9bbafd4a_Duct_Heaters___Wattco_com__vs__Unfinned_tubular_elements_Finned_tubular_elements
[Unfinned Tubular elements] Increase corrosion resistance High humidity environments Corrosive chemical contaminants in the air stream [Finned tubular elements] 
Include the highest wattage/cross section duct area
Duct Heaters - Wattco.com
Finned tubular elements