The designs differ in the following ways, among others:
- The tube-side fluid may be constrained to pass through the shell once only, or two or more times.
- When there are many passes, the tube-side fluid may be turned around by the hairpin like nature of the tubes; or it may enter headers, at either end of the shell, that receive fluid from one set of tubes and deliver it to another set.
- The tubes entering the headers may be famed to the tube plates that separate their contents from the shell in various ways-for example, by welding.
- The headers themselves may be welded to the shell, or they may be permitted to slide relative to it in response to thermal expansion.
- The shell may be provided with removable openings to permit inspection and/or cleaning of either the inside or outside of the tubes.
- The baffles may be of various shapes, and they may be few or many in number.
- The shell-side fluid may enter or leave through one or more apertures.