Three types are prevalent shell and tube, plate-frame heat exchangers, and plate-coil.
Shell and tube types are made in numerous materials and configurations to meet the needs of the process. They are somewhat limited to about a 10°F approach temperature (small temperature difference).
Plate-frame heat exchangers are more flexible, smaller, and can easily achieve approach temperatures of 5F, and, by adding plates and some cost, can go as low as 2F. They are also made using various plate and gasket materials to meet the process needs.
Plate-coil exchangers are primarily used for vessel jacketing, tank wall, and in-tank applications. This category also includes steam-to-water.