TEMA U-Tube Heat Exchanger Types

TEMA assigns a letter to each of the three components. Front heads run A through D, shells E through X, rear heads L through W. A U-tube bundle is rear head type U, so every U-tube designation ends in that letter. Reading the code backward tells you what you are looking at: the U says removable bundle and free thermal expansion, the middle letter says how the shell-side fluid travels, and the first letter says how much access you have to the tube side.

• BEU. Bonnet front head, single-pass E shell, U-tube rear. The cheapest removable-bundle exchanger there is, and the most common U-tube arrangement built.
• AEU. Channel with a removable cover instead of a bonnet. You can open the tube side without breaking the process piping, which is what the premium buys.

• BKU. Kettle shell with an enlarged vapor space. Reboiler and vaporizer duty, where the U-bundle sits below a liquid level and the vapor disengages above it.
• DEU. Special high-pressure front head closure for tube-side pressures beyond what bolted A and B heads hold comfortably. Feedwater heaters are the classic case.

• BFU and AFU. F shell with a longitudinal baffle, giving two shell passes and restoring counterflow when a temperature cross would otherwise defeat the design.
• BJU. Divided-flow J shell, used where shell-side pressure drop is the binding constraint rather than surface area.