In addition to the type description code there is also a shorthand that is used for classifying heat exchangers. The first element of the shorthand is the nominal diameter, which is the inside diameter of the shell in inches, rounded off to the nearest integer. For kettle reboilers and chillers (remember the kettle has a narrow end and a fat end), the nominal diameter is the port diameter (the narrow end) followed by the shell diameter, each rounded off to the nearest integer.
The second element is the nominal tube length in inches. Tube length for straight tubes is taken as the actual overall length. For U-tubes the length is taken as the straight length from the end of the tube to the bend tangent.
The third element is a three-letter code indicating the type of front end, shell, and rear end, in that order. For example, a fixed tubesheet exchanger (the tubesheet does not expand and contract as it heats and cools) with removable channel and cover, single-pass shell, 23M-in, inside diameter with tubes 16 ft long is denoted as SIZE 23-192 TYPE AEL.
A pull-through, floating head, kettle-type reboiler having stationary head integral with the tubesheet, 23-in. port diameter and 37-in. inside shell diameter with tubes 16 ft long is denoted as SIZE 23/37-192 TYPE CKT.