Longitudinal Finned Tubes welded configuration can be used for practically any heat transfer application, and is particularly suited to high temperature, high pressure applications with high fin-side temperatures. 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 longitudinal fin configuration is most commonly used in shell and tube type applications such as in double-pipe and multi-pipe heat exchangers where the longitudinal finned tube is telescoped inside the bore of a larger tube shell. Heat is transferred between the fluid passing through the bore of the finned tube and the fluid passing through the bore of the shell. Fluids passing through the bore of the shell are forced between the longitudinal fins. In this case, a helical fin would block the flow of the fluid, rather than allowing the fluid to run between the fins.