Finned Tube----Integral low fin tubes
Integral low fin tube developed as a method of increasing heat transfer performance of fluids while minimizing the size also cost of the heat exchanger. The fin tubes can improve the thermal performance of a heat exchanger without change shell size, flow arrangement or re-positioning of tube. The external surface of the tube is increased by the formation of "low fins".
The fin is produced by being rolled from the wall of the tube and is therefore integral with the tube itself. Due to fin rolling the wall thickness beneath the finned section is reduced compared with the plain ends. The bore of the fin section is slightly reduced. Most tubular materials can be finned, however hardness of the material usually determines whether the tubes suitable for finning.
Harder materials such as stainless steel, nickel alloys and titanium are usually supplied with a greater fin density (such as 28, 30 or 36 fins / inch). This lower fin profile reduces work hardening of the material and helps eliminate the possibilty of fin root cracking.
Softer materials such as carbon steel, copper and copper alloys are usually supplied with a deeper profile giving a lower fin density (such as 16 or 19 fins / inch). Plain end lengths and any intermediary unfinned sections must be specified.
Finished tubes can be U bent if required. The U bend area can be either finned or plain, to meet the required specification.
Regular used materials:
1. Carbon and low alloy steel
2. Stainless steel: TP304 / TP304L / TP316 / TP316L / TP321 and duplex
3. Copper alloys: Alloy 443 / 687 / 706 / 715 etc
4. Titanium and high nickel alloys
Tube Sizes - outside diameter: 12.7 / 15.8 / 19.05 and 25.4mm
Plain end wall thickness: >= 1.25mm
Length: up to 24,000mm
Typical surface area improvements by using integral low finned tubes are:
1. 19.05mm OD with 19 fins / inch: 270%
2. 25.4mm OD with 26 fins / inch: 330%
Depending on the fluids within the heat exchanger the thermal performance improvement can range from between 20% to in excess of 100%
Number of finned tubes required
Outside diameter of tube
Tube thickness or thickness required under root of fin
Length of finned tube
Number of fins per inch
Unfinned ends
Skipped portions and dimensions from one end
Material of tube
Keywords: Fin Tubes, Finned tube, Low fin tubes, Integral low fin tubes, U bend fin tube