U-Tube Bundle in Tank

U-Tube Bundle in Tank Construction

One Penetration, One Flange, One Removable Assembly

A tank bundle is a heat exchanger with no shell of its own. The bundle mounts on a flange that bolts to a tank nozzle, the heating medium circulates inside the tubes, and the tank contents surround the outside.

The U-tube geometry earns its place twice here. Both tube ends terminate at the mounting flange, so the tank needs only one penetration and one set of external connections. And the free thermal expansion means a bundle can be sitting in cold stored water when steam is admitted without any differential load reaching the flange.

Natural convection sets the size. With no forced circulation on the tank side, heat moves by convection driven only by density difference. The resulting film coefficient is low, and the bundle needs a great deal of surface to compensate. That is why catalogued tank bundles reach 120 inch lengths for duties an external exchanger would handle in a fraction of the space.

Agitation changes the arithmetic. A tank with a mixer, an agitator or a circulation loop transfers heat far better than a still one, and the required bundle gets noticeably smaller. If the tank has any of those, it is worth saying.

Removal follows the same path as installation. The bundle withdraws back through the nozzle, so clear space outside the tank at least equal to the bundle length is required. On a tank in a plant room or against a wall, that clearance frequently limits which length can be fitted.