles should be followed and attention paid to; fin root temperature, fin thickness, corrosion concerns, cleaning requirements, possibility of condensation, temperature cycling, air side pressure drop and any other concern that is considered when selecting a fin design. Thermal Comparison Plate fin designs can typically match or exceed the thermal performance and pressure drop of annual fin for a given fin count and thickness. Again, due to the flexibility in the materials, geometry and fin thickness of plate fin designs a thermal replacement plate fin design can be developed for most common coil applications. Approach For heating and cooling coil applications using fin types of; tension wound, ‘L’ footed, overlapped ‘L’ or extruded, replacement with a similar fin thickness, spacing and material in a plate fin design would typically result in similar performance to the annular fin design. Every design, however, has unique aspects so before a change in fin type is made it should be reviewed by an experienced heat transfer application engineer. In most cases, solder coated, embedded, root brazed or weld on fin are used for specific reasons (often for high temperature, strength or corrosion resistance). Consideration must be given to whether these fin types can be replaced with a plate fin design.

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