We are looking for fin tubes with secondary or extended surfaces are now universally recommended to reduce the overall size and types of heat exchangers, particularly when dealing with difficult or dissimilar fluids. When one of the fluids has low conductivity or high viscosity, which reduces the heat transfer capability, it is necessary to increase the surface offered to this fluid to compensate for its deficiency.

Secondary surface can be provided in a variety of ways, both on the outside and inside of tubes. However, the high efficiency external finned tube in the following forms.