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Baffles are barriers or plates that are used to force a desirable flow path through process equipment.

A simple example of this is in cylindrical mixing vessels. In an unbaffled cylindrical tank, the rotation imparted to the liquid by a rotating impeller can lead solid body rotation in the mixing vessel. This makes the liquid swirl around with little motion to facilitate axial or radial transport of material. Swirling can also lead to vortex formation, which can cause, sometimes undesirable, aeration during mixing.

Adding appropriately sized baffles to a cylindrical tank will break the swirling flow patterns created by the impeller promoting axial and radial motion and improving mixing. Rules of thumb for sizing baffles in mixers can be found in mixing handbooks and many other references.

In flow-through reactors, baffles can be used to prevent short-circuiting of the material from inlets to outlets bypassing critical mixing zones. Baffles can divert the flow, forcing most of the material to take the “long way around” through the vessel improving the residence time distribution in the vessel.

Making processes more efficient by optimizing flow with something relatively simple like baffling can lead to reduced vessel sizes and optimum power and consumption. As with most “simple” improvements, however, extra thought may be required in complex situations where the material characteristics or the vessel configuration makes adding baffles difficult. Physical modeling experimentation and computational fluid dynamics simulations, two of our key areas of expertise at Coanda, can be effectively used to help guide baffle design and placement.