We know that the heat transfer coefficients increase when fluids velocity and turbulence increase. The shellside fluid velocity can be modified by installing a set of baffles that force the fluid movement in a direction perpendicular to the axis of the tubes. By changing the separation between these baffles, it is possible to change fluid velocity.
The most common type of baffle is the segmental baffle. Segmental baffles are circular plates, about thesame diameter as the shell, to which a horizontal or vertical cut has been made. The baffles are installed into the shell in such a way that the cuts of two consecutive baffles are rotated 180 degrees. The baffles obviously must be perforated to allow the tubes to pass through them. This type of exchanger is illustrated
in Fig. 6-2. The shell fluid must follow the illustrated path to reach the outlet nozzle.