L-Foot Detail

Vulcan's L-Foot Tension Wound Finned Tubes are used in applications where temperatures do not exceed about 400 degrees, primarily in air-cooled applications. Examples include large radiators, such as large compressor oil coolers, and other forced-draft or induced-draft air-cooled applications.

L-Foot tension wound finned tubes consist of thin aluminum fin strip tightly wound helically around the tube circumference. Tube material is typically carbon steel, stainless steel, or brass. A "foot", 1/16" wide, is first formed on one side of the fin strip (hence the name L-Foot). The strip is then wound tightly around the tube, with the foot bearing on the tube outer surface. A typical fin spacing is 10 fins per inch of tube length -- this can be varied. Tension in the fin strip as it is wrapped around the tube serves to seat the fin foot forcefully on the tube, and to hold the fin firmly in place.

The following table shows common L-Foot Tension Wound Finned Tube configurations:

Tube OD	5/8" to 1-1/2"
Fin Height	3/8" to 5/8"
Fin Thickness	0.014" or 0.015"
Fin Material	Aluminum 1100-0 or 5005
Tube Material	Generally carbon steel, stainless steel, or brass -- can be any material
Tube Length	No practical limit

Vulcan has the added capability of manufacturing Perforated L-Foot Finned Tube, which is identical in configuration to regular L-foot, except that holes are perforated through the fins at regularly-spaced radial intervals. Significant heat transfer advantages have been claimed for perforated L-foot finned tubes in air coolers, under the premise that interruptions in the fin surface reduce the thickness of the stagnant air film that builds up on the fin as air flows over it. This reduced film thickness results in an increased film coefficient, thereby increasing overall heat transfer rate. The improved heat transfer efficiency can reduce heat transfer surface area requirements and cooler size, or reduce air flow and fan horsepower requirements.

A common finned tube configuration used in air coolers is 5/8" OD steel tube with 7/16" aluminum fins. This configuration is frequently required on a short-delivery basis to meet cooler re-tubing requirements. Vulcan stocks a large quantity of this tube already finned and ready for immediate delivery after being cut to customer-specified length.

Vulcan can also supply accessory items commonly used in air-cooled applications, such as: wrap-on bands, wiggle strips (channel supports), turbulators, header plugs, tube plugs, and tube ferrules.

See Vulcan's "Standard Specifications for Aluminum L-Foot Finned Tubes"