What kind of tube does a heat exchanger typically have?

Heat exchangers most commonly employ simple, cylindrical “plain” tubes arranged in bundles within a shell, though enhanced-surface tubes (e.g., finned) are also used when higher heat-transfer rates are required. These tubes are typically made from corrosion- and temperature-resistant metals—such as copper, carbon steel, stainless steels (304/316L), copper–nickel alloys, titanium, nickel alloys (Inconel, Hastelloy) or zirconium—selected based on the fluids, pressures and temperatures involved. Bundles may consist of straight tubes fixed into tube sheets or U-shaped tubes to allow for thermal expansion, and are offered in diameters from roughly 0.625″ to 1.5″ (16–38 mm) with wall thicknesses per industry standards.

Tube Constructions

Plain (Smooth) Tubes

• Description: Cylindrical tubes with smooth internal and external surfaces, providing baseline heat-transfer performance and simplest manufacture.

• Usage: Standard in shell-and-tube exchangers for many liquid–liquid or gas–liquid applications.

Finned (Enhanced) Tubes

• Description: Tubes fitted with axial or helical fins on the outside (or internally), greatly increasing surface area and turbulence to boost heat transfer.

• Usage: Common in air-cooled exchangers or when one side has a low convective coefficient.

Materials Selection

• Carbon Steel & Admiralty Brass: Economical, moderate performance; used in water and low-pressure services.

• Copper & Copper-Nickel Alloys: Excellent thermal conductivity and corrosion resistance in seawater or potable water.

• Stainless Steels (304/316L, Duplex): Good corrosion resistance for chemical and food-grade services.

• Nickel Alloys (Inconel, Hastelloy): High-temperature and highly corrosive environments (e.g., acid, chloride).

• Titanium & Zirconium: Superior resistance to chloride stress cracking and very corrosive media like seawater or acids.

Bundle Configurations

Fixed-Tube Sheet

Tubes are welded or expanded into fixed tube sheets; simple, economical, but limited in accommodating thermal expansion.

U-Tube

Continuous “U” bends allow for differential expansion between shell and tube; easier to handle thermal stresses but harder to clean inside the bend.

Floating-Head

One tube-sheet is free to float, permitting full bundle withdrawal and inspection; ideal for services requiring frequent cleaning.