Heat exchangers can be constructed from various materials to meet specific needs. Common materials include copper, copper-nickel, steel, and stainless steel for tubes, with naval brass or copper-nickel for tube sheets.
Shell Assembly: The shell, made from steel pipe or rolled plate metal, is designed for economic efficiency and durability. Ensuring shell roundness through mandrel expansion or double rolling is critical for minimizing baffle spacing and optimizing performance. Impingement plates distribute fluid evenly to prevent erosion, vibration, and cavitation.
Tubes: Heat exchangers use tubes made from materials such as low carbon steel, copper, stainless steel, and more, with diameters from 0.625 to 1.5 inches. Tubes can be seamless or welded, with fins added to improve heat transfer rates. Finned tubes are ideal for lower heat transfer coefficient shell-side fluids. U-tube designs handle significant thermal differences but are harder to clean and maintain.
Bonnets and End Channels: Bonnets regulate fluid flow in the tube-side circuit and are fabricated or cast. Mounted against the tube sheet with bolts and gaskets, they may include pass ribs for consistent fluid velocity and pressure drop. Materials used include iron, steel, bronze, Hastelloy, nickel-plated, or stainless steel.
Baffles: Baffles guide tubes during assembly, prevent vibration, and direct shell-side fluids to increase heat transfer. They fit tightly within the shell to prevent fluid bypass and are precisely manufactured for easy assembly and maintenance. In liquid applications, baffles occupy 20-30% of the shell diameter; in gas applications, 40-45%. They are evenly spaced to reduce pressure drop and ensure even fluid velocity.
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