The heat exchanger engineer's work includes selecting equipment for numerous kinds of applications or to accommodate various conditions:
1. For new installations, the task is to select some basic equipment to provide heating or cooling. In this instance, the engineer chooses among shell-and-tube units, air coolers, double-pipe units, plate exchangers, and other designs.
2. The exchanger's size may have to be increased to accommodate a plant expansion. New units in series or parallel may be needed to meet the new conditions. Other options are:
a. Replace a shell-and-tube bundle with another having a different size tube, bare or finned, on a new spacing. This usually requires a redesign of tube-side passes.
b. Furnish new bundles using a different fin material, height, and spacing.
c. Increase the number of plates in plate exchangers.
d. Add double-pipe units in series or parallel or change their elements.
