Air Fin Coolers or Air cooled Heat Exchangers are Heat Exchangers to exchange the Heat between Air/Gas on one side & Air/Gas/liquid on other side.
Air/Gas have very low heat transfer co-efficient. Low Heat Transfer Co-efficient results in requirement of Large Surface Area for a conventional Shell & Tube Type of Heat Exchangers for a fixed Heat Transfer Rate. This results in a huge size of Heat Exchanger. To overcome the Huge Size requirement, area available on Air/Gas side is enhanced with help of External Fins. The basic idea is to provide a very large heat transfer area in a relatively small area.
Various Types of Fins are used depending on the Air/Gas to be cooled, Fouling Nature of the Air/Gas, Area Availability etc. Some of them are enumerated below
Plate Fin:
Plate Fin generally consist of a thin strip of either aluminium, Galvanized Iron, Copper etc which is slipped over the OD of the Tube. Necessary operation is done to ensure proper contact between the OD of the Tube and Tube Hole ID of the Plate Fin. The Pitch of the Holes in Fin is accordingly to the Tube Layout of the Tube Sheet.
Integral Fin:
The Tubes are finned on the OD of the Tube as shown in the picture. This increases the Heat Transfer Area of the Tube by 3 to 3.5 Times as compared to Plain Tube, with a minor increase in the cost. These Tubes find applications in the AC Plants/Oil Cooler, Condensers etc. Carbon Steel, Stainless Steel, Copper, Copper Alloys can be finned.
Spiral Tension Wound Tubes:
Here Plate Fin is tension wound spirally on the od of the tube, ensuring proper contact between the OD of the Tube & Plat Fin. Plate Fin material can be Aluminium, Carbon Steel, Copper, while Tube material can be Carbon Steel, Stainless Steel, Copper, Copper Alloys etc.
L Type Fins:
The aluminium strip foot section is first formed into an L shape and then tension wrapped on to the base tube. Wound fin base sections are close to each other so as ensure a continuous cover over the primary tube surface. Finally, the fin strip is fastened at ends to prevent loosening
G Type Fins:
The aluminium strip foot section is first formed into an L shape and which is tension wrapped and embedded into the primary tube wall. These type of tubes have better life vis a vis the L type of Fins find applications in Refineries.
