When the shell-side fluid is a relatively low-pressure gas, heat exchangers incorporating Fin Tubes, with a significantly larger heat transfer surface area, are generally used to improve thermal efficiency.

Typical applications include the Air Cooled Heat Exchanger, which condenses steam with air instead of water and is widely used as a steam condenser in locations where cooling water is difficult to supply, such as urban waste incineration plants; the Economizer, which recovers waste heat from boiler flue gas to raise feed water temperature; the Inter & After Air Cooler, an essential component of the air compression process; and the Air Preheater, which preheats combustion air using flue gas or steam.