Hairpin heat exchangers utilize true counter-current flow which maximizes the temperature differences between the shellside and tubeside fluids, unlike the multi-pass shell-and-tube designs where correction factors are used to account for the inefficiencies resulting from co-current passes.

When your process calls for a temperature cross (when the hot fluid outlet temperature is below the cold fluid outlet temperature), a hairpin heat exchanger is the most efficient design and will result in fewer sections and less surface area.