Longitudinal Welded Finned Tube

Longitudinal Welded Finned Tubes:
Like welded spiral fin tubes, this welded construction can be used for practically any heat transfer application. The choice of longitudinal fin tubes vs. spiral fin tubes seems to be determined primarily by geometric factors. For example, some heater constructions consist of finned tubes inserted within other tubes - longitudinal fin tubes are the obvious choice for such applications. In other cases, users prefer longitudinal fin tube installations where the tubes will be in a vertical orientation - the fin orientation facilitates fluid drainage on one side of the fin tube. Longitudinal fin construction is commonly used in shell and tube applications, such as in double tube and multi-tube heat exchangers, where longitudinal finned tubes are telescoped within the bore of a larger tube shell. Heat is transferred between the fluid flowing through the fin tube bore and the fluid flowing through the shell bore. The fluid flowing through the shell bore is forced to flow between the longitudinal fins. In this case, the spiral fins block the flow of the fluid rather than allowing it to flow between the fins.

Why Use Finned Tubes
① Improve heat transfer efficiency within the available space.
② Reduce the installation space for the required heat transfer surface.
③ Reduce equipment costs while having high operating reliability.
④ Reduce tube side pressure drop, reducing operating costs.
⑤ Improved rigidity and improved seismic performance of steel tubes.
⑥ Enhanced heat transfer, reduced flow resistance and metal consumption.

Manufacturing process: Longitudinal finned tubes are produced by resistance welding fins along the length of the tube. The fins are first formed into a U-shaped channel so that each leg of the U-shape forms a fin. The channel is cut to the appropriate length and then oriented and resistance welded in place along the length of the tube. The channels are welded in pairs, diametrically opposed, so the specified number of fins must be a multiple of four.
For a given tube or tube size, the required heat transfer surface area per unit length of tube can be obtained by specifying the appropriate fin height and number of fins. The number of fins depends on the outer diameter of the tube - larger OD tubes can accommodate more fins.