3 Considerations in Selecting Shell-and-Tube Exchangers

Shell-and-tube exchangers are classified according to their geometry and construction. They have four main components: a bundle, a shell (with nozzles) enclosing the bundle, a stationary channel with nozzles, and the return head or its equivalent, U-tubes. Tubes are arranged within a circular area and rolled or welded into tubesheets. Shell-side baffles are positioned at intervals along the tubes to control flow, to act as tube supports, and to minimize vibration. Their function is to maximize the rate and stay within the allowable pressure drop. Meeting these conditions is not always possible in a given shell diameter, and when they cannot be met the shell diameter or tube pitch or both can be increased. Divided flow or the use of two or more units in parallel should be considered.

Many constructions are available. These and their nomenclature are given in the Standards of the Tubular Exchanger Manufacturers Association (TEMA), Figure 3-1. Shell-and-tube exchangers are classified according to construction features—principally, the stationary head, flow pattern, and rear-end closure. The latter is divided into three types: fixed tubesheet, floating tubesheet, and U-tube.