Laboratory Reactor: The baffle in the laboratory reactor works under the action of the impeller's stirring.

In addition to baffles, accessories within the equipment—such as coils and draft tubes—also play a role in baffle-like functions to some extent. In industrial production, the installation of reactor baffles should be as close as possible to the fully baffled condition. At a given rotational speed, if additional accessories are added while the shaft power remains constant, this is referred to as... “Full baffle” operating condition. Typically, four baffles—each with a width equal to the vessel diameter—are sufficient to meet this requirement. So, what exactly do these baffles do? Let’s take a look. Laboratory Reactor What role does the baffle play when the impeller is stirring?

I. Two Types of Flow Patterns: When the impeller is driven by an external source and begins to rotate on its own, mechanical energy is first transferred to a small area of fluid nearby, causing intense turbulence throughout the reactor vessel. As turbulent vortices propagate outward, a high-speed jet starts to push the slower-moving liquid around it, setting up large-scale circulating flows within the vessel along specific pathways and thus forming the flow pattern of the concentrated material inside the mixing tank. Different types of impellers can generate distinct flow patterns, which are broadly categorized into axial-flow patterns and radial-flow patterns. An axial-flow impeller allows the liquid to enter and exit axially; a radial-flow impeller enables the liquid to enter axially and exit radially. Generally, axial flow primarily creates a circulation effect involving the liquid’s up-and-down reversal, whereas radial flow mainly induces a shear effect on the liquid. Reactor vessels typically employ axial-flow impellers, such as propeller-type or inclined-blade impellers; radial-flow impellers include turbine blades and flat-blade impellers, among others.

II. Laboratory Reactor The baffle and its function: When the impeller stirs a low-viscosity liquid, the high-speed rotation of the impeller generates tangential flow under the action of centrifugal force, causing the liquid to be thrown against the vessel wall and rise along the perimeter of the reactor, while the liquid level in the center naturally drops, thereby creating a large cavity within the reactor. This phenomenon is called... “Vortex.” The liquid being stirred rotates closely along with the stirring shaft, resulting in poor mixing. If the stirring involves a multiphase system, phase separation or layering may occur. In such cases, the liquid with higher dryness can draw large amounts of air from the surface of the liquid layer, reducing the apparent density of the liquid and causing the stirring bearings to experience varying forces that lead to movement. Therefore, “vortex formation” should generally be avoided. One effective approach is to install baffles around the vessel wall—typically four in number—to redirect the tangential flow of the fluid into axial or radial flow.

The propeller behind the baffle is installed on... Laboratory Reactor Inside the vessel, the spiral vortex flow in the liquid’s longitudinal cross-section is blocked by baffles, causing upward and downward deflections in a direction perpendicular to the liquid surface. At this point, the liquid is forced to undergo axial flow toward the axis, and the cavity disappears. As shown above, the flow pattern induced by the agitator inside the reactor is closely related to the mixing efficiency and the system’s heat and mass transfer performance. The agitator-induced flow pattern is not only determined by the agitator’s own characteristics but is also influenced by the internal attachments within the reactor and their installation positions. The above discussion pertains to... Laboratory Reactor The role of baffles in impeller agitation—I hope this will be helpful to everyone.