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Vulcan's Longitudinal Finned Tubes are
produced by resistance welding fins in the longitudinal direction along
the length of the tube. The fin strip is first formed into a U-shaped
channel, such that each leg of the U will form a fin. The channels are
cut to the appropriate length and then oriented along the length of the
tube and resistance welded in place. The channels are welded in pairs,
diametrically opposed -- therefore the number of fins specified must
always be a multiple of four.
For a given pipe or tube size, the desired
heat transfer surface area per unit length of tube can be obtained by
specifying the appropriate fin height and/or number of fins. The
maximum number of fins is dependent upon the tube outside diameter --
larger OD tube can accommodate a greater number of fins.
Some customers specify that the longitudinal
finned tubes be "cut and twisted". This operation consists of cutting
through the fin channels circumferentially at specified intervals along
the tube length. The fins are then bent (or "twisted") on one side of
each cut, creating a discontinuity that promotes turbulent fluid flow,
thereby enhancing heat transfer efficiency.
The choice of longitudinal
finned tubes versus helical finned tubes seems to be governed mainly by
geometric considerations. For example, some heater configurations
consist of finned tubes inserted inside other tubes -- longitudinal
finned tubes are the obvious choice for such applications. In other
cases, users prefer longitudinal finned tubes for installations where
the tube will be oriented in a vertical direction -- the fin orientation
facilitates fluid drainage on the fin side of the tube.
The following table shows Vulcan's
manufacturing capabilities for longitudinal finned tube ...
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Weld
Process |
Resistance
Weld |
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Tube/Pipe
Size |
0.625" to
10.75" outside diameter |
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Fin Height |
0.21" to
1.50" |
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Fin
Thickness |
0.035" to
0.050" |
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Number of
Fins |
Dependent
on tube OD |
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Materials |
Any
material combination that can be resistance welded |
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Tube
Length |
No
practical limit |
Like welded helical finned tubes, this
welded steel configuration can be used for practically any heat transfer
application, and is particularly suited to high temperature, high
pressure applications. The important features of this configuration
are efficient, effective bond of fin to tube under all conditions of
temperature and pressure, and ability to withstand high fin-side
temperatures.
See Vulcan's "Standard Specifications for Welded
Longitudinal Finned Tubes"
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