Baffle Spacing. As was explained previously, an increase in the heat transfer coefficient is achieved by reducing the baffle spacing.
However, there is a lower limit for the baffle spacing, set by the TEMA Standards, of one-fifth the shell diameter and never less than 2 in (51 mm).
Spacing higher than the shell diameter is not common. If higher spacing is employed, the effect may be similar to that seen in Fig. 6-3c with poor heat transfer coefficients.